Sensitive MicroRNA detection via single nanoparticle collision electrochemistry using DNA-functionalized silver...

MicroRNA (miRNA) quantification is pivotal for disease diagnostics and molecular mechanism studies, yet existing methods often suffer from limited sensitivity or complex workflows. Herein, we present a novel electrochemical sensor for miRNA-21 detection based on AgNP collision-oxidation and DSN-mediated signal amplification. The AgNPs are functionalized with target-specific ssDNA probes, which initially block electrode contact ("off" state). Upon miRNA-21 hybridization, DSN cleaves the duplex to expose AgNPs, enabling oxidation-induced current transient ("on" state) with signal frequency positively correlated with target miRNA concentration. The sensor achieved a limit of detection (LOD) of 0.011 fM and a linear detection range of 0.05 fM to 1000 fM, along with excellent specificity that enables effective distinction between the target miRNA and mismatched or non-complementary miRNA analogs. The sensor successfully detected miRNA-21 in spiked human serum (recovery: 96.7-112 %), demonstrating its promising clinical potential for liquid biopsy applications. Our work provides a simple yet powerful tool for low-abundance miRNA analysis in complex biological samples.