Development of a particle concentration fluorescence immunoassay for the quantitative determination of IgG in bovine milk

A rapid solid-phase particle concentration fluorescence immunoassay (PCFIA) was developed to quantitate the total IgG concentration in bovine milk. The assay is based on agglutination of antibody covalently bound to carboxyl-polystyrene particles with the antigen, which is in turn detected by a fluorescent labeled antibody by epifluorometry. Optimum assay performance was obtained using 0.25% w/v dilution of 0.8 micrometers carboxyl-polystyrene particles coated with 250 micrograms/mL of rabbit anti-bovine IgG at pH 4.5, two-step incubation of 30 and 20 min, respectively, and a 1.1000 dilution of the fluorescein isothiocyanate (FITC)-labeled rabbit anti-bovine IgG as the fluorescence signal. PCFIA is repeatable, and faster than most immunoassays