NIOSOMeS

SRAVANTHI.BINDUSTRIAL PHARMACY

Contents

IntroductionStructure of niosomes Materials used in the preparation of niosomesAdvantages & disadvantages of niosomesFormation of niosomes from proniosomesMethods of preparationSize reduction methods & drug loadingEncapsulation of drugs & removal of unentrapped drugCharacterization of niosomesStability of niosomes ApplicationsRecent advances in niosomesConclusion References

INTRODUCTIONNiosomes definition

Niosomes are essentially non-ionic surfactant based multilamellar or unilamellar vesicles in which an aqueous solution of solute (s) is entirely enclosed by a membrane resulted from the organization of surfactant macromolecules as bilayers”

Niosomes made-up of self assembly of hydrated nonionic surfactant molecules (eg: tweens and spans) with or with out cholesterol and dicetyl phosphate.

The assembly into closed bilayers is rarely spontaneous and usually involves some input of energy such as physical agitation or heat.

Niosomes also called as Nonionic surfactant vesicles or NSV s

Nios = non ionic surfactant somes = vesicles

NSVS results from the self assembly of hydrated surfactant monomers results in closed bilayer structuresDrug carriersBiodegradable, biocompatible and non immunogenicLarge qty of material can be encapsulated Very small ,microscopic in size.Most surface active agents when immersed in water yield micellar structures, how ever some surfactants can yield bilayered vesicles which are niosomes

STRUCTURE OF NIOSOMES

COMPARISION OF NIOSOMES VS LIPOSOMES

 Niosomes behave in-vivo like liposomes, prolonging the circulation of entrapped drug And altering its organ distribution and metabolic stability In both basic unit of assembly is Amphiphiles, but they phospholipids in liposomes and nonionic surfactants in niosomes.Both can entrap hydrophilic and lipophilic drugs.Both have same physical properties but differ in their chemical composition.Niosomes has higher chemical stability than liposomes.Niosomes made of uncharged single chain surfactant moleculesLiposomes made of neutral or charged double chain phospholipids.

Niosomes and liposomes are similar in-

Function Increase the bioavailability Decrease the clearence Used for targeted drug delivery Properties depends on both composition of bilayer and method of preparation

ADVANTAGES OF NIOSOMES OVER LIPOSOMES

Ester bonds of phospholipids are easily hydrolyzed, this can lead to phosphoryl migration at low PH

Peroxidation of unsaturated phospholipids.

This requires that purified phospholipids and liposomes have to be stored and handled in an inert (N2) atmosphere this problem is not seen with niosomes because these are made up of nonionic surfactants & these does require special storage condition

Phospholipid raw materials are naturally occurring substances and as such require

extensive purification thus making them costly

Niosomes has high adjuvanticity when compared to liposomes

ADVANTAGES OF NIOSOMES

They are osmotically active and stable. They increase the stability of the entrapped drug Handling and storage of surfactants do not require any special conditions Can increase the oral bioavailability of drugs Can enhance the skin penetration of drugs They can be used for oral, parenteral as well topical use

In cosmetics was first done by L’Oreal as they offered the following advantages:

The vesicle suspension being water based offers greater patient compliance over oil based systems

Since the structure of the niosome offers place to accommodate hydrophilic, lipophilic as well as amphiphilic drug moieties, they can be used for a variety of drugs.

The characteristics such as size, lamellarity etc. of the vesicle can be varied depending on the requirement.

The vesicles can act as a depot to release the drug slowly and offer a controlled release.

The surfactants are biodegradable, biocompatible, and non-immunogenic

Improve the therapeutic performance of the drug by protecting it from the biological environment and restricting effects to target cells, thereby reducing the clearance of the drug.

The Niosomal dispersions in an aqueous phase can be emulsified in a non-aqueous phase to control the release rate of the drug and administer normal vesicles in external non-aqueous phase.

USES OF NIOSOMES

Topical niosomes may serve as -

As solubilization matrix,

As a local depot for sustained release of dermally active compounds,

As penetration enhancers,

As rate-limiting membrane barrier for the modulation of systemic absorption of drugs

DISADVANTAGES/PROBLEMS ASSOCIATED WITH NIOSOMES

As high input of energy is required in the size reduction of niosomes, they aggregate and fuse togeather on prolonged storage

Physicochemical instability remains the major problem in the development of Niosomal system at industrial levels

DISTRIBUTION OF DRUGS IN NIOSOMES

Carriers for both lipophilic & hydrophilic drugs

Highly hydrophilic drugs are exclusively located in the aqueous domain

Highly lipophilic drugs are entrapped within the lipid bilayers of the niosomes

Drugs with intermediary partition coefficient equilibrate b/w lipid & aqueous domains

Different Niosomes

1. Bola-Surfactant containing Niosomes:

Niosomes made of alpha,omega-hexadecyl-bis-(1-aza-18-crown-6) (Bola-surfactant)-Span 80-cholesterol (2:3:1 molar ratio) are named as Bola-Surfactant containing Niosomes.

