Investigating into a Ca2+-sensitive electrostatic self-assembly films to fabricate reproducible immunobeads for flow immunoassay

A novel strategy has been developed for fabricating reproducible bead-based flow immunoassay system by combining the merits of Ca2+-induced cross-linkage of sodium alginate with negative carboxyl groups of alginate. The sodium alginate was applied to modify the polyallyamine beads and render beads negative charge to immobilize antibodies via electrostatic/hydrogen bonding interaction between alginate and antibodies to realize the fabrication of immunobeads in buffer solution of 0.01 mol/l acetic-acetate (pH 7.5). The Ca2+-induced cross-linkage of alginate on the immunobeads can easily release antibodies from beads and regenerate a fresh alginate-modified beads for next fabrication of new immunobeads. The electrochemical flow immunoassay system based on the so-made immunobeads has been fabricated and the feasibility of the proposed strategy and qualities of so-fabricated flow immunoassay system was evaluated by applying to a competitive transferrin–transferrin antiserum immunoassay system.