Test strip for a lateral flow assay for a sample containing whole cells

Abstract

A test strip for conducting a lateral flow assay for detection of an analyte in a sample that contains cells and fluid is provided, as well as methods for making and using the test strip. This test strip is commercially usable, for example, in a diagnostic device at a point of care for detection of analytes in whole blood.

1 . A test strip comprising (a) a first membrane comprising a chromatographic strip having a first end and a second end; and (b) a sample filter having an upper surface and a lower surface, wherein the lower surface of the sample filter is in capillary contact with the chromatographic strip; wherein the sample filter is capable of separating cells in a sample from fluid in the sample and allows the fluid to pass through to the chromatographic strip, and further wherein the test strip facilitates lateral flow of fluid from the sample filter towards the second end of the chromatographic strip. 
   
   
       2 . The test strip of  claim 1 , wherein the sample filter comprises pores of varying sizes and wherein cells in the sample are retained by the sample filter and fluid in the sample passes through the sample filter. 
   
   
       3 . The test strip of  claim 2 , wherein the sample filter comprises first pores having a first pore size and second pores having a second pore size, wherein the first pores are larger than the second pores and further wherein the first pores are closer to the upper surface of the sample filter and the second pores are closer to the lower surface of the sample filter. 
   
   
       4 . The test trip of  claim 1 , further comprising (c) a sample pad close to the first end of the chromatographic strip and wherein the sample pad allows the fluid to pass through to the chromatographic strip, and further wherein the test strip supports lateral flow of fluid in the sample from the sample pad towards the second end of the chromatographic strip. 
   
   
       5 . The test strip of  claim 3 , further comprising (c) sample pad comprising an upper surface and a lower surface, wherein the lower surface of the sample pad is in capillary contact with the chromatographic strip and wherein the lower surface of the sample filter is in capillary contact with the upper surface of the sample pad and further wherein the test strip supports lateral flow of fluid in the sample from the sample pad towards the second end of the chromatographic strip. 
   
   
       6 . The test strip of  claim 4 , further comprising a selective membrane in capillary contact with the sample filter and the sample pad. 
   
   
       7 . The test strip of  claim 6 , wherein the selective membrane is positioned under the sample filter. 
   
   
       8 . The test strip of  claim 6 , wherein the selective membrane is positioned on top of the sample pad or on top of the chromatographic strip. 
   
   
       9 . The test strip of  claim 6 , wherein the selective membrane contains an agent that selectively binds to a component in the sample and removes the component from the assay environment. 
   
   
       10 . The test strip of  claim 9 , wherein the agent is selected from the group consisting of an antibody, an antigen, a metabolite, a hormone, an enzyme, a virus, a prion, or parts thereof, and an agent that binds to such. 
   
   
       11 . The test strip of  claim 1 , further comprising one or more filters or membrane positioned between the sample filter and the chromatographic strip. 
   
   
       12 . The test strip of  claim 4 , further comprising (d) a conjugate pad comprising an upper surface and a lower surface, wherein the conjugate pad is at or near the second end of the chromatographic strip and wherein the lower surface of the conjugate pad is in capillary contact with the chromatographic strip; (e) a reagent pad comprising an upper surface and a lower surface, wherein the lower surface of the reagent pad is in capillary contact with the upper surface of the conjugate pad; and (f) an absorbent pad at the first end of the chromatographic strip and to a side of the sample pad that is away from the conjugate pad, wherein the absorbent pad is in capillary contact with the chromatographic strip; and wherein the sample filter is capable of separating the cells from the fluid in the sample and the test strip supports lateral flow of fluid in the sample from the sample pad towards the conjugate pad. 
   
   
       13 . The test strip of  claim 12 , wherein the reagent pad further comprises a reagent. 
   
   
       14 . The test strip of  claim 13 , wherein the reagent is a buffer. 
   
   
       15 . The test strip of  claim 12 , wherein the conjugate pad comprises a conjugate that can be released from the conjugate pad upon application of fluid to the conjugate pad, wherein the conjugate is capable of combining with an analyte to be detected to form a detectable signal. 
   
   
       16 .- 37 . (canceled) 
   
   
       38 . A method of conducting a lateral flow assay for detection of an analyte in a sample that contains cells and fluid, comprising the steps of: (a) providing a test strip according to  claim 15 ; (b) applying the sample to the sample filter; (c) allowing flow of fluid from the sample filter to the chromatographic strip and towards the second end of the chromatographic strip; (d) applying a buffer to release the conjugate in the conjugate pad; (e) allowing flow of the conjugate towards the analyte in the sample to form a complex; and (f) detecting presence of the complex. 
   
   
       39 . The method of  claim 38 , further comprising the step of: (g) quantifying amount of complex formed.