Ochratoxin A detection platform based on signal amplification by Exonuclease III and fluorescence quenching by gold nanoparticles

This study aimed to establish a detection platform for ochratoxin A (OTA), a common mycotoxin contaminant of various food products. The detection platform is based on signal amplification by Exonuclease III (Exo III) and fluorescence quenching by gold nanoparticles (AuNPs). The aptamer recognizes and binds to OTA, thus leading to the formation of duplex DNA between the complimentary DNA (cDNA) strand and the signal probe. Exo III then digests the duplex DNA from the 3′ blunt terminus of the signal probe to liberate the fluorophore and release cDNA. The released cDNA then hybridizes with other signal probes to initiate a new cleavage reaction. Through this cyclic hybridization-hydrolysis process, an OTA molecule can trigger the cleavage of a large quantity of signal probes. Upon the addition of AuNPs, the fluorophore cannot be adsorbed and quenched, thus notably amplifying fluorescence. The designed aptasensor is highly selective for OTA with a low limit of detection (4.82 nM). The feasibility of the detection procedure and the applicability of the aptasensor were validated through the detection of OTA in spiked red wine without interference from the sample matrix. Results indicated that the aptasensor could be used to verify the effectiveness of mycotoxin-control strategies.