Hindawi Publishing CorporationISRN BiochemistryVolume 2013 Article ID 238428 18 pageshttpdxdoiorg1011552013238428

Review ArticleNanoparticles for Brain Drug Delivery

Massimo Masserini

Department of Health Sciences University of Milano-Bicocca Via Cadore 48 20900 Monza Italy

Correspondence should be addressed to Massimo Masserini massimomasseriniunimibit

Received 20 March 2013 Accepted 11 April 2013

Academic Editors H Itoh H Pant and M Seno

Copyright copy 2013 Massimo Masserini This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

The central nervous system one of the most delicate microenvironments of the body is protected by the blood-brain barrier (BBB)regulating its homeostasis BBB is a highly complex structure that tightly regulates the movement of ions of a limited number ofsmall molecules and of an even more restricted number of macromolecules from the blood to the brain protecting it from injuriesand diseases However the BBB also significantly precludes the delivery of drugs to the brain thus preventing the therapy of anumber of neurological disorders As a consequence several strategies are currently being sought after to enhance the deliveryof drugs across the BBB Within this review the recently born strategy of brain drug delivery based on the use of nanoparticlesmultifunctional drug delivery systems with size in the order of one-billionth of meters is describedThe review also includes a briefdescription of the structural and physiological features of the barrier and of the most utilized nanoparticles for medical use Finallythe potential neurotoxicity of nanoparticles is discussed and future technological approaches are described The strong efforts toallow the translation from preclinical to concrete clinical applications are worth the economic investments

1 Introduction

At the beginning of the third millennium due to prolongedageing neurological disorders are growing with a conse-quent high social impact due to their prevalence andor highmorbidity and mortality For the purpose of calculation ofestimates of the global burden of disease the neurological dis-orders are included in two categories neurological disorderswithin the neuropsychiatric category and neurological dis-orders from other categories Neurological disorders withinthe neuropsychiatric category include epilepsy Alzheimerand other dementias Parkinsonrsquos disease multiple sclerosisand migraine Neurological disorders from other categoriesinclude diseases and injuries which have neurological sequelssuch as cerebrovascular disease neuroinfections and neuro-logical injuries

Neurological disorders are an important cause of mor-tality and constitute 12 of total deaths globally Amongthe neurological disorders Alzheimer and other dementiasare estimated to constitute 284 of the total deaths whilecerebrovascular disease constitute about 8 of the totaldeaths in high income countries in 2005 [1]

Presently there are no effective therapies for many ofthem Scientific and technological researchesfrommolecular

to behavioral levels have been carried out in many directionsbut they have not yet been developed in a truly interdis-ciplinary way and a definitive response is still far to beprospected

The immediate consequence of such condition is thatseveral pathological disorders involvingCNS remain untreat-able Examples of diseases include neurodegeneration (egamyotrophic lateral sclerosis Alzheimerrsquos Parkinsonrsquos Hunt-ington disease and Prion Disease) genetic deficiencies (eglysosomal storage diseases leukodystrophy) and severaltypes of brain cancer Even if candidate drugs for therapy ofsuch diseases may be already available in line of principlethey cannot be currently utilized because of their insignificantaccess to the central nervous system (CNS) due to thepresence of the blood-brain barrier (BBB) [2] preventing thepassage from blood to the brain

2 The Blood Brain Barrier and Drugs

The BBB is a structure formed by a complex system ofendothelial cells astroglia pericytes and perivascular mastcells [3] preventing the passage of most circulating cells andmolecules [4 5]The tightness of the BBB is attributedmainly

2 ISRN Biochemistry

to the vascular layer of brain capillary endothelial cells whichare interconnected side-by-side by tight and adherens junc-tions Tight junctions perform two functions (i) they preventthe passage of small molecules and ions through the spacebetween cells so that their passagemust occur by entering thecells (by diffusion or active transport) This pathway controlsthe type and amount of substances that are allowed to pass (ii)they prevent the movement of integral membrane proteinsbetween the apical and basolateral membranes of the cell sothat each of the cell membrane surfaces preserves its peculiarfunctions for example receptor-mediated endocytosis atthe apical surface and exocytosis at the basolateral surfaceThree integral proteins are present at the tight junctionsoccludin claudins and junctional adhesion molecules Theformer two constitute the backbone of junction strands whilejunctional adhesionmolecules are important for trafficking ofT-lymphocytes neutrophils and dendritic cells from the vas-cular compartment to the brain during immune surveillanceand inflammatory responses Adherens junctions providestrong mechanical attachments between adjacent cells andare built from cadherins and catenins The compact networkof interconnections is conferring to the endothelial layer ofthe BBB a transelectrical resistance gt1500Ω cm2 which isthe highest among all other endothelial districts The com-pactness of the endothelial BBB layer precludes the passageacross intercellular junctions (paracellular passage) limitingthe possibility of exchanges between the two compartmentsvirtually through passages transiting across the cellular body(transcellular passage)

However the BBB is not only a mechanical fence butalso a dynamic biological entity in which active metabolismand carrier-mediated transports occur Nutrients includingglucose amino acids and ketone bodies enter the brain viaspecific transporters whereas receptor-mediated endocyto-sis mediates the uptake of larger molecules such as neu-rotrophins and cytokines [6ndash10] The BBB prevents the brainuptake of most pharmaceuticals with the exception of smallhydrophilic compounds with a mass lower than 150Da andhighly hydrophobic compounds with amass lower than 400ndash600Da that can cross the membrane by passive diffusion [9]The list of BBB-permeant drugs includes opiates (eg mor-phine methadone and meperidine) anxiolytics (diazepamtemazepam) SSRIs (paroxetine) and antipsychotics (chlor-promazine promethazine) but does not include the majorityof antibiotics and antitumorals

As above said the tightness of the BBB is preventingthe pharmacological therapy of a number of neurologicaldiseases It should also be mentioned that a further obstaclefor drugs crossing the cerebral capillary endothelium andentering the brain parenchyma is represented by the pres-ence of the P-glycoprotein pump in the BBB allowing therecognition of molecules necessary for the brain to enter thebrain and the expulsion of other molecules pharmaceuticalsincluded

Given such premises it is conceivable that different ap-proaches have been tried to allow pharmaceuticals to over-come the BBB These explorative strategies have been ran-ging from invasive techniques for example through osmotic

opening of the BBB [11] to chemical modifications of drugsin order to take advantage of physiological carrier-mediatedtransports or exploiting the so-called ldquoTrojan horserdquo technol-ogy coupling BBB-impermeant pharmaceutical to moleculesable to cross the barrier taking advantage of receptor-mediated transport systems [12]

Alternative routes of administration able to reach thebrain bypassing the BBB (eg intranasal) have been activelyinvestigated but in the line of principle they are facingthe constraints of the limited surface of adsorption of theolfactory bulb which isminimal compared to that of the BBBthus quantitatively reducing the possibility to reach the brainwith relevant amounts of drugs [13]

3 Nanotechnology for Brain Drug Delivery

In the recent years with the advent of nanomedicine engi-neered tunable devices with the size in the order of billionthofmeters have been proposed as an intriguing tool potentiallyable to solve the unmet problem of enhancing drug transportacross the BBB [14 15] Among different devices nanoparti-cles (NPs) technology is rapidly advancing NPs are objectssized between 1 and 100 nm [16] that work as a whole unit interms of transport and properties

The types of NPs that are more popular for biomedicalapplications are reported in Figure 1

The reasons for this expectation are most of all linked tothe possibility of NPsmultifunctionalization coupled to theirability to carry drug payloads included BBB-impermeantdrugs In particular the rationale of using NPs for brain drugdelivery is that proper surface multifunctionalization maypromote at the same time either their targeting of the BBBor the enhancement of its crossing The possibility for BBB-impermeant drugs to reach the brain when vehicled by NPsis based upon the fact that their crossing of the barrier willdepend completely on the physicochemical and biomimeticfeatures of the NPs vehicle and will not depend anymore onthe chemical structure of the drug which is hindered insidethe NPs

What makes NPs even more attractive for medical appli-cations is the possibility of conferring on them featuressuch as high chemical and biological stability feasibility ofincorporating both hydrophilic and hydrophobic pharma-ceuticals and the ability to be administered by a varietyof routes (including oral inhalational and parenteral) [17]Moreover NPs can be functionalized by covalent conjugationto various ligands (such as antibodies proteins or aptamers)to target specific tissues The large surface-area-to-volumeratio of NPs permits multiple copies of a ligand to be attachedand to dramatically increase their binding affinity via themultivalent functionalization [18]

When designing NPs for clinical applications it shouldbe remembered that their systemic administration generatesimportant modifications In particular the nonspecific inter-action between the shell of NPs and many classes of proteinscirculating in the bloodstream leads to the adsorption ofopsonins on their surface forming the so-called ldquocoronardquo

ISRN Biochemistry 3

Liposomes Solid lipid nanoparticle Non-polymeric micelles

Lipoplex

+

+ +

+

+

+

+

++

+

+

+

Dendrimers Polymeric nanoparticle

Polymeric micelle Nanotubes Silica nanoparticle

Quantum dots Gold nanoparticle Magnetic nanoparticle

Figure 1 Different types of nanoparticles (NPs) Graphical representation of the most commonly used NPs for biomedical applications NPsare typically by a size measuring not more than 100 nm and have significant potential for delivering drugs across the blood-brain barrier Thesize of quantum dots is usually less than 10 nm

These proteins substantially change the bare material proper-ties determining the removal of NPs from circulation by thereticuloendothelial systemmainly located in spleen and liverThe most common approaches used for escaping RES are toformulate the particles with neutral surface charge to coat

their surface with different hydrophilic surfactants such aspolysorbates and polyethylene glycol (PEG) and to use smallsize nanoparticles (eglt80 nm) [19] NPswith these featurescalled ldquostealthrdquo are able to avoid the reticuloendothelialsystem to display long circulation time and stability in blood

4 ISRN Biochemistry

and may be functionalized to successfully target and crossthe BBB [20] Finally NPs should be nontoxic either forcells in the bloodstream or for healthy bystanding cells andshould be biodegradable and biocompatible noninflamma-tory and nonimmunogenic [21] The possibilities of func-tionalization of MP for brain drug delivery are depicted inFigure 2

It is also important to point out that the tailoring ofNPs toenhance drug delivery to the brain does not necessarily implytheir ability to cross the BBB themselves It is predictable thatNPs could play this role at least in two ways

(i) by increasing the drug concentration inside or atthe luminal surface of BBB cells establishing a localhigh concentration gradient between blood an brainhigher than that obtainable after systemic administra-tion of the free drug The gradient should then favorthe enhanced passive diffusion of the drug As forexample this task could be realized by synthesizingNPs functionalized to target brain capillary endothe-lial cells This feature can be followed or not by theirsubsequent uptake from targeted cells [22]

(ii) by moving themselves into the CNS together withtheir drug cargo As for example this task can berealized enabling NPs targeting of brain capillaryendothelial cells and their subsequent transcellularpassage across the BBB [23]

For the completeness of this review in the next section themain features ofNPs commonly utilized formedical purposesand already utilized or promising candidates for brain drugdelivery will be described

4 Nanoparticles for Medical Applications

41 Lipid-Based Nanoparticles

411 Liposomes Liposomes are the first generation ofnanoparticulate drug delivery systems [24] and are consti-tuted by one or more vesicular bilayers (lamellae) composedof amphiphilic lipids delimiting an internal aqueous com-partment Usually the liposomal lipid bilayer is composedof biocompatible and biodegradable lipids present in bio-logical membranes Common liposome constituents are sph-ingomyelin phosphatidylcholine and glycerophospholipidsCholesterol an important component of cell membranesis frequently included in liposome formulations because itdecreases the bilayer permeability and increases the stabilityof the liposome in vivo Liposomes are classified on thebase of their size and the number of lamellae as follows (i)small unilamellar vesicles (SUV) with a size up to 100 nmand one bilayer (ii) large unilamellar vesicles (LUV) with asize gt100 nm and one bilayer and (iii) multilamellar vesicles(MLV) that can reach a size of several 120583m and made of manyconcentric lipid bilayers

Liposomes have been largely utilized for brain drugdelivery (for a review see [25]) for the treatment of cerebral

+ +++

++

Targetingantibody

Fluorescentprobe

Targetingaptamer

Drug payload

Cationicmolecules

Targetingpeptide

DrugPEGspacer

Figure 2 Multifunctionalized nanoparticles (NPs) Graphical rep-resentation of surface-modified NPs with drugs (incorporatedwithin the core of NPs or conjugated to the surface) targetingmolecules (antibodies peptides aptamers and cationic molecules)for brain drug delivery with PEG for stealthiness and with fluores-cent probe as a tracer

ischemia [26] for delivery of opioid peptides [27] and braintumours [28]

Cationic Liposomes Cationic liposomes containing positivelycharged lipids have been developed and initially used astransfection vehicles to deliver genetic material (eg DNA)into the cell avoiding the lysosomal digestion The mostcommonly utilized cationic lipid is 12-dioleoyl-3-trimethyl-ammonium-propane (DOTAP) mixed with dioleoyl-phos-phatidylethanolamine (DOPE)The cholesterol also increasesthe levels of transfection and can potentially reduce thedestabilization of the liposomes in the presence of serum [29]

The interactions between cationic lipids and nucleicacids lead to the formation of structures which are calledldquolipoplexesrdquo [30] Lipoplexes are typically formed by directmixing between cationic liposomes and DNA solutionsPositively charged liposomes bind to negatively chargedphosphate molecules on the DNA backbone through electro-static interactions that are embedded and are shielded fromthe environment Generally complexes are formed with aslight excess positive charge to permit them to interact withthe negatively charged cell surface The cationic liposomesused are typically small before adding to DNA howevercomplexes formed with DNA exhibit diameters that rangefrom as small as 200 nm to structures as large as 2120583m Unlikeliposomes cationic liposomes undergo adsorptive-mediatedendocytosis and internalization in endosomes Upon acid-ification at pH 5 to 6 DOPE fuses and destabilizes theendosomal membrane releasing its contents to the cytosolTherefore drugs could be vehicled into endothelial cellssimilarly to DNA enhancing their crossing of the barrier andreaching neurons As a proof of this possibility transfection ofneuronal SH-SY5Y cells was achieved with the lipoplexes at adegree much higher than the degree obtained with the widelyand commonly utilized transfectant Lipofectamine cationic

ISRN Biochemistry 5

liposomes carrying a photoreactive drug resulted in a laser-stimulated cytotoxic effect on glioblastoma cells and showedthe ability to improve brain drug delivery of paclitaxel(a mitotic inhibitor used in cancer chemotherapy) in rodentsin vivo [31ndash33]

412 Solid Lipid Nanoparticles Solid lipid nanoparticles(SLN) are a stable lipid-based nanocarrier with a solidhydrophobic lipid core in which the drug can be dissolvedor dispersed [34] They are made with biocompatible lipidssuch as triglycerides fatty acids or waxes They are generallyof small size (around 40ndash200 nm) allowing them to crosstight endothelial cells of the BBB and escape from thereticuloendothelial system (RES) [35]

During their fabrication the melted lipid mixed withthe drug is commonly dispersed in an aqueous surfactantby high-pressure homogenization or microemulsificationThe advantages of SLN are their biocompatibility drugentrapment efficiency comparatively higher than other NPsand the ability to provide a continuous release of the drugfor several weeks [36] Moreover the composition of SLNcan be controlled modifying their surface properties to targetmolecules to the brain and to limit RES uptake [37]

Several reports are available describing an enhanced drugdelivery to the brain mediated by SLN For instance SLNcarrying a calcium channel blocker drug administered ivinto rodent showed that the drug was taken up to a greaterextent by the brain and maintained high drug levels for alonger time compared to free drug suspension

Wang et al have reported the synthesis of 310158405-dioctanoyl-5-fluoro-2-deoxyuridine (DO-FUdR) to overcome the lim-ited access of the drug 5-fluoro-2-deoxyuridine (FUdR) andits incorporation into SLN The results indicated that DO-FUdR-SLN had brain targeting efficiency in vivo of about 2-fold compared to free FUdR These authors report that SLNcan improve the ability of the drug to penetrate throughthe BBB and is a promising drug targeting system for thetreatment of central nervous system disorders [38 39]

42 Polymer-Based Nanoparticles

421 Polymeric Nanoparticles Polymeric NPs are composedof a core polymer matrix in which drugs can be embedded[40ndash42] with sizes usually between 60 and 200 nm A rangeof materials have been employed for delivery of drugs Inparticular in recent years some polymers have been designedprimarily for medical applications and have entered thearena of controlled release of bioactive agents Many ofthese materials are designed to degrade within the bodyMost popular ones are polylactides (PLA) polyglycolides(PGA) poly(lactide-co-glycolides) (PLGA) polyanhydridespolycyanoacrylates and polycaprolactone In spite of devel-opment of various synthetic and semi-synthetic polymersalso natural polymers such as chitosan can be utilized

Also in the case of polymeric NPs reports are avail-able describing an enhanced drug delivery to the brainmediated by these devices NPs made of PLGA embeddingantituberculosis drugs (rifampicin isoniazid pyrazinamide

and ethambutol) for cerebral drug deliverywere administeredto mice maintaining high drug levels for 5ndash8 days in plasmaand for 9 days in the brain much higher as comparedwith free drugs [43] InMycobacterium tuberculosis-infectedmice 5 doses of the NPs formulation (against 46 doses ofconventional free drugs) resulted in undetectable bacteriain the meninges [44] In another research [45] polybutyl-cyanoacrylate (PBCA) NPs were successfully utilized fordelivery of functional proteins into neurons and neuronal celllines

422 Polymeric Micelles Polymeric micelles are formedby amphiphilic copolymers whose aggregation in aqueousmedia leads to spheroidal structures with a hydrophilic shelland a hydrophobic core and with a good grade of stability[36] Stability can be improved by crosslinking between theshell or the core chains Additional tunable features of poly-meric micelles are the possibility to render them responsiveto external stimuli (pH light temperature ultrasound etc)[46] triggering a controllable release of entrapped drugsOne of the most utilized polymer is Pluronic type blockcopolymer based on ethylene oxide and propylene oxide

The possibility to use these NPs for brain drug deliv-ery has been described For instance chitosan-conjugatedPluronic nanocarriers with a specific target peptide forthe brain (rabies virus glycoprotein RVG29) following ivinjection in mice displayed in vivo brain accumulation eitherof a quantum dot fluorophore conjugated to the nanocarrieror of a protein loaded into the carrier [47] Other studieshave shown an increased central analgesic effect of micellar-vehicled drug [48]

423 Dendrimers Dendrimers are branched polymersreminding the structure of a tree A dendrimer is typicallysymmetric around the core and when sufficiently extended itoften adopts a spheroidal three-dimensional morphology inwater A central core can be recognized in their structure withat least two identical chemical functionalities starting fromthese groups repeated units of other molecules can originatehaving at least one junction of branching The repetitions ofchains and branching result in a series of radially concentriclayers with increased crowding The structure is thereforetightly packed in the periphery and loosely packed in thecore leaving spaces which play a key role in the drug-entrapping ability of dendrimers [49] Poly(amidoamine)or PAMAM is perhaps the most well-known molecule forsynthesis of dendrimers The core of PAMAM is a diamine(commonly ethylenediamine) which is reacted with methylacrylate and then with another ethylenediamine to makethe generation-0 PAMAM Successive reactions create highergenerations Albertazzi et al [50] showed that functionaliza-tion of PAMAMs dendrimers has a dramatic effect on theirability to diffuse in the CNS tissue in vivo and penetrate livingneurons as shown after intraparenchymal or intraventricularinjections

Kannan et al [51] showed that systemically administeredpolyamidoamine dendrimers localize in activated microgliaand astrocytes in the brain of newborn rabbits with cerebral

6 ISRN Biochemistry

palsy providing opportunities for clinical translation in thetreatment of neuroinflammatory disorders in humans

5 How NPs Can Cross the BBB

Many medicines are not able to reach the brain due to thelack of drug-specific transport systems through the BBBThedevelopment of new strategies based on NPs to enhance thebrain drug delivery is of great importance in the therapy anddiagnosis of CNS diseases and it is based on the interactionsbetween NPs and the BBB and on their intracellular trafficpathways

51 Crossing the BBB without Functionalization Althoughalmost all nanomaterials fall into the class of BBB imper-meable some exceptions have been reported in recent yearsFor instance gold and silica NPs have been shown to reachthe brain and accumulate in neurons even in the absenceof any specific functionalization with a mechanism thatsubstantially is still unknown In the case of silica the resultsindicated that NPs administered to rodents via intranasalinstillation entered into the brain and especially depositedin the striatum [52] In the case of gold NPs precise particledistribution in the brain was studied ex vivo by X-ray micro-tomography confocal laser andfluorescencemicroscopy [53]The authors found that the particles mainly accumulate inthe hippocampus thalamus hypothalamus and the cerebralcortex The same holds true for Titanium dioxide NPs thatwere found to cross the mice BBB particularly when smallerthan 40 nm [54]

52 Adsorptive-Mediated Transcytosis The concept of ad-sorptive-mediated transcytosis through the BBB was orig-inally suggested by the observation that cationic proteinscan bind the endothelial cell surface but also cross the BBB[55] The mechanism applied to NPs is based on the properfunctionalization of their surface allowing electrostatic inter-action with the luminal surface of BBB Given the presenceof negative charges on endothelial cells [56] this interactioncan be promoted by conferring a positive charge to the NPssurface

Different procedures can be followed to realize this issueA first possibility is to build up NPs made of componentsthat are bearing a positive charged at physiological pH (74)This is the case of nanosized vesiclesmade of bolaamphiphilicmolecules (amphiphilic molecules that have hydrophilicgroups at both ends of an hydrophobic chain) that followingintravenous administration to mice showed a marked accu-mulation of their encapsulated fluorescent cargo whereasnonencapsulated probe was detected only in peripheraltissues but not in the brain [57] In another investigation Jinet al [58] used SLN made with lipids extracted from depro-teinated lipoproteins and enriched with cationic cholesterylhydrochloride and phosphatidyl-ethanolamine The authorsafter intravenous administration of such cationic NPs for thedelivery of siRNA inhibiting c-Met expression suppressedtumor growth without evident signs of systemic toxicity inan orthotopic xenograft tumor mice model of glioblastoma

A second possibility is to functionalize the NPs surfacewith positively charged biomolecules combining their physic-ochemical features with biological activity This is the caseof cell-penetrating peptides (eg TAT peptides derived fromHIV gH625 derived from Herpes simplex virus type 1) andcationic proteins (eg albumin) [59] that have been exten-sively used for NPs decoration facilitating the BBB passageof drugs [60] As for example Rao et al [61] after admin-istration of ritonavir via TAT-conjugated NPs demonstratedapproximately an 800-fold higher level of drug in the brainwhen compared to that with free drug with a remarkableenhancement of drug delivery The authors suggested thatTAT-conjugated polymeric NPs are first mobilized in thebrain vasculatures then transported to the brain parenchymawhere they continue to release the drug

Polymeric micelles having TAT molecules on the surfacewere successfully fabricated also to incorporate antibioticsand were able to cross the BBB [62] In another study Xuet al [63] showed efficacy of TAT-polymeric NPs for thetreatment of C albicansmeningitis in rabbits Similar resultsare reported using another family of cell-penetrating peptides(SynB peptides RGGRLSYSRRRFSTSTGR) that were able toincrease drug permeability across a cocultured BBB modeldoubling drug transport in vivo in healthy mice [64]

Since the effect of cell-penetrating peptides could beinvalidated by the rapid systemic clearance of functionalizedNPs due to their positive charge in a study dedicated toinvestigate this issue Xia et al [65] utilized penetratin apeptide derived from Antennapedia protein (Drosophila)with relatively lower content of basic amino acids to func-tionalize poly(ethylene glycol)-poly(lactic acid) (PLGA)NPsfluorescently labeled with coumarin-6 and detected anincrease of fluorescence in the rodent brain with respect tounfunctionalized NPs

Xia et al [65] also combined the use of cell-penetratingpeptide to coumarin-6-loaded NPs for intranasal adminis-tration The amount of fluorescent probe detected in the ratcerebrum and cerebellum was found to be more than 2-foldcompared to that of coumarin carried by unfunctionalizedNPs Brain distribution analysis suggested that NPs afterintranasal administration could be delivered to the centralnervous system along both the olfactory and trigeminalnerves pathways

The efficacy of cationic albumin to functionalize andpromote NPs-carried drug delivery to the brain has beenrepeatedly reported [66 67]Theproperty of cationic proteinsto efficiently penetrate cells raises the question of the potentialtoxicity and immunogenicity of these proteins The possi-ble toxic effects include a generalized increase in vascularpermeability since breakdown of BBB permeability andother vascular beds has been observed following intravenousinjection of large amounts of cationic proteins but has notbeen seen when moderate amounts of these substances wereadministered [68]

53 Receptor-MediatedTranscytosis Oneof themost recentlyapplied strategies for drug delivery across the BBB endo-thelium using functionalized NPs is the one exploiting

ISRN Biochemistry 7

the transcytosis physiological mechanism of transport ofmacromolecules relying on the presence of specific recep-tors on the luminal surface of cells Transcytosis is theprocess by which extracellular cargo internalized at oneplasma membrane domain (eg apical) of a polarized cell istransported via vesicular intermediates to the controlateralplasma membrane (eg basolateral) As for example insulintransferrin apolipoproteins and 2-macroglobulin are someof the proteins that reach the brain following the path acrossendothelial cells

The rationale for exploiting this strategy with NPs is thatthe existing cellular mechanisms handling macromolecularcargoes may fit also to transport NPs after their functional-ization to interact with the same receptors

Transcytosis in endothelial cells starts with internal-ization of extracellular cargo into the cell by vesicularcarriers The cargo is subsequently processed via differentpathways to appropriate intracellular organelles and recycleddegraded or transcytosed to the contralateral side Strongmorphological and biochemical evidence suggest that thetwo membranes apical and basolateral are interconnectedvia vesicular intermediates involving multivesicular bodiesor a system of endosomal vacuoles and tubule vesiclesPhosphoinositide 3-kinase an enzyme increasingly demon-strated to play an important regulatory role inmany vesiculartrafficking events also appears to regulate transcytotic trafficbetween the two endosomal compartments

Transcytosis in endothelial cells starts with uptake eitherthrough clathrin-coated pits by caveolae or caveolae-likemembrane domains [69] that will be described here below

The first step of internalization through clathrin-mediated endocytosis is the binding of a ligand to a specificcell surface receptor This results in the clustering of theligand-receptor complexes in coated pits on the plasmamembrane which are formed by the assembly of cytosoliccoat proteins the main assembly units being clathrin whichform a polygonal lattice in the surface of the membrane andadaptor protein complexes which mediate the assembly ofthe clathrin lattice on the membrane The coated pits theninvaginate and pinch off from the plasma membrane to formintracellular clathrin-coated vesicles The clathrin coat thendepolymerizes resulting in early endosomes which fusewith each other or with other preexisting endosomes to formlate endosomes that further fuse with lysosomes Vesiculartrafficking after CME is controlled by the action of smallGTPases the Rab proteins

The second mechanisms internalization (caveolar) hasbeen clarified following the trafficking of some viruses thatuse caveolae to gain entry into the cells Caveolae aresmall flask-shaped invaginations of the plasma membranewith a size of about 50ndash60 nm that are rich in cholesteroland sphingolipids Viruses initially associate with the cellmembrane and then become trapped in relatively stationarycaveolae The subsequent intracellular uptake of caveolaeleads to intracellular organelles that are distinct from classicendosomes the presence of the protein caveolin in theseorganelles gave rise to the name caveosomes In contrast tothe dynamic nature of endosomes caveolae are highly stableand are only slowly internalized Another major difference is

that the caveolar uptake does not lead to a decrease of pHand to a degradative pathway of their cargo as in endoso-mallysosomal pathway

It is clear that the different pathways of NPs internal-ization affect their delivery to different intracellular com-partments and may affect their final destination To obtaininsight into the properties of drug delivery vehicles thatdirect their intracellular processing in brain endothelial cellsthe intracellular traffic of fixed-size nanoparticles in anin vitro BBB model as a function of distinct nanoparticlesurface modifications has been investigated Previous obser-vations [70] that latex particles with a diameter ge500 nm areinternalized by nonphagocytic B16 cells through caveolaewhereas particles up to 200 nm in diameter are efficientlytaken up via clathrin-mediated endocytosis were succes-sively confirmed with Silica-Hydroxyl NPs on immortalizedhuman brain capillary endothelial cell cultures [71] In theinvestigation of Georgieva et al [71] 500 nm particles wereused uncoated surface functionalized with cationic polymerpolyethyleneimine (PEI) or with prion protein The resultssuggested that uncoated NPs are internalized through cave-olae nanoparticles carrying a net cationic charge accom-plished by PEI followed an adsorptive endocytotic routeand particles surface-modified with prion protein followedreceptor-mediated endocytotic route Therefore the authorsconcluded that the NPs intracellular pathway is dictated bythe particle surface characteristic for a given size Mostinterestingly they found that the transcytotic potential ishigher for the receptor-mediated and caveolar pathways andlower for the adsorptive-mediated

However the enhancement of brain delivery obtainedwith drug-loaded NPs exploiting receptor- or caveolar-mediated transcytosis is currently quantitatively limited incomparison with the free drug Consequently also its clinicalrelevance is still scarce If we compare the hydrodynamicsize of most physiological proteins with that of NPs we areconfronting objects in the order of 5ndash10 nm size with thosethat in most cases are in the order of tenths of nanome-ters and commonly reach 100 nm and more Therefore itis conceivable that the transcytotic traffic may become abottleneck when transporting NPs It is also predictablethat smaller size NPs closer to the size of physiologicalmolecules would be facilitated to enter the same intracellu-lar transport pathways Following the strategy of receptor-mediated transport NPs made of gold PLGA chitosanPAA dendrimers and liposomes have been functionalizedimproving the delivery of drugs such as caspase inhibitorsendomorphin tamoxifen and tramadol and throwing thebasis for treatment of neurological diseases [72ndash79]

Exploring and targeting new receptors that could beutilized for receptor-dependent endocytosis are likely toprovide more efficient systems of brain drug delivery mainlybecause these uptakemechanisms are relatively unaffected bylysosomal degradation

531 Lipoprotein Receptors Apolipoprotein E (apoE) is a 34-kDa protein constituent of both very-low-density lipopro-tein (VLDL) and high-density lipoprotein (HDL) which

8 ISRN Biochemistry

transports cholesterol and other lipids in the plasma and inthe CNS [80 81] The lipoproteins complexes can be takenup in the brain through the recognition of apoE by specificreceptors at the BBB which include the low-density lipopro-tein receptor (LDLR) and the LDLR-related protein (LRP)

Taking into consideration that LRP has been reported tobe highly expressed on endothelial brain microvessels [82]receptor-mediated transcytosis using NPs functionalized tobind this target has been exploited in several ways

First by exploiting the preferential absorption of ApoEon some types of NPs when in serum This feature has beendescribed for PBCA NPs coated with polysorbate 80 indeeddisplaying the ability to cross the BBB in vivo in animalmodels [83ndash85] and for PEGylated PHDCA NPs able topenetrate into brain endothelial cells in vitro [86]

Taking advantage of such opportunity the formation ofa stable ApoE decoration of NPs surface by covalent bindinghas been utilized to functionalize albumin-NPs or liposomesthat showed the capacity of enhancing BBB passage in vivo inrodent models [87ndash89]

It should be questioned whether other apolipoproteinsmay be employed for NPs functionalization to confer onthem the ability to enhance brain drug delivery In order toanswer this question in an investigation of Kreuter et al [90]PBCA NPs loaded with dalargin or loperamide were coatedwith different apo-lipoproteins AII B CII E or J coatedor not with polysorbate 80 and then injected in mice andthe drug effect on CNS was evaluated The results showedthat only NPs coated with apolipoprotein B or E were able toachieve an antinociceptive effect This effect was significantlyhigher after polysorbate-precoating and apolipoprotein B orE-overcoating [90]

The region of apoE that is critical for interaction with theLDL receptor resides between amino acid residues 140 and160 Several studies with synthetic peptides have investigatedthe structural features of the LDLR-binding sequence ofApoE [91 92]

Laskowitz et al [81] derived an apoE-mimetic pep-tide from amino acids 133ndash149 named COG133 (LRVR-LASHLRKLRKRLL) which retains its biological activity invitro and in vivoThis capacity is displayed also by a fragmentof 26 aa from ApoE4 [93]

It has also been reported that the tandemdimer (141ndash155)2

is recognized by the LDLR in contrast to themonomeric pep-tide (141ndash155) [94] Also a shorter sequence of this peptide thetandem dimer (141ndash150)

2 retains this ability [95] Probably

as a consequence of these observations sterically stabilizedliposomeswere functionalized onlywithApoE tandemdimerpeptide (141ndash150)

2 but not with the monomer and were

shown to be efficiently taken up by rat brain capillaryendothelial cells [96] Interestingly in spite of the theoreticalpremises based on receptor-mediated endocytosis liposomestagged with (141ndash150)

2were nonselectively internalized into

cultured BBB cells and clathrin- or caveolin-dependentendocytosis was not demonstrable [97]

However in a successive investigation the ApoE-derivedpeptide monomer 141ndash150 was utilized by Re et al [98]in comparison with the dimer for the functionalization ofliposomes entrapping a radioactive derivative of curcumin

The investigation showed a higher uptake of the drug byhuman endothelial cells and an enhancement of permeabilityof the drug across an in vitromodel of the BBBmade with thesame cells when using monomer-functionalized liposomes

Apart from the amino acid sequence other factors mayaffect the cellular uptake of these peptides [98] These factorsinclude the type of peptide its cationic nature its mode ofexposure to the cell surface the nature of the cargo and thechemical linkage between the peptide and the cargo otherthan the peptide surface density on the cellular uptake ofnanoparticles [98 99]

Finally also Angiopep-2 a ligand of LRP possesses a highbrain penetration capability in both in vitro model of theBBB and in situ brain perfusion in mice [100] PEG-PAMAMdendrimers functionalized using this peptide resulted ina high accumulation of a delivered gene into brain afterintravenous administration into mice [101] moreover alsofunctionalized polymeric NPs and carbon nanotubes (CNT)have been produced showing the ability to reach gliomatumors in mice [102 103]

532 Transferrin Receptor (TfR) The transferrin receptor(TfR) is the most widely studied receptor for BBB targetingTfR is a transmembrane glycoprotein consisting of twolinked 90-kDa subunits each one binding a transferrinmolecule The receptor is highly expressed on immature ery-throid cells placental tissue and rapidly dividing cells bothnormal and malignant [104] Furthermore it is expressedon hepatocytes and endothelial cells of the BBB The role ofthe receptor is the regulation of cellular uptake of iron viatransferrin a plasma protein which transports iron in thecirculation Cellular uptake starts with the binding of trans-ferrin to the transferrin receptor followed by endocytosis[105]

Iron-bound transferrin has a high affinity for the TfRtherefore it has been used with success as a ligand for func-tionalization and targeting of liposomes to cultured brainendothelial cells [106 107] However it is likely that thatNPs decorated with transferrin would not be performantin vivo since transferrin receptors are almost saturated inphysiological conditions because of the high circulatinglevels of endogenous protein [108] Nevertheless successfulbrain targeting using transferrin as a targeting ligandhas beenaccomplished in vivo [109 110] Concerning the specificity oftransferrin a comparative study has been carried out betweentransferrin or lactoferrin a multifunctional protein of thetransferrin family widely represented in various secretoryfluids such as milk [111] Lalani et al [112] compared in vivodistribution in mice of PLGA NPs surface modified with thetwo proteins and showed a better performance to reach thebrain in the case of lactoferrin

In order to avoid the competition with endogenous trans-ferrin circulating in blood the use of monoclonal antibodies(mAbs) directed against transferrin receptors on the BBB hasbeen suggested because they recognize different epitopes onthe receptor [113] For instance OX26 8D3 and R17217 mAbbind to TfR and have also been shown to undergo receptor-mediated transcytosis

ISRN Biochemistry 9

Among these it is still debated which mAb is the bestperforming to be used for the decoration of NPs surface Themostwell known isOX26 an antibody directed against the ratTfR that has been successfully used in many brain targetingstudies in vivo [114] and also in vitro using BBB cellularmodels [115] However Lee et al [116] have shown that theOX26monoclonal antibody is not an effective brain targetingmolecule in mice Moreover they demonstrated that othertwo monoclonal antibodies 8D3 and RI7217 directed againstthe mouse TfR had a higher permeability of the mouseBBB in vivo with respect to the brain uptake of the OX26antibody which was negligible Additionally they showedthat RI7217wasmore selective for the brain than 8D3 becausethis antibody was less taken up by the liver and kidney Ithas been shown that RI7217 covalently coupled to humanserum albumin is able to transport loperamide across theBBB [110] More recently it has been shown that also thechemical linkage of anti-TfR on the NPs surface could affectthe crossing of BBB in vitro [117] The authors comparedliposomes covalently coupled with mAbs (obtained by react-ing thiolatedmAbs to phosphatidyl-ethanolaminemaleimideinserted in the liposome bilayer) with liposomes decoratedwith biotinylated mAbs via an avidin bridge The Authorsfound an higher cellular uptake and permeability across anin vitro BBB model made of immortalized human braincapillary endothelial cells of the liposomes covalently coupledwith mAbs suggesting that the covalent ligation could bepreferentially chosen for NPs decoration

54 Retrograde Transport Transsynaptic retrograde trans-port could enable some types of nanocarriers to travel fromperipheral nerve terminals to neuronal cell bodies in the CNS[118] Studies in this regard have shown that NPs modifiedwith PEI and other polyplexes display active retrogradetransport along neurites but are unable to mediate efficientbiological actions upon reaching the neuronal body [119]

55 BBB Breakdown BBB breakdown occurs in neuroin-flammatory diseases [120] NPs can transiently and reversiblyopen the tight junctions located at the BBB and other sitesthus increasing their paracellular permeability [121 122]In particular blood-brain barrier disruption therapy is anintensive effectiveway of sendingmedication to brain tumors[123]

Nevertheless it is known that tight junctions can beopened only to a limited extent [124] thus only NPs smallerthan about 20 nm can use this pathway to penetrate into thebrain through the BBB

56 Exploiting MonocyteMacrophage Infiltration in the CNSMonocytemacrophage infiltration in the CNS plays a keyrole in neuroinflammation as well as in lesion developmentand brain injury in neurological diseases such as multiplesclerosis (MS) and stroke [124ndash126] Knowledge of activephases of cell infiltration during CNS disorders is importantbecause anti-inflammatory treatments can target cell adhe-sion molecules and chemokines guiding cellular trafficking[127] The monocyte infiltration through the BBB is also

widely believed to play an important role in HIV infectionof the CNS The blood-brain barrier appears unaltered untilthe late stage of HIV encephalitis HIV flux that movestoward the brain thus relies on hijacking with immune-activated leukocytes mainly monocytesmacrophages fromthe periphery [128]

In this paper BBB crossing by immune-activated macro-phages appears to suggest possible strategies for future ther-apeutic developments employing NPs This strategy couldbe realized at least in two ways (1) by embedding NPs intoactivated monocytes used as Trojan horses to reach the brain(2) by designing NPs mimicking activated monocytes

561 Trojan Monocytes for NPs Delivery to the Brain Nano-particulate drug delivery systems have been used to avoidthe RES clearance and achieve longer circulation time forenhanced tissue uptake However the enhancing of NPsphagocytosis by monocytes can be considered as an uncon-ventional approach to deliver NPs-loaded drugs to thebrain After phagocytosis of NPs monocytes just like Trojanhorses may transport their cargo into the brain Aferganet al [129] taking this approach embedded serotonin aBBB impermeable neurological drug into negatively chargedliposomes and analyzed brain uptake in rats and rabbitsThe performance of liposomal serotonin was significantlybetter leading to two-fold higher drug concentration inbrain than the free drug Since treatment of animals byalendronate resulted with inhibition of monocytes but not ofneutrophils andwith no brain delivery the authors suggestedthat monocytes are the main transporters of liposomes tothe brain In spite of the fact that the clinical relevance ofthis investigation is limited the Trojan monocyte approachprovides a new possibility of more effective treatment ofbrain-associated inflammatory disorders including multiplesclerosis and Alzheimerrsquos disease which are characterizedwith increased passage of immune cells across the BBB[130]

In other examples in order to improve the delivery ofcontrast agents to the brain iron oxide NPs administeredintravenously in vivo have been shown to detect activatedmacrophage infiltration in multiple sclerosis either in theCNS of humans [131 132] or rodentmodel [133ndash137] in strokeeither in human [138 139] or animal brain ischemia [140ndash143] in human or murine intracranial tumors [144 145] inEAE [146ndash148] or in an ischemiareperfusion long-lived ratmodel [149]

562 NPs Mimicking Activated Monocytes The therapeu-tic efficacy of drug-loaded NPs systemically administereddepends on their ability to evade the immune system tocross the biological barriers of the body and to localizeat target tissues Parodi et al [150] show that nanoporoussilicon particles can successfully perform all these actionswhen they are coated with cellular membranes purifiedfrom leukocytes avoiding being cleared by the immune sys-tem Furthermore they can communicate with endothelialcells through receptor-ligand interactions and transport andrelease a doxorubicin payload across an inflamed endothelial

10 ISRN Biochemistry

barrier in vitro Also the accumulation of coated NPs inmice inoculated with murine B16 melanoma was enhancedcompared with that of non coated NPs Particle coatingusing leukocyte membranes led to an approximately twofoldincrease in particle density in the tumor

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsit is predictable that the research of NPs mimicking immunecells might be effective in brain-associated disorders and willreceive a stimulus in this direction in the next years

6 Factors Affecting NPs Brain Drug Delivery

61 NPs Diffusion inside the Brain Parenchyma While thisfactor is likely not particularly relevant when brain drugdelivery is sought after it could be very important when thepassage of the BBBbyNPs is looked for since the extracellularspace (ECS) of the brain parenchyma could limit their diffu-sion or even preclude their entrance into the brainThe abilityto achieve brain penetration with larger NPs is expected toallow more uniform longer lasting and effective delivery ofdrugs within the brain and may in particular find practicein the treatment of brain tumors stroke neuroinflammationand other brain diseases where the BBB is compromised orwhere local delivery strategies are feasible

Today it is well established that the ECSoccupies a volumefraction of between 15 and 30 in normal adult brain tissuewith a typical value of 20 and that this falls to 5 duringglobal ischemia [151 152]

It is less obvious what the true size of the spaces betweencells is Small molecules such as inulin and sucrose diffusethrough the ECS with a decreased diffusion coefficient withrespect to water suggesting the existence of limitation to theirmovements [153]

Possible sources of the limitations to the diffusing mol-ecules are (a) the presence of cellular obstructions (b) trap-ping of molecules in dead-space microdomains (c) a viscousdrag imposed by themacromolecules that compose the extra-cellular matrix or drag arising from the walls of the channelswhen molecules are large such as in the case of NPs(d) transient binding to cell membranes or extracellularmatrix (e) nonspecific interaction with negative charges onthe extracellular matrix when the diffusing molecule hasadequate charge density

A different type of model was proposed by Thorne andNicholson [154] to explain the higher tortuosity experimen-tally measured for larger substances such as dextran andespecially large synthetic quantum dot nanocrystals in the invivo rat cortex It was assumed that the quantum dots with ahydrodynamic diameter of 35 nm were close to the averagewidth of the ECS and depending on whether a planar ortubularmodel was adopted the estimated ECSwidth was 38ndash64 nm

In counter tendency to Thorne and Nicholson [154]Nance et al [155] report that NPs as large as 114 nm indiameter diffused within the human and rat brain only ifthey were densely coated with PEG Using these minimally

adhesive PEG-coated NPs they estimated that human braintissue ECS has some pores larger than 200 nm and that morethan one-quarter of all pores are ge100 nm

In addition to ECS in CNS there is also much interest inthe possibility that perivascular spaces fluid-filled channelssurrounding arteries arterioles veins venules and possiblyevenmicrovessels offer potential pathways for rapid flow intoand out of brain parenchyma Measurements of perivascularspace widths in mammals suggest that their typical dimen-sions may be at least 2 orders of magnitude greater thanthe neocortical ECS width (eg arteriole perivascular spaceshave been reported in the range of 5ndash10 120583m or larger (inrodents and humans))

62 Effect of Protein Corona Different physicochemicalproperties not only size may determine the ability ofnanoparticles to reach the brain The situation is furthercomplicated by the formation of a so-called ldquocoronardquo ofbiomolecules on the surfaces of nanoparticles the composi-tion of which may vary depending on the route of exposureand on the physicochemical surface properties of NPs Theacquisition of a corona of biomolecules on the surface ofNPs may also determine whether NPs are able to cross fromone compartment to another and whether they are taken upeffectively by cells or not [156]

In practical situations in which nanoparticles interactwith living organisms the nanoparticle surfaces are initiallyexposed to a biological fluid such as blood dependingon the route of administration For instance NPs injectedintravenously would be exposed to blood plasma containingan excess of proteins and many other complex biomoleculeswhich bind competitively with the surface of the nanoparti-cles

The current idea is that ldquobarerdquo nanoparticles do notexist in vivo because they are immediately modified bythe adsorption of blood proteins with higher affinities forthe particle surface forming a more or less tightly boundlayer (the so-called hard corona) and a weakly associatedmobile layer (the so-called soft corona) When this issue wasinvestigated it has been found that typical coronas containa limited number and types of molecules gathered fromthe blood in spite of the fact that biological fluids containthousands of proteins [157] Moreover it should be noted thatthe corona may also play a role in other undesirable effectsof NPs in living systems such as complement activation andblood clotting and may not necessarily play a role only incellular uptake

It should be pointed out that none of the in vitro exper-iments conducted to study the process of NPs translocationto the brain takes into account the surface modification ofNPs inside the blood and how can this affect the crossingof the BBB This issue needs much further investigationMoreover NPs once internalized by endothelial BBB cellsthey may also exit towards the brain covered with differentbiomolecules depending on that they have undergone endo-cytosistranscytosisexocytosis and thus exert additionaleffects (eg toxicity) on neuron Also this issue has not yetbeen investigated

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

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[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

[12] W M Pardridge ldquoDrug transport across the blood-brainbarrierrdquo Journal of Cerebral Blood Flow amp Metabolism vol 32no 11 pp 1959ndash1972 2012

[13] A Minn S Leclerc J M Heydel et al ldquoDrug transport into themammalian brain the nasal pathway and its specific metabolicbarrierrdquo Journal of Drug Targeting vol 10 no 4 pp 285rndash296r2002

[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

[23] L Martin-Banderas M A Holgado J L Venero J Alvarez-Fuentes and M Fernadez-Arealo ldquoNanostructures for drugdelivery to the brainrdquoCurrentMedicinal Chemistry vol 148 no34 pp 5303ndash5321 2011

