A surface plasmon resonance-based immunosensor for highly sensitive detection of morphine

Highly sensitive and selective detection of morphine (MO) based on surface-plasmon-resonance (SPR) was realized by using an anti-MO monoclonal antibody and MO-bovine serum albumin (MO-BSA) conjugate (antigen). MO-BSA was immobilized on the Au thin film of the SPR sensor chip by physical adsorption. The incident angle of the SPR system using the MO-BSA immobilized chip increased almost linearly with increasing concentration of antibody up to ca. 5 mu g ml(-1) (ppm). The addition of MO to 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 in the concentration range 0.1-10 ng ml(-1) (ppb). The affinity constants between the antibody and the antigens (MO and MO-BSA) could be obtained by assuming a Langmuir adsorption model for the immunoreaction system. (C) 1998 Elsevier Science S.A. All rights reserved.