They represents a structure similar to liposome

and hence they can represent alternative vesicular

systems with respect to liposomes.

a) Niosomes are used as an alternative to

liposomes,

which exhibit certain disadvantages such as :

They are expensive

Their ingredients like phospholipids are

chemically unstable because of their

predisposition to oxidative degradation

They require special storage and handling

Purity of natural phospholipids is variable.

b) Differences in characteristics exist between

liposomes and niosomes, especially since niosomes

are prepared from uncharged single-chain

surfactant and cholesterol whereas liposomes are

prepared from neutral or charged double-chain

phospholipids

Method of preparation

A. Ether injection method a Mixture of Span 60 , cholesterol and dicetyl

phosphate slowly dissolved in diethyl ether then

injected slowly through a needle in to warm

aqueous phase maintained at 60 °C that

consisting of drug.

Vaporization of ether leads to formation of

unillamellar niosomes

In niosomes, the vesicles forming lipid is a non-ionic

surfactant such as Span 60 which is stabilized by

addition of cholesterol and small amount of anionic

surfactant such as dicetyl phosphate.

B. Thin film hydration technique

Mixture of Span 60 , cholesterol and dicetyl

phosphate are dissolved in a volatile organic

solvent (chloroform) in a round bottom flask.

The organic solvent is removed at room

temperature (20°C) using rotary evaporator

leaving a thin layer of solid mixture deposited on

the wall of the flask.

The dried surfactant film can be rehydrated

with aqueous phase at 60°C with gentle agitation.

This process forms typical multillamellar niosomes.

C. Sonication Drug solution in phosphat buffer is added to the

Mixture of Span 60 , cholesterol and dicetyl

phosphate

The mixture is probe sonicated at 60°C for 3

minutes which lead to formation of unillaminar

niosomes

Separation of Unentrapped Drug

The removal of unentrapped solute from the vesicles

can be accomplished by :

A.Dialysis

B.Gel Filtration

C.Centrifugation.

the properties of niosomes depends on the

composition of the bilayer:

As the concentration of cholesterol increases,

entrapment efficiency decreases.

The entrapment efficiency increases with increase

in the concentration and lipophilicity of

surfactant.

• As HLB value of surfactant decreased give

highest percent entrapment, that Span 60 (HLB

= 4.7) gave highest percent entrapment than

Span 85 (HLB = 9.8)

Targeting

Sustained Release

Localized Drug Action

since their size and low penetrability through

epithelium keeps the drug localized at the site of

administration. results in enhancement of efficacy

and reduces its systemic toxic effects

Pharmaceutical Applications

niosomes can forms from proniosomes by coating a

water-soluble carrier such as sorbitol or maltodextrin

with surfactant.

Where the mixture of maltodextrin and surfactant

is dried to form a free flowing powder, in which each

water-soluble particle is covered with a thin film of

dry surfactant. This preparation is termed

“Proniosomes”.

The niosomes are produced by the rehydration of

Proniosomes by addition of warm water at T > Tc and

brief agitation.

Transfersomes are complex vesicles that have

extremely flexible & self-regulating membranes,

which makes the vesicle very deformable.

Transfersome vesicle can cross microporous

barriers efficiently, even if the porous are much

smaller than the vesicles size.

Transfersome consists of natural phospholipids

suspended in a water-buffered solution containing

drug & biocompatible surfactants (sodium cholate).

Similar to a liposome, a Transfersome has a lipid

bilayer that surrounds an aqueous core.

1. Liposomes are made of phospholipids and to

improve the stability of such vesicles, cholesterol is

included in the bilayer as membrane (stiffening

agent) which lead to more rigid, less flexible and

less permeable lipid bilayers.

2. The liposome that applied locally have crossed the

skin barrier in a low transport rate and distributed

between the cells in building blocks (ceramic

layer).

3. The liposome too large to enter the blood vessels;

locally they are utilized in peripheral tissues below

the application site

Mechanism of Transfersome

penetration: The skin is a nanoporous barrier that only permit the

passage of smaller particles.

Thus the passage of a Transfersome across the skin is

due to vesicle membrane flexibility, hydrophilicity,

and the ability to perforate the skin barrier.

Explanation of High efficiency of Transfersome

transport across the skin compared to liposomes

(rigid vesicles)

• Ultradeformable, lipid vesicle penetrating a

narrow pore, owing to the bilayer components.

•When a suspension of Transfersome

vesicles is placed on the surface of the

skin, the water evaporates from the

skin surface and the vesicles start to

dry out.

• Due to the strong hydrophilicity of Transfersome

ingredients, the vesicles are attracted to the areas

of higher water content in the narrow gaps

between adjoining cells in the skin.

•The phenomenon, together with the vesicle's

extreme ability to deform, enables Transfersomes

to change their shape, fit the channels, move

across the skin barrier and reach regions of high

water content in the deeper skin layers.

• Thus, Transfersomes bypass the cutaneous

capillary and reach the subcutaneous tissue and

the vesicle arrive into the systemic blood

circulation.