[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

[26] T Ishii T Asai D Oyama et al ldquoTreatment of cerebralischemia-reperfusion injury with PEGylated liposomes encap-sulating FK506rdquo FASEB Journal vol 27 no 4 pp 1362ndash13702013

[27] A Lindqvist J Rip P J Gaillard S Bjorkman and MHammarlund-Udenaes ldquoEnhanced brain delivery of the opioidpeptide DAMGO in glutathione PEGylated liposomes amicro-dialysis studyrdquoMolecular Pharmacology 2012

[28] A Orthmann R Zeisig R Suss D Lorenz M Lemm andI Fichtner ldquoTreatment of experimental brain metastasis withMTO-liposomes impact of fluidity and LRP-targeting on thetherapeutic resultrdquo Pharmaceutical Research vol 29 no 7 pp1949ndash1959 2012

[29] M T da Cruz S Simoes and M C de Lima ldquoImprovinglipoplex-mediated gene transfer into C6 glioma cells andprimary neuronsrdquo Experimental Neurology vol 187 no 1 pp65ndash75 2004

[30] F Artzner R Zantl and J O Radler ldquoLipid-DNA and lipid-polyelectrolyte mesophases structure and exchange kineticsrdquoCellular andMolecular Biology vol 46 no 5 pp 967ndash978 2000

[31] A Molinari M Colone A Calcabrini et al ldquoCationic lipo-somes loaded with m-THPC in photodynamic therapy for

14 ISRN Biochemistry

malignant gliomardquo Toxicology in Vitro vol 21 no 2 pp 230ndash234 2007

[32] Y Obata G Ciofani V Raffa et al ldquoEvaluation of cationicliposomes composed of an amino acid-based lipid for neuronaltransfectionrdquo Nanomedicine vol 6 no 1 pp e70ndashe77 2010

[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

[36] B Mishra B B Patel and S Tiwari ldquoColloidal nanocarriersa review on formulation technology types and applicationstoward targeted drug deliveryrdquo Nanomedicine vol 6 no 1 ppe9ndashe24 2010

[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

[40] S Md M Ali S Baboota et al ldquoPreparation characteri-zation in vivo biodistribution and pharmacokinetic studiesof donepezil-loaded PLGA nanoparticles for brain targetingrdquoDrug Development and Industrial Pharmacy 2013

[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

[43] Y E Choonara V Pillay V M K Ndesendo et al ldquoPoly-meric emulsion and crosslink-mediated synthesis of super-stable nanoparticles as sustained-release anti-tuberculosis drugcarriersrdquoColloids and Surfaces B vol 87 no 2 pp 243ndash254 2011

[44] R Pandey and G K Khuller ldquoOral nanoparticle-based antitu-berculosis drug delivery to the brain in an experimental modelrdquoJournal of Antimicrobial Chemotherapy vol 57 no 6 pp 1146ndash1152 2006

[45] L Hasadsri J Kreuter H Hattori T Iwasaki and J M GeorgeldquoFunctional protein delivery into neurons using polymericnanoparticlesrdquo Journal of Biological Chemistry vol 284 no 11pp 6972ndash6981 2009

[46] A V Kabanov E V Batrakova N S Melik-Nubarov et alldquoA new class of drug carriers micelles of poly(oxyethylene)-poly(oxypropylene) block copolymers as microcontainers for

drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

[50] L Albertazzi L Gherardini M Brondi et al ldquoIn vivo dis-tribution and toxicity of PAMAM dendrimers in the centralnervous system depend on their surface chemistryrdquo MolecularPharmacology vol 10 no 1 pp 249ndash260 2013

[51] S Kannan H Dai R S Navath et al ldquoDendrimer-basedpostnatal therapy for neuroinflammation and cerebral palsy ina rabbit modelrdquo Science Translational Medicine vol 4 no 130Article ID 130ra46 2012

[52] J Wu C Wang J Sun and Y Xue ldquoNeurotoxicity of silicananoparticles brain localization and dopaminergic neuronsdamage pathwaysrdquoACSNano vol 5 no 6 pp 4476ndash4489 2011

[53] F Sousa S Mandal C Garrovo et al ldquoFunctionalized goldnanoparticles a detailed in vivo multimodal microscopic braindistribution studyrdquo Nanoscale vol 2 no 12 pp 2826ndash28342010

[54] Y Ze L Zheng X Zhao et al ldquoMolecular mechanism oftitanium dioxide nanoparticles-induced oxidative injury in thebrain of micerdquo Chemosphere 2013

[55] R D Broadwell ldquoTranscytosis of macromolecules through theblood-brain barrier a cell biological perspective and criticalappraisalrdquo Acta Neuropathologica vol 79 no 2 pp 117ndash1281989

[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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2 ISRN Biochemistry

to the vascular layer of brain capillary endothelial cells whichare interconnected side-by-side by tight and adherens junc-tions Tight junctions perform two functions (i) they preventthe passage of small molecules and ions through the spacebetween cells so that their passagemust occur by entering thecells (by diffusion or active transport) This pathway controlsthe type and amount of substances that are allowed to pass (ii)they prevent the movement of integral membrane proteinsbetween the apical and basolateral membranes of the cell sothat each of the cell membrane surfaces preserves its peculiarfunctions for example receptor-mediated endocytosis atthe apical surface and exocytosis at the basolateral surfaceThree integral proteins are present at the tight junctionsoccludin claudins and junctional adhesion molecules Theformer two constitute the backbone of junction strands whilejunctional adhesionmolecules are important for trafficking ofT-lymphocytes neutrophils and dendritic cells from the vas-cular compartment to the brain during immune surveillanceand inflammatory responses Adherens junctions providestrong mechanical attachments between adjacent cells andare built from cadherins and catenins The compact networkof interconnections is conferring to the endothelial layer ofthe BBB a transelectrical resistance gt1500Ω cm2 which isthe highest among all other endothelial districts The com-pactness of the endothelial BBB layer precludes the passageacross intercellular junctions (paracellular passage) limitingthe possibility of exchanges between the two compartmentsvirtually through passages transiting across the cellular body(transcellular passage)

However the BBB is not only a mechanical fence butalso a dynamic biological entity in which active metabolismand carrier-mediated transports occur Nutrients includingglucose amino acids and ketone bodies enter the brain viaspecific transporters whereas receptor-mediated endocyto-sis mediates the uptake of larger molecules such as neu-rotrophins and cytokines [6ndash10] The BBB prevents the brainuptake of most pharmaceuticals with the exception of smallhydrophilic compounds with a mass lower than 150Da andhighly hydrophobic compounds with amass lower than 400ndash600Da that can cross the membrane by passive diffusion [9]The list of BBB-permeant drugs includes opiates (eg mor-phine methadone and meperidine) anxiolytics (diazepamtemazepam) SSRIs (paroxetine) and antipsychotics (chlor-promazine promethazine) but does not include the majorityof antibiotics and antitumorals

As above said the tightness of the BBB is preventingthe pharmacological therapy of a number of neurologicaldiseases It should also be mentioned that a further obstaclefor drugs crossing the cerebral capillary endothelium andentering the brain parenchyma is represented by the pres-ence of the P-glycoprotein pump in the BBB allowing therecognition of molecules necessary for the brain to enter thebrain and the expulsion of other molecules pharmaceuticalsincluded

Given such premises it is conceivable that different ap-proaches have been tried to allow pharmaceuticals to over-come the BBB These explorative strategies have been ran-ging from invasive techniques for example through osmotic

opening of the BBB [11] to chemical modifications of drugsin order to take advantage of physiological carrier-mediatedtransports or exploiting the so-called ldquoTrojan horserdquo technol-ogy coupling BBB-impermeant pharmaceutical to moleculesable to cross the barrier taking advantage of receptor-mediated transport systems [12]

Alternative routes of administration able to reach thebrain bypassing the BBB (eg intranasal) have been activelyinvestigated but in the line of principle they are facingthe constraints of the limited surface of adsorption of theolfactory bulb which isminimal compared to that of the BBBthus quantitatively reducing the possibility to reach the brainwith relevant amounts of drugs [13]

3 Nanotechnology for Brain Drug Delivery

In the recent years with the advent of nanomedicine engi-neered tunable devices with the size in the order of billionthofmeters have been proposed as an intriguing tool potentiallyable to solve the unmet problem of enhancing drug transportacross the BBB [14 15] Among different devices nanoparti-cles (NPs) technology is rapidly advancing NPs are objectssized between 1 and 100 nm [16] that work as a whole unit interms of transport and properties

The types of NPs that are more popular for biomedicalapplications are reported in Figure 1

The reasons for this expectation are most of all linked tothe possibility of NPsmultifunctionalization coupled to theirability to carry drug payloads included BBB-impermeantdrugs In particular the rationale of using NPs for brain drugdelivery is that proper surface multifunctionalization maypromote at the same time either their targeting of the BBBor the enhancement of its crossing The possibility for BBB-impermeant drugs to reach the brain when vehicled by NPsis based upon the fact that their crossing of the barrier willdepend completely on the physicochemical and biomimeticfeatures of the NPs vehicle and will not depend anymore onthe chemical structure of the drug which is hindered insidethe NPs

What makes NPs even more attractive for medical appli-cations is the possibility of conferring on them featuressuch as high chemical and biological stability feasibility ofincorporating both hydrophilic and hydrophobic pharma-ceuticals and the ability to be administered by a varietyof routes (including oral inhalational and parenteral) [17]Moreover NPs can be functionalized by covalent conjugationto various ligands (such as antibodies proteins or aptamers)to target specific tissues The large surface-area-to-volumeratio of NPs permits multiple copies of a ligand to be attachedand to dramatically increase their binding affinity via themultivalent functionalization [18]

When designing NPs for clinical applications it shouldbe remembered that their systemic administration generatesimportant modifications In particular the nonspecific inter-action between the shell of NPs and many classes of proteinscirculating in the bloodstream leads to the adsorption ofopsonins on their surface forming the so-called ldquocoronardquo

ISRN Biochemistry 3

Liposomes Solid lipid nanoparticle Non-polymeric micelles

Lipoplex

+

+ +

+

+

+

+

++

+

+

+

Dendrimers Polymeric nanoparticle

Polymeric micelle Nanotubes Silica nanoparticle

Quantum dots Gold nanoparticle Magnetic nanoparticle

Figure 1 Different types of nanoparticles (NPs) Graphical representation of the most commonly used NPs for biomedical applications NPsare typically by a size measuring not more than 100 nm and have significant potential for delivering drugs across the blood-brain barrier Thesize of quantum dots is usually less than 10 nm

These proteins substantially change the bare material proper-ties determining the removal of NPs from circulation by thereticuloendothelial systemmainly located in spleen and liverThe most common approaches used for escaping RES are toformulate the particles with neutral surface charge to coat

their surface with different hydrophilic surfactants such aspolysorbates and polyethylene glycol (PEG) and to use smallsize nanoparticles (eglt80 nm) [19] NPswith these featurescalled ldquostealthrdquo are able to avoid the reticuloendothelialsystem to display long circulation time and stability in blood

4 ISRN Biochemistry

and may be functionalized to successfully target and crossthe BBB [20] Finally NPs should be nontoxic either forcells in the bloodstream or for healthy bystanding cells andshould be biodegradable and biocompatible noninflamma-tory and nonimmunogenic [21] The possibilities of func-tionalization of MP for brain drug delivery are depicted inFigure 2

It is also important to point out that the tailoring ofNPs toenhance drug delivery to the brain does not necessarily implytheir ability to cross the BBB themselves It is predictable thatNPs could play this role at least in two ways

(i) by increasing the drug concentration inside or atthe luminal surface of BBB cells establishing a localhigh concentration gradient between blood an brainhigher than that obtainable after systemic administra-tion of the free drug The gradient should then favorthe enhanced passive diffusion of the drug As forexample this task could be realized by synthesizingNPs functionalized to target brain capillary endothe-lial cells This feature can be followed or not by theirsubsequent uptake from targeted cells [22]

(ii) by moving themselves into the CNS together withtheir drug cargo As for example this task can berealized enabling NPs targeting of brain capillaryendothelial cells and their subsequent transcellularpassage across the BBB [23]

For the completeness of this review in the next section themain features ofNPs commonly utilized formedical purposesand already utilized or promising candidates for brain drugdelivery will be described

4 Nanoparticles for Medical Applications

41 Lipid-Based Nanoparticles

411 Liposomes Liposomes are the first generation ofnanoparticulate drug delivery systems [24] and are consti-tuted by one or more vesicular bilayers (lamellae) composedof amphiphilic lipids delimiting an internal aqueous com-partment Usually the liposomal lipid bilayer is composedof biocompatible and biodegradable lipids present in bio-logical membranes Common liposome constituents are sph-ingomyelin phosphatidylcholine and glycerophospholipidsCholesterol an important component of cell membranesis frequently included in liposome formulations because itdecreases the bilayer permeability and increases the stabilityof the liposome in vivo Liposomes are classified on thebase of their size and the number of lamellae as follows (i)small unilamellar vesicles (SUV) with a size up to 100 nmand one bilayer (ii) large unilamellar vesicles (LUV) with asize gt100 nm and one bilayer and (iii) multilamellar vesicles(MLV) that can reach a size of several 120583m and made of manyconcentric lipid bilayers

Liposomes have been largely utilized for brain drugdelivery (for a review see [25]) for the treatment of cerebral

+ +++

++

Targetingantibody

Fluorescentprobe

Targetingaptamer

Drug payload

Cationicmolecules

Targetingpeptide

DrugPEGspacer

Figure 2 Multifunctionalized nanoparticles (NPs) Graphical rep-resentation of surface-modified NPs with drugs (incorporatedwithin the core of NPs or conjugated to the surface) targetingmolecules (antibodies peptides aptamers and cationic molecules)for brain drug delivery with PEG for stealthiness and with fluores-cent probe as a tracer

ischemia [26] for delivery of opioid peptides [27] and braintumours [28]

Cationic Liposomes Cationic liposomes containing positivelycharged lipids have been developed and initially used astransfection vehicles to deliver genetic material (eg DNA)into the cell avoiding the lysosomal digestion The mostcommonly utilized cationic lipid is 12-dioleoyl-3-trimethyl-ammonium-propane (DOTAP) mixed with dioleoyl-phos-phatidylethanolamine (DOPE)The cholesterol also increasesthe levels of transfection and can potentially reduce thedestabilization of the liposomes in the presence of serum [29]

The interactions between cationic lipids and nucleicacids lead to the formation of structures which are calledldquolipoplexesrdquo [30] Lipoplexes are typically formed by directmixing between cationic liposomes and DNA solutionsPositively charged liposomes bind to negatively chargedphosphate molecules on the DNA backbone through electro-static interactions that are embedded and are shielded fromthe environment Generally complexes are formed with aslight excess positive charge to permit them to interact withthe negatively charged cell surface The cationic liposomesused are typically small before adding to DNA howevercomplexes formed with DNA exhibit diameters that rangefrom as small as 200 nm to structures as large as 2120583m Unlikeliposomes cationic liposomes undergo adsorptive-mediatedendocytosis and internalization in endosomes Upon acid-ification at pH 5 to 6 DOPE fuses and destabilizes theendosomal membrane releasing its contents to the cytosolTherefore drugs could be vehicled into endothelial cellssimilarly to DNA enhancing their crossing of the barrier andreaching neurons As a proof of this possibility transfection ofneuronal SH-SY5Y cells was achieved with the lipoplexes at adegree much higher than the degree obtained with the widelyand commonly utilized transfectant Lipofectamine cationic

ISRN Biochemistry 5

liposomes carrying a photoreactive drug resulted in a laser-stimulated cytotoxic effect on glioblastoma cells and showedthe ability to improve brain drug delivery of paclitaxel(a mitotic inhibitor used in cancer chemotherapy) in rodentsin vivo [31ndash33]

412 Solid Lipid Nanoparticles Solid lipid nanoparticles(SLN) are a stable lipid-based nanocarrier with a solidhydrophobic lipid core in which the drug can be dissolvedor dispersed [34] They are made with biocompatible lipidssuch as triglycerides fatty acids or waxes They are generallyof small size (around 40ndash200 nm) allowing them to crosstight endothelial cells of the BBB and escape from thereticuloendothelial system (RES) [35]

During their fabrication the melted lipid mixed withthe drug is commonly dispersed in an aqueous surfactantby high-pressure homogenization or microemulsificationThe advantages of SLN are their biocompatibility drugentrapment efficiency comparatively higher than other NPsand the ability to provide a continuous release of the drugfor several weeks [36] Moreover the composition of SLNcan be controlled modifying their surface properties to targetmolecules to the brain and to limit RES uptake [37]

Several reports are available describing an enhanced drugdelivery to the brain mediated by SLN For instance SLNcarrying a calcium channel blocker drug administered ivinto rodent showed that the drug was taken up to a greaterextent by the brain and maintained high drug levels for alonger time compared to free drug suspension

Wang et al have reported the synthesis of 310158405-dioctanoyl-5-fluoro-2-deoxyuridine (DO-FUdR) to overcome the lim-ited access of the drug 5-fluoro-2-deoxyuridine (FUdR) andits incorporation into SLN The results indicated that DO-FUdR-SLN had brain targeting efficiency in vivo of about 2-fold compared to free FUdR These authors report that SLNcan improve the ability of the drug to penetrate throughthe BBB and is a promising drug targeting system for thetreatment of central nervous system disorders [38 39]

42 Polymer-Based Nanoparticles

421 Polymeric Nanoparticles Polymeric NPs are composedof a core polymer matrix in which drugs can be embedded[40ndash42] with sizes usually between 60 and 200 nm A rangeof materials have been employed for delivery of drugs Inparticular in recent years some polymers have been designedprimarily for medical applications and have entered thearena of controlled release of bioactive agents Many ofthese materials are designed to degrade within the bodyMost popular ones are polylactides (PLA) polyglycolides(PGA) poly(lactide-co-glycolides) (PLGA) polyanhydridespolycyanoacrylates and polycaprolactone In spite of devel-opment of various synthetic and semi-synthetic polymersalso natural polymers such as chitosan can be utilized

Also in the case of polymeric NPs reports are avail-able describing an enhanced drug delivery to the brainmediated by these devices NPs made of PLGA embeddingantituberculosis drugs (rifampicin isoniazid pyrazinamide

and ethambutol) for cerebral drug deliverywere administeredto mice maintaining high drug levels for 5ndash8 days in plasmaand for 9 days in the brain much higher as comparedwith free drugs [43] InMycobacterium tuberculosis-infectedmice 5 doses of the NPs formulation (against 46 doses ofconventional free drugs) resulted in undetectable bacteriain the meninges [44] In another research [45] polybutyl-cyanoacrylate (PBCA) NPs were successfully utilized fordelivery of functional proteins into neurons and neuronal celllines

422 Polymeric Micelles Polymeric micelles are formedby amphiphilic copolymers whose aggregation in aqueousmedia leads to spheroidal structures with a hydrophilic shelland a hydrophobic core and with a good grade of stability[36] Stability can be improved by crosslinking between theshell or the core chains Additional tunable features of poly-meric micelles are the possibility to render them responsiveto external stimuli (pH light temperature ultrasound etc)[46] triggering a controllable release of entrapped drugsOne of the most utilized polymer is Pluronic type blockcopolymer based on ethylene oxide and propylene oxide

The possibility to use these NPs for brain drug deliv-ery has been described For instance chitosan-conjugatedPluronic nanocarriers with a specific target peptide forthe brain (rabies virus glycoprotein RVG29) following ivinjection in mice displayed in vivo brain accumulation eitherof a quantum dot fluorophore conjugated to the nanocarrieror of a protein loaded into the carrier [47] Other studieshave shown an increased central analgesic effect of micellar-vehicled drug [48]

423 Dendrimers Dendrimers are branched polymersreminding the structure of a tree A dendrimer is typicallysymmetric around the core and when sufficiently extended itoften adopts a spheroidal three-dimensional morphology inwater A central core can be recognized in their structure withat least two identical chemical functionalities starting fromthese groups repeated units of other molecules can originatehaving at least one junction of branching The repetitions ofchains and branching result in a series of radially concentriclayers with increased crowding The structure is thereforetightly packed in the periphery and loosely packed in thecore leaving spaces which play a key role in the drug-entrapping ability of dendrimers [49] Poly(amidoamine)or PAMAM is perhaps the most well-known molecule forsynthesis of dendrimers The core of PAMAM is a diamine(commonly ethylenediamine) which is reacted with methylacrylate and then with another ethylenediamine to makethe generation-0 PAMAM Successive reactions create highergenerations Albertazzi et al [50] showed that functionaliza-tion of PAMAMs dendrimers has a dramatic effect on theirability to diffuse in the CNS tissue in vivo and penetrate livingneurons as shown after intraparenchymal or intraventricularinjections

Kannan et al [51] showed that systemically administeredpolyamidoamine dendrimers localize in activated microgliaand astrocytes in the brain of newborn rabbits with cerebral

6 ISRN Biochemistry

palsy providing opportunities for clinical translation in thetreatment of neuroinflammatory disorders in humans

5 How NPs Can Cross the BBB

Many medicines are not able to reach the brain due to thelack of drug-specific transport systems through the BBBThedevelopment of new strategies based on NPs to enhance thebrain drug delivery is of great importance in the therapy anddiagnosis of CNS diseases and it is based on the interactionsbetween NPs and the BBB and on their intracellular trafficpathways

51 Crossing the BBB without Functionalization Althoughalmost all nanomaterials fall into the class of BBB imper-meable some exceptions have been reported in recent yearsFor instance gold and silica NPs have been shown to reachthe brain and accumulate in neurons even in the absenceof any specific functionalization with a mechanism thatsubstantially is still unknown In the case of silica the resultsindicated that NPs administered to rodents via intranasalinstillation entered into the brain and especially depositedin the striatum [52] In the case of gold NPs precise particledistribution in the brain was studied ex vivo by X-ray micro-tomography confocal laser andfluorescencemicroscopy [53]The authors found that the particles mainly accumulate inthe hippocampus thalamus hypothalamus and the cerebralcortex The same holds true for Titanium dioxide NPs thatwere found to cross the mice BBB particularly when smallerthan 40 nm [54]

52 Adsorptive-Mediated Transcytosis The concept of ad-sorptive-mediated transcytosis through the BBB was orig-inally suggested by the observation that cationic proteinscan bind the endothelial cell surface but also cross the BBB[55] The mechanism applied to NPs is based on the properfunctionalization of their surface allowing electrostatic inter-action with the luminal surface of BBB Given the presenceof negative charges on endothelial cells [56] this interactioncan be promoted by conferring a positive charge to the NPssurface

Different procedures can be followed to realize this issueA first possibility is to build up NPs made of componentsthat are bearing a positive charged at physiological pH (74)This is the case of nanosized vesiclesmade of bolaamphiphilicmolecules (amphiphilic molecules that have hydrophilicgroups at both ends of an hydrophobic chain) that followingintravenous administration to mice showed a marked accu-mulation of their encapsulated fluorescent cargo whereasnonencapsulated probe was detected only in peripheraltissues but not in the brain [57] In another investigation Jinet al [58] used SLN made with lipids extracted from depro-teinated lipoproteins and enriched with cationic cholesterylhydrochloride and phosphatidyl-ethanolamine The authorsafter intravenous administration of such cationic NPs for thedelivery of siRNA inhibiting c-Met expression suppressedtumor growth without evident signs of systemic toxicity inan orthotopic xenograft tumor mice model of glioblastoma

A second possibility is to functionalize the NPs surfacewith positively charged biomolecules combining their physic-ochemical features with biological activity This is the caseof cell-penetrating peptides (eg TAT peptides derived fromHIV gH625 derived from Herpes simplex virus type 1) andcationic proteins (eg albumin) [59] that have been exten-sively used for NPs decoration facilitating the BBB passageof drugs [60] As for example Rao et al [61] after admin-istration of ritonavir via TAT-conjugated NPs demonstratedapproximately an 800-fold higher level of drug in the brainwhen compared to that with free drug with a remarkableenhancement of drug delivery The authors suggested thatTAT-conjugated polymeric NPs are first mobilized in thebrain vasculatures then transported to the brain parenchymawhere they continue to release the drug

Polymeric micelles having TAT molecules on the surfacewere successfully fabricated also to incorporate antibioticsand were able to cross the BBB [62] In another study Xuet al [63] showed efficacy of TAT-polymeric NPs for thetreatment of C albicansmeningitis in rabbits Similar resultsare reported using another family of cell-penetrating peptides(SynB peptides RGGRLSYSRRRFSTSTGR) that were able toincrease drug permeability across a cocultured BBB modeldoubling drug transport in vivo in healthy mice [64]

Since the effect of cell-penetrating peptides could beinvalidated by the rapid systemic clearance of functionalizedNPs due to their positive charge in a study dedicated toinvestigate this issue Xia et al [65] utilized penetratin apeptide derived from Antennapedia protein (Drosophila)with relatively lower content of basic amino acids to func-tionalize poly(ethylene glycol)-poly(lactic acid) (PLGA)NPsfluorescently labeled with coumarin-6 and detected anincrease of fluorescence in the rodent brain with respect tounfunctionalized NPs

Xia et al [65] also combined the use of cell-penetratingpeptide to coumarin-6-loaded NPs for intranasal adminis-tration The amount of fluorescent probe detected in the ratcerebrum and cerebellum was found to be more than 2-foldcompared to that of coumarin carried by unfunctionalizedNPs Brain distribution analysis suggested that NPs afterintranasal administration could be delivered to the centralnervous system along both the olfactory and trigeminalnerves pathways

The efficacy of cationic albumin to functionalize andpromote NPs-carried drug delivery to the brain has beenrepeatedly reported [66 67]Theproperty of cationic proteinsto efficiently penetrate cells raises the question of the potentialtoxicity and immunogenicity of these proteins The possi-ble toxic effects include a generalized increase in vascularpermeability since breakdown of BBB permeability andother vascular beds has been observed following intravenousinjection of large amounts of cationic proteins but has notbeen seen when moderate amounts of these substances wereadministered [68]

53 Receptor-MediatedTranscytosis Oneof themost recentlyapplied strategies for drug delivery across the BBB endo-thelium using functionalized NPs is the one exploiting

ISRN Biochemistry 7

the transcytosis physiological mechanism of transport ofmacromolecules relying on the presence of specific recep-tors on the luminal surface of cells Transcytosis is theprocess by which extracellular cargo internalized at oneplasma membrane domain (eg apical) of a polarized cell istransported via vesicular intermediates to the controlateralplasma membrane (eg basolateral) As for example insulintransferrin apolipoproteins and 2-macroglobulin are someof the proteins that reach the brain following the path acrossendothelial cells

The rationale for exploiting this strategy with NPs is thatthe existing cellular mechanisms handling macromolecularcargoes may fit also to transport NPs after their functional-ization to interact with the same receptors

Transcytosis in endothelial cells starts with internal-ization of extracellular cargo into the cell by vesicularcarriers The cargo is subsequently processed via differentpathways to appropriate intracellular organelles and recycleddegraded or transcytosed to the contralateral side Strongmorphological and biochemical evidence suggest that thetwo membranes apical and basolateral are interconnectedvia vesicular intermediates involving multivesicular bodiesor a system of endosomal vacuoles and tubule vesiclesPhosphoinositide 3-kinase an enzyme increasingly demon-strated to play an important regulatory role inmany vesiculartrafficking events also appears to regulate transcytotic trafficbetween the two endosomal compartments

Transcytosis in endothelial cells starts with uptake eitherthrough clathrin-coated pits by caveolae or caveolae-likemembrane domains [69] that will be described here below

The first step of internalization through clathrin-mediated endocytosis is the binding of a ligand to a specificcell surface receptor This results in the clustering of theligand-receptor complexes in coated pits on the plasmamembrane which are formed by the assembly of cytosoliccoat proteins the main assembly units being clathrin whichform a polygonal lattice in the surface of the membrane andadaptor protein complexes which mediate the assembly ofthe clathrin lattice on the membrane The coated pits theninvaginate and pinch off from the plasma membrane to formintracellular clathrin-coated vesicles The clathrin coat thendepolymerizes resulting in early endosomes which fusewith each other or with other preexisting endosomes to formlate endosomes that further fuse with lysosomes Vesiculartrafficking after CME is controlled by the action of smallGTPases the Rab proteins

The second mechanisms internalization (caveolar) hasbeen clarified following the trafficking of some viruses thatuse caveolae to gain entry into the cells Caveolae aresmall flask-shaped invaginations of the plasma membranewith a size of about 50ndash60 nm that are rich in cholesteroland sphingolipids Viruses initially associate with the cellmembrane and then become trapped in relatively stationarycaveolae The subsequent intracellular uptake of caveolaeleads to intracellular organelles that are distinct from classicendosomes the presence of the protein caveolin in theseorganelles gave rise to the name caveosomes In contrast tothe dynamic nature of endosomes caveolae are highly stableand are only slowly internalized Another major difference is

that the caveolar uptake does not lead to a decrease of pHand to a degradative pathway of their cargo as in endoso-mallysosomal pathway

It is clear that the different pathways of NPs internal-ization affect their delivery to different intracellular com-partments and may affect their final destination To obtaininsight into the properties of drug delivery vehicles thatdirect their intracellular processing in brain endothelial cellsthe intracellular traffic of fixed-size nanoparticles in anin vitro BBB model as a function of distinct nanoparticlesurface modifications has been investigated Previous obser-vations [70] that latex particles with a diameter ge500 nm areinternalized by nonphagocytic B16 cells through caveolaewhereas particles up to 200 nm in diameter are efficientlytaken up via clathrin-mediated endocytosis were succes-sively confirmed with Silica-Hydroxyl NPs on immortalizedhuman brain capillary endothelial cell cultures [71] In theinvestigation of Georgieva et al [71] 500 nm particles wereused uncoated surface functionalized with cationic polymerpolyethyleneimine (PEI) or with prion protein The resultssuggested that uncoated NPs are internalized through cave-olae nanoparticles carrying a net cationic charge accom-plished by PEI followed an adsorptive endocytotic routeand particles surface-modified with prion protein followedreceptor-mediated endocytotic route Therefore the authorsconcluded that the NPs intracellular pathway is dictated bythe particle surface characteristic for a given size Mostinterestingly they found that the transcytotic potential ishigher for the receptor-mediated and caveolar pathways andlower for the adsorptive-mediated

However the enhancement of brain delivery obtainedwith drug-loaded NPs exploiting receptor- or caveolar-mediated transcytosis is currently quantitatively limited incomparison with the free drug Consequently also its clinicalrelevance is still scarce If we compare the hydrodynamicsize of most physiological proteins with that of NPs we areconfronting objects in the order of 5ndash10 nm size with thosethat in most cases are in the order of tenths of nanome-ters and commonly reach 100 nm and more Therefore itis conceivable that the transcytotic traffic may become abottleneck when transporting NPs It is also predictablethat smaller size NPs closer to the size of physiologicalmolecules would be facilitated to enter the same intracellu-lar transport pathways Following the strategy of receptor-mediated transport NPs made of gold PLGA chitosanPAA dendrimers and liposomes have been functionalizedimproving the delivery of drugs such as caspase inhibitorsendomorphin tamoxifen and tramadol and throwing thebasis for treatment of neurological diseases [72ndash79]

Exploring and targeting new receptors that could beutilized for receptor-dependent endocytosis are likely toprovide more efficient systems of brain drug delivery mainlybecause these uptakemechanisms are relatively unaffected bylysosomal degradation

531 Lipoprotein Receptors Apolipoprotein E (apoE) is a 34-kDa protein constituent of both very-low-density lipopro-tein (VLDL) and high-density lipoprotein (HDL) which

8 ISRN Biochemistry

transports cholesterol and other lipids in the plasma and inthe CNS [80 81] The lipoproteins complexes can be takenup in the brain through the recognition of apoE by specificreceptors at the BBB which include the low-density lipopro-tein receptor (LDLR) and the LDLR-related protein (LRP)

Taking into consideration that LRP has been reported tobe highly expressed on endothelial brain microvessels [82]receptor-mediated transcytosis using NPs functionalized tobind this target has been exploited in several ways

First by exploiting the preferential absorption of ApoEon some types of NPs when in serum This feature has beendescribed for PBCA NPs coated with polysorbate 80 indeeddisplaying the ability to cross the BBB in vivo in animalmodels [83ndash85] and for PEGylated PHDCA NPs able topenetrate into brain endothelial cells in vitro [86]

Taking advantage of such opportunity the formation ofa stable ApoE decoration of NPs surface by covalent bindinghas been utilized to functionalize albumin-NPs or liposomesthat showed the capacity of enhancing BBB passage in vivo inrodent models [87ndash89]

It should be questioned whether other apolipoproteinsmay be employed for NPs functionalization to confer onthem the ability to enhance brain drug delivery In order toanswer this question in an investigation of Kreuter et al [90]PBCA NPs loaded with dalargin or loperamide were coatedwith different apo-lipoproteins AII B CII E or J coatedor not with polysorbate 80 and then injected in mice andthe drug effect on CNS was evaluated The results showedthat only NPs coated with apolipoprotein B or E were able toachieve an antinociceptive effect This effect was significantlyhigher after polysorbate-precoating and apolipoprotein B orE-overcoating [90]

The region of apoE that is critical for interaction with theLDL receptor resides between amino acid residues 140 and160 Several studies with synthetic peptides have investigatedthe structural features of the LDLR-binding sequence ofApoE [91 92]

Laskowitz et al [81] derived an apoE-mimetic pep-tide from amino acids 133ndash149 named COG133 (LRVR-LASHLRKLRKRLL) which retains its biological activity invitro and in vivoThis capacity is displayed also by a fragmentof 26 aa from ApoE4 [93]

It has also been reported that the tandemdimer (141ndash155)2

is recognized by the LDLR in contrast to themonomeric pep-tide (141ndash155) [94] Also a shorter sequence of this peptide thetandem dimer (141ndash150)

2 retains this ability [95] Probably

as a consequence of these observations sterically stabilizedliposomeswere functionalized onlywithApoE tandemdimerpeptide (141ndash150)

2 but not with the monomer and were

shown to be efficiently taken up by rat brain capillaryendothelial cells [96] Interestingly in spite of the theoreticalpremises based on receptor-mediated endocytosis liposomestagged with (141ndash150)

2were nonselectively internalized into

cultured BBB cells and clathrin- or caveolin-dependentendocytosis was not demonstrable [97]

However in a successive investigation the ApoE-derivedpeptide monomer 141ndash150 was utilized by Re et al [98]in comparison with the dimer for the functionalization ofliposomes entrapping a radioactive derivative of curcumin

The investigation showed a higher uptake of the drug byhuman endothelial cells and an enhancement of permeabilityof the drug across an in vitromodel of the BBBmade with thesame cells when using monomer-functionalized liposomes

Apart from the amino acid sequence other factors mayaffect the cellular uptake of these peptides [98] These factorsinclude the type of peptide its cationic nature its mode ofexposure to the cell surface the nature of the cargo and thechemical linkage between the peptide and the cargo otherthan the peptide surface density on the cellular uptake ofnanoparticles [98 99]

Finally also Angiopep-2 a ligand of LRP possesses a highbrain penetration capability in both in vitro model of theBBB and in situ brain perfusion in mice [100] PEG-PAMAMdendrimers functionalized using this peptide resulted ina high accumulation of a delivered gene into brain afterintravenous administration into mice [101] moreover alsofunctionalized polymeric NPs and carbon nanotubes (CNT)have been produced showing the ability to reach gliomatumors in mice [102 103]

532 Transferrin Receptor (TfR) The transferrin receptor(TfR) is the most widely studied receptor for BBB targetingTfR is a transmembrane glycoprotein consisting of twolinked 90-kDa subunits each one binding a transferrinmolecule The receptor is highly expressed on immature ery-throid cells placental tissue and rapidly dividing cells bothnormal and malignant [104] Furthermore it is expressedon hepatocytes and endothelial cells of the BBB The role ofthe receptor is the regulation of cellular uptake of iron viatransferrin a plasma protein which transports iron in thecirculation Cellular uptake starts with the binding of trans-ferrin to the transferrin receptor followed by endocytosis[105]

Iron-bound transferrin has a high affinity for the TfRtherefore it has been used with success as a ligand for func-tionalization and targeting of liposomes to cultured brainendothelial cells [106 107] However it is likely that thatNPs decorated with transferrin would not be performantin vivo since transferrin receptors are almost saturated inphysiological conditions because of the high circulatinglevels of endogenous protein [108] Nevertheless successfulbrain targeting using transferrin as a targeting ligandhas beenaccomplished in vivo [109 110] Concerning the specificity oftransferrin a comparative study has been carried out betweentransferrin or lactoferrin a multifunctional protein of thetransferrin family widely represented in various secretoryfluids such as milk [111] Lalani et al [112] compared in vivodistribution in mice of PLGA NPs surface modified with thetwo proteins and showed a better performance to reach thebrain in the case of lactoferrin

In order to avoid the competition with endogenous trans-ferrin circulating in blood the use of monoclonal antibodies(mAbs) directed against transferrin receptors on the BBB hasbeen suggested because they recognize different epitopes onthe receptor [113] For instance OX26 8D3 and R17217 mAbbind to TfR and have also been shown to undergo receptor-mediated transcytosis

ISRN Biochemistry 9

Among these it is still debated which mAb is the bestperforming to be used for the decoration of NPs surface Themostwell known isOX26 an antibody directed against the ratTfR that has been successfully used in many brain targetingstudies in vivo [114] and also in vitro using BBB cellularmodels [115] However Lee et al [116] have shown that theOX26monoclonal antibody is not an effective brain targetingmolecule in mice Moreover they demonstrated that othertwo monoclonal antibodies 8D3 and RI7217 directed againstthe mouse TfR had a higher permeability of the mouseBBB in vivo with respect to the brain uptake of the OX26antibody which was negligible Additionally they showedthat RI7217wasmore selective for the brain than 8D3 becausethis antibody was less taken up by the liver and kidney Ithas been shown that RI7217 covalently coupled to humanserum albumin is able to transport loperamide across theBBB [110] More recently it has been shown that also thechemical linkage of anti-TfR on the NPs surface could affectthe crossing of BBB in vitro [117] The authors comparedliposomes covalently coupled with mAbs (obtained by react-ing thiolatedmAbs to phosphatidyl-ethanolaminemaleimideinserted in the liposome bilayer) with liposomes decoratedwith biotinylated mAbs via an avidin bridge The Authorsfound an higher cellular uptake and permeability across anin vitro BBB model made of immortalized human braincapillary endothelial cells of the liposomes covalently coupledwith mAbs suggesting that the covalent ligation could bepreferentially chosen for NPs decoration

54 Retrograde Transport Transsynaptic retrograde trans-port could enable some types of nanocarriers to travel fromperipheral nerve terminals to neuronal cell bodies in the CNS[118] Studies in this regard have shown that NPs modifiedwith PEI and other polyplexes display active retrogradetransport along neurites but are unable to mediate efficientbiological actions upon reaching the neuronal body [119]

55 BBB Breakdown BBB breakdown occurs in neuroin-flammatory diseases [120] NPs can transiently and reversiblyopen the tight junctions located at the BBB and other sitesthus increasing their paracellular permeability [121 122]In particular blood-brain barrier disruption therapy is anintensive effectiveway of sendingmedication to brain tumors[123]

Nevertheless it is known that tight junctions can beopened only to a limited extent [124] thus only NPs smallerthan about 20 nm can use this pathway to penetrate into thebrain through the BBB

56 Exploiting MonocyteMacrophage Infiltration in the CNSMonocytemacrophage infiltration in the CNS plays a keyrole in neuroinflammation as well as in lesion developmentand brain injury in neurological diseases such as multiplesclerosis (MS) and stroke [124ndash126] Knowledge of activephases of cell infiltration during CNS disorders is importantbecause anti-inflammatory treatments can target cell adhe-sion molecules and chemokines guiding cellular trafficking[127] The monocyte infiltration through the BBB is also

widely believed to play an important role in HIV infectionof the CNS The blood-brain barrier appears unaltered untilthe late stage of HIV encephalitis HIV flux that movestoward the brain thus relies on hijacking with immune-activated leukocytes mainly monocytesmacrophages fromthe periphery [128]

In this paper BBB crossing by immune-activated macro-phages appears to suggest possible strategies for future ther-apeutic developments employing NPs This strategy couldbe realized at least in two ways (1) by embedding NPs intoactivated monocytes used as Trojan horses to reach the brain(2) by designing NPs mimicking activated monocytes

561 Trojan Monocytes for NPs Delivery to the Brain Nano-particulate drug delivery systems have been used to avoidthe RES clearance and achieve longer circulation time forenhanced tissue uptake However the enhancing of NPsphagocytosis by monocytes can be considered as an uncon-ventional approach to deliver NPs-loaded drugs to thebrain After phagocytosis of NPs monocytes just like Trojanhorses may transport their cargo into the brain Aferganet al [129] taking this approach embedded serotonin aBBB impermeable neurological drug into negatively chargedliposomes and analyzed brain uptake in rats and rabbitsThe performance of liposomal serotonin was significantlybetter leading to two-fold higher drug concentration inbrain than the free drug Since treatment of animals byalendronate resulted with inhibition of monocytes but not ofneutrophils andwith no brain delivery the authors suggestedthat monocytes are the main transporters of liposomes tothe brain In spite of the fact that the clinical relevance ofthis investigation is limited the Trojan monocyte approachprovides a new possibility of more effective treatment ofbrain-associated inflammatory disorders including multiplesclerosis and Alzheimerrsquos disease which are characterizedwith increased passage of immune cells across the BBB[130]

In other examples in order to improve the delivery ofcontrast agents to the brain iron oxide NPs administeredintravenously in vivo have been shown to detect activatedmacrophage infiltration in multiple sclerosis either in theCNS of humans [131 132] or rodentmodel [133ndash137] in strokeeither in human [138 139] or animal brain ischemia [140ndash143] in human or murine intracranial tumors [144 145] inEAE [146ndash148] or in an ischemiareperfusion long-lived ratmodel [149]

562 NPs Mimicking Activated Monocytes The therapeu-tic efficacy of drug-loaded NPs systemically administereddepends on their ability to evade the immune system tocross the biological barriers of the body and to localizeat target tissues Parodi et al [150] show that nanoporoussilicon particles can successfully perform all these actionswhen they are coated with cellular membranes purifiedfrom leukocytes avoiding being cleared by the immune sys-tem Furthermore they can communicate with endothelialcells through receptor-ligand interactions and transport andrelease a doxorubicin payload across an inflamed endothelial

10 ISRN Biochemistry

barrier in vitro Also the accumulation of coated NPs inmice inoculated with murine B16 melanoma was enhancedcompared with that of non coated NPs Particle coatingusing leukocyte membranes led to an approximately twofoldincrease in particle density in the tumor

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsit is predictable that the research of NPs mimicking immunecells might be effective in brain-associated disorders and willreceive a stimulus in this direction in the next years

6 Factors Affecting NPs Brain Drug Delivery

61 NPs Diffusion inside the Brain Parenchyma While thisfactor is likely not particularly relevant when brain drugdelivery is sought after it could be very important when thepassage of the BBBbyNPs is looked for since the extracellularspace (ECS) of the brain parenchyma could limit their diffu-sion or even preclude their entrance into the brainThe abilityto achieve brain penetration with larger NPs is expected toallow more uniform longer lasting and effective delivery ofdrugs within the brain and may in particular find practicein the treatment of brain tumors stroke neuroinflammationand other brain diseases where the BBB is compromised orwhere local delivery strategies are feasible

Today it is well established that the ECSoccupies a volumefraction of between 15 and 30 in normal adult brain tissuewith a typical value of 20 and that this falls to 5 duringglobal ischemia [151 152]

It is less obvious what the true size of the spaces betweencells is Small molecules such as inulin and sucrose diffusethrough the ECS with a decreased diffusion coefficient withrespect to water suggesting the existence of limitation to theirmovements [153]

Possible sources of the limitations to the diffusing mol-ecules are (a) the presence of cellular obstructions (b) trap-ping of molecules in dead-space microdomains (c) a viscousdrag imposed by themacromolecules that compose the extra-cellular matrix or drag arising from the walls of the channelswhen molecules are large such as in the case of NPs(d) transient binding to cell membranes or extracellularmatrix (e) nonspecific interaction with negative charges onthe extracellular matrix when the diffusing molecule hasadequate charge density

A different type of model was proposed by Thorne andNicholson [154] to explain the higher tortuosity experimen-tally measured for larger substances such as dextran andespecially large synthetic quantum dot nanocrystals in the invivo rat cortex It was assumed that the quantum dots with ahydrodynamic diameter of 35 nm were close to the averagewidth of the ECS and depending on whether a planar ortubularmodel was adopted the estimated ECSwidth was 38ndash64 nm

In counter tendency to Thorne and Nicholson [154]Nance et al [155] report that NPs as large as 114 nm indiameter diffused within the human and rat brain only ifthey were densely coated with PEG Using these minimally

adhesive PEG-coated NPs they estimated that human braintissue ECS has some pores larger than 200 nm and that morethan one-quarter of all pores are ge100 nm

In addition to ECS in CNS there is also much interest inthe possibility that perivascular spaces fluid-filled channelssurrounding arteries arterioles veins venules and possiblyevenmicrovessels offer potential pathways for rapid flow intoand out of brain parenchyma Measurements of perivascularspace widths in mammals suggest that their typical dimen-sions may be at least 2 orders of magnitude greater thanthe neocortical ECS width (eg arteriole perivascular spaceshave been reported in the range of 5ndash10 120583m or larger (inrodents and humans))

62 Effect of Protein Corona Different physicochemicalproperties not only size may determine the ability ofnanoparticles to reach the brain The situation is furthercomplicated by the formation of a so-called ldquocoronardquo ofbiomolecules on the surfaces of nanoparticles the composi-tion of which may vary depending on the route of exposureand on the physicochemical surface properties of NPs Theacquisition of a corona of biomolecules on the surface ofNPs may also determine whether NPs are able to cross fromone compartment to another and whether they are taken upeffectively by cells or not [156]

In practical situations in which nanoparticles interactwith living organisms the nanoparticle surfaces are initiallyexposed to a biological fluid such as blood dependingon the route of administration For instance NPs injectedintravenously would be exposed to blood plasma containingan excess of proteins and many other complex biomoleculeswhich bind competitively with the surface of the nanoparti-cles

The current idea is that ldquobarerdquo nanoparticles do notexist in vivo because they are immediately modified bythe adsorption of blood proteins with higher affinities forthe particle surface forming a more or less tightly boundlayer (the so-called hard corona) and a weakly associatedmobile layer (the so-called soft corona) When this issue wasinvestigated it has been found that typical coronas containa limited number and types of molecules gathered fromthe blood in spite of the fact that biological fluids containthousands of proteins [157] Moreover it should be noted thatthe corona may also play a role in other undesirable effectsof NPs in living systems such as complement activation andblood clotting and may not necessarily play a role only incellular uptake

