Modular nanostructure design of DX-tile DNA nano-stars (DX-DNAns) controls self-organization and force propagation of DX-based DNA Hydrogels yielding a soft matter metamaterial with programmable viscoelastic properties and integrated functionalization

Deoxyribonucleic Acids (DNA) have been used since 1982 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 the double crossover (DX) motif 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 coordinate the propagation of forces both within and across the different motifs driving unique organizational aspects which produce specific viscoelastic features, as evidenced by bulk-scale rheological profiles herein. This work begins to bridge the broad range of complexities available with DNA origami based nanostructures to the more application based potentials for macro-scale nanostructured materials with specified functionalizations. Particularly I elucidate the versatility of this method by implementing a DNA based pH response motif, i-motif, which has thus far only enabled switchable mechanical properties from the gel-to-sol states but herein there are graded changes in mechanistic properties while sustaining the gel state, a feat which has only been achieved via strand displacement in DNAns hydrogels thus far. The resulting metamaterial demonstrates the breadth of new possibilities for DNA hydrogels with the extensive functionality of bundled duplexes used in DNA Origami thus seeding the bridge to a fundamental gap in the field by pinpointing this new fundamental design factor.