Fast Amperometric Immunoassay Utilizing Highly Dispersed Electrode Material

Abstract

An immunoassay technique based on a high surface area carbon immunoelectrode is described. Dispersed ULTI carbon serves as a carrier for immobilized antibodies and also as an electrode material. ‘Sandwich’ scheme of immunoassay of rabbit IgG (as a model analyte) has been used. Iodine formed as a result of the enzymatic oxidation of iodide by peroxidase-label has been detected amperometrically. Using dispersed carbon material as a solid support for immobilization of immunoagents and as an electrode material improves the efficiency of immuno-interaction and the sensitivity of electrochemical assay due to the high area-to-volume ratio of solid to liquid phases. The method based on ‘sandwich’ immunoassay is conducted at 21°C. The time of each stage of incubation (with analyte and with peroxidase-antibody conjugate) is 10 min. Electrochemical detection of peroxidase-labeled immuno-complex does not exceed several minutes. The technique allows fast determination of rabbit IgG with a low detection limit, in the nanomolar range. By comparison, the conventional technique based on ELISA, being performed under the same conditions (temperature and incubation time) does not allow any quantitative determination of IgG for concentration lower then 100 nM.