Adaptive Detection of Ochratoxin a with Extended Dynamic Range by Molecular-Clamp Modulated Aptamer Fluorescent Probes

Abstract

Aptamer-based detection methods typically suffer from fixed dynamic range that highly limits their practical application. Inspired by our previous work of modulating aptamer affinity through a mechanically coupled double-stranded (ds) DNA as a “molecular clamp”, we demonstrated the adaptive detection of ochratoxin A (OTA) with extended dynamic range by molecular-clamp modulated aptamer fluorescent probes. First, we show that the OTA aptamer affinity varied by two-fold when modulated by a ds molecular clamp with a length of Nd=18 bp. Then, it is found that the detection limit of the aptamer fluorescence probes constructed with molecular-clamp modulated OTA aptamers (MC-SAM) was about 16-fold lower than that of the fluorescence probes based on the unmodulated OTA aptamers (OTA-Apt) and thus the detection range of the aptamer fluorescent probes was extended to lower concentration by changing the OTA aptamer affinity. Moreover, the regulation through the molecular clamp did not affect the specificity of the OTA aptamer, and constructed fluorescent probes showed good selectivity for OTA. Finally, the OTA-Apt and MC-SAM fluorescent probes were practically applied to quantitative analysis of OTA in coffee samples within the two linear ranges, respectively.

Keywords: aptamer, molecular clamp, detection range, Ochratoxin A, Graphene oxide