LAUSR

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 (ΔRet) originated from nucleic acid hybridization on the electrode surface. MiRNA-21 was used as a model to verify this strategy. The results indicated that ΔRet exhibited a good linear relationship with the concentration of miRNA-21 in the range from 1.0 × 10−14 mol L−1 to 1.0 × 10−10 mol L−1 with a detection limit of 4.3 × 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.