A fluorescence and colorimetric dual-mode immunoassay for detection of ochratoxin A based on cerium nanoparticles

Ochratoxin A (OTA) is a widely distributed mycotoxin that seriously endangers food safety and human health. Therefore, establishing a sensitive and simple method for detecting OTA is crucial to ensure food safety. A fluorescence and colorimetric dual-mode immunoassay was established using cerium-based nanoparticles CPNs(Ⅳ) for detection of OTA. CPNs(IV) with good oxidase activity can catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to produce visible blue color signal. Under the catalysis of ALP, the ascorbic acid 2-phosphate (AA2P) was hydrolyzed to form ascorbic acid (AA), which reduced CPNs(Ⅳ) to CPNs(III). The produced CPNs(III) can emit significant fluorescence signal. Because the concentration of OTA was inversely proportional to the concentration of IgG-ALP in the microplate, the fluorescence signal was gradually decreased and the blue color signal gradually increased with the addition of OTA. The limits of detection (LODs) of this dual-mode immunoassay were 0.404 ng/mL (for fluorescent mode) and 0.962 ng/mL (for colorimetric mode). The recoveries of OTA were 97.60 %–103.55 % for the fluorescence mode and 99.12 %–102.60 % for the colorimetric mode in corn samples. These results indicated the dual-mode immunoassay was sensitive and reliable for detection of OTA in actual samples.