1. LIPOSOMES AS DRUG CARRIERS
DEPARTMENT OF PHARMACEUTICS

2. Introduction
Liposomes are simple microscopic vesicles in which an aqueous volume is entirely enclosed by a membrane composed of lipid molecule. Structurally liposomes are concentric bilayered vesicles in which an aqueous volume is entirely enclosed by a membraneous lipid bilayer mainly composed of natural or synthetic phospholipids

3. Structure

4. Liposomes are composed of small vesicles of phospholipids encapsulating an aqueous space ranging from about 0.03 – 10 µm in diameter
Spherical and cylindrical liposomes are made
Multi laminar liposomes prolonged action

5. Classification
Depending upon their structure, liposomes are classified as:
i. MLV (multilamellar vesicles) : These liposomes are made of series of concentric bilayers of lipids enclosing a small internal volume.
ii. OLV (oligolamellar vesicles) : These are made of 2 to 10 bilayers of lipids surrounding a large internal volume.
iii. ULV (unilamellar vesicles) : These are made of single bilayer of lipids.
They may be:
SUV (small unilamellar vesicles) of size 20 to 40 nm,
MUV (medium unilamellar vesicles) of size 40 to 80 nm,
LUV (large unilamellar vesicles) of size 100 to 1000 nm or
GUV (giant unilamellar vesicles) of size greater than 1000 nm.

6. Manufacture of liposomes
They are manufacturing in different lipid compositions by different methods to show variation in particle size, shape, surface potential, no of lamella, encapsulation efficiency, etc.
Surface modification showed great advantage to produce liposomes of different mechanisms, kinetic properties and bio distribution

7. Preparation:
Lipid phase in organic solvent in flask containing glass beads
Removal of solvent leave thin layer of lipid on surface of flask and glass beads
Hydration with saline then vortex Leave for max.swelling

8. Incorporation of drug into liposomes
Polar drugs are incorporated in the aqeous compartment while lipophillic 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

9. A large variety of drugs (antineoplastics, antibiotics), peptides/proteins (including antibodies) and viruses and bacteria can be incorporated into liposomes.
Water-soluble drugs are trapped in the aqueous compartment while lipophilic ones are incorporated in the lipid phase of liposomes.
Because of their availability in various sizes, ability to incorporate both water as well as oil soluble drugs, their inertness and their ability to protect labile drugs, liposomes are versatile carriers for parenteral drug delivery systems.
Intramuscularly and subcutaneously injected liposomes deliver drug at a controlled rate while intravenous administration selectively targets them to reticuloendothelial system and phagocytic cells.

10. Methods of preparation
Involves four basic stages
Drying down from organic solvent
Dispersion of lipids in aqueous media
Purification of resultant liposomes
Analysis of final product

11. Interaction of liposomes with cells
Endocytosis
Stable adsorption
Fusion
Lipid transfer

12. Types of liposomes Conventional
Stealth (PEG, increase blood circulation time and decrease phagocytic attack
Cationic
Targeted

13. Applications cell liposome interaction localized drug effect
enhanced drug uptake
molecules with wide range of solubility and molecular weight can be accommodated
flexibility in structural characteristics

14. Advantages Drug delivery intact to various body tissues
Liposomes can be used for both hydrophilic and hydrophobic drug
Possibility of targeting and decrease drug toxicity
The size, charge and other characteristics can be altered according to drug and desired tissue

15. Disadvantages
Liposomes are rapidly cleared from the circulation and largely taken up by the liver macrophages
How to overcome:
liposome surface ligands decrease degradation (monosialoganglioside or polyoxyethylene)

16. References
N.K.Jain
S.P.Vyas – R.K.Khar
Donald L.Wise

17. Thank you