Biosensor system having enhanced stability and hematocrit performance

• US 7,862,696 B2
• Filed: 09/10/2007
• Issued: 01/04/2011
• Est. Priority Date: 09/22/2006
• Status: Active Grant

• Current Assignee: Ascensia Diabetes Care Holdings AG (PHC Holdings Corporation)
• Original Assignee: Bayer Healthcare LLC (Bayer AG)
• Inventors: Wu, Huan-Ping, Maurer, Eric, Spradlin, Hope, Nelson, Christine D.
• Primary Examiner(s): Neckel; Alexa D
• Assistant Examiner(s): DIETERLE, JENNIFER M
• Application Number:
  US11/853,010
• Publication Number:
  US 20080156662A1
• Time in Patent Office: 1,212 Days
• Field of Search: 204400-40314, 205775-779, 205790-794, 422/56, 422/82.01, 221/268, 436/514, 436/518, 436/169, 436/172, 436/525, 436/530, 436/805, 436/808, 436/810, 436/66, 436/67, 435 15- 26, 435/7.1, 435/7.2, 435/7.92, 435/817, 435/14, 600/576
• US Class Current: 204/403.01
• CPC Class Codes: C12Q 1/004 mediator-assisted
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: G01N 27/327 Biochemical electrodes , e.g. electrical or mechanical details for in vitro measurements
• CPC Class Codes: G01N 27/3272 Test elements therefor, i.e. disposable laminated substrates with electrodes, reagent and channels optical biosensors G01N33/52
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875
• CPC Class Codes: G01N 27/3274 Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771
• CPC Class Codes: G01N 33/49 Blood chemical methods for determining blood cell populations G01N33/5094; chemical analysis of blood groups or blood types G01N33/80
• CPC Class Codes: G01N 33/5438 Electrodes
• CPC Class Codes: Y10S 435/817 Enzyme or microbe electrode

Abstract

The present invention relates to electrochemical sensor strips and methods of determining the concentration of an analyte in a sample or improving the performance of a concentration determination. The electrochemical sensor strips may include at most 8 μg/mm² of a mediator. The strips, the strip reagent layer, or the methods may provide for the determination of a concentration value having at least one of a stability bias of less than ±10% after storage at 50° C. for 4 weeks when compared to a comparison strip stored at −20° C. for 4 weeks, a hematocrit bias of less than ±10% for whole blood samples including from 20 to 60% hematocrit, and an intercept to slope ratio of at most 20 mg/dL. A method of increasing the performance of a quantitative analyte determination also is provided.

Claims

1. An electrochemical sensor strip for detecting an analyte, comprising:

a base;

a first electrode on the base having at least one first layer on a first conductor, the first layer including a reagent layer comprising

at most 8 μ

g/mm² of a mediator, and

an enzyme system at a deposition density of at most 0.8 μ

g/mm²;

a second electrode on the base;

a lid on the base; and

where the strip provides a determined concentration value having at least one of a stability bias of less than ±

10% after storage at 50°

C. for 2 weeks when compared to a comparison strip stored at −

20°

C. for 2 weeks, a hematocrit bias of less than ±

10% for whole blood samples including from 20 to 60% hematocrit, and an intercept to slope ratio of at most 20 mg/dL.

2. The strip of claim 1, where the second electrode also comprises the at least one first layer on a second conductor.

3. The strip of claim 1, where the average initial thickness of the reagent layer is less than 8 μ

m.

4. The strip of claim 1, where the reagent layer is formed at a deposition density of at most 0.2 μ

L/mm² from a reagent solution.

5. The strip of claim 1, where the reagent layer comprises a partially water soluble polymeric binder that forms a gel-like material on hydration.

6. The strip of claim 1, where the reagent layer comprises at most 1.3 Units of an enzyme system.

7. The strip of claim 1, where the reagent layer comprises at most 2 μ

g/mm² of the mediator.

8. The strip of claim 1, where the stability bias is less than ±

5% after storage at 50°

C. for 2 weeks when compared to the comparison strip stored at −

20°

C. for 2 weeks.

9. The strip of claim 1, where the stability bias is less than ±

5% after storage at 50°

C. for 4 weeks when compared to the comparison strip stored at −

20°

C. for 4 weeks.

10. The strip of claim 1, where the hematocrit bias is less than ±

5% for the whole blood samples including from 20 to 60% hematocrit.

11. The strip of claim 1, where the intercept to slope ratio is at most 10 mg/dL.

12. The strip of claim 1, where the intercept to slope ratio is at most 1 mg/dL.

13. The strip of claim 1, where the first and second electrodes are in substantially the same plane.

14. The strip of claim 1, where the electrodes are separated by greater than 200 μ

m.

15. The strip of claim 1, where the electrodes are separated from an upper portion of the lid by at least 100 μ

m.

16. The strip of claim 1, where the average initial thickness of the reagent layer is from 0.25 to 3 μ

m.

17. The strip of claim 1, where the reagent layer comprises a polymeric binder selected from the group consisting of poly(ethylene oxide), polyvinyl alcohol, hydroxyethylene cellulose, carboxy methyl cellulose, and combinations thereof.

18. The strip of claim 17, where the deposition density of the polymeric binder is at most 2 μ

g/mm² on the first conductor.

19. The strip of claim 1, where the second electrode further comprises a second layer on the second conductor.

20. The strip of claim 19, where the second layer comprises a reagent layer different in composition from the reagent layer of the first layer.

21. The strip of claim 1, where the mediator is a two electron transfer mediator.

22. The strip of claim 21, where the mediator has a redox potential at least 100 mV lower than ferricyanide.

23. The strip of claim 21, where the mediator is selected from the group consisting of 3 phenylimino-3H-phenothiazines, 3 phenylimino-3H phenoxazines, salts thereof, acids thereof, derivatives thereof, and combinations thereof.