Enzymatic Janus Liposome Micromotors

A liposome-based micromotor system that utilizes regional enzymatic conversion and gas generation to achieve directional motion in water is presented. Constituted mainly of a low-melting lipid and a high-melting lipid together with cholesterol, these liposomes maintain stable Janus configuration at room temperature as a result of lipid liquid-liquid phase separation. Local placement of enzymes such as horseradish peroxidase is realized via affinity binding between avidin and biotin, the latter as a lipid conjugate sorted specifically into one domain of these Janus liposomes as a minor component. In the presence of the substrate, hydrogen peroxide, these enzyme-decorated Janus liposomes undergo directional motion, yielding velocities exceeding thermal diffusion by three folds in some cases. Experimental details on liposome size control, motor assembly, and substrate distribution are presented; effects of key experimental factors on liposome motion, such as substrate concentration and liposome Janus ratio, are also examined. This work thus provides a viable approach to building asymmetrical lipid-assembled, enzyme-attached colloids and, in addition, stresses the importance of asymmetry in achieving particle directional motion.

Automated summary

A liposome-based micromotor system that achieves directional motion in water by using regional enzymatic conversion and gas generation is presented. These liposomes, composed of low-melting and high-melting lipids along with cholesterol, maintain stable Janus configuration through lipid liquid-liquid phase separation. Local placement of enzymes is achieved through affinity binding, resulting in enzyme-decorated liposomes that undergo directional motion in the presence of substrate hydrogen peroxide. Experimental details on liposome size control, motor assembly, and substrate distribution are provided, highlighting the importance of asymmetry in achieving particle directional motion.