Portable detection of ochratoxin A in red wine based on a structure-switching aptamer using a personal glucometer

Abstract

Ochratoxin A (OTA) detection is important for food safety and public health because OTA is one of the most toxic and widespread mycotoxins. In this study, a portable aptasensor was developed for OTA quantification using a structure-switching aptamer and a commercially available personal glucometer (PGM), which is an affordable portable device for home or field use. The OTA aptamer was directly immobilized onto magnetic beads (MBs) through a facile streptavidin–biotin reaction. Invertase-labeled competitor DNA that was partly complementary to the aptamer was initially hybridized with the aptamer to form a competitor DNA–aptamer–MB complex. The addition of OTA triggered the structure-switching of the aptamer from the aptamer–competitor DNA duplex to the aptamer–OTA complex, thus releasing the competitor–invertase. The released competitor–invertase subsequently catalyzed sucrose hydrolysis to glucose, which was measured using a PGM. A higher OTA concentration led to higher competitor–invertase release and higher glucose concentration. The length and concentration of the competitor DNA were optimized to obtain the highest structure-switching activity of the aptamer on the MBs. This activity is essential to improve the detection performance of OTA aptasensors. The optimal pH for sucrose hydrolysis to glucose was also determined. Under optimal conditions, the detection limits in buffer and red wine were of 3.31 and 3.66 μg L⁻¹, respectively. This aptasensor also showed considerable selectivity to two other mycotoxins (aflatoxins B1 and B2). To the best of our knowledge, this paper was the first to report a portable aptasensor for OTA detection in real samples with the use of a PGM.