NIOSOMES

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NIOSOMES
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• 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.

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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
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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

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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 (20C) using rotary evaporator
  leaving a thin layer of solid mixture deposited
  on the wall of the flask.
• The dried surfactant film can be rehydratedwith
  aqueous phase at 60C with gentle agitation.
• This process forms typical multillamellar
  niosomes.

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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 60C for 3
  minutes which lead to formation of unillaminar
  niosomes

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• Separation of Unentrapped Drug
• The removal of unentrapped solute from the
  vesicles can be accomplished by
• Dialysis
• Gel Filtration
• Centrifugation.

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• 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)

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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

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PRONIOSOMES

• 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 gt Tc
  and brief agitation.

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TRANSFERSOME

• 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.

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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 in peripheral
   tissues below the application site

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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.
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• 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.

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• 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.

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• 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.