Magnetic nanobead-based immunoassay for the simultaneous detection of aflatoxin B1 and ochratoxin A using upconversion nanoparticles as multicolor labels

A novel and sensitive immunoassay for the simultaneous detection of aflatoxin B1 (AFB1) and ochratoxin A (OTA) in food samples was developed by using artificial antigen-modified magnetic nanoparticles (MNPs) as immunosensing probes and antibody functionalized upconversion nanoparticles (UCNPs) as signal probes. NaY0.78F4:Yb0.2, Tm0.02 and NaY0.28F4:Yb0.7,Er0.02 UCNPs were prepared and functionalized, respectively, with immobilized monoclonal anti-AFB1 antibodies and anti-OTA antibodies as signal probes. Based on a competitive immunoassay format, the detection limit for both AFB1 and OTA under optimal conditions was as low as 0.01 ng mL−1, and the effective detection range was from 0.01 to 10 ng mL−1. The proposed method was successfully applied to measure AFB1 and OTA in naturally contaminated maize samples and compared to a commercially available ELISA method. The high sensitivity and selectivity of this method is due to the magnetic separation and concentration effect of the MNPs, the high sensitivity of the UCNPs, and the different emission lines of Yb/Tm and Yb/Er doped NaYF4 UCNPs excited by 980 nm laser. Multicolor UCNPs have the potential to be used in other applications for detecting toxins in the field of food safety and other fields.