Gold Nanoparticle-Impact Electrochemistry for MicroRNA Assays with Catalyzed Hairpin Assembly Amplification

We herein report a novel method for microRNA detection by exploring the nanoimpact electrochemistry (NIE) effect of DNA-modified gold nanoparticles (AuNPs). A target-catalyzed hairpin assembly reaction is designed prior to the single-particle electrochemical collision. Direct electro-oxidation of AuNPs is utilized as the signal source, which is initially inhibited by the capped hairpin structured DNA strands. In the presence of target microRNA, catalyzed hairpin assembly occurs, forming rigid three-way junction nanostructures. Since the hairpins are consumed, they can no longer block current transmission, and the AuNP-impact electrochemical signal is restored to reveal the concentration of microRNA. This NIE-based electrochemical biosensor is nontoxic, simple to operate, and exhibits high detection sensitivity and selectivity. It can be further utilized in the clinically relevant diagnosis.