Development of an immunosensor for the determination of rabbit IgG using streptavidin modified screen-printed carbon electrodes

Voltammetric enzyme immunosensors based on the employment of streptavidin modified screen-printed carbon electrodes (SPCEs) for the detection of rabbit IgG, as a model analyte, were described. Alkaline phosphatase (AP) and 3-indoxyl phosphate (3-1P) were used as the enzymatic label and substrate, respectively. The adsorption of streptavidin was performed by deposition of a drop of a streptavidin solution overnight at 4degreesC on the pre-oxidized surface of the SPCEs. The analytical characteristics of these sensors were evaluated using biotin conjugated to AP. The immunosensor devices were based on a specific reaction of rabbit l.-G with its biotinylated antibodies, which were immobilised on the modified screen-printed carbon electrodes through the streptavidin:biotin reaction. The immunosensors were used for a direct determination of AP labelled rabbit IgG, and for free rabbit IgG detection using sequential competitive immunoassay. A calibration curve in the range of 9 5 x 10(-11) to 1 x 10(-9) M of rabbit IgG was obtained with a estimated detection limit of 5 x 10(-11) M (7.0 ng/ml). These immunosensors were stable for 5 months if they were stored at 4degreesC. (C) 2004 Elsevier B.V. All rights reserved.