Fabricating and Actuating DNA Origami Mechanisms

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DNA origami enables the precise fabrication of nanoscale geometries. We demonstrate an approach to engineer complex and reversible motion of nanoscale DNA origami mechanisms. Following a traditional macroscopic machine design approach, we developed flexible DNA origami rotational and linear joints that integrate stiff double-stranded DNA components and flexible single-stranded DNA components to constrain motion along a single degree of freedom and demonstrate the ability to tune flexibility and range of motion. Linear motion was achieved by folding a tube concentrically around a track through a novel approach of programmed sequential folding so the track folds first, and then the tube is constrained to assemble around the track. Multiple joints were then integrated into various higher order mechanisms including a crank–slider that couples rotational and linear motion. We have also demonstrated multiple actuation methods to achieve reversible conformational changes via input strands to form new connections distributed throughout the mechanisms. One approach uses stable input strand connections with DNA strand displacement, and we have established an approach for reversible actuation that relies on transient binding of many weak affinity input strands. In this case, the reverse actuation can be achieved simply by removing the input strands from solution. Also, we have recently developed a similar actuation method using weak complementary overhang connections that can that can be controlled by adjusting cation concentration. We expect these approaches can improve actuation times because they do not rely on strand displacement. In addition, with both approaches, we can tune the dynamics to see conformational changes in specific ranges of concentrations. Our results demonstrate programmable motion of 2D and 3D DNA origami mechanisms constructed following a macroscopic machine design approach with steps towards fast mechanical actuation.