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.