It should be pointed out that none of the in vitro exper-iments conducted to study the process of NPs translocationto the brain takes into account the surface modification ofNPs inside the blood and how can this affect the crossingof the BBB This issue needs much further investigationMoreover NPs once internalized by endothelial BBB cellsthey may also exit towards the brain covered with differentbiomolecules depending on that they have undergone endo-cytosistranscytosisexocytosis and thus exert additionaleffects (eg toxicity) on neuron Also this issue has not yetbeen investigated

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

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[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

[12] W M Pardridge ldquoDrug transport across the blood-brainbarrierrdquo Journal of Cerebral Blood Flow amp Metabolism vol 32no 11 pp 1959ndash1972 2012

[13] A Minn S Leclerc J M Heydel et al ldquoDrug transport into themammalian brain the nasal pathway and its specific metabolicbarrierrdquo Journal of Drug Targeting vol 10 no 4 pp 285rndash296r2002

[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

[23] L Martin-Banderas M A Holgado J L Venero J Alvarez-Fuentes and M Fernadez-Arealo ldquoNanostructures for drugdelivery to the brainrdquoCurrentMedicinal Chemistry vol 148 no34 pp 5303ndash5321 2011

[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

[26] T Ishii T Asai D Oyama et al ldquoTreatment of cerebralischemia-reperfusion injury with PEGylated liposomes encap-sulating FK506rdquo FASEB Journal vol 27 no 4 pp 1362ndash13702013

[27] A Lindqvist J Rip P J Gaillard S Bjorkman and MHammarlund-Udenaes ldquoEnhanced brain delivery of the opioidpeptide DAMGO in glutathione PEGylated liposomes amicro-dialysis studyrdquoMolecular Pharmacology 2012

[28] A Orthmann R Zeisig R Suss D Lorenz M Lemm andI Fichtner ldquoTreatment of experimental brain metastasis withMTO-liposomes impact of fluidity and LRP-targeting on thetherapeutic resultrdquo Pharmaceutical Research vol 29 no 7 pp1949ndash1959 2012

[29] M T da Cruz S Simoes and M C de Lima ldquoImprovinglipoplex-mediated gene transfer into C6 glioma cells andprimary neuronsrdquo Experimental Neurology vol 187 no 1 pp65ndash75 2004

[30] F Artzner R Zantl and J O Radler ldquoLipid-DNA and lipid-polyelectrolyte mesophases structure and exchange kineticsrdquoCellular andMolecular Biology vol 46 no 5 pp 967ndash978 2000

[31] A Molinari M Colone A Calcabrini et al ldquoCationic lipo-somes loaded with m-THPC in photodynamic therapy for

14 ISRN Biochemistry

malignant gliomardquo Toxicology in Vitro vol 21 no 2 pp 230ndash234 2007

[32] Y Obata G Ciofani V Raffa et al ldquoEvaluation of cationicliposomes composed of an amino acid-based lipid for neuronaltransfectionrdquo Nanomedicine vol 6 no 1 pp e70ndashe77 2010

[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

[36] B Mishra B B Patel and S Tiwari ldquoColloidal nanocarriersa review on formulation technology types and applicationstoward targeted drug deliveryrdquo Nanomedicine vol 6 no 1 ppe9ndashe24 2010

[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

[40] S Md M Ali S Baboota et al ldquoPreparation characteri-zation in vivo biodistribution and pharmacokinetic studiesof donepezil-loaded PLGA nanoparticles for brain targetingrdquoDrug Development and Industrial Pharmacy 2013

[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

[43] Y E Choonara V Pillay V M K Ndesendo et al ldquoPoly-meric emulsion and crosslink-mediated synthesis of super-stable nanoparticles as sustained-release anti-tuberculosis drugcarriersrdquoColloids and Surfaces B vol 87 no 2 pp 243ndash254 2011

[44] R Pandey and G K Khuller ldquoOral nanoparticle-based antitu-berculosis drug delivery to the brain in an experimental modelrdquoJournal of Antimicrobial Chemotherapy vol 57 no 6 pp 1146ndash1152 2006

[45] L Hasadsri J Kreuter H Hattori T Iwasaki and J M GeorgeldquoFunctional protein delivery into neurons using polymericnanoparticlesrdquo Journal of Biological Chemistry vol 284 no 11pp 6972ndash6981 2009

[46] A V Kabanov E V Batrakova N S Melik-Nubarov et alldquoA new class of drug carriers micelles of poly(oxyethylene)-poly(oxypropylene) block copolymers as microcontainers for

drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

[50] L Albertazzi L Gherardini M Brondi et al ldquoIn vivo dis-tribution and toxicity of PAMAM dendrimers in the centralnervous system depend on their surface chemistryrdquo MolecularPharmacology vol 10 no 1 pp 249ndash260 2013

[51] S Kannan H Dai R S Navath et al ldquoDendrimer-basedpostnatal therapy for neuroinflammation and cerebral palsy ina rabbit modelrdquo Science Translational Medicine vol 4 no 130Article ID 130ra46 2012

[52] J Wu C Wang J Sun and Y Xue ldquoNeurotoxicity of silicananoparticles brain localization and dopaminergic neuronsdamage pathwaysrdquoACSNano vol 5 no 6 pp 4476ndash4489 2011

[53] F Sousa S Mandal C Garrovo et al ldquoFunctionalized goldnanoparticles a detailed in vivo multimodal microscopic braindistribution studyrdquo Nanoscale vol 2 no 12 pp 2826ndash28342010

[54] Y Ze L Zheng X Zhao et al ldquoMolecular mechanism oftitanium dioxide nanoparticles-induced oxidative injury in thebrain of micerdquo Chemosphere 2013

[55] R D Broadwell ldquoTranscytosis of macromolecules through theblood-brain barrier a cell biological perspective and criticalappraisalrdquo Acta Neuropathologica vol 79 no 2 pp 117ndash1281989

[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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ISRN Biochemistry 3

Liposomes Solid lipid nanoparticle Non-polymeric micelles

Lipoplex

+

+ +

+

+

+

+

++

+

+

+

Dendrimers Polymeric nanoparticle

Polymeric micelle Nanotubes Silica nanoparticle

Quantum dots Gold nanoparticle Magnetic nanoparticle

Figure 1 Different types of nanoparticles (NPs) Graphical representation of the most commonly used NPs for biomedical applications NPsare typically by a size measuring not more than 100 nm and have significant potential for delivering drugs across the blood-brain barrier Thesize of quantum dots is usually less than 10 nm

These proteins substantially change the bare material proper-ties determining the removal of NPs from circulation by thereticuloendothelial systemmainly located in spleen and liverThe most common approaches used for escaping RES are toformulate the particles with neutral surface charge to coat

their surface with different hydrophilic surfactants such aspolysorbates and polyethylene glycol (PEG) and to use smallsize nanoparticles (eglt80 nm) [19] NPswith these featurescalled ldquostealthrdquo are able to avoid the reticuloendothelialsystem to display long circulation time and stability in blood

4 ISRN Biochemistry

and may be functionalized to successfully target and crossthe BBB [20] Finally NPs should be nontoxic either forcells in the bloodstream or for healthy bystanding cells andshould be biodegradable and biocompatible noninflamma-tory and nonimmunogenic [21] The possibilities of func-tionalization of MP for brain drug delivery are depicted inFigure 2

It is also important to point out that the tailoring ofNPs toenhance drug delivery to the brain does not necessarily implytheir ability to cross the BBB themselves It is predictable thatNPs could play this role at least in two ways

(i) by increasing the drug concentration inside or atthe luminal surface of BBB cells establishing a localhigh concentration gradient between blood an brainhigher than that obtainable after systemic administra-tion of the free drug The gradient should then favorthe enhanced passive diffusion of the drug As forexample this task could be realized by synthesizingNPs functionalized to target brain capillary endothe-lial cells This feature can be followed or not by theirsubsequent uptake from targeted cells [22]

(ii) by moving themselves into the CNS together withtheir drug cargo As for example this task can berealized enabling NPs targeting of brain capillaryendothelial cells and their subsequent transcellularpassage across the BBB [23]

For the completeness of this review in the next section themain features ofNPs commonly utilized formedical purposesand already utilized or promising candidates for brain drugdelivery will be described

4 Nanoparticles for Medical Applications

41 Lipid-Based Nanoparticles

411 Liposomes Liposomes are the first generation ofnanoparticulate drug delivery systems [24] and are consti-tuted by one or more vesicular bilayers (lamellae) composedof amphiphilic lipids delimiting an internal aqueous com-partment Usually the liposomal lipid bilayer is composedof biocompatible and biodegradable lipids present in bio-logical membranes Common liposome constituents are sph-ingomyelin phosphatidylcholine and glycerophospholipidsCholesterol an important component of cell membranesis frequently included in liposome formulations because itdecreases the bilayer permeability and increases the stabilityof the liposome in vivo Liposomes are classified on thebase of their size and the number of lamellae as follows (i)small unilamellar vesicles (SUV) with a size up to 100 nmand one bilayer (ii) large unilamellar vesicles (LUV) with asize gt100 nm and one bilayer and (iii) multilamellar vesicles(MLV) that can reach a size of several 120583m and made of manyconcentric lipid bilayers

Liposomes have been largely utilized for brain drugdelivery (for a review see [25]) for the treatment of cerebral

+ +++

++

Targetingantibody

Fluorescentprobe

Targetingaptamer

Drug payload

Cationicmolecules

Targetingpeptide

DrugPEGspacer

Figure 2 Multifunctionalized nanoparticles (NPs) Graphical rep-resentation of surface-modified NPs with drugs (incorporatedwithin the core of NPs or conjugated to the surface) targetingmolecules (antibodies peptides aptamers and cationic molecules)for brain drug delivery with PEG for stealthiness and with fluores-cent probe as a tracer

ischemia [26] for delivery of opioid peptides [27] and braintumours [28]

Cationic Liposomes Cationic liposomes containing positivelycharged lipids have been developed and initially used astransfection vehicles to deliver genetic material (eg DNA)into the cell avoiding the lysosomal digestion The mostcommonly utilized cationic lipid is 12-dioleoyl-3-trimethyl-ammonium-propane (DOTAP) mixed with dioleoyl-phos-phatidylethanolamine (DOPE)The cholesterol also increasesthe levels of transfection and can potentially reduce thedestabilization of the liposomes in the presence of serum [29]

The interactions between cationic lipids and nucleicacids lead to the formation of structures which are calledldquolipoplexesrdquo [30] Lipoplexes are typically formed by directmixing between cationic liposomes and DNA solutionsPositively charged liposomes bind to negatively chargedphosphate molecules on the DNA backbone through electro-static interactions that are embedded and are shielded fromthe environment Generally complexes are formed with aslight excess positive charge to permit them to interact withthe negatively charged cell surface The cationic liposomesused are typically small before adding to DNA howevercomplexes formed with DNA exhibit diameters that rangefrom as small as 200 nm to structures as large as 2120583m Unlikeliposomes cationic liposomes undergo adsorptive-mediatedendocytosis and internalization in endosomes Upon acid-ification at pH 5 to 6 DOPE fuses and destabilizes theendosomal membrane releasing its contents to the cytosolTherefore drugs could be vehicled into endothelial cellssimilarly to DNA enhancing their crossing of the barrier andreaching neurons As a proof of this possibility transfection ofneuronal SH-SY5Y cells was achieved with the lipoplexes at adegree much higher than the degree obtained with the widelyand commonly utilized transfectant Lipofectamine cationic

ISRN Biochemistry 5

liposomes carrying a photoreactive drug resulted in a laser-stimulated cytotoxic effect on glioblastoma cells and showedthe ability to improve brain drug delivery of paclitaxel(a mitotic inhibitor used in cancer chemotherapy) in rodentsin vivo [31ndash33]

412 Solid Lipid Nanoparticles Solid lipid nanoparticles(SLN) are a stable lipid-based nanocarrier with a solidhydrophobic lipid core in which the drug can be dissolvedor dispersed [34] They are made with biocompatible lipidssuch as triglycerides fatty acids or waxes They are generallyof small size (around 40ndash200 nm) allowing them to crosstight endothelial cells of the BBB and escape from thereticuloendothelial system (RES) [35]

During their fabrication the melted lipid mixed withthe drug is commonly dispersed in an aqueous surfactantby high-pressure homogenization or microemulsificationThe advantages of SLN are their biocompatibility drugentrapment efficiency comparatively higher than other NPsand the ability to provide a continuous release of the drugfor several weeks [36] Moreover the composition of SLNcan be controlled modifying their surface properties to targetmolecules to the brain and to limit RES uptake [37]

Several reports are available describing an enhanced drugdelivery to the brain mediated by SLN For instance SLNcarrying a calcium channel blocker drug administered ivinto rodent showed that the drug was taken up to a greaterextent by the brain and maintained high drug levels for alonger time compared to free drug suspension

Wang et al have reported the synthesis of 310158405-dioctanoyl-5-fluoro-2-deoxyuridine (DO-FUdR) to overcome the lim-ited access of the drug 5-fluoro-2-deoxyuridine (FUdR) andits incorporation into SLN The results indicated that DO-FUdR-SLN had brain targeting efficiency in vivo of about 2-fold compared to free FUdR These authors report that SLNcan improve the ability of the drug to penetrate throughthe BBB and is a promising drug targeting system for thetreatment of central nervous system disorders [38 39]

42 Polymer-Based Nanoparticles

421 Polymeric Nanoparticles Polymeric NPs are composedof a core polymer matrix in which drugs can be embedded[40ndash42] with sizes usually between 60 and 200 nm A rangeof materials have been employed for delivery of drugs Inparticular in recent years some polymers have been designedprimarily for medical applications and have entered thearena of controlled release of bioactive agents Many ofthese materials are designed to degrade within the bodyMost popular ones are polylactides (PLA) polyglycolides(PGA) poly(lactide-co-glycolides) (PLGA) polyanhydridespolycyanoacrylates and polycaprolactone In spite of devel-opment of various synthetic and semi-synthetic polymersalso natural polymers such as chitosan can be utilized

Also in the case of polymeric NPs reports are avail-able describing an enhanced drug delivery to the brainmediated by these devices NPs made of PLGA embeddingantituberculosis drugs (rifampicin isoniazid pyrazinamide

and ethambutol) for cerebral drug deliverywere administeredto mice maintaining high drug levels for 5ndash8 days in plasmaand for 9 days in the brain much higher as comparedwith free drugs [43] InMycobacterium tuberculosis-infectedmice 5 doses of the NPs formulation (against 46 doses ofconventional free drugs) resulted in undetectable bacteriain the meninges [44] In another research [45] polybutyl-cyanoacrylate (PBCA) NPs were successfully utilized fordelivery of functional proteins into neurons and neuronal celllines

422 Polymeric Micelles Polymeric micelles are formedby amphiphilic copolymers whose aggregation in aqueousmedia leads to spheroidal structures with a hydrophilic shelland a hydrophobic core and with a good grade of stability[36] Stability can be improved by crosslinking between theshell or the core chains Additional tunable features of poly-meric micelles are the possibility to render them responsiveto external stimuli (pH light temperature ultrasound etc)[46] triggering a controllable release of entrapped drugsOne of the most utilized polymer is Pluronic type blockcopolymer based on ethylene oxide and propylene oxide

The possibility to use these NPs for brain drug deliv-ery has been described For instance chitosan-conjugatedPluronic nanocarriers with a specific target peptide forthe brain (rabies virus glycoprotein RVG29) following ivinjection in mice displayed in vivo brain accumulation eitherof a quantum dot fluorophore conjugated to the nanocarrieror of a protein loaded into the carrier [47] Other studieshave shown an increased central analgesic effect of micellar-vehicled drug [48]

423 Dendrimers Dendrimers are branched polymersreminding the structure of a tree A dendrimer is typicallysymmetric around the core and when sufficiently extended itoften adopts a spheroidal three-dimensional morphology inwater A central core can be recognized in their structure withat least two identical chemical functionalities starting fromthese groups repeated units of other molecules can originatehaving at least one junction of branching The repetitions ofchains and branching result in a series of radially concentriclayers with increased crowding The structure is thereforetightly packed in the periphery and loosely packed in thecore leaving spaces which play a key role in the drug-entrapping ability of dendrimers [49] Poly(amidoamine)or PAMAM is perhaps the most well-known molecule forsynthesis of dendrimers The core of PAMAM is a diamine(commonly ethylenediamine) which is reacted with methylacrylate and then with another ethylenediamine to makethe generation-0 PAMAM Successive reactions create highergenerations Albertazzi et al [50] showed that functionaliza-tion of PAMAMs dendrimers has a dramatic effect on theirability to diffuse in the CNS tissue in vivo and penetrate livingneurons as shown after intraparenchymal or intraventricularinjections

Kannan et al [51] showed that systemically administeredpolyamidoamine dendrimers localize in activated microgliaand astrocytes in the brain of newborn rabbits with cerebral

6 ISRN Biochemistry

palsy providing opportunities for clinical translation in thetreatment of neuroinflammatory disorders in humans

5 How NPs Can Cross the BBB

Many medicines are not able to reach the brain due to thelack of drug-specific transport systems through the BBBThedevelopment of new strategies based on NPs to enhance thebrain drug delivery is of great importance in the therapy anddiagnosis of CNS diseases and it is based on the interactionsbetween NPs and the BBB and on their intracellular trafficpathways

51 Crossing the BBB without Functionalization Althoughalmost all nanomaterials fall into the class of BBB imper-meable some exceptions have been reported in recent yearsFor instance gold and silica NPs have been shown to reachthe brain and accumulate in neurons even in the absenceof any specific functionalization with a mechanism thatsubstantially is still unknown In the case of silica the resultsindicated that NPs administered to rodents via intranasalinstillation entered into the brain and especially depositedin the striatum [52] In the case of gold NPs precise particledistribution in the brain was studied ex vivo by X-ray micro-tomography confocal laser andfluorescencemicroscopy [53]The authors found that the particles mainly accumulate inthe hippocampus thalamus hypothalamus and the cerebralcortex The same holds true for Titanium dioxide NPs thatwere found to cross the mice BBB particularly when smallerthan 40 nm [54]

52 Adsorptive-Mediated Transcytosis The concept of ad-sorptive-mediated transcytosis through the BBB was orig-inally suggested by the observation that cationic proteinscan bind the endothelial cell surface but also cross the BBB[55] The mechanism applied to NPs is based on the properfunctionalization of their surface allowing electrostatic inter-action with the luminal surface of BBB Given the presenceof negative charges on endothelial cells [56] this interactioncan be promoted by conferring a positive charge to the NPssurface

Different procedures can be followed to realize this issueA first possibility is to build up NPs made of componentsthat are bearing a positive charged at physiological pH (74)This is the case of nanosized vesiclesmade of bolaamphiphilicmolecules (amphiphilic molecules that have hydrophilicgroups at both ends of an hydrophobic chain) that followingintravenous administration to mice showed a marked accu-mulation of their encapsulated fluorescent cargo whereasnonencapsulated probe was detected only in peripheraltissues but not in the brain [57] In another investigation Jinet al [58] used SLN made with lipids extracted from depro-teinated lipoproteins and enriched with cationic cholesterylhydrochloride and phosphatidyl-ethanolamine The authorsafter intravenous administration of such cationic NPs for thedelivery of siRNA inhibiting c-Met expression suppressedtumor growth without evident signs of systemic toxicity inan orthotopic xenograft tumor mice model of glioblastoma

A second possibility is to functionalize the NPs surfacewith positively charged biomolecules combining their physic-ochemical features with biological activity This is the caseof cell-penetrating peptides (eg TAT peptides derived fromHIV gH625 derived from Herpes simplex virus type 1) andcationic proteins (eg albumin) [59] that have been exten-sively used for NPs decoration facilitating the BBB passageof drugs [60] As for example Rao et al [61] after admin-istration of ritonavir via TAT-conjugated NPs demonstratedapproximately an 800-fold higher level of drug in the brainwhen compared to that with free drug with a remarkableenhancement of drug delivery The authors suggested thatTAT-conjugated polymeric NPs are first mobilized in thebrain vasculatures then transported to the brain parenchymawhere they continue to release the drug

Polymeric micelles having TAT molecules on the surfacewere successfully fabricated also to incorporate antibioticsand were able to cross the BBB [62] In another study Xuet al [63] showed efficacy of TAT-polymeric NPs for thetreatment of C albicansmeningitis in rabbits Similar resultsare reported using another family of cell-penetrating peptides(SynB peptides RGGRLSYSRRRFSTSTGR) that were able toincrease drug permeability across a cocultured BBB modeldoubling drug transport in vivo in healthy mice [64]

Since the effect of cell-penetrating peptides could beinvalidated by the rapid systemic clearance of functionalizedNPs due to their positive charge in a study dedicated toinvestigate this issue Xia et al [65] utilized penetratin apeptide derived from Antennapedia protein (Drosophila)with relatively lower content of basic amino acids to func-tionalize poly(ethylene glycol)-poly(lactic acid) (PLGA)NPsfluorescently labeled with coumarin-6 and detected anincrease of fluorescence in the rodent brain with respect tounfunctionalized NPs

Xia et al [65] also combined the use of cell-penetratingpeptide to coumarin-6-loaded NPs for intranasal adminis-tration The amount of fluorescent probe detected in the ratcerebrum and cerebellum was found to be more than 2-foldcompared to that of coumarin carried by unfunctionalizedNPs Brain distribution analysis suggested that NPs afterintranasal administration could be delivered to the centralnervous system along both the olfactory and trigeminalnerves pathways

The efficacy of cationic albumin to functionalize andpromote NPs-carried drug delivery to the brain has beenrepeatedly reported [66 67]Theproperty of cationic proteinsto efficiently penetrate cells raises the question of the potentialtoxicity and immunogenicity of these proteins The possi-ble toxic effects include a generalized increase in vascularpermeability since breakdown of BBB permeability andother vascular beds has been observed following intravenousinjection of large amounts of cationic proteins but has notbeen seen when moderate amounts of these substances wereadministered [68]

53 Receptor-MediatedTranscytosis Oneof themost recentlyapplied strategies for drug delivery across the BBB endo-thelium using functionalized NPs is the one exploiting

ISRN Biochemistry 7

the transcytosis physiological mechanism of transport ofmacromolecules relying on the presence of specific recep-tors on the luminal surface of cells Transcytosis is theprocess by which extracellular cargo internalized at oneplasma membrane domain (eg apical) of a polarized cell istransported via vesicular intermediates to the controlateralplasma membrane (eg basolateral) As for example insulintransferrin apolipoproteins and 2-macroglobulin are someof the proteins that reach the brain following the path acrossendothelial cells

The rationale for exploiting this strategy with NPs is thatthe existing cellular mechanisms handling macromolecularcargoes may fit also to transport NPs after their functional-ization to interact with the same receptors

Transcytosis in endothelial cells starts with internal-ization of extracellular cargo into the cell by vesicularcarriers The cargo is subsequently processed via differentpathways to appropriate intracellular organelles and recycleddegraded or transcytosed to the contralateral side Strongmorphological and biochemical evidence suggest that thetwo membranes apical and basolateral are interconnectedvia vesicular intermediates involving multivesicular bodiesor a system of endosomal vacuoles and tubule vesiclesPhosphoinositide 3-kinase an enzyme increasingly demon-strated to play an important regulatory role inmany vesiculartrafficking events also appears to regulate transcytotic trafficbetween the two endosomal compartments

Transcytosis in endothelial cells starts with uptake eitherthrough clathrin-coated pits by caveolae or caveolae-likemembrane domains [69] that will be described here below

The first step of internalization through clathrin-mediated endocytosis is the binding of a ligand to a specificcell surface receptor This results in the clustering of theligand-receptor complexes in coated pits on the plasmamembrane which are formed by the assembly of cytosoliccoat proteins the main assembly units being clathrin whichform a polygonal lattice in the surface of the membrane andadaptor protein complexes which mediate the assembly ofthe clathrin lattice on the membrane The coated pits theninvaginate and pinch off from the plasma membrane to formintracellular clathrin-coated vesicles The clathrin coat thendepolymerizes resulting in early endosomes which fusewith each other or with other preexisting endosomes to formlate endosomes that further fuse with lysosomes Vesiculartrafficking after CME is controlled by the action of smallGTPases the Rab proteins

The second mechanisms internalization (caveolar) hasbeen clarified following the trafficking of some viruses thatuse caveolae to gain entry into the cells Caveolae aresmall flask-shaped invaginations of the plasma membranewith a size of about 50ndash60 nm that are rich in cholesteroland sphingolipids Viruses initially associate with the cellmembrane and then become trapped in relatively stationarycaveolae The subsequent intracellular uptake of caveolaeleads to intracellular organelles that are distinct from classicendosomes the presence of the protein caveolin in theseorganelles gave rise to the name caveosomes In contrast tothe dynamic nature of endosomes caveolae are highly stableand are only slowly internalized Another major difference is

that the caveolar uptake does not lead to a decrease of pHand to a degradative pathway of their cargo as in endoso-mallysosomal pathway

It is clear that the different pathways of NPs internal-ization affect their delivery to different intracellular com-partments and may affect their final destination To obtaininsight into the properties of drug delivery vehicles thatdirect their intracellular processing in brain endothelial cellsthe intracellular traffic of fixed-size nanoparticles in anin vitro BBB model as a function of distinct nanoparticlesurface modifications has been investigated Previous obser-vations [70] that latex particles with a diameter ge500 nm areinternalized by nonphagocytic B16 cells through caveolaewhereas particles up to 200 nm in diameter are efficientlytaken up via clathrin-mediated endocytosis were succes-sively confirmed with Silica-Hydroxyl NPs on immortalizedhuman brain capillary endothelial cell cultures [71] In theinvestigation of Georgieva et al [71] 500 nm particles wereused uncoated surface functionalized with cationic polymerpolyethyleneimine (PEI) or with prion protein The resultssuggested that uncoated NPs are internalized through cave-olae nanoparticles carrying a net cationic charge accom-plished by PEI followed an adsorptive endocytotic routeand particles surface-modified with prion protein followedreceptor-mediated endocytotic route Therefore the authorsconcluded that the NPs intracellular pathway is dictated bythe particle surface characteristic for a given size Mostinterestingly they found that the transcytotic potential ishigher for the receptor-mediated and caveolar pathways andlower for the adsorptive-mediated

However the enhancement of brain delivery obtainedwith drug-loaded NPs exploiting receptor- or caveolar-mediated transcytosis is currently quantitatively limited incomparison with the free drug Consequently also its clinicalrelevance is still scarce If we compare the hydrodynamicsize of most physiological proteins with that of NPs we areconfronting objects in the order of 5ndash10 nm size with thosethat in most cases are in the order of tenths of nanome-ters and commonly reach 100 nm and more Therefore itis conceivable that the transcytotic traffic may become abottleneck when transporting NPs It is also predictablethat smaller size NPs closer to the size of physiologicalmolecules would be facilitated to enter the same intracellu-lar transport pathways Following the strategy of receptor-mediated transport NPs made of gold PLGA chitosanPAA dendrimers and liposomes have been functionalizedimproving the delivery of drugs such as caspase inhibitorsendomorphin tamoxifen and tramadol and throwing thebasis for treatment of neurological diseases [72ndash79]

Exploring and targeting new receptors that could beutilized for receptor-dependent endocytosis are likely toprovide more efficient systems of brain drug delivery mainlybecause these uptakemechanisms are relatively unaffected bylysosomal degradation

531 Lipoprotein Receptors Apolipoprotein E (apoE) is a 34-kDa protein constituent of both very-low-density lipopro-tein (VLDL) and high-density lipoprotein (HDL) which

8 ISRN Biochemistry

transports cholesterol and other lipids in the plasma and inthe CNS [80 81] The lipoproteins complexes can be takenup in the brain through the recognition of apoE by specificreceptors at the BBB which include the low-density lipopro-tein receptor (LDLR) and the LDLR-related protein (LRP)

Taking into consideration that LRP has been reported tobe highly expressed on endothelial brain microvessels [82]receptor-mediated transcytosis using NPs functionalized tobind this target has been exploited in several ways

First by exploiting the preferential absorption of ApoEon some types of NPs when in serum This feature has beendescribed for PBCA NPs coated with polysorbate 80 indeeddisplaying the ability to cross the BBB in vivo in animalmodels [83ndash85] and for PEGylated PHDCA NPs able topenetrate into brain endothelial cells in vitro [86]

Taking advantage of such opportunity the formation ofa stable ApoE decoration of NPs surface by covalent bindinghas been utilized to functionalize albumin-NPs or liposomesthat showed the capacity of enhancing BBB passage in vivo inrodent models [87ndash89]

It should be questioned whether other apolipoproteinsmay be employed for NPs functionalization to confer onthem the ability to enhance brain drug delivery In order toanswer this question in an investigation of Kreuter et al [90]PBCA NPs loaded with dalargin or loperamide were coatedwith different apo-lipoproteins AII B CII E or J coatedor not with polysorbate 80 and then injected in mice andthe drug effect on CNS was evaluated The results showedthat only NPs coated with apolipoprotein B or E were able toachieve an antinociceptive effect This effect was significantlyhigher after polysorbate-precoating and apolipoprotein B orE-overcoating [90]

The region of apoE that is critical for interaction with theLDL receptor resides between amino acid residues 140 and160 Several studies with synthetic peptides have investigatedthe structural features of the LDLR-binding sequence ofApoE [91 92]

Laskowitz et al [81] derived an apoE-mimetic pep-tide from amino acids 133ndash149 named COG133 (LRVR-LASHLRKLRKRLL) which retains its biological activity invitro and in vivoThis capacity is displayed also by a fragmentof 26 aa from ApoE4 [93]

It has also been reported that the tandemdimer (141ndash155)2

is recognized by the LDLR in contrast to themonomeric pep-tide (141ndash155) [94] Also a shorter sequence of this peptide thetandem dimer (141ndash150)

2 retains this ability [95] Probably

as a consequence of these observations sterically stabilizedliposomeswere functionalized onlywithApoE tandemdimerpeptide (141ndash150)

2 but not with the monomer and were

shown to be efficiently taken up by rat brain capillaryendothelial cells [96] Interestingly in spite of the theoreticalpremises based on receptor-mediated endocytosis liposomestagged with (141ndash150)

2were nonselectively internalized into

cultured BBB cells and clathrin- or caveolin-dependentendocytosis was not demonstrable [97]

However in a successive investigation the ApoE-derivedpeptide monomer 141ndash150 was utilized by Re et al [98]in comparison with the dimer for the functionalization ofliposomes entrapping a radioactive derivative of curcumin

The investigation showed a higher uptake of the drug byhuman endothelial cells and an enhancement of permeabilityof the drug across an in vitromodel of the BBBmade with thesame cells when using monomer-functionalized liposomes

Apart from the amino acid sequence other factors mayaffect the cellular uptake of these peptides [98] These factorsinclude the type of peptide its cationic nature its mode ofexposure to the cell surface the nature of the cargo and thechemical linkage between the peptide and the cargo otherthan the peptide surface density on the cellular uptake ofnanoparticles [98 99]

Finally also Angiopep-2 a ligand of LRP possesses a highbrain penetration capability in both in vitro model of theBBB and in situ brain perfusion in mice [100] PEG-PAMAMdendrimers functionalized using this peptide resulted ina high accumulation of a delivered gene into brain afterintravenous administration into mice [101] moreover alsofunctionalized polymeric NPs and carbon nanotubes (CNT)have been produced showing the ability to reach gliomatumors in mice [102 103]

532 Transferrin Receptor (TfR) The transferrin receptor(TfR) is the most widely studied receptor for BBB targetingTfR is a transmembrane glycoprotein consisting of twolinked 90-kDa subunits each one binding a transferrinmolecule The receptor is highly expressed on immature ery-throid cells placental tissue and rapidly dividing cells bothnormal and malignant [104] Furthermore it is expressedon hepatocytes and endothelial cells of the BBB The role ofthe receptor is the regulation of cellular uptake of iron viatransferrin a plasma protein which transports iron in thecirculation Cellular uptake starts with the binding of trans-ferrin to the transferrin receptor followed by endocytosis[105]

Iron-bound transferrin has a high affinity for the TfRtherefore it has been used with success as a ligand for func-tionalization and targeting of liposomes to cultured brainendothelial cells [106 107] However it is likely that thatNPs decorated with transferrin would not be performantin vivo since transferrin receptors are almost saturated inphysiological conditions because of the high circulatinglevels of endogenous protein [108] Nevertheless successfulbrain targeting using transferrin as a targeting ligandhas beenaccomplished in vivo [109 110] Concerning the specificity oftransferrin a comparative study has been carried out betweentransferrin or lactoferrin a multifunctional protein of thetransferrin family widely represented in various secretoryfluids such as milk [111] Lalani et al [112] compared in vivodistribution in mice of PLGA NPs surface modified with thetwo proteins and showed a better performance to reach thebrain in the case of lactoferrin

In order to avoid the competition with endogenous trans-ferrin circulating in blood the use of monoclonal antibodies(mAbs) directed against transferrin receptors on the BBB hasbeen suggested because they recognize different epitopes onthe receptor [113] For instance OX26 8D3 and R17217 mAbbind to TfR and have also been shown to undergo receptor-mediated transcytosis

ISRN Biochemistry 9

Among these it is still debated which mAb is the bestperforming to be used for the decoration of NPs surface Themostwell known isOX26 an antibody directed against the ratTfR that has been successfully used in many brain targetingstudies in vivo [114] and also in vitro using BBB cellularmodels [115] However Lee et al [116] have shown that theOX26monoclonal antibody is not an effective brain targetingmolecule in mice Moreover they demonstrated that othertwo monoclonal antibodies 8D3 and RI7217 directed againstthe mouse TfR had a higher permeability of the mouseBBB in vivo with respect to the brain uptake of the OX26antibody which was negligible Additionally they showedthat RI7217wasmore selective for the brain than 8D3 becausethis antibody was less taken up by the liver and kidney Ithas been shown that RI7217 covalently coupled to humanserum albumin is able to transport loperamide across theBBB [110] More recently it has been shown that also thechemical linkage of anti-TfR on the NPs surface could affectthe crossing of BBB in vitro [117] The authors comparedliposomes covalently coupled with mAbs (obtained by react-ing thiolatedmAbs to phosphatidyl-ethanolaminemaleimideinserted in the liposome bilayer) with liposomes decoratedwith biotinylated mAbs via an avidin bridge The Authorsfound an higher cellular uptake and permeability across anin vitro BBB model made of immortalized human braincapillary endothelial cells of the liposomes covalently coupledwith mAbs suggesting that the covalent ligation could bepreferentially chosen for NPs decoration

54 Retrograde Transport Transsynaptic retrograde trans-port could enable some types of nanocarriers to travel fromperipheral nerve terminals to neuronal cell bodies in the CNS[118] Studies in this regard have shown that NPs modifiedwith PEI and other polyplexes display active retrogradetransport along neurites but are unable to mediate efficientbiological actions upon reaching the neuronal body [119]

55 BBB Breakdown BBB breakdown occurs in neuroin-flammatory diseases [120] NPs can transiently and reversiblyopen the tight junctions located at the BBB and other sitesthus increasing their paracellular permeability [121 122]In particular blood-brain barrier disruption therapy is anintensive effectiveway of sendingmedication to brain tumors[123]

Nevertheless it is known that tight junctions can beopened only to a limited extent [124] thus only NPs smallerthan about 20 nm can use this pathway to penetrate into thebrain through the BBB

56 Exploiting MonocyteMacrophage Infiltration in the CNSMonocytemacrophage infiltration in the CNS plays a keyrole in neuroinflammation as well as in lesion developmentand brain injury in neurological diseases such as multiplesclerosis (MS) and stroke [124ndash126] Knowledge of activephases of cell infiltration during CNS disorders is importantbecause anti-inflammatory treatments can target cell adhe-sion molecules and chemokines guiding cellular trafficking[127] The monocyte infiltration through the BBB is also

widely believed to play an important role in HIV infectionof the CNS The blood-brain barrier appears unaltered untilthe late stage of HIV encephalitis HIV flux that movestoward the brain thus relies on hijacking with immune-activated leukocytes mainly monocytesmacrophages fromthe periphery [128]

In this paper BBB crossing by immune-activated macro-phages appears to suggest possible strategies for future ther-apeutic developments employing NPs This strategy couldbe realized at least in two ways (1) by embedding NPs intoactivated monocytes used as Trojan horses to reach the brain(2) by designing NPs mimicking activated monocytes

561 Trojan Monocytes for NPs Delivery to the Brain Nano-particulate drug delivery systems have been used to avoidthe RES clearance and achieve longer circulation time forenhanced tissue uptake However the enhancing of NPsphagocytosis by monocytes can be considered as an uncon-ventional approach to deliver NPs-loaded drugs to thebrain After phagocytosis of NPs monocytes just like Trojanhorses may transport their cargo into the brain Aferganet al [129] taking this approach embedded serotonin aBBB impermeable neurological drug into negatively chargedliposomes and analyzed brain uptake in rats and rabbitsThe performance of liposomal serotonin was significantlybetter leading to two-fold higher drug concentration inbrain than the free drug Since treatment of animals byalendronate resulted with inhibition of monocytes but not ofneutrophils andwith no brain delivery the authors suggestedthat monocytes are the main transporters of liposomes tothe brain In spite of the fact that the clinical relevance ofthis investigation is limited the Trojan monocyte approachprovides a new possibility of more effective treatment ofbrain-associated inflammatory disorders including multiplesclerosis and Alzheimerrsquos disease which are characterizedwith increased passage of immune cells across the BBB[130]

In other examples in order to improve the delivery ofcontrast agents to the brain iron oxide NPs administeredintravenously in vivo have been shown to detect activatedmacrophage infiltration in multiple sclerosis either in theCNS of humans [131 132] or rodentmodel [133ndash137] in strokeeither in human [138 139] or animal brain ischemia [140ndash143] in human or murine intracranial tumors [144 145] inEAE [146ndash148] or in an ischemiareperfusion long-lived ratmodel [149]

562 NPs Mimicking Activated Monocytes The therapeu-tic efficacy of drug-loaded NPs systemically administereddepends on their ability to evade the immune system tocross the biological barriers of the body and to localizeat target tissues Parodi et al [150] show that nanoporoussilicon particles can successfully perform all these actionswhen they are coated with cellular membranes purifiedfrom leukocytes avoiding being cleared by the immune sys-tem Furthermore they can communicate with endothelialcells through receptor-ligand interactions and transport andrelease a doxorubicin payload across an inflamed endothelial

10 ISRN Biochemistry

barrier in vitro Also the accumulation of coated NPs inmice inoculated with murine B16 melanoma was enhancedcompared with that of non coated NPs Particle coatingusing leukocyte membranes led to an approximately twofoldincrease in particle density in the tumor

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsit is predictable that the research of NPs mimicking immunecells might be effective in brain-associated disorders and willreceive a stimulus in this direction in the next years

6 Factors Affecting NPs Brain Drug Delivery

61 NPs Diffusion inside the Brain Parenchyma While thisfactor is likely not particularly relevant when brain drugdelivery is sought after it could be very important when thepassage of the BBBbyNPs is looked for since the extracellularspace (ECS) of the brain parenchyma could limit their diffu-sion or even preclude their entrance into the brainThe abilityto achieve brain penetration with larger NPs is expected toallow more uniform longer lasting and effective delivery ofdrugs within the brain and may in particular find practicein the treatment of brain tumors stroke neuroinflammationand other brain diseases where the BBB is compromised orwhere local delivery strategies are feasible

Today it is well established that the ECSoccupies a volumefraction of between 15 and 30 in normal adult brain tissuewith a typical value of 20 and that this falls to 5 duringglobal ischemia [151 152]

It is less obvious what the true size of the spaces betweencells is Small molecules such as inulin and sucrose diffusethrough the ECS with a decreased diffusion coefficient withrespect to water suggesting the existence of limitation to theirmovements [153]

Possible sources of the limitations to the diffusing mol-ecules are (a) the presence of cellular obstructions (b) trap-ping of molecules in dead-space microdomains (c) a viscousdrag imposed by themacromolecules that compose the extra-cellular matrix or drag arising from the walls of the channelswhen molecules are large such as in the case of NPs(d) transient binding to cell membranes or extracellularmatrix (e) nonspecific interaction with negative charges onthe extracellular matrix when the diffusing molecule hasadequate charge density

A different type of model was proposed by Thorne andNicholson [154] to explain the higher tortuosity experimen-tally measured for larger substances such as dextran andespecially large synthetic quantum dot nanocrystals in the invivo rat cortex It was assumed that the quantum dots with ahydrodynamic diameter of 35 nm were close to the averagewidth of the ECS and depending on whether a planar ortubularmodel was adopted the estimated ECSwidth was 38ndash64 nm

In counter tendency to Thorne and Nicholson [154]Nance et al [155] report that NPs as large as 114 nm indiameter diffused within the human and rat brain only ifthey were densely coated with PEG Using these minimally

adhesive PEG-coated NPs they estimated that human braintissue ECS has some pores larger than 200 nm and that morethan one-quarter of all pores are ge100 nm

In addition to ECS in CNS there is also much interest inthe possibility that perivascular spaces fluid-filled channelssurrounding arteries arterioles veins venules and possiblyevenmicrovessels offer potential pathways for rapid flow intoand out of brain parenchyma Measurements of perivascularspace widths in mammals suggest that their typical dimen-sions may be at least 2 orders of magnitude greater thanthe neocortical ECS width (eg arteriole perivascular spaceshave been reported in the range of 5ndash10 120583m or larger (inrodents and humans))

62 Effect of Protein Corona Different physicochemicalproperties not only size may determine the ability ofnanoparticles to reach the brain The situation is furthercomplicated by the formation of a so-called ldquocoronardquo ofbiomolecules on the surfaces of nanoparticles the composi-tion of which may vary depending on the route of exposureand on the physicochemical surface properties of NPs Theacquisition of a corona of biomolecules on the surface ofNPs may also determine whether NPs are able to cross fromone compartment to another and whether they are taken upeffectively by cells or not [156]

In practical situations in which nanoparticles interactwith living organisms the nanoparticle surfaces are initiallyexposed to a biological fluid such as blood dependingon the route of administration For instance NPs injectedintravenously would be exposed to blood plasma containingan excess of proteins and many other complex biomoleculeswhich bind competitively with the surface of the nanoparti-cles

The current idea is that ldquobarerdquo nanoparticles do notexist in vivo because they are immediately modified bythe adsorption of blood proteins with higher affinities forthe particle surface forming a more or less tightly boundlayer (the so-called hard corona) and a weakly associatedmobile layer (the so-called soft corona) When this issue wasinvestigated it has been found that typical coronas containa limited number and types of molecules gathered fromthe blood in spite of the fact that biological fluids containthousands of proteins [157] Moreover it should be noted thatthe corona may also play a role in other undesirable effectsof NPs in living systems such as complement activation andblood clotting and may not necessarily play a role only incellular uptake

It should be pointed out that none of the in vitro exper-iments conducted to study the process of NPs translocationto the brain takes into account the surface modification ofNPs inside the blood and how can this affect the crossingof the BBB This issue needs much further investigationMoreover NPs once internalized by endothelial BBB cellsthey may also exit towards the brain covered with differentbiomolecules depending on that they have undergone endo-cytosistranscytosisexocytosis and thus exert additionaleffects (eg toxicity) on neuron Also this issue has not yetbeen investigated

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

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[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

[12] W M Pardridge ldquoDrug transport across the blood-brainbarrierrdquo Journal of Cerebral Blood Flow amp Metabolism vol 32no 11 pp 1959ndash1972 2012

[13] A Minn S Leclerc J M Heydel et al ldquoDrug transport into themammalian brain the nasal pathway and its specific metabolicbarrierrdquo Journal of Drug Targeting vol 10 no 4 pp 285rndash296r2002

[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

[23] L Martin-Banderas M A Holgado J L Venero J Alvarez-Fuentes and M Fernadez-Arealo ldquoNanostructures for drugdelivery to the brainrdquoCurrentMedicinal Chemistry vol 148 no34 pp 5303ndash5321 2011

[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

[26] T Ishii T Asai D Oyama et al ldquoTreatment of cerebralischemia-reperfusion injury with PEGylated liposomes encap-sulating FK506rdquo FASEB Journal vol 27 no 4 pp 1362ndash13702013

[27] A Lindqvist J Rip P J Gaillard S Bjorkman and MHammarlund-Udenaes ldquoEnhanced brain delivery of the opioidpeptide DAMGO in glutathione PEGylated liposomes amicro-dialysis studyrdquoMolecular Pharmacology 2012

[28] A Orthmann R Zeisig R Suss D Lorenz M Lemm andI Fichtner ldquoTreatment of experimental brain metastasis withMTO-liposomes impact of fluidity and LRP-targeting on thetherapeutic resultrdquo Pharmaceutical Research vol 29 no 7 pp1949ndash1959 2012

[29] M T da Cruz S Simoes and M C de Lima ldquoImprovinglipoplex-mediated gene transfer into C6 glioma cells andprimary neuronsrdquo Experimental Neurology vol 187 no 1 pp65ndash75 2004

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[31] A Molinari M Colone A Calcabrini et al ldquoCationic lipo-somes loaded with m-THPC in photodynamic therapy for

14 ISRN Biochemistry

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[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

[36] B Mishra B B Patel and S Tiwari ldquoColloidal nanocarriersa review on formulation technology types and applicationstoward targeted drug deliveryrdquo Nanomedicine vol 6 no 1 ppe9ndashe24 2010

[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

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[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

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[46] A V Kabanov E V Batrakova N S Melik-Nubarov et alldquoA new class of drug carriers micelles of poly(oxyethylene)-poly(oxypropylene) block copolymers as microcontainers for

drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

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[52] J Wu C Wang J Sun and Y Xue ldquoNeurotoxicity of silicananoparticles brain localization and dopaminergic neuronsdamage pathwaysrdquoACSNano vol 5 no 6 pp 4476ndash4489 2011

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[54] Y Ze L Zheng X Zhao et al ldquoMolecular mechanism oftitanium dioxide nanoparticles-induced oxidative injury in thebrain of micerdquo Chemosphere 2013

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[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

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Molecular Biology International

GenomicsInternational Journal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

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Signal TransductionJournal of

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BioMed Research International

Evolutionary BiologyInternational Journal of

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Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Advances in

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Enzyme Research

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International Journal of

Microbiology

4 ISRN Biochemistry

and may be functionalized to successfully target and crossthe BBB [20] Finally NPs should be nontoxic either forcells in the bloodstream or for healthy bystanding cells andshould be biodegradable and biocompatible noninflamma-tory and nonimmunogenic [21] The possibilities of func-tionalization of MP for brain drug delivery are depicted inFigure 2

It is also important to point out that the tailoring ofNPs toenhance drug delivery to the brain does not necessarily implytheir ability to cross the BBB themselves It is predictable thatNPs could play this role at least in two ways

(i) by increasing the drug concentration inside or atthe luminal surface of BBB cells establishing a localhigh concentration gradient between blood an brainhigher than that obtainable after systemic administra-tion of the free drug The gradient should then favorthe enhanced passive diffusion of the drug As forexample this task could be realized by synthesizingNPs functionalized to target brain capillary endothe-lial cells This feature can be followed or not by theirsubsequent uptake from targeted cells [22]

