Label-free aptasensor for ochratoxin A detection using SYBR Gold as a probe

A label-free sensing strategy employing aptamers, SYBR Gold, and exonuclease I (Exo I) for ochratoxin A (OTA) detection was designed. In the presence of target molecules (OTA), the conformation of the aptamer specific for OTA is switched from a random coil to an antiparallel G-quadruplex. Subsequently, Exo I is added into the mixture to digest the unfolded aptamers selectively, which are the preferred substrates of Exo I. Following the addition of SYBR Gold as probe, a strong fluorescence intensity is obtained. This aptasensor shows high selectivity toward OTA with a low limit of detection (16.5 nM). The validity of the procedure and applicability of the aptasensor are successfully assessed through the detection of OTA in spiked red wine and beer without interference from the sample matrix. Utilization of the proposed biosensor for quantitative determination of mycotoxins in food samples indicates its usefulness as a tool for verifying the effectiveness of mycotoxin control strategies.