Construction of electrochemical flow immunoassay system using capillary columns and ferrocene conjugated immunoglobulin G for detection of human chorionic gonadotrophin

In this paper is reported a miniaturized flow immunoassay system. Ferrocene carboxylic acid (Fc) conjugated with anti-HCG immunoglobulin G (IgG) antibo dy (Fc-IgG) was prepared, and used as a novel analytical reagent. The syste m consists of the immunoreaction section, the capillary column packed with cation exchange resin, and the flow cell for electrochemical detection of F c-IgG. Antibody-antigen complexes were separated from their free conjugate on the basis of differences in isoelectric point (pl) using a cation exchan ge capillary column. The assay yielded a linear relationship between signal and HCG concentration in the range 0-2000 mIU/ml. This simple technique en ables the assay of HCG within 2 min. The cation exchange capillary column w as regenerated by occasional elution with malonate buffer (pH 6.0) containi ng 0.5 M NaCl, to remove free conjugate. Free conjugate recovered in this m anner could be reused up to eight times without significant decreases in th e sensitivity of the immunoassay. This electrochemical flow immunoassay req uires only minute quantities of serum and generates highly reproducible res ults. (C) 2001 Elsevier Science B.V. All rights reserved.