Liposomes are spherical vesicles made of phospholipids that can encapsulate both hydrophilic and hydrophobic drugs. They improve drug delivery by protecting drugs, altering biodistribution and pharmacokinetics, and enabling targeted release. Liposomes can be modified with polymers or ligands to selectively deliver drugs to specific tissues or cells, prolong drug circulation time, and decrease side effects. Medical applications of liposomes include cancer and antimicrobial treatments, diagnostic imaging, and localized drug delivery to tumors or specific cells.

1. Liposomes: Improving drug delivery

2. What is a liposome? Liposomes are closed vehicles having both lipophilic and hydrophilic portions. Size range is from 25nm to as much as 10mm. Made from naturally occuring phospholipids such as phosphatidylcholine , cholesterol. Also obtained from synthetic phospholipids like phosphatidylinositol.

3. Structure of liposome Hydrophilic Hydrophobic Spherical vesicles with a phospholipidbilayer

4. Cell Membrane

5. Advantages of Liposomes They can incorporate both hydrophobic and hydrophilic drugs in them. Their surfce can be modified to alter their biodistribution and pharmakokinetics. Alter drug distribution according to their size. Liposomes can be made to release the entrapped drugs at increased temperatures.

6. Advantages of Liposomes A number of anticancer and anti-microbiologic agents such as Cytosine, Arabinoside, Methotrexate, Doxorubicin, Dactinomycin and AmphotericinB are entrapped. These can be grafted with hydrophilic polymers such as PEG to reduce their uptake by macrophages.

8. Deliver drug in desired form

10. Change where drug accumulates in the body

13. Preparation of targeted Liposomes

14. Modes of Liposome/Cell Interaction Adsorption Endocytosis Fusion Lipid

15. Medical Applications of Liposomes Chelation therapy for treatment of heavy metal poisoning Enzyme replacement Diagnostic imaging of tumors Cosmetics Study of membranes Localised delivery of drug is possible.

16. Medical Applications of Liposomes Used for tumor imaging. Ligand mediated targeted drug delivery by long circulating liposomes. Antibodies can be conjugated to PEG chains on PEG stabilized liposomes. To treat artherosclerosis or neointimal hyperplasia. For targeted gene delivery to specific cells.