Microfabricated on-chip-type electrochemical flow immunoassay system for the detection of histamine released in whole blood samples

This paper describes an on-chip-type electrochemical flow immunoassay system with a multichanneled matrix column. The multichanneled matrix column was functionally coated with cation-exchange resin and used for separation of proteins. Antihistamine immunoglobulin G (IgG) antibody conjugated with ferrocenemonocarboxylic acid (Fc) was also prepared and used as a novel analytical reagent. Antibody-antigen complexes were separated from free Fc-conjugated IgG antibody (Fc-IgG) on the basis of differences in isoelectric point (pI) using the multichanneled matrix column coated with cation-exchange resin. The assay yields a good relationship between current and histamine concentration in the range of 200-2000 ng/ mL. This simple technique enables the assay of histamine released in whole blood within 2 min. Furthermore, a good correlation was found between the response of the electrochemical immunoassay described in this paper and the conventional RIA (radioimmunoassay). This on-chip-type electrochemical flow immunoassay requires only minute quantities of whole blood samples and generates highly reproducible results.