Label-free impedimetric sensing platform for microRNA-21 based on ZrO 2 -reduced graphene oxide nanohybrids coupled with catalytic hairpin assembly amplification.

Herein, a sensitive electrochemical impedance sensor was constructed based on ZrO 2 -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 (Δ 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 Δ R et 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.