2. Proniosomes:

A dry product which may be hydrated immediately before use to yield aqueous Niosome dispersions. These ‘proniosomes’ minimize problems of Niosome physical stability such as aggregation, fusion and leaking, and provide additional convenience in transportation, distribution, storage, and dosing.

In short;1. Carrier + Surfactants = Proniosomes2. Proniosomes + H2O = Niosomes

In case of Frusemide delivery in the body, it has been found that proniosomal formulations have been found effective

MOLECULAR GEOMETRY & VESICLE FORMATION

Concept of Critical Packing Parameter (Israelachvili, 1985)

Prediction of vesicle forming ability is not a simply a matter of HLB

CPP = v/lca0 where v - hydrophobic group volume, lc - critical hydrophobic group length and a0 - area of the hydrophilic head group CPP between

0.5 and 1 likely to form vesicles.

<0.5 (indicating a large contribution from the hydrophilic head group area) is said to give spherical micelles.>1 (indicating a large contribution from the hydrophobic group volume) should produce inverted micelles, the latter presumably only in an oil phase, or precipitation would occur.

SmallUnilamellarVesicle(SUV)

LargeUnilamellarVesicle(LUV)

MultilamellarVesicle(MLV)

Typical Size Ranges: SLV: 20-50 nm – MLV:100-1000 nm

MATERIALS USED IN THE PREPARATION OF NIOSOMES

Non ionic surfactants – AmphiphilesSterols like cholesterolCharge inducers

Non-ionic surfactant structure

Hydrophilic head groups found in vesicle forming surfactantsGlycerol head groupsEthylene oxide head groups Crown ether head groups Polyhydroxy head groups Sugar head groups + amino acids Sugar head groups (galactose, mannose, glucose, lactose)

Hydrophobic moiety One or two alkyl or perfluoroalkyl groups or in certain cases a single

steroidal group. Alkyl group chain length is usually from C12–C18 (one, two or three

alkyl chains.

Perfluoroalkyl surfactants that form vesicles possess chain lengths as short as C10

Additionally crown ether amphiphiles bearing a steroidal C14 alkyl or C16 alkyl hydrophobic unit have been shown to form vesicles.

The water soluble detergent polysorbate 20 also forms niosomes in the presence of cholesterol

two portions of the molecule are linked by ether, ester & amide linkages.

.STEROIDS – Cholesterol

Improves the fluidity of the bilayer. Minimizes leaching out of water soluble drug. Systems resulting in less leaky vesicles. Improves stability in biological fluids – reduce interaction with plasma proteins

CHARGE INDUCERS – Dicetyl Phosphate, Sod. Cholate, Stearylamine

Prevents aggregation Increases drug loading of water soluble drugs in MLV

FACTORS GOVERNING THE SELF ASSEMBLY OF NIOSOMES Non ionic surfactant structure

Membrane additives

Nature of the encapsulated material/drug

Surfactant & lipid levels

Temperature of hydration

FACTORS INFLUENCING THE NIOSOMAL PHYSICAL CHEMISTRY

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.

 

Method of preparation

A. Ether injection method surfactant : cholesterol(150µmol) ether(20ml) 14 gauge needle (.25ml/min)

aqueous phase (4ml at 60 0 c) Mechanism of action: Slow vapourization of solvent resulting into a ether gradient extending across the interfacial

lipid/surfactant monolayer at ether water interface results in the formation of bilayer sheet which eventually folds on itself to form sealed vesicles.

B. HAND SHAKING METHOD (THIN FILM TECNIQUE)

Surfactant : cholesterol(150µmol) diethyl ether(10ml) evaporated in rotary

evaporater

Surfactant swellsFolds to form vesicles

hydration

LUV

C. SONICATION surfactant : cholesterol (150µmol)

Aqueous phase in vial (2ml)

Probe sonication(3min at 60 0 c)

MLVUltrasonic vibration ULV

D. REVERSE PHASE EVAPORATION

Probe sonicator used when sample size is small volume Bath sonicator used for larger volumes

surfactant Chloroform& phosphate buffer W/O emulsion Sonication & evaporation

vesicles hydration

E . MICROFLUIDIZATION

This method 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 impingement of thin liquid sheet along a common front is arranged such that the energy supplied to the system remains within the area of niosomes formation.

