1. Niosomes are non-ionic surfactant-based vesicles that are structurally similar to liposomes but more stable due to their composition. 2. They are formed from non-ionic surfactants and cholesterol that orient themselves into bilayer structures with the hydrophilic ends pointing outwards and the hydrophobic ends facing each other. 3. Niosomes can entrap both hydrophilic drugs within the aqueous compartment and lipophilic drugs within the bilayer membranes, providing a means of controlled drug delivery.

1. A Niosome is a non-ionic surfactant-based Vesicle (biology and chemistry). Niosomes are formed
mostly by non-ionic surfactant and cholesterol incorporation as an excipient. Other excipients can
also be used. Niosomes have more penetrating capability than the previous preparations
of emulsions. They are structurally similar to liposomes in having a bilayer; however, the materials
used to prepare Niosomes make them more stable.
Niosomes are lamellar structures that are microscopic in size. They constitute of non-
ionic surfactant of the alkyl or dialkyl polyglycerol ether class and cholesterol with subsequent
hydration in aqueous media. The surfactant molecules tend to orient themselves in such a way that
the hydrophilic ends of the non-ionic surfactant point outwards, while the hydrophobic ends face
each other to form the bilayer. The figure in this article on Niosomes gives a better idea of the
lamellar orientation of the surfactant molecules.
1. Niosomes are osmotically active, chemically stable and have long storage time compared to
liposomes
2. Their surface formation and modification is very easy because of the functional groups on
their hydrophilic heads
3. They have high compatibility with biological systems and low toxicity because of their non-
ionic nature
4. They are biodegradable and non-immunogenic
5. They can entrap lipophilic drugs into vesicular bilayer membranes and hydrophilic drugs in
aqueous compartments
6. They can improve the therapeutic performance of the drug molecules by protecting the drug
from biological environment, resulting in better availability and controlled drug delivery by
restricting the drug effects to target cells in targeted carriers and delaying clearance from the
circulation in sustained drug delivery
7. Access to raw materials is convenient
 Ether injection method (EIM)
 Hand shaking method (HSM)
 Reverse phase evaporation method
(REV)
 Micro fluidization method
Methods of preparation in detail: Based on the vesicle size, can be divided into three groups.
Small unilamellar vesicles (SUV, size=0.025-0.05 μm),
Multilamellar vesicles (MLV, size=>0.05 μm), and
Large unilamellar vesicles (LUV, size=>0.10 μm).
Advantages
Structure
Method of preparation
NIOSOMES

2. Methods of Preparation: Niosomes are prepared by different methods based on the
I. Sizes of the vesicles and their
distribution,
II. Number of double layers,
III. Entrapment efficiency of the aqueous
phase
IV. Permeability of vesicle membrane
.
Preparation of small unilamellar vesicles
Sonication The aqueous phase containing drug is added to the mixture of surfactant and
cholesterol in a scintillation vial. The mixture is homogenized using a sonic probe at 60 °C for 3
minutes. The vesicles are small and uniform in size.
Micro fluidization Two fluidized streams move forward through precisely defined micro
channel and interact at ultra-high velocities within the interaction chamber. Here, a common gateway
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.
Preparation of multilamellar vesicles
Hand shaking method (Thin film hydration technique) In the hand shaking method,
surfactant and cholesterol are dissolved in a volatile organic solvent such as diethyl ether,
chloroform or methanol in a rotary evaporator, leaving a thin layer of solid mixture deposited on the
wall of the flask. The film is hydrated with 300 mM citric acid (pH 4.0) by vortex mixing. The
multilamellar vesicles are frozen and thawed three times and later sonicated. To this niosomal
suspension, aqueous solution containing 10 mg/ml of drug is added and vortexed. The pH of the
sample is then raised to 7.0-7.2 with 1M disodium phosphate. This mixture is later heated at 60 °C
for 10 minutes to produce the desired multilamellar vesicles.
Preparation of large unilamellar vesicles
Reverse phase evaporation technique (REV) In this method,
cholesterol and surfactant 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. The
organic phase is removed at 40 °C under low pressure. The resulting viscous niosome suspension is
diluted with phosphate-buffered saline and heated in a water bath at 60 °C for 10 min to yield
niosomes.
Ether injection method The ether injection method is essentially based on slow
injection of niosomal ingredients in ether through a 14-gauge needle at the rate of approximately
0.25 ml/min into a preheated aqueous phase maintained at 60 °C. The probable reason behind the
formation of larger unilamellar vesicles is that the slow vapourisation of solvent results in an ether
gradient extending towards the interface of aqueous-nonaqueous interface. The former may be
responsible for the formation of the bilayer structure. The disadvantages of this method are that a
small amount of ether is frequently present in the vesicles suspension and is difficult to remove.
Emulsion method The oil in water (o/w) emulsion is prepared from an organic solution
of surfactant, cholesterol, and an aqueous solution of the drug. The organic solvent is then
evaporated, leaving niosomes dispersed in the aqueous phase.

3. Lipid injection method This method does not require expensive organic phase. Here,
the mixture of lipids and surfactant is first melted and then injected into a highly agitated heated
aqueous phase containing dissolved drug. Here, the drug can be dissolved in molten lipid and the
mixture will be injected into agitated, heated aqueous phase containing surfactant.
Niosomes are a novel drug delivery system that is finding application in:
1. gene delivery
2. drug targeting
3. antineoplastic treatment
4. leishmaniasis treatment
5. delivery of peptide drugs
6. studying immune response
7. carriers for haemoglobin
8. transdermal drug delivery systems
9. cosmetics
Applications