(ii) by moving themselves into the CNS together withtheir drug cargo As for example this task can berealized enabling NPs targeting of brain capillaryendothelial cells and their subsequent transcellularpassage across the BBB [23]

For the completeness of this review in the next section themain features ofNPs commonly utilized formedical purposesand already utilized or promising candidates for brain drugdelivery will be described

4 Nanoparticles for Medical Applications

41 Lipid-Based Nanoparticles

411 Liposomes Liposomes are the first generation ofnanoparticulate drug delivery systems [24] and are consti-tuted by one or more vesicular bilayers (lamellae) composedof amphiphilic lipids delimiting an internal aqueous com-partment Usually the liposomal lipid bilayer is composedof biocompatible and biodegradable lipids present in bio-logical membranes Common liposome constituents are sph-ingomyelin phosphatidylcholine and glycerophospholipidsCholesterol an important component of cell membranesis frequently included in liposome formulations because itdecreases the bilayer permeability and increases the stabilityof the liposome in vivo Liposomes are classified on thebase of their size and the number of lamellae as follows (i)small unilamellar vesicles (SUV) with a size up to 100 nmand one bilayer (ii) large unilamellar vesicles (LUV) with asize gt100 nm and one bilayer and (iii) multilamellar vesicles(MLV) that can reach a size of several 120583m and made of manyconcentric lipid bilayers

Liposomes have been largely utilized for brain drugdelivery (for a review see [25]) for the treatment of cerebral

+ +++

++

Targetingantibody

Fluorescentprobe

Targetingaptamer

Drug payload

Cationicmolecules

Targetingpeptide

DrugPEGspacer

Figure 2 Multifunctionalized nanoparticles (NPs) Graphical rep-resentation of surface-modified NPs with drugs (incorporatedwithin the core of NPs or conjugated to the surface) targetingmolecules (antibodies peptides aptamers and cationic molecules)for brain drug delivery with PEG for stealthiness and with fluores-cent probe as a tracer

ischemia [26] for delivery of opioid peptides [27] and braintumours [28]

Cationic Liposomes Cationic liposomes containing positivelycharged lipids have been developed and initially used astransfection vehicles to deliver genetic material (eg DNA)into the cell avoiding the lysosomal digestion The mostcommonly utilized cationic lipid is 12-dioleoyl-3-trimethyl-ammonium-propane (DOTAP) mixed with dioleoyl-phos-phatidylethanolamine (DOPE)The cholesterol also increasesthe levels of transfection and can potentially reduce thedestabilization of the liposomes in the presence of serum [29]

The interactions between cationic lipids and nucleicacids lead to the formation of structures which are calledldquolipoplexesrdquo [30] Lipoplexes are typically formed by directmixing between cationic liposomes and DNA solutionsPositively charged liposomes bind to negatively chargedphosphate molecules on the DNA backbone through electro-static interactions that are embedded and are shielded fromthe environment Generally complexes are formed with aslight excess positive charge to permit them to interact withthe negatively charged cell surface The cationic liposomesused are typically small before adding to DNA howevercomplexes formed with DNA exhibit diameters that rangefrom as small as 200 nm to structures as large as 2120583m Unlikeliposomes cationic liposomes undergo adsorptive-mediatedendocytosis and internalization in endosomes Upon acid-ification at pH 5 to 6 DOPE fuses and destabilizes theendosomal membrane releasing its contents to the cytosolTherefore drugs could be vehicled into endothelial cellssimilarly to DNA enhancing their crossing of the barrier andreaching neurons As a proof of this possibility transfection ofneuronal SH-SY5Y cells was achieved with the lipoplexes at adegree much higher than the degree obtained with the widelyand commonly utilized transfectant Lipofectamine cationic

ISRN Biochemistry 5

liposomes carrying a photoreactive drug resulted in a laser-stimulated cytotoxic effect on glioblastoma cells and showedthe ability to improve brain drug delivery of paclitaxel(a mitotic inhibitor used in cancer chemotherapy) in rodentsin vivo [31ndash33]

412 Solid Lipid Nanoparticles Solid lipid nanoparticles(SLN) are a stable lipid-based nanocarrier with a solidhydrophobic lipid core in which the drug can be dissolvedor dispersed [34] They are made with biocompatible lipidssuch as triglycerides fatty acids or waxes They are generallyof small size (around 40ndash200 nm) allowing them to crosstight endothelial cells of the BBB and escape from thereticuloendothelial system (RES) [35]

During their fabrication the melted lipid mixed withthe drug is commonly dispersed in an aqueous surfactantby high-pressure homogenization or microemulsificationThe advantages of SLN are their biocompatibility drugentrapment efficiency comparatively higher than other NPsand the ability to provide a continuous release of the drugfor several weeks [36] Moreover the composition of SLNcan be controlled modifying their surface properties to targetmolecules to the brain and to limit RES uptake [37]

Several reports are available describing an enhanced drugdelivery to the brain mediated by SLN For instance SLNcarrying a calcium channel blocker drug administered ivinto rodent showed that the drug was taken up to a greaterextent by the brain and maintained high drug levels for alonger time compared to free drug suspension

Wang et al have reported the synthesis of 310158405-dioctanoyl-5-fluoro-2-deoxyuridine (DO-FUdR) to overcome the lim-ited access of the drug 5-fluoro-2-deoxyuridine (FUdR) andits incorporation into SLN The results indicated that DO-FUdR-SLN had brain targeting efficiency in vivo of about 2-fold compared to free FUdR These authors report that SLNcan improve the ability of the drug to penetrate throughthe BBB and is a promising drug targeting system for thetreatment of central nervous system disorders [38 39]

42 Polymer-Based Nanoparticles

421 Polymeric Nanoparticles Polymeric NPs are composedof a core polymer matrix in which drugs can be embedded[40ndash42] with sizes usually between 60 and 200 nm A rangeof materials have been employed for delivery of drugs Inparticular in recent years some polymers have been designedprimarily for medical applications and have entered thearena of controlled release of bioactive agents Many ofthese materials are designed to degrade within the bodyMost popular ones are polylactides (PLA) polyglycolides(PGA) poly(lactide-co-glycolides) (PLGA) polyanhydridespolycyanoacrylates and polycaprolactone In spite of devel-opment of various synthetic and semi-synthetic polymersalso natural polymers such as chitosan can be utilized

Also in the case of polymeric NPs reports are avail-able describing an enhanced drug delivery to the brainmediated by these devices NPs made of PLGA embeddingantituberculosis drugs (rifampicin isoniazid pyrazinamide

and ethambutol) for cerebral drug deliverywere administeredto mice maintaining high drug levels for 5ndash8 days in plasmaand for 9 days in the brain much higher as comparedwith free drugs [43] InMycobacterium tuberculosis-infectedmice 5 doses of the NPs formulation (against 46 doses ofconventional free drugs) resulted in undetectable bacteriain the meninges [44] In another research [45] polybutyl-cyanoacrylate (PBCA) NPs were successfully utilized fordelivery of functional proteins into neurons and neuronal celllines

422 Polymeric Micelles Polymeric micelles are formedby amphiphilic copolymers whose aggregation in aqueousmedia leads to spheroidal structures with a hydrophilic shelland a hydrophobic core and with a good grade of stability[36] Stability can be improved by crosslinking between theshell or the core chains Additional tunable features of poly-meric micelles are the possibility to render them responsiveto external stimuli (pH light temperature ultrasound etc)[46] triggering a controllable release of entrapped drugsOne of the most utilized polymer is Pluronic type blockcopolymer based on ethylene oxide and propylene oxide

The possibility to use these NPs for brain drug deliv-ery has been described For instance chitosan-conjugatedPluronic nanocarriers with a specific target peptide forthe brain (rabies virus glycoprotein RVG29) following ivinjection in mice displayed in vivo brain accumulation eitherof a quantum dot fluorophore conjugated to the nanocarrieror of a protein loaded into the carrier [47] Other studieshave shown an increased central analgesic effect of micellar-vehicled drug [48]

423 Dendrimers Dendrimers are branched polymersreminding the structure of a tree A dendrimer is typicallysymmetric around the core and when sufficiently extended itoften adopts a spheroidal three-dimensional morphology inwater A central core can be recognized in their structure withat least two identical chemical functionalities starting fromthese groups repeated units of other molecules can originatehaving at least one junction of branching The repetitions ofchains and branching result in a series of radially concentriclayers with increased crowding The structure is thereforetightly packed in the periphery and loosely packed in thecore leaving spaces which play a key role in the drug-entrapping ability of dendrimers [49] Poly(amidoamine)or PAMAM is perhaps the most well-known molecule forsynthesis of dendrimers The core of PAMAM is a diamine(commonly ethylenediamine) which is reacted with methylacrylate and then with another ethylenediamine to makethe generation-0 PAMAM Successive reactions create highergenerations Albertazzi et al [50] showed that functionaliza-tion of PAMAMs dendrimers has a dramatic effect on theirability to diffuse in the CNS tissue in vivo and penetrate livingneurons as shown after intraparenchymal or intraventricularinjections

Kannan et al [51] showed that systemically administeredpolyamidoamine dendrimers localize in activated microgliaand astrocytes in the brain of newborn rabbits with cerebral

6 ISRN Biochemistry

palsy providing opportunities for clinical translation in thetreatment of neuroinflammatory disorders in humans

5 How NPs Can Cross the BBB

Many medicines are not able to reach the brain due to thelack of drug-specific transport systems through the BBBThedevelopment of new strategies based on NPs to enhance thebrain drug delivery is of great importance in the therapy anddiagnosis of CNS diseases and it is based on the interactionsbetween NPs and the BBB and on their intracellular trafficpathways

51 Crossing the BBB without Functionalization Althoughalmost all nanomaterials fall into the class of BBB imper-meable some exceptions have been reported in recent yearsFor instance gold and silica NPs have been shown to reachthe brain and accumulate in neurons even in the absenceof any specific functionalization with a mechanism thatsubstantially is still unknown In the case of silica the resultsindicated that NPs administered to rodents via intranasalinstillation entered into the brain and especially depositedin the striatum [52] In the case of gold NPs precise particledistribution in the brain was studied ex vivo by X-ray micro-tomography confocal laser andfluorescencemicroscopy [53]The authors found that the particles mainly accumulate inthe hippocampus thalamus hypothalamus and the cerebralcortex The same holds true for Titanium dioxide NPs thatwere found to cross the mice BBB particularly when smallerthan 40 nm [54]

52 Adsorptive-Mediated Transcytosis The concept of ad-sorptive-mediated transcytosis through the BBB was orig-inally suggested by the observation that cationic proteinscan bind the endothelial cell surface but also cross the BBB[55] The mechanism applied to NPs is based on the properfunctionalization of their surface allowing electrostatic inter-action with the luminal surface of BBB Given the presenceof negative charges on endothelial cells [56] this interactioncan be promoted by conferring a positive charge to the NPssurface

Different procedures can be followed to realize this issueA first possibility is to build up NPs made of componentsthat are bearing a positive charged at physiological pH (74)This is the case of nanosized vesiclesmade of bolaamphiphilicmolecules (amphiphilic molecules that have hydrophilicgroups at both ends of an hydrophobic chain) that followingintravenous administration to mice showed a marked accu-mulation of their encapsulated fluorescent cargo whereasnonencapsulated probe was detected only in peripheraltissues but not in the brain [57] In another investigation Jinet al [58] used SLN made with lipids extracted from depro-teinated lipoproteins and enriched with cationic cholesterylhydrochloride and phosphatidyl-ethanolamine The authorsafter intravenous administration of such cationic NPs for thedelivery of siRNA inhibiting c-Met expression suppressedtumor growth without evident signs of systemic toxicity inan orthotopic xenograft tumor mice model of glioblastoma

A second possibility is to functionalize the NPs surfacewith positively charged biomolecules combining their physic-ochemical features with biological activity This is the caseof cell-penetrating peptides (eg TAT peptides derived fromHIV gH625 derived from Herpes simplex virus type 1) andcationic proteins (eg albumin) [59] that have been exten-sively used for NPs decoration facilitating the BBB passageof drugs [60] As for example Rao et al [61] after admin-istration of ritonavir via TAT-conjugated NPs demonstratedapproximately an 800-fold higher level of drug in the brainwhen compared to that with free drug with a remarkableenhancement of drug delivery The authors suggested thatTAT-conjugated polymeric NPs are first mobilized in thebrain vasculatures then transported to the brain parenchymawhere they continue to release the drug

Polymeric micelles having TAT molecules on the surfacewere successfully fabricated also to incorporate antibioticsand were able to cross the BBB [62] In another study Xuet al [63] showed efficacy of TAT-polymeric NPs for thetreatment of C albicansmeningitis in rabbits Similar resultsare reported using another family of cell-penetrating peptides(SynB peptides RGGRLSYSRRRFSTSTGR) that were able toincrease drug permeability across a cocultured BBB modeldoubling drug transport in vivo in healthy mice [64]

Since the effect of cell-penetrating peptides could beinvalidated by the rapid systemic clearance of functionalizedNPs due to their positive charge in a study dedicated toinvestigate this issue Xia et al [65] utilized penetratin apeptide derived from Antennapedia protein (Drosophila)with relatively lower content of basic amino acids to func-tionalize poly(ethylene glycol)-poly(lactic acid) (PLGA)NPsfluorescently labeled with coumarin-6 and detected anincrease of fluorescence in the rodent brain with respect tounfunctionalized NPs

Xia et al [65] also combined the use of cell-penetratingpeptide to coumarin-6-loaded NPs for intranasal adminis-tration The amount of fluorescent probe detected in the ratcerebrum and cerebellum was found to be more than 2-foldcompared to that of coumarin carried by unfunctionalizedNPs Brain distribution analysis suggested that NPs afterintranasal administration could be delivered to the centralnervous system along both the olfactory and trigeminalnerves pathways

The efficacy of cationic albumin to functionalize andpromote NPs-carried drug delivery to the brain has beenrepeatedly reported [66 67]Theproperty of cationic proteinsto efficiently penetrate cells raises the question of the potentialtoxicity and immunogenicity of these proteins The possi-ble toxic effects include a generalized increase in vascularpermeability since breakdown of BBB permeability andother vascular beds has been observed following intravenousinjection of large amounts of cationic proteins but has notbeen seen when moderate amounts of these substances wereadministered [68]

53 Receptor-MediatedTranscytosis Oneof themost recentlyapplied strategies for drug delivery across the BBB endo-thelium using functionalized NPs is the one exploiting

ISRN Biochemistry 7

the transcytosis physiological mechanism of transport ofmacromolecules relying on the presence of specific recep-tors on the luminal surface of cells Transcytosis is theprocess by which extracellular cargo internalized at oneplasma membrane domain (eg apical) of a polarized cell istransported via vesicular intermediates to the controlateralplasma membrane (eg basolateral) As for example insulintransferrin apolipoproteins and 2-macroglobulin are someof the proteins that reach the brain following the path acrossendothelial cells

The rationale for exploiting this strategy with NPs is thatthe existing cellular mechanisms handling macromolecularcargoes may fit also to transport NPs after their functional-ization to interact with the same receptors

Transcytosis in endothelial cells starts with internal-ization of extracellular cargo into the cell by vesicularcarriers The cargo is subsequently processed via differentpathways to appropriate intracellular organelles and recycleddegraded or transcytosed to the contralateral side Strongmorphological and biochemical evidence suggest that thetwo membranes apical and basolateral are interconnectedvia vesicular intermediates involving multivesicular bodiesor a system of endosomal vacuoles and tubule vesiclesPhosphoinositide 3-kinase an enzyme increasingly demon-strated to play an important regulatory role inmany vesiculartrafficking events also appears to regulate transcytotic trafficbetween the two endosomal compartments

Transcytosis in endothelial cells starts with uptake eitherthrough clathrin-coated pits by caveolae or caveolae-likemembrane domains [69] that will be described here below

The first step of internalization through clathrin-mediated endocytosis is the binding of a ligand to a specificcell surface receptor This results in the clustering of theligand-receptor complexes in coated pits on the plasmamembrane which are formed by the assembly of cytosoliccoat proteins the main assembly units being clathrin whichform a polygonal lattice in the surface of the membrane andadaptor protein complexes which mediate the assembly ofthe clathrin lattice on the membrane The coated pits theninvaginate and pinch off from the plasma membrane to formintracellular clathrin-coated vesicles The clathrin coat thendepolymerizes resulting in early endosomes which fusewith each other or with other preexisting endosomes to formlate endosomes that further fuse with lysosomes Vesiculartrafficking after CME is controlled by the action of smallGTPases the Rab proteins

The second mechanisms internalization (caveolar) hasbeen clarified following the trafficking of some viruses thatuse caveolae to gain entry into the cells Caveolae aresmall flask-shaped invaginations of the plasma membranewith a size of about 50ndash60 nm that are rich in cholesteroland sphingolipids Viruses initially associate with the cellmembrane and then become trapped in relatively stationarycaveolae The subsequent intracellular uptake of caveolaeleads to intracellular organelles that are distinct from classicendosomes the presence of the protein caveolin in theseorganelles gave rise to the name caveosomes In contrast tothe dynamic nature of endosomes caveolae are highly stableand are only slowly internalized Another major difference is

that the caveolar uptake does not lead to a decrease of pHand to a degradative pathway of their cargo as in endoso-mallysosomal pathway

It is clear that the different pathways of NPs internal-ization affect their delivery to different intracellular com-partments and may affect their final destination To obtaininsight into the properties of drug delivery vehicles thatdirect their intracellular processing in brain endothelial cellsthe intracellular traffic of fixed-size nanoparticles in anin vitro BBB model as a function of distinct nanoparticlesurface modifications has been investigated Previous obser-vations [70] that latex particles with a diameter ge500 nm areinternalized by nonphagocytic B16 cells through caveolaewhereas particles up to 200 nm in diameter are efficientlytaken up via clathrin-mediated endocytosis were succes-sively confirmed with Silica-Hydroxyl NPs on immortalizedhuman brain capillary endothelial cell cultures [71] In theinvestigation of Georgieva et al [71] 500 nm particles wereused uncoated surface functionalized with cationic polymerpolyethyleneimine (PEI) or with prion protein The resultssuggested that uncoated NPs are internalized through cave-olae nanoparticles carrying a net cationic charge accom-plished by PEI followed an adsorptive endocytotic routeand particles surface-modified with prion protein followedreceptor-mediated endocytotic route Therefore the authorsconcluded that the NPs intracellular pathway is dictated bythe particle surface characteristic for a given size Mostinterestingly they found that the transcytotic potential ishigher for the receptor-mediated and caveolar pathways andlower for the adsorptive-mediated

However the enhancement of brain delivery obtainedwith drug-loaded NPs exploiting receptor- or caveolar-mediated transcytosis is currently quantitatively limited incomparison with the free drug Consequently also its clinicalrelevance is still scarce If we compare the hydrodynamicsize of most physiological proteins with that of NPs we areconfronting objects in the order of 5ndash10 nm size with thosethat in most cases are in the order of tenths of nanome-ters and commonly reach 100 nm and more Therefore itis conceivable that the transcytotic traffic may become abottleneck when transporting NPs It is also predictablethat smaller size NPs closer to the size of physiologicalmolecules would be facilitated to enter the same intracellu-lar transport pathways Following the strategy of receptor-mediated transport NPs made of gold PLGA chitosanPAA dendrimers and liposomes have been functionalizedimproving the delivery of drugs such as caspase inhibitorsendomorphin tamoxifen and tramadol and throwing thebasis for treatment of neurological diseases [72ndash79]

Exploring and targeting new receptors that could beutilized for receptor-dependent endocytosis are likely toprovide more efficient systems of brain drug delivery mainlybecause these uptakemechanisms are relatively unaffected bylysosomal degradation

531 Lipoprotein Receptors Apolipoprotein E (apoE) is a 34-kDa protein constituent of both very-low-density lipopro-tein (VLDL) and high-density lipoprotein (HDL) which

8 ISRN Biochemistry

transports cholesterol and other lipids in the plasma and inthe CNS [80 81] The lipoproteins complexes can be takenup in the brain through the recognition of apoE by specificreceptors at the BBB which include the low-density lipopro-tein receptor (LDLR) and the LDLR-related protein (LRP)

Taking into consideration that LRP has been reported tobe highly expressed on endothelial brain microvessels [82]receptor-mediated transcytosis using NPs functionalized tobind this target has been exploited in several ways

First by exploiting the preferential absorption of ApoEon some types of NPs when in serum This feature has beendescribed for PBCA NPs coated with polysorbate 80 indeeddisplaying the ability to cross the BBB in vivo in animalmodels [83ndash85] and for PEGylated PHDCA NPs able topenetrate into brain endothelial cells in vitro [86]

Taking advantage of such opportunity the formation ofa stable ApoE decoration of NPs surface by covalent bindinghas been utilized to functionalize albumin-NPs or liposomesthat showed the capacity of enhancing BBB passage in vivo inrodent models [87ndash89]

It should be questioned whether other apolipoproteinsmay be employed for NPs functionalization to confer onthem the ability to enhance brain drug delivery In order toanswer this question in an investigation of Kreuter et al [90]PBCA NPs loaded with dalargin or loperamide were coatedwith different apo-lipoproteins AII B CII E or J coatedor not with polysorbate 80 and then injected in mice andthe drug effect on CNS was evaluated The results showedthat only NPs coated with apolipoprotein B or E were able toachieve an antinociceptive effect This effect was significantlyhigher after polysorbate-precoating and apolipoprotein B orE-overcoating [90]

The region of apoE that is critical for interaction with theLDL receptor resides between amino acid residues 140 and160 Several studies with synthetic peptides have investigatedthe structural features of the LDLR-binding sequence ofApoE [91 92]

Laskowitz et al [81] derived an apoE-mimetic pep-tide from amino acids 133ndash149 named COG133 (LRVR-LASHLRKLRKRLL) which retains its biological activity invitro and in vivoThis capacity is displayed also by a fragmentof 26 aa from ApoE4 [93]

It has also been reported that the tandemdimer (141ndash155)2

is recognized by the LDLR in contrast to themonomeric pep-tide (141ndash155) [94] Also a shorter sequence of this peptide thetandem dimer (141ndash150)

2 retains this ability [95] Probably

as a consequence of these observations sterically stabilizedliposomeswere functionalized onlywithApoE tandemdimerpeptide (141ndash150)

2 but not with the monomer and were

shown to be efficiently taken up by rat brain capillaryendothelial cells [96] Interestingly in spite of the theoreticalpremises based on receptor-mediated endocytosis liposomestagged with (141ndash150)

2were nonselectively internalized into

cultured BBB cells and clathrin- or caveolin-dependentendocytosis was not demonstrable [97]

However in a successive investigation the ApoE-derivedpeptide monomer 141ndash150 was utilized by Re et al [98]in comparison with the dimer for the functionalization ofliposomes entrapping a radioactive derivative of curcumin

The investigation showed a higher uptake of the drug byhuman endothelial cells and an enhancement of permeabilityof the drug across an in vitromodel of the BBBmade with thesame cells when using monomer-functionalized liposomes

Apart from the amino acid sequence other factors mayaffect the cellular uptake of these peptides [98] These factorsinclude the type of peptide its cationic nature its mode ofexposure to the cell surface the nature of the cargo and thechemical linkage between the peptide and the cargo otherthan the peptide surface density on the cellular uptake ofnanoparticles [98 99]

Finally also Angiopep-2 a ligand of LRP possesses a highbrain penetration capability in both in vitro model of theBBB and in situ brain perfusion in mice [100] PEG-PAMAMdendrimers functionalized using this peptide resulted ina high accumulation of a delivered gene into brain afterintravenous administration into mice [101] moreover alsofunctionalized polymeric NPs and carbon nanotubes (CNT)have been produced showing the ability to reach gliomatumors in mice [102 103]

532 Transferrin Receptor (TfR) The transferrin receptor(TfR) is the most widely studied receptor for BBB targetingTfR is a transmembrane glycoprotein consisting of twolinked 90-kDa subunits each one binding a transferrinmolecule The receptor is highly expressed on immature ery-throid cells placental tissue and rapidly dividing cells bothnormal and malignant [104] Furthermore it is expressedon hepatocytes and endothelial cells of the BBB The role ofthe receptor is the regulation of cellular uptake of iron viatransferrin a plasma protein which transports iron in thecirculation Cellular uptake starts with the binding of trans-ferrin to the transferrin receptor followed by endocytosis[105]

Iron-bound transferrin has a high affinity for the TfRtherefore it has been used with success as a ligand for func-tionalization and targeting of liposomes to cultured brainendothelial cells [106 107] However it is likely that thatNPs decorated with transferrin would not be performantin vivo since transferrin receptors are almost saturated inphysiological conditions because of the high circulatinglevels of endogenous protein [108] Nevertheless successfulbrain targeting using transferrin as a targeting ligandhas beenaccomplished in vivo [109 110] Concerning the specificity oftransferrin a comparative study has been carried out betweentransferrin or lactoferrin a multifunctional protein of thetransferrin family widely represented in various secretoryfluids such as milk [111] Lalani et al [112] compared in vivodistribution in mice of PLGA NPs surface modified with thetwo proteins and showed a better performance to reach thebrain in the case of lactoferrin

In order to avoid the competition with endogenous trans-ferrin circulating in blood the use of monoclonal antibodies(mAbs) directed against transferrin receptors on the BBB hasbeen suggested because they recognize different epitopes onthe receptor [113] For instance OX26 8D3 and R17217 mAbbind to TfR and have also been shown to undergo receptor-mediated transcytosis

ISRN Biochemistry 9

Among these it is still debated which mAb is the bestperforming to be used for the decoration of NPs surface Themostwell known isOX26 an antibody directed against the ratTfR that has been successfully used in many brain targetingstudies in vivo [114] and also in vitro using BBB cellularmodels [115] However Lee et al [116] have shown that theOX26monoclonal antibody is not an effective brain targetingmolecule in mice Moreover they demonstrated that othertwo monoclonal antibodies 8D3 and RI7217 directed againstthe mouse TfR had a higher permeability of the mouseBBB in vivo with respect to the brain uptake of the OX26antibody which was negligible Additionally they showedthat RI7217wasmore selective for the brain than 8D3 becausethis antibody was less taken up by the liver and kidney Ithas been shown that RI7217 covalently coupled to humanserum albumin is able to transport loperamide across theBBB [110] More recently it has been shown that also thechemical linkage of anti-TfR on the NPs surface could affectthe crossing of BBB in vitro [117] The authors comparedliposomes covalently coupled with mAbs (obtained by react-ing thiolatedmAbs to phosphatidyl-ethanolaminemaleimideinserted in the liposome bilayer) with liposomes decoratedwith biotinylated mAbs via an avidin bridge The Authorsfound an higher cellular uptake and permeability across anin vitro BBB model made of immortalized human braincapillary endothelial cells of the liposomes covalently coupledwith mAbs suggesting that the covalent ligation could bepreferentially chosen for NPs decoration

54 Retrograde Transport Transsynaptic retrograde trans-port could enable some types of nanocarriers to travel fromperipheral nerve terminals to neuronal cell bodies in the CNS[118] Studies in this regard have shown that NPs modifiedwith PEI and other polyplexes display active retrogradetransport along neurites but are unable to mediate efficientbiological actions upon reaching the neuronal body [119]

55 BBB Breakdown BBB breakdown occurs in neuroin-flammatory diseases [120] NPs can transiently and reversiblyopen the tight junctions located at the BBB and other sitesthus increasing their paracellular permeability [121 122]In particular blood-brain barrier disruption therapy is anintensive effectiveway of sendingmedication to brain tumors[123]

Nevertheless it is known that tight junctions can beopened only to a limited extent [124] thus only NPs smallerthan about 20 nm can use this pathway to penetrate into thebrain through the BBB

56 Exploiting MonocyteMacrophage Infiltration in the CNSMonocytemacrophage infiltration in the CNS plays a keyrole in neuroinflammation as well as in lesion developmentand brain injury in neurological diseases such as multiplesclerosis (MS) and stroke [124ndash126] Knowledge of activephases of cell infiltration during CNS disorders is importantbecause anti-inflammatory treatments can target cell adhe-sion molecules and chemokines guiding cellular trafficking[127] The monocyte infiltration through the BBB is also

widely believed to play an important role in HIV infectionof the CNS The blood-brain barrier appears unaltered untilthe late stage of HIV encephalitis HIV flux that movestoward the brain thus relies on hijacking with immune-activated leukocytes mainly monocytesmacrophages fromthe periphery [128]

In this paper BBB crossing by immune-activated macro-phages appears to suggest possible strategies for future ther-apeutic developments employing NPs This strategy couldbe realized at least in two ways (1) by embedding NPs intoactivated monocytes used as Trojan horses to reach the brain(2) by designing NPs mimicking activated monocytes

561 Trojan Monocytes for NPs Delivery to the Brain Nano-particulate drug delivery systems have been used to avoidthe RES clearance and achieve longer circulation time forenhanced tissue uptake However the enhancing of NPsphagocytosis by monocytes can be considered as an uncon-ventional approach to deliver NPs-loaded drugs to thebrain After phagocytosis of NPs monocytes just like Trojanhorses may transport their cargo into the brain Aferganet al [129] taking this approach embedded serotonin aBBB impermeable neurological drug into negatively chargedliposomes and analyzed brain uptake in rats and rabbitsThe performance of liposomal serotonin was significantlybetter leading to two-fold higher drug concentration inbrain than the free drug Since treatment of animals byalendronate resulted with inhibition of monocytes but not ofneutrophils andwith no brain delivery the authors suggestedthat monocytes are the main transporters of liposomes tothe brain In spite of the fact that the clinical relevance ofthis investigation is limited the Trojan monocyte approachprovides a new possibility of more effective treatment ofbrain-associated inflammatory disorders including multiplesclerosis and Alzheimerrsquos disease which are characterizedwith increased passage of immune cells across the BBB[130]

In other examples in order to improve the delivery ofcontrast agents to the brain iron oxide NPs administeredintravenously in vivo have been shown to detect activatedmacrophage infiltration in multiple sclerosis either in theCNS of humans [131 132] or rodentmodel [133ndash137] in strokeeither in human [138 139] or animal brain ischemia [140ndash143] in human or murine intracranial tumors [144 145] inEAE [146ndash148] or in an ischemiareperfusion long-lived ratmodel [149]

562 NPs Mimicking Activated Monocytes The therapeu-tic efficacy of drug-loaded NPs systemically administereddepends on their ability to evade the immune system tocross the biological barriers of the body and to localizeat target tissues Parodi et al [150] show that nanoporoussilicon particles can successfully perform all these actionswhen they are coated with cellular membranes purifiedfrom leukocytes avoiding being cleared by the immune sys-tem Furthermore they can communicate with endothelialcells through receptor-ligand interactions and transport andrelease a doxorubicin payload across an inflamed endothelial

10 ISRN Biochemistry

barrier in vitro Also the accumulation of coated NPs inmice inoculated with murine B16 melanoma was enhancedcompared with that of non coated NPs Particle coatingusing leukocyte membranes led to an approximately twofoldincrease in particle density in the tumor

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsit is predictable that the research of NPs mimicking immunecells might be effective in brain-associated disorders and willreceive a stimulus in this direction in the next years

6 Factors Affecting NPs Brain Drug Delivery

61 NPs Diffusion inside the Brain Parenchyma While thisfactor is likely not particularly relevant when brain drugdelivery is sought after it could be very important when thepassage of the BBBbyNPs is looked for since the extracellularspace (ECS) of the brain parenchyma could limit their diffu-sion or even preclude their entrance into the brainThe abilityto achieve brain penetration with larger NPs is expected toallow more uniform longer lasting and effective delivery ofdrugs within the brain and may in particular find practicein the treatment of brain tumors stroke neuroinflammationand other brain diseases where the BBB is compromised orwhere local delivery strategies are feasible

Today it is well established that the ECSoccupies a volumefraction of between 15 and 30 in normal adult brain tissuewith a typical value of 20 and that this falls to 5 duringglobal ischemia [151 152]

It is less obvious what the true size of the spaces betweencells is Small molecules such as inulin and sucrose diffusethrough the ECS with a decreased diffusion coefficient withrespect to water suggesting the existence of limitation to theirmovements [153]

Possible sources of the limitations to the diffusing mol-ecules are (a) the presence of cellular obstructions (b) trap-ping of molecules in dead-space microdomains (c) a viscousdrag imposed by themacromolecules that compose the extra-cellular matrix or drag arising from the walls of the channelswhen molecules are large such as in the case of NPs(d) transient binding to cell membranes or extracellularmatrix (e) nonspecific interaction with negative charges onthe extracellular matrix when the diffusing molecule hasadequate charge density

A different type of model was proposed by Thorne andNicholson [154] to explain the higher tortuosity experimen-tally measured for larger substances such as dextran andespecially large synthetic quantum dot nanocrystals in the invivo rat cortex It was assumed that the quantum dots with ahydrodynamic diameter of 35 nm were close to the averagewidth of the ECS and depending on whether a planar ortubularmodel was adopted the estimated ECSwidth was 38ndash64 nm

In counter tendency to Thorne and Nicholson [154]Nance et al [155] report that NPs as large as 114 nm indiameter diffused within the human and rat brain only ifthey were densely coated with PEG Using these minimally

adhesive PEG-coated NPs they estimated that human braintissue ECS has some pores larger than 200 nm and that morethan one-quarter of all pores are ge100 nm

In addition to ECS in CNS there is also much interest inthe possibility that perivascular spaces fluid-filled channelssurrounding arteries arterioles veins venules and possiblyevenmicrovessels offer potential pathways for rapid flow intoand out of brain parenchyma Measurements of perivascularspace widths in mammals suggest that their typical dimen-sions may be at least 2 orders of magnitude greater thanthe neocortical ECS width (eg arteriole perivascular spaceshave been reported in the range of 5ndash10 120583m or larger (inrodents and humans))

62 Effect of Protein Corona Different physicochemicalproperties not only size may determine the ability ofnanoparticles to reach the brain The situation is furthercomplicated by the formation of a so-called ldquocoronardquo ofbiomolecules on the surfaces of nanoparticles the composi-tion of which may vary depending on the route of exposureand on the physicochemical surface properties of NPs Theacquisition of a corona of biomolecules on the surface ofNPs may also determine whether NPs are able to cross fromone compartment to another and whether they are taken upeffectively by cells or not [156]

In practical situations in which nanoparticles interactwith living organisms the nanoparticle surfaces are initiallyexposed to a biological fluid such as blood dependingon the route of administration For instance NPs injectedintravenously would be exposed to blood plasma containingan excess of proteins and many other complex biomoleculeswhich bind competitively with the surface of the nanoparti-cles

The current idea is that ldquobarerdquo nanoparticles do notexist in vivo because they are immediately modified bythe adsorption of blood proteins with higher affinities forthe particle surface forming a more or less tightly boundlayer (the so-called hard corona) and a weakly associatedmobile layer (the so-called soft corona) When this issue wasinvestigated it has been found that typical coronas containa limited number and types of molecules gathered fromthe blood in spite of the fact that biological fluids containthousands of proteins [157] Moreover it should be noted thatthe corona may also play a role in other undesirable effectsof NPs in living systems such as complement activation andblood clotting and may not necessarily play a role only incellular uptake

It should be pointed out that none of the in vitro exper-iments conducted to study the process of NPs translocationto the brain takes into account the surface modification ofNPs inside the blood and how can this affect the crossingof the BBB This issue needs much further investigationMoreover NPs once internalized by endothelial BBB cellsthey may also exit towards the brain covered with differentbiomolecules depending on that they have undergone endo-cytosistranscytosisexocytosis and thus exert additionaleffects (eg toxicity) on neuron Also this issue has not yetbeen investigated

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

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[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

[12] W M Pardridge ldquoDrug transport across the blood-brainbarrierrdquo Journal of Cerebral Blood Flow amp Metabolism vol 32no 11 pp 1959ndash1972 2012

[13] A Minn S Leclerc J M Heydel et al ldquoDrug transport into themammalian brain the nasal pathway and its specific metabolicbarrierrdquo Journal of Drug Targeting vol 10 no 4 pp 285rndash296r2002

[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

[23] L Martin-Banderas M A Holgado J L Venero J Alvarez-Fuentes and M Fernadez-Arealo ldquoNanostructures for drugdelivery to the brainrdquoCurrentMedicinal Chemistry vol 148 no34 pp 5303ndash5321 2011

[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

[26] T Ishii T Asai D Oyama et al ldquoTreatment of cerebralischemia-reperfusion injury with PEGylated liposomes encap-sulating FK506rdquo FASEB Journal vol 27 no 4 pp 1362ndash13702013

[27] A Lindqvist J Rip P J Gaillard S Bjorkman and MHammarlund-Udenaes ldquoEnhanced brain delivery of the opioidpeptide DAMGO in glutathione PEGylated liposomes amicro-dialysis studyrdquoMolecular Pharmacology 2012

[28] A Orthmann R Zeisig R Suss D Lorenz M Lemm andI Fichtner ldquoTreatment of experimental brain metastasis withMTO-liposomes impact of fluidity and LRP-targeting on thetherapeutic resultrdquo Pharmaceutical Research vol 29 no 7 pp1949ndash1959 2012

[29] M T da Cruz S Simoes and M C de Lima ldquoImprovinglipoplex-mediated gene transfer into C6 glioma cells andprimary neuronsrdquo Experimental Neurology vol 187 no 1 pp65ndash75 2004

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[31] A Molinari M Colone A Calcabrini et al ldquoCationic lipo-somes loaded with m-THPC in photodynamic therapy for

14 ISRN Biochemistry

malignant gliomardquo Toxicology in Vitro vol 21 no 2 pp 230ndash234 2007

[32] Y Obata G Ciofani V Raffa et al ldquoEvaluation of cationicliposomes composed of an amino acid-based lipid for neuronaltransfectionrdquo Nanomedicine vol 6 no 1 pp e70ndashe77 2010

[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

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[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

[40] S Md M Ali S Baboota et al ldquoPreparation characteri-zation in vivo biodistribution and pharmacokinetic studiesof donepezil-loaded PLGA nanoparticles for brain targetingrdquoDrug Development and Industrial Pharmacy 2013

[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

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[44] R Pandey and G K Khuller ldquoOral nanoparticle-based antitu-berculosis drug delivery to the brain in an experimental modelrdquoJournal of Antimicrobial Chemotherapy vol 57 no 6 pp 1146ndash1152 2006

[45] L Hasadsri J Kreuter H Hattori T Iwasaki and J M GeorgeldquoFunctional protein delivery into neurons using polymericnanoparticlesrdquo Journal of Biological Chemistry vol 284 no 11pp 6972ndash6981 2009

[46] A V Kabanov E V Batrakova N S Melik-Nubarov et alldquoA new class of drug carriers micelles of poly(oxyethylene)-poly(oxypropylene) block copolymers as microcontainers for

drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

[50] L Albertazzi L Gherardini M Brondi et al ldquoIn vivo dis-tribution and toxicity of PAMAM dendrimers in the centralnervous system depend on their surface chemistryrdquo MolecularPharmacology vol 10 no 1 pp 249ndash260 2013

[51] S Kannan H Dai R S Navath et al ldquoDendrimer-basedpostnatal therapy for neuroinflammation and cerebral palsy ina rabbit modelrdquo Science Translational Medicine vol 4 no 130Article ID 130ra46 2012

[52] J Wu C Wang J Sun and Y Xue ldquoNeurotoxicity of silicananoparticles brain localization and dopaminergic neuronsdamage pathwaysrdquoACSNano vol 5 no 6 pp 4476ndash4489 2011

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[54] Y Ze L Zheng X Zhao et al ldquoMolecular mechanism oftitanium dioxide nanoparticles-induced oxidative injury in thebrain of micerdquo Chemosphere 2013

[55] R D Broadwell ldquoTranscytosis of macromolecules through theblood-brain barrier a cell biological perspective and criticalappraisalrdquo Acta Neuropathologica vol 79 no 2 pp 117ndash1281989

[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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PeptidesInternational Journal of

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Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

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Molecular Biology International

GenomicsInternational Journal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

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BioinformaticsAdvances in

Marine BiologyJournal of

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Signal TransductionJournal of

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BioMed Research International

Evolutionary BiologyInternational Journal of

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Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Advances in

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Enzyme Research

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International Journal of

Microbiology

ISRN Biochemistry 5

liposomes carrying a photoreactive drug resulted in a laser-stimulated cytotoxic effect on glioblastoma cells and showedthe ability to improve brain drug delivery of paclitaxel(a mitotic inhibitor used in cancer chemotherapy) in rodentsin vivo [31ndash33]

412 Solid Lipid Nanoparticles Solid lipid nanoparticles(SLN) are a stable lipid-based nanocarrier with a solidhydrophobic lipid core in which the drug can be dissolvedor dispersed [34] They are made with biocompatible lipidssuch as triglycerides fatty acids or waxes They are generallyof small size (around 40ndash200 nm) allowing them to crosstight endothelial cells of the BBB and escape from thereticuloendothelial system (RES) [35]

During their fabrication the melted lipid mixed withthe drug is commonly dispersed in an aqueous surfactantby high-pressure homogenization or microemulsificationThe advantages of SLN are their biocompatibility drugentrapment efficiency comparatively higher than other NPsand the ability to provide a continuous release of the drugfor several weeks [36] Moreover the composition of SLNcan be controlled modifying their surface properties to targetmolecules to the brain and to limit RES uptake [37]

Several reports are available describing an enhanced drugdelivery to the brain mediated by SLN For instance SLNcarrying a calcium channel blocker drug administered ivinto rodent showed that the drug was taken up to a greaterextent by the brain and maintained high drug levels for alonger time compared to free drug suspension

Wang et al have reported the synthesis of 310158405-dioctanoyl-5-fluoro-2-deoxyuridine (DO-FUdR) to overcome the lim-ited access of the drug 5-fluoro-2-deoxyuridine (FUdR) andits incorporation into SLN The results indicated that DO-FUdR-SLN had brain targeting efficiency in vivo of about 2-fold compared to free FUdR These authors report that SLNcan improve the ability of the drug to penetrate throughthe BBB and is a promising drug targeting system for thetreatment of central nervous system disorders [38 39]

42 Polymer-Based Nanoparticles

421 Polymeric Nanoparticles Polymeric NPs are composedof a core polymer matrix in which drugs can be embedded[40ndash42] with sizes usually between 60 and 200 nm A rangeof materials have been employed for delivery of drugs Inparticular in recent years some polymers have been designedprimarily for medical applications and have entered thearena of controlled release of bioactive agents Many ofthese materials are designed to degrade within the bodyMost popular ones are polylactides (PLA) polyglycolides(PGA) poly(lactide-co-glycolides) (PLGA) polyanhydridespolycyanoacrylates and polycaprolactone In spite of devel-opment of various synthetic and semi-synthetic polymersalso natural polymers such as chitosan can be utilized

Also in the case of polymeric NPs reports are avail-able describing an enhanced drug delivery to the brainmediated by these devices NPs made of PLGA embeddingantituberculosis drugs (rifampicin isoniazid pyrazinamide

and ethambutol) for cerebral drug deliverywere administeredto mice maintaining high drug levels for 5ndash8 days in plasmaand for 9 days in the brain much higher as comparedwith free drugs [43] InMycobacterium tuberculosis-infectedmice 5 doses of the NPs formulation (against 46 doses ofconventional free drugs) resulted in undetectable bacteriain the meninges [44] In another research [45] polybutyl-cyanoacrylate (PBCA) NPs were successfully utilized fordelivery of functional proteins into neurons and neuronal celllines

422 Polymeric Micelles Polymeric micelles are formedby amphiphilic copolymers whose aggregation in aqueousmedia leads to spheroidal structures with a hydrophilic shelland a hydrophobic core and with a good grade of stability[36] Stability can be improved by crosslinking between theshell or the core chains Additional tunable features of poly-meric micelles are the possibility to render them responsiveto external stimuli (pH light temperature ultrasound etc)[46] triggering a controllable release of entrapped drugsOne of the most utilized polymer is Pluronic type blockcopolymer based on ethylene oxide and propylene oxide

The possibility to use these NPs for brain drug deliv-ery has been described For instance chitosan-conjugatedPluronic nanocarriers with a specific target peptide forthe brain (rabies virus glycoprotein RVG29) following ivinjection in mice displayed in vivo brain accumulation eitherof a quantum dot fluorophore conjugated to the nanocarrieror of a protein loaded into the carrier [47] Other studieshave shown an increased central analgesic effect of micellar-vehicled drug [48]

423 Dendrimers Dendrimers are branched polymersreminding the structure of a tree A dendrimer is typicallysymmetric around the core and when sufficiently extended itoften adopts a spheroidal three-dimensional morphology inwater A central core can be recognized in their structure withat least two identical chemical functionalities starting fromthese groups repeated units of other molecules can originatehaving at least one junction of branching The repetitions ofchains and branching result in a series of radially concentriclayers with increased crowding The structure is thereforetightly packed in the periphery and loosely packed in thecore leaving spaces which play a key role in the drug-entrapping ability of dendrimers [49] Poly(amidoamine)or PAMAM is perhaps the most well-known molecule forsynthesis of dendrimers The core of PAMAM is a diamine(commonly ethylenediamine) which is reacted with methylacrylate and then with another ethylenediamine to makethe generation-0 PAMAM Successive reactions create highergenerations Albertazzi et al [50] showed that functionaliza-tion of PAMAMs dendrimers has a dramatic effect on theirability to diffuse in the CNS tissue in vivo and penetrate livingneurons as shown after intraparenchymal or intraventricularinjections

Kannan et al [51] showed that systemically administeredpolyamidoamine dendrimers localize in activated microgliaand astrocytes in the brain of newborn rabbits with cerebral

6 ISRN Biochemistry

palsy providing opportunities for clinical translation in thetreatment of neuroinflammatory disorders in humans

5 How NPs Can Cross the BBB

Many medicines are not able to reach the brain due to thelack of drug-specific transport systems through the BBBThedevelopment of new strategies based on NPs to enhance thebrain drug delivery is of great importance in the therapy anddiagnosis of CNS diseases and it is based on the interactionsbetween NPs and the BBB and on their intracellular trafficpathways

51 Crossing the BBB without Functionalization Althoughalmost all nanomaterials fall into the class of BBB imper-meable some exceptions have been reported in recent yearsFor instance gold and silica NPs have been shown to reachthe brain and accumulate in neurons even in the absenceof any specific functionalization with a mechanism thatsubstantially is still unknown In the case of silica the resultsindicated that NPs administered to rodents via intranasalinstillation entered into the brain and especially depositedin the striatum [52] In the case of gold NPs precise particledistribution in the brain was studied ex vivo by X-ray micro-tomography confocal laser andfluorescencemicroscopy [53]The authors found that the particles mainly accumulate inthe hippocampus thalamus hypothalamus and the cerebralcortex The same holds true for Titanium dioxide NPs thatwere found to cross the mice BBB particularly when smallerthan 40 nm [54]

