A copper monosulfide-nanoparticle-based fluorescent probe for the sensitive and specific detection of ochratoxin A.

The mycotoxin ochratoxin A (OTA) is a secondary metabolite derived from multiple Aspergillus and Penicillium strains. The development of a rapid, sensitive, and simple method for OTA detection is important to ensure food biosafety and safeguard public health. In this study, we designed a highly specific and sensitive assay for the detection of OTA using copper monosulfide (CuS) nanoparticles conjugated to an anti-OTA antibody (CuS-Ab NPs) and a fluorescent probe for Cu. When OTA is present in the solution, the OTA antigen, bound to the microplate, is competed off by the soluble OTA for binding to CuS-Ab NPs. After washing, the CuS-Ab NPs and bound OTA are removed. Subsequently, HCl is added to dissolve the CuS-Ab NPs bound to the OTA antigen, releasing Cu and activating the Cu fluorescent probe. Thus, the resultant fluorescence emission is inversely proportional to the OTA content in the solution. Under optimal conditions, this method detected 0.1-100 ng mL OTA with a limit of detection of 0.01 ng mL. The assay was tested using corn, soybean, and coffee samples, with recoveries ranging from 94% to 110%. This strategy provides a new approach for the detection of mycotoxins and other small-molecule analytes with broad application potential in food safety and quality control.