2nd term (ceutics) colloidal drug delivery systems

7/27/2019 2nd Term (Ceutics) Colloidal Drug Delivery Systems

1/99

Colloidal drug delivery systems

Colloidal size range (1-1,000 nm)

4/11/2010 1Dr Mahmoud Mokhtar Ahmed Ibrahim


2/99

Two methods for site specific or targeted

delivery:

1- Synthesis of prodrug (new drug) by chemical

modification. Active moiety released after

metabolism in vivo.

2- The use of drug delivery systems (Liposomes,

Niosomes, microemulsions, nanopaticles,

etc). Provide targeting and controlled

delivery for drugs.



3/99

Advantages of controlled drug delivery

systems

Increase the amount of drug reach site of

action.

Decrease the amount being distributed to

other parts of the body.

Reduce the unwanted side effects.

Reduce the dose required.

Increase the therapeutic index of the drug.



4/99

Liposomes

These are microscopic spherical vesicles that

formed when phospholipids are hydrated with

water.

Dioleoyl Phosphatidylethanolamine

4/11/2010

4Dr Mahmoud Mokhtar Ahmed Ibrahim


5/99


6/99



7/99

Advantages of liposomes:

Controlled drug delivery systems.

Carry both hydrophilic and lipophilicdrugs.

Solubilize insoluble compounds.

Selective passive targeting to tumor.

Increase efficacy and therapeutic index.

Reduce the toxicity of encapsulated drug.

Improve pharmacokinetics (reduceelimination and increase circulation lifetime)

Increase stability via encapsulation.(protection against metabolicdegradation).



8/99

Issues to consider when selecting lipids:

Phase transition temperature (Tc): the temp. required to induce physicalchange in the lipid from the ordered gel state to disordered liquidcrystalline state (hydrocarbon chains randomly oriented).

The Tc of a lipid depends on:

Acyl chain length.

Degree of saturation.

Polar head group.

Stability: unsaturated lipids from biological source less stable thansaturated synthetic ones.

Charge: affect physical stability.

Cholesterol: can modulate membrane fluidity, elasticity, and permeability.

Fills gaps created by imperfect packing of other lipid species increasemembrane rigidity).



9/99

Types of liposomes:

Vesicle Types Abbreviation Diameter Size Number of lipid bilayers

Small unilamellar vesicles SUV

Diameter of 20-

100nm. One lipid bilayer

Large unilamellar vesicles LUVDiameter of

100nm.One lipid bilayer

Multilamellar vesicles MLV Diameter of 0.5m. Five to twenty lipid bilayers

Oligolamellar vesicles OLVDiameter of 0.1-

1m.Approximately five lipid bilayers

Multivesicular vesicles MVV Diameter of 1m. Multicompartmental structure



10/99

Preparation of liposomes:

Passive loading:1- Hand shaking or lipid film method:

a) Dissolve lipids in organic solvent Chloroform, ether,chloroform methanol mixtures, butanol,cyclohexane to obtain clear lipid solution.

b) Removal of the solvent using rotary evaporator toobtain the thin lipid film.

c) Hydration of the lipid film: by addition of water and

agitation. Temperature should be above the Tc forthe phospholipid used. Hydration time of one hourwith vigorous shaking is recommended.



11/99



12/99

Mechanism of vesicle formation:

Hydration

Extrusion (200 nm)

Lipid film Swelling

Agitation

Lipid preparation, hydration with agitation, sizing to produce homogenous distribution.4/11/2010 12Dr Mahmoud Mokhtar Ahmed Ibrahim


13/99

Sizing of the prepared vesicles:

1- Sonication: produce vesicles of SUV with diameters of 15-50 nm.Bath and probe sonicators are used

Probe sonicator of high energy however has the followingdisadvantages:

Over heating of the lipid suspension, and release of titanium

particles which enhance lipid degradation.2- Sequential extrusion (Done at a temp. above Tc): the lipid

suspension is forced through polycarbonated membrane filters witha defined pore size to yield liposomes of sizes close to the filterpore size.

3- Ultra-centrifugation (separate liposomes into diferent fractionsaccording to the RPM and vesicle size).

4- Gel permeation chromatography. (also fractionate liposomalpreparation).

5- High shear homogenization.



14/99

2- Ether infusion method:

Introduction of lipid solution in ether or ether/methanol

mix into warm water (above Tc) using syringe typeinfusion pump.

3- Detergent removal.

When a mixed micelle of detergent with phospholipids

dialyzed against water or passed through sephadex G25 column (SEC).4- Reversed phase evaporation:

Diethly ether and isopropyl ether are the usual solvents ofchoice for phospholipids. w/o microemulsions are formed by

sonication. Organic solvent is removed by rotary evaporator toform liposomes of LUV or oligolammellar vesicles.