52 Adsorptive-Mediated Transcytosis The concept of ad-sorptive-mediated transcytosis through the BBB was orig-inally suggested by the observation that cationic proteinscan bind the endothelial cell surface but also cross the BBB[55] The mechanism applied to NPs is based on the properfunctionalization of their surface allowing electrostatic inter-action with the luminal surface of BBB Given the presenceof negative charges on endothelial cells [56] this interactioncan be promoted by conferring a positive charge to the NPssurface

Different procedures can be followed to realize this issueA first possibility is to build up NPs made of componentsthat are bearing a positive charged at physiological pH (74)This is the case of nanosized vesiclesmade of bolaamphiphilicmolecules (amphiphilic molecules that have hydrophilicgroups at both ends of an hydrophobic chain) that followingintravenous administration to mice showed a marked accu-mulation of their encapsulated fluorescent cargo whereasnonencapsulated probe was detected only in peripheraltissues but not in the brain [57] In another investigation Jinet al [58] used SLN made with lipids extracted from depro-teinated lipoproteins and enriched with cationic cholesterylhydrochloride and phosphatidyl-ethanolamine The authorsafter intravenous administration of such cationic NPs for thedelivery of siRNA inhibiting c-Met expression suppressedtumor growth without evident signs of systemic toxicity inan orthotopic xenograft tumor mice model of glioblastoma

A second possibility is to functionalize the NPs surfacewith positively charged biomolecules combining their physic-ochemical features with biological activity This is the caseof cell-penetrating peptides (eg TAT peptides derived fromHIV gH625 derived from Herpes simplex virus type 1) andcationic proteins (eg albumin) [59] that have been exten-sively used for NPs decoration facilitating the BBB passageof drugs [60] As for example Rao et al [61] after admin-istration of ritonavir via TAT-conjugated NPs demonstratedapproximately an 800-fold higher level of drug in the brainwhen compared to that with free drug with a remarkableenhancement of drug delivery The authors suggested thatTAT-conjugated polymeric NPs are first mobilized in thebrain vasculatures then transported to the brain parenchymawhere they continue to release the drug

Polymeric micelles having TAT molecules on the surfacewere successfully fabricated also to incorporate antibioticsand were able to cross the BBB [62] In another study Xuet al [63] showed efficacy of TAT-polymeric NPs for thetreatment of C albicansmeningitis in rabbits Similar resultsare reported using another family of cell-penetrating peptides(SynB peptides RGGRLSYSRRRFSTSTGR) that were able toincrease drug permeability across a cocultured BBB modeldoubling drug transport in vivo in healthy mice [64]

Since the effect of cell-penetrating peptides could beinvalidated by the rapid systemic clearance of functionalizedNPs due to their positive charge in a study dedicated toinvestigate this issue Xia et al [65] utilized penetratin apeptide derived from Antennapedia protein (Drosophila)with relatively lower content of basic amino acids to func-tionalize poly(ethylene glycol)-poly(lactic acid) (PLGA)NPsfluorescently labeled with coumarin-6 and detected anincrease of fluorescence in the rodent brain with respect tounfunctionalized NPs

Xia et al [65] also combined the use of cell-penetratingpeptide to coumarin-6-loaded NPs for intranasal adminis-tration The amount of fluorescent probe detected in the ratcerebrum and cerebellum was found to be more than 2-foldcompared to that of coumarin carried by unfunctionalizedNPs Brain distribution analysis suggested that NPs afterintranasal administration could be delivered to the centralnervous system along both the olfactory and trigeminalnerves pathways

The efficacy of cationic albumin to functionalize andpromote NPs-carried drug delivery to the brain has beenrepeatedly reported [66 67]Theproperty of cationic proteinsto efficiently penetrate cells raises the question of the potentialtoxicity and immunogenicity of these proteins The possi-ble toxic effects include a generalized increase in vascularpermeability since breakdown of BBB permeability andother vascular beds has been observed following intravenousinjection of large amounts of cationic proteins but has notbeen seen when moderate amounts of these substances wereadministered [68]

53 Receptor-MediatedTranscytosis Oneof themost recentlyapplied strategies for drug delivery across the BBB endo-thelium using functionalized NPs is the one exploiting

ISRN Biochemistry 7

the transcytosis physiological mechanism of transport ofmacromolecules relying on the presence of specific recep-tors on the luminal surface of cells Transcytosis is theprocess by which extracellular cargo internalized at oneplasma membrane domain (eg apical) of a polarized cell istransported via vesicular intermediates to the controlateralplasma membrane (eg basolateral) As for example insulintransferrin apolipoproteins and 2-macroglobulin are someof the proteins that reach the brain following the path acrossendothelial cells

The rationale for exploiting this strategy with NPs is thatthe existing cellular mechanisms handling macromolecularcargoes may fit also to transport NPs after their functional-ization to interact with the same receptors

Transcytosis in endothelial cells starts with internal-ization of extracellular cargo into the cell by vesicularcarriers The cargo is subsequently processed via differentpathways to appropriate intracellular organelles and recycleddegraded or transcytosed to the contralateral side Strongmorphological and biochemical evidence suggest that thetwo membranes apical and basolateral are interconnectedvia vesicular intermediates involving multivesicular bodiesor a system of endosomal vacuoles and tubule vesiclesPhosphoinositide 3-kinase an enzyme increasingly demon-strated to play an important regulatory role inmany vesiculartrafficking events also appears to regulate transcytotic trafficbetween the two endosomal compartments

Transcytosis in endothelial cells starts with uptake eitherthrough clathrin-coated pits by caveolae or caveolae-likemembrane domains [69] that will be described here below

The first step of internalization through clathrin-mediated endocytosis is the binding of a ligand to a specificcell surface receptor This results in the clustering of theligand-receptor complexes in coated pits on the plasmamembrane which are formed by the assembly of cytosoliccoat proteins the main assembly units being clathrin whichform a polygonal lattice in the surface of the membrane andadaptor protein complexes which mediate the assembly ofthe clathrin lattice on the membrane The coated pits theninvaginate and pinch off from the plasma membrane to formintracellular clathrin-coated vesicles The clathrin coat thendepolymerizes resulting in early endosomes which fusewith each other or with other preexisting endosomes to formlate endosomes that further fuse with lysosomes Vesiculartrafficking after CME is controlled by the action of smallGTPases the Rab proteins

The second mechanisms internalization (caveolar) hasbeen clarified following the trafficking of some viruses thatuse caveolae to gain entry into the cells Caveolae aresmall flask-shaped invaginations of the plasma membranewith a size of about 50ndash60 nm that are rich in cholesteroland sphingolipids Viruses initially associate with the cellmembrane and then become trapped in relatively stationarycaveolae The subsequent intracellular uptake of caveolaeleads to intracellular organelles that are distinct from classicendosomes the presence of the protein caveolin in theseorganelles gave rise to the name caveosomes In contrast tothe dynamic nature of endosomes caveolae are highly stableand are only slowly internalized Another major difference is

that the caveolar uptake does not lead to a decrease of pHand to a degradative pathway of their cargo as in endoso-mallysosomal pathway

It is clear that the different pathways of NPs internal-ization affect their delivery to different intracellular com-partments and may affect their final destination To obtaininsight into the properties of drug delivery vehicles thatdirect their intracellular processing in brain endothelial cellsthe intracellular traffic of fixed-size nanoparticles in anin vitro BBB model as a function of distinct nanoparticlesurface modifications has been investigated Previous obser-vations [70] that latex particles with a diameter ge500 nm areinternalized by nonphagocytic B16 cells through caveolaewhereas particles up to 200 nm in diameter are efficientlytaken up via clathrin-mediated endocytosis were succes-sively confirmed with Silica-Hydroxyl NPs on immortalizedhuman brain capillary endothelial cell cultures [71] In theinvestigation of Georgieva et al [71] 500 nm particles wereused uncoated surface functionalized with cationic polymerpolyethyleneimine (PEI) or with prion protein The resultssuggested that uncoated NPs are internalized through cave-olae nanoparticles carrying a net cationic charge accom-plished by PEI followed an adsorptive endocytotic routeand particles surface-modified with prion protein followedreceptor-mediated endocytotic route Therefore the authorsconcluded that the NPs intracellular pathway is dictated bythe particle surface characteristic for a given size Mostinterestingly they found that the transcytotic potential ishigher for the receptor-mediated and caveolar pathways andlower for the adsorptive-mediated

However the enhancement of brain delivery obtainedwith drug-loaded NPs exploiting receptor- or caveolar-mediated transcytosis is currently quantitatively limited incomparison with the free drug Consequently also its clinicalrelevance is still scarce If we compare the hydrodynamicsize of most physiological proteins with that of NPs we areconfronting objects in the order of 5ndash10 nm size with thosethat in most cases are in the order of tenths of nanome-ters and commonly reach 100 nm and more Therefore itis conceivable that the transcytotic traffic may become abottleneck when transporting NPs It is also predictablethat smaller size NPs closer to the size of physiologicalmolecules would be facilitated to enter the same intracellu-lar transport pathways Following the strategy of receptor-mediated transport NPs made of gold PLGA chitosanPAA dendrimers and liposomes have been functionalizedimproving the delivery of drugs such as caspase inhibitorsendomorphin tamoxifen and tramadol and throwing thebasis for treatment of neurological diseases [72ndash79]

Exploring and targeting new receptors that could beutilized for receptor-dependent endocytosis are likely toprovide more efficient systems of brain drug delivery mainlybecause these uptakemechanisms are relatively unaffected bylysosomal degradation

531 Lipoprotein Receptors Apolipoprotein E (apoE) is a 34-kDa protein constituent of both very-low-density lipopro-tein (VLDL) and high-density lipoprotein (HDL) which

8 ISRN Biochemistry

transports cholesterol and other lipids in the plasma and inthe CNS [80 81] The lipoproteins complexes can be takenup in the brain through the recognition of apoE by specificreceptors at the BBB which include the low-density lipopro-tein receptor (LDLR) and the LDLR-related protein (LRP)

Taking into consideration that LRP has been reported tobe highly expressed on endothelial brain microvessels [82]receptor-mediated transcytosis using NPs functionalized tobind this target has been exploited in several ways

First by exploiting the preferential absorption of ApoEon some types of NPs when in serum This feature has beendescribed for PBCA NPs coated with polysorbate 80 indeeddisplaying the ability to cross the BBB in vivo in animalmodels [83ndash85] and for PEGylated PHDCA NPs able topenetrate into brain endothelial cells in vitro [86]

Taking advantage of such opportunity the formation ofa stable ApoE decoration of NPs surface by covalent bindinghas been utilized to functionalize albumin-NPs or liposomesthat showed the capacity of enhancing BBB passage in vivo inrodent models [87ndash89]

It should be questioned whether other apolipoproteinsmay be employed for NPs functionalization to confer onthem the ability to enhance brain drug delivery In order toanswer this question in an investigation of Kreuter et al [90]PBCA NPs loaded with dalargin or loperamide were coatedwith different apo-lipoproteins AII B CII E or J coatedor not with polysorbate 80 and then injected in mice andthe drug effect on CNS was evaluated The results showedthat only NPs coated with apolipoprotein B or E were able toachieve an antinociceptive effect This effect was significantlyhigher after polysorbate-precoating and apolipoprotein B orE-overcoating [90]

The region of apoE that is critical for interaction with theLDL receptor resides between amino acid residues 140 and160 Several studies with synthetic peptides have investigatedthe structural features of the LDLR-binding sequence ofApoE [91 92]

Laskowitz et al [81] derived an apoE-mimetic pep-tide from amino acids 133ndash149 named COG133 (LRVR-LASHLRKLRKRLL) which retains its biological activity invitro and in vivoThis capacity is displayed also by a fragmentof 26 aa from ApoE4 [93]

It has also been reported that the tandemdimer (141ndash155)2

is recognized by the LDLR in contrast to themonomeric pep-tide (141ndash155) [94] Also a shorter sequence of this peptide thetandem dimer (141ndash150)

2 retains this ability [95] Probably

as a consequence of these observations sterically stabilizedliposomeswere functionalized onlywithApoE tandemdimerpeptide (141ndash150)

2 but not with the monomer and were

shown to be efficiently taken up by rat brain capillaryendothelial cells [96] Interestingly in spite of the theoreticalpremises based on receptor-mediated endocytosis liposomestagged with (141ndash150)

2were nonselectively internalized into

cultured BBB cells and clathrin- or caveolin-dependentendocytosis was not demonstrable [97]

However in a successive investigation the ApoE-derivedpeptide monomer 141ndash150 was utilized by Re et al [98]in comparison with the dimer for the functionalization ofliposomes entrapping a radioactive derivative of curcumin

The investigation showed a higher uptake of the drug byhuman endothelial cells and an enhancement of permeabilityof the drug across an in vitromodel of the BBBmade with thesame cells when using monomer-functionalized liposomes

Apart from the amino acid sequence other factors mayaffect the cellular uptake of these peptides [98] These factorsinclude the type of peptide its cationic nature its mode ofexposure to the cell surface the nature of the cargo and thechemical linkage between the peptide and the cargo otherthan the peptide surface density on the cellular uptake ofnanoparticles [98 99]

Finally also Angiopep-2 a ligand of LRP possesses a highbrain penetration capability in both in vitro model of theBBB and in situ brain perfusion in mice [100] PEG-PAMAMdendrimers functionalized using this peptide resulted ina high accumulation of a delivered gene into brain afterintravenous administration into mice [101] moreover alsofunctionalized polymeric NPs and carbon nanotubes (CNT)have been produced showing the ability to reach gliomatumors in mice [102 103]

532 Transferrin Receptor (TfR) The transferrin receptor(TfR) is the most widely studied receptor for BBB targetingTfR is a transmembrane glycoprotein consisting of twolinked 90-kDa subunits each one binding a transferrinmolecule The receptor is highly expressed on immature ery-throid cells placental tissue and rapidly dividing cells bothnormal and malignant [104] Furthermore it is expressedon hepatocytes and endothelial cells of the BBB The role ofthe receptor is the regulation of cellular uptake of iron viatransferrin a plasma protein which transports iron in thecirculation Cellular uptake starts with the binding of trans-ferrin to the transferrin receptor followed by endocytosis[105]

Iron-bound transferrin has a high affinity for the TfRtherefore it has been used with success as a ligand for func-tionalization and targeting of liposomes to cultured brainendothelial cells [106 107] However it is likely that thatNPs decorated with transferrin would not be performantin vivo since transferrin receptors are almost saturated inphysiological conditions because of the high circulatinglevels of endogenous protein [108] Nevertheless successfulbrain targeting using transferrin as a targeting ligandhas beenaccomplished in vivo [109 110] Concerning the specificity oftransferrin a comparative study has been carried out betweentransferrin or lactoferrin a multifunctional protein of thetransferrin family widely represented in various secretoryfluids such as milk [111] Lalani et al [112] compared in vivodistribution in mice of PLGA NPs surface modified with thetwo proteins and showed a better performance to reach thebrain in the case of lactoferrin

In order to avoid the competition with endogenous trans-ferrin circulating in blood the use of monoclonal antibodies(mAbs) directed against transferrin receptors on the BBB hasbeen suggested because they recognize different epitopes onthe receptor [113] For instance OX26 8D3 and R17217 mAbbind to TfR and have also been shown to undergo receptor-mediated transcytosis

ISRN Biochemistry 9

Among these it is still debated which mAb is the bestperforming to be used for the decoration of NPs surface Themostwell known isOX26 an antibody directed against the ratTfR that has been successfully used in many brain targetingstudies in vivo [114] and also in vitro using BBB cellularmodels [115] However Lee et al [116] have shown that theOX26monoclonal antibody is not an effective brain targetingmolecule in mice Moreover they demonstrated that othertwo monoclonal antibodies 8D3 and RI7217 directed againstthe mouse TfR had a higher permeability of the mouseBBB in vivo with respect to the brain uptake of the OX26antibody which was negligible Additionally they showedthat RI7217wasmore selective for the brain than 8D3 becausethis antibody was less taken up by the liver and kidney Ithas been shown that RI7217 covalently coupled to humanserum albumin is able to transport loperamide across theBBB [110] More recently it has been shown that also thechemical linkage of anti-TfR on the NPs surface could affectthe crossing of BBB in vitro [117] The authors comparedliposomes covalently coupled with mAbs (obtained by react-ing thiolatedmAbs to phosphatidyl-ethanolaminemaleimideinserted in the liposome bilayer) with liposomes decoratedwith biotinylated mAbs via an avidin bridge The Authorsfound an higher cellular uptake and permeability across anin vitro BBB model made of immortalized human braincapillary endothelial cells of the liposomes covalently coupledwith mAbs suggesting that the covalent ligation could bepreferentially chosen for NPs decoration

54 Retrograde Transport Transsynaptic retrograde trans-port could enable some types of nanocarriers to travel fromperipheral nerve terminals to neuronal cell bodies in the CNS[118] Studies in this regard have shown that NPs modifiedwith PEI and other polyplexes display active retrogradetransport along neurites but are unable to mediate efficientbiological actions upon reaching the neuronal body [119]

55 BBB Breakdown BBB breakdown occurs in neuroin-flammatory diseases [120] NPs can transiently and reversiblyopen the tight junctions located at the BBB and other sitesthus increasing their paracellular permeability [121 122]In particular blood-brain barrier disruption therapy is anintensive effectiveway of sendingmedication to brain tumors[123]

Nevertheless it is known that tight junctions can beopened only to a limited extent [124] thus only NPs smallerthan about 20 nm can use this pathway to penetrate into thebrain through the BBB

56 Exploiting MonocyteMacrophage Infiltration in the CNSMonocytemacrophage infiltration in the CNS plays a keyrole in neuroinflammation as well as in lesion developmentand brain injury in neurological diseases such as multiplesclerosis (MS) and stroke [124ndash126] Knowledge of activephases of cell infiltration during CNS disorders is importantbecause anti-inflammatory treatments can target cell adhe-sion molecules and chemokines guiding cellular trafficking[127] The monocyte infiltration through the BBB is also

widely believed to play an important role in HIV infectionof the CNS The blood-brain barrier appears unaltered untilthe late stage of HIV encephalitis HIV flux that movestoward the brain thus relies on hijacking with immune-activated leukocytes mainly monocytesmacrophages fromthe periphery [128]

In this paper BBB crossing by immune-activated macro-phages appears to suggest possible strategies for future ther-apeutic developments employing NPs This strategy couldbe realized at least in two ways (1) by embedding NPs intoactivated monocytes used as Trojan horses to reach the brain(2) by designing NPs mimicking activated monocytes

561 Trojan Monocytes for NPs Delivery to the Brain Nano-particulate drug delivery systems have been used to avoidthe RES clearance and achieve longer circulation time forenhanced tissue uptake However the enhancing of NPsphagocytosis by monocytes can be considered as an uncon-ventional approach to deliver NPs-loaded drugs to thebrain After phagocytosis of NPs monocytes just like Trojanhorses may transport their cargo into the brain Aferganet al [129] taking this approach embedded serotonin aBBB impermeable neurological drug into negatively chargedliposomes and analyzed brain uptake in rats and rabbitsThe performance of liposomal serotonin was significantlybetter leading to two-fold higher drug concentration inbrain than the free drug Since treatment of animals byalendronate resulted with inhibition of monocytes but not ofneutrophils andwith no brain delivery the authors suggestedthat monocytes are the main transporters of liposomes tothe brain In spite of the fact that the clinical relevance ofthis investigation is limited the Trojan monocyte approachprovides a new possibility of more effective treatment ofbrain-associated inflammatory disorders including multiplesclerosis and Alzheimerrsquos disease which are characterizedwith increased passage of immune cells across the BBB[130]

In other examples in order to improve the delivery ofcontrast agents to the brain iron oxide NPs administeredintravenously in vivo have been shown to detect activatedmacrophage infiltration in multiple sclerosis either in theCNS of humans [131 132] or rodentmodel [133ndash137] in strokeeither in human [138 139] or animal brain ischemia [140ndash143] in human or murine intracranial tumors [144 145] inEAE [146ndash148] or in an ischemiareperfusion long-lived ratmodel [149]

562 NPs Mimicking Activated Monocytes The therapeu-tic efficacy of drug-loaded NPs systemically administereddepends on their ability to evade the immune system tocross the biological barriers of the body and to localizeat target tissues Parodi et al [150] show that nanoporoussilicon particles can successfully perform all these actionswhen they are coated with cellular membranes purifiedfrom leukocytes avoiding being cleared by the immune sys-tem Furthermore they can communicate with endothelialcells through receptor-ligand interactions and transport andrelease a doxorubicin payload across an inflamed endothelial

10 ISRN Biochemistry

barrier in vitro Also the accumulation of coated NPs inmice inoculated with murine B16 melanoma was enhancedcompared with that of non coated NPs Particle coatingusing leukocyte membranes led to an approximately twofoldincrease in particle density in the tumor

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsit is predictable that the research of NPs mimicking immunecells might be effective in brain-associated disorders and willreceive a stimulus in this direction in the next years

6 Factors Affecting NPs Brain Drug Delivery

61 NPs Diffusion inside the Brain Parenchyma While thisfactor is likely not particularly relevant when brain drugdelivery is sought after it could be very important when thepassage of the BBBbyNPs is looked for since the extracellularspace (ECS) of the brain parenchyma could limit their diffu-sion or even preclude their entrance into the brainThe abilityto achieve brain penetration with larger NPs is expected toallow more uniform longer lasting and effective delivery ofdrugs within the brain and may in particular find practicein the treatment of brain tumors stroke neuroinflammationand other brain diseases where the BBB is compromised orwhere local delivery strategies are feasible

Today it is well established that the ECSoccupies a volumefraction of between 15 and 30 in normal adult brain tissuewith a typical value of 20 and that this falls to 5 duringglobal ischemia [151 152]

It is less obvious what the true size of the spaces betweencells is Small molecules such as inulin and sucrose diffusethrough the ECS with a decreased diffusion coefficient withrespect to water suggesting the existence of limitation to theirmovements [153]

Possible sources of the limitations to the diffusing mol-ecules are (a) the presence of cellular obstructions (b) trap-ping of molecules in dead-space microdomains (c) a viscousdrag imposed by themacromolecules that compose the extra-cellular matrix or drag arising from the walls of the channelswhen molecules are large such as in the case of NPs(d) transient binding to cell membranes or extracellularmatrix (e) nonspecific interaction with negative charges onthe extracellular matrix when the diffusing molecule hasadequate charge density

A different type of model was proposed by Thorne andNicholson [154] to explain the higher tortuosity experimen-tally measured for larger substances such as dextran andespecially large synthetic quantum dot nanocrystals in the invivo rat cortex It was assumed that the quantum dots with ahydrodynamic diameter of 35 nm were close to the averagewidth of the ECS and depending on whether a planar ortubularmodel was adopted the estimated ECSwidth was 38ndash64 nm

In counter tendency to Thorne and Nicholson [154]Nance et al [155] report that NPs as large as 114 nm indiameter diffused within the human and rat brain only ifthey were densely coated with PEG Using these minimally

adhesive PEG-coated NPs they estimated that human braintissue ECS has some pores larger than 200 nm and that morethan one-quarter of all pores are ge100 nm

In addition to ECS in CNS there is also much interest inthe possibility that perivascular spaces fluid-filled channelssurrounding arteries arterioles veins venules and possiblyevenmicrovessels offer potential pathways for rapid flow intoand out of brain parenchyma Measurements of perivascularspace widths in mammals suggest that their typical dimen-sions may be at least 2 orders of magnitude greater thanthe neocortical ECS width (eg arteriole perivascular spaceshave been reported in the range of 5ndash10 120583m or larger (inrodents and humans))

62 Effect of Protein Corona Different physicochemicalproperties not only size may determine the ability ofnanoparticles to reach the brain The situation is furthercomplicated by the formation of a so-called ldquocoronardquo ofbiomolecules on the surfaces of nanoparticles the composi-tion of which may vary depending on the route of exposureand on the physicochemical surface properties of NPs Theacquisition of a corona of biomolecules on the surface ofNPs may also determine whether NPs are able to cross fromone compartment to another and whether they are taken upeffectively by cells or not [156]

In practical situations in which nanoparticles interactwith living organisms the nanoparticle surfaces are initiallyexposed to a biological fluid such as blood dependingon the route of administration For instance NPs injectedintravenously would be exposed to blood plasma containingan excess of proteins and many other complex biomoleculeswhich bind competitively with the surface of the nanoparti-cles

The current idea is that ldquobarerdquo nanoparticles do notexist in vivo because they are immediately modified bythe adsorption of blood proteins with higher affinities forthe particle surface forming a more or less tightly boundlayer (the so-called hard corona) and a weakly associatedmobile layer (the so-called soft corona) When this issue wasinvestigated it has been found that typical coronas containa limited number and types of molecules gathered fromthe blood in spite of the fact that biological fluids containthousands of proteins [157] Moreover it should be noted thatthe corona may also play a role in other undesirable effectsof NPs in living systems such as complement activation andblood clotting and may not necessarily play a role only incellular uptake

It should be pointed out that none of the in vitro exper-iments conducted to study the process of NPs translocationto the brain takes into account the surface modification ofNPs inside the blood and how can this affect the crossingof the BBB This issue needs much further investigationMoreover NPs once internalized by endothelial BBB cellsthey may also exit towards the brain covered with differentbiomolecules depending on that they have undergone endo-cytosistranscytosisexocytosis and thus exert additionaleffects (eg toxicity) on neuron Also this issue has not yetbeen investigated

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

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[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

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[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

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14 ISRN Biochemistry

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ISRN Biochemistry 15

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16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

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[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

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[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

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[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

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[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

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BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

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Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

6 ISRN Biochemistry

palsy providing opportunities for clinical translation in thetreatment of neuroinflammatory disorders in humans

5 How NPs Can Cross the BBB

Many medicines are not able to reach the brain due to thelack of drug-specific transport systems through the BBBThedevelopment of new strategies based on NPs to enhance thebrain drug delivery is of great importance in the therapy anddiagnosis of CNS diseases and it is based on the interactionsbetween NPs and the BBB and on their intracellular trafficpathways

51 Crossing the BBB without Functionalization Althoughalmost all nanomaterials fall into the class of BBB imper-meable some exceptions have been reported in recent yearsFor instance gold and silica NPs have been shown to reachthe brain and accumulate in neurons even in the absenceof any specific functionalization with a mechanism thatsubstantially is still unknown In the case of silica the resultsindicated that NPs administered to rodents via intranasalinstillation entered into the brain and especially depositedin the striatum [52] In the case of gold NPs precise particledistribution in the brain was studied ex vivo by X-ray micro-tomography confocal laser andfluorescencemicroscopy [53]The authors found that the particles mainly accumulate inthe hippocampus thalamus hypothalamus and the cerebralcortex The same holds true for Titanium dioxide NPs thatwere found to cross the mice BBB particularly when smallerthan 40 nm [54]

52 Adsorptive-Mediated Transcytosis The concept of ad-sorptive-mediated transcytosis through the BBB was orig-inally suggested by the observation that cationic proteinscan bind the endothelial cell surface but also cross the BBB[55] The mechanism applied to NPs is based on the properfunctionalization of their surface allowing electrostatic inter-action with the luminal surface of BBB Given the presenceof negative charges on endothelial cells [56] this interactioncan be promoted by conferring a positive charge to the NPssurface

Different procedures can be followed to realize this issueA first possibility is to build up NPs made of componentsthat are bearing a positive charged at physiological pH (74)This is the case of nanosized vesiclesmade of bolaamphiphilicmolecules (amphiphilic molecules that have hydrophilicgroups at both ends of an hydrophobic chain) that followingintravenous administration to mice showed a marked accu-mulation of their encapsulated fluorescent cargo whereasnonencapsulated probe was detected only in peripheraltissues but not in the brain [57] In another investigation Jinet al [58] used SLN made with lipids extracted from depro-teinated lipoproteins and enriched with cationic cholesterylhydrochloride and phosphatidyl-ethanolamine The authorsafter intravenous administration of such cationic NPs for thedelivery of siRNA inhibiting c-Met expression suppressedtumor growth without evident signs of systemic toxicity inan orthotopic xenograft tumor mice model of glioblastoma

A second possibility is to functionalize the NPs surfacewith positively charged biomolecules combining their physic-ochemical features with biological activity This is the caseof cell-penetrating peptides (eg TAT peptides derived fromHIV gH625 derived from Herpes simplex virus type 1) andcationic proteins (eg albumin) [59] that have been exten-sively used for NPs decoration facilitating the BBB passageof drugs [60] As for example Rao et al [61] after admin-istration of ritonavir via TAT-conjugated NPs demonstratedapproximately an 800-fold higher level of drug in the brainwhen compared to that with free drug with a remarkableenhancement of drug delivery The authors suggested thatTAT-conjugated polymeric NPs are first mobilized in thebrain vasculatures then transported to the brain parenchymawhere they continue to release the drug

Polymeric micelles having TAT molecules on the surfacewere successfully fabricated also to incorporate antibioticsand were able to cross the BBB [62] In another study Xuet al [63] showed efficacy of TAT-polymeric NPs for thetreatment of C albicansmeningitis in rabbits Similar resultsare reported using another family of cell-penetrating peptides(SynB peptides RGGRLSYSRRRFSTSTGR) that were able toincrease drug permeability across a cocultured BBB modeldoubling drug transport in vivo in healthy mice [64]

Since the effect of cell-penetrating peptides could beinvalidated by the rapid systemic clearance of functionalizedNPs due to their positive charge in a study dedicated toinvestigate this issue Xia et al [65] utilized penetratin apeptide derived from Antennapedia protein (Drosophila)with relatively lower content of basic amino acids to func-tionalize poly(ethylene glycol)-poly(lactic acid) (PLGA)NPsfluorescently labeled with coumarin-6 and detected anincrease of fluorescence in the rodent brain with respect tounfunctionalized NPs

Xia et al [65] also combined the use of cell-penetratingpeptide to coumarin-6-loaded NPs for intranasal adminis-tration The amount of fluorescent probe detected in the ratcerebrum and cerebellum was found to be more than 2-foldcompared to that of coumarin carried by unfunctionalizedNPs Brain distribution analysis suggested that NPs afterintranasal administration could be delivered to the centralnervous system along both the olfactory and trigeminalnerves pathways

The efficacy of cationic albumin to functionalize andpromote NPs-carried drug delivery to the brain has beenrepeatedly reported [66 67]Theproperty of cationic proteinsto efficiently penetrate cells raises the question of the potentialtoxicity and immunogenicity of these proteins The possi-ble toxic effects include a generalized increase in vascularpermeability since breakdown of BBB permeability andother vascular beds has been observed following intravenousinjection of large amounts of cationic proteins but has notbeen seen when moderate amounts of these substances wereadministered [68]

53 Receptor-MediatedTranscytosis Oneof themost recentlyapplied strategies for drug delivery across the BBB endo-thelium using functionalized NPs is the one exploiting

ISRN Biochemistry 7

the transcytosis physiological mechanism of transport ofmacromolecules relying on the presence of specific recep-tors on the luminal surface of cells Transcytosis is theprocess by which extracellular cargo internalized at oneplasma membrane domain (eg apical) of a polarized cell istransported via vesicular intermediates to the controlateralplasma membrane (eg basolateral) As for example insulintransferrin apolipoproteins and 2-macroglobulin are someof the proteins that reach the brain following the path acrossendothelial cells

The rationale for exploiting this strategy with NPs is thatthe existing cellular mechanisms handling macromolecularcargoes may fit also to transport NPs after their functional-ization to interact with the same receptors

Transcytosis in endothelial cells starts with internal-ization of extracellular cargo into the cell by vesicularcarriers The cargo is subsequently processed via differentpathways to appropriate intracellular organelles and recycleddegraded or transcytosed to the contralateral side Strongmorphological and biochemical evidence suggest that thetwo membranes apical and basolateral are interconnectedvia vesicular intermediates involving multivesicular bodiesor a system of endosomal vacuoles and tubule vesiclesPhosphoinositide 3-kinase an enzyme increasingly demon-strated to play an important regulatory role inmany vesiculartrafficking events also appears to regulate transcytotic trafficbetween the two endosomal compartments

Transcytosis in endothelial cells starts with uptake eitherthrough clathrin-coated pits by caveolae or caveolae-likemembrane domains [69] that will be described here below

The first step of internalization through clathrin-mediated endocytosis is the binding of a ligand to a specificcell surface receptor This results in the clustering of theligand-receptor complexes in coated pits on the plasmamembrane which are formed by the assembly of cytosoliccoat proteins the main assembly units being clathrin whichform a polygonal lattice in the surface of the membrane andadaptor protein complexes which mediate the assembly ofthe clathrin lattice on the membrane The coated pits theninvaginate and pinch off from the plasma membrane to formintracellular clathrin-coated vesicles The clathrin coat thendepolymerizes resulting in early endosomes which fusewith each other or with other preexisting endosomes to formlate endosomes that further fuse with lysosomes Vesiculartrafficking after CME is controlled by the action of smallGTPases the Rab proteins

The second mechanisms internalization (caveolar) hasbeen clarified following the trafficking of some viruses thatuse caveolae to gain entry into the cells Caveolae aresmall flask-shaped invaginations of the plasma membranewith a size of about 50ndash60 nm that are rich in cholesteroland sphingolipids Viruses initially associate with the cellmembrane and then become trapped in relatively stationarycaveolae The subsequent intracellular uptake of caveolaeleads to intracellular organelles that are distinct from classicendosomes the presence of the protein caveolin in theseorganelles gave rise to the name caveosomes In contrast tothe dynamic nature of endosomes caveolae are highly stableand are only slowly internalized Another major difference is

that the caveolar uptake does not lead to a decrease of pHand to a degradative pathway of their cargo as in endoso-mallysosomal pathway

It is clear that the different pathways of NPs internal-ization affect their delivery to different intracellular com-partments and may affect their final destination To obtaininsight into the properties of drug delivery vehicles thatdirect their intracellular processing in brain endothelial cellsthe intracellular traffic of fixed-size nanoparticles in anin vitro BBB model as a function of distinct nanoparticlesurface modifications has been investigated Previous obser-vations [70] that latex particles with a diameter ge500 nm areinternalized by nonphagocytic B16 cells through caveolaewhereas particles up to 200 nm in diameter are efficientlytaken up via clathrin-mediated endocytosis were succes-sively confirmed with Silica-Hydroxyl NPs on immortalizedhuman brain capillary endothelial cell cultures [71] In theinvestigation of Georgieva et al [71] 500 nm particles wereused uncoated surface functionalized with cationic polymerpolyethyleneimine (PEI) or with prion protein The resultssuggested that uncoated NPs are internalized through cave-olae nanoparticles carrying a net cationic charge accom-plished by PEI followed an adsorptive endocytotic routeand particles surface-modified with prion protein followedreceptor-mediated endocytotic route Therefore the authorsconcluded that the NPs intracellular pathway is dictated bythe particle surface characteristic for a given size Mostinterestingly they found that the transcytotic potential ishigher for the receptor-mediated and caveolar pathways andlower for the adsorptive-mediated

However the enhancement of brain delivery obtainedwith drug-loaded NPs exploiting receptor- or caveolar-mediated transcytosis is currently quantitatively limited incomparison with the free drug Consequently also its clinicalrelevance is still scarce If we compare the hydrodynamicsize of most physiological proteins with that of NPs we areconfronting objects in the order of 5ndash10 nm size with thosethat in most cases are in the order of tenths of nanome-ters and commonly reach 100 nm and more Therefore itis conceivable that the transcytotic traffic may become abottleneck when transporting NPs It is also predictablethat smaller size NPs closer to the size of physiologicalmolecules would be facilitated to enter the same intracellu-lar transport pathways Following the strategy of receptor-mediated transport NPs made of gold PLGA chitosanPAA dendrimers and liposomes have been functionalizedimproving the delivery of drugs such as caspase inhibitorsendomorphin tamoxifen and tramadol and throwing thebasis for treatment of neurological diseases [72ndash79]

Exploring and targeting new receptors that could beutilized for receptor-dependent endocytosis are likely toprovide more efficient systems of brain drug delivery mainlybecause these uptakemechanisms are relatively unaffected bylysosomal degradation

531 Lipoprotein Receptors Apolipoprotein E (apoE) is a 34-kDa protein constituent of both very-low-density lipopro-tein (VLDL) and high-density lipoprotein (HDL) which

8 ISRN Biochemistry

transports cholesterol and other lipids in the plasma and inthe CNS [80 81] The lipoproteins complexes can be takenup in the brain through the recognition of apoE by specificreceptors at the BBB which include the low-density lipopro-tein receptor (LDLR) and the LDLR-related protein (LRP)

Taking into consideration that LRP has been reported tobe highly expressed on endothelial brain microvessels [82]receptor-mediated transcytosis using NPs functionalized tobind this target has been exploited in several ways

First by exploiting the preferential absorption of ApoEon some types of NPs when in serum This feature has beendescribed for PBCA NPs coated with polysorbate 80 indeeddisplaying the ability to cross the BBB in vivo in animalmodels [83ndash85] and for PEGylated PHDCA NPs able topenetrate into brain endothelial cells in vitro [86]

Taking advantage of such opportunity the formation ofa stable ApoE decoration of NPs surface by covalent bindinghas been utilized to functionalize albumin-NPs or liposomesthat showed the capacity of enhancing BBB passage in vivo inrodent models [87ndash89]

It should be questioned whether other apolipoproteinsmay be employed for NPs functionalization to confer onthem the ability to enhance brain drug delivery In order toanswer this question in an investigation of Kreuter et al [90]PBCA NPs loaded with dalargin or loperamide were coatedwith different apo-lipoproteins AII B CII E or J coatedor not with polysorbate 80 and then injected in mice andthe drug effect on CNS was evaluated The results showedthat only NPs coated with apolipoprotein B or E were able toachieve an antinociceptive effect This effect was significantlyhigher after polysorbate-precoating and apolipoprotein B orE-overcoating [90]

The region of apoE that is critical for interaction with theLDL receptor resides between amino acid residues 140 and160 Several studies with synthetic peptides have investigatedthe structural features of the LDLR-binding sequence ofApoE [91 92]

Laskowitz et al [81] derived an apoE-mimetic pep-tide from amino acids 133ndash149 named COG133 (LRVR-LASHLRKLRKRLL) which retains its biological activity invitro and in vivoThis capacity is displayed also by a fragmentof 26 aa from ApoE4 [93]

It has also been reported that the tandemdimer (141ndash155)2

is recognized by the LDLR in contrast to themonomeric pep-tide (141ndash155) [94] Also a shorter sequence of this peptide thetandem dimer (141ndash150)

2 retains this ability [95] Probably

as a consequence of these observations sterically stabilizedliposomeswere functionalized onlywithApoE tandemdimerpeptide (141ndash150)

2 but not with the monomer and were

shown to be efficiently taken up by rat brain capillaryendothelial cells [96] Interestingly in spite of the theoreticalpremises based on receptor-mediated endocytosis liposomestagged with (141ndash150)

2were nonselectively internalized into

cultured BBB cells and clathrin- or caveolin-dependentendocytosis was not demonstrable [97]

However in a successive investigation the ApoE-derivedpeptide monomer 141ndash150 was utilized by Re et al [98]in comparison with the dimer for the functionalization ofliposomes entrapping a radioactive derivative of curcumin

The investigation showed a higher uptake of the drug byhuman endothelial cells and an enhancement of permeabilityof the drug across an in vitromodel of the BBBmade with thesame cells when using monomer-functionalized liposomes

Apart from the amino acid sequence other factors mayaffect the cellular uptake of these peptides [98] These factorsinclude the type of peptide its cationic nature its mode ofexposure to the cell surface the nature of the cargo and thechemical linkage between the peptide and the cargo otherthan the peptide surface density on the cellular uptake ofnanoparticles [98 99]

Finally also Angiopep-2 a ligand of LRP possesses a highbrain penetration capability in both in vitro model of theBBB and in situ brain perfusion in mice [100] PEG-PAMAMdendrimers functionalized using this peptide resulted ina high accumulation of a delivered gene into brain afterintravenous administration into mice [101] moreover alsofunctionalized polymeric NPs and carbon nanotubes (CNT)have been produced showing the ability to reach gliomatumors in mice [102 103]

532 Transferrin Receptor (TfR) The transferrin receptor(TfR) is the most widely studied receptor for BBB targetingTfR is a transmembrane glycoprotein consisting of twolinked 90-kDa subunits each one binding a transferrinmolecule The receptor is highly expressed on immature ery-throid cells placental tissue and rapidly dividing cells bothnormal and malignant [104] Furthermore it is expressedon hepatocytes and endothelial cells of the BBB The role ofthe receptor is the regulation of cellular uptake of iron viatransferrin a plasma protein which transports iron in thecirculation Cellular uptake starts with the binding of trans-ferrin to the transferrin receptor followed by endocytosis[105]

Iron-bound transferrin has a high affinity for the TfRtherefore it has been used with success as a ligand for func-tionalization and targeting of liposomes to cultured brainendothelial cells [106 107] However it is likely that thatNPs decorated with transferrin would not be performantin vivo since transferrin receptors are almost saturated inphysiological conditions because of the high circulatinglevels of endogenous protein [108] Nevertheless successfulbrain targeting using transferrin as a targeting ligandhas beenaccomplished in vivo [109 110] Concerning the specificity oftransferrin a comparative study has been carried out betweentransferrin or lactoferrin a multifunctional protein of thetransferrin family widely represented in various secretoryfluids such as milk [111] Lalani et al [112] compared in vivodistribution in mice of PLGA NPs surface modified with thetwo proteins and showed a better performance to reach thebrain in the case of lactoferrin

In order to avoid the competition with endogenous trans-ferrin circulating in blood the use of monoclonal antibodies(mAbs) directed against transferrin receptors on the BBB hasbeen suggested because they recognize different epitopes onthe receptor [113] For instance OX26 8D3 and R17217 mAbbind to TfR and have also been shown to undergo receptor-mediated transcytosis

ISRN Biochemistry 9

Among these it is still debated which mAb is the bestperforming to be used for the decoration of NPs surface Themostwell known isOX26 an antibody directed against the ratTfR that has been successfully used in many brain targetingstudies in vivo [114] and also in vitro using BBB cellularmodels [115] However Lee et al [116] have shown that theOX26monoclonal antibody is not an effective brain targetingmolecule in mice Moreover they demonstrated that othertwo monoclonal antibodies 8D3 and RI7217 directed againstthe mouse TfR had a higher permeability of the mouseBBB in vivo with respect to the brain uptake of the OX26antibody which was negligible Additionally they showedthat RI7217wasmore selective for the brain than 8D3 becausethis antibody was less taken up by the liver and kidney Ithas been shown that RI7217 covalently coupled to humanserum albumin is able to transport loperamide across theBBB [110] More recently it has been shown that also thechemical linkage of anti-TfR on the NPs surface could affectthe crossing of BBB in vitro [117] The authors comparedliposomes covalently coupled with mAbs (obtained by react-ing thiolatedmAbs to phosphatidyl-ethanolaminemaleimideinserted in the liposome bilayer) with liposomes decoratedwith biotinylated mAbs via an avidin bridge The Authorsfound an higher cellular uptake and permeability across anin vitro BBB model made of immortalized human braincapillary endothelial cells of the liposomes covalently coupledwith mAbs suggesting that the covalent ligation could bepreferentially chosen for NPs decoration

54 Retrograde Transport Transsynaptic retrograde trans-port could enable some types of nanocarriers to travel fromperipheral nerve terminals to neuronal cell bodies in the CNS[118] Studies in this regard have shown that NPs modifiedwith PEI and other polyplexes display active retrogradetransport along neurites but are unable to mediate efficientbiological actions upon reaching the neuronal body [119]

55 BBB Breakdown BBB breakdown occurs in neuroin-flammatory diseases [120] NPs can transiently and reversiblyopen the tight junctions located at the BBB and other sitesthus increasing their paracellular permeability [121 122]In particular blood-brain barrier disruption therapy is anintensive effectiveway of sendingmedication to brain tumors[123]

Nevertheless it is known that tight junctions can beopened only to a limited extent [124] thus only NPs smallerthan about 20 nm can use this pathway to penetrate into thebrain through the BBB

56 Exploiting MonocyteMacrophage Infiltration in the CNSMonocytemacrophage infiltration in the CNS plays a keyrole in neuroinflammation as well as in lesion developmentand brain injury in neurological diseases such as multiplesclerosis (MS) and stroke [124ndash126] Knowledge of activephases of cell infiltration during CNS disorders is importantbecause anti-inflammatory treatments can target cell adhe-sion molecules and chemokines guiding cellular trafficking[127] The monocyte infiltration through the BBB is also

widely believed to play an important role in HIV infectionof the CNS The blood-brain barrier appears unaltered untilthe late stage of HIV encephalitis HIV flux that movestoward the brain thus relies on hijacking with immune-activated leukocytes mainly monocytesmacrophages fromthe periphery [128]

In this paper BBB crossing by immune-activated macro-phages appears to suggest possible strategies for future ther-apeutic developments employing NPs This strategy couldbe realized at least in two ways (1) by embedding NPs intoactivated monocytes used as Trojan horses to reach the brain(2) by designing NPs mimicking activated monocytes

561 Trojan Monocytes for NPs Delivery to the Brain Nano-particulate drug delivery systems have been used to avoidthe RES clearance and achieve longer circulation time forenhanced tissue uptake However the enhancing of NPsphagocytosis by monocytes can be considered as an uncon-ventional approach to deliver NPs-loaded drugs to thebrain After phagocytosis of NPs monocytes just like Trojanhorses may transport their cargo into the brain Aferganet al [129] taking this approach embedded serotonin aBBB impermeable neurological drug into negatively chargedliposomes and analyzed brain uptake in rats and rabbitsThe performance of liposomal serotonin was significantlybetter leading to two-fold higher drug concentration inbrain than the free drug Since treatment of animals byalendronate resulted with inhibition of monocytes but not ofneutrophils andwith no brain delivery the authors suggestedthat monocytes are the main transporters of liposomes tothe brain In spite of the fact that the clinical relevance ofthis investigation is limited the Trojan monocyte approachprovides a new possibility of more effective treatment ofbrain-associated inflammatory disorders including multiplesclerosis and Alzheimerrsquos disease which are characterizedwith increased passage of immune cells across the BBB[130]

In other examples in order to improve the delivery ofcontrast agents to the brain iron oxide NPs administeredintravenously in vivo have been shown to detect activatedmacrophage infiltration in multiple sclerosis either in theCNS of humans [131 132] or rodentmodel [133ndash137] in strokeeither in human [138 139] or animal brain ischemia [140ndash143] in human or murine intracranial tumors [144 145] inEAE [146ndash148] or in an ischemiareperfusion long-lived ratmodel [149]

562 NPs Mimicking Activated Monocytes The therapeu-tic efficacy of drug-loaded NPs systemically administereddepends on their ability to evade the immune system tocross the biological barriers of the body and to localizeat target tissues Parodi et al [150] show that nanoporoussilicon particles can successfully perform all these actionswhen they are coated with cellular membranes purifiedfrom leukocytes avoiding being cleared by the immune sys-tem Furthermore they can communicate with endothelialcells through receptor-ligand interactions and transport andrelease a doxorubicin payload across an inflamed endothelial

