Method of using a small volume in vitro analyte sensor with diffusible or non-leachable redox mediator

• US 6,592,745 B1
• Filed: 05/17/2000
• Issued: 07/15/2003
• Est. Priority Date: 10/08/1998
• Status: Expired due to Term

• Current Assignee: Abbott Diabetes Care Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Therasense Incorporated (Abbott Laboratories Incorporated)
• Inventors: Colman, Fredric C., Krishnan, Rajesh, Heller, Ephraim, Heller, Adam, Feldman, Benjamin J., Mao, Fei, Funderburk, Jeffery V., Vivolo, Joseph A.
• Primary Examiner(s): Nguyen, Nam
• Assistant Examiner(s): NOGUEROLA, ALEXANDER STEPHAN
• Application Number:
  US09/572,617
• Time in Patent Office: 1,154 Days
• Field of Search: 205/777.5, 205/778, 204/403.04, 204/403.09, 204/403.1, 204/403.11
• 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: C12Q 1/32 involving dehydrogenase
• CPC Class Codes: G01N 27/3271 Amperometric enzyme electrodes for analytes in body fluids, e.g. glucose in blood amperometry per se G01N27/49; aspects concerning the enzyme reagent C12Q1/001
• 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 27/3274 Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771
• CPC Class Codes: Y10T 156/1052 with cutting, punching, tearing or severing
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/49004 including measuring or testing of device or component part
• CPC Class Codes: Y10T 29/49007 Indicating transducer
• CPC Class Codes: Y10T 29/49126 Assembling bases
• CPC Class Codes: Y10T 29/49128 Assembling formed circuit to base
• CPC Class Codes: Y10T 29/4913 Assembling to base an electrical component, e.g., capacitor, etc.
• CPC Class Codes: Y10T 29/49147 Assembling terminal to base
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base
• CPC Class Codes: Y10T 29/49204 Contact or terminal manufacturing
• CPC Class Codes: Y10T 29/49208 by assembling plural parts
• CPC Class Codes: Y10T 29/4921 with bonding
• CPC Class Codes: Y10T 29/49794 Dividing on common outline

Abstract

A sensor utilizing a non-leachable or diffusible redox mediator is described. The sensor includes a sample chamber to hold a sample in electrolytic contact with a working electrode, and in at least some instances, the sensor also contains a non-leachable or a diffusible second electron transfer agent. The sensor and/or the methods used produce a sensor signal in response to the analyte that can be distinguished from a background signal caused by the mediator. The invention can be used to determine the concentration of a biomolecule, such as glucose or lactate, in a biological fluid, such as blood or serum, using techniques such as coulometry, amperometry, and potentiometry. An enzyme capable of catalyzing the electrooxidation or electroreduction of the biomolecule is typically provided as a second electron transfer agent.

Claims

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

(a) contacting a sample with an electrochemical sensor comprising;

(i) an electrode pair comprising a working electrode and a counter electrode, wherein the working electrode and counter electrode are separated by a closest distance in a range of 200 to 1000 μ

m;

(ii) a measurement zone positioned adjacent to the working electrode and the counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ

L of the sample; and

(iii) an analyte-responsive enzyme and a diffusible redox mediator disposed in the measurement zone;

(b) holding the sample within the measurement zone in a non-flowing manner;

(c) generating a sensor signal at the working electrode within a measurement period of no greater than about 5 minutes, wherein a background signal that is generated by the redox mediator is no more than five times a signal generated by oxidation or reduction of 5 mM of glucose; and

(d) determining the concentration of the glucose using the sensor signal.

2. The method of claim 1, wherein the step of contacting a sample with an electrochemical sensor comprises:

(a) contacting a sample with the electrochemical sensor, wherein the working electrode and counter electrode are separated by a closest distance in a range of 200 to 400 μ

m.

3. The method of claim 1, wherein the step of contacting a sample with an electrochemical sensor comprises:

(a) contacting a sample with the electrochemical sensor, wherein the redox mediator disposed in the measurement zone does not shuttle between the working electrode and counter electrode more than an average of 1 time during the measurement period.

4. The method of claim 3, wherein the step of contacting a sample with an electrochemical sensor comprises:

(a) contacting a sample with the electrochemical sensor, wherein the redox mediator disposed in the measurement zone does not shuttle between the working electrode and counter electrode more than an average of 0.1 time during the measurement period.

