Liquid DNA Coacervates form Porous Capsular Hydrogels via Viscoelastic Phase Separation on Microdroplet Interface

Abstract

Liquid–liquid phase separation (LLPS) droplets of biopolymers are known as functional microdroplets in living cells and have recently been used to construct protocells and artificial cells. The formation of DNA coacervates (also referred to as DNA droplets) from branched DNA nanostructures and the control of their physical properties via DNA nanostructure design are demonstrated previously. For the construction of artificial cells or protocells, however, even though physical effects such as surface tension, wetting, and viscoelasticity are more important in a tiny (micrometer‐sized), confined environment than in a bulk solution environment, they have not been explored yet. This study shows that a tiny, confined environment using a water‐in‐oil (W/O) microdroplet interface modulates the phase separation dynamics of DNA coacervates, leading to micrometer‐sized porous capsular structures. The porous structures are produced via two types of viscoelastic phase separation (VPS) processes in DNA coacervates: i) simple VPS and ii) cluster‐cluster aggregation after VPS. Finally, it is shown that environmental chemical stimulation can manipulate porous capsular DNA hydrogels extracted from W/O microdroplets. These results provide an approach for designing and fabricating artificial cells or protocells with complex structures and physicochemical properties.

Pioneering artificial cell-like structures with DNA nanotechnology-based liquid-liquid phase separation

“…Because DNA is a negatively charged polymer molecule, when cell-sized water-in-oil (W/O) droplets were prepared with positively charged amphiphilic molecules, DNA nanostructures were adsorbed on the water/oil interface. When the W/O droplet solution, whose aqueous phase contains the Y-motif, was heated and cooled gradually, the porous pattern was formed [16] (Fig. 4a).…”

“…This phenomenon was explained by three factors: accumulation of the motifs at the interface, (2) concentration of the accumulated motifs, and (3) diffusion of the motifs. The detailed mechanism of the phenomena is described in the reference paper [16].…”

“…Detailed investigation of the relationship between the space size and the pattern formed, as well as the pattern formation process, may lead to the construction and control of artificial cell nuclei. An important achievement in the above works is that the formed structures on the W/O droplet interfaces can be extracted to aqueous solution [16,17] (Fig. 4c and 4d).…”