Assay

Abstract

The present invention provides an assay kit for detecting an analyte of interest in a sample. The kit comprises a) a reporter species; b) a labelled species having first and second binding regions, wherein the first binding region is capable of binding to the analyte of interest and the second binding region is capable of binding to the reporter species; c) an immobilised species capable of binding to the first binding region of the labelled species; and d) immobilised capture reagent capable of binding to the reporter species. The arrangement is such that the sample is contacted with the labelled species, is then contacted with the immobilised species and is subsequently contacted with the immobilised capture reagent, the reporter species being added prior to exposure of the sample to the immobilised capture reagent. If no analyte is present in the sample, the labelled species becomes bound to the immobilised species and is therefore unable to bind to the immobilised capture reagent. If analyte is present in the sample, the analyte binds to the labelled species such that the labelled species is unable to bind to the immobilised species but can bind to the immobilised capture reagent via the reporter species, the presence of the analyte thus being determined by the presence of labelled species bound to the immobilised capture reagent via the reporter species.

1 . An assay kit for detecting an analyte of interest in a sample, comprising:
 a) a reporter species;   b) a labelled species having first and second binding regions, wherein the first binding region is capable of binding to the analyte of interest and the second binding region is capable of binding to the reporter species;   c) an immobilised species capable of binding to the first binding region of the labelled species; and   d) immobilised capture reagent capable of binding to the reporter species,   the arrangement being such that the sample is contacted with the labelled species, is then contacted with the immobilised species and is subsequently contacted with the immobilised capture reagent, the reporter species being added prior to exposure of the sample to the immobilised capture reagent,   wherein if no analyte is present in the sample, the labelled species becomes bound to the immobilised species and is therefore unable to bind to the immobilised capture reagent, and wherein, if analyte is present in the sample, the analyte binds to the labelled species such that the labelled species is unable to bind to the immobilised species but can bind to the immobilised capture reagent via the reporter species, the presence of the analyte thus being determined by the presence of labelled species bound to the immobilised capture reagent via the reporter species.   
     
     
         2 . An assay kit according to  claim 1 , wherein the immobilised species is provided in a trapping zone and the immobilised capture reagent is provided in a separate detection zone, the sample moving from the trapping zone to the detection zone. 
     
     
         3 . An assay kit according to  claim 2 , wherein the labelled species is provided in a reagent zone situated upstream of the trapping zone, and wherein in use the labelled species is mobilized in the sample when the sample contacts the reagent zone and be able to bind to the analyte of interest (if present) in the sample and further be able to move to the trapping zone and subsequently to the detection zone. 
     
     
         4 . An assay kit according to  claim 2  or  claim 3 , wherein the reporter species is provided at or upstream from the trapping zone. 
     
     
         5 . A lateral flow carrier immunoassay device for the detection of an analyte of interest in a sample, comprising:
 a) A mobilisable reporter species;   b) A reagent zone having a mobilisable labelled species having first and second binding regions, wherein the first binding region is specific to the analyte of interest and the second binding region is specific to the reporter species;   c) A trapping zone situated at or downstream of the reagent zone comprising an immobilised analyte of interest and;   d) A detection zone situated downstream of the trapping zone comprising an immobilised capture reagent specific for the reporter species;   wherein the mobilisable reporter species is situated upstream from the detection zone.   
     
     
         6 . An assay kit or device according to any one of  claims 2 - 5 , further comprising:
 a mobilisable control marker situated upstream of the detection zone; and   a control zone situated downstream of the detection zone comprising an immobilised capture reagent capable of binding the control marker.   
     
     
         7 . An assay kit or device according to any preceding claim, wherein the analyte is a hapten. 
     
     
         8 . A method of detecting the presence of an analyte of interest in a sample, the method comprising:
 allowing the sample to contact a labelled species having first and second binding regions, wherein the first binding region is capable of binding to the analyte of interest and the second binding region is capable of binding to a reporter species;   allowing the sample to contact immobilised species capable of binding to the first binding region of the labelled species;   subsequently allowing the sample to contact immobilised capture reagent capable of binding the reporter species;   wherein the reporter species is added prior to contact of the sample with the immobilised capture reagent, and wherein, if no analyte is present in the sample, the labelled species binds to the immobilised species and therefore is unable to bind to the immobilised capture reagent via the reporter species, and wherein, if analyte is present in the sample, the analyte binds to the labelled species such that the labelled species is unable to bind to the immobilised species but can bind to the immobilised capture reagent via the reporter species, the presence of the analyte thus being determined by the presence of labelled species bound to the immobilised capture reagent via the reporter species.   
     
     
         9 . A method according to  claim 8 , wherein the sample is exposed to a trapping zone present on a substrate having the immobilised analyte of interest, before being exposed to a detection zone on the substrate having immobilised capture reagent. 
     
     
         10 . A method according to  claim 9 , wherein the sample is exposed to a reagent zone present on the substrate having the labelled species, the labelled species then being mobilized in the sample. 
     
     
         11 . The use of an assay kit or device according to any one of  claims 1  to  7  in the detection of an analyte in a sample.