DNA Droplets: Design, Characterization, and Manipulation

We describe a single-component coacervate droplet comprised entirely of DNA. These DNA droplets are based on a multi-arm geometry termed a DNA nanostar. In our system, every nanostar exhibits four arms that each terminates in a single-stranded DNA overhang (sticky end) with a palindromic sequence. The sticky ends enable transient base-pairing interactions between nanostars, leading to a liquid-liquid phase separation in low-temperature, high-salt conditions. We observe that the viscosity and surface tension of DNA droplets can be controlled by altering the ionic strength of the solution as well as the sequence of the overhangs. We further show that mixtures of two types of nanostars, with different, non-interacting sequences, form two immiscible liquid phases. However, when there is partial complementarity between the two sticky ends, the two types of droplets can adhere, forming low curvature interfaces. We present correlations between the interfacial angles and hybridization energy for various pairs of overhang sequences.