Ultrasensitive fluorescence immunoassay for detection of ochratoxin A using catalase-mediated fluorescence quenching of CdTe QDs

Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H 2 O 2 )-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs). In this immunoassay, catalase (CAT) was labeled with OTA as a competitive antigen to connect the fluorescence signals of the QDs with the concentration of the target. Through the combinatorial use of H 2 O 2 -induced fluorescence quenching of CdTe QDs as a fluorescence signal output and the ultrahigh catalytic activity of CAT to H 2 O 2 , our proposed method could be used to perform a dynamic linear detection of OTA ranging from 0.05 pg mL −1 to 10 pg mL −1 . The half maximal inhibitory concentration was 0.53 pg mL −1 and the limit of detection was 0.05 pg mL −1 . These values were approximately 283- and 300-folds lower than those of horseradish peroxidase (HRP)-based conventional ELISA, respectively. The reported method is accurate, highly reproducible, and specific against other mycotoxins in agricultural products as well. In summary, the developed fluorescence immunoassay based on H 2 O 2 -induced fluorescence quenching of CdTe QDs can be used for the rapid and highly sensitive detection of mycotoxins or haptens in food safety monitoring. Herein, for the first time we report an improved competitive fluorescent enzyme linked immunosorbent assay (ELISA) for the ultrasensitive detection of ochratoxin A (OTA) by using hydrogen peroxide (H 2 O 2 )-induced fluorescence quenching of mercaptopropionic acid-modified CdTe quantum dots (QDs).