15/99

5-The dehydration-rehydration method.

This method begins with empty buffer containing SUVs(hand shaken MLVs can be also used but are usually notpreferred).

These are mixed with the component to be entrapped,after which they are dried.

Freeze-drying is often the method of choice but other

methods such as drying by vacuum or under a stream ofnitrogen can be used. The vesicles are then rehydrated.

A mechanism the vesicles become more concentratedduring dehydration, they flatten and fuse formingmultilamellar planes where the solute is sandwiched,

hence, on hydration, larger vesicles are formed. This technique is mild and simple, the main limitation being

the heterogeneity of the size of the liposomes.



16/99

Active loading Remote loading

1- pH Gradient method: a pH differential made across theliposome membrane with a lower pH inside theliposome. The amine drug is then added external to thelipoosome and crosses the membrane barrier in theunionized state. Once inside the liposome the drugbecomes protonated and is unable to leave the liposome.The acid pH inside the liposome vesicles thus acts as anintra-vesicular trap.

2- (NH4)2 SO4 gradient method:

The presence of ammonium sulphate within the vesiclesapparently causes the amine drug to form a gel withinthe liposome vesicles. Hence, ammonium sulphate actsas an intra-vesicular trap for amine drugs.



17/99

Liposomes evaluation for in vitro, in

vivo quality control.

Drug to lipid ratio,

Encapsulation Efficiency,

Particle size,

Lamellarity ,

Using Electronmicroscopy, X ray scattering

technique, NMR, light scattering.



18/99


19/99

4/11/2010 19

Classes of Liposomes: surface charge and

attached ligand

Conventional (neutral)

Long circulating (Pegylated)Immuno (targeted)

Cationicanionic

Dr Mahmoud Mokhtar Ahmed Ibrahim


20/99

Pharmacokinetics of liposomes:

After I.V injection liposomes located in

macrophages in liver, spleen and bone

marrow.

Factors influencing liposomes pharmacokinetics:

1- liposome lipid dosage:

a) Low dose, the elimination of both large and small

liposomes follows first order kinetics.

b) High dose, the elimination of large liposomes from blood

follows zero order, however the elimination of small

liposomes follows first order kinetics.



21/99

2- Liposome size:The clearance of large MLV is biphasic.

Fast elimination phase due to RES and slow elimination one due to liver parenchymalcells.

The biphasic elimination could be due to heterogenous size liposomes. Large vesiclesbeing eliminated rapidly and small ones eliminated slowly.

3- liposomes composition: Neutral and +ve charged liposomes slowly cleared compared tove charged

ones.

Clearance of smallve charged liposomes is biphasic in semilog plots of

concentration against time. Largeve liposomes taken up by blood monocytes more efficiently than neutral

or +ve lipids.

-ve liposomes taken up by the lung more efficiently than neutral or +veliposomes.

Addition of cholesterol to liposomes decrease association with plasmalipoproteines and uptake by liver.

Liposomes carrying a specific ligand like antibody or cell adhesion molecules havemore rapid blood clearance than native liposomes.

Liposomes with PEG physically attached or chemically attached to the surfaceStealth liposomes are long circulating and very slow elimination ratescompared to native liposomes.



22/99

4/11/2010 22

Modes of Liposome/Cell Interaction

Adsorption Endocytosis or phagocytosis

Fusion Lipid transfer



23/99

Stability and storage

Physical stability: fusion, aggregation and leakage of the entrapped drugcould happen upon storage.

Chemical stability: hydrolysis of phospholipids lead to lysophospholipidsdetergents which disrupt liposomal membranes. So liposomes should bestored at pH close to 7.

Hydrolysis rate affected by temp. so it is suggested to keep liposomesrefrigerated. However freezing could lead to rupture or fracture ofliposomal membranes and loss of entrapped components and change insize distributions.

Addition of cryoprotectants like sucrose, trehalose, glucose, etc. helpincrease stability and decrease the rate of hydrolysis.

Antioxidants required to inhibit lipid peroxidation.



24/99

4/11/2010 24

Sterilization of liposomes

a) Heat sterilization by autoclaving: require certainconditions however loss of liposome-associated

agent (retention loss) and chemical degradation of

liposome components and/or associated agent can

occur.

b) Sterilization by -irradiation

c) Filtration sterilization

d) Aseptic production procedures



25/99

4/11/2010 25

Pharmaceutical applications of liposomes

In vitro enhancement of the antibacterial activity

In vivo enhancement of biological activity.

1- Oral administration (Enhancing of buccal delivery of

insulin) .

