Copolymers Composed of 2-(Methacryloyloxy)ethyl Phosphorylcholine and Methacrylated Polyhedral Oligomeric Silsesquioxane as a Simple Modifier for Liposomes

PEGylated liposomes have been used as carriers for delivery of anticancer drugs like doxorubicin (DOX) because of their bioinert nature. However, repeated administration of the PEGylated liposomes results in accelerated blood clearance (ABC) phenomenon caused by immune response of the PEGylated surface. To escape the ABC phenomenon, alternative modification of the liposome surface is needed while maintaining good stability in a blood environment. In this study, we focused on random and diblock copolymers composed of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and methacrylate R-POSS (vertex R-groups of polyhedral oligomeric silsesquioxanes (POSS) cage modified with ethyl (C 2 ), hexayl (C 6 ), octayl (C 8 ) alkyl chain). The C 8 alkyl chain was found to strongly interact with the lipid bilayer of the liposomes as well as the interactions between phosphorylcholine groups of liposome and the MPC parts. The liposomes were stabilized by the MPC/POSS copolymers in 50% (v/v) serum. The experimental results suggested that MPC/POSS copolymers have a great potential to improve the stability of liposomes as carriers of anticancer drugs.