Highly Sensitive Electrochemical Sensor for an miR-200c Assay Based on Ligation-Assisted DNA Strand Displacements

Abstract

miRNAs are emerging as powerful biomarkers, which can be used for pointing out various pathological processes of human beings. For example, miR-200c is a critical signature of prostate cancer. Nevertheless, classic approaches for an miRNA assay still suffer certain limitations. Herein, we have established a highly sensitive miR-200c biosensor utilizing electrochemical techniques. A smart sensing strategy is designed focusing on ligation-dependent cascade strand displacement amplification (CSDA). Target miR-200c is able to link two DNA probes aided by the T4 DNA ligase. The as-formed DNA hybrid is then applied for cyclic strand displacement polymerization and nicking cleavage processes in the solution. Subsequently, the generated product is able to trigger downstream SDA at the electrode interface. The combined procedure helps recruit a large number of DNA probes labeled with electrochemical species. The recorded electrochemical signal is positively related to the initial miR-200c level. Under optimal conditions, the as-prepared biosensor achieves a high sensitivity. The limit of detection (LOD) is estimated to be as low as 3.3 aM. Moreover, it successfully discriminates the target miRNA from mismatched miRNAs and performs satisfactorily in biological samples. The working electrode can be easily regenerated for additional tests by heating and annealing processes. This work offers a facile, reliable, and highly sensitive way to sense miRNAs for potential applications.