Synthesis of Monomethoxypolyethyleneglycol—Cholesteryl Ester and Effect of its Incorporation in Liposomes
The objective of the present study was to synthesize monomethoxypolyethyleneglycol-5000 cholesteryl ester [PEG–CH] as a cost-effective substitute for polyethyleneglycol–phosphatidylethanolamine and to evaluate the influence of its incorporation in liposomal bilayers for surface modification. PEG–CH was synthesized and characterized by infrared (IR), proton nuclear magnetic resonance spectroscopy (1H NMR), and differential scanning calorimetry (DSC) studies. Influence of incorporation of PEG–CH in liposomes was evaluated on various parameters such as zeta potential, DSC, and encapsulation efficiency of a hydrophilic drug pentoxyfylline. Conventional and PEG–CH containing pentoxyfylline liposomes were formulated and their stability was evaluated at 4°C for 3 months. PEG–CH could be successfully synthesized with good yields and the structure was confirmed by IR, DSC, and 1H NMR. The incorporation of PEG–CH in liposomes resulted in reduction of the zeta potential and broadening of the DSC endotherm. Furthermore, incorporation of PEG–CH in liposomes decreased the encapsulation efficiency of pentoxifylline in liposomes when compared to conventional liposomes. Conventional and PEG–CH containing pentoxyfylline liposomes did not show any signs of pentoxyfylline degradation when stored at 4°C for 3 months.
KEY WORDSliposomes PEG–cholesteryl ester steric stabilization
Vinayak P. Sant is thankful to CSIR, New Delhi for the award of Senior Research Fellowship. Authors acknowledge the help of Dr. Krishna Iyer and Dr. Abhijit Date for manuscript preparation and useful discussions. The kind help of Phospholipid GmBH, Germany and Sun Pharmaceuticals, India is also gratefully acknowledged.
- 18.Sant VP, Paradkar AR, Nagarsenker MS. Optimization of pentoxifylline liposomes using 24 factorial design. Ind J Pharm Sci. 2002;64:459–64.Google Scholar