Pattern Regulation of DNA Hydrogels Formed by Lateral Phase Separation of DNA Nanostructures on Water-in-Oil Droplet Interfaces

Phase separation is a key phenomenon in artificial cell construction. Recent studies have shown that the liquid-liquid phase separation of designed-DNA nanostructures induces the formation of liquid-like condensates that eventually become hydrogels by lowering the solution temperature. As a compartmental capsule is an essential artificial cell structure, many studies have focused on the lateral phase separation of artificial lipid vesicles. However, controlling phase separation using a molecular design approach remains challenging. Here, we present the lateral liquid-liquid phase separation of DNA nanostructures that leads to the formation of phase-separated capsule-like hydrogels. We designed three types of DNA nanostructures (two orthogonal and a linker nanostructure) that were adsorbed onto an interface of water-in-oil droplets via electrostatic interactions. The phase separation of DNA nanostructures led to the formation of hydrogels of bicontinuous, patch, and mix patterns, due to the immiscibility of liquid-like DNA during the self-assembly process. The frequency of appearance of these patterns was regulated by designing DNA sequences and altering the mixing ratio of the nanostructures. We constructed a phase diagram for the capsule-like DNA hydrogels by investigating pattern formation under various conditions. Our results provide a method for the design and control of phase-separated hydrogel capsules using sequence-designed DNAs. We envision that by incorporating various DNA nanodevices into DNA hydrogel capsules, the capsules will gain molecular sensing, chemical-information processing, and mechano-chemical actuating functions, allowing the construction of functional molecular systems.