Dual particle immunoassay method and kit

Abstract

A dual particle immunoassay method and kit for detecting analyte in a sample in which the sample to be analyzed, a binding molecule specific for the analyte, and a particle coated with the analyte to be detected or coated with a second binding molecule are reacted and applied to a porous membrane. The competitive immunoassay utilizes an analyte-coated particle, whereas the sandwich immunoassay employs a second binding molecule-coated particle. All of the reagents except for the coated particle are able to pass through the porous membrane. Detectable particles coated with a binding substance that binds to the binding molecule, such as protein A protein G, second antibody reactive to the binding molecule, or a small synthetic affinity ligand, are reacted with coated particles retained on the membrane surface. The detectable particles will pass through the membrane if not complexed with the coated particle. In the competitive immunoassay, detectable particles bind to binding molecules that complex with the analyte-coated particles in the absence of analyte and are detected. In the sandwich immunoassay, detectable particles bind to binding molecules that are attached to the coated particle in the presence of analyte and are detected.