Synergistic Effects of DNA Structure for Ultrasensitive Detecting OTA in Grains

Ochratoxin A (OTA) is considered as one of the most hazardous mycotoxins commonly occurring in grains. Thus, the monitoring of OTA is extremely significant. Herein, a synergistic strategy to detect OTA in grains based on the combination of DNA tetrahedron-structured aptamer (DTA) and hybridization chain reaction (HCR) was proposed. Briefly, DTA was assembled on the gold electrode. In the presence of OTA, the trigger DNA on the top of the DTA was exposed to unfold the biotin-modified hairpin structure DNA to HCR. It could conjugate plentiful streptavidin-labeled horseradish peroxidase (SA-HRP) to form polyaniline (PANI), which was regarded as electrochemical active molecule to detect OTA. In this way, the synergistic effect of DTA and HCR not only can provide stable probe structure to improve the recognition rate of OTA, but also can supply a large number of templates to synthesize PANI under mild conditions. As a result, the biosensor has a good analytical performance for OTA in a linear range of 0.05 to 50 ng mL −1 , with a detection limit of 0.017 ng mL −1 . The accuracy of sensor is similar with high-performance liquid chromatography (HPLC) analysis.