5. The method of claim 1, wherein the step of contacting a sample with an electrochemical sensor comprises:

(a) contacting a sample with the electrochemical sensor, wherein the electrode pair has the working electrode disposed on a first substrate and the counter electrode disposed on the first substrate.

6. The method of claim 1, wherein the step of contacting a sample with an electrochemical sensor comprises:

(a) contacting a sample with an electrochemical sensor, wherein the electrode pair has the working electrode disposed on a first substrate and the counter electrode disposed on a second substrate.

7. The method of claim 6, wherein the step of contacting a sample with an electrochemical sensor comprises:

(a) contacting a sample with an electrochemical sensor, wherein the first substrate is facing the second substrate.

8. The method of claim 1, wherein the step of determining the concentration of the glucose using the sensor signal comprises:

(a) determining the concentration of the glucose by amperometry using the sensor signal.

9. The method of claim 8, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein the concentration of the analyte in the measurement zone does not change by more than 20% during the measurement period.

10. The method of claim 8, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein a concentration of the redox mediator in the measurement zone in a given oxidation state does not change by more than 20% during the measurement period.

11. The method of claim 8, wherein the step of determining the concentration of the glucose using the sensor signal comprises:

(a) determining the concentration of the analyte by a measurement technique selected from the group consisting of chronoamperometry and Cotrell-type measurement techniques using the sensor signal.

12. The method of claim 11, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein the concentration of the analyte in the measurement zone changes by more than 20% during the measurement period.

13. The method of claim 11, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein a concentration of the redox mediator in the measurement zone in a given oxidation state changes by more than 20% during the measurement period.

14. The method of claim 1, wherein the step of determining the concentration of the glucose using the sensor signal further comprises:

(a) reducing variation due to the diffusivity of the redox mediator or analyte by measuring the temperature and compensating for a temperature effect on diffusivity of the redox mediator or analyte in the measurement zone.

15. The method of claim 1, wherein the step of determining the concentration of the glucose using the sensor signal comprises:

(a) determining the concentration of the glucose by potentiometry using the sensor signal.

16. The method of claim 15, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein the concentration of the analyte in the measurement zone does not change by more than 20% during the measurement period.

17. The method of claim 15, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein a concentration of the redox mediator in the measurement zone in a given oxidation state does not change by more than 20% during the measurement period.

18. The method of claim 1, wherein the step of determining the concentration of the glucose using the sensor signal comprises:

(a) determining the concentration of the glucose by chronopotentiometry using the sensor signal.

19. The method of claim 18, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein the concentration of the analyte in the measurement zone changes by more than 20% during the measurement period.

20. The method of claim 18, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein a concentration of the redox mediator in the measurement zone in a given oxidation state changes by more than 20% during the measurement period.

21. The method of claim 1, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein the background signal that is generated by the redox mediator is the same or less than the signal generated by oxidation or reduction of 5 mM glucose.

22. The method of claim 1, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein the background signal that is generated by the redox mediator is no more than 25% of the signal generated by oxidation or reduction of 5 mM glucose.

23. The method of claim 1, wherein the step of generating a sensor signal at the working electrode within a measurement period comprises:

(a) generating a sensor signal at the working electrode within a measurement period, wherein the background signal that is generated by the redox mediator is no more than 5% of the signal generated by oxidation or reduction of 5 mM glucose.

24. The method of claim 1, wherein the sensor is a sensor strip comprising a rectangular base and an additional working electrode, each of the electrodes being positioned on the base, the method further comprising the steps of lancing the skin of a patient to form a blood sample on the skin of the patient before the contacting step, and, wherein the contacting step includes drawing the sample into the sensor through an opening at an end edge of the sensor strip from the sample on the skin of the patient into the sensor and first contacting a first of the working electrodes and then contacting a second of the working electrodes.

25. The method of claim 24, wherein the step of lancing the skin of a patient comprises lancing the forearm skin of a patient.

26. The method of claim 1, wherein the sensor comprises a base on which the working electrode is formed, wherein each electrode comprises gold and at least a portion of the working electrode is situated in a circular recess in the sensor, the method further comprising the steps of lancing the skin of a patient to form a blood sample on the skin of the patient before the contacting step, and, wherein the contacting step includes drawing the sample into the sensor through an opening at an edge of the sensor from the skin of the patient into the sensor and into the circular recess to contact the working electrode.

