In this work, it is demonstrated that liposome active motion takes advantage of mainly a pair of intrinsic material properties associated with these assemblies: lipid phase separation and extraction. It is shown that global phase separation of ternary lipid systems (such as DPPC/DOPC/cholesterol) within individual liposomes yields stable Janus particles with two distinctive liquid domains. While these anisotropic liposomes undergo pure Brownian diffusion in water, similar to their homogeneous analogues, adding extracting agents, cyclodextrins, to the system triggers asymmetrical cholesterol efflux about the liposomes, setting the latter into active motion. We present detailed analyses of liposome movement and cholesterol extraction kinetics to establish their correlation. Various experimental parameters as well as mechanistic details to account for such motion are explored. The results highlight the rich possibility to hierarchically design lipid-based artificial motors, from individual lipids, to their organization, surface chemistry, and interfacial mechanics.
Jinyan Cui, Hui Jin, and Wei Zhan (2022) Enzyme-Free Liposome Active Motion via Asymmetrical Lipid Efflux. Langmuir