Sensitive detection of Ochratoxin A in food and drinks using metal-enhanced fluorescence

Easy, sensitive, rapid and low cost ochratoxin biosensors are strongly demanded in food analysis since Ochratoxin A (OTA) is a widely diffused food contaminant, highly detrimental for human health. In this work, a novel plasmonic based optical biosensor prototype for ochratoxin A is described. It exploits the metal-enhanced fluorescence phenomenon due to the silver film over nanosphere plasmonic substrate. Since ochratoxin A could be present in different food commodities, sensor performances have been tested on three different matrices (dried milk, juices, and wheat mix). Firstly, a common OTA extraction solvent and a labeling and detection protocol were defined for the analyzed matrices. Then, the efficiency of the Ag-FON surfaces in signal amplification for the detection of low ochratoxin A concentrations was defined. Using samples spiked with OTA-AF 647 or with unlabeled OTA we were able to detect the mycotoxin at concentrations lower than E.U. specifications of 0.5 μg/kg in wheat, milk and apple juice. The test performances are comparable to those of ELISA kits but the platform presented here, once optimized, present some perspective advantages, such as: low cost and time consuming, versatility of the protocol for the investigation of different matrices, employment also in non-qualified laboratories, small dimensions that allow its integration in a compact device for OTA on-site detection.