Starch Granules as Programmable Nucleation Sites for DNA Nanostar Self-Assembly

DNA-based materials have attracted significant interest, as their properties can be precisely controlled through modulation of the encoded sequence. Specific DNA oligomers can be assembled into three-dimensional DNA nanostars, which undergo liquid-liquid phase separation and network formation based on the flexibility of the structure. However, understanding additional mechanisms to control the properties of nanostar-based materials remains a topic of interest. Here, we show that starch granules, which offer a polyvalent surface for easy modulation of surface charge, serve as nucleation sites for nanostar self-assembly. Using fluorescence confocal microscopy, we observe rapid hydrogel nucleation and growth on the order of seconds, compared to hours in the absence of starch. Additionally, we show that by chemically modifying the starch granules to have positive, negative, or neutral surface charges, we can tune the self-assembly process and resultant structure across a wide phase space. With their rapid self-assembly and tunability, starch-DNA composites can serve as models for understanding and engineering tissues and biomolecular condensates, where the chemistry and concentration of starches can function as tuning knobs to control nucleation and local self-assembly.