Cerium ions triggered dual-readout immunoassay based on aggregation induced emission effect and 3,3′,5,5′-tetramethylbenzidine for fluorescent and colorimetric detection of ochratoxin A

Ochratoxin A (OTA) is one of the most prevalent and toxic mycotoxins. Ultrasensitive and convenient detection of OTA is urgent demanded for public health. In this work, a dual-readout immunoassay was established for the detection of OTA based on Ce4+ oxidizing 3,3',5,5'-tetramethylbenzidine (TMB) and Ce3+ inducing aggregation induced emission (AIE) of Au nanoclusters (AuNCs). Under alkaline phosphatase (ALP), the ascorbic acid 2-phosphate (AA2P) can form ascorbic acid (AA) by dephosphorylation. The AA can reduce Ce4+ to generate Ce3+, which induced the AIE of AuNCs to enhance the fluorescence intensity of AuNCs. Meanwhile, unreacted Ce4+ oxidized TMB to form blue oxTMB. Thus, a dual-readout immunoassay was developed based on AIE of AuNCs and TMB as substrate. The limits of detection (LODs) were as low as 0.62 ng/mL for fluorescent assay and 0.81 ng/mL for colorimetric assay. The recoveries of OTA from corn were 94.4%-107.7% for the fluorescent mode and 93.7%-106.9% for the colorimetric mode. The results verified that the cerium ions triggered dual-readout immunoassay was reliable to sensitive detect OTA in corn samples.