Development of surface plasmon resonance immunosensor for the determination of methyl parathion

A surface plasmon resonance (SPR) sensor for the determination of methyl parathion (MP) was developed using an indirect competitive immunoassay. A, sensor chip was prepared by immobilizing a MP-BSA conjugate on a gold film on the sensor chip, followed by blocking with BSA to prevent the non-specific adsorption of MP and an anti-MP antibody onto the unmodified surface of the sensor chip. An evaluation of the adsorption equilibrium of MP-BSA onto the sensor chip by measuring the SPR angle shift revealed that the adsorption equilibrium was expressed by a Langmuir-type adsorption isotherm equation. The adsorption constant and the adsorbed amount of MP-BSA onto the sensor chip were found to be 5.0 X 10(5) M-1 and 0.95 ng/mm(2), respectively. An MP solution (1 similar to 5000 ppb) containing 60 ppm anti-MP antibody was introduced into the SPR sensor chip, and then the SPR angle shift was measured. The detection limit, defined as the angle shift of 85% for the blank, was found to be 10 ppb. The anti-MP antibody bound to the MP-BSA conjugate on the sensor chip was able to be dissociated by introducing an HCI-glycine solution (pH 2) into the sensor chip. Duplicate measurements with a single sensor chip were possible for at least 20 times.