Assay Device Having Multiple Reagent Cells

Abstract

An assay device includes: a liquid sample zone; a reagent zone downstream and in fluid communication with the sample zone. The reagent zone includes at least two reagent cells containing a reagent material and arranged in the reagent zone such that each reagent cell experiences substantially the same flow conditions of sample from the sample zone. The reagent cells divide the sample flow from the sample zone into multiple flow streams. Also includes are: one or more flow control elements disposed downstream from the reagent zone which combine the multiple flow streams into fewer flow streams; a detection zone in fluid communication with the reagent zone; and a wicking zone in fluid communication with the detection zone having a capacity to receive liquid sample flowing from the detection zone. The sample addition zone, the detection zone and the wicking zone define a fluid flow path.

What is claimed is: 
     
         1 . An assay device comprising:
 a liquid sample zone;   a reagent zone downstream and in fluid communication with the sample zone comprising at least two reagent cells containing a reagent material and arranged in the reagent zone such that each reagent cell experiences substantially the same flow conditions of sample from the sample zone, wherein the reagent cells divide the sample flow from the sample zone into multiple flow streams;   one or more flow control elements disposed downstream from the reagent zone which combine the multiple flow streams into fewer flow streams;   a detection zone in fluid communication with the reagent zone; and   a wicking zone in fluid communication with the detection zone having a capacity to receive liquid sample flowing from the detection zone, wherein the sample addition zone, the detection zone and the wicking zone define a fluid flow path.   
     
     
         2 . An assay device as claimed in  claim 1 , wherein the at least two reagent cells are arranged symmetrically in the reagent zone. 
     
     
         3 . An assay device as claimed in  claim 1 , wherein the elements are arranged such that each flow stream is subjected to the same flow resistance. 
     
     
         4 . An assay device as claimed in  claim 1 , wherein the capture zone has a substrate and projections which extend substantially vertically from the substrate, wherein the projections have a height, cross-section and a distance between one another that defines a capillary space between the projections capable of generating capillary flow parallel to the substrate surface. 
     
     
         5 . An assay device as claimed in  claim 1 , wherein the reagent material comprises a labeled reagent material, and the detection zone has capture elements bound thereto. 
     
     
         6 . An assay device as claimed in  claim 1 , wherein the at least two reagent zones comprises three or more reagent zones. 
     
     
         7 . An assay device comprising:
 a liquid sample addition zone;   a reagent zone downstream and in fluid communication with the sample addition zone comprising 2 n  reagent cells, where n is a non-zero, non-negative integer, arranged in the reagent zone such that each reagent cell experiences substantially the same flow conditions of sample from the sample addition zone, wherein the reagent cells divide the sample flow from the sample addition zone into multiple flow streams;   flow control elements which separate the reagent cells;   one or more flow control elements disposed downstream from the reagent zone which combine the multiple flow streams into fewer flow streams;   a detection zone in fluid communication with the reagent zone capable of producing a detectable signal; and   a wicking zone in fluid communication with the capture zone having a capacity to receive liquid sample flowing from the capture zone, wherein the sample addition zone, the capture zone and the wicking zone define a fluid flow path.   
     
     
         8 . An assay device as claimed in  claim 7 , wherein the elements are arranged such that each flow stream is subjected to the same flow resistance. 
     
     
         9 . An assay device as claimed in  claim 7 , wherein the multiple flow streams are (2 n )×2 flow streams. 
     
     
         10 . An assay device as claimed in  claim 7 , wherein the multiple flow streams are combined into a single flow stream. 
     
     
         11 . An assay device as claimed in  claim 7 , wherein the reverse bifurcation elements comprises a first stage which combines the multiple flow streams into 2 n  flow streams. 
     
     
         12 . An assay device as claimed in  claim 9 , further comprising a second stage which receives the 2 n  flow streams and combines them into 2 n-1  flow streams. 
     
     
         13 . An assay device as claimed in  claim 7 , wherein the one or more flow control elements disposed downstream are arranged to provide channel gates for each of the multiple flow streams which constrict the flow of each of the multiple flow streams. 
     
     
         14 . An assay device as claimed in  claim 13 , wherein the flow control elements comprise structures which extend from the base of a substrate from the device and block the flow of sample and the channel gates are formed from discontinuities of the elements. 
     
     
         15 . An assay device as claimed in  claim 14 , wherein the assay device comprises a substrate that includes a channel for containing the reagent zone and the detection zone, and wherein the outermost flow control structures are wall portions of the channel which extend into and narrow the channel. 
     
     
         16 . An assay device as claimed in  claim 15 , wherein the sides of the channel are substantially straight in the direction of flow and the outermost flow control structures extend from the sidewalls of the channel and extend into and narrow the channel. 
     
     
         17 . An assay device as claimed in  claim 16 , further comprising elements disposed upstream from the reagent cells which contribute to each reagent cell experiencing substantially the same flow conditions of sample from the sample addition zone. 
     
     
         18 . An assay device as claimed in  claim 17 , wherein flow control elements which separate the reagent cells and flow control elements disposed upstream and downstream from the reagent cells are in the shape of an hour-glass structure. 
     
     
         19 . An assay device as claimed in  claim 7 , further comprising elements disposed upstream from the reagent cells which contribute to each reagent cell experiencing substantially the same flow conditions of sample from the sample addition zone. 
     
     
         20 . A method of controlling the flow around the reagent zone in an assay device comprising:
 providing a liquid sample zone;   providing a reagent zone upstream and in fluid communication with the sample zone comprising at least two reagent cells arranged in the reagent zone such that each reagent cell experiences substantially the same flow conditions of sample from the sample zone, wherein the reagent cells divide the sample flow from the sample zone into multiple flow streams;   providing one or more flow control elements disposed upstream from the reagent zone, arranged to provide channel gates having a width narrower than the reagent cells and which are adapted to constrict the flow from the sample leaving the sample zone;   providing one or more flow control elements disposed downstream from the reagent zone which combine the multiple flow streams into fewer flow streams;   providing a detection zone in fluid communication with the reagent zone;   providing a wicking zone in fluid communication with the capture zone having a capacity to receive liquid sample flowing from the capture zone, wherein the sample zone, the detection zone and the wicking zone define a fluid flow path;   adding sample to the sample zone;   flowing the sample from the sample zone through the upstream flow channel gates which increase the velocity of the flow;   flowing the sample past the reagent zone, whereby the flow has larger flow rate near the reagent boundary compared to the flow at a distance from the reagent boundary, resulting in a more complete dissolution of the reagent zone;   flowing the sample past the downstream flow channel gates, which results in a wider reagent plume flowing through the detection zone, as compared to a reagent plume generated by a single reagent cell.   
     
     
         21 . An method as claimed in  claim 20 , wherein the elements are arranged such that each flow stream is subjected to the same flow resistance. 
     
     
         22 . A method as claimed in  claim 20 , wherein the wider reagent plume extends across the entire width of the detection zone. 
     
     
         23 . A method of performing an assay on a liquid sample for the presence or concentration of one or more analyte(s) or control(s), on the assay device according to  claim 1 , comprising:
 depositing a liquid sample containing the analyte(s) of interest onto a sample addition zone of the assay device;   moving the sample by capillary action through a fluid flow path into a reagent zone where it dissolves one or more reagents;   flowing the sample away from the reagent zone having a dissolved reagent plume containing one or more reagents and into detection zone(s) by capillary action through the fluid flow path, wherein signal(s) representative of the presence or concentration of analyte(s) or control(s) is produced; and   reading the signal(s) that are produced in the detection zones to determine the presence or concentration of the analytes or controls.