Sol particle decay protection immunoassay

Abstract

Disclosed is a method for determining the concentration of an analyte in a liquid test sample. The method involves the use of colloidal sized metal particles, which exhibit a spectral response in the agglomerated state which is detectably different than in their unagglomerated state, which bear specific binding partners for the analyte in question on their surface. The specific binding partner treated colloidal particles are combined in a buffered, aqueous medium with a destabilizer material capable of destabilizing the specific binding partner-colloidal particle conjugates thereby permitting the particles to agglomerate. Also included in the liquid medium is a polymer bearing multiple analyte or analyte analog molecules along its surface which serves to protect the specific binding partner coated metal particles from dissociation by the destabilizing agent. Analyte added to the medium, typically in the form of a fluid test sample, competes for the specific binding partner and thereby decreases the amount of protection afforded by the analyte or analyte analog bearing polymer which permits unprotected colloidal particles to agglomerate and provide a detectable spectral response. The magnitude of the change in spectral response is directly proportional to the concentration of analyte in the fluid test sample.