Modular nanostructure design of DX-tile DNA nano-stars (DX-DNAns) controls self-organization and force propagation of DX-based DNA Hydrogels enabling programmable viscoelastic properties and integrated functionalization

Deoxyribonucleic Acids (DNA) have been used for a few decades to form nanostructures with precisely tunable features, shapes, responses, etc. Some of the most basic structures, DNA nanostars (DNAns) have been used to form soft matter hydrogels with unique functionalizations and responses to soluble stimuli as well as physical cues. Notably these studies use 'arms' comprising a single duplex whereas more complex nanostructures, DNA origami, can have a multitude of duplexes bundled together to produce different structural properties. Herein I introduce DNAns bundling two duplexes together, commonly known as double crossover (DX) motifs to enable multi scale mechanical design of hydrogels with interchangeable strands, i.e. modular DX-DNAns hydrogels. This is achieved by rational design of the internal structure to facilitate the propagation of forces through and across the different motifs driving unique organizational aspects which produce specific viscoelastic features evidenced by bulk-scale rheological profiles. This work begins to bridge the near endless complexities available with DNA origami based nanostructures to the more application based potentials for large-scale functional nanostructured materials. Particularly I highlight the versatility of this method by implementing a DNA based pH response motif, i-motif, which has this far only enabled switchable mechanical properties from the gel-to-sol states but herein there is graded change in mechanistic properties while sustaining the gel state, something that has only been achieved via strand displacement in DNAns hydrogels thus far. Demonstrating the breadth of new possibilities for DNA hydrogels with the added functionality of bundled duplexes used in DNA Origami effectively ushering in a 'new era' for the field.