A transformable DNA nanomachine serving as both walker and track for sensitive miRNA detection in living cells and...

DNA walkers are powerful nanomachines for biosensing and bioimaging, yet their application in microRNA detection faces significant challenges. Current DNA walker designs often involve complex structures with separate walker and track components, leading to reduced efficiency and potential interference in cellular environments. Here, we developed a self-propelled multi-leg walker (SMW) where autocatalytic hairpin assembly (ACHA) components are anchored on a DNA nanowire to create an initial track structure. Upon target recognition, catalytic hairpin assembly (CHA) reactions dynamically transform sections of track into multi-leg walkers with newly generated triggers. ACHA reactions are then initiated by these triggers, driving the walker to move autonomously along the unreacted track while generating amplified fluorescent signals. The SMW demonstrated excellent performance with a detection limit of 2.9 pM for miR-21, successfully distinguishing cancer cells from normal cells and enabling microRNA detection in clinical tissue samples. This innovative design strategy opens new possibilities for developing simplified yet efficient DNA nanomachines for broader biomedical applications.