Simultaneous Detection of Multiple Analytes Using Copalis Technology: A Reduction to Practice

Abstract

Coupled Particle Light Scattering (Copalis) is a homogeneous immunoassay technology that enables the simultaneous determination of multiple analytes in serum, plasma, or whole blood (1) . The Copalis system measures changes in light-scattering properties of particles when they form antibody-mediated complexes. The system can measure two types of events: polystyrene microparticle coagglutination and polystyrene-gold colloid microparticle coupling. In the first format, polystyrene microparticles are differentiated from their complexed aggregates as a function of antigen concentration or serological response. The second format measures the broadening of the microparticle light scatter histogram as gold particles are attached. In both cases, light scattering analysis is performed as particles flow singly through a finely focused laser beam. The ability to differentiate various sizes of polystyrene microparticles allows the system to measure multiple analytes or serological responses simultaneously. This capability has been demonstrated by the ToRC assay (toxoplasma, rubella, cytomegalovirus), in which antibodies to three different infectious agents are detected simultaneously (2) . In the present work, we demonstrate the application of Copalis technology to a variety of areas of diagnostic medicine in which the simultaneous measurement of multiple analytes or variables may be advantageous, including infectious disease, autoimmunity, and reproductive endocrinology. This format is useful for detecting the presence of antibodies to infectious agents or autoantigens, which are coated onto latex microparticles. By using only forward-scatter measurement, Copalis instrumentation …