Tyramine Signal Amplification on Polystyrene Microspheres for Highly Sensitive Quantification of Aflatoxin B1 in Peanut Samples

Aflatoxin B1 (AFB1) is the most toxic mycotoxin in contaminated food, which poses a serious threat to food safety and human health. Hence, a novel microparticle counting immunosensor was proposed for sensitive AFB1 detection mediated by polystyrene microspheres (PS) and tyramine signal amplification (TSA). Magnetic nanoparticles were used as immune carriers. Tyramine (Ty) molecules were decorated on the surface of PS (PS -Ty). In the presence of H2O2, horseradish peroxidase converted tyramine to a short-lived radical intermediate, thus forming stable covalent bonds between the immune carrier and PS-Ty. After magnetic separation, the coupled magnetic immune complexes act as the immune carrier to trigger changes in the number of unreacted PS-Ty. The proposed novel immunosensor was able to discriminate as low as 2 pg/mL of AFB1 and exhibited approximately a 13.8-fold increase in detection limit compared to the conventional enzyme-linked immuno-sorbent assay. Taking advantage of tyramine signal amplification and magnetic separation, the sensitivity of this sensor has been improved by 1-2 orders of magnitude. The TSA-based signal enhancement system significantly improved the performance of the immunosensor for trace detection of risk factors from complex food matrices.