Biocatalyzed deposition amplification for detection of aflatoxin B1 based on quartz crystal microbalance

An ultrasensitive piezoelectric method for the detection of the aflatoxin B1 (AFB1) based on the indirect competitive immunoassay and the biocatalyzed deposition amplification has been developed. In this method, the quartz crystal surface was coated with a self-assembled monolayer of 3-mercaptopropionic acid (MPA) for covalently immobilization of the BSA-AFB1 conjugate, which could compete with the free AFB1 for binding to the anti-AFB1 antibody (MsIgG). After the competitive immunoreaction, the horseradish peroxidase (HRP) labeled goat anti-mouse IgG (G-Anti-MsIgG) was introduced into the detection cell to combine with the anti-AFB1 antibody on the crystal surface. The enzyme labeled G-Anti-MsIgG as a biocatalyst could accelerate the oxidation of 4-chloro-1-naphthol by H2O2 to yield the insoluble product benzo-4-chlorohexadienone on the surface of quartz crystal microbalance (QCM), resulting in a mass increase that was reflected by a decrease in the resonance frequency of the QCM. The proposed approach could allow for the determination of AFB1 in the concentration range of 0.01–10.0 ng mL−1. Furthermore, several artificially contaminated milk samples were analyzed with good recoveries obtained, which demonstrated the suitability of the proposed method for detecting AFB1.