pH-Sensitive Liposomes for Effective Release of Therapeutics

1. pH-Sensitive Liposomes for Effective Release of Therapeutics By: Savita RamlallMentor: Professor Sofou & Shrirang Karve Polytechnic University Laboratory of Drug Delivery Systems

2. A liposomes is a spherical vesicle with a membrane composed of a phospholipid bi-layer used to deliver drugs or genetic material into a cell. When using liposomes as drug carriers the main aim is to reduce toxic side affects in sensitive organs such as the heart and brain and to target specific tissues such as cancer cells. What are Liposomes?

3. It involves lipid separation which leads to imperfections in membrane. This leads to leakage of drugs. The Purpose of This Project

4. Materials • Prepared liposomes • Pipettes • Fluorescence Spectrometer

5. Procedures • Take Lipids in (CHCl3 solution) in a round bottom flask dried under N2 for 5 minutes • Anneal it with PBS solution for 2 hours • Extrude it through 100 nm membrane • Measure the intensities for excimer and monomer for pH 7.4; 5.5; 4.0

6. Leakage mechanism: lipids with pyrene-labeled fatty acid chains to detect membrane asymmetry and destabilization ex: 344 nm/ em: 396 nm ex: 344 nm/ em: 470 nm

7. Release of contents from rigid PEGylated liposomes vs pH (in PBS) • pH dependent content release • size of ‘lipid-packing’ discontinuities (3kDa dextrans are released similarly, 10kDa dextrans are retained at all pH values)

8. Release of contents from rigid PEGylated liposomes vs pH (in media with 10% serum) • Instantaneous content release at pH 4 • significant release at pH 5.5 • stable content retention at pH 7.4 the first hours

9. raft formation monomer-to-eximer ratio

10. Result & Discussion • Content release at different pH in PBS & media (10% serum) studied using calcein leakage. • Higher content release at lower pH • Membrane asymmetry at different pH was studied using pyrene monomer – excimer ratio. • Asymmetry increases with lower values of pH.

11. Further Studies • During the remaining summer I would like to see the effect of temperature on the raft formation of the liposomal membranes and compare it with the effect of pH levels.

12. References • http://biophysics.org/discussions/2004/london.pdf • http://www.ajhp.org/cgi/content/abstract/46/8/1576 • http://explantion-guide.info/meaning/liposome.html • Ulrich, A Biophysical Aspects of Using Liposomes as Delivery Vehicles vol. 22, NO. 2 (2002) 129-146 • Torchilin, V Fluorescence microscopy to follow the targeting of liposomes and micelles to cells and their intracellular fate. (2004) 96-107 • Lasic, D Noel applications of liposomes vol. 16 (1998) 307-319

13. Acknowledgements • Professor Sofou • Shrirang Karve • Polytechnic University • Everyone in the Laboratory of Drug Delivery Systems • Dr. Sat • Harlem Children Society • The Audience

14. Special Thanks LAB

15. Thank You