(Targeted drug delivery systems)


       Medication is  encapsulated in a  vesicle

       Composed of a bilayer  of non-ionic surface  active agents

       They are vesicles composed of non-ionic surfactants

       Biodegradable, relatively nontoxic, more stable and  inexpensive

       Used as an alternative to liposomes

Advantages of niosomes

       These are very small in size -nanometric scale

       Structurally similar to liposomes, but offer several advantages over them

       Niosomes greatly increase transdermal drug delivery and  also in targeted drug delivery

       Hydrophilic, lipophilic and amphiphilic drugs can be accommodated in the vesicular moieties

       Act as a depot to release the drug slowly and offer a controlled release

       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

Ø  Niosomes are microscopic  lamellar structures

Ø  Formed on the admixture of  non-ionic surfactant of the alkyl or dialkyl polyglycerol 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 are exposed on the outside and inside  of the vesicle, while the hydrophobic chains face each  other within the bilayer

Methods of preparation

  1. Ether injection method
  2. Film hydration method
  3. Reverse phase evaporation
  4. The “Bubble” method
  5. Micro fluidization
  6. Sonication

1. Ether injection method

       In this method a solution of niosomal ingredients in ether is  slowly injected into an aqueous medium at high  temperature

       A mixture of surfactant and cholesterol (150 μmol) is  dissolved in ether (20 ml)

       Injected into an aqueous phase (4 ml) using a 14- gauge  needle syringe at the rate of approximately 0.25ml/min

       The aqueous phase is preheated to 600C during the injection  of the ether solution

       This causes evaporation of ether leading to the formation of  single layered vesicles

       The particle size of niosomes formed can range b/w 50μm  and 1000μm


      Niosomes prepared by ether injection method have better  entrapment efficiency than those prepared by the film or  sonication


      Small amount of residual ether  frequently remains in the  final product and is difficult to remove

2. Film hydration method

          Vesicle-forming agents such as the surfactant and cholesterol are dissolved in a volatile organic solvent such  as diethyl ether, chloroform, or methanol in a round bottom  flask

          The organic solvent is evaporated under reduced pressure  using a rotary evaporator

          A thin film of solid mixture remains deposited on the walls of the flask

          The dried surfactant layer is rehydrated with the aqueous  phase at normal temperature with gentle agitation to yield  unilamellar niosomes or smaller niosomes using sonication,  technique

3. Reverse phase evaporation technique

          In this method, cholesterol and surfactant (1:1 ratio) are  dissolved in a mixture of ether and chloroform

          An aqueous phase containing the drug to be loaded is added to this

          Mixture is sonicated at 40C- 50C until a clear gel is formed

          Phosphate buffered saline (PBS) is added to it Sonicated

          The temperature is raised to 400C and the organic phase is  removed under reduced pressure

          A viscous niosome suspension is obtained

          Diluted with PBS and heated on a water bath at 600C for  10min to yield niosomes

4. The Bubble method

          This method allows the preparation of niosomes without the use of organic solvent

          The niosomes are prepared in a bubbling unit, which consists of a round bottom flask with three necks

          The flask is positioned in a water temperature

          In the first neck water – cooled reflux is positioned

          In the second neck thermometer is fixed

          The third neck is used to bubble nitrogen gas into the mixture

          A dispersion of cholesterol and surfactant in a buffer (pH 7.4) is  taken in the flask and maintained at 700C

          The dispersion is then mixed with shear homogenizer

          Nitrogen gas is immediately bubbled into it at 700C to yield  niosomes

5. Sonication

          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

6. 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 mm screen

          It is then forced along defined micro channels, which direct  two streams of fluid to collide together at right angles,  there by affecting a very efficient transfer of energy

          The lipids/surfactants can be introduced  fluidizer

          The fluid collected can be recycled until vesicles are obtained

Separation of free/unentrapped drug


The aqueous niosomal dispersion is dialyzed in a dialysis tubing against phosphate buffer or normal saline or glucose solution.

Gel Filtration

The unentrapped drug is removed by gel filtration of niosomal dispersion through a Sephadex-G-50 column and elution with phosphate buffered saline or normal saline.


The niosomal suspension is centrifuged and the supernatant is separated. The pellet is washed and then resuspended to obtain a niosomal suspension free from unentrapped drug

Evaluation of niosomes

1. Entrappment efficiency

Entrapment efficiency = Amount entrapped / Total amount added x 10

2. Vesicle Size

Laser Light Scattering method

3. Particle size analysis

Scanning Electron Microscopy (SEM)

4. Bilayer formation

Polarised Light Microscope

5. Number of lamellae

Nuclear Magnetic Resonance (NMR) spectroscopy

6.In vitro Release Study

7. In vivo Release Study

Scanning Electron Microscopy

Polarised Light Microscope


          Anti-neoplastic treatment

          Treatment of Leishmaniasis

          Delivery of peptide drugs

          Used in studying immune response

          Niosomes as carriers for haemoglobin

          Transdermal drug delivery systems


  1. Niosomes are vesicular systems in which the medication is encapsulated in a vesicle composed of a bilayer of non-ionic  surface active agents

2.       The methods of preparation include Ether injection method, Film hydration method, Reverse phase evaporation, The  “Bubble” method, Micro fluidization, Sonication

3.       Niosomes can be characterized for Entrapment efficiency, Vesicle Size, Particle size, Bilayer formation, Number of  lamellae, In vitro and In vivo release study

  Detailed Image Based Notes Click on Download Button

Post a Comment