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LiposomesDr.Issra Al-AniAlahliyya Amman University-Jordan : 

LiposomesDr.Issra Al-AniAlahliyya Amman University-Jordan

History : 

History In 1960s, it was well recognized that microscopic lipid vesicles, known as liposomes, could be utilized to encapsulate drugs and dyes for the purpose of systemic administration and drug targeting. Considerable progress was made in 1980s, in engeneering liposomes to circulate longer in blood and remain intact while doing so.

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Structure: Liposomes are composed of small vesicles of phospholipids encapsulating an aqueous space ranging from about 0.03 to 10 µm in diameter. Spherical and cylindrical liposomes are made. Multilaminar liposomes prolonged action.

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Liposomes can be manufacturing in different lipid comopsitions or by different method show variation in par. Size , size distribution, surface electrical potential, no. of lamella, encapsulation efficacy…… Surface modification showed great advantage to produce liposomes of different mechanisims, kinetic properties and biodistribution.

Composition : 

Composition The phospholipids composing liposomes are amphipathic, possessing both both hydrophilic or polar head and hydrophobic or non polar head. The hydrophobic tail composed of fatty acid containing generally 10-24 carbon atoms and the polar end contain phosphoric acid bound to water – soluble portion.

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Different phosphatidyl cholines

Incorporation of drug into liposome: : 

Incorporation of drug into liposome: Polar drugs are incorporated in the aqeous compartment while lipophilic drugs are intercalated into the liposome membrane. For lipophilic drug maximum incorporation of drug depends on the amount of lipid in the dispersion. Solubility of polar drugs determines the efficient corporation into the liposomes.

Interaction of liposomes with cells: : 

Interaction of liposomes with cells: 1- Endocytosis

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2- Stable adsorption 3- Fusion 4- lipid transfer

Types of liposomes : 

Types of liposomes 1- Conventional. 2- Stealth.(PEG, increase blood circulation time and decrease phagocytic attack. 3- Cationic.(lipoplex) 4- Targeted.(antibody)

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Preparation of liposomes: 1-Lipid phase in organic solvent in flask containing glass beads. 2-Removal of solvent leave thin layer of lipid on surface of flask and glass beads. 3-hydration with saline then vortex. Leave for max. swelling.

Advantages of liposomes : 

Advantages of liposomes 1- drugs delivered intact to various body tissues. 2- liposomes can be used for both hydrophilic and hydrophobic drug. 3- possibility of targeting and decrease drug toxicity. 4-the size, charge and other characteristics can be altered according to drug and desired tissue.

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Disadvantages of liposomes: 1- Their tendency to be uptaken by RI system. 2- They need many modification for drug delivery to special organs. 3- cost.

Products in the market : 

Products in the market Doxorubicin (Doxil, Myocet) (KS Kaposis sarcoma) Daunorubicin (Dauno Xome) Cytarabin (Depocyte) (lymphotmatos meningitis) Amphotericine B (Ambisome) (fungal infection)

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