PRESENTATION FLOW Introduction Methods of Preparation Factors Affecting NiosomesPreparation Stability of Niosomes Applications of Niosomes.
Introduction NIOSOMES 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 . These are very small, and microscopic in size that lies in the nanometric scale. Although structurally similar to liposomes, they offer several advantages over them. Niosomes have recently been shown to greatly increase transdermal drug delivery and also in targeted drug delivery.
WHY ? WHY? WHY? Used for a variety of drugs : accommodate hydrophilic, lipophilic as well as amphiphilic moieties. Act as a depot to release the drug slowly and offer a controlled release . Osmotically active and stable. Increase the stability of the entrapped drug. Handling and storage of surfactants do not require any special conditions Enhance the skin penetration of drugs
Structure of Niosomes Niosomes are microscopic lamellar structures, which are formed on the admixture of non-ionic surfactant of the alkyl or dialkylpolyglycerol ether class and cholesterol with subsequent hydration in aqueous media. Niosomes may be unilamellar or multilamellar depending on the method used to prepare them. The hydrophilic ends areexposed on the outside and inside of the vesicle, while the hydrophobic chains face each other ` within the bilayer. Hence, the vesicle holds hydrophilic drugs within the space enclosed in the vesicle, while hydrophobic drugs are embedded within the bilayer itself. .
Small Unilamellar Vesicle (SUV) Large Unilamellar Vesicle (LUV) Multilamellar Vesicle (MLV) Typical Size Ranges: SLV: 20-50 nm – MLV:100-1000 nm
Niosomes Vs Liposomes 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 molecules Liposomesmade of neutral or charged double chain phospholipids. .
Similarity : Niosomes & Liposomes
Increase the bioavailability
Decrease the clearence
Used for targeted drug delivery
Properties depends on both composition of bilayer and method of preparation
Advantages : Niosomes Over Liposomes
Ester bonds of phospholipids are easily hydrolyzed, this can lead to phosphoryl migration at low PH.
Peroxidation of unsaturated phospholipids.
As liposomes have purified phospholipids they are to be stored and handled at inert(N2) atmospheres where as Niosomes are are made of non ionic surfactants and are easy to handle and store.
Phospholipid raw materials are naturally occurring substances and as such require extensive purification thus making them costly
Niosomes : Types 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. .
Formation of niosomes from proniosomes
Factors Affecting NiosomesFormation Hydration Temperature Non-ionic surfactant nature Factors affecting niosomes formation Surfactants and lipid levels Membrane additives Nature of encapsulated drug
Contd… Nature of non-ionic surfactant Type of surfactant influences encapsulation efficiency, toxicity, and stability of niosomes SURFACTANT Linked via ether , amide or ester bonds Hydrophobic tail Hydrophilic head Consist of one or two alkyl or perfluroroalkyl groups or in some cases a single steriodal group.
The alkyl group chain length is usually from C12-C18
Uchegbu et al reported that Span surfactants with HLB values between 4 and 8 were found to be compatible with vesicle formation
The water soluble detergent polysorbate 20 (HLB value 16.7) also forms niosomes with cholesterol
Polyglycerolmonoalkyl ethers and polyoxylate analogues are the most widely used single-chain surfactants
Contd… Membrane additives Cholesterol, a natural steriod, is the most commonly used membrane additive Usually incorporated in 1:1 molar ratio Prevent vesicle aggregation by the inclusion of molecules that stabilize the system against the formation of aggregates by repulsive steric or electrostatic effects Leads to the transition from the gel state to liquid phase in niosomes systems As the result, niosomes become less leaky Cholesterol Dicetyl phosphate provides negative charge to vesicles It is used to prevent aggregation of hexadecyldiglycerol ether (C16G2) niosomes Stearic acid is used in the preparation of cationic niosomes Dicetyl phosphate and Stearic acid
Contd… Surfactant and lipid levels The surfactant/lipid ratio is generally 10-30 mM (1-2.5% w/w) If the level of surfactant/lipid is too high, increasing the surfactant/lipid level increases the total amount of drug encapsulated Hydration temperature
The hydrating temperatures used to make niosomes should usually be above the gel to liquid phase transition temperature of the system
Methods Of Preparation
Ether injection method
Reverse phase evaporation
The “Bubble” method
Contd… Ether injection method
Slow injection of an ether solution of niosomal ingredients into an aqueous medium at high temperature
A mixture of surfactant and cholesterol (150 μmol) is dissolved in ether (20 ml) and injected into an aqueous phase (4 ml) using a 14- gauge needle syringe
Temperature of the system is maintained at 60oC during the process
Niosomes in the form of large unilamellar vesicles (LUV) are formed
Contd… Film method
The mixture of surfactant and cholesterol is dissolved in an organic solvent (e.g. diethyl ether, chloroform, etc.) in a round-bottomed flask
The organic solvent is removed by low pressure/vacuum at room temperature
The resultant dry surfactant film is hydrated by agitation at 50-60oC
