Towards Synthetic Life—Molecular Design of Complex Coacer-vates that Self-Divide

Complex coacervation occurs when oppositely charged polyelectrolytes interact, leading to liquid-liquid phase separation. We coupled this phase separation to a fuel-driven reaction cycle, leading to active droplets that emerge when fuel is supplied and dissolve when the energy source is depleted. These behaviors make them an exciting protocell model and a promising step toward synthetic life. However, these active coacervate droplets cannot self-divide—critically important for Darwinian evolution and, by extension, synthetic life. This work demonstrates how to design division in active complex coacervate droplets. We found that mixtures of long and short polyanions lead to tiny speckles inside the active droplets. As the droplet dissolves, these speckles made of the long polyanion liberate as daughter droplets. In fueling-starvation-fueling experi-ments, we can rescue the offspring by adding the second batch of fuel. Finally, we showed that we can include molecules partitioning in the com-plex coacervates, which stay in the offspring until they eventually dissolve. We envision combining our self-division of self-sustaining droplets with replicators that aid the droplets can open the door to Darwinian evolution in synthetic cells.