Nanobody-based and aggregate quantum microspheres-integrated fluorescence immunochromatographic test strip for highly sensitive detection of aflatoxin B.

Aflatoxin B (AFB) is a highly toxic and potent carcinogenic mycotoxin that poses a significant threat to food safety. Conventional immunochromatographic test strips (ICTS) often exhibit insufficient specificity and sensitivity. To address these limitations, a novel fluorescent ICTS (AQMs@G8-ICTS) was developed by integrating aggregated quantum microspheres (AQMs) with the high-affinity nanobody G8. Initially, the G8 nanobody was successfully expressed and purified, and its binding activity was validated using enzyme-linked immunosorbent assay (ELISA). The fluorescent signal probe was constructed by coupling the G8 nanobody to AQMs via electrostatic adsorption. Under optimized conditions, the AQMs@G8-ICTS exhibited a limit of detection (LOD) of 0.03 ng/mL, with a total detection time of only 8 min, making it highly suitable for rapid on-site analysis. This method also demonstrated excellent specificity and methanol tolerance. In spiked corn samples, recoveries ranged from 99.6 % to 112.1 %, with relative standard deviations (RSD) from 1.3 % to 4.1 %. Notably, the AQMs@G8-ICTS demonstrated a significant improvement in sensitivity, achieving a LOD that is approximately tenfold lower than that of the conventional gold nanoparticle-based ICTS (AuNPs@G8-ICTS). These results demonstrate that this design enables accurate and precise real-time detection of AFB in corn. Furthermore, it establishes a valuable reference for developing sensitive and rapid immunoassays.