10 ISRN Biochemistry

barrier in vitro Also the accumulation of coated NPs inmice inoculated with murine B16 melanoma was enhancedcompared with that of non coated NPs Particle coatingusing leukocyte membranes led to an approximately twofoldincrease in particle density in the tumor

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsit is predictable that the research of NPs mimicking immunecells might be effective in brain-associated disorders and willreceive a stimulus in this direction in the next years

6 Factors Affecting NPs Brain Drug Delivery

61 NPs Diffusion inside the Brain Parenchyma While thisfactor is likely not particularly relevant when brain drugdelivery is sought after it could be very important when thepassage of the BBBbyNPs is looked for since the extracellularspace (ECS) of the brain parenchyma could limit their diffu-sion or even preclude their entrance into the brainThe abilityto achieve brain penetration with larger NPs is expected toallow more uniform longer lasting and effective delivery ofdrugs within the brain and may in particular find practicein the treatment of brain tumors stroke neuroinflammationand other brain diseases where the BBB is compromised orwhere local delivery strategies are feasible

Today it is well established that the ECSoccupies a volumefraction of between 15 and 30 in normal adult brain tissuewith a typical value of 20 and that this falls to 5 duringglobal ischemia [151 152]

It is less obvious what the true size of the spaces betweencells is Small molecules such as inulin and sucrose diffusethrough the ECS with a decreased diffusion coefficient withrespect to water suggesting the existence of limitation to theirmovements [153]

Possible sources of the limitations to the diffusing mol-ecules are (a) the presence of cellular obstructions (b) trap-ping of molecules in dead-space microdomains (c) a viscousdrag imposed by themacromolecules that compose the extra-cellular matrix or drag arising from the walls of the channelswhen molecules are large such as in the case of NPs(d) transient binding to cell membranes or extracellularmatrix (e) nonspecific interaction with negative charges onthe extracellular matrix when the diffusing molecule hasadequate charge density

A different type of model was proposed by Thorne andNicholson [154] to explain the higher tortuosity experimen-tally measured for larger substances such as dextran andespecially large synthetic quantum dot nanocrystals in the invivo rat cortex It was assumed that the quantum dots with ahydrodynamic diameter of 35 nm were close to the averagewidth of the ECS and depending on whether a planar ortubularmodel was adopted the estimated ECSwidth was 38ndash64 nm

In counter tendency to Thorne and Nicholson [154]Nance et al [155] report that NPs as large as 114 nm indiameter diffused within the human and rat brain only ifthey were densely coated with PEG Using these minimally

adhesive PEG-coated NPs they estimated that human braintissue ECS has some pores larger than 200 nm and that morethan one-quarter of all pores are ge100 nm

In addition to ECS in CNS there is also much interest inthe possibility that perivascular spaces fluid-filled channelssurrounding arteries arterioles veins venules and possiblyevenmicrovessels offer potential pathways for rapid flow intoand out of brain parenchyma Measurements of perivascularspace widths in mammals suggest that their typical dimen-sions may be at least 2 orders of magnitude greater thanthe neocortical ECS width (eg arteriole perivascular spaceshave been reported in the range of 5ndash10 120583m or larger (inrodents and humans))

62 Effect of Protein Corona Different physicochemicalproperties not only size may determine the ability ofnanoparticles to reach the brain The situation is furthercomplicated by the formation of a so-called ldquocoronardquo ofbiomolecules on the surfaces of nanoparticles the composi-tion of which may vary depending on the route of exposureand on the physicochemical surface properties of NPs Theacquisition of a corona of biomolecules on the surface ofNPs may also determine whether NPs are able to cross fromone compartment to another and whether they are taken upeffectively by cells or not [156]

In practical situations in which nanoparticles interactwith living organisms the nanoparticle surfaces are initiallyexposed to a biological fluid such as blood dependingon the route of administration For instance NPs injectedintravenously would be exposed to blood plasma containingan excess of proteins and many other complex biomoleculeswhich bind competitively with the surface of the nanoparti-cles

The current idea is that ldquobarerdquo nanoparticles do notexist in vivo because they are immediately modified bythe adsorption of blood proteins with higher affinities forthe particle surface forming a more or less tightly boundlayer (the so-called hard corona) and a weakly associatedmobile layer (the so-called soft corona) When this issue wasinvestigated it has been found that typical coronas containa limited number and types of molecules gathered fromthe blood in spite of the fact that biological fluids containthousands of proteins [157] Moreover it should be noted thatthe corona may also play a role in other undesirable effectsof NPs in living systems such as complement activation andblood clotting and may not necessarily play a role only incellular uptake

It should be pointed out that none of the in vitro exper-iments conducted to study the process of NPs translocationto the brain takes into account the surface modification ofNPs inside the blood and how can this affect the crossingof the BBB This issue needs much further investigationMoreover NPs once internalized by endothelial BBB cellsthey may also exit towards the brain covered with differentbiomolecules depending on that they have undergone endo-cytosistranscytosisexocytosis and thus exert additionaleffects (eg toxicity) on neuron Also this issue has not yetbeen investigated

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

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[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

[12] W M Pardridge ldquoDrug transport across the blood-brainbarrierrdquo Journal of Cerebral Blood Flow amp Metabolism vol 32no 11 pp 1959ndash1972 2012

[13] A Minn S Leclerc J M Heydel et al ldquoDrug transport into themammalian brain the nasal pathway and its specific metabolicbarrierrdquo Journal of Drug Targeting vol 10 no 4 pp 285rndash296r2002

[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

[23] L Martin-Banderas M A Holgado J L Venero J Alvarez-Fuentes and M Fernadez-Arealo ldquoNanostructures for drugdelivery to the brainrdquoCurrentMedicinal Chemistry vol 148 no34 pp 5303ndash5321 2011

[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

[26] T Ishii T Asai D Oyama et al ldquoTreatment of cerebralischemia-reperfusion injury with PEGylated liposomes encap-sulating FK506rdquo FASEB Journal vol 27 no 4 pp 1362ndash13702013

[27] A Lindqvist J Rip P J Gaillard S Bjorkman and MHammarlund-Udenaes ldquoEnhanced brain delivery of the opioidpeptide DAMGO in glutathione PEGylated liposomes amicro-dialysis studyrdquoMolecular Pharmacology 2012

[28] A Orthmann R Zeisig R Suss D Lorenz M Lemm andI Fichtner ldquoTreatment of experimental brain metastasis withMTO-liposomes impact of fluidity and LRP-targeting on thetherapeutic resultrdquo Pharmaceutical Research vol 29 no 7 pp1949ndash1959 2012

[29] M T da Cruz S Simoes and M C de Lima ldquoImprovinglipoplex-mediated gene transfer into C6 glioma cells andprimary neuronsrdquo Experimental Neurology vol 187 no 1 pp65ndash75 2004

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[31] A Molinari M Colone A Calcabrini et al ldquoCationic lipo-somes loaded with m-THPC in photodynamic therapy for

14 ISRN Biochemistry

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[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

[36] B Mishra B B Patel and S Tiwari ldquoColloidal nanocarriersa review on formulation technology types and applicationstoward targeted drug deliveryrdquo Nanomedicine vol 6 no 1 ppe9ndashe24 2010

[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

[40] S Md M Ali S Baboota et al ldquoPreparation characteri-zation in vivo biodistribution and pharmacokinetic studiesof donepezil-loaded PLGA nanoparticles for brain targetingrdquoDrug Development and Industrial Pharmacy 2013

[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

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[44] R Pandey and G K Khuller ldquoOral nanoparticle-based antitu-berculosis drug delivery to the brain in an experimental modelrdquoJournal of Antimicrobial Chemotherapy vol 57 no 6 pp 1146ndash1152 2006

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[46] A V Kabanov E V Batrakova N S Melik-Nubarov et alldquoA new class of drug carriers micelles of poly(oxyethylene)-poly(oxypropylene) block copolymers as microcontainers for

drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

[50] L Albertazzi L Gherardini M Brondi et al ldquoIn vivo dis-tribution and toxicity of PAMAM dendrimers in the centralnervous system depend on their surface chemistryrdquo MolecularPharmacology vol 10 no 1 pp 249ndash260 2013

[51] S Kannan H Dai R S Navath et al ldquoDendrimer-basedpostnatal therapy for neuroinflammation and cerebral palsy ina rabbit modelrdquo Science Translational Medicine vol 4 no 130Article ID 130ra46 2012

[52] J Wu C Wang J Sun and Y Xue ldquoNeurotoxicity of silicananoparticles brain localization and dopaminergic neuronsdamage pathwaysrdquoACSNano vol 5 no 6 pp 4476ndash4489 2011

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[54] Y Ze L Zheng X Zhao et al ldquoMolecular mechanism oftitanium dioxide nanoparticles-induced oxidative injury in thebrain of micerdquo Chemosphere 2013

[55] R D Broadwell ldquoTranscytosis of macromolecules through theblood-brain barrier a cell biological perspective and criticalappraisalrdquo Acta Neuropathologica vol 79 no 2 pp 117ndash1281989

[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

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Nucleic AcidsJournal of

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Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

ISRN Biochemistry 7

the transcytosis physiological mechanism of transport ofmacromolecules relying on the presence of specific recep-tors on the luminal surface of cells Transcytosis is theprocess by which extracellular cargo internalized at oneplasma membrane domain (eg apical) of a polarized cell istransported via vesicular intermediates to the controlateralplasma membrane (eg basolateral) As for example insulintransferrin apolipoproteins and 2-macroglobulin are someof the proteins that reach the brain following the path acrossendothelial cells

The rationale for exploiting this strategy with NPs is thatthe existing cellular mechanisms handling macromolecularcargoes may fit also to transport NPs after their functional-ization to interact with the same receptors

Transcytosis in endothelial cells starts with internal-ization of extracellular cargo into the cell by vesicularcarriers The cargo is subsequently processed via differentpathways to appropriate intracellular organelles and recycleddegraded or transcytosed to the contralateral side Strongmorphological and biochemical evidence suggest that thetwo membranes apical and basolateral are interconnectedvia vesicular intermediates involving multivesicular bodiesor a system of endosomal vacuoles and tubule vesiclesPhosphoinositide 3-kinase an enzyme increasingly demon-strated to play an important regulatory role inmany vesiculartrafficking events also appears to regulate transcytotic trafficbetween the two endosomal compartments

Transcytosis in endothelial cells starts with uptake eitherthrough clathrin-coated pits by caveolae or caveolae-likemembrane domains [69] that will be described here below

The first step of internalization through clathrin-mediated endocytosis is the binding of a ligand to a specificcell surface receptor This results in the clustering of theligand-receptor complexes in coated pits on the plasmamembrane which are formed by the assembly of cytosoliccoat proteins the main assembly units being clathrin whichform a polygonal lattice in the surface of the membrane andadaptor protein complexes which mediate the assembly ofthe clathrin lattice on the membrane The coated pits theninvaginate and pinch off from the plasma membrane to formintracellular clathrin-coated vesicles The clathrin coat thendepolymerizes resulting in early endosomes which fusewith each other or with other preexisting endosomes to formlate endosomes that further fuse with lysosomes Vesiculartrafficking after CME is controlled by the action of smallGTPases the Rab proteins

The second mechanisms internalization (caveolar) hasbeen clarified following the trafficking of some viruses thatuse caveolae to gain entry into the cells Caveolae aresmall flask-shaped invaginations of the plasma membranewith a size of about 50ndash60 nm that are rich in cholesteroland sphingolipids Viruses initially associate with the cellmembrane and then become trapped in relatively stationarycaveolae The subsequent intracellular uptake of caveolaeleads to intracellular organelles that are distinct from classicendosomes the presence of the protein caveolin in theseorganelles gave rise to the name caveosomes In contrast tothe dynamic nature of endosomes caveolae are highly stableand are only slowly internalized Another major difference is

that the caveolar uptake does not lead to a decrease of pHand to a degradative pathway of their cargo as in endoso-mallysosomal pathway

It is clear that the different pathways of NPs internal-ization affect their delivery to different intracellular com-partments and may affect their final destination To obtaininsight into the properties of drug delivery vehicles thatdirect their intracellular processing in brain endothelial cellsthe intracellular traffic of fixed-size nanoparticles in anin vitro BBB model as a function of distinct nanoparticlesurface modifications has been investigated Previous obser-vations [70] that latex particles with a diameter ge500 nm areinternalized by nonphagocytic B16 cells through caveolaewhereas particles up to 200 nm in diameter are efficientlytaken up via clathrin-mediated endocytosis were succes-sively confirmed with Silica-Hydroxyl NPs on immortalizedhuman brain capillary endothelial cell cultures [71] In theinvestigation of Georgieva et al [71] 500 nm particles wereused uncoated surface functionalized with cationic polymerpolyethyleneimine (PEI) or with prion protein The resultssuggested that uncoated NPs are internalized through cave-olae nanoparticles carrying a net cationic charge accom-plished by PEI followed an adsorptive endocytotic routeand particles surface-modified with prion protein followedreceptor-mediated endocytotic route Therefore the authorsconcluded that the NPs intracellular pathway is dictated bythe particle surface characteristic for a given size Mostinterestingly they found that the transcytotic potential ishigher for the receptor-mediated and caveolar pathways andlower for the adsorptive-mediated

However the enhancement of brain delivery obtainedwith drug-loaded NPs exploiting receptor- or caveolar-mediated transcytosis is currently quantitatively limited incomparison with the free drug Consequently also its clinicalrelevance is still scarce If we compare the hydrodynamicsize of most physiological proteins with that of NPs we areconfronting objects in the order of 5ndash10 nm size with thosethat in most cases are in the order of tenths of nanome-ters and commonly reach 100 nm and more Therefore itis conceivable that the transcytotic traffic may become abottleneck when transporting NPs It is also predictablethat smaller size NPs closer to the size of physiologicalmolecules would be facilitated to enter the same intracellu-lar transport pathways Following the strategy of receptor-mediated transport NPs made of gold PLGA chitosanPAA dendrimers and liposomes have been functionalizedimproving the delivery of drugs such as caspase inhibitorsendomorphin tamoxifen and tramadol and throwing thebasis for treatment of neurological diseases [72ndash79]

Exploring and targeting new receptors that could beutilized for receptor-dependent endocytosis are likely toprovide more efficient systems of brain drug delivery mainlybecause these uptakemechanisms are relatively unaffected bylysosomal degradation

531 Lipoprotein Receptors Apolipoprotein E (apoE) is a 34-kDa protein constituent of both very-low-density lipopro-tein (VLDL) and high-density lipoprotein (HDL) which

8 ISRN Biochemistry

transports cholesterol and other lipids in the plasma and inthe CNS [80 81] The lipoproteins complexes can be takenup in the brain through the recognition of apoE by specificreceptors at the BBB which include the low-density lipopro-tein receptor (LDLR) and the LDLR-related protein (LRP)

Taking into consideration that LRP has been reported tobe highly expressed on endothelial brain microvessels [82]receptor-mediated transcytosis using NPs functionalized tobind this target has been exploited in several ways

First by exploiting the preferential absorption of ApoEon some types of NPs when in serum This feature has beendescribed for PBCA NPs coated with polysorbate 80 indeeddisplaying the ability to cross the BBB in vivo in animalmodels [83ndash85] and for PEGylated PHDCA NPs able topenetrate into brain endothelial cells in vitro [86]

Taking advantage of such opportunity the formation ofa stable ApoE decoration of NPs surface by covalent bindinghas been utilized to functionalize albumin-NPs or liposomesthat showed the capacity of enhancing BBB passage in vivo inrodent models [87ndash89]

It should be questioned whether other apolipoproteinsmay be employed for NPs functionalization to confer onthem the ability to enhance brain drug delivery In order toanswer this question in an investigation of Kreuter et al [90]PBCA NPs loaded with dalargin or loperamide were coatedwith different apo-lipoproteins AII B CII E or J coatedor not with polysorbate 80 and then injected in mice andthe drug effect on CNS was evaluated The results showedthat only NPs coated with apolipoprotein B or E were able toachieve an antinociceptive effect This effect was significantlyhigher after polysorbate-precoating and apolipoprotein B orE-overcoating [90]

The region of apoE that is critical for interaction with theLDL receptor resides between amino acid residues 140 and160 Several studies with synthetic peptides have investigatedthe structural features of the LDLR-binding sequence ofApoE [91 92]

Laskowitz et al [81] derived an apoE-mimetic pep-tide from amino acids 133ndash149 named COG133 (LRVR-LASHLRKLRKRLL) which retains its biological activity invitro and in vivoThis capacity is displayed also by a fragmentof 26 aa from ApoE4 [93]

It has also been reported that the tandemdimer (141ndash155)2

is recognized by the LDLR in contrast to themonomeric pep-tide (141ndash155) [94] Also a shorter sequence of this peptide thetandem dimer (141ndash150)

2 retains this ability [95] Probably

as a consequence of these observations sterically stabilizedliposomeswere functionalized onlywithApoE tandemdimerpeptide (141ndash150)

2 but not with the monomer and were

shown to be efficiently taken up by rat brain capillaryendothelial cells [96] Interestingly in spite of the theoreticalpremises based on receptor-mediated endocytosis liposomestagged with (141ndash150)

2were nonselectively internalized into

cultured BBB cells and clathrin- or caveolin-dependentendocytosis was not demonstrable [97]

However in a successive investigation the ApoE-derivedpeptide monomer 141ndash150 was utilized by Re et al [98]in comparison with the dimer for the functionalization ofliposomes entrapping a radioactive derivative of curcumin

The investigation showed a higher uptake of the drug byhuman endothelial cells and an enhancement of permeabilityof the drug across an in vitromodel of the BBBmade with thesame cells when using monomer-functionalized liposomes

Apart from the amino acid sequence other factors mayaffect the cellular uptake of these peptides [98] These factorsinclude the type of peptide its cationic nature its mode ofexposure to the cell surface the nature of the cargo and thechemical linkage between the peptide and the cargo otherthan the peptide surface density on the cellular uptake ofnanoparticles [98 99]

Finally also Angiopep-2 a ligand of LRP possesses a highbrain penetration capability in both in vitro model of theBBB and in situ brain perfusion in mice [100] PEG-PAMAMdendrimers functionalized using this peptide resulted ina high accumulation of a delivered gene into brain afterintravenous administration into mice [101] moreover alsofunctionalized polymeric NPs and carbon nanotubes (CNT)have been produced showing the ability to reach gliomatumors in mice [102 103]

532 Transferrin Receptor (TfR) The transferrin receptor(TfR) is the most widely studied receptor for BBB targetingTfR is a transmembrane glycoprotein consisting of twolinked 90-kDa subunits each one binding a transferrinmolecule The receptor is highly expressed on immature ery-throid cells placental tissue and rapidly dividing cells bothnormal and malignant [104] Furthermore it is expressedon hepatocytes and endothelial cells of the BBB The role ofthe receptor is the regulation of cellular uptake of iron viatransferrin a plasma protein which transports iron in thecirculation Cellular uptake starts with the binding of trans-ferrin to the transferrin receptor followed by endocytosis[105]

Iron-bound transferrin has a high affinity for the TfRtherefore it has been used with success as a ligand for func-tionalization and targeting of liposomes to cultured brainendothelial cells [106 107] However it is likely that thatNPs decorated with transferrin would not be performantin vivo since transferrin receptors are almost saturated inphysiological conditions because of the high circulatinglevels of endogenous protein [108] Nevertheless successfulbrain targeting using transferrin as a targeting ligandhas beenaccomplished in vivo [109 110] Concerning the specificity oftransferrin a comparative study has been carried out betweentransferrin or lactoferrin a multifunctional protein of thetransferrin family widely represented in various secretoryfluids such as milk [111] Lalani et al [112] compared in vivodistribution in mice of PLGA NPs surface modified with thetwo proteins and showed a better performance to reach thebrain in the case of lactoferrin

In order to avoid the competition with endogenous trans-ferrin circulating in blood the use of monoclonal antibodies(mAbs) directed against transferrin receptors on the BBB hasbeen suggested because they recognize different epitopes onthe receptor [113] For instance OX26 8D3 and R17217 mAbbind to TfR and have also been shown to undergo receptor-mediated transcytosis

ISRN Biochemistry 9

Among these it is still debated which mAb is the bestperforming to be used for the decoration of NPs surface Themostwell known isOX26 an antibody directed against the ratTfR that has been successfully used in many brain targetingstudies in vivo [114] and also in vitro using BBB cellularmodels [115] However Lee et al [116] have shown that theOX26monoclonal antibody is not an effective brain targetingmolecule in mice Moreover they demonstrated that othertwo monoclonal antibodies 8D3 and RI7217 directed againstthe mouse TfR had a higher permeability of the mouseBBB in vivo with respect to the brain uptake of the OX26antibody which was negligible Additionally they showedthat RI7217wasmore selective for the brain than 8D3 becausethis antibody was less taken up by the liver and kidney Ithas been shown that RI7217 covalently coupled to humanserum albumin is able to transport loperamide across theBBB [110] More recently it has been shown that also thechemical linkage of anti-TfR on the NPs surface could affectthe crossing of BBB in vitro [117] The authors comparedliposomes covalently coupled with mAbs (obtained by react-ing thiolatedmAbs to phosphatidyl-ethanolaminemaleimideinserted in the liposome bilayer) with liposomes decoratedwith biotinylated mAbs via an avidin bridge The Authorsfound an higher cellular uptake and permeability across anin vitro BBB model made of immortalized human braincapillary endothelial cells of the liposomes covalently coupledwith mAbs suggesting that the covalent ligation could bepreferentially chosen for NPs decoration

54 Retrograde Transport Transsynaptic retrograde trans-port could enable some types of nanocarriers to travel fromperipheral nerve terminals to neuronal cell bodies in the CNS[118] Studies in this regard have shown that NPs modifiedwith PEI and other polyplexes display active retrogradetransport along neurites but are unable to mediate efficientbiological actions upon reaching the neuronal body [119]

55 BBB Breakdown BBB breakdown occurs in neuroin-flammatory diseases [120] NPs can transiently and reversiblyopen the tight junctions located at the BBB and other sitesthus increasing their paracellular permeability [121 122]In particular blood-brain barrier disruption therapy is anintensive effectiveway of sendingmedication to brain tumors[123]

Nevertheless it is known that tight junctions can beopened only to a limited extent [124] thus only NPs smallerthan about 20 nm can use this pathway to penetrate into thebrain through the BBB

56 Exploiting MonocyteMacrophage Infiltration in the CNSMonocytemacrophage infiltration in the CNS plays a keyrole in neuroinflammation as well as in lesion developmentand brain injury in neurological diseases such as multiplesclerosis (MS) and stroke [124ndash126] Knowledge of activephases of cell infiltration during CNS disorders is importantbecause anti-inflammatory treatments can target cell adhe-sion molecules and chemokines guiding cellular trafficking[127] The monocyte infiltration through the BBB is also

widely believed to play an important role in HIV infectionof the CNS The blood-brain barrier appears unaltered untilthe late stage of HIV encephalitis HIV flux that movestoward the brain thus relies on hijacking with immune-activated leukocytes mainly monocytesmacrophages fromthe periphery [128]

In this paper BBB crossing by immune-activated macro-phages appears to suggest possible strategies for future ther-apeutic developments employing NPs This strategy couldbe realized at least in two ways (1) by embedding NPs intoactivated monocytes used as Trojan horses to reach the brain(2) by designing NPs mimicking activated monocytes

561 Trojan Monocytes for NPs Delivery to the Brain Nano-particulate drug delivery systems have been used to avoidthe RES clearance and achieve longer circulation time forenhanced tissue uptake However the enhancing of NPsphagocytosis by monocytes can be considered as an uncon-ventional approach to deliver NPs-loaded drugs to thebrain After phagocytosis of NPs monocytes just like Trojanhorses may transport their cargo into the brain Aferganet al [129] taking this approach embedded serotonin aBBB impermeable neurological drug into negatively chargedliposomes and analyzed brain uptake in rats and rabbitsThe performance of liposomal serotonin was significantlybetter leading to two-fold higher drug concentration inbrain than the free drug Since treatment of animals byalendronate resulted with inhibition of monocytes but not ofneutrophils andwith no brain delivery the authors suggestedthat monocytes are the main transporters of liposomes tothe brain In spite of the fact that the clinical relevance ofthis investigation is limited the Trojan monocyte approachprovides a new possibility of more effective treatment ofbrain-associated inflammatory disorders including multiplesclerosis and Alzheimerrsquos disease which are characterizedwith increased passage of immune cells across the BBB[130]

In other examples in order to improve the delivery ofcontrast agents to the brain iron oxide NPs administeredintravenously in vivo have been shown to detect activatedmacrophage infiltration in multiple sclerosis either in theCNS of humans [131 132] or rodentmodel [133ndash137] in strokeeither in human [138 139] or animal brain ischemia [140ndash143] in human or murine intracranial tumors [144 145] inEAE [146ndash148] or in an ischemiareperfusion long-lived ratmodel [149]

562 NPs Mimicking Activated Monocytes The therapeu-tic efficacy of drug-loaded NPs systemically administereddepends on their ability to evade the immune system tocross the biological barriers of the body and to localizeat target tissues Parodi et al [150] show that nanoporoussilicon particles can successfully perform all these actionswhen they are coated with cellular membranes purifiedfrom leukocytes avoiding being cleared by the immune sys-tem Furthermore they can communicate with endothelialcells through receptor-ligand interactions and transport andrelease a doxorubicin payload across an inflamed endothelial

10 ISRN Biochemistry

barrier in vitro Also the accumulation of coated NPs inmice inoculated with murine B16 melanoma was enhancedcompared with that of non coated NPs Particle coatingusing leukocyte membranes led to an approximately twofoldincrease in particle density in the tumor

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsit is predictable that the research of NPs mimicking immunecells might be effective in brain-associated disorders and willreceive a stimulus in this direction in the next years

6 Factors Affecting NPs Brain Drug Delivery

61 NPs Diffusion inside the Brain Parenchyma While thisfactor is likely not particularly relevant when brain drugdelivery is sought after it could be very important when thepassage of the BBBbyNPs is looked for since the extracellularspace (ECS) of the brain parenchyma could limit their diffu-sion or even preclude their entrance into the brainThe abilityto achieve brain penetration with larger NPs is expected toallow more uniform longer lasting and effective delivery ofdrugs within the brain and may in particular find practicein the treatment of brain tumors stroke neuroinflammationand other brain diseases where the BBB is compromised orwhere local delivery strategies are feasible

Today it is well established that the ECSoccupies a volumefraction of between 15 and 30 in normal adult brain tissuewith a typical value of 20 and that this falls to 5 duringglobal ischemia [151 152]

It is less obvious what the true size of the spaces betweencells is Small molecules such as inulin and sucrose diffusethrough the ECS with a decreased diffusion coefficient withrespect to water suggesting the existence of limitation to theirmovements [153]

Possible sources of the limitations to the diffusing mol-ecules are (a) the presence of cellular obstructions (b) trap-ping of molecules in dead-space microdomains (c) a viscousdrag imposed by themacromolecules that compose the extra-cellular matrix or drag arising from the walls of the channelswhen molecules are large such as in the case of NPs(d) transient binding to cell membranes or extracellularmatrix (e) nonspecific interaction with negative charges onthe extracellular matrix when the diffusing molecule hasadequate charge density

A different type of model was proposed by Thorne andNicholson [154] to explain the higher tortuosity experimen-tally measured for larger substances such as dextran andespecially large synthetic quantum dot nanocrystals in the invivo rat cortex It was assumed that the quantum dots with ahydrodynamic diameter of 35 nm were close to the averagewidth of the ECS and depending on whether a planar ortubularmodel was adopted the estimated ECSwidth was 38ndash64 nm

In counter tendency to Thorne and Nicholson [154]Nance et al [155] report that NPs as large as 114 nm indiameter diffused within the human and rat brain only ifthey were densely coated with PEG Using these minimally

adhesive PEG-coated NPs they estimated that human braintissue ECS has some pores larger than 200 nm and that morethan one-quarter of all pores are ge100 nm

In addition to ECS in CNS there is also much interest inthe possibility that perivascular spaces fluid-filled channelssurrounding arteries arterioles veins venules and possiblyevenmicrovessels offer potential pathways for rapid flow intoand out of brain parenchyma Measurements of perivascularspace widths in mammals suggest that their typical dimen-sions may be at least 2 orders of magnitude greater thanthe neocortical ECS width (eg arteriole perivascular spaceshave been reported in the range of 5ndash10 120583m or larger (inrodents and humans))

62 Effect of Protein Corona Different physicochemicalproperties not only size may determine the ability ofnanoparticles to reach the brain The situation is furthercomplicated by the formation of a so-called ldquocoronardquo ofbiomolecules on the surfaces of nanoparticles the composi-tion of which may vary depending on the route of exposureand on the physicochemical surface properties of NPs Theacquisition of a corona of biomolecules on the surface ofNPs may also determine whether NPs are able to cross fromone compartment to another and whether they are taken upeffectively by cells or not [156]

In practical situations in which nanoparticles interactwith living organisms the nanoparticle surfaces are initiallyexposed to a biological fluid such as blood dependingon the route of administration For instance NPs injectedintravenously would be exposed to blood plasma containingan excess of proteins and many other complex biomoleculeswhich bind competitively with the surface of the nanoparti-cles

The current idea is that ldquobarerdquo nanoparticles do notexist in vivo because they are immediately modified bythe adsorption of blood proteins with higher affinities forthe particle surface forming a more or less tightly boundlayer (the so-called hard corona) and a weakly associatedmobile layer (the so-called soft corona) When this issue wasinvestigated it has been found that typical coronas containa limited number and types of molecules gathered fromthe blood in spite of the fact that biological fluids containthousands of proteins [157] Moreover it should be noted thatthe corona may also play a role in other undesirable effectsof NPs in living systems such as complement activation andblood clotting and may not necessarily play a role only incellular uptake

It should be pointed out that none of the in vitro exper-iments conducted to study the process of NPs translocationto the brain takes into account the surface modification ofNPs inside the blood and how can this affect the crossingof the BBB This issue needs much further investigationMoreover NPs once internalized by endothelial BBB cellsthey may also exit towards the brain covered with differentbiomolecules depending on that they have undergone endo-cytosistranscytosisexocytosis and thus exert additionaleffects (eg toxicity) on neuron Also this issue has not yetbeen investigated

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

[1] K Honjo S E Black and N P Verhoeff ldquoAlzheimerrsquos diseasecerebrovascular disease and the 120573-amyloid cascaderdquo CanadianJournal of Neurological Sciences vol 39 no 6 pp 712ndash728 2012

[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

[12] W M Pardridge ldquoDrug transport across the blood-brainbarrierrdquo Journal of Cerebral Blood Flow amp Metabolism vol 32no 11 pp 1959ndash1972 2012

[13] A Minn S Leclerc J M Heydel et al ldquoDrug transport into themammalian brain the nasal pathway and its specific metabolicbarrierrdquo Journal of Drug Targeting vol 10 no 4 pp 285rndash296r2002

[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

[23] L Martin-Banderas M A Holgado J L Venero J Alvarez-Fuentes and M Fernadez-Arealo ldquoNanostructures for drugdelivery to the brainrdquoCurrentMedicinal Chemistry vol 148 no34 pp 5303ndash5321 2011

[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

[26] T Ishii T Asai D Oyama et al ldquoTreatment of cerebralischemia-reperfusion injury with PEGylated liposomes encap-sulating FK506rdquo FASEB Journal vol 27 no 4 pp 1362ndash13702013

[27] A Lindqvist J Rip P J Gaillard S Bjorkman and MHammarlund-Udenaes ldquoEnhanced brain delivery of the opioidpeptide DAMGO in glutathione PEGylated liposomes amicro-dialysis studyrdquoMolecular Pharmacology 2012

[28] A Orthmann R Zeisig R Suss D Lorenz M Lemm andI Fichtner ldquoTreatment of experimental brain metastasis withMTO-liposomes impact of fluidity and LRP-targeting on thetherapeutic resultrdquo Pharmaceutical Research vol 29 no 7 pp1949ndash1959 2012

[29] M T da Cruz S Simoes and M C de Lima ldquoImprovinglipoplex-mediated gene transfer into C6 glioma cells andprimary neuronsrdquo Experimental Neurology vol 187 no 1 pp65ndash75 2004

[30] F Artzner R Zantl and J O Radler ldquoLipid-DNA and lipid-polyelectrolyte mesophases structure and exchange kineticsrdquoCellular andMolecular Biology vol 46 no 5 pp 967ndash978 2000

[31] A Molinari M Colone A Calcabrini et al ldquoCationic lipo-somes loaded with m-THPC in photodynamic therapy for

14 ISRN Biochemistry

malignant gliomardquo Toxicology in Vitro vol 21 no 2 pp 230ndash234 2007

[32] Y Obata G Ciofani V Raffa et al ldquoEvaluation of cationicliposomes composed of an amino acid-based lipid for neuronaltransfectionrdquo Nanomedicine vol 6 no 1 pp e70ndashe77 2010

[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

[36] B Mishra B B Patel and S Tiwari ldquoColloidal nanocarriersa review on formulation technology types and applicationstoward targeted drug deliveryrdquo Nanomedicine vol 6 no 1 ppe9ndashe24 2010

[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

[40] S Md M Ali S Baboota et al ldquoPreparation characteri-zation in vivo biodistribution and pharmacokinetic studiesof donepezil-loaded PLGA nanoparticles for brain targetingrdquoDrug Development and Industrial Pharmacy 2013

[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

[43] Y E Choonara V Pillay V M K Ndesendo et al ldquoPoly-meric emulsion and crosslink-mediated synthesis of super-stable nanoparticles as sustained-release anti-tuberculosis drugcarriersrdquoColloids and Surfaces B vol 87 no 2 pp 243ndash254 2011

[44] R Pandey and G K Khuller ldquoOral nanoparticle-based antitu-berculosis drug delivery to the brain in an experimental modelrdquoJournal of Antimicrobial Chemotherapy vol 57 no 6 pp 1146ndash1152 2006

[45] L Hasadsri J Kreuter H Hattori T Iwasaki and J M GeorgeldquoFunctional protein delivery into neurons using polymericnanoparticlesrdquo Journal of Biological Chemistry vol 284 no 11pp 6972ndash6981 2009

[46] A V Kabanov E V Batrakova N S Melik-Nubarov et alldquoA new class of drug carriers micelles of poly(oxyethylene)-poly(oxypropylene) block copolymers as microcontainers for

drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

[50] L Albertazzi L Gherardini M Brondi et al ldquoIn vivo dis-tribution and toxicity of PAMAM dendrimers in the centralnervous system depend on their surface chemistryrdquo MolecularPharmacology vol 10 no 1 pp 249ndash260 2013

[51] S Kannan H Dai R S Navath et al ldquoDendrimer-basedpostnatal therapy for neuroinflammation and cerebral palsy ina rabbit modelrdquo Science Translational Medicine vol 4 no 130Article ID 130ra46 2012

[52] J Wu C Wang J Sun and Y Xue ldquoNeurotoxicity of silicananoparticles brain localization and dopaminergic neuronsdamage pathwaysrdquoACSNano vol 5 no 6 pp 4476ndash4489 2011

[53] F Sousa S Mandal C Garrovo et al ldquoFunctionalized goldnanoparticles a detailed in vivo multimodal microscopic braindistribution studyrdquo Nanoscale vol 2 no 12 pp 2826ndash28342010

[54] Y Ze L Zheng X Zhao et al ldquoMolecular mechanism oftitanium dioxide nanoparticles-induced oxidative injury in thebrain of micerdquo Chemosphere 2013

[55] R D Broadwell ldquoTranscytosis of macromolecules through theblood-brain barrier a cell biological perspective and criticalappraisalrdquo Acta Neuropathologica vol 79 no 2 pp 117ndash1281989

[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Marine BiologyJournal of

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Signal TransductionJournal of

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BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Enzyme Research

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International Journal of

Microbiology

8 ISRN Biochemistry

transports cholesterol and other lipids in the plasma and inthe CNS [80 81] The lipoproteins complexes can be takenup in the brain through the recognition of apoE by specificreceptors at the BBB which include the low-density lipopro-tein receptor (LDLR) and the LDLR-related protein (LRP)

Taking into consideration that LRP has been reported tobe highly expressed on endothelial brain microvessels [82]receptor-mediated transcytosis using NPs functionalized tobind this target has been exploited in several ways

First by exploiting the preferential absorption of ApoEon some types of NPs when in serum This feature has beendescribed for PBCA NPs coated with polysorbate 80 indeeddisplaying the ability to cross the BBB in vivo in animalmodels [83ndash85] and for PEGylated PHDCA NPs able topenetrate into brain endothelial cells in vitro [86]

Taking advantage of such opportunity the formation ofa stable ApoE decoration of NPs surface by covalent bindinghas been utilized to functionalize albumin-NPs or liposomesthat showed the capacity of enhancing BBB passage in vivo inrodent models [87ndash89]

It should be questioned whether other apolipoproteinsmay be employed for NPs functionalization to confer onthem the ability to enhance brain drug delivery In order toanswer this question in an investigation of Kreuter et al [90]PBCA NPs loaded with dalargin or loperamide were coatedwith different apo-lipoproteins AII B CII E or J coatedor not with polysorbate 80 and then injected in mice andthe drug effect on CNS was evaluated The results showedthat only NPs coated with apolipoprotein B or E were able toachieve an antinociceptive effect This effect was significantlyhigher after polysorbate-precoating and apolipoprotein B orE-overcoating [90]

The region of apoE that is critical for interaction with theLDL receptor resides between amino acid residues 140 and160 Several studies with synthetic peptides have investigatedthe structural features of the LDLR-binding sequence ofApoE [91 92]

Laskowitz et al [81] derived an apoE-mimetic pep-tide from amino acids 133ndash149 named COG133 (LRVR-LASHLRKLRKRLL) which retains its biological activity invitro and in vivoThis capacity is displayed also by a fragmentof 26 aa from ApoE4 [93]

It has also been reported that the tandemdimer (141ndash155)2

is recognized by the LDLR in contrast to themonomeric pep-tide (141ndash155) [94] Also a shorter sequence of this peptide thetandem dimer (141ndash150)

2 retains this ability [95] Probably

as a consequence of these observations sterically stabilizedliposomeswere functionalized onlywithApoE tandemdimerpeptide (141ndash150)

2 but not with the monomer and were

shown to be efficiently taken up by rat brain capillaryendothelial cells [96] Interestingly in spite of the theoreticalpremises based on receptor-mediated endocytosis liposomestagged with (141ndash150)

2were nonselectively internalized into

cultured BBB cells and clathrin- or caveolin-dependentendocytosis was not demonstrable [97]

However in a successive investigation the ApoE-derivedpeptide monomer 141ndash150 was utilized by Re et al [98]in comparison with the dimer for the functionalization ofliposomes entrapping a radioactive derivative of curcumin

The investigation showed a higher uptake of the drug byhuman endothelial cells and an enhancement of permeabilityof the drug across an in vitromodel of the BBBmade with thesame cells when using monomer-functionalized liposomes

Apart from the amino acid sequence other factors mayaffect the cellular uptake of these peptides [98] These factorsinclude the type of peptide its cationic nature its mode ofexposure to the cell surface the nature of the cargo and thechemical linkage between the peptide and the cargo otherthan the peptide surface density on the cellular uptake ofnanoparticles [98 99]

Finally also Angiopep-2 a ligand of LRP possesses a highbrain penetration capability in both in vitro model of theBBB and in situ brain perfusion in mice [100] PEG-PAMAMdendrimers functionalized using this peptide resulted ina high accumulation of a delivered gene into brain afterintravenous administration into mice [101] moreover alsofunctionalized polymeric NPs and carbon nanotubes (CNT)have been produced showing the ability to reach gliomatumors in mice [102 103]

532 Transferrin Receptor (TfR) The transferrin receptor(TfR) is the most widely studied receptor for BBB targetingTfR is a transmembrane glycoprotein consisting of twolinked 90-kDa subunits each one binding a transferrinmolecule The receptor is highly expressed on immature ery-throid cells placental tissue and rapidly dividing cells bothnormal and malignant [104] Furthermore it is expressedon hepatocytes and endothelial cells of the BBB The role ofthe receptor is the regulation of cellular uptake of iron viatransferrin a plasma protein which transports iron in thecirculation Cellular uptake starts with the binding of trans-ferrin to the transferrin receptor followed by endocytosis[105]

Iron-bound transferrin has a high affinity for the TfRtherefore it has been used with success as a ligand for func-tionalization and targeting of liposomes to cultured brainendothelial cells [106 107] However it is likely that thatNPs decorated with transferrin would not be performantin vivo since transferrin receptors are almost saturated inphysiological conditions because of the high circulatinglevels of endogenous protein [108] Nevertheless successfulbrain targeting using transferrin as a targeting ligandhas beenaccomplished in vivo [109 110] Concerning the specificity oftransferrin a comparative study has been carried out betweentransferrin or lactoferrin a multifunctional protein of thetransferrin family widely represented in various secretoryfluids such as milk [111] Lalani et al [112] compared in vivodistribution in mice of PLGA NPs surface modified with thetwo proteins and showed a better performance to reach thebrain in the case of lactoferrin

In order to avoid the competition with endogenous trans-ferrin circulating in blood the use of monoclonal antibodies(mAbs) directed against transferrin receptors on the BBB hasbeen suggested because they recognize different epitopes onthe receptor [113] For instance OX26 8D3 and R17217 mAbbind to TfR and have also been shown to undergo receptor-mediated transcytosis

ISRN Biochemistry 9

Among these it is still debated which mAb is the bestperforming to be used for the decoration of NPs surface Themostwell known isOX26 an antibody directed against the ratTfR that has been successfully used in many brain targetingstudies in vivo [114] and also in vitro using BBB cellularmodels [115] However Lee et al [116] have shown that theOX26monoclonal antibody is not an effective brain targetingmolecule in mice Moreover they demonstrated that othertwo monoclonal antibodies 8D3 and RI7217 directed againstthe mouse TfR had a higher permeability of the mouseBBB in vivo with respect to the brain uptake of the OX26antibody which was negligible Additionally they showedthat RI7217wasmore selective for the brain than 8D3 becausethis antibody was less taken up by the liver and kidney Ithas been shown that RI7217 covalently coupled to humanserum albumin is able to transport loperamide across theBBB [110] More recently it has been shown that also thechemical linkage of anti-TfR on the NPs surface could affectthe crossing of BBB in vitro [117] The authors comparedliposomes covalently coupled with mAbs (obtained by react-ing thiolatedmAbs to phosphatidyl-ethanolaminemaleimideinserted in the liposome bilayer) with liposomes decoratedwith biotinylated mAbs via an avidin bridge The Authorsfound an higher cellular uptake and permeability across anin vitro BBB model made of immortalized human braincapillary endothelial cells of the liposomes covalently coupledwith mAbs suggesting that the covalent ligation could bepreferentially chosen for NPs decoration

54 Retrograde Transport Transsynaptic retrograde trans-port could enable some types of nanocarriers to travel fromperipheral nerve terminals to neuronal cell bodies in the CNS[118] Studies in this regard have shown that NPs modifiedwith PEI and other polyplexes display active retrogradetransport along neurites but are unable to mediate efficientbiological actions upon reaching the neuronal body [119]

55 BBB Breakdown BBB breakdown occurs in neuroin-flammatory diseases [120] NPs can transiently and reversiblyopen the tight junctions located at the BBB and other sitesthus increasing their paracellular permeability [121 122]In particular blood-brain barrier disruption therapy is anintensive effectiveway of sendingmedication to brain tumors[123]

Nevertheless it is known that tight junctions can beopened only to a limited extent [124] thus only NPs smallerthan about 20 nm can use this pathway to penetrate into thebrain through the BBB

56 Exploiting MonocyteMacrophage Infiltration in the CNSMonocytemacrophage infiltration in the CNS plays a keyrole in neuroinflammation as well as in lesion developmentand brain injury in neurological diseases such as multiplesclerosis (MS) and stroke [124ndash126] Knowledge of activephases of cell infiltration during CNS disorders is importantbecause anti-inflammatory treatments can target cell adhe-sion molecules and chemokines guiding cellular trafficking[127] The monocyte infiltration through the BBB is also

widely believed to play an important role in HIV infectionof the CNS The blood-brain barrier appears unaltered untilthe late stage of HIV encephalitis HIV flux that movestoward the brain thus relies on hijacking with immune-activated leukocytes mainly monocytesmacrophages fromthe periphery [128]

In this paper BBB crossing by immune-activated macro-phages appears to suggest possible strategies for future ther-apeutic developments employing NPs This strategy couldbe realized at least in two ways (1) by embedding NPs intoactivated monocytes used as Trojan horses to reach the brain(2) by designing NPs mimicking activated monocytes

561 Trojan Monocytes for NPs Delivery to the Brain Nano-particulate drug delivery systems have been used to avoidthe RES clearance and achieve longer circulation time forenhanced tissue uptake However the enhancing of NPsphagocytosis by monocytes can be considered as an uncon-ventional approach to deliver NPs-loaded drugs to thebrain After phagocytosis of NPs monocytes just like Trojanhorses may transport their cargo into the brain Aferganet al [129] taking this approach embedded serotonin aBBB impermeable neurological drug into negatively chargedliposomes and analyzed brain uptake in rats and rabbitsThe performance of liposomal serotonin was significantlybetter leading to two-fold higher drug concentration inbrain than the free drug Since treatment of animals byalendronate resulted with inhibition of monocytes but not ofneutrophils andwith no brain delivery the authors suggestedthat monocytes are the main transporters of liposomes tothe brain In spite of the fact that the clinical relevance ofthis investigation is limited the Trojan monocyte approachprovides a new possibility of more effective treatment ofbrain-associated inflammatory disorders including multiplesclerosis and Alzheimerrsquos disease which are characterizedwith increased passage of immune cells across the BBB[130]

In other examples in order to improve the delivery ofcontrast agents to the brain iron oxide NPs administeredintravenously in vivo have been shown to detect activatedmacrophage infiltration in multiple sclerosis either in theCNS of humans [131 132] or rodentmodel [133ndash137] in strokeeither in human [138 139] or animal brain ischemia [140ndash143] in human or murine intracranial tumors [144 145] inEAE [146ndash148] or in an ischemiareperfusion long-lived ratmodel [149]

562 NPs Mimicking Activated Monocytes The therapeu-tic efficacy of drug-loaded NPs systemically administereddepends on their ability to evade the immune system tocross the biological barriers of the body and to localizeat target tissues Parodi et al [150] show that nanoporoussilicon particles can successfully perform all these actionswhen they are coated with cellular membranes purifiedfrom leukocytes avoiding being cleared by the immune sys-tem Furthermore they can communicate with endothelialcells through receptor-ligand interactions and transport andrelease a doxorubicin payload across an inflamed endothelial

10 ISRN Biochemistry

barrier in vitro Also the accumulation of coated NPs inmice inoculated with murine B16 melanoma was enhancedcompared with that of non coated NPs Particle coatingusing leukocyte membranes led to an approximately twofoldincrease in particle density in the tumor

