Robust and sensitive methods for the detection of
microRNAs (
miRNAs) are crucial in the clinical diagnosis of
cancers. In this study, a novel electrochemical biosensor with high sensitivity for miRNA-21 detection is developed, which relies on the formation of a
peptide nucleic acid (PNA)-
DNA hetero-three-way junction (H3WJ) and target-recycling catalytic hairpin assembly (CHA) amplification. The electroneutral PNA probes are initially immobilized onto a
gold electrode to construct the sensor. Upon introduction of miRNA-21, target-recycling CHA is initiated, resulting in abundant double-stranded CHA products. Subsequently, association between the PNA probes and these products leads to the formation of PNA-
DNA H3WJs. Consequently, the
electrode surface is densely populated with numerous electroactive
Ferrocene (Fc) groups, resulting in a significantly amplified current response for highly sensitive detection of miRNA-21 at concentrations as low as 0.15 fM. This approach demonstrates remarkable specificity towards target
miRNAs and can be utilized for quantitative monitoring of miRNA-21 expression in human
cancer cells. More importantly, the sensor exhibits exceptional stability and shows a significant reduction in background noise during
miRNA detection, making this method a highly promising sensing platform for monitoring various
miRNA biomarkers to facilitate the diagnosis of diverse
cancers.