A Seminar

on

Niosome As Drug Carrier

Keyur Vasava… 1

Introduction

• Development of new drug , improving safety and efficacy of existing drugs is difficult, expensive and time consuming

• At present, no available drug delivery system behaves ideally achieving all the lofty

goals

• Encapsulation of the drug in vesicular structures is one of the promising system

• such as liposomes, niosomes, transfersomes, and pharmacosomes etc

• It delivers drug directly to the site of action, leading to reduction of drug toxicity with no adverse effects

• Vesicular drug delivery reduces the cost of therapy by improving bioavailability of

medication and also solves the problems of drug insolubility, instability and rapid degradation

• Niosomes are a novel drug delivery system, in which the medication is encapsulated

in a vesicle,composed of a bilayer of non-ionic surface active agents and hence the name niosomes

• The niosomes are very small, and microscopic in size. Their size lies in the

nanometric scale. History of Niosome

• 1st Niosome was reported in 17th centuries in cosmetic industry.

• In 1985, niosome are studied as an alternative to liposome found baillie.

• In 1990, Kronberg prepared niosome.

• In 1993, Florence was found that various types non-ionic surfactants used as

alternative to phospholipids in the fabrication of vesicular system.

• Alan Rogerson, Colin cable, Yoshioka & Parinya have explored niosome structure and function.

Defination

Niosomes are synthetic microscopic vesicles consisting of an aqueous core

enclosed in a bilayer consisting of cholesterol and one or more nonionic surfactants. Structure of Niosomes

• Niosomes are microscopic lamellar structures.

2

• Basic structural components are

• Non ionic surfctant

• Cholesterol

• Dicetyl phosphate

• A number of non- ionic surfactants have been used to prepare vesicles viz. polyglycerol alkyl ether, glucosyl dialkyl ethers, crown ethers, ester linked surfactants, polyoxyethylene alkyl ether and a series of spans and tweens.

• CPP(Critical Packing Parameter) = v/Ic * a0

where v = hydrophobic group volume,

Ic = the critcal hydrophobic group length,

a0 = the area of hydrophilic head group.

CPP value should be between 0-5 to 1.0 for bilayer micelle formation. General Characteristics of Niosome

• Biocompatible, biodegradable, non-toxic, non immunogenic and non-carcinogenic

• The ability of nonionic surfactant to form bilayer vesicles is dependant on the HLB

value of the surfactant, the chemical structure of the components and the critical packing parameter.

• Niosomes can be characterized by their size distribution studies.

3

• High resistance to hydrolytic degradation

• The properties of niosome depends both on composition of the bilayer & on method of their production.

Advantages of Niosome

• The vesicle suspension is water–based vehicle more patient compliance than oily

preparation.

• The vesicles may act as a depot, releasing the drug in a controllable manner.

• They are osmotically active and stable.

• Handling and storage of surfactants requires no special conditions.

• They improve oral bioavailability of poorly absorbed drugs and enhance skin penetration of drugs.

• Niosome improves therapeutic performance of drug molecules.

Disadvantages of Niosome

• Aqueous suspension of niosome may exhibit fusion, aggregation leaching or

hydrolysis of entrapped drug, thus limiting the shelf life of niosome dispersion.

• Time consuming

• Requires specialized equipment

• Inefficient drug loading Contrast of Niosomes Vs liposomes

Sr no Niosomes liposomes

1. Less Expensive More expensive 2. Chemically Stable Chemically unstable 3. Niosomes are prepared

from uncharged single- chain surfactant

Liposomes are prepared from double-chain phospholipids

4. They do not require special storage and handling.

They require special storage, handling & purity of natural phospholipid is variable.

4

5. Non ionic drugs carriers are safer.

The ionic drugs carriers are relatively toxic & unsuitable

Comparision of niosomes and liposomes

• Properties of both depends on composition of bilayer and method of production

• Increase in surfactant lipophilicity, increases entrapment efficiency.

• Increase in cholesterol concentration, decreases in entrapment efficiency.

• Lipophilic surfactant forms mean size reduction.

Method of preparation:

Niosomes are prepared by the following general steps.

• Hydration of mixture of surfactant/lipid at elevated temperature.

• Sizing of niosomes.

• Removal of unentrapped material from the vesicles

For the formation of noisome phase transition temperature plays most important role. It should be done above the phase transition temperature.

Methods of preparation

1. Ether Injection

2. Hand Shaking Method

3. The “Bubble” Method

4. Reverse Phase Evaporation

5. Sonication

6. Micro Fluidization

7. Trans Membrane pH Gradient Drug Uptake Process (remote Loading)

8. Formation of Niosomes From Proniosomes

5

Step of preparation

• Hydration

Hydration of the mixture of the surfactant/ lipid at elevated temperature can be done by using following method.