2- Topical and transdermal application

(corticosteroids)

3- Ophthalmic drug delivery system Sustained release ,Prolonged retention of drugs

4- Pulmonary administration (immunoglobulins)



26/99


27/99

Liposomes for infections and parasitic disease

treatments

Clearance of liposomes by macrophages and

RES where the parasites exists lead to

effective antibiotic, antifungal and

antiparasitic treatments. Ex: Leishmaniasis(antimony: antimonials drugs which in higher

concentrations can cause cardiac, liver and

kidney damage). Amphterecin B (antifungal) isanother ex.



28/99

4/11/2010 28

Doxil

Chemotherapy drug doxorubinAnemia, damage to veins and tissue at

injection, decrease

platelet and WBC count, toxic to

Treats Kaposis sarcoma lesions or

cancer tumors

Modifications of liposome stealthkeeps doxorubin in blood for 50 hours instead of

20 minutes so liposomes can penetrate through gaps and

defects of blood veins into tumor and so

concentrates at KS lesions and tumors

Anti cancer therapy



29/99



30/99

4/11/2010 30

Liposomes extravasate through gaps/defects in tumor blood

vessels deep into tumor mass

Liposomes in

tumor tissue

Liposomes in

blood vessels



31/99

Liposomal Corticosteroids injected directly into the site of inflammation

(Arthritic joints).Liposomes can deliver drugs into lungs (Nebulizers or inhalations) for treatment

of asthma, infections, or lung disorders.

Treatment of neonatal jaundice in animal model.

oral application of liposomes is limited due to enzymatic degradation in

stomach and duodenum.

Liposomes in bioengineeringDelivery of genetic material (DNA) into cells in order to force them to

produce certain proteins (transfection vectors).

Liposomes in cosmetics

Lipids are well hydrated and reduce dehydration and dryness of the skin and

as a supply to replenish lipids.

Other applications



32/99

4/11/2010 32

Problems with Liposomal

Preparations of Drugs

$$$$ very high costFungizone $40.58 Amphotec $2334

Doxil $1200 per treatment, twice the cost of normal protocol

of chemotherapy and drugs

Lack long term stability (short shelf life)

Treated by: Freeze dry, proliposome and pH adjustment

Low Pay Load - poor encapsulation

Due to Physical and chemical instability

Of Polar drugs and drugs without opposite charge

Treated by:Modifications for preparation methods and lipid

compositionDr Mahmoud Mokhtar Ahmed Ibrahim


33/99


34/99


35/99

Fall single-chain lipids with large

head group areas, e.g.,

lysophosphatidylcholine.

Some Nonionic surfactants

Lecithins,

disugardiglycerids, fluid

chains

Anionic lipids, Phosphatidyl

ethanol amine, saturated frozen

chains

Double chain lipid with

small head group areas.



36/99


37/99


38/99

Reduction in vesicles size

1- Sonication

2- Extrusion

3- Combination of sonication and filtration

4- High pressure homogenization.

5- Microfluidizer



39/99

Microfluidizer

Microfluidizer high shear fluid processing technology is used for particle

size reduction of suspensions and emulsions to sub-micron levels



40/99

Drug loading optimization

A) Units for reporting drug loads: often quoted as % drug

encapsulated.

Factors affecting drug loading

1) Chemical structure: chemical nature of the niosomal membrane can be

manipulated by changing the nature of the hydrophilic and/or hydrophobic groups.

Ex. Sugars as cryoprotectants: according to different levels of hydration of different

sugars EE% for aqueous solute decreased in the following orderSucrose>glucose>mannose>galactose>lactose.

2) DCP or SA charge inducing agents: increase EE%.

3) Dehydration rehydration method increase EE%.



41/99


42/99

Toxicity of niosomes (CnEOx)

1- Increase in alkyl chain length (Cn) lead to decrease in toxicity. Increase in gel toliquid transition.

2- Increase in EOx chain length increase toxicity due to decrease in gel to liquid

transition. Generally gel state is less toxic than liquid phase.

3- Ester form (more labile to hydrolysis) less toxic than ether linkage.

4- HLB of no influence on toxicity.



43/99

Stability of niosomes

Physical Stability means constant particle size and constant level of entrapped drug

Chemical stability means reduction in hydrolysis and peroxidation rates.

Should be stored dry to have maximum stability.

1- addition of cholesterol:

2- control of storage temperature: increasing temperature change the nature of

system and affect release rate.

3- High detergent concentration: cause solubilization of vesicles to micells or largeaggregates.

4- Addition of polymerized surfactant

5- Inclusion of charging molecules DCP or SA Prevents aggregation.

6- Decrease water/air interface prevent crystallization of surfactant monomers.4/11/2010 43Dr Mahmoud Mokhtar Ahmed Ibrahim


44/99

Therapeutic applications

1- I.V administration:a) Anti infective agents as administration of sodium stibogluconate in hexadecyl

triglycerol ether (C16G3) niosomes or DPPC liposomes containing 20% and 30%

cholesterol is an ex.

