Download - Liposomes
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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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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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Size and size distribution
Lamellarity
Entrapped volume
Solute distribution
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Classification based on structural parameters
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Based on structural
MLVMultilamell
ar Large vesicles
(>0.5 um)
OLV oligolamellar vesicles(>0.1-1.0
um)
UV UnilamellarVesicles (all size rang
es)
MVVMultivesicularvesicles(> 1.0 UM)
MUV
GUV>1um
SUV20-
100nm
LUV>100n
m
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Multilamellar vesicles
Unilamellar vesicles
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Endocytosis
Adsorption to cell surface
Fusion with plasma cell membrane
Transfer of liposomal content
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Physical dispersion methods
Solvent dispersion
Detergent solubilisation
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Hand shaking method
Non shaking method
Pro liposomes
Freeze drying method
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• SOLVENT DISPERSION METHODS:1.Ethanol injection
2.Ether injection
3.Water in organic phase
4.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 0.9:1:0.1. these lipids are stored as solids or in organic solution at -20°C or -70°C in order to reduce oxidation. The solvent is mixture of chloroform and methanol(2:1). Stored in dark glass vessels.
• Drying : Gentle warming at 20°C to 40°C under reduced pressure. Rapid rotation increase surface area for evaporation.
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• 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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• IV route is the most popular route. Three pathways are there for drug release.
I. Destabilization of liposomesII.Delivery of liposomes to the monounuclear
phagocyte system(MPS)III.Sustained release of liposome encapsulated
drug by long circulating liposomes.
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Enzyme replacement therapy Delivery of antibodies, antigens and
vaccines Hormones and blood factors Blood substitutes Interferon
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