Concentration Measuring Method, Concentration Test Instrument, and Concentration Measuring Apparatus

• US 20040245121A1
• Filed: 03/12/2004
• Published: 12/09/2004
• Est. Priority Date: 09/14/2001
• Status: Active Grant

• Current Assignee: ARKRAY, Inc
• Original Assignee: ARKRAY, Inc
• Inventors: Yamaoka, Hideaki, Nagakawa, Kenji
• Granted Patent: US 7,390,391 B2
• Time in Patent Office: Days
• US Class Current: 205/777.5
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: C12Q 1/004 mediator-assisted
• 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

Abstract

The present invention relates to technology for constructing a reaction system including a test target, an oxidation-reduction enzyme, and an electron mediator, and measuring the concentration of the test target by an electrochemical process. A Ru compound is used as the electron mediator. The present invention provides a concentration test instrument including a substrate, first and second electrodes formed on the substrate, and a reagent layer formed as a solid. The reagent layer contains an oxidation-reduction enzyme and a Ru compound, and is constituted so as to dissolve and construct a liquid phase reaction system when a sample liquid is supplied.

Claims

1. A method for measuring a concentration of a test target, the method comprising:

constructing a reaction system containing the test target, an oxidation-reduction enzyme and an electron mediator;

measuring the concentration of the test target by utilizing an electrochemical process;

wherein a Ru compound is used as the electron mediator.

2. The method according to claim 1, further comprising:

a first step of producing a reductant of the Ru compound in the reaction system;

a second step of applying voltage to the reaction system to oxidize the reductant, and measuring the response current value correlated with a quantity of electrons released by the reductant; and

a third step of computing the concentration of the test target on the basis of the response current value measured in the second step.

3. The method according to claim 2, wherein the Ru compound is an oxidative Ru(III) complex, and the reductant of the compound is a reductive Ru(II) complex.

4. The method according to claim 3, wherein the oxidative Ru(III) complex is expressed by the following chemical formula:

[Ru(NH₃)X]ⁿ⁺

(where X in the formula is NH₃ or a halogen ion, and n+ in the formula is the valence of the oxidative Ru(III) complex as determined by a type of X).

5. The method according to claim 3, wherein in the first step the reductive Ru(II) complex is produced by only two reactions:

an oxidation reaction of the test target catalyzed by the oxidation-reduction enzyme, and a reduction reaction of the oxidative Ru(III) complex.

6. The method according to claim 3, wherein the reaction system is a uniform or substantially uniform liquid phase reaction system in which a relatively small amount of the oxidation-reduction enzyme is dispersed substantially uniformly with respect to a relatively large amount of the oxidative Ru (III) complex.

7. The method according to claim 1, wherein the test target is glucose.

8. A concentration test instrument comprising:

a substrate;

at least first and second electrodes formed on the substrate; and

a reagent layer formed as a solid;

wherein the reagent layer comprises an oxidation-reduction enzyme and a Ru compound, and is constituted so as to dissolve and construct a liquid phase reaction system when a sample liquid containing the test target is supplied.

9. The concentration test instrument according to claim 8, wherein the reagent layer is constituted such that when the sample liquid is supplied, the oxidation-reduction enzyme and the Ru compound are present in the liquid phase reaction system.

10. The concentration test instrument according to claim 8, wherein the reagent layer contains the Ru compound as an oxidant, and is constituted such that when the sample liquid is supplied to the reagent layer, a reductant is produced from the oxidant by only two reactions:

an oxidation reaction of the test target catalyzed by the oxidation-reduction enzyme, and a reduction reaction of the Ru compound.

11. The concentration test instrument according to claim 10, wherein the reagent layer is constituted so that the reductant is produced substantially uniformly in every location of the liquid phase reaction system.

12. The concentration test instrument according to claim 8, wherein the Ru compound is expressed by the following chemical formula:

[Ru(NH₃)₅X]ⁿ⁺

(where X in the formula is NH₃ or a halogen ion, and n+ in the formula is the valence of the oxidative Ru(III) complex as determined by a type of X).

13. The concentration test instrument according to claim 8, wherein the test target is glucose.

14. The concentration test instrument according to claim 13, wherein the oxidation-reduction enzyme comprises at least one selected from the group consisting of PQQGDH, AGDH, and CyGDH.

15. A concentration measuring apparatus used together with a measurement test instrument which comprises a reagent layer, a first electrode and a second electrode, the reagent layer containing an oxidation-reduction enzyme and a Ru compound, the measuring apparatus comprising:

a voltage applier for applying voltage between the first and second electrodes;

a current value measurer for measuring the response current value when voltage is applied between the first and second electrodes; and

a computer for computing the concentration of the test target on the basis of the response current value.

16. The concentration measuring apparatus according to claim 15, further comprising a controller for controlling the voltage application performed by the voltage applier,

wherein the controller is constituted such that the voltage applied by the voltage applier is controlled to be a constant voltage selected from a range of 100 to 500 mV.

17. The concentration measuring apparatus according to claim 15, further comprising a controller for controlling the voltage application performed by the voltage applier,

wherein the controller is constituted such that the voltage applied by the voltage applier is controlled to be a constant voltage selected from a range of at least a standard oxidation-reduction potential (versus a standard hydrogen electrode) between the oxidant and reductant of the Ru compound, and less than a standard oxidation-reduction potential (versus a standard hydrogen electrode) between ferrocyanide ions and ferricyanide ions.

18. The concentration measuring apparatus according to claim 15, further comprising a controller for controlling the current value measurement performed by the current measurer,

wherein the controller is constituted such that the response current value necessary for computation by the computer is measured by the current value measurer at any point between 3 and 5 seconds after the sample liquid is supplied to the reagent layer.