Application of the Dimeric G-Quadruplex and toehold-mediated strand displacement reaction for fluorescence biosensing of ochratoxin A

Ochratoxin A (OTA) is one of the most toxic mycotoxins that exists in various agro-products and foods. Here, a non-label and enzyme-free fluorescence biosensor for highly specific detection of OTA has been developed by the combination of toehold-mediated strand displacement reaction (TMSD) and G-quadruplex dimer/ThT (G-dimer/ ThT). The DNA duplex (aptamer-IP) is composed of the anti-OTA aptamer and a single stranded initiation probe (IP). In the presence of OTA, the attachment of target to aptamer leads to the liberation of the IP, which activates the cycle TMSD amplifications of two hairpin probes (H-1 and H-2) accompanied by the production of numerous H-1-H-2 assemblies. This double-stranded H-1-H-2 structure results in the proximity between the 5'-end overhang tail of H-1 and the 3'-end stem of H-2 to liberate the pre-blocked G-dimer sequence for lighting up ThT. In addition, the method displayed a stable fluorescence emission in the high-salt media. It was successfully applied to analyze OTA in real food samples. Hence, the constructed fluorescence biosensing platform might provide a new way for OTA and other toxin analysis detection.

Automated summary

A new non-label and enzyme-free fluorescence biosensor for highly specific detection of OTA was developed using TMSD and G-dimer/ThT. The method successfully analyzed OTA in real food samples, offering a new way for OTA and other toxin analysis detection.