Higher levels of antimony found in liver compared to solution forms.No differences between niosomes and liposomes.

Results

Antimony still in high levels in serum after 4 hours of administration in case of

solution form however negligible amounts of antimony in serum incase of vesicles.

b) Anti cancer drugs, methotrexate and adriamicine (doxrubicin) by Niosomal I.V

administration, increased drug levels in tumors and decreased drug levels in different

organs like heart so decreased toxicity. Decrease the tumor growth in lungs.


2 O l t


45/99

2- Oral route:

Due to the influence of gastric juice, enzymes and bile salts

on phospholipids, liposomes are unstable when intakenoraly.

Niosomes on the other hand are more stable due to ether

linkage, absorption of drugs is enhanced and consequently

become more effective.

Ex: niosomal methotrexate: higher drug absorption rates

compared to solution forms. Higher drug concentrations in

serum, liver, and brain.

Lower drug concentration found in feces when using

niosomes compared to free drug .



46/99

3- Transdermal route

Interactions of vesicles with skin:

1- direct penetration of intact niosomes into stratum corneum.

Micro-reservoirs.

2- Fusion of niosomes with lipid bilayer in stratum corneum ,

penetration enhancers.

4- Ophthalmic route:

Cyclopentolate niosomes (polysorbate 20, cholesterol)

penetrate cornea in a pH manner. Increased penetration in

pH5.5 and decreased in pH 7.4.


Wh U Li d i


47/99

4/11/2010 47

Inactive: Unmodified liposomes gather in specific tissuereticuloendothelial system

Active: alter liposome surface with ligand (antibodies,enzymes, protein A, sugars)

For Drug Targeting

Why Use Liposomes and niosomes

in Drug Delivery?

Gene Therapy, Anti Tumor And

Chemo-Therapy, Vaccines.




48/99

4/11/2010 48

Exert Protection effect

They Decrease harmful side effects

Affect Pharmokinetics - efficacy andtoxicity of drugsThey Change the absorbance and biodistribution

By Changing where drug accumulates in the body

They Protect drug from either oxidation or

enzymatic and biological evironment

They Deliver drug in desired form

Why Use Liposomes and niosomesin Drug Delivery?

So they enhance the availability of compounds



49/99

4/11/2010 49

Affect Release of entrapped drugAffect the time in which the drug is released

Prolong time -increase duration of action and

decrease administration frequency

Release of drugs Dependent on drug and liposomeproperties

Liposome composition, pH and osmotic gradient, and

environment


in Drug Delivery?



50/99

4/11/2010 50

Improved dispersion of difficult- tosolubilize

compounds.

A means for entrapment and delivery of a

variety of agents

Improved adhesion on the membrane surface

and sustained drug release. (Topically)


in Drug Delivery?



51/99

4/11/2010 51

Enhance penetration into the skin.

Reduced skin irritation and toxicity of thecarrier so they are used In cosmetic

preparations.

Chelation therapy for the treatment of heavy

metal poisoning


in Drug Delivery?



52/99

4/11/2010 52

Bio-membranes in study of membranes



53/99

The Microemulsion concept was introduced as earlyas 1940s by Hoar and Schulman who generated aclear single-phase solution by titrating a milkyemulsion with hexanol.

However, the microemulsion definition provided byDanielson and Lindman in 1981 will be used as thepoint of reference.

Microemulsion is thus defined as a system of water,oil and amphiphile which is single optically isotropicand thermodynamically stable liquid solution.

Microemulsion



54/99



55/99



56/99

Or microemulsions can be defined as: Transparent

thermodynamically stable dispersion of water and oil

stabilized by surfactant and co-surfactant. Particle size smaller than 0.1 um.

Advantages of the use of microemulsion as drug carrier

systems:

1- Thermodynamic stability allow self emulsification.

2- Technology is very simple, no significant energy

required.

3- Super solvents of drugs due to SAA and Cosurfactant.4- w/o or o/w types microemulsions can serve as potential

reservoirs to drugs.



57/99

5- Droplet size is below 100 nm allow great interfacial area

from which the drug is quickly absorbed in vivo or in vitro.

6- Sterilized by filtration as mean diameter below 0.22 um.

7- Auto-oxidation of lipids in o/w is slower than in case of

emulsions or micellar solution. (linoleic acid ex.)

8- Can carry both hydrophilic and lipophilic drugs in the same

microemulsion.

9- They are of low viscosity.

10- can improve the efficacy of drugs, allow the total dose to

be reduced.

11- may become unstable at high or low temperature

however this is reversible as they return back to stable

forms at room temperature.


F t li iti th f i l i


58/99

Factors limiting the use of microemulsion

in pharmacy

Components specially SAA and Cosurfactant may

not be acceptable.

