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 liposomeHydrophilicHydrophobicSpherical vesicles with a phospholipidbilayer

4. Cell Membrane

5. Advantages of LiposomesThey 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 LiposomesA 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.

7. Why Use Liposomes in Drug Delivery?Pharmokinetics - efficacy and toxicityChanges the absorbance and biodistribution

8. Deliver drug in desired form

9. Multidrug resistanceProtectionDecrease harmful side effects

10. Change where drug accumulates in the body

11. Protects drugWhy Use Liposomes in Drug Delivery?ReleaseAffect the time in which the drug is released

12. Prolong time -increase duration of action and decrease administrationDependent on drug and liposome properties:Liposome composition, pH and osmotic gradient, and environmentTargeted Liposome delivery system

13. Preparation of targeted Liposomes