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsit is predictable that the research of NPs mimicking immunecells might be effective in brain-associated disorders and willreceive a stimulus in this direction in the next years

6 Factors Affecting NPs Brain Drug Delivery

61 NPs Diffusion inside the Brain Parenchyma While thisfactor is likely not particularly relevant when brain drugdelivery is sought after it could be very important when thepassage of the BBBbyNPs is looked for since the extracellularspace (ECS) of the brain parenchyma could limit their diffu-sion or even preclude their entrance into the brainThe abilityto achieve brain penetration with larger NPs is expected toallow more uniform longer lasting and effective delivery ofdrugs within the brain and may in particular find practicein the treatment of brain tumors stroke neuroinflammationand other brain diseases where the BBB is compromised orwhere local delivery strategies are feasible

Today it is well established that the ECSoccupies a volumefraction of between 15 and 30 in normal adult brain tissuewith a typical value of 20 and that this falls to 5 duringglobal ischemia [151 152]

It is less obvious what the true size of the spaces betweencells is Small molecules such as inulin and sucrose diffusethrough the ECS with a decreased diffusion coefficient withrespect to water suggesting the existence of limitation to theirmovements [153]

Possible sources of the limitations to the diffusing mol-ecules are (a) the presence of cellular obstructions (b) trap-ping of molecules in dead-space microdomains (c) a viscousdrag imposed by themacromolecules that compose the extra-cellular matrix or drag arising from the walls of the channelswhen molecules are large such as in the case of NPs(d) transient binding to cell membranes or extracellularmatrix (e) nonspecific interaction with negative charges onthe extracellular matrix when the diffusing molecule hasadequate charge density

A different type of model was proposed by Thorne andNicholson [154] to explain the higher tortuosity experimen-tally measured for larger substances such as dextran andespecially large synthetic quantum dot nanocrystals in the invivo rat cortex It was assumed that the quantum dots with ahydrodynamic diameter of 35 nm were close to the averagewidth of the ECS and depending on whether a planar ortubularmodel was adopted the estimated ECSwidth was 38ndash64 nm

In counter tendency to Thorne and Nicholson [154]Nance et al [155] report that NPs as large as 114 nm indiameter diffused within the human and rat brain only ifthey were densely coated with PEG Using these minimally

adhesive PEG-coated NPs they estimated that human braintissue ECS has some pores larger than 200 nm and that morethan one-quarter of all pores are ge100 nm

In addition to ECS in CNS there is also much interest inthe possibility that perivascular spaces fluid-filled channelssurrounding arteries arterioles veins venules and possiblyevenmicrovessels offer potential pathways for rapid flow intoand out of brain parenchyma Measurements of perivascularspace widths in mammals suggest that their typical dimen-sions may be at least 2 orders of magnitude greater thanthe neocortical ECS width (eg arteriole perivascular spaceshave been reported in the range of 5ndash10 120583m or larger (inrodents and humans))

62 Effect of Protein Corona Different physicochemicalproperties not only size may determine the ability ofnanoparticles to reach the brain The situation is furthercomplicated by the formation of a so-called ldquocoronardquo ofbiomolecules on the surfaces of nanoparticles the composi-tion of which may vary depending on the route of exposureand on the physicochemical surface properties of NPs Theacquisition of a corona of biomolecules on the surface ofNPs may also determine whether NPs are able to cross fromone compartment to another and whether they are taken upeffectively by cells or not [156]

In practical situations in which nanoparticles interactwith living organisms the nanoparticle surfaces are initiallyexposed to a biological fluid such as blood dependingon the route of administration For instance NPs injectedintravenously would be exposed to blood plasma containingan excess of proteins and many other complex biomoleculeswhich bind competitively with the surface of the nanoparti-cles

The current idea is that ldquobarerdquo nanoparticles do notexist in vivo because they are immediately modified bythe adsorption of blood proteins with higher affinities forthe particle surface forming a more or less tightly boundlayer (the so-called hard corona) and a weakly associatedmobile layer (the so-called soft corona) When this issue wasinvestigated it has been found that typical coronas containa limited number and types of molecules gathered fromthe blood in spite of the fact that biological fluids containthousands of proteins [157] Moreover it should be noted thatthe corona may also play a role in other undesirable effectsof NPs in living systems such as complement activation andblood clotting and may not necessarily play a role only incellular uptake

It should be pointed out that none of the in vitro exper-iments conducted to study the process of NPs translocationto the brain takes into account the surface modification ofNPs inside the blood and how can this affect the crossingof the BBB This issue needs much further investigationMoreover NPs once internalized by endothelial BBB cellsthey may also exit towards the brain covered with differentbiomolecules depending on that they have undergone endo-cytosistranscytosisexocytosis and thus exert additionaleffects (eg toxicity) on neuron Also this issue has not yetbeen investigated

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

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[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

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[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

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[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

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14 ISRN Biochemistry

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[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

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[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

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ISRN Biochemistry 15

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16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

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[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

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[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

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BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Advances in

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Enzyme Research

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International Journal of

Microbiology

ISRN Biochemistry 9

Among these it is still debated which mAb is the bestperforming to be used for the decoration of NPs surface Themostwell known isOX26 an antibody directed against the ratTfR that has been successfully used in many brain targetingstudies in vivo [114] and also in vitro using BBB cellularmodels [115] However Lee et al [116] have shown that theOX26monoclonal antibody is not an effective brain targetingmolecule in mice Moreover they demonstrated that othertwo monoclonal antibodies 8D3 and RI7217 directed againstthe mouse TfR had a higher permeability of the mouseBBB in vivo with respect to the brain uptake of the OX26antibody which was negligible Additionally they showedthat RI7217wasmore selective for the brain than 8D3 becausethis antibody was less taken up by the liver and kidney Ithas been shown that RI7217 covalently coupled to humanserum albumin is able to transport loperamide across theBBB [110] More recently it has been shown that also thechemical linkage of anti-TfR on the NPs surface could affectthe crossing of BBB in vitro [117] The authors comparedliposomes covalently coupled with mAbs (obtained by react-ing thiolatedmAbs to phosphatidyl-ethanolaminemaleimideinserted in the liposome bilayer) with liposomes decoratedwith biotinylated mAbs via an avidin bridge The Authorsfound an higher cellular uptake and permeability across anin vitro BBB model made of immortalized human braincapillary endothelial cells of the liposomes covalently coupledwith mAbs suggesting that the covalent ligation could bepreferentially chosen for NPs decoration

54 Retrograde Transport Transsynaptic retrograde trans-port could enable some types of nanocarriers to travel fromperipheral nerve terminals to neuronal cell bodies in the CNS[118] Studies in this regard have shown that NPs modifiedwith PEI and other polyplexes display active retrogradetransport along neurites but are unable to mediate efficientbiological actions upon reaching the neuronal body [119]

55 BBB Breakdown BBB breakdown occurs in neuroin-flammatory diseases [120] NPs can transiently and reversiblyopen the tight junctions located at the BBB and other sitesthus increasing their paracellular permeability [121 122]In particular blood-brain barrier disruption therapy is anintensive effectiveway of sendingmedication to brain tumors[123]

Nevertheless it is known that tight junctions can beopened only to a limited extent [124] thus only NPs smallerthan about 20 nm can use this pathway to penetrate into thebrain through the BBB

56 Exploiting MonocyteMacrophage Infiltration in the CNSMonocytemacrophage infiltration in the CNS plays a keyrole in neuroinflammation as well as in lesion developmentand brain injury in neurological diseases such as multiplesclerosis (MS) and stroke [124ndash126] Knowledge of activephases of cell infiltration during CNS disorders is importantbecause anti-inflammatory treatments can target cell adhe-sion molecules and chemokines guiding cellular trafficking[127] The monocyte infiltration through the BBB is also

widely believed to play an important role in HIV infectionof the CNS The blood-brain barrier appears unaltered untilthe late stage of HIV encephalitis HIV flux that movestoward the brain thus relies on hijacking with immune-activated leukocytes mainly monocytesmacrophages fromthe periphery [128]

In this paper BBB crossing by immune-activated macro-phages appears to suggest possible strategies for future ther-apeutic developments employing NPs This strategy couldbe realized at least in two ways (1) by embedding NPs intoactivated monocytes used as Trojan horses to reach the brain(2) by designing NPs mimicking activated monocytes

561 Trojan Monocytes for NPs Delivery to the Brain Nano-particulate drug delivery systems have been used to avoidthe RES clearance and achieve longer circulation time forenhanced tissue uptake However the enhancing of NPsphagocytosis by monocytes can be considered as an uncon-ventional approach to deliver NPs-loaded drugs to thebrain After phagocytosis of NPs monocytes just like Trojanhorses may transport their cargo into the brain Aferganet al [129] taking this approach embedded serotonin aBBB impermeable neurological drug into negatively chargedliposomes and analyzed brain uptake in rats and rabbitsThe performance of liposomal serotonin was significantlybetter leading to two-fold higher drug concentration inbrain than the free drug Since treatment of animals byalendronate resulted with inhibition of monocytes but not ofneutrophils andwith no brain delivery the authors suggestedthat monocytes are the main transporters of liposomes tothe brain In spite of the fact that the clinical relevance ofthis investigation is limited the Trojan monocyte approachprovides a new possibility of more effective treatment ofbrain-associated inflammatory disorders including multiplesclerosis and Alzheimerrsquos disease which are characterizedwith increased passage of immune cells across the BBB[130]

In other examples in order to improve the delivery ofcontrast agents to the brain iron oxide NPs administeredintravenously in vivo have been shown to detect activatedmacrophage infiltration in multiple sclerosis either in theCNS of humans [131 132] or rodentmodel [133ndash137] in strokeeither in human [138 139] or animal brain ischemia [140ndash143] in human or murine intracranial tumors [144 145] inEAE [146ndash148] or in an ischemiareperfusion long-lived ratmodel [149]

562 NPs Mimicking Activated Monocytes The therapeu-tic efficacy of drug-loaded NPs systemically administereddepends on their ability to evade the immune system tocross the biological barriers of the body and to localizeat target tissues Parodi et al [150] show that nanoporoussilicon particles can successfully perform all these actionswhen they are coated with cellular membranes purifiedfrom leukocytes avoiding being cleared by the immune sys-tem Furthermore they can communicate with endothelialcells through receptor-ligand interactions and transport andrelease a doxorubicin payload across an inflamed endothelial

10 ISRN Biochemistry

barrier in vitro Also the accumulation of coated NPs inmice inoculated with murine B16 melanoma was enhancedcompared with that of non coated NPs Particle coatingusing leukocyte membranes led to an approximately twofoldincrease in particle density in the tumor

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsit is predictable that the research of NPs mimicking immunecells might be effective in brain-associated disorders and willreceive a stimulus in this direction in the next years

6 Factors Affecting NPs Brain Drug Delivery

61 NPs Diffusion inside the Brain Parenchyma While thisfactor is likely not particularly relevant when brain drugdelivery is sought after it could be very important when thepassage of the BBBbyNPs is looked for since the extracellularspace (ECS) of the brain parenchyma could limit their diffu-sion or even preclude their entrance into the brainThe abilityto achieve brain penetration with larger NPs is expected toallow more uniform longer lasting and effective delivery ofdrugs within the brain and may in particular find practicein the treatment of brain tumors stroke neuroinflammationand other brain diseases where the BBB is compromised orwhere local delivery strategies are feasible

Today it is well established that the ECSoccupies a volumefraction of between 15 and 30 in normal adult brain tissuewith a typical value of 20 and that this falls to 5 duringglobal ischemia [151 152]

It is less obvious what the true size of the spaces betweencells is Small molecules such as inulin and sucrose diffusethrough the ECS with a decreased diffusion coefficient withrespect to water suggesting the existence of limitation to theirmovements [153]

Possible sources of the limitations to the diffusing mol-ecules are (a) the presence of cellular obstructions (b) trap-ping of molecules in dead-space microdomains (c) a viscousdrag imposed by themacromolecules that compose the extra-cellular matrix or drag arising from the walls of the channelswhen molecules are large such as in the case of NPs(d) transient binding to cell membranes or extracellularmatrix (e) nonspecific interaction with negative charges onthe extracellular matrix when the diffusing molecule hasadequate charge density

A different type of model was proposed by Thorne andNicholson [154] to explain the higher tortuosity experimen-tally measured for larger substances such as dextran andespecially large synthetic quantum dot nanocrystals in the invivo rat cortex It was assumed that the quantum dots with ahydrodynamic diameter of 35 nm were close to the averagewidth of the ECS and depending on whether a planar ortubularmodel was adopted the estimated ECSwidth was 38ndash64 nm

In counter tendency to Thorne and Nicholson [154]Nance et al [155] report that NPs as large as 114 nm indiameter diffused within the human and rat brain only ifthey were densely coated with PEG Using these minimally

adhesive PEG-coated NPs they estimated that human braintissue ECS has some pores larger than 200 nm and that morethan one-quarter of all pores are ge100 nm

In addition to ECS in CNS there is also much interest inthe possibility that perivascular spaces fluid-filled channelssurrounding arteries arterioles veins venules and possiblyevenmicrovessels offer potential pathways for rapid flow intoand out of brain parenchyma Measurements of perivascularspace widths in mammals suggest that their typical dimen-sions may be at least 2 orders of magnitude greater thanthe neocortical ECS width (eg arteriole perivascular spaceshave been reported in the range of 5ndash10 120583m or larger (inrodents and humans))

62 Effect of Protein Corona Different physicochemicalproperties not only size may determine the ability ofnanoparticles to reach the brain The situation is furthercomplicated by the formation of a so-called ldquocoronardquo ofbiomolecules on the surfaces of nanoparticles the composi-tion of which may vary depending on the route of exposureand on the physicochemical surface properties of NPs Theacquisition of a corona of biomolecules on the surface ofNPs may also determine whether NPs are able to cross fromone compartment to another and whether they are taken upeffectively by cells or not [156]

In practical situations in which nanoparticles interactwith living organisms the nanoparticle surfaces are initiallyexposed to a biological fluid such as blood dependingon the route of administration For instance NPs injectedintravenously would be exposed to blood plasma containingan excess of proteins and many other complex biomoleculeswhich bind competitively with the surface of the nanoparti-cles

The current idea is that ldquobarerdquo nanoparticles do notexist in vivo because they are immediately modified bythe adsorption of blood proteins with higher affinities forthe particle surface forming a more or less tightly boundlayer (the so-called hard corona) and a weakly associatedmobile layer (the so-called soft corona) When this issue wasinvestigated it has been found that typical coronas containa limited number and types of molecules gathered fromthe blood in spite of the fact that biological fluids containthousands of proteins [157] Moreover it should be noted thatthe corona may also play a role in other undesirable effectsof NPs in living systems such as complement activation andblood clotting and may not necessarily play a role only incellular uptake

It should be pointed out that none of the in vitro exper-iments conducted to study the process of NPs translocationto the brain takes into account the surface modification ofNPs inside the blood and how can this affect the crossingof the BBB This issue needs much further investigationMoreover NPs once internalized by endothelial BBB cellsthey may also exit towards the brain covered with differentbiomolecules depending on that they have undergone endo-cytosistranscytosisexocytosis and thus exert additionaleffects (eg toxicity) on neuron Also this issue has not yetbeen investigated

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

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[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

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[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

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[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

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[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

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14 ISRN Biochemistry

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[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

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[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

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ISRN Biochemistry 15

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16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

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[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

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[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

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Molecular Biology International

GenomicsInternational Journal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

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Signal TransductionJournal of

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BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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International Journal of

Microbiology

10 ISRN Biochemistry

barrier in vitro Also the accumulation of coated NPs inmice inoculated with murine B16 melanoma was enhancedcompared with that of non coated NPs Particle coatingusing leukocyte membranes led to an approximately twofoldincrease in particle density in the tumor

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsit is predictable that the research of NPs mimicking immunecells might be effective in brain-associated disorders and willreceive a stimulus in this direction in the next years

6 Factors Affecting NPs Brain Drug Delivery

61 NPs Diffusion inside the Brain Parenchyma While thisfactor is likely not particularly relevant when brain drugdelivery is sought after it could be very important when thepassage of the BBBbyNPs is looked for since the extracellularspace (ECS) of the brain parenchyma could limit their diffu-sion or even preclude their entrance into the brainThe abilityto achieve brain penetration with larger NPs is expected toallow more uniform longer lasting and effective delivery ofdrugs within the brain and may in particular find practicein the treatment of brain tumors stroke neuroinflammationand other brain diseases where the BBB is compromised orwhere local delivery strategies are feasible

Today it is well established that the ECSoccupies a volumefraction of between 15 and 30 in normal adult brain tissuewith a typical value of 20 and that this falls to 5 duringglobal ischemia [151 152]

It is less obvious what the true size of the spaces betweencells is Small molecules such as inulin and sucrose diffusethrough the ECS with a decreased diffusion coefficient withrespect to water suggesting the existence of limitation to theirmovements [153]

Possible sources of the limitations to the diffusing mol-ecules are (a) the presence of cellular obstructions (b) trap-ping of molecules in dead-space microdomains (c) a viscousdrag imposed by themacromolecules that compose the extra-cellular matrix or drag arising from the walls of the channelswhen molecules are large such as in the case of NPs(d) transient binding to cell membranes or extracellularmatrix (e) nonspecific interaction with negative charges onthe extracellular matrix when the diffusing molecule hasadequate charge density

A different type of model was proposed by Thorne andNicholson [154] to explain the higher tortuosity experimen-tally measured for larger substances such as dextran andespecially large synthetic quantum dot nanocrystals in the invivo rat cortex It was assumed that the quantum dots with ahydrodynamic diameter of 35 nm were close to the averagewidth of the ECS and depending on whether a planar ortubularmodel was adopted the estimated ECSwidth was 38ndash64 nm

In counter tendency to Thorne and Nicholson [154]Nance et al [155] report that NPs as large as 114 nm indiameter diffused within the human and rat brain only ifthey were densely coated with PEG Using these minimally

adhesive PEG-coated NPs they estimated that human braintissue ECS has some pores larger than 200 nm and that morethan one-quarter of all pores are ge100 nm

In addition to ECS in CNS there is also much interest inthe possibility that perivascular spaces fluid-filled channelssurrounding arteries arterioles veins venules and possiblyevenmicrovessels offer potential pathways for rapid flow intoand out of brain parenchyma Measurements of perivascularspace widths in mammals suggest that their typical dimen-sions may be at least 2 orders of magnitude greater thanthe neocortical ECS width (eg arteriole perivascular spaceshave been reported in the range of 5ndash10 120583m or larger (inrodents and humans))

62 Effect of Protein Corona Different physicochemicalproperties not only size may determine the ability ofnanoparticles to reach the brain The situation is furthercomplicated by the formation of a so-called ldquocoronardquo ofbiomolecules on the surfaces of nanoparticles the composi-tion of which may vary depending on the route of exposureand on the physicochemical surface properties of NPs Theacquisition of a corona of biomolecules on the surface ofNPs may also determine whether NPs are able to cross fromone compartment to another and whether they are taken upeffectively by cells or not [156]

In practical situations in which nanoparticles interactwith living organisms the nanoparticle surfaces are initiallyexposed to a biological fluid such as blood dependingon the route of administration For instance NPs injectedintravenously would be exposed to blood plasma containingan excess of proteins and many other complex biomoleculeswhich bind competitively with the surface of the nanoparti-cles

The current idea is that ldquobarerdquo nanoparticles do notexist in vivo because they are immediately modified bythe adsorption of blood proteins with higher affinities forthe particle surface forming a more or less tightly boundlayer (the so-called hard corona) and a weakly associatedmobile layer (the so-called soft corona) When this issue wasinvestigated it has been found that typical coronas containa limited number and types of molecules gathered fromthe blood in spite of the fact that biological fluids containthousands of proteins [157] Moreover it should be noted thatthe corona may also play a role in other undesirable effectsof NPs in living systems such as complement activation andblood clotting and may not necessarily play a role only incellular uptake

It should be pointed out that none of the in vitro exper-iments conducted to study the process of NPs translocationto the brain takes into account the surface modification ofNPs inside the blood and how can this affect the crossingof the BBB This issue needs much further investigationMoreover NPs once internalized by endothelial BBB cellsthey may also exit towards the brain covered with differentbiomolecules depending on that they have undergone endo-cytosistranscytosisexocytosis and thus exert additionaleffects (eg toxicity) on neuron Also this issue has not yetbeen investigated

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

[1] K Honjo S E Black and N P Verhoeff ldquoAlzheimerrsquos diseasecerebrovascular disease and the 120573-amyloid cascaderdquo CanadianJournal of Neurological Sciences vol 39 no 6 pp 712ndash728 2012

[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

[12] W M Pardridge ldquoDrug transport across the blood-brainbarrierrdquo Journal of Cerebral Blood Flow amp Metabolism vol 32no 11 pp 1959ndash1972 2012

[13] A Minn S Leclerc J M Heydel et al ldquoDrug transport into themammalian brain the nasal pathway and its specific metabolicbarrierrdquo Journal of Drug Targeting vol 10 no 4 pp 285rndash296r2002

[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

[23] L Martin-Banderas M A Holgado J L Venero J Alvarez-Fuentes and M Fernadez-Arealo ldquoNanostructures for drugdelivery to the brainrdquoCurrentMedicinal Chemistry vol 148 no34 pp 5303ndash5321 2011

[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

[26] T Ishii T Asai D Oyama et al ldquoTreatment of cerebralischemia-reperfusion injury with PEGylated liposomes encap-sulating FK506rdquo FASEB Journal vol 27 no 4 pp 1362ndash13702013

[27] A Lindqvist J Rip P J Gaillard S Bjorkman and MHammarlund-Udenaes ldquoEnhanced brain delivery of the opioidpeptide DAMGO in glutathione PEGylated liposomes amicro-dialysis studyrdquoMolecular Pharmacology 2012

[28] A Orthmann R Zeisig R Suss D Lorenz M Lemm andI Fichtner ldquoTreatment of experimental brain metastasis withMTO-liposomes impact of fluidity and LRP-targeting on thetherapeutic resultrdquo Pharmaceutical Research vol 29 no 7 pp1949ndash1959 2012

[29] M T da Cruz S Simoes and M C de Lima ldquoImprovinglipoplex-mediated gene transfer into C6 glioma cells andprimary neuronsrdquo Experimental Neurology vol 187 no 1 pp65ndash75 2004

[30] F Artzner R Zantl and J O Radler ldquoLipid-DNA and lipid-polyelectrolyte mesophases structure and exchange kineticsrdquoCellular andMolecular Biology vol 46 no 5 pp 967ndash978 2000

[31] A Molinari M Colone A Calcabrini et al ldquoCationic lipo-somes loaded with m-THPC in photodynamic therapy for

14 ISRN Biochemistry

malignant gliomardquo Toxicology in Vitro vol 21 no 2 pp 230ndash234 2007

[32] Y Obata G Ciofani V Raffa et al ldquoEvaluation of cationicliposomes composed of an amino acid-based lipid for neuronaltransfectionrdquo Nanomedicine vol 6 no 1 pp e70ndashe77 2010

[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

[36] B Mishra B B Patel and S Tiwari ldquoColloidal nanocarriersa review on formulation technology types and applicationstoward targeted drug deliveryrdquo Nanomedicine vol 6 no 1 ppe9ndashe24 2010

[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

[40] S Md M Ali S Baboota et al ldquoPreparation characteri-zation in vivo biodistribution and pharmacokinetic studiesof donepezil-loaded PLGA nanoparticles for brain targetingrdquoDrug Development and Industrial Pharmacy 2013

[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

[43] Y E Choonara V Pillay V M K Ndesendo et al ldquoPoly-meric emulsion and crosslink-mediated synthesis of super-stable nanoparticles as sustained-release anti-tuberculosis drugcarriersrdquoColloids and Surfaces B vol 87 no 2 pp 243ndash254 2011

[44] R Pandey and G K Khuller ldquoOral nanoparticle-based antitu-berculosis drug delivery to the brain in an experimental modelrdquoJournal of Antimicrobial Chemotherapy vol 57 no 6 pp 1146ndash1152 2006

[45] L Hasadsri J Kreuter H Hattori T Iwasaki and J M GeorgeldquoFunctional protein delivery into neurons using polymericnanoparticlesrdquo Journal of Biological Chemistry vol 284 no 11pp 6972ndash6981 2009

[46] A V Kabanov E V Batrakova N S Melik-Nubarov et alldquoA new class of drug carriers micelles of poly(oxyethylene)-poly(oxypropylene) block copolymers as microcontainers for

drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

[50] L Albertazzi L Gherardini M Brondi et al ldquoIn vivo dis-tribution and toxicity of PAMAM dendrimers in the centralnervous system depend on their surface chemistryrdquo MolecularPharmacology vol 10 no 1 pp 249ndash260 2013

[51] S Kannan H Dai R S Navath et al ldquoDendrimer-basedpostnatal therapy for neuroinflammation and cerebral palsy ina rabbit modelrdquo Science Translational Medicine vol 4 no 130Article ID 130ra46 2012

[52] J Wu C Wang J Sun and Y Xue ldquoNeurotoxicity of silicananoparticles brain localization and dopaminergic neuronsdamage pathwaysrdquoACSNano vol 5 no 6 pp 4476ndash4489 2011

[53] F Sousa S Mandal C Garrovo et al ldquoFunctionalized goldnanoparticles a detailed in vivo multimodal microscopic braindistribution studyrdquo Nanoscale vol 2 no 12 pp 2826ndash28342010

[54] Y Ze L Zheng X Zhao et al ldquoMolecular mechanism oftitanium dioxide nanoparticles-induced oxidative injury in thebrain of micerdquo Chemosphere 2013

[55] R D Broadwell ldquoTranscytosis of macromolecules through theblood-brain barrier a cell biological perspective and criticalappraisalrdquo Acta Neuropathologica vol 79 no 2 pp 117ndash1281989

[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

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BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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International Journal of

Microbiology

ISRN Biochemistry 11

63 BBB Alterations in Neurological Diseases The peculiarphysiological features of the BBB affect the extent of drugpermeability and in most cases extremely restrict the amountof pharmaceuticals taken up by the brain It should be pointedout that the anatomy and organization of the BBB are alteredin a number of pathological conditions and these changescould have consequences onto the crossing of the barrier byphysiological circulatingmolecules drugs andNPs It shouldbe also pointed out that changes are not the same for all thediseases the variability is high thus it is hard to predict theeffects on any particular drug In general the BBB alterationscould cause shifts in the dosage efficacy and side effect ofcommonly used drugs

For instance the effect of hypoxia-ischemia on the barrierhas been extensively investigated Hypoxia-ischemia starts aseries of events which lead to increased BBB permeabilitypossibly due to disruption of tight junctions and mediatedby signaling molecules such as cytokines and nitric oxide[158] It is expected that the passage ofmacromolecules acrossthe BBB is increased under this condition It is thereforesignificant that nanostructured erythropoietin may exert aneuroprotective action against hypoxia-ischemia in animalmodels [159]

A variety of evidence demonstrates that the BBB isalso compromised in septic encephalopathy where albumin[160] has been shown to enter brain parenchyma from thecirculation in rodents

Also a series of neurologic inflammatory diseases includ-ing HIV-associated dementia and multiple sclerosis stronglyalter the integrity of the BBB with consequent migration ofleukocytes into the brain [161 162] The migration has beenshown to trigger signals leading to loss of tight junctionsmolecules and to opening of the BBB [163]

Although there is no evidence in humans or animalmodels for a massive disruption of the BBB in Alzheimerdisease (AD) there is evidence of a decreased glucose andoxygenuse by theADbrain If the decrease represents a defectin the flow across the barrier or in response to a decreasedrequirement by the CNS is unclear however it is consistentwith the AD environment promoting barrier cell secretionsthat have detrimental effects on cognition [164]What is clearis that BBB endothelial cells bind and internalize 120573-amyloidpeptide (A120573) where the peptide mostly remains adherent toor internalized by the cells A120573 induces chemokine secretionmonocyte trafficking decreased proliferation altered per-meability and altered nitric oxide synthase activity Micro-lesions representing limited protein leakage at capillaries havebeen demonstrated in some animal models of AD [165]Interestingly one of the few drugs available for the treatmentof AD the NMDA receptor antagonist memantine protectsagainst BBB disruption

64 Size An underestimated issue is whether or not the sizeof NPs designed for reaching the brain drug delivery makesany difference Different investigations have been carriedin the attempt to clarify this issue Sarin et al [166] afterhaving intravenously administered functionalized PAMAMdendrimers with size less than approximately 12 nm found

that NPs were able to traverse pores of the blood-brain tumorbarrier of RG-2 malignant gliomas while larger ones couldnot

Sonavane et al [167] studied tissue distribution of col-loidal gold nanoparticles of different sizes (15 50 100 and200 nm) after intravenous administration in mice The num-ber of NPs which entered the brain after 24 h was inverselydependent on the size and for 15 nm gold NPs was 500-fold higher than for 100 nm NPs while was very low for200 nm NPs However the total amount of gold which isproportional to total volume of NPs entered thus to thepayload of drug in the case of drug-loaded NPs was similarfor 15 and 50 and only 30 lower for 100 nm Oberdorsteret al [168] generated solid ultrafine particles of size around36 nmmade of graphite that were administered by inhalationby rodents The authors concluded that the CNS can betargeted by airborne NPs of this size via the olfactory nervefrom the olfactory mucosa

Recent evidence suggests that the transit through thegastrointestinal tract may strongly influence the subsequentaccess of NPs into the brain Hillyer and Albrecht [169]studied the gastrointestinal uptake and tissueorgan distri-bution of 4 10 28 and 58 nm diameter metallic colloidalgold NPs The gold NPs were administered orally and goldconcentration in various tissuesorgans brain included wasdetermined after 12 hThe author found that the total amountof gold uptaken in brain was similar for 4 and 58 nm particlesize Also Schleh et al [170] investigated the influence of sizeand surface charge of gold nanoparticles on the absorptionacross intestinal barriers and accumulation in brain afteroral administration The authors utilizing NPs from 14 to200 nm found the highest accumulation in secondary organsfor 14 nm particles while the highest brain accumulationwas recorded in the case of 18 nm NPs These data suggestthat the route of administration of NPs into the body is ofpharmacological and clinical importance and that NPs maycross the BBB whichever the initial route of administration

7 Neurotoxicity Issues

Even if the use of engineered NPs represents one of the mainhopes for innovative pharmacological strategies in neurology[171] it is important to mention that the BBB represents amechanism of defense of CNS against potentially neurotoxicmolecules and structures NPs included In vivo and clinicaldata evaluating the toxic effects of NPs on neural cells are stillscarce and it is still difficult to extrapolate the results obtainedon in vitro models to the actual situation in vivo [172] giventhat the application of NPs to the CNS is at a nascent stage

It should be pointed out that different types of NPsshowing promising features for in vivo applications at thebeginning were successively discarded after having demon-strated their toxicity when utilized in vivoThis is the case forinstance of quantum dots and carbon nanotubes that provedto be toxic in vivo [173] and for this reason their prospectiveuse in medicine will be likely limited to in vitro diagnosticsOther cases of NPs-related neurotoxicity have been reportedand neurological effects were described in mice exposed

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

[1] K Honjo S E Black and N P Verhoeff ldquoAlzheimerrsquos diseasecerebrovascular disease and the 120573-amyloid cascaderdquo CanadianJournal of Neurological Sciences vol 39 no 6 pp 712ndash728 2012

[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

[12] W M Pardridge ldquoDrug transport across the blood-brainbarrierrdquo Journal of Cerebral Blood Flow amp Metabolism vol 32no 11 pp 1959ndash1972 2012

[13] A Minn S Leclerc J M Heydel et al ldquoDrug transport into themammalian brain the nasal pathway and its specific metabolicbarrierrdquo Journal of Drug Targeting vol 10 no 4 pp 285rndash296r2002

[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

[23] L Martin-Banderas M A Holgado J L Venero J Alvarez-Fuentes and M Fernadez-Arealo ldquoNanostructures for drugdelivery to the brainrdquoCurrentMedicinal Chemistry vol 148 no34 pp 5303ndash5321 2011

[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

[26] T Ishii T Asai D Oyama et al ldquoTreatment of cerebralischemia-reperfusion injury with PEGylated liposomes encap-sulating FK506rdquo FASEB Journal vol 27 no 4 pp 1362ndash13702013

[27] A Lindqvist J Rip P J Gaillard S Bjorkman and MHammarlund-Udenaes ldquoEnhanced brain delivery of the opioidpeptide DAMGO in glutathione PEGylated liposomes amicro-dialysis studyrdquoMolecular Pharmacology 2012

[28] A Orthmann R Zeisig R Suss D Lorenz M Lemm andI Fichtner ldquoTreatment of experimental brain metastasis withMTO-liposomes impact of fluidity and LRP-targeting on thetherapeutic resultrdquo Pharmaceutical Research vol 29 no 7 pp1949ndash1959 2012

[29] M T da Cruz S Simoes and M C de Lima ldquoImprovinglipoplex-mediated gene transfer into C6 glioma cells andprimary neuronsrdquo Experimental Neurology vol 187 no 1 pp65ndash75 2004

[30] F Artzner R Zantl and J O Radler ldquoLipid-DNA and lipid-polyelectrolyte mesophases structure and exchange kineticsrdquoCellular andMolecular Biology vol 46 no 5 pp 967ndash978 2000

[31] A Molinari M Colone A Calcabrini et al ldquoCationic lipo-somes loaded with m-THPC in photodynamic therapy for

14 ISRN Biochemistry

malignant gliomardquo Toxicology in Vitro vol 21 no 2 pp 230ndash234 2007

[32] Y Obata G Ciofani V Raffa et al ldquoEvaluation of cationicliposomes composed of an amino acid-based lipid for neuronaltransfectionrdquo Nanomedicine vol 6 no 1 pp e70ndashe77 2010

[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

[36] B Mishra B B Patel and S Tiwari ldquoColloidal nanocarriersa review on formulation technology types and applicationstoward targeted drug deliveryrdquo Nanomedicine vol 6 no 1 ppe9ndashe24 2010

[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

[40] S Md M Ali S Baboota et al ldquoPreparation characteri-zation in vivo biodistribution and pharmacokinetic studiesof donepezil-loaded PLGA nanoparticles for brain targetingrdquoDrug Development and Industrial Pharmacy 2013

[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

[43] Y E Choonara V Pillay V M K Ndesendo et al ldquoPoly-meric emulsion and crosslink-mediated synthesis of super-stable nanoparticles as sustained-release anti-tuberculosis drugcarriersrdquoColloids and Surfaces B vol 87 no 2 pp 243ndash254 2011

[44] R Pandey and G K Khuller ldquoOral nanoparticle-based antitu-berculosis drug delivery to the brain in an experimental modelrdquoJournal of Antimicrobial Chemotherapy vol 57 no 6 pp 1146ndash1152 2006

[45] L Hasadsri J Kreuter H Hattori T Iwasaki and J M GeorgeldquoFunctional protein delivery into neurons using polymericnanoparticlesrdquo Journal of Biological Chemistry vol 284 no 11pp 6972ndash6981 2009

[46] A V Kabanov E V Batrakova N S Melik-Nubarov et alldquoA new class of drug carriers micelles of poly(oxyethylene)-poly(oxypropylene) block copolymers as microcontainers for

drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

[50] L Albertazzi L Gherardini M Brondi et al ldquoIn vivo dis-tribution and toxicity of PAMAM dendrimers in the centralnervous system depend on their surface chemistryrdquo MolecularPharmacology vol 10 no 1 pp 249ndash260 2013

[51] S Kannan H Dai R S Navath et al ldquoDendrimer-basedpostnatal therapy for neuroinflammation and cerebral palsy ina rabbit modelrdquo Science Translational Medicine vol 4 no 130Article ID 130ra46 2012

[52] J Wu C Wang J Sun and Y Xue ldquoNeurotoxicity of silicananoparticles brain localization and dopaminergic neuronsdamage pathwaysrdquoACSNano vol 5 no 6 pp 4476ndash4489 2011

[53] F Sousa S Mandal C Garrovo et al ldquoFunctionalized goldnanoparticles a detailed in vivo multimodal microscopic braindistribution studyrdquo Nanoscale vol 2 no 12 pp 2826ndash28342010

[54] Y Ze L Zheng X Zhao et al ldquoMolecular mechanism oftitanium dioxide nanoparticles-induced oxidative injury in thebrain of micerdquo Chemosphere 2013

[55] R D Broadwell ldquoTranscytosis of macromolecules through theblood-brain barrier a cell biological perspective and criticalappraisalrdquo Acta Neuropathologica vol 79 no 2 pp 117ndash1281989

[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

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Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

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The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

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Signal TransductionJournal of

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BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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International Journal of

Microbiology

12 ISRN Biochemistry

to SiO2andMnONPs [174] In vivo experiments showed that

other NPs also have some neurotoxicity by causing transientmicroglia activation and induction of TLR-2 promoter activ-ity in transgenic mice [175]

For these reasons the benefit-risk balance deriving fromtheuse of NPs intended for treatment of CNS diseases shouldbe carefully evaluated for each type of new engineered NPsWhen assessing the possible neurotoxicity of NPs it shouldbe pointed out that beyond of the core structure also surfacefunctionalization often employed for targeted delivery cansignificantly alter the biological response and induce neuro-toxicity of otherwise safe particles [176]Therefore this aspectalso needs to be taken into considerationMoreover it shouldalso be stressed that toxicity could depend by the openingof tight junctions of the BBB endothelia induced by NPsFor instance an in vitro study by Olivier et al [177] showedthat PBCA NPs induced a permeabilization of a BBB modelwhich was presumably attributed to the toxicity of the carrier

The most reliable data on the safety of NPs towardsCNS have been reported for liposomes and iron oxide NPsLiposomes are known from the 60s and are generally lowtoxic because they are composed of naturally occurring lipids[178] Iron oxide-based NPs are also believed to be scarcelytoxic to the CNS [179 180]

Another source of neurotoxicity could arise from thefunctionalization of NPs with cationized proteins [181] Toxiceffects have been detected only when such proteins areadministered to ldquoheterologousrdquo animals In view of thishuman proteins or recombinant humanized proteins shouldbe used for cationization and subsequent applications inhumans Moreover since the conjugation of proteins topolyethylene glycol has been shown to decrease their immu-nogenicity PEGylation of cationized molecules may be analternative to minimize the immunogenic potential of thesemolecules

8 Future Directions

Given the importance of finding new drug delivery systemsfor treatment of CNS diseases it is conceivable that newstrategies will be developed in the next future

Since several studies demonstrate increased passage ofmonocytes across the BBB in various pathological conditionsthe synthesis of NPs mimicking immune cells might beeffective in brain-associated disorders and it is thereforepredictable that the research will receive a stimulus in thisdirection in the next years It is also hypothesizable thatNPs designed to mimic the molecular interactions occurringbetween inflamed leukocytes and endothelium should pos-sess selectivity toward diverse host inflammatory responsesfor instance the incorporation of inflammation-sensitivesensors such as integrin lymphocyte function-associatedantigen (LFA)-1 I domain to mimic activated leukocytesfor the targeting of inflamed tumor microenvironments OrCCR2 since cerebral microglia can recruit an increasednumber of activated circulating monocytes into the brainin response to elevated cerebral monocyte chemoattractantprotein (MCP)-1

Other possibilities are to exploit the absence or at leastthe high permeability of some BBB regions The BBB ispresent in all brain regions with the exception area postremamedian eminence neurohypophysis pineal gland subfor-nical organ and lamina terminalis The endothelial cellspresent in capillaries of these brain areas have fenestrationsthat allow diffusion of molecules The most extended areawhere presumably a more extensive passage of NPs couldbe possible is occupied by the leptomeningeal space whichis the space occupied by Cerebrospinal fluid (CSF) includingall spaces continuous with the subarachnoid space such asperivascular spaces and ventricles [182] The data availableto date suggest that many macromolecules and nanopar-ticles can be delivered to CNS in biologically significantamounts

Moreover the perivascular spaces which are in continuitywith leptomeningeal space penetrate into the parenchymaprovide an unexplored avenue for drug transport deep intothe brain via CSF The flux of the interstitial fluid in theCNS parenchyma as well as the macro flux of CSF in theleptomeningeal space is believed to be generally opposite tothe desirable direction of CNS-targeted drug delivery Thefinal outcome will depend on the NPs behavior which hasnot been studied yet It is therefore conceivable that efforts inthis direction will be carried out in the next future in orderto exploit alternative administration routes

9 Conclusions

The number of deaths due to neurological or neurodegener-ative diseases is those of a world war with connected hugesocioeconomical problems and costs The treatment of suchdiseases is hampered by the presence of BBB insurmountableby most available and future potentially effective drugsTherefore the discovery and development of novel drugdelivery systems for the treatment of such diseases is amajor challenge for both the academic and pharmaceuticalcommunity Nanotechnology represents an innovative andpromising approach Currently several types of NPs areavailable for biomedical use with different features andapplications facilitating the delivery of neuroactivemoleculessuch as drugs growth factors and genes and cells to thebrain NPs offer clinical advantages for drug delivery suchas decreased drug dose reduced side effects increaseddrug half-life and the possibility to enhance drug crossingacross the BBB However the enhancement of brain deliveryobtained with drug-loaded NPs although very promisingis still quantitatively limited in comparison with free drugsConsequently with very few exceptions NPs are not yet aviable solution for pharmacology requiring enhancements ofone order of magnitude or more

Further investigations are necessary for a better com-prehension of the mechanisms which manage this differentNPs-mediated transport of the drugs to the brain Howeverthe strong efforts to allow the translation from preclinicalto concrete clinical applications are worth of the necessaryeconomic investments

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

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[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

[12] W M Pardridge ldquoDrug transport across the blood-brainbarrierrdquo Journal of Cerebral Blood Flow amp Metabolism vol 32no 11 pp 1959ndash1972 2012

[13] A Minn S Leclerc J M Heydel et al ldquoDrug transport into themammalian brain the nasal pathway and its specific metabolicbarrierrdquo Journal of Drug Targeting vol 10 no 4 pp 285rndash296r2002

[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

[23] L Martin-Banderas M A Holgado J L Venero J Alvarez-Fuentes and M Fernadez-Arealo ldquoNanostructures for drugdelivery to the brainrdquoCurrentMedicinal Chemistry vol 148 no34 pp 5303ndash5321 2011

[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

[26] T Ishii T Asai D Oyama et al ldquoTreatment of cerebralischemia-reperfusion injury with PEGylated liposomes encap-sulating FK506rdquo FASEB Journal vol 27 no 4 pp 1362ndash13702013

[27] A Lindqvist J Rip P J Gaillard S Bjorkman and MHammarlund-Udenaes ldquoEnhanced brain delivery of the opioidpeptide DAMGO in glutathione PEGylated liposomes amicro-dialysis studyrdquoMolecular Pharmacology 2012

[28] A Orthmann R Zeisig R Suss D Lorenz M Lemm andI Fichtner ldquoTreatment of experimental brain metastasis withMTO-liposomes impact of fluidity and LRP-targeting on thetherapeutic resultrdquo Pharmaceutical Research vol 29 no 7 pp1949ndash1959 2012

[29] M T da Cruz S Simoes and M C de Lima ldquoImprovinglipoplex-mediated gene transfer into C6 glioma cells andprimary neuronsrdquo Experimental Neurology vol 187 no 1 pp65ndash75 2004

[30] F Artzner R Zantl and J O Radler ldquoLipid-DNA and lipid-polyelectrolyte mesophases structure and exchange kineticsrdquoCellular andMolecular Biology vol 46 no 5 pp 967ndash978 2000

[31] A Molinari M Colone A Calcabrini et al ldquoCationic lipo-somes loaded with m-THPC in photodynamic therapy for

14 ISRN Biochemistry

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[32] Y Obata G Ciofani V Raffa et al ldquoEvaluation of cationicliposomes composed of an amino acid-based lipid for neuronaltransfectionrdquo Nanomedicine vol 6 no 1 pp e70ndashe77 2010

[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

[36] B Mishra B B Patel and S Tiwari ldquoColloidal nanocarriersa review on formulation technology types and applicationstoward targeted drug deliveryrdquo Nanomedicine vol 6 no 1 ppe9ndashe24 2010

[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

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[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

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[44] R Pandey and G K Khuller ldquoOral nanoparticle-based antitu-berculosis drug delivery to the brain in an experimental modelrdquoJournal of Antimicrobial Chemotherapy vol 57 no 6 pp 1146ndash1152 2006

[45] L Hasadsri J Kreuter H Hattori T Iwasaki and J M GeorgeldquoFunctional protein delivery into neurons using polymericnanoparticlesrdquo Journal of Biological Chemistry vol 284 no 11pp 6972ndash6981 2009

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drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

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[55] R D Broadwell ldquoTranscytosis of macromolecules through theblood-brain barrier a cell biological perspective and criticalappraisalrdquo Acta Neuropathologica vol 79 no 2 pp 117ndash1281989

[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

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[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

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[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

ISRN Biochemistry 13

Conflict of Interests

The author declares that he has no commercial or financialrelationship that could be construed as a conflict of interests

Acknowledgment

The authorrsquos work is currently funded by the EuropeanCommunityrsquos Seventh Framework Programme (FP72007ndash2013) under Grant agreement no 212043 (NAD)

References

[1] K Honjo S E Black and N P Verhoeff ldquoAlzheimerrsquos diseasecerebrovascular disease and the 120573-amyloid cascaderdquo CanadianJournal of Neurological Sciences vol 39 no 6 pp 712ndash728 2012

[2] J R Kanwar B Sriramoju and R K Kanwar ldquoNeurologicaldisorders and therapeutics targeted to surmount the blood-brain barrierrdquo International Journal of Nanomedicine vol 7 pp3259ndash3278 2012

[3] M Wahl A Unterberg A Baethmann and L SchillingldquoMediators of blood-brain barrier dysfunction and formationof vasogenic brain edemardquo Journal of Cerebral Blood Flow andMetabolism vol 8 no 5 pp 621ndash634 1988

[4] A G de Boer and D D Breimer ldquoCytokines and blood-brainbarrier permeabilityrdquo Progress in Brain Research vol 115 pp425ndash451 1998

[5] M A Petty and E H Lo ldquoJunctional complexes of the blood-brain barrier permeability changes in neuroinflammationrdquoProgress in Neurobiology vol 68 no 5 pp 311ndash323 2002

[6] A J Kastin W Pan L M Maness and W A Banks ldquoPeptidescrossing the blood-brain barrier some unusual observationsrdquoBrain Research vol 848 no 1-2 pp 96ndash100 1999

[7] WM Pardridge J Eisenberg and J Yang ldquoHuman blood-brainbarrier insulin receptorrdquo Journal of Neurochemistry vol 44 no6 pp 1771ndash1778 1985

