DNA Triple Helix Complex-Functionalized Electrochemical Sensor for Sensitive Detection of MicroRNA in Human Serum

Abstract

The selective and sensitive monitoring of microRNAs (miRNAs) plays essential roles in cancer diagnosis. Herein, on the basis of DNA triple helix and toehold-mediated strand displacement reaction (TSDR), the construction of a simple electrochemical sensing system is reported for monitoring of let 7a in human serum. The triple helix complex probe (THCP) consisting of signal probe (MB-SP) labeled with methylene blue (MB) and capture probe (CP) is first assembled onto the sensing interface. The presence of target let 7a initiates the disassembly of THCP structure and conformational change of MB-SP. And the hairpin probe (HP) triggers the TSDR amplification and achieves the recycling of target let 7a, thus leading to massive MB-SP turning into molecular beacon structure, which causes the significantly amplified MB signal for monitoring of let 7a down to femtomolar level. In addition, taking advantage of TSDR signal amplification and the high selectivity of the THCP, the selective discrimination of let 7 miRNAs family members and circulating miRNAs detection in human serum are accomplished, which would supply a simple and sensitive monitoring approach for early clinical diagnostics.