METHOD FOR DETERMINING THE CONCENTRATION OF AN ANALYTE IN A LIQUID SAMPLE USING SMALL VOLUME SAMPLES AND FAST TEST TIMES

• US 20120103833A1
• Filed: 12/29/2011
• Published: 05/03/2012
• Est. Priority Date: 11/16/2001
• Status: Active Grant

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Roche Operations Limited (Roche Holding AG)
• Inventors: Wilsey, Christopher D.
• Granted Patent: US 8,303,801 B2
• Time in Patent Office: Days
• US Class Current: 205/777.5
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: C12Q 1/006 for glucose
• CPC Class Codes: G01N 27/307 Disposable laminated or multilayered electrodes G01N27/3272 takes precedence
• 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 27/3275 Sensing specific biomolecules, e.g. nucleic acid strands, based on an electrode surface reaction

Abstract

Analytes in a liquid sample are determined by methods utilizing sample volumes of less than about 1.0 μl and test times within about nine seconds. The methods are preferably performed using small test strips including a sample receiving chamber filled with the sample by capillary action.

Claims

1. A method of determining the concentration of glucose in a blood sample, comprising:

providing a disposable biosensor test strip including a capillary chamber having a depth suitable for capillary flow of blood, and holding a volume of from 0.1 μ

l to 1.0 μ

l of the blood sample, working and counter or reference electrodes with a width of greater than 100 μ

m to about 1000 μ

m disposed within the capillary chamber, and a reagent proximal to or in contact with at least the working electrode, the reagent including an enzyme and a mediator;

applying a blood sample containing glucose into the capillary chamber, the capillary chamber directing capillary flow of the blood sample into contact with the reagent to cause the blood sample to at least partially solubilize or hydrate the reagent, the glucose reacting with the reagent to produce an electroactive reaction product;

detecting the blood sample in the capillary chamber;

following said detecting, providing a delay period prior to application of an electrooxidation assay potential across the working and counter or reference electrodes, said delay period including an open-circuit time during which no potential is applied across the working and counter or reference electrodes;

following said delay period, applying an electrooxidation assay potential across the working and counter or reference electrodes;

electrooxidizing the electroactive reaction product at the working electrode, said electrooxidizing producing an assay current;

measuring the assay current at one or more times after applying the assay potential,

correlating the assay current measurement to the concentration of glucose in the blood sample, and

from about 4 to about 9 seconds after said detecting, providing a readout of the glucose concentration in the blood sample.

2. The method of claim 1 in which said providing a readout comprises providing a readout about 5 seconds after said detecting.

3. The method of claim 1 in which said providing a readout comprises providing a readout about 8 seconds after said detecting.

4. The method of claim 1 in which the delay period is about 3 seconds.

5. The method of claim 1 in which said measuring comprises measuring the assay current at one or more times from about 3 to about 5 seconds after said detecting.

6. The method of claim 1 in which said measuring comprises measuring the assay current at one or more times up to about 2 seconds after the delay period.

7. The method of claim 6 in which said measuring comprises measuring the assay current at one or more times up to about 2 seconds after the open circuit time.

8. The method of claim 1 in which the delay period is about 3 seconds, and in which said measuring comprises measuring the assay current at one or more times from about 3 to about 5 seconds after said detecting.

9. The method of claim 8 in which said measuring comprises measuring the assay current at one or more times up to about 2 seconds after the open circuit time.

10. The method of claim 1 in which said measuring comprises measuring the assay current at a time the assay current is decaying proportionally to t⁻

0.5, wherein t is time measured from the beginning of application of the assay potential.

11. The method of claim 10 in which the delay period is about 3 seconds.

12. The method of claim 10 in which said measuring comprises measuring the assay current at one or more times from about 3 to about 5 seconds after said detecting.

13. The method of claim 10 in which said measuring comprises measuring the assay current at one or more times up to about 2 seconds after the delay period.

14. The method of claim 13 in which said measuring comprises measuring the assay current at one or more times up to about 2 seconds after the open circuit time.

15. The method of claim 10 in which the delay period is about 3 seconds, and in which said measuring comprises measuring the assay current at one or more times from about 3 to about 5 seconds after said detecting.

16. The method of claim 15 in which said measuring comprises measuring the assay current at one or more times up to about 2 seconds after the open circuit time.

17. A method of determining the concentration of glucose in a blood sample, comprising:

providing a disposable biosensor test strip including a capillary chamber having a depth suitable for capillary flow of blood, and holding a volume of about 0.6 μ

l of the blood sample, working and counter or reference electrodes with a width of greater than 100 μ

m to about 1000 μ

m disposed within the capillary chamber, and a reagent proximal to or in contact with at least the working electrode, the reagent including an enzyme and a mediator;

applying a blood sample containing glucose into the capillary chamber, the capillary chamber directing capillary flow of the blood sample into contact with the reagent to cause the blood sample to at least partially solubilize or hydrate the reagent, the glucose reacting with the reagent to produce an electroactive reaction product;

detecting the blood sample in the capillary chamber;

following said detecting, providing a delay period of about 3 seconds prior to application of an electrooxidation assay potential across the working and counter or reference electrodes, said delay period including an open-circuit time during which no potential is applied across the working and counter or reference electrodes;

following said delay period, applying an electrooxidation assay potential across the working and counter or reference electrodes from about 3 seconds to about 5 seconds following said detecting;

electrooxidizing the electroactive reaction product at the working electrode, said electrooxidizing producing an assay current;

measuring the assay current at one or more times after applying the assay potential, said measuring comprising measuring the assay current from about 3 seconds to about 5 seconds after said detecting,

correlating the assay current measurement to the concentration of glucose in the blood sample, and

from about 4 to about 9 seconds after said detecting, providing a readout of the glucose concentration in the blood sample.

