Method of making a test strip for determining analyte concentration over a broad range of sample volumes

• US 20020106710A1
• Filed: 03/28/2002
• Published: 08/08/2002
• Est. Priority Date: 08/28/1989
• Status: Active Grant

• Current Assignee: Cilag Gmbh International (Johnson & Johnson)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Tuohy, Deborah P., Dubowik, John M.
• Granted Patent: US 6,949,221 B2
• Time in Patent Office: Days
• US Class Current: 435/14
• CPC Class Codes: C12Q 1/54 involving glucose or galactose
• CPC Class Codes: G01N 33/48 Biological material, e.g. blood, urine G01N33/02, G01N33/26, G01N33/44, G01N33/46 take precedence; Haemocytometers counting blood corpuscules distributed over a surface by scanning the surface G06M11/02
• CPC Class Codes: G01N 33/521 Single-layer analytical elements
• CPC Class Codes: G01N 33/523 the element being adapted for a specific analyte
• CPC Class Codes: G01N 33/54386 Analytical elements
• CPC Class Codes: Y10T 156/10 Methods of surface bonding and/or assembly therefor

Abstract

A test strip for determining the concentration of an analyte in a body fluid includes a membrane in fluid communication with a porous layer. The membrane and the porous layer are divided into compressed portions, which restrict the capillary flow of the body fluid, and uncompressed portions. The uncompressed portions are adapted to absorb and retain body fluids in excess of the amount required for operation of the test strip. The test strip may be constructed with an internal relief chamber to accommodate the uncompressed portions. A method of making the test strip by pressure and/or heat sealing individual components on a shaping die is also provided.

Claims

1. A test strip, suitable for determining the concentration of an analyte in a body fluid, which comprises:

a cover sheet, having an elongated window cut through it;

a lamellar membrane adjacent to the cover sheet, extending across and into the window and containing a reagent that reacts with the analyte to produce a color change, a porous sheet in fluid communication with the membrane, having a pillow portion and a compressed portion, the pillow portion being substantially aligned with the window; and

a backing sheet, adjoining the porous sheet and having a sample port cut through it;

whereby fluid introduced into the sample port can flow to the membrane, and analyte in the fluid can react with the reagent to produce a color change visible through the window.

2. The test strip of claim 1 wherein the analyte is glucose and the body fluid is blood.

3. The test strip of claim 1 wherein the cover sheet comprises polyethylene terephthalate.

4. The test strip of claim 1 wherein the backing sheet comprises polyethylene terephthalate.

5. The test strip of claim 1 wherein the membrane is anisotropic, having relatively larger pores nearer the sample port.

6. The test strip of claim 1 wherein the membrane contains a plurality of zones with various predetermined concentrations of an inhibitor for the analyte-reagent reaction.

7. The test strip of claim 1 wherein the porous sheet comprises a nonwoven material.

8. The test strip of claim 7 wherein the nonwoven material is a polyester or a polyester-nylon blend.

9. The test strip of claim 1 wherein the pillow region can absorb in the range of about 6 to about 100 microliters of human blood.

10. The test strip of claim 9 wherein the pillow region can absorb about 30 microliters of human blood.

11. The test strip of claim 1 wherein the membrane can absorb in the range of about 8 to about 10 microliters of human blood.

12. The test strip of claim 1 wherein the cover sheet is attached to the membrane with a heat-sealable adhesive.

13. The test strip of claim 11 wherein the adhesive comprises polyisobutylene rubber or ethylene vinyl acetate.

14. The test strip of claim 13 wherein the adhesive comprises ethylene vinyl acetate.

15. The test strip of claim 11 wherein the adhesive is a low-density polyethylene co-extruded with the cover sheet.

16. The test strip of claim 1 wherein the porous sheet contains polypropylene glycol in an amount effective as a surfactant to improve wicking of fluid by the porous sheet.

17. The test strip of claim 1 wherein a nonwoven layer of polyethylene-coated polyester is located between the membrane and the porous sheet.

19. The test strip of claim 18 wherein the surfaces of the center plate and cover sheet that adjoin the membrane comprise solid thermoplastics which penetrate the membrane, creating a seal and fastening the center plate and cover sheet to the membrane.

20. The test strip of claim 18 wherein the surfaces of the backing sheet and center plate that adjoin the porous sheet comprise solid thermoplastics, which penetrate the pores of the porous sheet, creating a seal and fastening the backing sheet and center plate to the absorbent sheet.

18. A test strip, suitable for detecting an analyte in a body fluid, comprising:

a cover sheet having an elongated window cut through it;

a lamellar membrane adjacent to the cover sheet, extending across the window and containing a reagent that reacts with the analyte to produce a color change;

a relatively incompressible center plate, adjacent to the membrane and having a central portion cut out of it to form an internal relief chamber, into which a portion of the membrane protrudes, the relief chamber being substantially aligned with the window;

a porous sheet adjoining-the center plate, in fluid communication with the membrane, and having a pillow portion that extends into the relief chamber; and

a backing sheet adjoining the porous sheet and having a sample port cut through it;

whereby fluid introduced into the sample port can flow to the membrane, and analyte in the fluid can react with the reagent to produce a color change visible through the window.

21. A method of making a test strip for determining the concentration of an analyte in a body fluid, which comprises:

assembling as a sealable package;

a cover sheet having an elongated window cut in it;

a lamellar membrane which extends across the window, has a sealable coating and contains a reagent that reacts with the analyte to produce a color change;

an adhesive-coated porous sheet, and a backing sheet which contacts the adhesive and has through it a sample port;

positioning the sealable package between a substantially flat plate and a shaping die that defines an elongated groove having a length about equal to the length of the window, such that the groove and the window are in alignment; and

applying the die to the sealable package with sufficient pressure to compress portions of the porous layer that are located on opposite sides of the groove and to bond the cover sheet to the membrane and the porous sheet to the backing sheet.

22. The method of claim 21 which further comprises venting the porous layer by removing a part of the sealable package adjacent to an end of the groove.

23. The method of claim 21 in which the sealable package and sealable coating are heat sealable.

24. The method of claim 23 wherein the die is applied to the heat-sealable package with a pressure in the range of about 340 to about 1400 kPa. at a temperature in the range of about 65°

C. to about 110°

C.