A surface plasmon resonance-based immunosensor for sensitive detection of bisphenol A

A method for the determination of bisphenol A (BPA), a representative endocrine-disrupting chemicals, was developed using a surfase plasmon resonance (SPR) sensor. BPA-ovalbumin (BPA-OVA) conjugate was immobilized on an Au thin film of the SPR sensor chip by physical adsorption, and BPA determinations were performed by an indirect competitive immunoassay, where a BPA sample containing an anti-BPA antibody is introduced into the SPR sensor system. The addition of BPA into the anti-BPA antibody solution (-0.8 mug/final, final concentration) was found to decrease the incidence angle shift sharply because of an inhibition effect of BPA. The RSDs (n=3) of each point were less than 4%. An evaluation of the affinity constant (K1) between anti-BPA antibody and BPA-OVA conjugate on the chip was found to be 2.26 X 10(6) M(-l) and that (K2) between anti-BPA-antibody and free BPA (analyte) was 5.72 X l0(4) M(-1). The lowest detection limit for BPA by SPR was almost the same as that by ELISA, 10(-9)g/ml (1 ppb).