▎ 摘　　要

Herein, a sensitive electrochemical impedance sensor was constructed based on ZrO2-reduced graphene oxide (RGO)-modified electrode coupled with the catalytic hairpin assembly signal amplification strategy. Electrochemical impedance spectroscopy (EIS) was used to detect microRNA (miRNA) using the change in electron transfer resistance (Delta R-et) originated from nucleic acid hybridization on the electrode surface. MiRNA-21 was used as a model to verify this strategy. The results indicated that Delta R-et exhibited a good linear relationship with the concentration of miRNA-21 in the range from 1.0 x 10(-14) mol L-1 to 1.0 x 10(-10) mol L-1 with a detection limit of 4.3 x 10(-15) mol L-1 (S/N = 3). Additionally, this sensor exhibited good selectivity, and it could be applied to detect miRNA-21 in human serum samples and measure the expression levels of miRNA-21 in human breast cancer cell lines (MCF-7); thus, this sensor has great potential in cancer diagnosis.