C. Fernandezsanchez et A. Costagarcia, ADSORPTION OF IMMUNOGLOBULIN-G ON CARBON-PASTE ELECTRODES AS A BASIS FOR THE DEVELOPMENT OF IMMUNOELECTROCHEMICAL DEVICES, Biosensors & bioelectronics, 12(5), 1997, pp. 403-413
The attachment of Immunoglobulin G (IgG) to a carbon paste electrode i
s investigated in this work. Studies of the immobilization of the immu
noglobulin on this electrode were carried out. Alkaline phosphatase (A
P) has been used as an enzyme label, linked to the antibody, for the d
etermination of the adsorbed immunoglobulin. Various substrates for th
is enzyme have been tested and alpha-naphthyl phosphate was found to b
e the best because of the lower oxidation potential of the enzymatic p
roduct, alpha-naphthol, and greater sensitivity under the same experim
ental conditions. An electrodic pretreatment based on an anodic oxidat
ion of the electrode surface in a phosphate media pH 9 was carried out
prior to the adsorption step. This activation is also suitable for th
e removal of the IgG layer and the regeneration of the electrodic surf
ace after each determination, with the intention of using the same ele
ctrode in the subsequent assays. A good reproducibility of the signal
was achieved in this way (Relative Standard Deviation, R.S.D. = 3.7%).
Using cyclic voltammetry, IgG labelled with AP has been quantified in
a range from 2x10(-12) to 7x10(-11) M and a detection limit of 2.3x10
(-12) M (signal-to-noise ratio = 3) was found. Finally, human IgG was
quantified under non-optimized conditions on the electrodic surface th
rough the reaction with AP labelled IgG using two different immunologi
cal designs. (C) 1997 Elsevier Science Limited.