Liposome - A novel drug delivery systems, classification and methods of manufacturing

Liposomes are simple microscopic lipid vesicles in which an aqueous volume is entirely enclosed by a membrane composed of lipid molecule.

1. Presented by- Sneha Singh M. Pharm ( 3 rd sem )Pharmaceutics LIPOSOMES GROUP OF INSTITUTIONS (FACULTY OF PHARMACY , BHOPAL ) Guided by- Dr Ankit Mishra Professor PG Co-Ordinator Faculty of Pharmacy

2. CONTENT Introduction Composition of liposomes. Mechanism of liposome formation. Classification. Methods of preparation. Applications and commercial products.

3. Liposome - The word liposomes derives from two Greek words: lipo (fat) and soma (body). -Liposomes are simple microscopic vesicles in which an aqueous volume is entirely enclosed by a membrane composed of lipid molecule. -Liposomes were first produced in England in 1961 by Alec D. Bangham . INTRODUCTION

4. STRUCTURE OF LIPOSOMES They are concentric bilayered vesicles. The size of a liposome ranges from some 20nm up-to several micrometers. The sphere like shell encapsulated a liquid interior contains substances such as peptides and protein, hormones, enzymes, antibiotics, antifungal and anti-cancer agents.

5. COMPOSITION OF LIPOSOMES The main components of liposomes are: 1. Phospholipids 2. Cholesterol Phospholipids: They are the fatty substance and basic molecular building block of liposomes. It is a lipid which is amphipathic; consists of – 1 hydrophilic polar head 2 hydrophobic tails. Most commonly used phospholipids are- Phosphatidylcholine or PC Phosphatidylethanolamine.

6. Cholesterol: Cholesterol act as fluidity buffer. Enhances the stability of the membrane. Enhances the rigidity of the phospholipid bilayer.

7. ADVANTAGES -Suitable for delivery of hydrophobic, hydrophilic and amphipathic drugs and agents. -Liposomes increases efficacy and therapeutic index of drug. -Increases stability via; encapsulation. -Naturally occurring lipids are non-toxic & biodegradable. DISADVANTAGES - Short half life . - Production cost is high. -Sometimes phospholipid undergoes oxidation and hydrolysis like reaction.

8. MECHANISM FOR FORMATION OF LIPOSOME -In aqueous media phospholipids, as they are not soluble align themselves closely in planar bilayer sheets or lipid cakes which is thermodynamically stable. -It consists of polar head groups face outwards into the aqueous medium, and the lipid chains turns inwards to avoid the water phase, giving rise to double layer or bilayer. -This structure is also called as LAMELLA. -For the liposomes to be formed, upon further hydration, the lipid cakes(lamella) swells eventually they curve to form a closed vesicles in the form of spheres. -These spheres are called as liposomes.

9. CLASSIFICATION OF LIPOSOMES Classification based on size of liposomes Classification based on method of preparation. Classification based on composition and applications.

10. Classification based on size of liposome

11. Classification based on method of preparation Vesicles prepared by reverse phase evaporation method REV Multi lamellar vesicle by REV MLV-REV Stable plurilamellar vesicle SPLV Frozen & thawed MLV FATMLV Vesicles prepared by extrusion techniques VET Dried reconstituted vesicles DRV Classification based on composition and application Conventional liposomes(CL) - neutral/negatively charged phospholipids and cholesterol Fusogenic liposomes - Reconstituted Sendai Virus Envelopes(RVSE) pH sensitive liposomes - using phospholipids as; PE or DOPE with OA Cationic liposomes - cationic lipids with dope Long circulatory liposomes(LCL)- high Tc made using cholesterol and 5-10% PEG-DSPE Immuno-liposomes - with attached monoclonal antibody

12. GENERAL METHOD FOR PREPARATION OF LIPOSOME

13. METHODS OF LIPOSOME PREPARATION

14. HAND SHAKING METHOD: Surfactant & cholesterol (150 µmole ) Solution is dissolved in 10ml ether in round bottom flask Ether is evaporated under vacuum at room temperature Surfactant swells and peeled off into a film like lipids Swollen amphiphiles fold to form vesicles. Rotary evaporator hydration NON-HAND SHAKING METHOD: -The procedure differs from hand shaken method wherein it uses a stream of nitrogen to provide agitation rather than rotationary movements. - Here the lipid film is exposed to water saturated nitrogen for 15-20 min.

15. MICRO EMULSIFICATION -This method is provided for preparing small lipid vesicles in commercial quantities by micro emulsifying lipid compositions using very high shear forces generated in a homogenizing apparatus operated at high pressures at a selected temperature. -At least 20 circulations (approximately 10 minutes) but not greater than 200 circulations (100 minutes) are sufficient to produce a micro emulsion of small vesicles suitable for biological applications. SONICATION METHOD: The small unilamellar vesicles (SUVs) are produced from MLVs by exposing the MLVs to ultrasonic irradiation.

16. FRENCH PRESSURE CELL METHOD: -It is used for SUVs by passing MLVs through a narrow orifice under high pressure. -Liposomes prepared by this method are less likely to suffer from structural defects & instabilities as observed in sonicated vesicles. MEMBRANE EXTRUSION METHOD: -Liposomes passed through polycarbonate membrane of defined pore size. Lower pressure is required (<100psi). -LUVs as well as MLVs can be processed. French pressure cell

17. DRIED RECONSTITUTED VESICLES (DRV) AND FREEZE THAW SONICATION (FTS): ETHANOL/ETHER INJECTION METHOD:

18. REVERSE-PHASE EVAPORATION: Lipid organic solvent and aqueous solution are: Mixed, Sonicated, Formation of w/o emulsion, Evaporate to remove the organic solvent. Lipids form a phospholipid bilayer on vigorous shaking, water droplets collapse and formation of LUVs takes place. DETERGENT REMOVAL METHOD: Upon removal of detergent, transition of mixed micelles occurs to form concentric bilayered vesicles. The following methods are used to remove the detergent: Dialysis Column chromatography

19. APPLICATIONS OF LIPOSOME 1.Liposomes as drug or protein delivery vehicles. 2.Liposome as vaccine carrier. 3.Liposome in tumour therapy. 4.Liposome in gene delivery. 5.Liposome in cosmetics and dermatology. 6.Liposome as artificial blood surrogates. 7.Liposome as radio-pharmaceutical & radio-diagnostic carrier. 8.Enzyme immobilization.

20. LIST OF MARKETED PRODUCTS NAME TRADE NAME COMPANY INDICATION Liposomal amphotericin B Abelcet Enzon Fungal infections Liposomal Amphotericin B Ambisome Gilead sciences Fungal and protozoal infections Liposomal cytarabine Depocyt Pacira (formerly Skye pharma) Malignant lymphomatous meningitis Liposomal doxorubicin Myocet Zeneus Combination therapy with cyclophosphamide in metastatic breast cancer. Liposomal IRIV vaccine Inflexal V Berna Biotech Influenza Liposomal morphine DepoDur Skye Pharma Post surgical analgesia

21. CONCLUSION Liposome over the years have been investigated as major drug delivery system. The use of liposomes in delivery of drugs and genes to the tumor sites are promising and may serve as handle for focus of future research.