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

niosomes formed

METHODS USED FOR NIOSOME PREPARATION IN INDUSTRIAL SCALE ARE

NovasomeHandjani – Vila et al. - for larger qty i.e. Kg of dispersions

F. Multiple membrane extrusion method

Surfactant, cholesterol, diacetyl phosphate in chloroform

Thin films by evaporation

Hydrated with aqc drug soln

Suspension extruded through polycarbonate membranes

Upto 8 passages forms vesicles

G. Trans membrane pH gradient (inside acidic) Drug Uptake Process (Remote Loading)

Surfactant, cholesterol in chloroform

evaporation Hydration with 300mM citric acid MLV

Frozen,thawed& sonicated(Niosomal suspension)

Acq drug soln(10mg/ml)

P H 7 -7.2 with 1M disodium phosphate

Heating at 60 0 c forms niosomes

Niosomes (of controlled size)

H. BUBBLE METHODThis method does uses organic solvents - adv

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

Surfactant, cholesterol Dissolved in buffer at p H 7.4 at 70 0 c

HomogenizationFor 15 min

Bubbled at 70 0 c using N 2 gas

niosomes

I. MICELLAR SOLUTION METHODS

Mixed micellar solutionEsterases ,non ionic surfactant , NIOSOMES

Charged inducer Esterases enzymes cleavage the micellar solution

SIZE REDUCTION METHODS

Probe sonication 100 -140nm

Extrusion method in the range of 140nm

Sonication & filtration in the range of 200nm

Microfluidizer <50nm

High pressure homogenization <100nm

DRUG LOADING

Active loading / Remote loading

Passive loading

ENCAPSULATION OF DRUGS IN NIOSOMES

Encapsulation volume/Trapped volume

Volume of aqueous solution entrapped in niosomes per mole of surfactant (µL/µmol surfactant)

Encapsulation Efficiency

It is determined after separation of unentrapped drug, on complete vesicle disruption by using about 1 ml of 2.5% sodium lauryl sulphate, briefly homogenized and centrifuged and supernatant assayed for drug after suitable dilution.

% Encapsulation

Drug entrapped in niosomes x 100 Total drug added

The effect of the choice of niosome forming surfactant on the properties of the niosome dispersion

The effect of the nature of the encapsulated drug on the properties of the niosome dispersion.

Method of preparation Drug incorporated

Ether Injection Sodium stibogluconate Doxorubicin 

Hand Shaking Methotrexate Doxorubicin 

Sonication

Reverse phase evaporation

9-desglycinamide8-arginineVasopressinOestradiol

Diclofenac sodium

DRUGS INCORPORATED INTO NIOSOMES BY VARIOUS METHODS

. Characterization of niosomesa) Entrapment efficiency The drug remained entrapped in niosomes is determined by complete vesicle disruption using 50% n-

propanol or 0.1% Triton X-100 and analyzing 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 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

dialysis tubingA 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

Factors affecting vesicles size, entrapment efficiency and release characteristics

a)   Drug entrapment of drugs in niosomes increase the vesicle size by- 1.interaction of solute with surfactant head groups 2.increasing the charge 3.mutual repulsions of the surfactant bilayers

In PEG coated vesicles, some of the drug entrapped in long PEG chains there by reducing the charge

b)   Amount and type of surfactant

Hydrophilic Lipophilic Balance (HLB) is a good indicator of the vesicle forming ability of any surfactant.With the sorbitan monostearate (Span) surfactants, a HLB number of between 4 and 8 was found to be compatible with vesicle formationBilayers of vesicles are in gel or liquid state depending on-

1. Temp 2. Type of liquid or surfactant 3. Cholesterol

Surfactants or lipids are characterized by gel - liquid phase transition temp (TC)TC of surfactant also effect entrapment efficiency i.e., span 60 has higher TC so better entrapment

c) cholesterol content & charge

Cholesterol increase the hydrodynamic diameter & entrapment efficiency

Action is two ways –

1. Increase the chain order of liquid state bilayers2. Decrease the chain order of gel state bilayers

at high cholesterol conc - gel state less ordered liquid crystalline phase

Increase in cholesterol content-

Increase the rigidity of bilayersDecrease the release rate of encapsulated material

charge - induced by stearylamine & Diacetyl phosphate

Increase the interlamellar distance b/w the successive bilayers in multilamellar vesicles

Overall greater entrapped volume

d)   Methods of preparation

Hand shaking method forms vesicles with greater diameter (0.35-13nm) compared to the ether injection method (50-1000nm)

Small sized niosomes can be produced by Reverse Phase Evaporation (REV) method 

Micro fluidization  method gives greater uniformity and small size vesicles.