18. The method of claim 17 in which said applying comprises applying the assay potential immediately following the open circuit time.

19. The method of claim 18, wherein at the time the assay current is measured the assay current is decaying proportionally to t⁻

0.5, wherein t is time measured from the beginning of application of the assay potential.

20. The method of claim 19 in which said providing a readout comprises providing a readout about 5 seconds after said detecting.

21. The method of claim 19 in which said providing a readout comprises providing a readout about 8 seconds after said detecting.

22. The method of claim 19 in which the capillary chamber has a depth of 25-200 μ

m.

23. A method of determining the concentration of glucose in a blood sample, comprising:

providing a disposable biosensor test strip including a capillary chamber having a depth suitable for capillary flow of blood, and holding a volume of about 0.6 μ

l of the blood sample, working and counter or reference electrodes with a width of greater than 100 μ

m to about 1000 μ

m disposed within the capillary chamber, and a reagent proximal to or in contact with at least the working electrode, the reagent including an enzyme and a mediator;

applying a blood sample containing glucose into the capillary chamber, the capillary chamber directing capillary flow of the blood sample into contact with the reagent to cause the blood sample to at least partially solubilize or hydrate the reagent, the glucose reacting with the reagent to produce an electroactive reaction product;

detecting the blood sample in the capillary chamber;

following said detecting, providing a delay period of about 3 seconds prior to application of an electrooxidation assay potential across the working and counter or reference electrodes, said delay period including an open-circuit time during which no potential is applied across the working and counter or reference electrodes;

following the open circuit time of said delay period, applying an electrooxidation assay potential across the working and counter or reference electrodes from about 3 seconds to about 5 seconds after said detecting;

electrooxidizing the electroactive reaction product at the working electrode, said electrooxidizing producing an assay current;

measuring the assay current at one or more times after applying the assay potential, said measuring comprising measuring the assay current from about 3 seconds to about 5 seconds after said detecting;

correlating the assay current measurement to the concentration of glucose in the blood sample; and

about 5 seconds after said detecting, providing a readout of the glucose concentration in the blood sample.

24. The method of claim 23 in which said measuring comprises measuring the assay current at a time the assay current is decaying proportionally to t⁻

0.5, wherein t is time measured from the beginning of application of the assay potential.

25. The method of claim 24 in which the test strip comprises a counter electrode consisting of a pair of electrically connected counter electrodes within the capillary chamber, the working electrode being located between the counter electrodes, the reagent being located proximal to or in contact with both the working electrode and the counter electrodes.

26. The method of claim 25 in which the capillary chamber has a depth of 25-200 μ

m.

27. A method of determining the concentration of glucose in a blood sample, comprising:

providing a disposable biosensor test strip including a capillary chamber having a depth suitable for capillary flow of blood, and holding a volume of about 0.6 μ

l of the blood sample, working and counter or reference electrodes with a width of greater than 100 μ

m to about 1000 μ

m disposed within the capillary chamber, and a reagent proximal to or in contact with at least the working electrode, the reagent including an enzyme and a mediator;

applying a blood sample containing glucose into the capillary chamber, the capillary chamber directing capillary flow of the blood sample into contact with the reagent to cause the blood sample to at least partially solubilize or hydrate the reagent, the glucose reacting with the reagent to produce an electroactive reaction product;

detecting the blood sample in the capillary chamber;

following said detecting, providing a delay period of about 3 seconds prior to application of an electrooxidation assay potential across the working and counter or reference electrodes, said delay period including an open-circuit time during which no potential is applied across the working and counter or reference electrodes;

following the open circuit time of said delay period, applying an electrooxidation assay potential across the working and counter or reference electrodes from about 3 seconds to about 5 seconds after said detecting;

electrooxidizing the electroactive reaction product at the working electrode, said electrooxidizing producing an assay current;

measuring the assay current at one or more times after applying the assay potential, said measuring comprising measuring the assay current from about 3 seconds to about 5 seconds after said detecting;

correlating the assay current measurement to the concentration of glucose in the blood sample; and

about 8 seconds after said detecting, providing a readout of the glucose concentration in the blood sample.

28. The method of claim 27 in which said measuring comprises measuring the assay current at a time the assay current is decaying proportionally to t⁻

0.5, wherein t is time measured from the beginning of application of the assay potential.

29. The method of claim 28 in which the test strip comprises a counter electrode consisting of a pair of electrically connected counter electrodes within the capillary chamber, the working electrode being located between the counter electrodes, the reagent being located proximal to or in contact with both the working electrode and the counter electrodes.

30. The method of claim 29 in which the capillary chamber has a depth of 25-200 μ

m.