SPECIFIC ACTIVITY OF POLYPYRROLE NANOPARTICULATE IMMUNOREAGENTS - COMPARISON OF SURFACE-CHEMISTRY AND IMMOBILIZATION OPTIONS

Polypyrrole-based colloids with differing surface chemistries were com pared with respect to the specific activity of immobilized antibody. M onoclonal antibody to the alpha subunit of human chorionic gonadotropi n (hCG) was modified by incorporation of cystamine into the Fc-carbohy drate, followed by reduction with dithiothreitol resulting in the gene ration of 4.5 free thiols per IgG. The reduced IgG was added to clean, unmodified and surface-modified polypyrrole colloids. Functionalized colloids included carboxylate-modified polypyrrole, poly[pyrrole-co-1- (2-carboxyethyl) pyrrole]-silica composite, and amine forms of the car boxylated colloids. The amine-functionalized colloids were subsequentl y treated with sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-1-ca rboxylate to provide thiol-reactive maleimide surface groups. Followin g the conjugation of IgG to the colloids, bound and soluble antibody a ctivity was quantitated using a sequentially competitive immunoassay f or hCG, based on an automated commercial hCG kit. The results indicate d that all forms of polypyrrole retained the equivalence of between 12 and 33 mu g of IgG activity/mg of colloidal solids, relative to the u nmodified soluble IgG.