Dual-mode immunoassay for sensitive detection of ochratoxin a based on PP(Fe)@HRP probe with high catalytic activity

Ochratoxin A (OTA) is a mycotoxin with carcinogenic properties. Thus, it is essential to establish a sensitive method for detecting OTA. In this work, a colorimetric and fluorescence dual-mode OTA immunoassay was established based on PP(Fe)@HRP probe. The PP(Fe)@HRP probe consists of PCN-224(Fe), PtNPs and HRP, all of which possess peroxidase activity. When combined to form PP(Fe)@HRP, the peroxidase activity increased significantly. Then, the new probe was used to oxidize TMB to generate blue signal. Meanwhile, the TMB oxidation product (oxTMB) effectively quenched the fluorescence of GSH-AuNCs to generate fluorescence signal. By modifying antibody onto this probe, linking them to the target OTA, an ultra-sensitive dual-mode OTA immunoassay was achieved. This immunoassay demonstrated excellent sensitivity. The limit of detection (LOD) of colorimetric mode was 0.09 ng/mL, and the LOD of fluorescence mode was 0.02 ng/mL. Besides, the immunoassay had high specificity toward OTA and satisfactory recovery rate in corn samples.