• Ether injection method

• This method is based on slow injection of surfactant : cholesterol solution in ether

through 14 gauge needle into a preheated aqueous phase maintained at 600C.

• Slow vaporization of ether resulting into a formation of ether gradient at ether-water interface which leads to formation of single layered vesicles.

• Depending upon the conditions used, the diameter of the vesicle range from 50 to

1000 nm.

B. Hand shaking method

(Thin film hydration technique)

• Surfactant and cholesterol are dissolved in a volatile organic solvent (diethyl ether, chloroform or methanol) in a round bottom flask.

• The organic solvent is removed under vaccum at room temperature using rotary

evaporator leaving a thin layer of solid mixture deposited on the wall of the flask.

• The dried surfactant film can be rehydrated with aqueous phase at 0-60°C with gentle agitation.

• This process forms large multilamellar niosomes.

C. The “Bubble” Method

• It is novel technique for the one step preparation of liposomes and niosomes without the use of organic solvents.

• The bubbling unit consists of round-bottomed flask with three necks positioned in

water bath to control the temperature.

• Water-cooled reflux and thermometer is positioned in the first and second neck and nitrogen supply through the third neck.

• Cholesterol and surfactant are dispersed together in this buffer (pH 7.4) at 70°C, the

dispersion mixed for 15 seconds with high shear homogenizer and immediately afterwards “bubbled at 70°C using nitrogen gas.

D. Reverse Phase Evaporation Technique (REV)

6

• Cholesterol and surfactant (1:1) are dissolved in a mixture of ether and chloroform.

• An aqueous phase containing drug is added to this and the resulting two phases are sonicated at 4-5°C. The clear gel formed is further sonicated after the addition of a small amount of phosphate buffered saline (PBS).

• The organic phase is removed at 40°C under low pressure. The resulting viscous

niosome suspension is diluted with PBS and heated on a water bath at 60°C for 10 min to yield niosomes.

• Sizing of niosomes,

The size ranges of niosomes have a major effect on their fate in vivo and in vitro. Hence, size reduction stage of noisome is essential after hydration stage. The more impoetant methods are given below.

A. Sonication

• In this method, an aliquot of drug solution in buffer is added to the

surfactant/cholesterol mixture in a 10-ml glass vial.

• The mixture is probe sonicated at 60°C for 3 minutes using a sonicator with a titanium probe to yield multi lamellar vesicles.

• For small volume samples probe sonicator is used while for large volume samples

bath sonicator is used.

• Greater size reduction can be achieved by this method.

B . Micro fluidization

• Micro fluidization is a recent technique which is based on submerged jet principle in which two fluidized streams interact at ultra high velocities, in precisely defined micro channels within the interaction chamber.

• The result is a greater uniformity, smaller size and better reproducibility of niosomes

formed.

• Nucleopore filters extrusion

• Size of niosomes reduces to nano range by extrusion of noisome through nucleopore filters of pore size 100nm.

• Noisome of nano size range can be achieved.

7

Another method of preparation of niosomes:

• Remote loading

In this method, drug loading can be done by use of pH gradient across. The lower pH value inside noisome develops pH differential across the noisome membrane. The added basic drug in an unionized state passes the membrane of niosomes.after entering the drug into noisome inner chamber, it becomes ionized at lower pH and unable to leave the niosomes. The acidic pH within the niosomes interir thus acts as an intravesicular trap.

e.g vincristin sulphate niosomes prepared by this method

• Formation of niosomes from proniosomes Another method of producing niosomes is to coat a water-soluble carrier such as sorbitol with surfactant. The result of the coating process is a dry formulation. In which each water-soluble particle is covered with a thin film of dry surfactant. This preparation is termed “Proniosomes”. The niosomes are recognized by the addition of aqueous phase at T > Tm and brief agitation.

T = Temperature. Tm = mean phase transition temperature

• Removal of unentrapped material from the vesicles

The removal of unentrapped solute from the vesicles can be accomplished by various techniques, which include

• Gel Filtration

• Dialysis

• Centrifugation

8

Factors affecting vesicles size, entrapment efficiency and release characteristics

a) Drug

Entrapment of drug in niosomes increases vesicle size, probably by interaction of solute with surfactant head groups, increasing the charge and mutual repulsion of the surfactant bilayers, thereby increasing vesicle size.The hydrophilic lipophilic balance of the drug affects degree of entrapment.

b) Amount and type of surfactant The mean size of niosomes increases proportionally with increase in the HLB of surfactants like Span 85 (HLB 1.8) to Span 20 (HLB 8.6) because the surface free energy decreases with an increase in hydrophobicity of surfactant.

