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 Cu²⁺. 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 Cu²⁺ and activating the Cu²⁺ 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^-1 OTA with a limit of detection of 0.01 ng mL^-1. 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.