Ultrasensitive quantification of aflatoxin B1 via nanobody phage -mediated quantitative PCR and digital PCR for agro-products

Phage display-mediated immuno-polymerase chain reaction (PD-IPCR) combines the strengths of phage display technology and immuno-PCR. The link between genotype and phenotype has been established by displaying antibody fragments on the surface of phage particles, allowing signal transmission. In this study, we utilized aflatoxin B₁ (AFB₁) as a model system to investigate the efficacy of PD-IPCR. Signal amplification was achieved using both real-time fluorescence quantitative PCR (qPCR) and a custom-made droplet digital PCR (dPCR) system. Under optimized conditions, the assay using dPCR achieved a limit of detection of 0.015 ng/mL, a 6-fold improvement over qPCR. The validation of our method using major agricultural produce, such as corn, flour, and soy sauce, shows excellent recoveries ranging from 85.77 % to 108.28 %, with a total assay time of less than 2 h. Furthermore, we compared our results with a high-performance liquid chromatography (HPLC) method for AFB₁ content in corn and flour, revealing consistent outcomes (r = 0.9847). These results demonstrate the potential of nanobody-based PD-IPCR as a reliable tool for detecting mycotoxins.