Niosomes

NIOSOMES

VIJAYENDHAR REDDY M-PHARM 2 SEM

CONTENTS

• INTRODUCTION• CLASSIFICATION• CHARACTERIZATION OF NIOSOMES• NIOSOMES PREPARATION• ENCAPLUSLATION OF DRUG IN

NIOSOMES• APPLICATIONS

Niosomes are non-ionic surfactant based vesicles are formed from the self-assembly of non-ionicamphiphiles in aqueous media resulting in closedbilayer structures (Vanlerberghe et al., 1972; Handjani-Vila et al., 1979).

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

Advantages

• Encapsulate hydrophilic and hydrophobic drugs• Low cost• Greater stability• Ease of storage of nonionic surfactants

Factors affecting Niosome physical chemistry

Non-ionic surfactant structure

Hydrophilic head groups found in vesicle forming surfactants

• glycerol head groups• ethylene 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.

• 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 formation.

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

Classification of Vesicles

SmallUnilamellarVesicle(SUV)

LargeUnilamellarVesicle(LUV)

MultilamellarVesicle(MLV)

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

NIOSOME PREPARATION

Ether Injection

Injection of an organic solution of surfactants:lipids in an aqueous solution of the drug to be encapsulated which is heated above the boiling point of the organic solvent. Injection is given through a 14 gauge needle at a rate of 0.25ml/min

Reverse Phase Evaporation

The formation of an oil in water (o/w) emulsion from an organic solution of surfactants:lipids and an aqueous solution of the drug. The organic solvent is then evaporated to leave niosomes dispersed in the aqueous phase. In some cases, a gel results which must be further hydrated to yield niosomes.

Hand shaking method

Surfactant and cholestrol mixture is dissolved in 10 ml of diethylether in a round bottom flask. The ether is evapourated under vaccum at room temperature in a rotary evapourater.

So the surfactent swells then the amphiphiles eventually fold to form vesicles.

The liquid volume entrapped in vesicles appears to be small i.e 5-10% .

But the entrapped volume seems to be unsuitable for water soluble solutes.

REDUCTION OF NIOSOME SIZE

• Probe sonication which yields niosomes in the 100–140 nm size range.

• Extrusion through 100 nm Nucleopore filters size range.

• In some instances the combination of sonication and filtration (220 nm Millipore® filter) has been used to achieve niosomes in the 200 nm size range

• The achievement of sub-50 nm sizes is possible by the use of a microfluidizer.

• High-pressure homogenisation also yields vesicles of below 100 nm in diameter although drug loading is ultimately sacrificed to achieve this small size.

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

Encapsulated drug to surfactant (µmol/µmol of surfactant)

% Encapsulation

Drug entrapped in niosomes x 100 Total drug added

Seperation of Unencapsulated drug

REMOVAL OF UNENCAPSULATED DRUG

Centrifree - Suitable dilution is necessary

- Higher concentration of lipid blocks membrane Adv : Rapid, requires small sample volumeDisadv : Expensive, Lipid concentration cannot exceed 5mg/mL

Gel Chromtography- Sepharose/Sephadex- Liposomes larger size pass through void volume

Adv : Sample recoveryDisadv : Slow and tedious, dilution of samples

Dialysis- Controlled and minimized by avoiding large dilution steps- Several steps of small dil. vol (5-10 fold original dispersion)

Adv : Sample recoveryDisadv : Inaccurate and impossible to determine critical point

Protamine Aggregation

Adv : EconomicalDisadv : Slow with neutral/positive charged liposomes

Contamination of the sample

Ultracentrifugation

- Subjected to high forces, can modify physically

CHARACTERIZATION OF NIOSOMES

Mean Size & Size distribution - Electron MicroscopyDynamic Light Scattering (PCS)

