The electrochemistry of antibody-modified conducting polymer electrodes

The modification of conducting polymer electrodes with antibodies (i.e. pro teins) by means of electrochemical polymerization is a simple step that can be used to develop an immunological sensor. However, the electrochemical p rocesses involved leading to the generation of analytical signals by the se nsor have not been fully investigated. In this work, we report on the chara cterization of the interaction between an antigen, human serum albumin (HSA ) and an antibody-immobilized polypyrrole electrode (such as anti-HSA) usin g cyclic voltammetry (CV) and impedance spectroscopy. This interaction was monitored using electrochemical impedance spectroscopy at three different p otentials. The potentials correspond to the three redox states of the elect roconducting polymer (i.e. reduced, doped and overoxidized states). Evidenc e from the CV experiments confirmed that there was a shift in the potential , which was found to be proportional to the concentration. Both the CV and the impedance experiments indicated that this potential-dependent shift cou ld be attributed to antibody-antigen (Ab-Ag) binding. (C) 1999 Elsevier Sci ence S.A. All rights reserved.