liposomes

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LIPOSOMES

• By
• SHIVA
• Shiva.pharmacist_at_gmail.com

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LIPOSOMES

• Liposome are membranous vesicles formed by
  dispersion of phospholipids in aqueous media.
  They are small hollow spheres bound by a double
  layer of lipid molecules in which the hydrophilic
  heads of the molecules form the inner and outer
  surface of the sphere, while the lipophillic
  tails interwine in the middle.

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LIPOSOME
HYDROPHOBIC
HYDROPHILIC
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• ADVANTAGES
• Flexibility in the structure in entrapment of
  water soluble as well as insoluble drugs.
• Biodegradability
• Efficient control of release.
• Resemblance to natural membrane structures.
• Increased targeting prospects.
• Beneficial modification of pharmacokinetics of
  the drug.
• Facilitation of transport across membranes.
• Adjuanticity of vaccines

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• DISADVANTAGES
• The development of liposomes at industrial level
  is difficult due to its physiological and
  physicochemical instability.
• They aggregate and fuse together upon prolonged
  storage disturbing the reproducibility.
• They are prone to degradation by oxidation and
  hydrolysis.

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CHARACTERISATION

• Size and size distribution
• Lamellarity
• Entrapped volume
• Solute distribution

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Classification based on structural parameters






MVV Multivesicularvesicles (gt 1.0 UM)
MLV Multilamellar Large vesicles (gt0.5 um)
OLV oligolamellar vesicles (gt0.1-1.0 um)
UV UnilamellarVesicles (all size ranges)
Based on structural 
SUV 20-100nm
MUV
LUV gt100nm
GUV gt1um
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Multilamellar vesicles
Unilamellar vesicles
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MECHANISM OF ACTION

• Endocytosis
• Adsorption to cell surface
• Fusion with plasma cell membrane
• Transfer of liposomal content

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METHODS OF PREPARATION

• Physical dispersion methods
• Solvent dispersion
• Detergent solubilisation

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Physical dispersion methods

• Hand shaking method
• Non shaking method
• Pro liposomes
• Freeze drying method

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HAND SHAKING METHOD

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• SOLVENT DISPERSION METHODS
• Ethanol injection
• Ether injection
• Water in organic phase
• Double emulsion vesicles

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Ethanol/Ether injection method
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• Handling of liposomes
• Liposomes have a standard composition- egg,
  lecithin, cholesterol, phosphotidyl glycerol in
  molar ratio of 0.910.1. these lipids are stored
  as solids or in organic solution at -20C or
  -70C in order to reduce oxidation. The solvent
  is mixture of chloroform and methanol(21).
  Stored in dark glass vessels.
• Drying Gentle warming at 20C to 40C under
  reduced pressure. Rapid rotation increase surface
  area for evaporation.

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PURIFICATION OF LIPOSOMES

• Commonly purified by gel filtration column
  chromatography or dialysis or centrifugation.
• In column chromatographic separation, Sephadex
  G-50 is most widely used material.
• In dialysis method, hollow fiber dialysis
  cartridge may be used.
• The separation of liposomes by centrifugation
  method depends on the size as well as the
  composition of the bilayers.

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INVITRO BEHAVIOUR OF LIPOSOMES

• IV route is the most popular route. Three
  pathways are there for drug release.
• Destabilization of liposomes
• Delivery of liposomes to the monounuclear
  phagocyte system(MPS)
• Sustained release of liposome encapsulated drug
  by long circulating liposomes.

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APPLICATIONS

• Enzyme replacement therapy
• Delivery of antibodies, antigens and vaccines
• Hormones and blood factors
• Blood substitutes
• Interferon

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Thank you