Saturation assay

Abstract

A modified form of saturation assay is provided that is based on the measurement of a free or unbound labelled reagent fraction (such that there is an increase in signal in the presence of analyte) and employs trapping zones to concentrate said unbound or free labelled faction to avoid loss of sensitivity. Preferably the assay is a membrane assay.

1 . A kit for performing a saturation assay for detection of an analyte in a sample, the kit comprising:
 a. a component for separating bound and unbound products of a competitive binding step; and   b. a secondary trapping zone   
     
     
         2 . A kit according to  claim 1 , further comprising a porous carrier. 
     
     
         3 . A kit according to  claim 1 , wherein the component for separating bound and unbound products of a competitive binding step comprises a primary trapping zone. 
     
     
         4 . A kit according to  claim 1 , further comprising a detectable moiety comprising at least one component selected from the group consisting of: microorganisms, cells, macromolecules, metal sol particles, beads, charcoals, kaolinites, bentonites, and latex beads. 
     
     
         5 . A kit according to  claim 4  wherein the detectable moiety comprises colloidal gold. 
     
     
         6 . A kit according to  claim 1 , wherein the saturation assay is an agglutination immunoassay and the primary trapping zone comprises a means for immobilizing an agglutinated fraction. 
     
     
         7 . A kit according to  claim 4 , wherein the detectable moiety is agglutinable. 
     
     
         8 . A kit according to  claim 6 , wherein the primary trapping zone comprises a capillary membrane of a pore size that excludes the agglutinated fraction. 
     
     
         9 . A kit according to  claim 1 , wherein the component for separating bound and unbound products of a competitive binding step comprises a capillary membrane of a pore size that allows chromatographic separation of bound and unbound products on the basis of particle size. 
     
     
         10 . A kit according to  claim 1 , wherein the secondary trapping zone comprises a component to immobilize and concentrate a free fraction of labelled analyte-binding reagent 
     
     
         11 . A kit according to  claim 10 , wherein the secondary trapping zone comprises a capillary membrane of a pore size that excludes unagglutinated labelled reagent. 
     
     
         12 . A kit according to  claim 11 , wherein the secondary trapping zone comprises an immobilized analyte-binding reagent or ligand or other cognate binding partner. 
     
     
         13 . A kit according to  claim 1 , further comprising:
 a. a hub to which two or more analyte-analogue moieties are bound; and   b. two or more labelled analyte-binding reagents capable of binding said analyte-analogue moieties.   
     
     
         14 . A kit according to  claim 1 , further comprising:
 a. a hub to which two or more analyte-binding reagents are bound; and   b. a signal particle comprising two or more analyte-analogue moieties capable of binding said analyte-binding reagents.   
     
     
         15 . A kit according to  claim 1 , further comprising at least one components selected from the group consisting of: buffers, application means, instructions, charts, desiccants, control samples, dyes, batteries, and signal processing/display means. 
     
     
         16 . A kit according to any of  claims 13 , wherein the pore size upstream of the primary trapping zone is sufficient to allow free movement of the hub, labelled reagent, sample and any agglutinate. 
     
     
         17 . A device for performing a saturation agglutination assay for detection of an analyte within a sample, the device comprising a carrier having a proximal end for receiving a sample, and a distal end toward which a sample may travel along the carrier, wherein the carrier comprises:
 a. a primary trapping zone comprising means which exclude an agglutinated fraction; and   b. a secondary trapping zone comprising a component which excludes a labelled reagent.   
     
     
         18 . A device according to  claim 17 , wherein the carrier is porous. 
     
     
         19 . A device according to  claim 18  wherein the primary and/or secondary trapping zones comprise a capillary membrane of a pore size that excludes an agglutinated fraction or labelled reagent, respectively. 
     
     
         20 . A kit comprising a device of  claim 17 .