Mismatched catalytic hairpin assembly and ratiometric strategy for highly sensitive electrochemical detection of microRNA from tumor cells

Abstract

MicroRNAs (miRNAs) are regarded as promising biomarkers for the prognosis, diagnosis and treatment of different cancers. However, resulting from their low abundance, short length and high sequence similarity among family members, it is of major challenge to detect these miRNAs. On the basis of a mismatched catalytic hairpin assembly (CHA) amplification and ratiometric strategy, we constructed an electrochemical sensor for sensitively detecting miRNAs from tumor cells. The target miRNA can cyclically trigger the assembly of two hairpins with mismatched bases into many duplexes via CHA. Subsequently, these duplexes further associate with another hairpin assembled on the sensor surface to generate stable “Y”-shaped DNA complexes, which causes reverse current change for two electrochemical labels on the hairpins. It is found that the introduction of the mismatched bases in the hairpins for CHA can reduce the background noise to improve the signal to background ratio of the sensor, leading to a dynamic range of 5 fM–0.1 nM and a low detection limit of 1.1 fM for miRNA detection. Besides, the developed sensor can be employed to monitor and evaluate the expression levels of miRNAs in different tumor cells, demonstrating its potential real applications.