Cu2-xSe@Bi2MoO6 nanozyme-based immunoassay for the colorimetric detection of walnut allergen in foods

In the present study, we developed a nanozyme-based direct competitive immunoassay to detect walnut allergen (Jug r 4) in foods. Walnut monoclonal antibody (mAb) and Cu 2− x Se@Bi 2 MoO 6 nanocomposites were generated to form a signal probe by electrostatic adsorption. The nanocomposites had high peroxidase-like activity and could be stored at room temperature. The linear range of the optimized assay was 137.35 ± 0.14 to 3526.0 ± 4.53 μg/L with a limit of detection of 81.63 ± 0.89 μg/L. This method was validated by detecting walnut protein in bread, biscuits, and milk samples, providing recovery rates of 70.63–127.04 %. The fast and sensitive assay was suitable for the rapid detection of walnut allergen in foods.