Highly sensitive detection of morphine by using immunosensor based on surface-plasmon-resonance

Highly sensitive and selective detection of morphine (MO) was realized by coupling an immunoreaction of an anti-MO monoclonal antibody and a surface-plasmon-resonance (SPR) phenomena. A normorphine-bovine serum albumin (NM-BSA) conjugate prepared as an antigen was immobilized on the Au thin film of sensor chip by physical adsorption. The incident angle of the SPR system using the NM-BSA immobilized chip increased almost linearly with increasing concentration of antibody up to ca. 5 μg/ml (ppm). The addition of MO into the antibody solution (5 ppm) was found to reduce the incident angle shift sharply because of the inhibition effect of MO. Based on this inhibiting principle, the present sensor could detect MO very sensitively in the concentration range of 0.1-10 ng/ml (ppb)