Patent ID: 7829328

Claim:
An assay device for detecting an analyte in a test sample, the assay device comprising: a porous membrane that defines a detection zone, wherein a biological receptive material is immobilized within the detection zone; and detection probes that contain latex particles having an average size of from about 0.1 nanometer to about 100 microns, wherein the latex particles individually define a polymeric shell about a hollow interior constituting at least about 20% of the spatial volume occupied by the particle, wherein the polymeric shell of the latex particles comprises an organic polymer covalently conjugated with a specific binding member for the analyte, wherein the organic polymer is covalently conjugated with the specific binding member via a carboxylic functional group on the organic polymer, and wherein any remaining activated carboxylic functional groups on the organic polymer of the polymeric shell are blocked; wherein the detection probes are capable of generating a detection signal when present within the detection zone.