Temporally controlled multistep division of DNA droplets for dynamic artificial cells

Bio-soft matter droplets formed via liquid-liquid phase separation (LLPS) of biopolymers have been found in living cells. Synthetic LLPS droplets have recently been employed in nanobiotechnology for artificial cell construction, molecular robotics, molecular computing, diagnosis, and therapeutics. Controlling the dynamics of bio-soft matter droplets is essential for developing such bio-inspired functional systems because living systems maintain their functions based on the temporally controlled dynamics of biomolecular reactions and assemblies. Recently, the dynamics of bio-soft matter droplets have been revealed; however, their temporal control has not yet been achieved. This paper reports the temporal control of DNA-based LLPS droplets (DNA droplets). We demonstrate the timing-controlled division of DNA droplet-based artificial cells via time-delayed division triggers regulated by non-equilibrium chemical reactions. We also investigated it using a reaction-diffusion model. We regulated the release order of multiple division triggers, resulting in order control of the multistep droplet division, that is, pathway control of the droplet division in a reaction landscape. Finally, we demonstrate an application of the timing-controlled division of DNA droplet-based artificial cells: a molecular computing element to compare the concentrations of microRNA sequences (called molecular comparators). We believe that temporal control of DNA droplets will promote the design of more dynamic artificial cells/molecular robots and more sophisticated biomedical applications.