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.