Electrochemical Biosensor for MicroRNA Detection Based on Cascade Hybridization Chain Reaction

The development of effective strategies for sensitive and specific detection of microRNAs will facilitate clinical diagnostics. Here, we utilize cascade hybridization chain reaction as an enzyme-free isothermal amplified strategy, and construct label-free electrochemical biosensors for microRNAassay. MicroRNA initiated autonomous assembly of DNA nanostructures through the toehold-mediated strand displacement reaction. The assembly behavior was examined by gel electrophoresis and morphology of branched DNA nanostructure was verified by atomic force microscope. This cascade hybridization chain reaction leads to extended growth of DNA chains and higher amplification efficiency compared with the regular hybridization chain reaction. The performance of the sensors was characterized by electrochemical impedance spectroscopy, differential pulse voltammetry, and chronocoulometric analysis. The prepared biosensor exhibits high sensitivity and a lower detection limit of 11pM for the determination of microRNA-21. This electrochemical assay based on cascade hybridization chain reaction is specific and can distinguish between highly homologous targets such as fully complementary target microRNA-21, single, or two-base mismatched sequences and other family members. These findings open the possibility of using cascade hybridization chain reaction as possible amplified electrochemical sensing platforms.