Thermodynamic stability should be maintained

over temp. range 4-40 C. Pressure must be kept constant during storage.

Salinity affect the stability of the produced

microemulsion.

The amounts of surfactant and cosurfactant are

usually higher than required in case of emulsions.



59/99

Formation of microemulsion

The reduction in the interfacial tension by 3 or 4

magnitude is a requirement for stability.

Medium chain length alcohol addition to emulsion

of oil/water/soap. At certain alcohol concentration, turbid emulsion

become transparent microemulsion.

Addition of alcohol help decrease the interfacial

tension between water/oil up to negative values.



60/99

Why thermodynamic stability?

Three contributions of free energy in the formation

of microemulsion:

1- Interfacial free energy. (0 or negative if surface

tension 10-2

0r 10-3

dyne/cm).2- Energy of interaction between droplets (negligible)

3- Entropy of the dispersion (entropy is a measure of

the unavailability of a system s energy to do work)

(0 or negative if surface tension 10-2 0r 10-3

dyne/cm).


For the microemulsion formation a SAA with a


61/99

For the microemulsion formation a SAA with a

well balanced HL properties able to reduce the

interfacial tension to 0 or negative values

required.

SAA with unbalanced HL properties are unable to

reduce the interfacial tension below 1 dyne/cm so

to form microemulsion, a cosurfactant is required. HLB temperature, or PIT (phase inversion temp),

the temperature the HL properties of SAA is

balanced. At PIT, maximum oil solubilization in water and

ultra low interfacial tensions are achieved.


St t


62/99

Structure

Two main structures:

1- Discrete microemulsions Microemulsionspoor in water or oil form globular structures.

(domains of one pseudo phase (oil or water)

dispersed in another pseudo phase). Onecomponent is present in a higher proportion

than the other with little SAA.

2- Bicontinueous structure: Those with similarwater:oil amounts present bicontinuous

structured microemulsion.



63/99

Microemulsion One phase dispersed in the other.

Thermodynamicaly stable.

Structure is stable independent oftime.

ultra low interfacial tension, totalfree energy is negligible, sononspherical droplets canpresent.

Contain particles of sizesbetween100 A0 and 1000A0).

Spontaneously formed (no energyinput required).

Due to higher Surface area,higher absorption rates.

Emulsion One phase dispersed in the other

Unstable.

Structure is time dependant.

Globules are spherical or nearly

spherical of high energetic term. Size is 2 to 50 microns.

High energy input required toform.

Lower absorption rates.


CPP=V/al


64/99

/

The area of polar head groups (a) can be measured atwater/air interface or oil/water interface (Gibbs isotherm).

The length of hydrophobic tails calculated from values ofTanford).

The volume of hydrocarbon tail calculated from the density ofbulk hydrocarbon.

The geometry of surfactant molecules at the interface plays

an important role. Israelachivilli et al., considers that the amphiphile molecules

regarded as two pieces structure: polar head and hydrophobictail.

The possible geometry of the interface film formed is

dependant on SAA intrinsic geometry. CPP


65/99

Hydrocarbon penetration and cosurfactant presence may

completely change the structure from the natural tendency. Oil penetration in the hydrocarbon tail increase the

hydrophobic volume so CPP INCREASED.

Cosurfactants (medium chain alcohols) co-adsorb at theinterface leading to reduction in CPP.

SAA concentration, and the ratio of oil/water have highimpact on microemulsion structure.

Increasing ionic SAA produce high ionic strength with areduction of polar head area and increase in CPP.

Increasing the amounts of the internal pseudophase may

produce phase separation if SAA is low. Electrolytes might influence the natural curvature of

amphiphile mainly ionic ones.

Temperature also can affect the natural curvature (mainlynonionic SAA).

g

formation



66/99


67/99


68/99

Win

I

Win

II

S

W O

R1



69/99

Methods of Characterization:1) Phase behavior: provide information on boundaries of

different phases as a function of composition variables.2) Scattering technique: by SAXS (small angle X-ray scattering)

give information of drop size and shape.

or by SANS (small angle neutron scattering) characterize

shape, size and SAA layer.3) NMR study: the structure and dynamics of microemulsion.

4) Electron microscopy:

5) Interfacial tension measurments: ultralow interfacialtension can be determined by spinning-drop apparatus.

6) Electrical conductivity : determine different phasesaccording to higher or lower conductivity.

7) Viscosity: to determine the droplet radius.


Partition of drug among phases of


70/99

Partition of drug among phases of

microemulsion:

Drug partitioned to three phases: the water, the oiland interphace.

So partition coefficient through these phases Pcosshould be determined.

The log of coefficient of permeation through ahydrophilic membranes were inversely proportionalto log Pcos.