Multilamellar vesicles (MLV) are formed
The aqueous phase is added into the mixture of surfactant and cholesterol in a scintillation vial
Homogenized using a sonic probe
The resultant vesicles are of small unilamellar (SUV) type niosomes
The SUV type niosomes are larger than SUV liposomes
It is possible to obtain SUV niosomes by sonication of MLV type vesicles
Contd… Reverse phase evaporation
Surface-active agents are dissolved in chlorofom, and 0.25 volume of phosphate saline buffer (PBS) is emulsified to get w/o emulsion
The mixture is sonicated and subsequently chloroform is evaporated under reduced pressure
The surfactant first forms a gel and then hydrates to form niosomal vesicles
The vesicles formed are unilamellar and 0.5 μ in diameter
Contd… 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 are positioned in the first and second neck and nitrogen supply through the third neck Cholesterol and surfactant are dispersed together in the buffer (pH 7.4) at 70°C, the dispersion mixed for 15 secs with high shear homogenizer and immediately afterwards “bubbled” at 70°C using nitrogen gas
Contd… Micro fluidization This is a recent technique to prepare small MLVS A microfludizer is used to pump the fluid at a very high pressure (10,000 psi) through a 5 pm screen It is then forced along defined micro channels, which direct two streams of fluid to collide together at right angles, thereby affecting a very efficient transfer of energy The lipids/surfactants can be introduced into the fluidizer The fluid collected can be recycled until spherical vesicles are obtained Uniform and small sized vesicles are obtained
Contd… Post-Preparation Processes Downsizing Separation of unentrapped material
Contd… Probe sonication Size reduction of niosomes Extrusion through filters High-pressure homogenization Combination of sonication and filtration Microfluidization
Dialysis Separation of unentrapped material from niosomes Centrifugation Gel filtration Ultracentrifugation
Charecrisation of niosoms Entrapment efficiency
Depend on the method of preparation
Niosomes prepared by ether injection method have better entrapment efficiency than those prepared by the film or sonication
Addition of cholesterol to non-ionic surfactants with single- or dialkyl-chain significantly alters the entrapment efficiency
Surfactants of glycerol type lead to reduction in entrapment capacity as the amount of cholesterol increases
Niosomes in the form of liquid crystals possess better entrapment efficiency than gel type vesicles
contd… Entrapment efficiency (EF) = (Amount entrapped total amount) x100 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.
contd… 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 methodof vesicles during the cycle.
Stability Of Niosomes Vesicles are stabilised based upon formation of following forces:
van der Waals forces among surfactant molecules
Electrostatic repulsive forces are formed among vesicles upon addition of charged surfactants to the double layer, enhancing the stability of the system
Contd… Niosomes in the form of liquid crystal and gel can remain stable at both room temperature and 4oC for 2 months Recommended temperature of storage 4oC Ideally niosomes should be stored dry for reconstitution The factors which affect the stability of niosomes:
Type of surfactant
Nature of encapsulated drug
Use of membrane spanning lipids
Inclusion of charged molecule
Applications Of Niosomes
Slow penetration of drug through skin is the major drawback of transdermal route of delivery. An increase in the penetration rate has been achieved by transdermal delivery of drug incorporated in niosomes. has studied the topical delivery of erythromycin from various formulations including niosomes or hairless mouse.
Niosomes in sub-micron size are used for parenteral administration
Niosomal vesicles upto 10 μm are administered via i.p. or i.m.
First application of niosomes as radiopharmaceuticals demonstrated by Erdogan et al. in 1996.
Delivery of peptide drugs
Oral delivery of 9-desglycinamide, 8-arginine vasopressin entrapped in niosomes increase stability of peptide significantly.
Contd… Ophthalmic Drug Delivery Saettone et al. (1996) reported on the biological evaluation of a niosomalCyclopentolate delivery system for opthalmic delivery Polysorbate 20 and cholesterol were used for niosomes formulation Optimum pH for peak permation values was pH 5.5, permeatiom decreased at pH 7.4 But in vivo data showed no such dependent on pH Niosomes> 10 μm are suitable for drug administration to eye
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 Niosomalmethotrexate gel in the treatment of localized psoriasis. These studies suggest that niosomalmethotrexate 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. 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.
References 1. Malhotra M and Jain NK. Niosomes as Drug Carriers. Indian Drugs 31 (3), 1994, 81-86. 2. Handjani-Vila RM., Ribier A, Rondot B and Vanlerberghie G. Dispersions of lamellar phases of non-ionic lipids in cosmetic products. International Journal of Cosmetic Science 1 (5), 1979, 303-314. 3. Baillie AJ, Florence AT, Hume LR, Rogerson A, and Muirhead GT ,The preparation and properties of niosomes-non-ionic surfactant vesicles. J. PharmPharmacol. 37(12), 1985, 863–868.