Rational Engineering of a Dynamic, Entropy-Driven DNA Nanomachine for Intracellular MicroRNA Imaging.

We rationally engineered an elegant entropy-driven DNA nanomachine with three-dimensional track and applied it for intracellular miRNAs imaging. The proposed nanomachine is activated by target miRNA binding to drive a walking leg tethered to gold nanoparticle with a high density of DNA substrates. The autonomous and progressive walk on the DNA track via the entropy-driven catalytic reaction of intramolecular toehold-mediated strand migration leads to continuous disassembly of DNA substrates, accompanied by the recovery of fluorescence signal due to the specific release of a dye-labeled substrate from DNA track. Our nanomachine outperforms the conventional intermolecular reaction-based gold nanoparticle design in the context of an improved sensitivity and kinetics, attributed to the enhanced local effective concentrations of working DNA components from the proximity-induced intramolecular reaction. Moreover, the nanomachine was applied for miRNA imaging inside living cells.