The higher the concentration of the drug in theinternal phase the lower the amount releasedovertime from the system.



71/99

Pharmaceutical Applications of


72/99

Pharmaceutical Applications of

microemulsion

It increases solubility of poor soluble drugs.

It increases therapeutic activity.

Allow a reduction in the total dose needed.

So minimize toxic side effects.



73/99

1)Percutaneous administration:

Transport from microemulsions is better than from

ointments, gels, or creams. This is due to: drug is completely dissolved in microemulsion,

of high concentration and the dispersed phase can act as areservoir for the drug making it possible to maintain aconstant concentration in the continuous phase and pseudo

order kinetics can be achieved. Surfactants and cosurfactants acts a enhancers for drug

release.

Ex1: Tetracycline HCl release is better from microemulsions.

EX2: Tizanidine (a short-acting muscle relaxant) of high

absorption from microemulsion and this found not possiblefrom other dosage forms.



74/99

2) Occular administration

O/W microemulsion used for occular adminstration ofsome drugs.

To dissolve poor soluble drugs, to increase absorption,decrease the wash out and prolong release time.

Ex: Lecithin T80 microemulsion systems used to dissolvepoor soluble drugs like atropine, chloramphenicol andindomethacin and used for local ocular therapy and highabsorption of drugs , low physiological irritation, andprolonged release.

Ex2: enhance amount transport through cornea anddecrease the drug transport through the conjunctivawhich localize drug effect to eye.



75/99

3) Oral administration:

Protect the drug from GIT degradation and increase

drug absorption.

Ex1: Cyclosporin in microemulsion: increased

absorption, and bioavailability more than

commercial dosage forms.EX2: improve hypoglycemic effect ofinsulin when

given orally.



76/99

4) Parentral administration:

O/W microemulsions: used as carriers for lipophilic

drugs to attain prolonged release. Can administer

I.M, I.V., or S.C.

W/O microemulsions: parentral administration of

hydrophilic drugs. For I.M and S.C.

Application in other fields:1) Cosmetics: transparent, attractive for customers. Used as shampoo and skin

cleaner, hair conditioner.

2) Cleaning fluids: for dirties and stain removal.

3) Floor polisher: due to high stability and small particle size enable theformation of high glassy layer on the floor.


Th f i l i d d li hi l h b


77/99

The use of microemulsions as drug delivery vehicle has been anexciting and attractive area of research because of its manypotential and extraordinary benefits.

Microemulsions offer an interesting and potentially quite powerfulalternative carrier system for drug delivery because of their highsolubilization capacity, transparency, thermodynamic stability, easeof preparation, and high diffusion and absorption rates whencompared to solvent without the surfactant system.

Microemulsion system has considerable potential to act as a drug

delivery vehicle by incorporating a wide range of drug molecules. Microemulsion has got advantage like excellent thermodynamicstability, high drug solubilization capacity, improved oralbioavailability and protection against enzymatic hydrolysis.

The only problem with microemulsion is poor palatability due tothe lipid content leading to the poor patient compliance.

Moreover due to their water content, microemulsions cannot beencapsulated in soft gelatin or hard gelatin capsules.


All th bl b b f l ti


78/99

All these problems may be overcome by formulating orconverting microemulsion into another stable dosage formlike conversion of microemulsion containing drug into tablet

by adsorbing onto the solid support i.e. adsorbent, orincorporation of microemulsion in gel bases etc.

Drug containing microemulsions can be adsorbed onto solidparticles which may be further formulated into solid dosageform to improve the bioavailability of drugs.

By using this concept Sangeeta V. et.al have developed a newdosage form that is microemulsion as solid dosage form(United States Patent 6280770). They used poorly bioavailabledrug like testosterone propionate in their work, which gave

good results.


l


79/99

Nanoparticles Solid colloidal particles ranging in size from 10 to 1000 nm.

Composed of macromolecular material (polymer) in whichthe active principle is dissolved, entrapped, encapsulated,adsorbed or attached to nanoparticle surface.

May be as solid matrices or nanocapsules with a shell likewall.

It is often difficult to distinguish between continuous matrixor shell like wall so the term nanoparticles used.



80/99

Scanning electron micrographs of PLGA nanoparticles preparedby ESE method using DCM (a) and Et-Ac (b), nanoprecipitationmethod using acetone as a solvent (c), and mixed micellemethod using methoxy Peg 350 as solvent (d).


d


81/99

Advantages:

Of better stability than liposomes.

Can be used for I.V, I.M, or S.C injection.

Reduction in size minimize the irritation at site of

injection.

Biodegradable and non toxic and of reasonable shelf life(up to one year).

After I.V injection they are mainly taken by RES and so

can be targeted to liver and phagocytotic cells.

