SPR immunosensor for the detection of okadaic acid in mussels using magnetic particles as antibody carriers

Protein G-coated magnetic particles (MPs) were used as immobilisation supports for an antibody against okadaic acid (MAbOA) and carriers into a surface plasmon resonance (SPR) device for the development of a direct competitive immunosensor for okadaic acid (OA). SPR analysis of MAbOA–MP conjugates demonstrated that conjugations were successful with complete immobilisation of all the antibody biomolecules onto the MPs. Moreover, MAbOA–MP conjugates provided up to 11-fold higher SPR signals, compared to free MAbOA. The use of conjugates in the direct competition assay provided a 3-fold lower LOD μg/L (2.6 μg of OA/L, equivalent to 12 μg of OA/kg mussel meat). The presence of mussel matrix did not interfere in the OA quantification as seen in the calibration curves. Mussel samples, obtained from Ebro Deltaʹs bays (NW Mediterranean) during a diarrheic shellfish poisoning (DSP) event and in the presence of Dinophysis sacculus, an OA producer, in the shellfish production area, were analysed with the MP-based SPR immunosensor. The OA contents correlated with those obtained by liquid chromatography–tandem mass spectrometry (LC–MS/MS) (y = 0.984x − 5.273, R2 = 0.789, p < 0.001) and by mouse bioassay (MBA).