Dual-mode biosensor for femtomolar miRNA-155 detection by electrochemiluminescence and adsorptive stripping voltammetry

Herein, a dual-mode electrochemical biosensor for the detection of femtomolar miRNA-155 is developed based on electrochemiluminescence (ECL) and adsorptive stripping voltammetry (AdsSV). The capture unit is tetrahedron DNA, and the signal unit is g-C3N4@AgNPs-rDNA. When target miRNA-155 is present, a complex capture unit-miRNA-155-signal unit is formed through DNA/RNA hybridization, which is immobilized on the electrode surface in a special adsorption state. Numerous silver nanoparticles (AgNPs) improve the electric conductivity of graphitic carbon nitride (g-C3N4) which thus then generate strong and stable ECL signals. In addition, AgNPs would be stripped to generate electrochemical signals itself. So, a sensitive ECL/AdsSV dual-mode detection is obtained. Both the ECL intensity and the AdsSV stripping peak current have linear relationships with miRNA-155 concentration, with limits of quantitation (LOQs) of 50 fM and 100 fM respectively. High selectivity, good reproducibility and long-term stability are also gained. Furthermore, the signals of ECL and AdsSV could verify each other, providing an insurance for the accuracy and reliability of the testing results. Thence, a practical detection plateau for rapid, simple, selective and reliable detection of miRNAs is provided.