By modifying surface characteristics by coating with SAA,

it is possible to target the drug to spleen more than liver.


P i f i l


82/99

Preparation of nanoparticles:(i) dispersion of the preformed polymers.PLA, PLGA, and poly (E-caprolactone) are examples of biodegradable

polymers used for nanoparticles formation.

a) Solvent evaporation method:the polymer is dissolved in an organic solvent like dichloromethane,

chloroform or ethyl acetate. The drug is dissolved or dispersed inthe polymer solution. O/W emulsion is then made by using asurfactant / emulsifying agent like gelatin, poly(vinyl alcohol),polysorbate-80, poloxamer-188, etc.

After the formation of a stable emulsion, the organic solvent isevaporated either by increasing the temperature /under pressure

or by continuous stirring.W/O/W technique is used for water soluble drugs.

Both the above methods use a high-speed homogenization orsonication for emulsification.



83/99

c) Polymer nanoprecipitation (or solvent


84/99

c) Polymer nanoprecipitation (or solventdisplacement method):

Another method of preparation for nanoparticles that was

originally developed and patented by Fessi and co-workers.

This technique is based on the dissolution of the polymer ina water soluble solvent (acetone for PLGAs), followed byits dispersion in a continuous external phase, in which the

polymer is insoluble.The main difference between the emulsion and

nanoprecipitation technique is the miscibility of the

(ii) Polymerization methods


85/99

(ii) Polymerization methods

Nanoparticles prepared by the polymerization of monomers.

Polyalkylcyanoacrylate is a biodegradable polymer of interest

prepared by polymerization method. It has been used as tissueadhesive in surgery as it is well tolerated in vivo.

Ex: methyl or ethyl cyanoacrylate dispersed in aqueous acidic medium

in the presence of polysorbate-20 as a surfactant without

irradiation or an initiator. Here, the cyanoacrylic monomer is added

to an aqueous solution of a surface-active agent (polymerization

medium) under vigorous mechanical stirring to polymerize

alkylcyanoacrylate at ambient temperature.

Drug is dissolved in the polymerization medium either before the

addition of the monomer or at the end of the polymerizationreaction.

The NP suspension is then purified by ultracentrifugation or by re-

suspending the particles in an isotonic surfactant free medium.

The mechanism of polymerization of PACA monomer is given below.4/11/2010 85Dr Mahmoud Mokhtar Ahmed Ibrahim


86/99

Polymerization follows the anionic mechanism, since it isinitiated in the presence of nucleophilic initiators like OH- , CH3O- and CH3 COO

- leading to the formation of NPs of low

molecular mass due to rapid polymerization. Rapidly

biodegradable and eliminated from the body in few days.4/11/2010 86Dr Mahmoud Mokhtar Ahmed Ibrahim

During polymerization various


87/99

During polymerization, various

stabilizers like dextran-70,

dextran-40, dextran-10,

poloxamer-188, -184, -237, etcare added. In addition, some

surfactant like polysorbate-20, -

40 or -80 are also used.

Particle size and molecular massof NPs depend upon the type

and concentration of the

stabilizer and/or surfactant used.


Examples of polymerization of monomers to form nanoparticles:


88/99

1- Poly (methylmethacrylate) nanoparticles.

Monomeric methylmethacrylate is dissolved in water in 1.5%

concentration, Polymerization initiated by high energyirradiation or chemically by ammonium potassiumperoxodisulfate and heating.

They are very slowly biodegradable so can be used for vaccinedelivery to achieve prolonged immune response.

2- Acrylic copolymer nanoparticles:Monomers like methyl methacrylate, 2-hydroxy methacrylate,

metha acrylic acid, and acrylamide are used.

Gama irradiation was employed as initiator for polymerization.

3- polystyrene nanoparticles: styrene monomer is used in asimilar polymerization technique like acrylates, howeverstyrene water solubility is lower.

4- Poly (vinyl pyridine) nanoparticles.


NPs prepared from hydrophilic polymers:


89/99

NPs prepared from hydrophilic polymers:

hydrophilic polymers like chitosan, sodium alginate,gelatin, BSA, and others.

Chitosan nanoparticles can be prepared by Ionic gelationmethod.

Mixture of two aqueous phases, of which one containschitosan and the other contains a polyanion sodium

tripolyphosphate (TPP). positively charged amino groupof chitosan interacts with the negatively charged TPP.

Nanoparticles of the size 200 nm to 1000 nm areproduced.

These NPs have shown good association with proteins,such as bovine serum albumin, tetanus toxoid anddiptaheria toxoid, insulin as well as oligonucleotide.