[8] Y Zhang and W M Pardridge ldquoConjugation of brain-derivedneurotrophic factor to a blood-brain barrier drug targetingsystem enables neuroprotection in regional brain ischemiafollowing intravenous injection of the neurotrophinrdquo BrainResearch vol 889 no 1-2 pp 49ndash56 2001

[9] S Santaguida D Janigro M Hossain E Oby E Rapp andL Cucullo ldquoSide by side comparison between dynamic versusstatic models of blood-brain barrier in vitro a permeabilitystudyrdquo Brain Research vol 1109 no 1 pp 1ndash13 2006

[10] J M Rabanel V Aoun I Elkin M Mokhtar and P HildgenldquoDrug-loaded nanocarriers passive targeting and crossing ofbiological barriersrdquo Current Medicinal Chemistry vol 19 no 19pp 3070ndash3102 2012

[11] M A Bellavance M Blanchette and D Fortin ldquoRecentadvances in blood-brain barrier disruption as a CNS deliverystrategyrdquo AAPS Journal vol 10 no 1 pp 166ndash177 2008

[12] W M Pardridge ldquoDrug transport across the blood-brainbarrierrdquo Journal of Cerebral Blood Flow amp Metabolism vol 32no 11 pp 1959ndash1972 2012

[13] A Minn S Leclerc J M Heydel et al ldquoDrug transport into themammalian brain the nasal pathway and its specific metabolicbarrierrdquo Journal of Drug Targeting vol 10 no 4 pp 285rndash296r2002

[14] D Holmes ldquoThe next big things are tinyrdquo Lancet Neurology vol12 no 1 pp 31ndash32 2013

[15] F Re M Gregori and M Masserini ldquoNanotechnology forneurodegenerative disordersrdquo Nanomedicine NBM vol 8 sup-plement 1 pp S51ndashS58 2012

[16] M Youns J D Hoheisel and T Efferth ldquoTherapeutic anddiagnostic applications of nanoparticlesrdquo Current Drug Targetsvol 12 no 3 pp 357ndash365 2011

[17] K C Petkar S S Chavhan S Agatonovik-Kustrin and K KSawant ldquoNanostructured materials in drug and gene deliverya review of the state of the artrdquo Critical Reviews in TherapeuticDrug Carrier Systems vol 28 no 2 pp 101ndash164 2011

[18] X Montet M Funovics K Montet-Abou R Weissleder andL Josephson ldquoMultivalent effects of RGD peptides obtained bynanoparticle displayrdquo Journal of Medicinal Chemistry vol 49no 20 pp 6087ndash6093 2006

[19] J M Provenzale and G A Silva ldquoUses of nanoparticles forcentral nervous system imaging and therapyrdquoAmerican Journalof Neuroradiology vol 30 no 7 pp 1293ndash1301 2009

[20] R Gabathuler ldquoApproaches to transport therapeutic drugsacross the blood-brain barrier to treat brain diseasesrdquo Neuro-biology of Disease vol 37 no 1 pp 48ndash57 2010

[21] A J Andersen S H Hashemi G Galimberti F Re MMasserini and SMMoghimi ldquoThe interaction of complementsystem with abeta-binding liposomes towards engineering ofsafer vesicles for the management of Alzheimerrsquos diseaserdquoJournal of Biotechnology vol 150 no 1 pp S97ndashS98 2010

[22] S Haque S Md M I Alam J K Sahni J Ali and SBaboota ldquoNanostructure-based drug delivery systems for braintargetingrdquo Drug Development and Industrial Pharmacy vol 38no 4 pp 387ndash411 2012

[23] L Martin-Banderas M A Holgado J L Venero J Alvarez-Fuentes and M Fernadez-Arealo ldquoNanostructures for drugdelivery to the brainrdquoCurrentMedicinal Chemistry vol 148 no34 pp 5303ndash5321 2011

[24] M Budai and M Szogyi ldquoLiposomes as drug carrier systemsPreparation classification and therapeutical advantages of lipo-somesrdquoActa PharmaceuticaHungarica vol 71 no 1 pp 114ndash1182001

[25] F Lai A M Fadda and C Sinico ldquoLiposomes for braindeliveryrdquo Expert Opinion on Drug Delivery 2013

[26] T Ishii T Asai D Oyama et al ldquoTreatment of cerebralischemia-reperfusion injury with PEGylated liposomes encap-sulating FK506rdquo FASEB Journal vol 27 no 4 pp 1362ndash13702013

[27] A Lindqvist J Rip P J Gaillard S Bjorkman and MHammarlund-Udenaes ldquoEnhanced brain delivery of the opioidpeptide DAMGO in glutathione PEGylated liposomes amicro-dialysis studyrdquoMolecular Pharmacology 2012

[28] A Orthmann R Zeisig R Suss D Lorenz M Lemm andI Fichtner ldquoTreatment of experimental brain metastasis withMTO-liposomes impact of fluidity and LRP-targeting on thetherapeutic resultrdquo Pharmaceutical Research vol 29 no 7 pp1949ndash1959 2012

[29] M T da Cruz S Simoes and M C de Lima ldquoImprovinglipoplex-mediated gene transfer into C6 glioma cells andprimary neuronsrdquo Experimental Neurology vol 187 no 1 pp65ndash75 2004

[30] F Artzner R Zantl and J O Radler ldquoLipid-DNA and lipid-polyelectrolyte mesophases structure and exchange kineticsrdquoCellular andMolecular Biology vol 46 no 5 pp 967ndash978 2000

[31] A Molinari M Colone A Calcabrini et al ldquoCationic lipo-somes loaded with m-THPC in photodynamic therapy for

14 ISRN Biochemistry

malignant gliomardquo Toxicology in Vitro vol 21 no 2 pp 230ndash234 2007

[32] Y Obata G Ciofani V Raffa et al ldquoEvaluation of cationicliposomes composed of an amino acid-based lipid for neuronaltransfectionrdquo Nanomedicine vol 6 no 1 pp e70ndashe77 2010

[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

[36] B Mishra B B Patel and S Tiwari ldquoColloidal nanocarriersa review on formulation technology types and applicationstoward targeted drug deliveryrdquo Nanomedicine vol 6 no 1 ppe9ndashe24 2010

[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

[40] S Md M Ali S Baboota et al ldquoPreparation characteri-zation in vivo biodistribution and pharmacokinetic studiesof donepezil-loaded PLGA nanoparticles for brain targetingrdquoDrug Development and Industrial Pharmacy 2013

[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

[43] Y E Choonara V Pillay V M K Ndesendo et al ldquoPoly-meric emulsion and crosslink-mediated synthesis of super-stable nanoparticles as sustained-release anti-tuberculosis drugcarriersrdquoColloids and Surfaces B vol 87 no 2 pp 243ndash254 2011

[44] R Pandey and G K Khuller ldquoOral nanoparticle-based antitu-berculosis drug delivery to the brain in an experimental modelrdquoJournal of Antimicrobial Chemotherapy vol 57 no 6 pp 1146ndash1152 2006

[45] L Hasadsri J Kreuter H Hattori T Iwasaki and J M GeorgeldquoFunctional protein delivery into neurons using polymericnanoparticlesrdquo Journal of Biological Chemistry vol 284 no 11pp 6972ndash6981 2009

[46] A V Kabanov E V Batrakova N S Melik-Nubarov et alldquoA new class of drug carriers micelles of poly(oxyethylene)-poly(oxypropylene) block copolymers as microcontainers for

drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

[50] L Albertazzi L Gherardini M Brondi et al ldquoIn vivo dis-tribution and toxicity of PAMAM dendrimers in the centralnervous system depend on their surface chemistryrdquo MolecularPharmacology vol 10 no 1 pp 249ndash260 2013

[51] S Kannan H Dai R S Navath et al ldquoDendrimer-basedpostnatal therapy for neuroinflammation and cerebral palsy ina rabbit modelrdquo Science Translational Medicine vol 4 no 130Article ID 130ra46 2012

[52] J Wu C Wang J Sun and Y Xue ldquoNeurotoxicity of silicananoparticles brain localization and dopaminergic neuronsdamage pathwaysrdquoACSNano vol 5 no 6 pp 4476ndash4489 2011

[53] F Sousa S Mandal C Garrovo et al ldquoFunctionalized goldnanoparticles a detailed in vivo multimodal microscopic braindistribution studyrdquo Nanoscale vol 2 no 12 pp 2826ndash28342010

[54] Y Ze L Zheng X Zhao et al ldquoMolecular mechanism oftitanium dioxide nanoparticles-induced oxidative injury in thebrain of micerdquo Chemosphere 2013

[55] R D Broadwell ldquoTranscytosis of macromolecules through theblood-brain barrier a cell biological perspective and criticalappraisalrdquo Acta Neuropathologica vol 79 no 2 pp 117ndash1281989

[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

14 ISRN Biochemistry

malignant gliomardquo Toxicology in Vitro vol 21 no 2 pp 230ndash234 2007

[32] Y Obata G Ciofani V Raffa et al ldquoEvaluation of cationicliposomes composed of an amino acid-based lipid for neuronaltransfectionrdquo Nanomedicine vol 6 no 1 pp e70ndashe77 2010

[33] M Zhao J Chang X Fu et al ldquoNano-sized cationic polymericmagnetic liposomes significantly improves drug delivery to thebrain in ratsrdquo Journal of Drug Targeting vol 20 no 5 pp 416ndash421 2012

[34] I P Kaur R Bhandari S Bhandari and V Kakkar ldquoPotentialof solid lipid nanoparticles in brain targetingrdquo Journal ofControlled Release vol 127 no 2 pp 97ndash109 2008

[35] C Pardeshi P Rajput V Belgamwar et al ldquoSolid lipid basednanocarriers an overviewrdquo Acta Pharmaceutica vol 62 no 4pp 433ndash472 2012

[36] B Mishra B B Patel and S Tiwari ldquoColloidal nanocarriersa review on formulation technology types and applicationstoward targeted drug deliveryrdquo Nanomedicine vol 6 no 1 ppe9ndashe24 2010

[37] P Blasi S Giovagnoli A Schoubben M Ricci and C RossildquoSolid lipid nanoparticles for targeted brain drug deliveryrdquoAdvanced Drug Delivery Reviews vol 59 no 6 pp 454ndash4772007

[38] J X Wang X Sun and Z R Zhang ldquoEnhanced brain targetingby synthesis of 3101584051015840-dioctanoyl-5-fluoro-21015840-deoxyuridine andincorporation into solid lipid nanoparticlesrdquo European Journalof Pharmaceutics and Biopharmaceutics vol 54 no 3 pp 285ndash290 2002

[39] S Martins I Tho I Reimold et al ldquoBrain delivery of camp-tothecin by means of solid lipid nanoparticles formulationdesign in vitro and in vivo studiesrdquo International Journal ofPharmaceutics vol 439 no 1-2 pp 49ndash62 2012

[40] S Md M Ali S Baboota et al ldquoPreparation characteri-zation in vivo biodistribution and pharmacokinetic studiesof donepezil-loaded PLGA nanoparticles for brain targetingrdquoDrug Development and Industrial Pharmacy 2013

[41] J Madan R S Pandey V Jain O P Katare R Chandraand A Katyal ldquoPoly (ethylene)-glycol conjugated solid lipidnanoparticles of noscapine improve biological half-life braindelivery and efficacy in glioblastoma cellsrdquo Drug Delivery vol19 no 8 pp 378ndash391 2012

[42] X Zhang G Chen L Wen et al ldquoNovel multiple agentsloaded PLGA nanoparticles for brain delivery via inner earadministration in vitro and in vivo evaluationrdquo EuropeanJournal of Pharmaceutical Sciences vol 48 no 4-5 pp 595ndash6032013

[43] Y E Choonara V Pillay V M K Ndesendo et al ldquoPoly-meric emulsion and crosslink-mediated synthesis of super-stable nanoparticles as sustained-release anti-tuberculosis drugcarriersrdquoColloids and Surfaces B vol 87 no 2 pp 243ndash254 2011

[44] R Pandey and G K Khuller ldquoOral nanoparticle-based antitu-berculosis drug delivery to the brain in an experimental modelrdquoJournal of Antimicrobial Chemotherapy vol 57 no 6 pp 1146ndash1152 2006

[45] L Hasadsri J Kreuter H Hattori T Iwasaki and J M GeorgeldquoFunctional protein delivery into neurons using polymericnanoparticlesrdquo Journal of Biological Chemistry vol 284 no 11pp 6972ndash6981 2009

[46] A V Kabanov E V Batrakova N S Melik-Nubarov et alldquoA new class of drug carriers micelles of poly(oxyethylene)-poly(oxypropylene) block copolymers as microcontainers for

drug targeting from blood in brainrdquo Journal of ControlledRelease vol 22 no 2 pp 141ndash157 1992

[47] J Y Kim W I Choi Y H Kim and G Tae ldquoBrain-targeted delivery of protein using chitosan- and RVG peptide-conjugated pluronic-based nano-carrierrdquo Biomaterials vol 34no 4 pp 1170ndash1179 2013

[48] T Dutta H B Agashe M Garg P Balasubramanium MKabra and N K Jain ldquoPoly (propyleneimine) dendrimerbased nanocontainers for targeting of efavirenz to humanmonocytesmacrophages in vitrordquo Journal of Drug Targetingvol 15 no 1 pp 89ndash98 2007

[49] R S Dhanikula T Hammady and P Hildgen ldquoOn the mech-anism and dynamics of uptake and permeation of polyether-copolyester dendrimers across an in vitro blood-brain barriermodelrdquo Journal of Pharmaceutical Sciences vol 98 no 10 pp3748ndash3760 2009

[50] L Albertazzi L Gherardini M Brondi et al ldquoIn vivo dis-tribution and toxicity of PAMAM dendrimers in the centralnervous system depend on their surface chemistryrdquo MolecularPharmacology vol 10 no 1 pp 249ndash260 2013

[51] S Kannan H Dai R S Navath et al ldquoDendrimer-basedpostnatal therapy for neuroinflammation and cerebral palsy ina rabbit modelrdquo Science Translational Medicine vol 4 no 130Article ID 130ra46 2012

[52] J Wu C Wang J Sun and Y Xue ldquoNeurotoxicity of silicananoparticles brain localization and dopaminergic neuronsdamage pathwaysrdquoACSNano vol 5 no 6 pp 4476ndash4489 2011

[53] F Sousa S Mandal C Garrovo et al ldquoFunctionalized goldnanoparticles a detailed in vivo multimodal microscopic braindistribution studyrdquo Nanoscale vol 2 no 12 pp 2826ndash28342010

[54] Y Ze L Zheng X Zhao et al ldquoMolecular mechanism oftitanium dioxide nanoparticles-induced oxidative injury in thebrain of micerdquo Chemosphere 2013

[55] R D Broadwell ldquoTranscytosis of macromolecules through theblood-brain barrier a cell biological perspective and criticalappraisalrdquo Acta Neuropathologica vol 79 no 2 pp 117ndash1281989

[56] A K Kumagai J B Eisenberg and W M PardridgeldquoAbsorptive-mediated endocytosis of cationized albumin and a120573-endorphin-cationized albumin chimeric peptide by isolatedbrain capillaries Model system of blood-brain barrier trans-portrdquo Journal of Biological Chemistry vol 262 no 31 pp 15214ndash15219 1987

[57] G R Dakwar I Abu Hammad M Popov et al ldquoDelivery ofproteins to the brain by bolaamphiphilic nano-sized vesiclesrdquoJournal of Controlled Release vol 160 no 2 pp 315ndash321 2012

[58] J Jin K H Bae H Yang et al ldquoIn vivo specific delivery of c-MetsiRNA to glioblastoma using cationic solid lipid nanoparticlesrdquoBioconjugate Chemistry vol 22 no 12 pp 2568ndash2572 2011

[59] V Tuan Giam Chuang U Kragh-Hansen and M OtagirildquoPharmaceutical strategies utilizing recombinant human serumalbuminrdquo Pharmaceutical Research vol 19 no 5 pp 569ndash5772002

[60] X H Tian FWei T XWang et al ldquoIn vitro and in vivo studieson gelatin-siloxane nanoparticles conjugated with SynB peptideto increase drug delivery to the brainrdquo International Journal ofNanomedicine vol 7 pp 1031ndash1041 2012

[61] K S Rao M K Reddy J L Horning and V LabhasetwarldquoTAT-conjugated nanoparticles for the CNS delivery of anti-HIV drugsrdquo Biomaterials vol 29 no 33 pp 4429ndash4438 2008

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

ISRN Biochemistry 15

[62] L Liu S S Venkatraman Y Y Yang et al ldquoPolymeric micellesanchored with TAT for delivery of antibiotics across the blood-brain barrierrdquo Biopolymers vol 90 no 5 pp 617ndash623 2008

[63] K Xu H Wang L Liu et al ldquoEfficacy of CG(3)R(6)TATnanoparticles self-assembled from a novel antimicrobial pep-tide for the treatment of Candida albicansmeningitis in rabbitsrdquoChemotherapy vol 57 no 5 pp 417ndash425 2011

[64] M Praetorius C Brunner B Lehnert et al ldquoTranssynapticdelivery of nanoparticles to the central auditory nervous sys-temrdquo Acta Oto-Laryngologica vol 127 no 5 pp 486ndash490 2007

[65] H Xia X Gao G Gu et al ldquoPenetratin-functionalized PEG-PLA nanoparticles for brain drug deliveryrdquo International Jour-nal of Pharmacology vol 436 no 1-2 pp 840ndash850 2012

[66] T Parikh M M Bommana and E Squillante ldquoEfficacy ofsurface charge in targeting pegylated nanoparticles of sulpirideto the brainrdquo European Journal of Pharmaceutics and Biophar-maceutics vol 74 no 3 pp 442ndash450 2010

[67] X Liu C An P Jin X Liu and L Wang ldquoProtective effects ofcationic bovine serum albumin-conjugated PEGylated tanshi-none IIA nanoparticles on cerebral ischemiardquo Biomaterials vol34 no 3 pp 817ndash830 2013

[68] F Herve N Ghinea and J M Scherrmann ldquoCNS delivery viaadsorptive transcytosisrdquo AAPS Journal vol 10 no 3 pp 455ndash472 2008

[69] S Muro M Koval and V Muzykantov ldquoEndothelial endocyticpathways gates for vascular drug deliveryrdquo Current VascularPharmacology vol 2 no 3 pp 281ndash299 2004

[70] J Rejman V Oberle I S Zuhorn and D Hoekstra ldquoSize-dependent internalization of particles via the pathways ofclathrin-and caveolae-mediated endocytosisrdquoBiochemical Jour-nal vol 377 no 1 pp 159ndash169 2004

[71] J V Georgieva D Kalicharan P O Couraud et al ldquoSurfacecharacteristics of nanoparticles determine their intracellularfate in and processing by human blood-brain barrier endothe-lial cells in vitrordquoMolecular Therapy vol 19 no 2 pp 318ndash3252011

[72] Q Xu C HWang andDW Pack ldquoPolymeric carriers for genedelivery chitosan and poly(amidoamine) dendrimersrdquo CurrentPharmaceutical Design vol 16 no 21 pp 2350ndash2368 2010

[73] H Bao X Jin L Li F Lv and T Liu ldquoOX26 modifiedhyperbranched polyglycerol-conjugated poly(lactic-co-glycolicacid) nanoparticles synthesis characterization and evaluationof its brain delivery abilityrdquo Journal of Materials Science vol 23no 8 pp 1891ndash1901 2012

[74] R Prades S Guerrero E Arraya et al ldquoDelivery of goldnanoparticles to the brain by conjugation with a peptide thatrecognizes the transferrin receptorrdquoBiomaterials vol 33 no 29pp 7194ndash7205 2012

[75] M Yemisci Y Gursoy-Ozdemi S Caban et al ldquoTransport ofa caspase inhibitor across the blood-brain barrier by chitosannanoparticlesrdquo Methods in Enzymology vol 508 pp 253ndash2692012

[76] HKaratas YAktas YGursoy-Ozdemir et al ldquoAnanomedicinetransports a peptide caspase-3 inhibitor across the blood-brainbarrier and provides neuroprotectionrdquo Journal of Neurosciencevol 29 no 44 pp 13761ndash13769 2009

[77] W M Pardridge Y S Kang J L Buciak and J Yang ldquoHumaninsulin receptor monoclonal antibody undergoes high affinitybinding to human brain capillaries in vitro and rapid transcy-tosis through the blood-brain barrier in vivo in the primaterdquoPharmaceutical Research vol 12 no 6 pp 807ndash816 1995

[78] P Candela F Gosselet F Miller et al ldquoPhysiological pathwayfor low-density lipoproteins across the blood-brain barriertranscytosis through brain capillary endothelial cells in vitrordquoEndothelium vol 15 no 5-6 pp 254ndash264 2008

[79] Y Li H He X Jia et al ldquoA dual-targeting nanocarrier based onpoly(amidoamine) dendrimers conjugated with transferrin andtamoxifen for treating brain gliomasrdquo Biomaterials vol 33 no15 pp 3899ndash3908 2012

[80] G Bu ldquoApolipoprotein e and its receptors in Alzheimerrsquosdisease pathways pathogenesis and therapyrdquo Nature ReviewsNeuroscience vol 10 no 5 pp 333ndash344 2009

[81] D T Laskowitz A D Thekdi S D Thekdi et al ldquoDownreg-ulation of microglial activation by apolipoprotein E and apoE-mimetic peptidesrdquo Experimental Neurology vol 167 no 1 pp74ndash85 2001

[82] R D Bell A P Sagare A E Friedman et al ldquoTransport path-ways for clearance of human Alzheimerrsquos amyloid 120573-peptideand apolipoproteins E and J in the mouse central nervoussystemrdquo Journal of Cerebral Blood Flow and Metabolism vol 27no 5 pp 909ndash918 2007

[83] T M Goppert and R H Muller ldquoPolysorbate-stabilized solidlipid nanoparticles as colloidal carriers for intravenous targetingof drugs to the brain comparison of plasma protein adsorptionpatternsrdquo Journal of Drug Targeting vol 13 no 3 pp 179ndash1872005

[84] RM Koffie C T Farrar L J Saidi CMWilliam B T Hymanand T L Spires-Jones ldquoNanoparticles enhance brain deliveryof blood-brain barrier-impermeable probes for in vivo opticaland magnetic resonance imagingrdquo Proceedings of the NationalAcademy of Sciences of the United States of America vol 108 no46 pp 18837ndash118842 2011

[85] X H Tian X N Lin F Wei et al ldquoEnhanced brain targetingof temozolomide in polysorbate-80 coated polybutylcyanoacry-late nanoparticlesrdquo International Journal of Nanomedicine vol6 pp 445ndash452 2011

[86] H R Kim K Andrieux S Gil et al ldquoTranslocation ofpoly(ethylene glycol-co-hexadecyl)cyanoacrylate nanoparticlesinto rat brain endothelial cells role of apolipoproteins onreceptor-medicted endocytosisrdquo Biomacromolecules vol 8 no3 pp 793ndash799 2007

[87] KMichaelis MM Hoffmann S Dreis et al ldquoCovalent linkageof apolipoprotein E to albumin nanoparticles strongly enhancesdrug transport into the brainrdquo Journal of Pharmacology andExperimental Therapeutics vol 317 no 3 pp 1246ndash1253 2006

[88] A Zensi D Begley C Pontikis et al ldquoAlbumin nanoparticlestargeted with Apo E enter the CNS by transcytosis and aredelivered to neuronesrdquo Journal of Controlled Release vol 137 no1 pp 78ndash86 2009

[89] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[90] J Kreuter D Shamenkov V Petrov et al ldquoApolipoprotein-mediated transport of nanoparticle-bound drugs across theblood-brain barrierrdquo Journal of Drug Targeting vol 10 no 4pp 317ndash325 2002

[91] M P Mims A T Darnule R W Tovar et al ldquoA nonexchange-able apolipoprotein E peptide that mediates binding to the lowdensity lipoprotein receptorrdquo Journal of Biological Chemistryvol 269 no 32 pp 20539ndash20547 1994

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

16 ISRN Biochemistry

[92] G Datta M Chaddha D W Garber et al ldquoThe receptorbinding domain of apolipoprotein E linked to a model classA amphipathic helix enhances internalization and degradationof LDL by fibroblastsrdquo Biochemistry vol 39 no 1 pp 213ndash2202000

[93] U Hulsermann M M Hoffmann U Massing and G FrickerldquoUptake of apolipoprotein E fragment coupled liposomes bycultured brain microvessel endothelial cells and intact braincapillariesrdquo Journal of Drug Targeting vol 17 no 8 pp 610ndash6182009

[94] C A Dyer D P Cistola G C Parry and L K CurtissldquoStructural features of synthetic peptides of apolipoprotein Ethat bind the LDL receptorrdquo Journal of Lipid Research vol 36no 1 pp 80ndash88 1995

[95] X S Wang G Ciraolo R Morris and E GruensteinldquoIdentification of a neuronal endocytic pathway activated byan apolipoprotein E (apoE) receptor binding peptiderdquo BrainResearch vol 778 no 1 pp 6ndash15 1997

[96] I Sauer I R Dunay K Weisgraber M Bienert and MDathe ldquoAn apolipoprotein E-derived peptide mediates uptakeof sterically stabilized liposomes into brain capillary endothelialcellsrdquo Biochemistry vol 44 no 6 pp 2021ndash2029 2005

[97] E Leupold H Nikolenko and M Dathe ldquoApolipoprotein Epeptide-modified colloidal carriers the design determines themechanism of uptake in vascular endothelial cellsrdquo Biochimicaet Biophysica Acta vol 1788 no 2 pp 442ndash449 2009

[98] F Re I Cambianica C Zona S et al ldquoFunctionalizationof liposomes with ApoE-derived peptides at different densityaffects cellular uptake and drug transport across a blood-brainbarrier modelrdquo Nanomedicine NBM vol 7 no 5 pp 551ndash5592011

[99] G Datta D W Garber B H Chung et al ldquoCationic domain141-150 of apoE covalently linked to a class A amphipathic helixenhances atherogenic lipoprotein metabolism in vitro and invivordquo Journal of Lipid Research vol 42 no 6 pp 959ndash966 2001

[100] M Demeule J C Currie Y Bertrand et al ldquoInvolvementof the low-density lipoprotein receptor-related protein in thetranscytosis of the brain delivery vector Angiopep-2rdquo Journalof Neurochemistry vol 106 no 4 pp 1534ndash1544 2008

[101] W Ke K Shao R Huang et al ldquoGene delivery targeted tothe brain using an Angiopep-conjugated polyethyleneglycol-modified polyamidoamine dendrimerrdquo Biomaterials vol 30no 36 pp 6976ndash6985 2009

[102] H Xin X Sha X Jiang W Zhang L Chen and X FangldquoAnti-glioblastoma efficacy and safety of paclitaxel-loadingAngiopep-conjugated dual targeting PEG-PCL nanoparticlesrdquoBiomaterials vol 33 no 32 pp 8167ndash8176 2012

[103] J Ren S Shen D Wang et al ldquoThe targeted delivery ofanticancer drugs to brain glioma by PEGylated oxidized multi-walled carbon nanotubes modified with angiopep-2rdquo Biomate-rials vol 33 no 11 pp 3324ndash3333 2012

[104] P Ponka and C N Lok ldquoThe transferrin receptor role inhealth and diseaserdquo International Journal of Biochemistry andCell Biology vol 31 no 10 pp 1111ndash1137 1999

[105] T Moos T R Nielsen T Skjoslashrringe and E H Morgan ldquoIrontrafficking inside the brainrdquo Journal of Neurochemistry vol 103no 5 pp 1730ndash1740 2007

[106] C C Visser S Stevanovic L H Voorwinden et al ldquoTargetingliposomes with protein drugs to the blood-brain barrier invitrordquo European Journal of Pharmaceutical Sciences vol 25 no2-3 pp 299ndash305 2005

[107] J Chang Y Jallouli M Kroubi et al ldquoCharacterization ofendocytosis of transferrin-coated PLGA nanoparticles by theblood-brain barrierrdquo International Journal of Pharmaceuticsvol 379 no 2 pp 285ndash292 2009

[108] A G de Boer and P J Gaillard ldquoDrug targeting to the brainrdquoAnnual Review of Pharmacology andToxicology vol 47 pp 323ndash355 2007

[109] V Mishra S Mahor A Rawat et al ldquoTargeted brain deliveryof AZT via transferrin anchored pegylated albumin nanoparti-clesrdquo Journal of Drug Targeting vol 14 no 1 pp 45ndash53 2006

[110] K Ulbrich T Hekmatara E Herbert and J KreuterldquoTransferrin- and transferrin-receptor-antibody-modifiednanoparticles enable drug delivery across the blood-brainbarrier (BBB)rdquo European Journal of Pharmaceutics andBiopharmaceutics vol 71 no 2 pp 251ndash256 2009

[111] J H Brock ldquoLactoferrinmdash50 years onrdquo International Journal ofBiochemistry amp Cell Biology vol 90 no 3 pp 245ndash251 2012

[112] J Lalani Y Raichandani R Mathur et al ldquoComparativereceptor based brain delivery of tramadol-loaded poly(lactic-co-glycolic acid) nanoparticlesrdquo Journal of Biomedical Nan-otechnology vol 8 no 6 pp 918ndash927 2012

[113] A R Jones and E V Shusta ldquoBlood-brain barrier transport oftherapeutics via receptor-mediationrdquo Pharmaceutical Researchvol 24 no 9 pp 1759ndash1771 2007

[114] J Huwyler D Wu and W M Pardridge ldquoBrain drug deliveryof small molecules using immunoliposomesrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 93 no 24 pp 14164ndash14169 1996

[115] E Markoutsa G Pampalakis A Niarakis et al ldquoUptake andpermeability studies of BBB-targeting immunoliposomes usingthe hCMECD3 cell linerdquo European Journal of Pharmaceuticsand Biopharmaceutics vol 77 no 2 pp 265ndash274 2011

[116] H J Lee B Engelhardt J Lesley U Bickel andWM PardridgeldquoTargeting rat anti-mouse transferrin receptor monoclonalantibodies through blood-brain barrier in mouserdquo Journal ofPharmacology and Experimental Therapeutics vol 292 no 3pp 1048ndash1052 2000

[117] E Salvati F Re S Sesana et al ldquoLiposomes functionalizedto overcome the blood-brain barrier and to target amyloid-120573peptide the chemical design affects the permeability across anin vitro modelrdquo International Journal of Nanomedicine vol 8pp 1749ndash1758 2013

[118] B Cui C Wu L Chen et al ldquoOne at a time live tracking ofNGF axonal transport using quantum dotsrdquo Proceedings of theNational Academy of Sciences of the United States of Americavol 104 no 34 pp 13666ndash13671 2007

[119] JM Bergen and SH Pun ldquoAnalysis of the intracellular barriersencountered by nonviral gene carriers in a model of spatiallycontrolled delivery to neuronsrdquo Journal of Gene Medicine vol10 no 2 pp 187ndash197 2008

[120] H E de Vries J Kuiper A G de Boer T J C van Berkel andD D Breimer ldquoThe blood-brain barrier in neuroinflammatorydiseasesrdquo Pharmacological Reviews vol 49 no 2 pp 143ndash1551997

[121] S Sadekar and H Ghandehari ldquoTransepithelial transport andtoxicity of PAMAM dendrimers implications for oral drugdeliveryrdquo Advanced Drug Delivery Reviews vol 64 no 6 pp571ndash588 2012

[122] A F Kotze H L Lueszligen B J Leeuw B G Boer J CVerhoef and H E Junginger ldquoComparison of the effect ofdifferent chitosan salts and N-trimethyl chitosan chloride on

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

ISRN Biochemistry 17

the permeability of intestinal epithelial cells (Caco-2)rdquo Journalof Controlled Release vol 51 no 1 pp 35ndash46 1998

[123] L H Treat N McDannold Y Zhang N Vykhodtsevaand K Hynynen ldquoImproved anti-tumor effect of liposomaldoxorubicin after targeted blood-brain barrier disruption byMRI-guided focused ultrasound in rat gliomardquo Ultrasound inMedicine amp Biology vol 38 no 10 pp 1716ndash1725 2012

[124] R H Adamson J F Lenz X Zhang G N Adamson SWeinbaum and F E Curry ldquoOncotic pressures opposingfiltration across non-fenestrated rat microvesselsrdquo Journal ofPhysiology vol 557 no 3 pp 889ndash907 2004

[125] S Jander M Schroeter and A Saleh ldquoImaging inflammationin acute brain ischemiardquo Stroke vol 38 no 2 pp S642ndashS6452007

[126] G Enzmann C Mysiorek R Gorina et al ldquoThe neurovascularunit as a selective barrier to polymorphonuclear granulocyte(PMN) infiltration into the brain after ischemic injuryrdquo ActaNeuropathologica vol 125 no 3 pp 395ndash412 2013

[127] G Stoll S Jander and M Schroeter ldquoInflammation and glialresponses in ischemic brain lesionsrdquo Progress in Neurobiologyvol 56 no 2 pp 149ndash171 1998

[128] S Gartner ldquoHIV infection and dementiardquo Science vol 287 no5453 pp 602ndash604 2000

[129] E Afergan H Epstein R Dahan et al ldquoDelivery of serotoninto the brain bymonocytes following phagocytosis of liposomesrdquoJournal of Controlled Release vol 132 no 2 pp 84ndash90 2008

[130] K Park ldquoTrojan monocytes for improved drug delivery to thebrainrdquo Journal of Controlled Release vol 132 no 2 p 75 2008

[131] V Dousset B Brochet M S A Deloire et al ldquoMR imaging ofrelapsing multiple sclerosis patients using ultra-small-particleiron oxide and compared with gadoliniumrdquo American Journalof Neuroradiology vol 27 no 5 pp 1000ndash1005 2006

[132] S P Manninger L L Muldoon G Nesbit T Murillo PM Jacobs and E A Neuwelt ldquoAn exploratory study offerumoxtran-10 nanoparticles as a blood-brain barrier imagingagent targeting phagocytic cells in CNS inflammatory lesionsrdquoAmerican Journal of Neuroradiology vol 26 no 9 pp 2290ndash2300 2005

[133] V Dousset L Ballarino C Delalande et al ldquoCompari-son of ultrasmall particles of iron oxide (USPIO)-enhancedT2- weighted conventional T2-weighted and gadolinium-enhanced T1-weighted MR images in rats with experimentalautoimmune encephalomyelitisrdquo American Journal of Neurora-diology vol 20 no 2 pp 223ndash227 1999

[134] V Dousset C Delalande L Ballarino et al ldquoIn vivomacrophage activity imaging in the central nervous sys-tem detected by magnetic resonancerdquo Magnetic Resonance inMedicine vol 41 no 2 pp 329ndash333 1999

[135] S Floris E L A Blezer G Schreibelt et al ldquoBlood-brain barrierpermeability andmonocyte infiltration in experimental allergicencephalomyelitis a quantitativeMRI studyrdquo Brain vol 127 no3 pp 616ndash627 2004

[136] M Rausch P Hiestand D Baumann C Cannet andM RudinldquoMRI-based monitoring of inflammation and tissue damagein acute and chronic relapsing EAErdquo Magnetic Resonance inMedicine vol 50 no 2 pp 309ndash314 2003

[137] M Rausch P Hiestand C A Foster D R Baumann C Cannetand M Rudin ldquoPredictability of FTY720 efficacy in experi-mental autoimmune encephalomyelitis by in vivo macrophagetracking clinical implications for ultrasmall superparamagneticiron oxide-enhanced magnetic resonance imagingrdquo Journal ofMagnetic Resonance Imaging vol 20 no 1 pp 16ndash24 2004

[138] N Nighoghossian M Wiart S Cakmak et al ldquoInflammatoryresponse after ischemic stroke a USPIO-enhanced MRI studyin patientsrdquo Stroke vol 38 no 2 pp 303ndash307 2007

[139] A Saleh M Schroeter C Jonkmanns H P Hartung UModder and S Jander ldquoIn vivo MRI of brain inflammation inhuman ischaemic strokerdquo Brain vol 127 no 7 pp 1670ndash16772004

[140] C Kleinschnitz A Schutz I Nolte et al ldquoIn vivo detection ofdeveloping vessel occlusion in photothrombotic ischemic brainlesions in the rat by iron particle enhanced MRIrdquo Journal ofCerebral Blood Flow and Metabolism vol 25 no 11 pp 1548ndash1555 2005

[141] M Rausch A Sauter J Frohlich U Neubacher E W Raduand M Rudin ldquoDynamic patterns of USPIO enhancementcan be observed in macrophages after ischemic brain damagerdquoMagnetic Resonance in Medicine vol 46 no 5 pp 1018ndash10222001

[142] M Rausch D Baumann U Neubacher andM Rudin ldquoIn-vivovisualization of phagocytotic cells in rat brains after transientischemia by USPIOrdquo NMR in Biomedicine vol 15 no 4 pp278ndash283 2002

[143] M Schroeter A Saleh D Wiedermann M Hoehn and S Jan-der ldquoHistochemical detection of ultrasmall superparamagneticiron oxide (USPIO) contrast medium uptake in experimentalbrain ischemiardquoMagnetic Resonance in Medicine vol 52 no 2pp 403ndash406 2004

[144] E A Neuwelt P Varallyay A G Bago L L Muldoon GNesbit and R Nixon ldquoImaging of iron oxide nanoparticlesby MR and light microscopy in patients with malignant braintumoursrdquoNeuropathology andAppliedNeurobiology vol 30 no5 pp 456ndash471 2004

[145] C Zimmer R Weissleder K Poss A Bogdanova S CWright Jr and W S Enochs ldquoMR imaging of phagocytosis inexperimental gliomasrdquo Radiology vol 197 no 2 pp 533ndash5381995

[146] K Baeten J J Hendriks N Hellings et al ldquoVisualisation ofthe kinetics of macrophage infiltration during experimentalautoimmune encephalomyelitis by magnetic resonance imag-ingrdquo Journal of Neuroimmunology vol 195 no 1-2 pp 1ndash6 2008

[147] B BrochetM S Deloire T Touil et al ldquoEarlymacrophageMRIof inflammatory lesions predicts lesion severity and diseasedevelopment in relapsing EAErdquo NeuroImage vol 32 no 1 pp266ndash274 2006

[148] R D Oude Engberink E L Blezer C D Dijkstra S M vander Pol A van der Toorn and H E de Vries ldquoDynamics andfate of USPIO in the central nervous system in experimentalautoimmune encephalomyelitisrdquo NMR in Biomedicine vol 23no 9 pp 1087ndash1096 2010

[149] V Sekeljic D Bataveljic S Stamenkovic et al ldquoCellularmarkersof neuroinflammation and neurogenesis after ischemic braininjury in the long-term survival rat modelrdquo Brain Structure andFunction vol 217 no 2 pp 411ndash420 2012

[150] A Parodi N Quattrocchi A L van de Ven et al ldquoSyntheticnanoparticles functionalized with biomimetic leukocyte mem-branes possess cell-like functionsrdquo Nature Nanotechnology vol8 no 1 pp 61ndash68 2013

[151] E Sykova and C Nicholson ldquoDiffusion in brain extracellularspacerdquo Physiological Reviews vol 88 no 4 pp 1277ndash1340 2008

[152] D J Wolak and R G Thorne ldquoDiffusion of macromolecules inthe Brain implications for drug deliveryrdquoMolecular Pharmacol-ogy 2013

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

18 ISRN Biochemistry

[153] V A Levin J D Fenstermacher and C S Patlak ldquoSucroseand inulin space measurements of cerebral cortex in fourmammalian speciesrdquo The American Journal of Physiology vol219 no 5 pp 1528ndash1533 1970

[154] R G Thorne and C Nicholson ldquoIn vivo diffusion analysiswith quantum dots and dextrans predicts the width of brainextracellular spacerdquo Proceedings of the National Academy ofSciences of theUnited States of America vol 103 no 14 pp 5567ndash5572 2006

[155] E A Nance G F Woodworth K A Sailor et al ldquoA densepoly(ethylene glycol) coating improves penetration of largepolymeric nanoparticles within brain tissuerdquo Science Transla-tional Medicine vol 4 no 149 Article ID 149ra119 2012

[156] A Pietroiusti L Campagnolo and B Fadeel ldquoInteractionsof engineered nanoparticles with organs protected by internalbiological barriersrdquo Small 2012

[157] E Mahon A Salvati F Baldelli Bombelli I Lynch and KA Dawson ldquoDesigning the nanoparticle-biomolecule interfacefor targeting and therapeutic deliveryrdquo Journal of ControlledRelease vol 161 no 2 pp 164ndash174 2012

[158] Y Yang and G A Rosenberg ldquoBlood-brain barrier breakdownin acute and chronic cerebrovascular diseaserdquo Stroke vol 42no 11 pp 3323ndash3328 2011

[159] H Chen F Spagnoli M Burris et al ldquoNanoerythropoietin is10-times more effective than regular erythropoietin in neuro-protection in a neonatal rat model of hypoxia-ischemiardquo Strokevol 43 no 3 pp 884ndash887 2012

[160] XDeng XWang andRAndersson ldquoEndothelial barrier resis-tance inmultiple organs after septic and nonseptic challenges inthe ratrdquo Journal of Applied Physiology vol 78 no 6 pp 2052ndash2061 1995

[161] J Lou M Chofflon C Juillard et al ldquoBrain microvascularendothelial cells and leukocytes derived from patients withmultiple sclerosis exhibit increased adhesion capacityrdquo Neu-roReport vol 8 no 3 pp 629ndash633 1997

[162] A Minagar P Shapshak R Fujimura R Ownby M Heyesand C Eisdorfer ldquoThe role of macrophagemicroglia and astro-cytes in the pathogenesis of three neurologic disorders HIV-associated dementia Alzheimer disease andmultiple sclerosisrdquoJournal of the Neurological Sciences vol 202 no 1-2 pp 13ndash232002

[163] S J Bolton and V H Perry ldquoDifferential blood-brain barrierbreakdown and leucocyte recruitment following excitotoxiclesions in juvenile and adult ratsrdquo Experimental Neurology vol154 no 1 pp 231ndash240 1998

[164] H S Sharma R J Castellani M A Smith and A Sharma ldquoTheblood-brain barrier in Alzheimerrsquos disease novel therapeutictargets and nanodrug deliveryrdquo International Review of Neuro-biology vol 102 pp 47ndash90 2012

[165] K D Kania H C Wijesuriya S B Hladky and M ABarrand ldquoBeta amyloid effects on expression ofmultidrug effluxtransporters in brain endothelial cellsrdquoBrain Research vol 1418pp 1ndash11 2011

[166] H Sarin A S Kanevsky H Wu et al ldquoEffective transvasculardelivery of nanoparticles across the blood-brain tumor barrierinto malignant glioma cellsrdquo Journal of Translational Medicinevol 6 article 80 2008

[167] G Sonavane K Tomoda and K Makino ldquoBiodistribution ofcolloidal gold nanoparticles after intravenous administrationeffect of particle sizerdquo Colloids and Surfaces B vol 66 no 2 pp274ndash280 2008

[168] G Oberdorster Z Sharp V Atudorei et al ldquoTranslocation ofinhaled ultrafine particles to the brainrdquo Inhalation Toxicologyvol 16 no 6-7 pp 437ndash445 2004

[169] J F Hillyer and R M Albrecht ldquoGastrointestinal persorp-tion and tissue distribution of differently sized colloidal goldnanoparticlesrdquo Journal of Pharmaceutical Sciences vol 90 no12 pp 1927ndash1936 2001

[170] C Schleh M Semmler-Behnke J Lipka et al ldquoSize andsurface charge of gold nanoparticles determine absorptionacross intestinal barriers and accumulation in secondary targetorgans after oral administrationrdquo Nanotoxicology vol 6 no 1pp 36ndash46 2012

[171] E Barbu E Molnar J Tsibouklis and D C Gorecki ldquoThepotential for nanoparticle-based drug delivery to the brainovercoming the blood-brain barrierrdquo Expert Opinion on DrugDelivery vol 6 no 6 pp 553ndash565 2009

[172] R Landsiedel E Fabian L Ma-Hock B van RavenzwaayW Wohlleben et al ldquoToxico-biokinetics of nanomaterialsrdquoArchives of Toxicoogyl vol 86 no 7 pp 1021ndash1060 2012

[173] T T Win-Shwe and H Fujimaki ldquoNanoparticles and neurotox-icityrdquo International Journal of Molecular Sciences vol 12 no 9pp 6267ndash6280 2011

[174] A Elder R Gelein V Silva et al ldquoTranslocation of inhaledultrafine manganese oxide particles to the central nervoussystemrdquo Environmental Health Perspectives vol 114 no 8 pp1172ndash1178 2006

[175] E Hutter S Boridy S Labrecque et al ldquoMicroglial responseto gold nanoparticlesrdquo ACS Nano vol 4 no 5 pp 2595ndash26062010

[176] C J Rivet Y Yuan D A Borca-Tasciuc and R J GilbertldquoAltering iron oxide nanoparticle surface properties inducecortical neuron cytotoxicityrdquo Chemical Research in Toxicologyvol 25 no 1 pp 153ndash161 2011

[177] J C Olivier L Fenart R Chauvet C Pariat R Cecchelli andW Couet ldquoIndirect evidence that drug brain targeting usingpolysorbate 80- coated polybutylcyanoacrylate nanoparticles isrelated to toxicityrdquo Pharmaceutical Research vol 16 no 12 pp1836ndash1842 1999

[178] J Buse and A El-Aneed ldquoProperties engineering and applica-tions of lipid-based nanoparticle drug-delivery systems currentresearch and advancesrdquo Nanomedicine vol 5 no 8 pp 1237ndash1260 2010

[179] P Xu J Li B Chen et al ldquoThe real-time neurotoxicity analysisof Fe3O4 nanoparticles combined with daunorubicin for ratbrain in vivordquo Journal of Biomedical Nanotechnology vol 8 no3 pp 417ndash423 2012

[180] S P Singh M F Rahman U S Murty M Mahboob and PGrover ldquoComparative study of genotoxicity and tissue distribu-tion of nano and micron sized iron oxide in rats after acute oraltreatmentrdquo Toxicology and Applied Pharmacology vol 266 no1 pp 56ndash66 2013

[181] ZCui andR JMumper ldquoCoating of cationized protein on engi-neered nanoparticles results in enhanced immune responsesrdquoInternational Journal of Pharmaceutics vol 238 no 1-2 pp 229ndash239 2002

[182] M I Papisov V Belov and K Gannon ldquoPhysiology of theintrathecal bolus the leptomeningeal route for macromoleculeand particle delivery to CNSrdquoMolecular Pharmacology 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Anatomy Research International

PeptidesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporation httpwwwhindawicom

International Journal of

Volume 2014

Zoology

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Molecular Biology International

GenomicsInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioinformaticsAdvances in

Marine BiologyJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Signal TransductionJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

BioMed Research International

Evolutionary BiologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Biochemistry Research International

ArchaeaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Genetics Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Virolog y

Hindawi Publishing Corporationhttpwwwhindawicom

Nucleic AcidsJournal of

Volume 2014

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Enzyme Research

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

International Journal of

Microbiology