Potentiometric biosensor and the method of its use

• US 5,413,690 A
• Filed: 07/23/1993
• Issued: 05/09/1995
• Est. Priority Date: 07/23/1993
• Status: Expired due to Term

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Boehringer Mannheim Corporation
• Inventors: Lindsay, Thomas J., Price, John F., Kost, Kent M.
• Primary Examiner(s): Gorgos, Kathryn
• Assistant Examiner(s): Bell, Bruce F.
• Application Number:
  US08/097,331
• Time in Patent Office: 655 Days
• Field of Search: 204/403, 204/412, 204/418, 204/435, 204/433, 435/817, 435/288, 435/291
• US Class Current: 205/777.5
• CPC Class Codes: C12Q 1/004 mediator-assisted
• CPC Class Codes: Y10S 435/817 Enzyme or microbe electrode

Abstract

A potentiometric biosensor, test strip, reagent and a potentiometric method for detection or measurement of an analyte from a fluid sample. The biosensor includes indicating and reference electrodes, and a reagent, which overlays a portion of the surface of the indicating electrode. The reagent generally includes an enzyme and a redox mediator. When a fluid sample (e.g., blood) containing an analyte (e.g., glucose) is added to the reagent, the enzyme (e.g., glucose oxidase) catalyzes a reaction involving enzyme, redox mediator (e.g., potassium ferricyanide), and analyte.

This reaction may be monitored by monitoring the electrical potential at the indicating electrode surface. (Electrical potential at the indicating electrode surface changes as the concentration of oxidized and reduced forms of the redox mediator change at the indicating electrode surface.) The inventive potentiometric biosensor measures the change in potential at the indicating electrode surface after the fluid sample containing the analyte is added to the reagent. The change in potential that occurs may be correlated to the detection or measurement of analyte in the fluid sample.

Claims

1. A potentiometric biosensor for analysis of an analyte from a fluid sample, comprising:

a. an indicating electrode;

b. a reference electrode;

c. a reagent of known amount overlaying a portion of the surface of the indicating electrode and comprising a redox mediator,

the redox mediator being in an amount to react with all of the analyte at the surface of the indicating electrode, thereby causing a measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode; and

d. a potentiometer in electrical connection with the indicating and reference electrodes.

4. A potentiometric method of detecting an analyte from a fluid sample, comprising the steps of:

a. forming a test sample by adding the fluid sample to the potentiometric biosensor of claim 1, wherein the reagent is fully exposed to the fluid sample and the fluid sample contacts both the indicating and the reference electrodes, thereby forming a circuit;

b. incubating the test sample to produce the measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode;

c. measuring potential after incubation; and

d. correlating the measured potential to detection of the analyte.

2. A potentiometric biosensor, comprising:

a. an indicating electrode;

b. a reference electrode;

c. a reagent of known amount overlaying a portion of the surface of the indicating electrode and comprising a catalyst and a redox mediator,

the catalyst being in an amount to catalyze a reaction involving the catalyst, the redox mediator, and an analyte from a fluid sample,

the redox mediator being in an amount to react with all of the analyte at the surface of the indicating electrode, thereby causing a measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode; and

d. a potentiometer in electrical connection with the indicating and reference electrodes.

6. A potentiometric method of detecting an analyte from a fluid sample, comprising the steps of:

a. forming a test sample by adding the fluid sample to the potentiometric biosensor of claim 2, wherein the reagent is fully exposed to the fluid sample and the fluid sample contacts both the indicating and the reference electrodes, thereby forming a circuit;

b. incubating the test sample to produce the measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode;

c. measuring potential after incubation; and

d. correlating the measured potential to detection of the analyte.

3. A potentiometric biosensor, comprising:

a. an indicating electrode;

b. a reference electrode;

c. a reagent of known amount overlaying a portion of the surface of the indicating electrode and comprising an enzyme and a redox mediator,

the enzyme being in an amount to catalyze a reaction involving the enzyme, the redox mediator, and an analyte from a fluid sample,

the redox mediator being in an amount to react with all of the analyte at the surface of the indicating electrode, thereby causing a measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode; and

d. a potentiometer in electrical connection with the indicating and reference electrodes.

