Signal-enhanced ultrasensitive photoelectrochemical immunosensor for detecting Aflatoxin B1 based on phage-anti-immunocomplex peptide and PCN-224@MXene

As a carcinogenic mycotoxin, Aflatoxin B1 (AFB1) is widespread in grains. In particular, corn-derived feed and food are more heavily contaminated with AFB1 than other grain products, which pose severe risks to food safety and human health. Thus, developing rapid, sensitive, and accurate AFB1 detection methods is of great importance. In this study, a highly sensitive photoelectrochemical (PEC) immunosensor for detecting AFB1 based on phage-anti-immunocomplex peptide and the PCN-224@MXene composite was developed. The prepared phage-anti-immunocomplex peptide could bind to a large number of enzyme-labeled secondary antibodies, thereby greatly increasing the loading capacity of horseradish peroxidase (HRP). Moreover, the PCN-224@MXene showed wider light absorption range and narrower band gap, which is conducive to improving the photoelectric conversion efficiency. This resulted in the photocurrent intensities of PCN-224@MXene being 1.9-fold and 2.5-fold higher than those of PCN-224 and MXene, respectively. In addition, HRP catalyzed the oxidation of 4-Chloro-1-naphthol by H 2 O 2 to product an insulating precipitate, which hindered photo-induced electron transport, and thereby lead to a distinct photocurrent change. Using the multi-signal amplification strategy, the sensitivity of the PEC immunosensor for detecting AFB1 was significantly enhanced. Under the optimal detection conditions, the linear range was from 1 fg mL -1 to 100 ng mL -1 , and the detection limit was as low as 0.91 fg mL -1 (3σ/S). This LOD was considerably lower than the regulatory limit for AFB1 in corn. This method showed good selectivity, stability and reproducibility, and could be applied to the detection of AFB1 in corn samples.