Amperometmc immunoassays

When an electrode is placed in an electrolyte solution an electrical double layer is formed at the surface which functions electrically as a capacitor. An applied oscillating potential causes a certain current flow depending on the capacitance of this double layer. Carbon electrodes were prepared with immobilized antibodies (or antigens). When a specific antigen (or antibody) is added to the solutions, an antigen/antibody complex is formed at the electrode surface, which perturbs the electrical double layer and results in a current change. Dose-response curves can be obtained by measuring these current changes. Under the proper conditions this dose response is specific in the presence of non-specific proteins (e.g. serum). The method has been demonstrated, and dose-response curves obtained, for IgG, anti-IgG, anti-ferritin and S. Aureus cells. No labelled tag is required with this method.