Surface Potential & Surface pH - Microelectrophoresis

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

Structural & Motional behaviorof lipids - NMR

Surface Chemical Analysis - NMR

APPLICATIONSCancerAntimicrobial agents – Leishmaniasis (Amphotericin B)Gene therapyImmunological AdjuvantsLiposome entrapped DNA deliveryTransdermal drug deliveryVaccine adjuvantsEnzyme replacementCosmeticsTopical applicationsPulmonary deliveryLysosomal storage diseasesOphthalmic delivery of drugs

MICROSPHERES

CONTENTS• INTRODUCTION • USES • POLYMERS USED IN MICROSPHERE • METHOD OF PREPARATION OF MICROSPHERES

• APPLICATIONS

INTRODUCTION

Microspheres are the spherical particles of size varying from 50 nm to 2 nm, containing a core substance.

Some related terms like micro capsules, micro spheres, micro beads

and beads are used as synonymously. These are characteristically free flowing powders consisting of

proteins or synthetic polymers , which are biodegradable in nature, and ideally having a particle size less than 200 micro meter.

Microcapsule Micromatrix

Types of Microspheres

Spherical particle with size varying from 50 nm to 2 mm.

Potential use of microspheres in the pharmaceutical industry

• Taste and odor masking

• Conversion of oils and other liquids to solids for ease of handling

• Protection of drugs against the environment (moisture, light etc.)

• Separation of incompatible materials (other drugs or excipients)

• Improvement of flow of powders

• Aid in dispersion of water-insoluble substances in aqueous media, and

• Production of SR, CR, and targeted medications

PHARMACEUTICAL APPLICATIONS

Microencapsulated products currently on the market, such as aspirin,theophylline & its derivatives, vitamins, pancrelipase, antihypertensives, potassium chloride, progesterone, and contraceptive hormone combinations.

Microencapsulated KCl is used to prevent gastrointestinal complications associated with potassium chloride.

Microspheres have also found potential applications as injection, or inhalation products.

Most encapsulation processes are expensive and require significant capital investment for equipment.

An additional expense is due to the fact that most microencapsulationprocesses are patent protected.

OTHER APPLICATIONS

Microcapsules are also extensively used as diagnostics, for example, temperature-sensitive microcapsules for thermographic detection of tumors.

In the biotechnology industry microencapsulated microbial cells are being used for the production of recombinant proteins and peptides.

Encapsulation of microbial cells can also increase the cell-loading capacity and the rate of production in bioreactors.

A feline breast tumor line, which was difficult to grow in conventionalculture, has been successfully grown in microcapsules.

Microencapsulated activated charcoal has been used for hemoperfusion.

Paramedical uses of microcapsules include bandages with microencapsulated anti-infective substances.

Synthetic Polymers

Non-biodegradableAcroleinEpoxy polymers

BiodegradableLactides and Glycolides copolymersPolyalkyl cyanoacrylatesPolyanhydrides

Natural MaterialsProteins

AlbuminsGelatinCollagen

CarbohydratesStarch agaroseCarrageenanChitosan

Chemically modified carbohydratesPoly(acryl)dextranPoly(acryl)starch

Polymers used in the Microsphere preparation

• Longer duration of action• Control of content release• Increase of therapeutic efficacy• Protection of drug• Reduction of toxicity• Biocompatibility• Sterilizability• Relative stability• Water solubility or dispersibility• Bioresorbability• Targetability• Polyvalent

Ideal properties of Microparticulate Carriers

GENERAL METHODS OF PREPARATION

• Single Emulsion techniques• Double emulsion techniques• Polymerization techniques

- Normal polymerization- Interfacial polymerization

• Coacervation phase separation techniques• Spray drying and spray congealing• Solvent extraction

SIMPLE EMULSION BASED METHOD

Aq.Solution/suspension of polymer

Dispersion in organic phase (Oil/Chloroform)

Microspheres in organic phase Microspheres in organic phase

MICROSPHERES

Stirring, Sonication

CROSS LINKINGChemical cross linking (Glutaraldehyde/Formaldehyde/ButanolHeat denaturation

Centrifugation, Washing, Separation

DOUBLE EMULSION BASED METHODAq.Solution of protein/polymer

First emulsion (W/O)

MICROSPHERES

Dispersion in oil/organic phaseHomogenization

Separation, Washing, Drying

Addition of aq. Solution of PVA

Addition to large aq. PhaseDenaturation/hardening

Multiple emulsion

Microspheres in solution

First, the polymer is dissolved in acetone, then a phospholipid mixture (e.g., Epikuron'") and benzyl benzoate are added to this solution.

