Electrochemical method for measuring chemical reaction rates

• US 6,444,115 B1
• Filed: 07/14/2000
• Issued: 09/03/2002
• Est. Priority Date: 07/14/2000
• Status: Expired due to Term

• Current Assignee: Cilag Gmbh International (Johnson & Johnson)
• Original Assignee: Lifescan Incorporated (Duv Holding Corporation)
• Inventors: Hodges, Alastair, Chatelier, Ron
• Primary Examiner(s): Tung, T.
• Assistant Examiner(s): NOGUEROLA, ALEXANDER STEPHAN
• Application Number:
  US09/616,556
• Time in Patent Office: 781 Days
• Field of Search: 205/775, 205/777.5, 205/793.5, 205/792, 204/403
• US Class Current: 205/792
• CPC Class Codes: C12Q 1/004 mediator-assisted
• CPC Class Codes: C12Q 1/006 for glucose
• 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 33/84 involving inorganic compounds or pH

Abstract

The present invention relates to the measurement of the progress of a chemical reaction that generates an electroactive reaction product that is subsequently detected at an electrode amperometrically or coulometrically. The method is useful in applications where it is desirable to follow the progress of a chemical reaction, particularly in sensor applications where the progress of the reaction of an analyte can be useful in determining the analyte concentration.

Claims

1. A method for measuring a rate of a chemical reaction between a component of a liquid sample and a reagent, the reaction producing an electroactive species, comprising:

providing an electrochemical cell having a working electrode, a counter electrode, and at least one wall;

substantially immobilizing the reagent in the electrochemical cell at a site at a minimum distance from the working electrode, wherein the site is situated on the counter electrode, wherein the distance is such that transfer of the electroactive species from the site to the working electrode is diffusion controlled;

placing the liquid sample in the electrochemical cell such that the liquid sample is in contact with the reagent, the working electrode, and the counter electrode;

reacting the component with the reagent to produce the electroactive species;

applying a potential between the working electrode and the counter electrode, wherein the potential is sufficient to electrochemically react the electroactive species at the working electrode; and

measuring the current produced by the electrochemical reaction at the working electrode to obtain a measure of the rate of the chemical reaction.

2. The method according to claim 1, wherein the working electrode and the counter electrode are sufficiently spaced such that a product of an electrochemical reaction occurring at the counter electrode does not reach the working electrode while the current is measured.

3. The method according to claim 2, wherein the working electrode and the counter electrode are spaced apart at a distance greater than about 500 microns.

4. The method according to claim 3, wherein the distance is between about 500 microns and about 5 mm.

5. The method according to claim 4, wherein the distance is between about 1 mm and about 2 mm.

6. The method according to claim 2, wherein the working electrode and the counter electrode are situated on the same plane.

7. The method according to claim 1, wherein the site and the working electrode are separated by a minimum distance ranging from about 10 microns to about 5 millimeters.

8. The method according to claim 7, wherein the minimum distance ranges from about 50 microns to about 500 microns.

9. The method according to claim 8, wherein the minimum distance ranges from about 100 microns to about 200 microns.

10. The method of claim 1, wherein the counter electrode is capable of functioning as a combined counter/reference electrode.

11. The method of claim 1, wherein the electrochemical cell further comprises a reference electrode.

12. The method according to claim 1, wherein the working electrode functions as an anode.

13. The method according to claim 12, wherein the working electrode comprises a material selected from the group consisting of platinum, palladium, carbon, carbon in combination with one or more inert binders, iridium, indium oxide, tin oxide, indium in combination with tin oxide, and mixtures thereof.

14. The method according to claim 1, wherein the working electrode functions as a cathode.

15. The method according to claim 14, wherein the working electrode comprises a material selected from the group consisting of platinum, palladium, carbon, carbon in combination with one or more inert binders, iridium, indium oxide, tin oxide, indium in combination with tin oxide, steel, stainless steel, copper, nickel, silver, chromium, and mixtures thereof.

16. The method according to claim 1, wherein the counter electrode comprises a material selected from the group consisting of platinum, palladium, carbon, carbon in combination with inert binders, iridium, indium oxide, tin oxide, indium in combination with tin oxide, steel, stainless steel, copper, nickel, chromium, silver, and mixtures thereof.

17. The method according to claim 1, wherein the counter electrode comprises silver coated with a substantially insoluble silver salt.

18. The method according to claim 17, wherein the silver salt is selected from the group consisting of silver chloride, silver bromide, silver iodide, silver ferrocyanide, and silver ferricyanide.

