In this study, a time-resolved fluorescence immunochromatographic assay (TRFICA) for detecting aflatoxin B₁ (AFB₁) and ochratoxin A (OTA) simultaneously was developed. Europium-based time-resolved fluorescent microspheres were used to label anti-AFB₁ monoclonal antibody and anti-OTA monoclonal antibody. Various factors such as pH for the activation of fluorescent microspheres, concentration of labeled antibodies, dosage of fluorescent probes, concentration of coating antigens for test line, concentration of goat anti-mouse IgG for quality control line, and sample pretreatment conditions were optimized. Under the optimal conditions, the assay showed half inhibition concentration (IC₅₀) values of 1.58 and 3.91 μg/kg , linear ranges of 0.26–9.73 and 1.14–13.29 μg/kg, and visible limits of detection (vLOD) of 3.70 and 5.55 μg/kg for AFB₁ and OTA, respectively. The cross-reactivity rates of this method with aflatoxin analogues and ochratoxin B were 12%–62% and 58%, respectively, without cross-reactivity with other mycotoxins. The recoveries of the two toxins spiked in corn samples were 92%–103%, with coefficients of variation (CV) less than 15%. The results of this method for real samples coincided with those of high performance liquid chromatography (HPLC) and commercial colloidal gold strip. The TRFICA strip was stored at 4 ℃ for more than 5 months with good stability. To sum up, this immunochromatographic strip is sensitive, accurate, rapid and easy to operate, and is very suitable for rapid screening of AFB₁ and OTA in food and agricultural products.

Heavy metals are highly toxic and can contaminate a wide range of foods. Their pollution and residues can bring about serious harm to food safety. Therefore, it is critical to strengthen efforts to detect heavy metal residues in food products. Immunoassay is promising for the rapid and efficient detection of heavy metals. Heavy metal antibodies are at the heart of immunoassays for the detection of heavy metals. Heavy metal antigens consist of two parts: heavy metal ions and chelating agents. Due to the structural similarity among metal ions and the universality of chelating agents, the resulting antibodies often show inadequate specificity, although antibodies with good specificity have been reported in some literatures. Therefore, it is significant to explore the specific recognition and interaction mechanism between heavy metal antibodies and antigens. In this article, we elaborate three research methods for understanding the recognition mechanism between heavy metal antibodies and antigens and recent progress in this area, and analyze the critical factors for the specific recognition and interaction. We hope that this review will provide a reference for enhancing the performance of heavy metal antibodies, and lay the foundation for establishing efficient, sensitive and specific methods for the detection of heavy metal residues in foods.