FAST AMPEROMETRIC IMMUNOASSAY UTILIZING HIGHLY DISPERSED ELECTRODE MATERIAL

An immunoassay technique based on a high surface area carbon immunoele ctrode is described. Dispersed ULTI carbon serves as a carrier for imm obilized antibodies and also as an electrode material. 'Sandwich' sche me of immunoassay of rabbit IgG (as a model analyte) has been used. Io dine formed as a result of the enzymatic oxidation of iodide by peroxi dase-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 immune-interaction an d the sensitivity of electrochemical assay due to the high area-to-vol ume ratio of solid to liquid phases. The method based on 'sandwich' im munoassay is conducted at 21 degrees C. The time of each stage of incu bation (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 com parison, the conventional technique based on ELISA, being performed un der the same conditions (temperature and incubation time) does not all ow any quantitative determination of IgG for concentration lower then 100 nM.