The resulting organic solution is poured into an aqueous phase containing a surfactant (e.g., poloxamer 188) under moderate stirring.

Acetone diffuses immediately into the aqueous phase, inducing the deposition and the precipitation of the polymer around the oily droplets.

Drugs intended to be encapsulated by this method must have a high solubility in the organic-oily phase, otherwise they diffuse from the oily

solution and precipitate in the aqueous medium during particle formation.

Once the microcapsules are formed, acetone is eliminated under reduced pressure.

Interfacial Deposition technique

When two reactive monomers are dissolved in immiscible solvents, the monomers diffuse to the oil-water interface where they react to form a polymeric membrane.

Drug is incorporated either by being dissolved in the polymerization medium or by adsorption onto the nanoparticles after polymerization completed.

The nanoparticle suspension is then purified to remove various stabilizers and surfactants employed for polymerization by ultracentrifugation and re-suspending the particles in an isotonic surfactant-free medium.

This technique has been reported for making polybutylcyanoacrylate or poly (alkylcyanoacrylate) nanoparticles.

Interfacial Polymerization technique

PHASE SEPARATION METHOD

Aqueous/Organic.Solution of polymer

Drug dispersed or dissolved in polymer solution

MICROSPHERES

Drug

Separation, Washing, Drying

Phase seperation induced by various means

Hardening

Polymer rich globules

Microspheres in aq./organic phase

Gelatin and albumin nanospheres can be produced by the slow addition of a desolvating agent (neutral salt or alcohol) to the protein solution.

Upon this addition, a progressive modification of the protein tertiarystructure is induced leading (when a certain degree of desolvation is obtained), to the formation of protein aggregates.

To obtain small and monodispersed particles, it is important to maintain the system at a point just before coacervation is initiated.

The addition of the desolvating agent is monitored by turbidimetry measurements of the system and must be stopped as soon as the turbidity

increases, otherwise aggregates that are too large will be formed.

Nanospheres are obtained by subsequent crosslinking of these aggregates with glutaraldehyde.

Preparation of Microspheres by desolvation of albumin

An aqueous phase saturated with electrolytes (e.g., magnesium acetate, magnesium chloride) and containing PVA as a stabilizing and viscosity increasing agent is added under vigorous stirring to an acetone solution of polymer.

In this system, the miscibility of both phases is prevented by the saturation of the aqueous phase with electrolytes, according to a salting-out phenomenon.

The addition of the aqueous phase is continued until a phase inversion occurs and an o/w emulsion is formed.

Then, a sufficient amount of pure water is added to disrupt the equilibrium between the two phases and to allow complete diffusion of acetone into water, leading to polymer precipitation in the form of spherical nanospheres

Salting-out process

Emulsification-Solvent evaporation method

Once a high degree of dispersion is achieved, the emulsion is added dropwise.

Immediate vaporization of the water contained in the droplets and to the irreversible denaturation of the albumin which coagulates in the form of solid nanospheres.

The suspension is then allowed to cool down at room temperature or in an ice bath. Subsequently, the particles are submitted to several washings using large amounts of

organic solvent (e.g., ether, ethanol, acetone) for complete removal of the oil.

Preparation of Microspheres by thermal denaturation of albumin

Applications• Vaccine delivery – Improved antigenecity, Ag release,

Stabilization of Ag• Drug targeting

– Ocular: gelation with increased residence time– Intranasal: protein and peptide delivery– Oral

• Magnetic microspheres• Immunomicrospheres• Chemoembolization• Imaging• Microsponges• Surface modified microspheres