Engineering motile aqueous phase-separated droplets via liposome stabilisation

Abstract There are increasing efforts to engineer functional compartments that mimic aspects of cellular behaviour in a drive to construct an artificial cell from the bottom-up. One behaviour that is receiving particular attention is motility, due to its biotechnological potential and the fact that movement of discrete cells is a ubiquitous feature of living systems. Many existing platforms make use of the Marangoni effect to achieve motion in water/oil (w/o) droplet systems. However, most of these systems are unsuitable for biological applications due to issues with biocompatibility caused by the presence of oil phases. Here we report a biocompatible all aqueous (w/w) PEG/dextran Pickering-like emulsion system consisting of liposome-stabilized cell-sized droplets, where the stability can be easily tuned by adjusting liposome composition and concentration. We demonstrate that the compartments are capable of negative chemotaxis: if water is introduced into the emulsion system, these droplets can respond through directional motion away from PEG in the continuous phase and down to the polymer gradient with a velocity change proportional to the rearrangement of liposome stabilisers in the PEG/dextran interface. The biocompatibility, motility and partitioning abilities of this novel droplet system offers new directions to pursue research in motion-related biological processes.