Simply Constructed and Highly Efficient Classified Cargo-Discharge DNA Robot: A DNA Walking Nanomachine Platform for Ultrasensitive Multiplexed Sensing

In this work, a classified cargo-discharge DNA robot with only two DNA strands was designed and driven by an analogous proximity ligation assay (aPLA)-based enzyme cleaving for fast walk to construct a novel electrochemical biosensor for simultaneously ultrasensitive detection of microRNA-155 (miRNA-155) and miRNA-21. Compared with traditional DNA nanomachines, the multifunctional DNA robot possessed simple structure, high self-assembling efficiency and walking efficiency. Once it interacted with target miRNAs, this DNA robot could walk fast on the electrode surface and realize the classified cargoes discharging including beacons methylene blue (MB) and ferrocene (Fc), respectively labeled in the double-stranded DNA (A1-A2) for ultrasensitive detection of multiple miRNAs simultaneously. As a result, the wide linearity ranging from 100 aM to 100 pM and low detection limits of 42.7 and 51.1 aM were obtained for miRNA-155 and miRNA-21 detection, respectively. As a proof of concept, the present strategy initiates a novel and highly efficient walking platform to realize the ultrasensitive detection of biomarkers and possesses potential applications in the clinical diagnosis of disease.