Biosensor system having enhanced stability and hematocrit performance
View Patent ↗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/mm 2 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.
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 μg/mm 2 of a mediator, and
an enzyme system at a deposition density of at most 0.8 μg/mm 2 ;
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 μm.
4. The strip of claim 1 , where the reagent layer is formed at a deposition density of at most 0.2 μL/mm 2 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 μg/mm 2 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 μm.
15. The strip of claim 1 , where the electrodes are separated from an upper portion of the lid by at least 100 μm.
16. The strip of claim 1 , where the average initial thickness of the reagent layer is from 0.25 to 3 μm.
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 μg/mm 2 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.