A catalytic hairpin assembly-based Forster resonance energy transfer sensor for ratiometric detection of ochratoxin A in food samples

Ochratoxin A (OTA) poses severe risks to the environment and human health, making the development of an accurate and sensitive analytical method for OTA detection essential. In this study, a catalytic hairpin assembly (CHA)-based Forster resonance energy transfer (FRET) aptasensor was developed to detect OTA using carbon quantum dots (CDs) and 6-carboxy-fluorescein (FAM) as dual signal readout. In the presence of OTA, the aptamer specifically interacted with OTA to release the helper DNA (HP), which could open the hairpin structure of FAM-labeled hairpin DNA 1 (H-1-FAM) modified on the surface of gold nanoparticles (AuNPs). CHA between H-1-FAM and hairpin H-2 labeled with CDs (H-2-CDs) can release HP for the next cycle, resulting in the occurrence of FRET with CDs as the energy donor and FAM as the energy acceptor. According to the ratio of F-CDs/F-FAM, the proposed aptasensor showed a wide linear range from 5.0 pg/mL to 3.0 ng/mL and a low detection limit of 1.5 pg/mL for OTA detection. Moreover, satisfactory results were obtained for OTA detection in rice, suggesting the potential application of this sensor in food safety analysis.