Competitive fluorescent immunosensor based on FRET between core-shell graphene quantum dots and Au nanoparticles for ultra-sensitive detection of ochratoxin A

Ochratoxin A (OTA) is a kind of mycotoxin, and developing a sensitive and simple method to detect OTA is of great significance for ensuring food safety and human health. In this study, a competitive fluorescent immunosensor based on fluorescence resonance energy transfer (FRET) was designed for the ultra-sensitive detection of OTA. Here, Ag@SiO2 @N, S-GQDs nanocomposites were successfully designed, fabricated, and characterized by heteroatom co-doping and metal enhanced fluorescence (MEF) techniques, which can improve the fluorescence intensity and quantum yield. This study indicated that FRET between OTA antigen-modified Ag@SiO2 @N, S-GQDs (Ag@SiO2 @N, S-GQDs-OTA-Antigen) and OTA antibody-modified AuNPs can effectively quench the strong fluorescence of Ag@SiO2 @N, S-GQDs-OTA-Antigen. The competitive fluorescent immunosensor based on FRET can detect OTA with a linear range of 0.5–1000 pg/mL and a limit of detection (LOD) of 0.094 pg/mL under optimal conditions. The recoveries ranged from 94% to 110% for the red wine sample, suggesting that the developed FRET-based competitive fluorescent immunosensor can be an effective tool for the ultra-sensitive detection of OTA, meanwhile, it might provide a better method for the detection of other toxic small molecules in food and the environment.