Target “turn on” electrochemical pseudocapacitive sensor for ultrasensitive detection of microRNA-141

Abstract

In this study, an ultrasensitive electrochemical-detection system based on a target “turn-on” signal-enhancement pseudocapacitor was established for microRNA-141 (miRNA-141) detection. A three-dimensional porous film was constructed on the electrode surface in situ by chitosan, catechol and nanomaterials (gold nanoparticles and nitrogen-doped carbon nanotubes). When miRNA-141 hybridized with the probe on the electrode, ferrocene (Fc) was specifically introduced into the electrode surface, and then a pseudocapacitor containing Fc, ruthenium ion (Ru3+), catechol, and electrode formed (“turn on”). Fc and Ru3+ consumed in the electrode reaction can quickly recover to the original valence state on the surface of catechol/quinone and again participated in the electrode reaction. A "one to many" relationship existed between the target and the signal molecule Fc, which contributed to the improvement of the sensor sensitivity. The signal strength and stability of Fc improved and thus improved the sensitivity and stability of miRNA-141 detection. The concentration information of miRNA-141 was collected from the change in Fc signal strength. The linear detection range was 0.5 fM to 800 pM, and the detection limit can be calculated as 43.73 aM. This system overcame the problems of low reliability and weak signal of the traditional electroactive-ion labeling method, which relied on the change in electrostatic attraction/repulsion before and after probe–target hybridization.