Phase-separated cationic giant unilamellar vesicles as templates for the polymerization of tetraethyl orthosilicate (TEOS)

Abstract

Unlike homogeneous liposomes, phase-separated liposomes have the potential to be attractive soft materials because they exhibit different properties for each phase. In this study, phase separation was observed when liposomes were prepared using 1,2-dioleoyloxy-3-trimethylammonium propane chloride (DOTAP), 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC), and cholesterol. The pH of the DOTAP-rich phase was evaluated using a coumarin derivative, and measurements showed that DOTAP molecules accumulated hydroxyl ions (OH⁻) in the DOTAP-rich phase. Such accumulation of OH⁻ was not observed when homogeneous DSPC liposomes were used. The difference in local concentration of OH⁻ in each phase was applied to prepare hollow silica particles with large pores. The OH⁻ promotes the polymerization of tetraethyl orthosilicate (TEOS). Therefore, TEOS polymerized preferentially in the DOTAP-rich phase, whereas a silica membrane barely formed in the DSPC-rich phase.