Transcript Document

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 doublechain phospholipids
Method of preparation
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 .
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
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)
Pharmaceutical applications
 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
niosomes can forms from proniosomes by coating a watersoluble 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.
The difference between Liposomes &
Transfersomes
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
application site
in
peripheral
tissues
below
the
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.