Ultrasensitive electrochemical detection of microRNA based on in-situ catalytic hairpin assembly actuated DNA tetrahedral interfacial probes.

Selective and sensitive detection of microRNA is crucial for early diagnosis and pathogenesis of disease. Here, we established a novel electrochemical biosensor for simple and accurate analysis of the tumor biomarker microRNA-141, which was based on in-situ catalytic hairpin assembly (CHA) actuated DNA tetrahedral (DTN) interfacial probes. Two hairpin structures used for CHA reaction were placed on the DTN, in which the hairpin H1 on the one vertex of DTN and hairpin H2 embedded in adjacent edge, respective. The target microRNA-141 could open the hairpin H1 and activated the in-situ CHA reaction between H1 and H2 to alter the conformational of DTN, increasing the chances of the direct interaction between methylene blue (MB) and the electrode surface, leading to an increase in the electrochemical signal. Meanwhile, the released miRNA-141 could unfold another H1, enabling the enzyme-free recycling of the target to obtain amplified electrochemical signals. Moreover, the in-situ catalytic hairpin assembly reaction on DTN could shorten the reaction time and enhance the sensitivity. The established biosensor exhibited a wide linear dynamic range of miRNA-141 from 1 fM to 100 pM with a detection limit of 0.32 fM. Besides, the approach can discriminate the target miRNA from mismatched ones with excellent selectivity and can be successfully applied in diluted serum samples, holding great potential for sensitive detection of various biomarkers clinically.