Electrochemical sensors including electrode systems with increased oxygen generation

• US 20050051440A1
• Filed: 07/21/2004
• Published: 03/10/2005
• Est. Priority Date: 07/25/2003
• Status: Active Grant

• Current Assignee: DexCom Incorporated
• Original Assignee: DexCom Incorporated
• Inventors: Carr-Brendel, Victoria, Simpson, Peter C., Tapsak, Mark A., Goode, Paul
• Granted Patent: US 7,108,778 B2
• Time in Patent Office: Days
• US Class Current: 205/778
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14865 invasive, e.g. introduced into the body by a catheter or needle or using implanted sensors
• CPC Class Codes: C12Q 1/003 Functionalisation
• CPC Class Codes: G01N 27/3272 Test elements therefor, i.e. disposable laminated substrates with electrodes, reagent and channels optical biosensors G01N33/52

Abstract

The present invention relates generally to systems and methods for increasing oxygen generation in electrochemical sensors in order to overcome the oxygen limitations. The preferred embodiments employ electrode systems with at least two electrodes in relatively close proximity to each other; wherein at least one electrode is configured to generate oxygen and at least one other electrode is configured to sense an analyte or a product of a reaction indicative of the concentration of analyte. The oxygen generated by the oxygen-generating electrode is available to the catalyst within a membrane system and/or the counter electrode, thereby enabling the electrochemical sensors of the preferred embodiments to function even during ischemic conditions.

Claims

1. An electrochemical sensor for determining a presence or a concentration of an analyte in a fluid, the sensor comprising:

a membrane system comprising an enzyme that reacts with the analyte;

a first working electrode comprising a conductive material, wherein the first working electrode is configured to measure a product of the reaction of the enzyme with the analyte; and

an auxiliary electrode comprising a conductive material, wherein the auxiliary electrode is configured to generate oxygen,

wherein the auxiliary electrode is located at a proximity to the first working electrode such that oxygen generated at the auxiliary electrode diffuses to the enzyme at a location substantially above the first working electrode.

2. The electrochemical sensor of claim 1, wherein a distance between the first working electrode and the auxiliary electrode is from about 0.5 to about 1000 microns.

3. The electrochemical sensor of claim 1, wherein a distance between the first working electrode and the auxiliary electrode is from about 10 to about 100 microns.

4. The electrochemical sensor of claim 1, wherein a distance between the first working electrode and the auxiliary electrode is about 50 microns.

5. The electrochemical sensor of claim 1, wherein at least one of the first working electrode and the auxiliary electrode is configured in a pattern selected from the group consisting of spiral, concentric, adjacent, interdigitated, and sandwiched.

6. The electrochemical sensor of claim 1, wherein at least one of the first working electrode and the auxiliary electrode is formed by a process selected from the group consisting of thick film printing, screen printing, lithography, letter press printing, vapor deposition, spray coating, pad printing, ink jet printing, laser jet printing, roller coating, vacuum deposition, thin film deposition, sputtering, evaporation, glow discharge methods, gluing, epoxy bonding, casting, rolling, machining, and laser cutting.

7. The electrochemical sensor of claim 1, wherein the first working electrode comprises a sensing electrode, and wherein the auxiliary electrode comprises an oxygen-generating electrode.

8. The electrochemical sensor of claim 1, further comprising a counter electrode, wherein the counter electrode is situated in proximity to the auxiliary electrode such that oxygen generated by the auxiliary electrode diffuses to the counter electrode.

9. The electrochemical sensor of claim 1, further comprising at least one additional auxiliary electrode comprising a conductive material and configured to generate oxygen.

10. The electrochemical sensor of claim 9, wherein the additional auxiliary electrode is configured to substantially surround the first working electrode.

11. An electrochemical sensor for determining a presence or a concentration of an analyte in a fluid, the sensor comprising:

a membrane system comprising an enzyme that reacts with the analyte;

a first working electrode comprising a conductive material, wherein the first working electrode is configured to measure a product of the reaction of the enzyme with the analyte; and

an auxiliary electrode comprising a conductive material, wherein the auxiliary electrode is configured to generate oxygen; and

a counter electrode comprising a conductive material, wherein the counter electrode is configured to reduce oxygen so as to balance current being generated by the first working electrode,

wherein the auxiliary electrode is located at a proximity to the counter electrode such that oxygen generated at the auxiliary electrode diffuses to the counter electrode to be reduced thereby.

12. The electrochemical sensor of claim 11, wherein a distance between the auxiliary electrode and the counter electrode is from about 0.5 microns to about 1000 microns.

13. The electrochemical sensor of claim 11, wherein a distance between the auxiliary electrode and the counter electrode is from about 10 microns to about 100 microns.

14. The electrochemical sensor of claim 11, wherein a distance between the auxiliary electrode and the counter electrode is about 50 microns.

15. The electrochemical sensor of claim 11, wherein at least one of the working electrode and the counter electrode is configured in a pattern selected from the group consisting of spiral, concentric, adjacent, interdigitated, and sandwiched.

16. The electrochemical sensor of claim 11, wherein at least one of the working electrode and the counter electrode is formed by a process selected from the group consisting of thick film printing, screen printing, lithography, letter press printing, vapor deposition, spray coating, pad printing, ink jet printing, laser jet printing, roller coating, vacuum deposition, thin film deposition, sputtering, evaporation, glow discharge methods, gluing, epoxy bonding, casting, rolling, machining, and laser cutting.

17. The electrochemical sensor of claim 11, wherein the first working electrode comprises a sensing electrode, and wherein the auxiliary electrode comprises an oxygen-generating electrode.

18. The electrochemical sensor of claim 11, further comprising an additional working electrode comprising a conductive material, wherein the additional working electrode is configured to measure an additional analyte or is configured to function as a baseline-subtracting electrode.

19. The electrochemical sensor of claim 11, further comprising at least one additional working electrode comprising a conductive material and configured to generate oxygen.

20. The electrochemical sensor of claim 19, wherein the additional working electrode is configured to substantially surround the first working electrode.

21. A method for generating oxygen for use at an electrochemical analyte sensor, the method comprising:

providing a membrane system comprising an enzyme that reacts with the analyte;

providing a first working electrode comprising a conductive material;

measuring a product of a reaction of the enzyme with the analyte at the first working electrode, wherein a concentration of the product is indicative of a concentration of the analyte;

providing an auxiliary electrode comprising a conductive material; and

generating oxygen at the auxiliary electrode,

wherein the auxiliary electrode is configured such that the oxygen generated at the auxiliary electrode diffuses toward the enzyme at a location substantially above the first working electrode.

22. The method of claim 21, wherein the enzyme is selected from the group consisting of glucose oxidase, amino acid oxidase, alcohol oxidase, galactose oxidase, lactate oxidase, and cholesterol oxidase.

23. The method of claim 21, wherein the analyte is selected from the group consisting of glucose, amino acid, alcohol, galactose, lactate, and cholesterol.

24. A method for generating oxygen for use at an electrochemical analyte sensor, the method comprising:

providing an electrochemical sensor comprising a sensing electrode and an auxiliary electrode;

measuring an analyte at the sensing electrode; and

generating oxygen at the auxiliary electrode,

wherein the electrochemical sensor comprises an oxygen-utilizing source, and wherein the oxygen generated by the auxiliary electrode diffuses to the oxygen-utilizing source.

25. The method of claim 24, wherein the oxygen-utilizing source comprises an enzyme.

26. The method of claim 24, wherein the oxygen-utilizing source comprises a counter electrode.