An electrochemical microRNA sensing platform based on tungsten diselenide nanosheets and competitive RNA–RNA hybridization

In this work, we report an ultrasensitive electrochemical biosensor for microRNA-21 (miRNA-21) detection by using a competitive RNA–RNA hybridization configuration. A biotinylated miRNA of the self-same sequence with the target miRNA is mixed with the samples, and allowed competition with the target miRNA for a thiolated RNA probe immobilized onto a tungsten diselenide (WSe2) nanosheet modified electrode. Thereafter the current response is obtained by forming the hybridized biotinylated miRNA with streptavidin–horseradish peroxidase (HRP) conjugates to catalyze the H2O2 + hydroquinone (HQ) system. Benefiting from the high specific surface area of WSe2 nanosheets, the competitive hybridization configuration and the signal amplification of the H2O2 + HQ detection system, the proposed assay exhibits a wide linear range of 0.0001–100 pM towards target miRNA with a detection limit of 0.06 fM (S/N = 3), and shows excellent discrimination ability for base-mismatched miRNA sequences. Therefore, the designed platform has promising prospects for the detection of miRNA in biomedical research and early clinical diagnosis.