10. A potentiometric method of measuring an analyte from a fluid sample, comprising the steps of:

a. forming a test sample by adding the fluid sample to the potentiometric biosensor of claim 3, wherein the reagent is fully exposed to the fluid sample and the fluid sample contacts both the indicating and reference electrodes, thereby forming a circuit;

b. incubating the test sample to produce the measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode;

c. measuring potential after incubation; and

d. correlating the measured potential to the amount of the analyte in the fluid sample.

5. A potentiometric method of measuring an analyte from a fluid sample, comprising the steps of:

a. forming a test sample by adding the fluid sample to a potentiometric biosensor including,

1) a first electrical insulator,.

2) indicating and reference electrodes supported on the first electrical insulator,

3) a second electrical insulator, overlaying the first electrical insulator and the electrodes and including a cutout portion that exposes surface areas of the indicating and reference electrodes,

4) a reagent of known amount overlaying the exposed surface of the indicating electrode in the cutout portion and comprising a redox mediator,

the redox mediator being in sufficient amount to react with all of the analyte at the surface of the indicating electrode, thereby causing a measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode, and

5) a potentiometer in electrical connection with the indicating and reference electrodes,

wherein the reagent is fully exposed to the fluid sample and the fluid sample contacts both the indicating and reference electrodes, thereby forming a circuit;

b. incubating the test sample to produce the measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode;

c. measuring potential after incubation; and

d. correlating the measured potential to the amount of the analyte in the fluid sample.

7. A potentiometric method of measuring an analyte from a fluid sample, comprising the steps of:

a. forming a test sample by adding the fluid sample to a potentiometric biosensor including,

1) a first electrical insulator,

2) indicating and reference electrodes supported on the first electrical insulator,

3) a second electrical insulator, overlaying the first electrical insulator and the electrodes and including a cutout portion that exposes surface areas of the indicating and reference electrodes,

4) a reagent of known amount overlaying the exposed surface of the indicating electrode in the cutout portion and comprising a catalyst, a buffer, and a redox mediator,

the catalyst being in an amount to catalyze a reaction involving the catalyst, the redox mediator, and an analyte from the fluid sample,

the buffer being in an amount to provide and maintain a pH at which the catalyst catalyzes the reaction involving the catalyst, the redox mediator, and the analyte,

the redox mediator being in an amount to react with all of the analyte at the surface of the indicating electrode, thereby causing a measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode, and

5) a potentiometer in electrical connection with the indicating and reference electrodes,

wherein the reagent is fully exposed to the fluid sample and the fluid sample contacts both the indicating and reference electrodes, thereby forming a circuit;

b. incubating the test sample to produce the measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode;

c. measuring potential after incubation; and

d. correlating the measured potential to the amount of the analyte in the fluid sample.

8. A potentiometric method of detecting an analyte from a fluid sample, comprising the steps of:

a. forming a test sample by adding the fluid sample to a potentiometric biosensor including,

1) a first electrical insulator,

2) indicating and reference electrodes supported on the first electrical insulator,

3) a second electrical insulator, overlaying the first electrical insulator and the electrodes and including a cutout portion that exposes surface areas of the indicating and reference electrodes,

4) a reagent of known amount overlaying the exposed surface of the indicating electrode in the cutout portion and comprising an enzyme, a buffer, and a redox mediator,

the enzyme being in an amount to catalyze a reaction involving the enzyme, the redox mediator, and an analyte from the fluid sample,

the buffer being in an amount to provide and. maintain a pH at which the enzyme catalyzes the reaction involving the enzyme, the redox mediator, and the analyte,

the redox mediator being in an amount to react with all of the analyte at the surface of the indicating electrode, thereby causing a measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode, and

5) a potentiometer in electrical connection with the indicating and reference

wherein the reagent is fully exposed to the fluid sample and the fluid sample contacts both the indicating and reference electrodes, thereby forming a circuit;

b. incubating the test sample to produce the measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode;

c. measuring potential after incubation; and

d. correlating the measured potential to the detection of the analyte.

