Probing direct binding affinity in electrochemical antibody-based sensors

Antibodies (Ab) are commonly used in the development of biosensors for large molecules. Their effectiveness in the direct analysis of small analyte at low concentrations can be compromised by the mode of Ab immobilization to solid substrates. The association of atrazine with anti-atrazine IgG monoclonal antibodies bound to gold-deposited quartz-crystal (GQC) and indium-doped tin oxide (ITO) electrode surfaces was characterized by electrochemical impedance spectroscopy (EIS) as a function of immobilization chemistry. Relative differences in the capacitance of unmodified and antibody modified gold electrode surfaces varied inversely with the degree of surface roughness as determined by atomic force microscopy (AFM). In addition, the surface resistance and capacitance elements measured at antibody modified GQC and ITO-electrodes were shown to reflect anti body-antigen binding. (C) 2003 Published by Elsevier B.V.