A programmatic electrochemical nanosensor based on robust bipedal DNA walkers fueled by catalytic hairpin assembly

In this paper, a robust and highly integrated DNA bipedal walker based electrochemical biosensor was designed on single nanoelectrodes for ultrasensitive miRNA-21 detection through click chemistry, enzyme-free target recycling amplification strategy and programmed catalysis hairpin assembly. Triggered by target miRNA-21, the DNA bipedal walker was built through hybridization and chemical ligation of two hairpin DNA probes (W1 and W2), accompanied with the releasing of target. Then driven by MB-labeled hairpin DNA (MB-FS), the DNA bipedal walker was activated to run continuously along the DNA track and attach a large number of signal molecules MB on the nanoelectrode surface, resulting in cascade signal amplification. With the target recycling amplification strategy and DNA walker, the biosensor showed high analysis performance in detection of miRNA-21 including wide detection range (0.1 fM-50 pM), low detection limit (60 aM) and high selectivity. What’s more, owing to the proximity-dependent hybridization and programmed catalysis hairpin assembly, the nanosensor was one-incubated and regenerative which showed a promising approach for miRNA biomarker expression in cancer cells.