Determination of okadaic acid in scallop using microfluidic-based fluorescence polarization immunoassay

A microfluidic device-based fluorescence polarization immunoassay (FPIA) enabling rapid assay completion within 20-25 min was developed for the rapid screening of okadaic acid (OA) in shellfish. A fluorescent tracer was synthesized by conjugating OA to a fluorescent dye, and two anti-OA monoclonal antibodies (7E1 and 9G3) were evaluated to optimize assay performance. Binding activity tests revealed that the 9G3 antibody exhibited a lower dissociation constant and superior assay performance. Calibration curves were constructed, and the dynamic range and sensitivity of the assay were investigated, with particular emphasis on OA concentrations around the regulatory limit (0.16 mg/kg). The applicability of the developed FPIA to real samples was assessed through spike-recovery tests using scallop extracts. Although a slight decrease in sensitivity was observed due to the presence of methanol in the extracts, OA concentrations near the regulatory threshold could be reliably discriminated. These results demonstrate that the developed microfluidic FPIA provides a rapid and simple screening approach for determining whether OA concentrations in shellfish exceed established regulatory limits, thereby supporting routine monitoring and on-site analysis.