Deshpande, S. et al. Nat. Commun. 10, 1800 (2019).

To understand the underlying mechanism of liquid–liquid phase separation (LLPS), researchers have developed in vitro models to reconstitute the process of LLPS. Yet, it is still a challenge to capture the dynamic process of coacervation—droplet formation via LLPS. Deshpande et al. have developed a microfluidic platform to generate liposomes that can be used as containers to control the formation of coacervates. The necessary components are initially loaded inside the liposomes, and the permeation of small molecules into liposomes can trigger phase separation. In addition to the diffusion-mediated coacervate formation, the researchers also demonstrate that the transport of substrate can catalyze an enzymatic reaction that in turn triggers the coacervate formation. The researchers applied the coacervate-in-liposome platform to demonstrate protein (FtsZ) sequestration and β-galactosidase metabolic reaction within coacervates inside liposomes.