Assay device and method

Abstract

An assay device and method are described. The assay may involve immobilizing a binding partner (e.g., an antigen or antibody) for an analyte to be detected (e.g., an antibody or antigen) on a portion of a surface of a microfluidic chamber; passing a fluid sample over the surface and allowing the analyte to bind to the binding partner; allowing a metal colloid, e.g., a gold-conjugated antibody, to associate with the bound analyte; flowing a metal solution, e.g., a silver solution, over the surface such as to form an opaque metallic layer; and detecting the presence of said metallic layer, e.g., by visual inspection or by measuring light transmission through the layer, conductivity or resistance of the layer, or metal concentration in the metal solution after flowing the metal solution over the surface.

What is claimed is: 
     
         1 . An assay, comprising:
 a microfluidic channel comprising a surface;   at least one of an antigen or an antibody disposed on a portion of the channel surface; and   an opaque layer associated with the portion of the surface.   
     
     
         2 . The assay of  claim 1 , wherein the layer is opaque at a wavelength for which the microfluidic channel is transparent. 
     
     
         3 . The assay of  claim 1 , wherein the opaque layer comprises a metal. 
     
     
         4 . The assay of  claim 1 , further comprising a layer including a metal colloid. 
     
     
         5 . The assay of  claim 1 , comprising a plurality of microfluidic channels. 
     
     
         6 . The assay of  claim 3 , wherein the metal comprises silver. 
     
     
         7 . The assay of  claim 4 , wherein the metal colloid comprises a gold-conjugated antibody. 
     
     
         8 . The assay of  claim 1 , wherein the opaque layer is a web or honeycomb of material that includes passages that allow light to be transmitted therethrough. 
     
     
         9 . The assay of  claim 1 , wherein the opaque layer is continuous. 
     
     
         10 . An assay, comprising:
 a microfluidic channel comprising a surface;   at least one of an antibody or an antigen associated with a portion of the microfluidic channel;   a metal colloid associated with an antibody or an antigen; and   a metal precursor.   
     
     
         11 . The assay of  claim 10 , wherein the metal precursor comprises a silver salt solution. 
     
     
         12 . The assay of  claim 11 , wherein the silver salt solution comprises silver nitrate. 
     
     
         13 . The assay of  claim 10 , wherein the metal colloid comprises gold. 
     
     
         14 . The assay of  claim 10 , wherein the metal colloid comprises a gold-conjugated antibody. 
     
     
         15 . The assay of  claim 10 , comprising a plurality of microfluidic channels. 
     
     
         16 . The assay of  claim 10 , comprising a microfluidic device, wherein the metal colloid and metal precursor are stored in the microfluidic device. 
     
     
         17 . The assay of  claim 10 , comprising a plurality of surfaces, wherein the plurality of surfaces includes at least a first surface including a first binding partner disposed across the first surface and a second surface including a second binding partner disposed across the second surface, and wherein the first and second surfaces are positioned in series with respect to one another. 
     
     
         18 . The assay of  claim 10 , wherein the microfluidic channel comprises at least one cross-sectional dimension of less than 100 microns. 
     
     
         19 . The assay of  claim 10 , further comprising a rinse solution.