c) Cholesterol content and charge Inclusion of cholesterol in niosomes increases its hydrodynamic diameter and entrapment efficiency. An increase in cholesterol content of the bilayers resulted in a decrease in the release rate of encapsulated material and therefore an increase of the rigidity of the bilayers obtained. Presence of charge tends to increase the interlamellar distance between successive bilayers in multilamellar vesicle structure and leads to greater overall entrapped volume.

d) Methods of preparation Methods of preparation affects noisome characteristics. It mainly affects size, entrapment efficiency and retension of drug.

e) Resistance to osmotic stress Addition of a hypertonic salt to a suspension of niosomes brings about reduction in diameter. In hypotonic salt solution, there is initial slow release with slight swelling of vesicles probably due to inhibition of eluting fluid from vesicles, followed by faster release, which may be due to mechanical loosening of vesicles structure under osmotic stress.

Characterization of niosomes

• Physical characterization

• Chemical characterization

• Biological characterization

• Physical characterization

Sr no Parameter Analytical method

1. Vesicles shape & surface Transmission electron

9

morphology microscopy, Freeze-fracture electron

microscopy

2.

Mean vesicle size and size

distribution (submicron and micron

range)

Dynamic light scattering, zetasizer, Photon

correlation spectroscopy,

laser light scattering, gel permeation and gel exclusion

3. Surface charge Free-flow electrophoresis

4.

Phase behavior Freeze-fracture electron

microscopy, Differential scanning colorimetery

5.

Electrical surface potential and surface pH

Zeta potential measurements & pH sensitive probes

6.

Entrappment efficiency Amount entrapped/total amount added*100

2. Chemical characterization

Sr no Parameter Analytical methods

1. Cholesterol concentration Cholesterol oxidase assay and HPLC

2. Cholesterol auto-oxidation HPLC and TLC

3. Osmolarity

Osmometer

3. Biological characterization

Sr no Parameter Analytical methods

1.

Sterility Aerobic or anaerobic cultures

2.

Pyrogenicity

Limulus Amebocyte Lysate (LAL) test

3. Animal toxicity Monitoring survival rates, histology and pathology

10

a) Entrapment efficiency After preparing niosomal dispersion, unentrapped drug is separated by dialysis, centrifugation, or gel filtration and the drug remained entrapped in niosomes is determined by complete vesicle disruption using 50% n-propanol or 0.1% Triton X-100 and analysing the resultant solution by appropriate assay method for the drug. Where,

Entrapment efficiency (EF) = (Amount entrapped/ total amount) x 100

b) Vesicle diameter

Niosomes, similar to liposomes, assume spherical shape and so their diameter can be determined using light microscopy, photon correlation microscopy and freeze fracture electron microscopy.

Freeze thawing (keeping vesicles suspension at –20°C for 24 hrs and then heating to ambient temperature) of niosomes increases the vesicle diameter, which might be attributed to fusion of vesicles during the cycle.

c) In-vitro release

A method of in-vitro release rate study includes the use of dialysis tubing. A dialysis sac is washed and soaked in distilled water. The vesicle suspension is pipetted into a bag made up of the tubing and sealed. The bag containing the vesicles is placed in 200 ml of buffer solution in a 250 ml beaker with constant shaking at 25°C or 37°C. At various time intervals, the buffer is analyzed for the drug content by an appropriate assay method .

Therapeutic Application

1. Intravenous Route

Ipromide, Vincristine,Indomethacin, Colchicines, Rifampicin, Transferrin, Zidovudine, Cisplantin, amarogentin, Daunorubicin,

AmphotericinB.

2. Transdermal Route

Flurbiprofen, Piroxicam, Levonorgestrol, Nimeluside, Estradiol, Ketoconazole, Enoxacin, DNA loaded noisome,

Cyclosporine, Erythromycin, α interferon.

3. Oral Route

Vaccine, Polysaccharide Coated noisome, Cipro floxacin, Insulin.

11

4. Oncology Route

Methotrexate, Doxorubicin, adriamycin.

5. Ocular Route

Timolol, cyclopentolate

6. Nasal Route

Sumatriptan, Influenza

7. Immunological

Adjuvant

Bovine serum albumin, Hemoglobin

8. For treatment of Leishmaniasis

Stilbogluconat

REFERENCES 1. Sanjay K. Jain and N.K. Jain

Controlled and novel drug delivery system

2. Dr. Rakesh S. Patel, niosomes as a unique drug delivery system, www.pharmainfo.net

3. Mithal, B. M., A text book of pharmaceutical formulation, 6th Edn., vallabh prakashan, 6, 306-307

4. International journal of pharmaceutical Science and Nanotechnology volume 1,issue 1, April-June 2008

12