Biosensor electrode mediators for regeneration of cofactors

• US 20040197935A1
• Filed: 04/26/2004
• Published: 10/07/2004
• Est. Priority Date: 10/16/1997
• Status: Active Grant

• Current Assignee: Abbott Diabetes Care Incorporated (Abbott Laboratories Incorporated)
• Original Assignee: Abbott Laboratories Incorporated
• Inventors: Forrow, Nigel J., Watkin, Jared L., Sanghera, Gurdial S., Walters, Stephen
• Granted Patent: US 7,504,019 B2
• Time in Patent Office: Days
• US Class Current: 436/518
• CPC Class Codes: C12Q 1/004 mediator-assisted
• CPC Class Codes: C12Q 1/005 involving specific analytes or enzymes including groups of enzymes, e.g. oxydases; C12Q1/004 takes precedence
• 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: Y10T 29/49155 Manufacturing circuit on or in base

Abstract

The present invention is based on the discovery of NAD⁺ and NADP⁺ mediator compounds that do not bind irreversibly to thiol groups in the active sites of intracellular dehydrogenase enzymes. Such mediator compounds avoid a common mode of enzyme inhibition. The mediators can therefore increase the stability and reliability of the electrical response in amperometric electrodes constructed from NAD- or NADP-dependent enzymes.

Claims

1. A single use disposable electrode strip for attachment to the signal readout circuitry of a sensor system to detect a current representative of an analyte in an aqueous sample, the strip comprising:

a) an elongated support having a substantially flat, planar surface, adapted for releasable attachment to said readout circuitry;

b) a first conductor extending along said surface and comprising a conductive element for connection to said readout circuitry;

 

an active electrode on said surface in contact with said first conductor, said active electrode comprising a nicotinamide co-factor-dependent enzyme, a nicotinamide cofactor, and a mediator compound having one of the two following formulae;

 

where X and Y can independently be oxygen, sulphur, CR³R⁴, NR³, or NR³R⁴ or the functional group CZ¹Z², where Z¹ and Z² are electron withdrawing groups;

R₁ and R₂ can independently be a substituted or unsubstituted aromatic or heteroaromatic group; and

R³ and R⁴ can independently be a hydrogen atom, a hydroxyl group or a substituted or unsubstituted alkyl, aryl, heteroaryl, amino, alkoxyl, or aryloxyl group

c) a second conductor extending along said surface, comprising a conductive element for connection to said readout circuitry;

d) a reference/counter electrode in contact with said second conductor;

e) a third conductor extending along said surface, comprising a conductive element for connection to readout circuitry;

f) a fill indicator electrode in contact with said third conductor;

g) said conductors being spaced apart so as not to be in electrical contact and being configured so as not to be brought into electrical contact when said aqueous sample is placed on said strip;

h) said active electrode and said reference/counter electrode being configured so that both may be simultaneously covered by a small drop of said aqueous sample to provide an electrical conduction path between said electrodes.

2. The electrode strip of claim 1 wherein the mediator compound is 1,10-phenantholine quinone.

3. The electrode strip of claim 2 wherein the cofactor-dependent enzyme is Glucose Dehydrogenase.

4. The electrode strip of claim 1 wherein the cofactor-dependent enzyme is 3-Hydroxybutyrate Dehydrogenase.

5. A process of measuring the concentration in an aqueous sample of an analyte subject to oxidation by a NAD(P)⁺ dependent enzyme comprising:

a) providing the electrode strip of claim 1;

b) applying the sample containing the analyte to the electrode strip;

c) detecting the sample applied to the electrode strip;

d) oxidizing the analyte with the NAD(P)⁺ dependent enzyme in the presence of NAD(P)⁺;

oxidizing the NAD(P)H generated by reaction with the analyte and NAD(P)⁺ dependent enzyme with the mediator compound of step a); and

e) applying an electrical potential at an electrode to reoxidize the mediator compound reduced in oxidizing NAD(P)H and observing the resultant current.

6. The process of claim 5 wherein the NAD(P)⁺ dependent enzyme, NAD(P)⁺, and mediator compound have been applied to the surface of said electrode in combination with a binder and a filler.

7. The process of claim 6 wherein the current observed during the measurement period is linearly related to the concentration of the analyte in the sample.

8. The process of claim 5 wherein the mediator is 1,10-phenanthroline quinone.

9. The process of claim 8 wherein the cofactor-dependent enzyme is Glucose Dehydrogenase.

10. The process of claim 8 wherein the cofactor dependent enzyme is 3-Hydroxybutyrate Dehydrogenase.

11. The process of claim 5 wherein the applied potential is 200 mV or less.

12. The process of claim 5, wherein the current is linearly related to the concentration of the analyte.

13. The electrode strip of claim 1, wherein the mediator is 4,7-phenanthroline quinone.

14. The electrode strip of claim 1, wherein the mediator is 1,7-phenanthroline quinone.

15. The electrode strip of claim 1, further including a dummy electrode.

16. The electrode strip of claim 1, further including circuit loops for providing a resistance characteristic of the electrode strip to identify the test strip as being suitable for a particular analyte.

17. The electrode strip of claim 1, further including at least one notch or other shape in an end of the test strip to identify the test strip as being suitable for a particular analyte.

18. The electrode strip of claim 1, further including at least one switch to identify the test strip as being suitable for a particular analyte.

19. The electrode strip of claim 1, further including at least one optical detector to identify the test strip as being suitable for a particular analyte.

20. A single use disposable electrode strip for attachment to the signal readout circuitry of a sensor system to detect a current representative of an analyte in an aqueous sample, the strip comprising:

a) an elongated support having a substantially flat, planar surface, adapted for releasable attachment to said readout circuitry;

b) a first conductor extending along said surface and comprising a conductive element for connection to said readout circuitry;

c) an active electrode on said surface in contact with said first conductor;

d) a second conductor extending along said surface, comprising a conductive element for connection to said readout circuitry;

e) a reference/counter electrode in contact with said second conductor;

f) a third conductor extending along said surface, comprising a conductive element for connection to readout circuitry;

g) a fill indicator electrode in contact with said third conductor;

h) said conductors being spaced apart so as not to be in electrical contact and being configured so as not to be brought into electrical contact when said aqueous sample is placed on said strip;

i) said active electrode and said reference/counter electrode being configured so that both may be simultaneously covered by a small drop of said aqueous sample to provide an electrical conduction path between said electrodes.

21. The electrode strip of claim 20, further including circuit loops for providing a resistance characteristic of the electrode strip to identify the test strip as being suitable for a particular analyte.

22. The electrode strip of claim 20, further including at least one notch or other shape in an end of the test strip to identify the test strip as being suitable for a particular analyte.

23. The electrode strip of claim 20, further including at least one switch to identify the test strip as being suitable for a particular analyte.

24. The electrode strip of claim 20, further including at least one optical detector to identify the test strip as being suitable for a particular analyte.