19. The method according to claim 1, wherein the site is situated on the wall.

20. The method according to claim 1, wherein the site is situated in a plane facing and substantially parallel to the working electrode.

21. The method according to claim 1, wherein the reagent is contained within a polymeric matrix attached to a surface in the electrochemical cell.

22. The method according to claim 1, wherein the reagent is chemically tethered to a surface in the electrochemical cell.

23. The method according to claim 1, wherein the reagent is physically tethered to a surface in the electrochemical cell.

24. The method according to claim 1, wherein the reagent is dried onto a surface in the electrochemical cell, the reagent exhibiting sufficiently low mobility in the liquid sample such that the reagent does not substantially migrate-while the current is measured.

25. The method according to claim 24, wherein the sample comprises whole blood.

26. The method according to claim 24, wherein the component comprises glucose.

27. The method according to claim 26, wherein the reagent comprises an enzyme selected from the group consisting of PQQ dependent glucose dehydrogenase, NAD dependent glucose dehydrogenase, glucose oxidase, lactate dehydrogenase, and alcohol dehydrogenase.

28. The method according to claim 1, further comprising a redox mediator.

29. The method according to claim 1, wherein the redox mediator is selected from the group consisting ferrocinium, osmium complexes with bipyridine, and benzophenone.

30. The method according to claim 1, wherein the redox mediator comprises ferricyanide.

31. The method according to claim 30, wherein the potential is between about +50 mV and +500 mV.

32. The method according to claim 30, wherein the potential is about +300 mV.

33. A method for measuring a rate of a chemical reaction between a component of a liquid sample and a reagent, the reaction producing an electroactive species, comprising:

providing an electrochemical cell having a working electrode, a counter electrode, and at least one wall;

substantially immobilizing the reagent in the electrochemical cell at a site at a minimum distance from the working electrode, wherein the site and the working electrode are situated on the same plane, wherein the distance is such that transfer of the electroactive species from the site to the working electrode is diffusion controlled;

placing the liquid sample in the electrochemical cell such that the liquid sample is in contact with the reagent, the working electrode, and the counter electrode;

reacting the component with the reagent to produce the electroactive species;

applying a potential between the working electrode and the counter electrode, wherein the potential is sufficient to electrochemically react the electroactive species at the working electrode; and

measuring the current produced by the electrochemical reaction at the working electrode to obtain a measure of the rate of the chemical reaction.

34. A method for measuring a rate of a chemical reaction between glucose and PQQ dependent glucose dehydrogenase in whole blood comprising:

providing an electrochemical cell having a working electrode, a counter electrode, at least one wall, a redox mediator comprising ferricyanide and contained within the electrochemical cell, and a reagent comprising PQQ dependent glucose dehydrogenase, the reagent being substantially immobilized in the electrochemical cell at a site at a minimum distance from the working electrode, wherein the site is situated on the counter electrode;

placing the whole blood sample in the electrochemical cell such that the sample is in contact with the reagent, the redox mediator, the working electrode, and the counter electrode;

reacting the glucose with the PQQ dependent glucose dehydrogenase to produce reduced PQQ dependent glucose dehydrogenase, the reduced PQQ dependent glucose dehydrogenase in turn reacting with the ferricyanide redox mediator to form ferrocyanide;

applying a potential between the working electrode and the counter electrode, wherein the potential is sufficient to electrochemically react the ferrocyanide at the working electrode; and

measuring the current produced by the electrochemical reaction of ferrocyanide at the working electrode, wherein the measurement is indicative of the rate of the chemical reaction between glucose and PQQ dependent glucose dehydrogenase.

35. A method for measuring a rate of a chemical reaction between a component of a liquid sample and a reagent, the reaction producing an electroactive species, comprising:

providing an electrochemical cell having a working electrode, a counter electrode, and at least one wall;

substantially immobilizing the reagent in the electrochemical cell at a site at a minimum distance from the working electrode, wherein the site and the working electrode are situated on the same plane, and wherein the distance is such that transfer of the electroactive species from the site to the working electrode is diffusion controlled;

placing the liquid sample in the electrochemical cell such that the liquid sample is in contact with the reagent, the working electrode, and the counter electrode;

reacting the component with the reagent to produce the electroactive species;

applying a potential between the working electrode and the counter electrode, wherein the potential is sufficient to electrochemically react the electroactive species at the working electrode; and

measuring the current produced by the electrochemical reaction at the working electrode to obtain a measure of the rate of the chemical reaction.