Sensitive detection of the okadaic acid marine toxin in shellfish by Au@Pt NPs/horseradish peroxidase dual catalysis immunoassay.

Based on the catalysis enhancement strategy of Au@Pt nanoparticles (Au@Pt NPs) and horseradish peroxidase (HRP) related to the TMB-HO indicator, a sensitive colorimetric immunoassay was established for trace okadaic acid (OA) detection. The anti-OA monoclonal antibody (McAb) with a high constant was prepared and modified on Au@Pt NPs. Through grafting the HRP conjugated goat anti-mouse IgG antibody (IgG) on Au@Pt/McAb, bifunctional composites with Au@Pt-Ab and HRP were prepared and adopted. Characteristics including morphology, specificity and catalytic performance were evaluated. Under the optimal conditions, the sensitivity of the resultant enzyme immunoassay was significantly improved, and a low limit of detection (LOD) of OA was achieved at 0.04 ng mL (equivalent to 0.6 μg kg in mussel tissue), which was better than that of most HRP or Au/HRP enzyme-linked immunosorbent assays. When applied to fortified shellfish samples ( oysters, mussels and clams), the recoveries ranging from 98.3 ± 2.3% to 106.0 ± 9.0% were acceptable and comparable with those of the LC-MS method. Acceptable precision was achieved with a variation coefficient (CV) of 2.3-8.4%. The method provides a promising alternative for the highly sensitive detection of the OA marine toxin at trace levels.