Disposable amperometric immunosensor system for rabbit IgG using a conducting polymer modified screen-printed electrode

A disposable and mediatorless immunosensor based on a conducting polymer (5,2':5'2-terthiophene-3'-carboxylic acid) coated screen-printed carbon electrode has been developed using a separation-free homogeneous technique for the detection of rabbit IgG as a model analyte. Horseradish peroxidase (HRP) and streptavidin were covalently bonded with the polymer on the electrode and biotinylated antibody was immobilized on the electrode surface using avidin-biotin coupling. This sensor was based on the competitive assay between free and labeled antigen for the available binding sites of antibody. Glucose oxidase was used as a label and in the presence of glucose, H2O2 formed by the analyte-enzyme conjugate was reduced by the enzyme channeling via HRP bonded on the electrode. The catalytic current was monitored amperometrically at -0.35 V vs. Ag/AgCl and this method showed a linear range of RIgG concentrations from 0.5 to 2 mug/ml with standard deviation +/-0.0145 (n = 4). Detection limit was determined to be 0.33 mug/ml. (C) 2003 Elsevier Science B.V. All rights reserved.