27. The method of claim 26, wherein the step of lancing the skin of a patient comprises lancing the forearm skin of a patient.

28. A method for determining a concentration of glucose in a sample, comprising the steps of:

(a) contacting a sample with an electrochemical sensor comprising;

(i) a working electrode and a counter electrode, wherein the working electrode and counter electrode are separated by a closest distance no greater than 1000 μ

m;

(ii) a measurement zone positioned adjacent to the working electrode and the counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ

L of the sample; and

(iii) an analyte-responsive enzyme and a diffusible redox mediator disposed in the measurement zone;

(b) holding the sample within the measurement zone in a non-flowing manner;

(c) generating a sensor signal at the working electrode within a measurement period, wherein a background signal that is generated by the redox mediator is no more than five times a signal generated by oxidation or reduction of an average normal physiological amount of analyte; and

(d) determining the connection of the glucose by amperometry using the sensor signal.

29. The method of claim 28, wherein the sensor comprises a base on which the working electrode is formed, wherein each electrode comprises gold and at least a portion of the working electrode is situated in a circular recess in the sensor, the method further comprising the steps of lancing the skin of a patient to form a blood sample on the skin of the patient before the contacting step, and, wherein the contacting step includes drawing the sample into the sensor through an opening at an edge of the sensor from the skin of the patient into the sensor and into the circular recess to contact the working electrode.

30. The method of claim 29, wherein the step of lancing the skin of a patient comprises lancing the forearm skin of a patient.

31. The method of claim 28, wherein the step of contacting a sample with an electrochemical sensor comprises:

(a) contacting a sample with an electrochemical sensor, wherein the working electrode and counter electrode are separated by a closest distance in a range of 200 to 400 μ

m.

32. The method of claim 28, wherein the sensor is a sensor strip comprising a rectangular base and an additional working electrode, each of the electrodes being positioned on the base, the method further comprising the steps of lancing the skin of a patient to form a blood sample on the skin of the patient before the contacting step, and, wherein the contacting step includes drawing the sample into the sensor through an opening at an end edge of the sensor strip from the sample on the skin of the patient into the sensor and first contacting a first of the working electrodes and then contacting a second of the working electrodes.

33. The method of claim 32, wherein the step of lancing the skin of a patient comprises lancing the forearm skin of a patient.

34. A method for determining a concentration of an analyte in a sample, comprising the steps of:

(a) contacting a sample with an electrochemical sensor comprising;

(i) an electrode pair comprising a working electrode and a counter electrode, wherein the working electrode and counter electrode are separated by a closest distance in a range of 200 to 1000 μ

m;

(ii) a measurement zone positioned adjacent to the working electrode and the counter electrode, wherein the measurement zone is sized to contain a volume of no more than about 1 μ

L of the sample; and

(iii) an analyte-responsive enzyme and a diffusible redox mediator disposed in the measurement zone;

(b) holding the sample within the measurement zone in a non-flowing manner;

(c) generating a sensor signal at the working electrode within a measurement period, wherein a background signal that is generated by the redox mediator is no more than five times a signal generated by oxidation or reduction of an average normal physiological amount of analyte; and

(d) determining the concentration of the analyte using the sensor signal.

35. The method of claim 34, wherein the sensor is a sensor strip comprising a rectangular base and an additional working electrode, each of the electrodes being positioned on the base, the method further comprising the steps of lancing the skin of a patient to form a blood sample on the skin of the patient before the contacting step, and, wherein the contacting step includes drawing the sample into the sensor through an opening at an end edge of the sensor strip from the sample on the skin of the patient into the sensor and first contacting a first of the working electrodes and then contacting a second of the working electrodes.

36. The method of claim 35 wherein the step of lancing the skin of a patient comprises lancing the forearm skin of a patient.

37. The method of claim 34, wherein the sensor comprises a base on which the working electrode is formed, wherein each electrode comprises gold and at least a portion of the working electrode is situated in a circular recess in the sensor, the method further comprising the steps of lancing the skin of a patient to form a blood sample on the skin of the patient before the contacting step, and, wherein the contacting step includes drawing the sample into the sensor through an opening at an edge of the sensor from the skin of the patient into the sensor and into the circular recess to contact the working electrode.

38. The method of claim 37 wherein the step of lancing the skin of a patient comprises lancing the forearm skin of a patient.