Dynamical Regulation of Enzyme Cascade Amplification by a Regenerated DNA Nanotweezer for Ultrasensitive Electrochemical DNA Detection.

Traditional scaffolds such as metal nanoparticles and DNA origami remain a considerable challenge to regulate the enzyme cascade catalytic efficiency dynamically and reversibly on account of their irreversible conformation. To address these issues, a regenerated DNA tweezer was designed to dynamically regulate the interenzyme spacing for high-efficiency enzyme cascade amplification for homogeneous determination of target DNA related to cancer diseases. Initially, the enzyme-functionalized DNA tweezer was maintained at the opened state with a relatively distant interenzyme distance (19-24 nm), leading to a low catalytic efficiency. Benefiting from target induced Mg2+-dependent DNAzyme cleavage recycling, the one input target could be transduced to multiple corresponding methylene blue (MB) labeled DNA (S5), which served not only as the signal probe to provide a detectable electrochemical signal but also fuel to switch the DNA tweezer from the opened to closed state, leading to cascaded enzymes close enough (5-10 nm) for enhancing the catalytic efficiency for sensitive target DNA analysis with a low detection limit down to 30 fM. In the presence of antifuels, the closed DNA tweezer easily switched back to the opened state via a one-step strand displacement, and the obtained DNA tweezer achieved regeneration for subsequently recycling target detection. With the dynamical regulation of interenzyme distance in an "open-close-open" way, the enzyme cascade catalytic efficiency became dynamically controllable, and the DNA tweezer realized simple reutilization over five times, overcoming the drawbacks of inflexible, time-consuming operation and false positive signal induced by traditional scaffolds. More importantly, this method opened a new avenue for employing the arbitrary change of enzyme cascade catalytic efficiency for sensitive detection various biomolecules.