pH-Controlled Resettable Modular DNA Strand-Displacement Circuits.

Sophisticated dynamic molecular systems with diverse functions have been fabricated by using the fundamental tool of toehold-mediated strand displacement (TMSD) in the field of dynamic DNA nanotechnology. However, simple approaches to reset these TMSD-based dynamic systems are lacking due to the difficulty in creating kinetically favored pathways to implement the backward resetting reactions. Here, we develop a facile proton-driven strategy to achieve complete resetting of a modular DNA circuit by integrating a pH-responsive intermolecular CG-C triplex DNA and an i-motif DNA into the conventional DNA substrate. The pH-programmed strategy allows modular DNA components to specifically associate/dissociate to promote the forward/backward TMSD reactions, thereby enabling the modular DNA circuit to be repeatedly operated at a constant temperature without generating any DNA waste products. Leveraging this tractable approach, we further constructed two resettable DNA logic gates used for logical computation and two resettable catalytic DNA systems with good performance in signal transduction and amplification.