Emulsion coacervation method also used to prepare


90/99

Emulsion coacervation method also used to prepare

chitosan nanoparticles:

chitosan and the drug to be loaded were dissolved in

water and water-in-oil emulsion prepared in liquid

paraffin using an emulsifying agent. To this stable

emulsion, another emulsion of NaOH in liquid paraffin

was added.When in contact with NaOH, chitosan NPs were

produced by the coacervation of the polymer.

Methods like salting out, and aldehyde cross linking

also applied to produce nanoparticles from gelatin,

and BSA, respectively.


D l di


91/99

Drug loading:

Drug loading into nanoparticles is achieved by two methods:

1) By incorporating the drug at the time of NP production.

2) By adsorbing the drug after the formation of NPs by incubating

them in the drug solution.

3) By chemical conjugation into NPs.Ex: The conjugated doxorubicinPLGA and doxorubicin-loaded

PLGA nanoparticles were prepared by Emulsion solvent

diffusion method. The EE% was 96.6% for chemically bound

doxorubicin (doxorubicinPLGA), however only 6.7% for

doxorubicin loaded physically.


Nanoparticles purification


92/99

Nanoparticles purification

Nanoparticle suspension withsurfactants and free non

entrapped drug.

Centrifugation

17,000 g

Supernatant collected and

nanoparticles resuspended in water

Re-centrifugetwice

Supernatant collected and

nanoparticles suspended in water

Suspension is then freeze

dried

In order to protect nanoparticles from aggregation after freeze drying, sugars like trehalose,

glucose, or mannitol could be added to nanoparticles suspension as cryoprotectants.


Drug loading analysis: Determination of


93/99

g g y

the entrapment efficiency (protein as Ex.)

Indirect method Direct method

Analysis of the supernatant after

centrifugation and washingLyses of the particles in

acetone

Protein precipitated

and can be assayed by

BCA

Centrifugation


Characterization of nanoparticles


94/99

Characterization of nanoparticles

Parameter Method

Particle size Photon correlation

spectroscopy,

transmission EM, SEM.

Molecular weight Gel chromatography.

Surface charge Electrophoresis.

Hydrophobicity Contact angle

measurement


Mechanisms of Drug release from nanoparticles


95/99

(i) desorption of the surface-bound /adsorbed drug.

(ii) diffusion through the NP matrix.(iii) Diffusion (in case of nanocapsules) through the polymer

wall.

(iv) NP matrix erosion.

(v) a combined erosion / diffusion process.

f g f p

Methods to study the in vitro release are:

1) side-by-side diffusion cells with artificial or biomembranes.2) dialysis bag diffusion technique.

3) Ultracentrifugation.

4) Ultrafiltration technique.


Nanoparticle degradation


96/99

p g

1) By erosion of the polymer backbone under formation

of formaldehyde.2) By cleavage of the ester bond under the formation of

soluble acids.

Nanoparticle toxicityNanoparticles distributed very rapidly in the RES, especially theliver.

Toxicity decreases by increasing ester side chain length. An

exception is the methyl esters, showed lower toxicity than ethyl

esters.

Degradation products of nanoparticles could increase toxicity as

non degraded nanoparticles are less toxic than partially degraded

ones.


Application of nanoparticles


97/99

Application of nanoparticlesA) Delivery of cytostatic drugs loaded nanoparticles.

Nanoparticles showed high tendency to accumulate in tumorsafter I.V administration due to:

1) The attachment of the particles to the inner walls of bloodvessels supplying tumors.

2) Endocytosis of the particles by endothelial cells lining the

tumor blood vessels.B) Delivery of anti-infective agents:

treatment of some intracellular infections is sometimes verydifficult due to the inability of the anti-infective agent topenetrate the cells. Nanoparticles however can carry the

drug and by endocytosis it can deliver it inside infectedcells.

Target cells are macreophages in the liver (Kupffer cells) and thespleen as well as circulating monocytesr and in lung(alveolar macrophages).


C) Targeting of nanoparticles to specific organ or tissue:


98/99

Occur of certain nanoparticle surfaces are modified by

adsorbing or coating by different substances:

Ex1: incorporation of magnetic Fe3SO4 into

nanoparticles enables the preparation of

magnetically responsive nanoparticles.

So, by placing the magnet close the target organleading to increase concentration of magnetic

particles in this organ. Drugs so can release in high

concentration localized in that organ and hence

lower concentrations in other organs.

EX2: PEG coating, surfactant coating and etc.


Body distribution of nanoparticles


99/99

Body distribution of nanoparticles

1) After I.V administration: to RES.

2) After oral administration: concentrated into payer`s

batches in the intestine by endocytosis. 14C labled

polymers used in this study.

3) After ocular application: 1% adheres to the corneaand to higher extent in the conjunctiva for more

than 6 hours due to surface mucoadhesion.

2nd term (ceutics) colloidal drug delivery systems

Documents