Novel shell/core particles for automated turbidimetric immunoassays

Recent innovations in particle design have led to the development of highly sensitive and reproducible immunoassay methods for the Du Pont aca discrete clinical analyzer. Key advances include the synthesis and use of particles less than 1 micron in diameter with high refractive index cores surrounded by thin, chemically reactive shells. The cores are prepared by emulsion polymerization to a well-defined size that depends on the choice of monomer and the requirements for turbidimetric signal. Methods for measuring therapeutic drugs (e.g., theophylline) involve particles with polystyrene cores; other methods require cores with higher refractive indices such as polyvinylnaphthalene. The shells are critical for overall method performance because they bind covalently the immunochemicals of interest. Polyglycidyl methacrylate shells have been used effectively to attach antigens and haptens to the particle surface.