Photoinduced Pinocytosis for Artificial Cell and Protocell Systems

A photocleavable membrane component was introduced into synthetic liposomes to achieve light-triggered pinocytosis-like behavior as a potential solution to the feeding requirement in protocell and bottom-up artificial cell systems. Light-triggered pinocytosis was observed in both elongated liposomes, prepared by lipid film hydration, and osmotically stressed spherical vesicles prepared by the pull-down method. Liposomes formed via lipid film hydration consistently underwent pinocytosis in cases of lobed structures or in prolate ellipsoidal structures with aspect ratios ≥2, suggesting that a critical volume-to-surface-area ratio is necessary to drive pinocytosis. When liposomes formed by the pull-down method were osmotically deformed prior to irradiation, an average of 44% exhibited pinocytosis. This light-driven pinocytosis behavior is hypothesized to be due to an asymmetric distribution of photocleavable lipid between the inner and outer leaflet, consistent with the observation that liposomes assembled a...