Niosomes also prepared by trans membrane pH gradient (inside acidic) drug uptake process , showed greater entrapment efficiency and better retention of drug

e)    Resistance to osmotic stress

Addition of a hypertonic salt solution 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

Mean Size & Size distribution - Electron Microscopy Dynamic Light Scattering (PCS) molecular sieve chromatography

Surface Potential & Surface pH - Micro electrophoresis

No of lamellae - Small angle X ray Scattering, NMR, Electron microscopy

Structural & Motional behavior of lipids - DSC, ESR, NMR

Surface Chemical Analysis - NMR Bilayer formation - X cross formation under light polarization microscopy

Membrane rigidity - mobility of fluorescence probe as a function of temp

STABILITY OF NIOSOMES

Stability in buffer

Stability in hypertonic media

Stability in hypotonic media

Stability in – vivo

Stability is also influenced by –

Surfactant/lipid ratio Encapsulated drug Temperature of storage Detergents

Applications

1) Targeting of bioactive agents

a) To reticulo - endothelial system (RES) b) To organs other than RES

2) Neoplasia

Doxorubicin dose dependant irreversible cardio toxic effect.

Niosomal delivery of this drug to mice bearing S-180 tumor increased their life span and decreased the rate of proliferation of sarcoma.

Niosomal entrapment increased the half-life of the drug, prolonged its circulation and altered its metabolism.

Intravenous administration of methotrexate entrapped in niosomes to S-180 tumor bearing mice resulted in total regression of tumor and also higher plasma level and slower elimination.

3) Leishmaniasis sodium stibogluconate

4) Niosomes in Oral & Opthalmic drug delivery Oral - Ergot alkaloids Opthalmic - Cyclopentolate (polysorbate – 20 & cholesterol)

5) Diagnostic imaging with niosomes Iopromide

6) Anti infective agents Rifampicin

7) Anti cancer therapy methotrexate

8) Niosomes as Vaccine Adjuvants

9) Delivery of peptide drugs 9-desglycinamide, 8-arginine, vasopressin

10) Immunological application

11) Carriers for haemoglobin 12) Transdermal delivery of drugs Oestradiol

13) Other applecations a) Sustained release b) Localized drug action c) Cosmetics 14) Niosomes also used as drug carrier

Ciprofloxacin & Norfloxacin Doxorubicin Indomethacin Pentoxyphillin Diclofenac Sodium 9 – desglycinamide 8 – Arginine Vasopressin Propylthiouracil

Suitable niosome sizes for particular routes of administration

RECENT ADVANCES IN NIOSOMES

 Combination of PEG and glucose conjugates on the surface of niosomes significantly improved tumor targeting of an encapsulated paramagnetic agent assessed with MR imaging in a human carcinoma xenograft model.

Phase I and phase II studies were conducted for Niosomal methotrexate gel in the treatment of localized psoriasis. These studies suggest that niosomal methotrexate gel is more efficacious than placebo and marketed methotrexate gel.

A research article was published that Acyclovir entrapped niosomes were prepared by Hand shaking and Ether injection methods increases the oral bioavailability

Lancome has come out with a variety of anti-ageing products which are based on niosome formulations

Conclusion The concept of incorporating the drug into liposomes or niosomes for a better targeting of the drug at

appropriate tissue destination is widely accepted by researchers and academicians.

Niosomes represent a promising drug delivery module. They presents a structure similar to liposome and hence they can represent alternative vesicular systems

with respect to liposomes, due to the niosome ability to encapsulate different type of drugs within their multi environmental structure.

Niosomes are thoughts to be better candidates drug delivery as compared to liposomes due to various factors like cost, stability etc

. Various type of drug deliveries can be possible using niosomes like targeting, ophthalmic, topical,

parenteral, etc.

 Niosomes can also serve better aid in diagnostic imaging and vaccine adjuvant in pharmaceutical industry.

Niosomes are considered as promising controlled drug delivery carrier which increase the half life of

drugs and helps in formulating prolonged/controlled acting dosage forms

Niosomes have great drug delivery potential for targeted delivery of anti-cancer, anti infective agents.

REFERENCES

1) S.P.Vyas, R.K.Khar., Targetted and controlled drug delivery. 2) N.K.Jain., Advances in controlled and novel drug delivery. 3)James Swarbrick, Encyclopedia of pharmaceutical technology, third edition ,

vol-24) en.wikipedia.org5) Informa Healthcare – Journal of Liposome Research6) AAPS PharmaSciTec.com7) Pharmainfo.net8) I. F. Uchegbu, S.P. Vyas : International Journal of Pharmaceutics 172 (1998)

33–709)Journal of Pharmacy Research Vol.1.Issue 2. Oct-December 2008

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