liposome by SAP

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MAEER’S,MAHARASHTRA INSTITUTE OF PHARMACY,PUNE-38. LIPOSOMES Prof. S. A. Polshettiwar M.Pharm (Quality Assurance), D.I.T., PhD.,FESO

WHAT IS LIPOSOME:

WHAT IS LIPOSOME Liposome's are simple microscopic vesicles in which an aqueous volume is entirely enclosed by membrane composed of lipid molecule. Structuraly,liposomes are concentric bilayer vesicles in which an aqueous volume is entirely enclosed by membranous lipid bilayer mainly composed of natural or synthetic phospholipids .

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Spherical vesicles with a phospholipids bilayer Phospholipid Bilayer . Aqueous cavity

Structural components of liposome's:

Structural components of liposome's Phospholipids Cholesterol

phospholipids:

phospholipids Phospholipids are the major structural components of biological membranes such as the cell membrane PHOSPOGLYCERIDES TWO TYPES OF PHOSPOLIPIDS( ALONG WITH THEIR HYDROLYSIS PRODUCT) SPHINGOLIPIDS

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Phospholipids

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Phospholipids

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The most common phospholipids used is phosphatidylcholine. Phosphatidylcholine is an amphipathic molecule in which . Hydrophilic polar head group, phosphocholine, A glycerol bridge A pair of hydrophobic acyl hydrocarbon chains

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Phospholipids represented as

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Molecules of PC are not soluble in water. In aqueous medium they align themselves closely in planer bilayer sheets in order to minimize the unfavorable action between the bulk aqueous phase and the long hydrocarbon fatty chain. Such unfavorable interactions are completely eliminated when the sheets fold on themselves them to form closed sealed vesicles.

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PC molecules contrast markedly with other amphipathic molecules such as detergents and lysolecithin-in that they form- bilayer sheets Net micellar structures This is thought to be because the double fatty acid chain gives the molecule on overall tubular shape, more suitable for aggregation in planar sheets compared with detergents with a polar heads a single chain whose conical shape fits nicely into spherical micellar structures.

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Some other conventional used phospholipids Naturally occurring phospholipids - PC: phosphatidylcholine (oleoly & palmytoyl chain) - PE: Phosphatidylethanolamine - PS: Phosphatidylserine Synthetic phospholipids - DOPC: Dioleoylphosphatidylcholine - DSPC: Ditsearoylphosphatidylcholine - DOPE: Dioleoylphosphatidylethanolamine - DSPE: Ditsearoylphosphatidylethanolamine

CHOLESTEROL:

CHOLESTEROL Cholesterol by itself does not form bilayer structure. Cholesterol act as fluidity buffer i.e. below phase transition temperature it make membrane less ordered and slightly more permeable . It can be incorporated into phospholipids in very high concentrationabout1:1 or even 2:1 molar ratio of cholesterol to PC. Cholesterol into membrane with its hydroxyl group oriented towards aqueous surface and aliphatic chain aligned parallel to acyl chain in the center of the bil ayer.

Types of liposome:

Types of liposome Liposomes are classified on basis of - structural parameters - method of preparation - composition and application

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Lamella: Types of vesicles on bases of lamella

Classification of liposome:

Classification of liposome

Uses of Liposomes:

Uses of Liposomes Chelation therapy for treatment of heavy metal poisoning Enzyme replacement Diagnostic imaging of tumors Study of membranes Cosmetics

ADVANTAGES OF LIPOSOMES:

ADVANTAGES OF LIPOSOMES Provide selective passive targeting to tumor tissues. E.g. Doxorubicin Increased efficacy and therapeutic index Increased stability of drug. Reduction in toxicity of drug. Improved pharmacokinetic properties. Flexibility to couple with site specific ligands to achieve active targeting

NEED OF Liposome in Drug Delivery :

NEED OF Liposome in Drug Delivery Pharmokinetics - efficacy and toxicity -Changes the absorbance and biodistribution -Deliver drug in desired form -Multidrug resistance Protection- -Decrease harmful side effects Change where drug accumulates in the body -Protects drug Release- -Affect the time in which the drug is released -Prolong time -increase duration of action and decrease administration -

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Liposome Help to Improve Therapeutic index Rapid metabolism Unfavorable Pharmokinetics Low solubility Lack of stability Irritation

REFERENCES:

REFERENCES Allen, Theresa M. "Liposomal Drug Formulations: Rationale for Development and What We Can Expect for the Future." Drugs 56: 747-756, 1998. Allen, Theresa M. "Long-circulating (serially stabilized) liposome for targeted drug delivery ." Tips 15: 214-219, 1994. Target & controlled drug delivery- Novel carrier systems by S.P. Vyas & R.K. Khar. Vesicular drug delivery system by R.S.R. Murthy.

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