Construction of an electrochemical probe for on chip type flow immunoassay

Miniaturized immunosensors, that combine the analytical power of microfluidic devices with the high specificity of biomolecules, have been intensively studied for clinical analyses, environmental immunoassays and biochemical studies. Protein A has the ability to bind Fc-binding site of immunoglobulin G (IgG), and can be used as the detection probe in immunoassays. Ferrocenecarboaldehyde (Fc-CHO) was labeled to protein A as an electrochemical probe for on chip type amperometric flow immunoassay. When labeling Fc-CHO onto protein A via formation of Schiff-base and its reduction, mean number of nine Fc-CHO labeled to individual protein A molecules. Protein A labeled with Fc-CHO exhibited reversible redox properties of ferrocene in cyclic voltammograms and its peak currents increased with number of labeled ferrocenes. The current response of protein A labeled with Fc-CHO well correlated with its concentration when applying 390 V versus Ag/AgCl. Protein A labeled with Fc-CHO showed sufficient electrochemical properties that are useful in a miniaturized electrochemical immunoassays.