AUTOMATIC-APPARATUS FOR HETEROGENEOUS ENZYME IMMUNOASSAYS BASED ON ELECTROCATALYTIC DETECTION OF THE ENZYME AND ELECTROCHEMICAL REGENERATION OF THE SOLID-PHASE

A glassy carbon electrode, anodized for a short time at about 2.2 V vs. SCE, is a very convenient regenerable solid phase for the successive stages of an automated enzyme-linked immunosorbent assay. The anodized surface adsorbs the primary antibody and the blocking proteins in a similar manner to classical polystyrene solid phases; the detection of the immobilized glucose oxidase used as the label can be obtained from an electrocatalytic process occurring directly on the electrode; and the protein stacking, accumulated during the assay, can be eliminated by a simple re-anodization at the end of the cycle, allowing the adsorption of a new primary antibody. An automatic apparatus has been developed round an electrochemical flow cell fed with samples and reagents according to the principles of flow-injection analysis. Using rabbit IgG as analyte and glucose oxidase as label, series of 150 successive assays were conducted on the same electrode before it was polished again. The overall time of one assay, including the time for primary antibody adsorption and electrode regeneration, was 55 min.