Rapid quantitative detection of okadaic acid in shellfish using lanthanide-labelled fluorescent-nanoparticle immunochromatographic test strips

The accidental consumption of diarrhetic shellfish poisons can cause food poisoning. Okadaic acid (OA) is among the major diarrhetic shellfish poisons; however, current assays and techniques for OA detection have certain limitations. Therefore, in this study, a rapid and quantitative immunochromatographic assay for the detection of OA in shellfish was established using lanthanide fluorescent microspheres (LFM). Lanthanide fluorescent nanospheres were used to label OA monoclonal antibodies. Conjugates of antibodies and microspheres were pre-mixed with the sample for 5 min and then poured into the sample wells. After 15 min, the results were visualized under an ultraviolet lamp and quantified using a fluorescence strip reader. Under optimal conditions, the IC50 of the LFM test strip was 0.24 ng/mL, the visual limit of detection was 0.625 ng/mL, and the limit of detection values for mussels, oysters, and scallops were 0.97, 0.91, and 0.93 ng/g, respectively. The cross-reactivity with DTX1 was 51.23%; there was no cross-reactivity of the test strips with GTX2,3 or STX. The recoveries of OA in shellfish samples ranged from 87.14% to 99.57%, with a CV ≤ 7%. In both actual and simulated sample detection, the results obtained with the LFM test strips demonstrated a high correlation with the results obtained with the commercial ELISA kit. These findings demonstrate that the developed LFM test strip exhibits high accuracy and sensitivity, suggesting its suitability for rapid quantitative on-site detection of OA in seafood.