Lipase activated endocytosis-like behavior of oil-in-water emulsion.

Oil-in-water emulsion is a system with extensive applications in foods, cosmetics and coating industries, and it could also be designed into an artificial lipid droplet in recent works. However, the insights into the biophysical dynamic behaviors of such artificial lipid droplets are lacking. Here, we reveal an enzymatic reaction triggered endocytosis-like behavior in the oil-in-water emulsion lipid droplets. A thermodynamically favored recruitment of lipases onto the membrane of the droplets is demonstrated. We confirm that the hydrolysis of tributyrin by lipases can decrease the interfacial tension and increase the compressive force on the membrane, which are the two main driving forces for triggering the endocytosis-like behavior. The endocytosis-like behavior induced various emerging functionalities of the lipid droplets, including proteins, DNA or inorganic particles being efficiently sequestered into the oil droplet with reversible release as well as enhanced cascade enzymatic reaction. Overall, our studies are expected to open up a way to functionalize oil-in-water emulsions capable of life-inspired behaviors and tackle emerging challenges in bottom-up synthetic biology, revealing the unknown dynamic behaviors of lipid droplets in living organisms.