Renewable amperometric immunosensor for complement 3 (C-3) assay in human serum

A renewable electrochemical immunosensor has been developed for the determi nation of complement 3 (C-3) in human serum. It is based on a paraffin-grap hite-complement 3 antiserum biocomposite, which needs no additional curing. The analytical sample containing sought for C-3 was mixed with C-3 labeled with horseradish peroxidase (HRP) to form the incubation solution. A compe titive binding assay was realized by dipping the biocomposite immunosensor into the incubation mixture. After rinsing away the excess of HRP-C-3, the amount of HP,P fixed on the sensor surface was determined amperometrically, the current signal was inversely proportional to the amount of sought-for C-3 in the incubation mixture. Assay conditions were optimized including th e loading of C-3 antiserum in the biocomposite, the amount of labeled C-3 i n incubation solution, incubation time and temperature. Using o-aminophenol (o-AP) as a substrate, amperometric detection at - 150 mV (versus SCE) res ults in a linear range of 1.17-29.25 mug/ml. Serum samples were analyzed an d the results demonstrated that the concentration in this system meets the demands of clinical analysis. The surface of the immunosensor can be regene rated by simply polishing to obtain a fresh immunocomposite ready to be use d in a new competitive assay. (C) 2001 Elsevier Science B.V. All rights res erved.