9. A potentiometric method of measuring an analyte from a fluid sample, comprising the steps of:

a. forming a test sample by adding the fluid sample to a potentiometric biosensor including,

1) a first electrical insulator,

2) indicating and reference electrodes supported on the first electrical insulator,

3) a second electrical insulator, overlaying the first electrical insulator and the electrodes and including a cutout portion that exposes surface areas of the indicating and reference electrodes,

4) a reagent of known amount overlaying the exposed surface of the indicating electrode in the cutout portion and comprising an enzyme, a buffer, and a redox mediator,

the enzyme being in an amount to catalyze reaction involving the enzyme, the redox mediator, and an analyte from the fluid sample,

the buffer being in an amount to provide and maintain a pH at which the enzyme catalyzes the reaction involving the enzyme, the redox mediator, and the analyte,

the redox mediator being in an amount to react with all of the analyte at the surface of the indicating electrode, thereby causing a measurable change in potential that correlates to the change in proportions of the and reduced forms of the redox mediator at the surface of the indicating electrode, and

5) a potentiometer in electrical connection with the indicating and reference electrodes,

wherein the reagent is fully exposed to the fluid sample and the fluid sample contacts both the indicating and reference electrodes, thereby forming a circuit;

b. incubating the test sample to produce the measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode;

c. measuring potential after incubation; and

d. correlating the measured potential to the amount of the analyte in the fluid sample.

11. A potentiometric biosensor for analysis of an analyte from a fluid sample, comprising:

a. a first electrical insulator;

b. indicating and reference electrodes supported on the first electrical insulator;

c. a second electrical insulator, overlaying the first electrical insulator and the electrodes and including a cutout portion that exposes surface areas of the indicating and reference electrodes;

d. a reagent of known amount overlaying the exposed surface of the indicating electrode in the cutout portion and comprising a redox mediator,

the redox mediator being in an amount to react with all of the analyte at the surface of the indicating electrode, thereby causing a measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode; and

e. a potentiometer in electrical connection with the indicating and reference electrodes.

12. The potentiometric biosensor of claim 11, wherein the reagent further comprises a dispersant and crystallization inhibitor and a thickener.

13. A potentiometric biosensor, comprising:

a. a first electrical insulator;

b. indicating and reference electrodes supported on the first electrical insulator;

c. a second electrical insulator, overlaying the first electrical insulator and the electrodes and including a cutout portion that exposes surface areas of the indicating and reference electrodes;

d. a reagent of known amount overlaying the exposed surface of the indicating electrode in the cutout portion and comprising a catalyst and a redox mediator,

the catalyst being in an amount to catalyze a reaction involving the catalyst, the redox mediator, and an analyte from a fluid sample,

the redox mediator being in an amount to react with all of the analyte at the surface of the indicating electrode, thereby causing a measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode; and

e. a potentiometer in electrical connection with the indicating and reference electrodes.

14. The potentiometric biosensor of claim 13, wherein the reagent further comprises a buffer in sufficient amount to provide and maintain a pH at which the catalyst catalyzes the reaction involving the catalyst, the redox mediator, and the analyte.

15. A potentiometric biosensor, comprising:

a. a first electrical insulator;

b. indicating and reference electrodes supported on the first electrical insulator;

c. a second electrical insulator, overlaying the first electrical insulator and the electrodes and including a cutout portion that exposes surface areas of the indicating and reference electrodes;

d. a reagent of known amount overlaying the exposed surface of the indicating electrode in the cutout portion and comprising an enzyme and a redox mediator,

the enzyme being in an amount to catalyze a reaction involving the enzyme, the redox mediator, and an analyte from a fluid sample,

the redox mediator being in an amount to react with all of the analyte at the surface of the indicating electrode, thereby causing a measurable change in potential that correlates to the change in proportions of the oxidized and reduced forms of the redox mediator at the surface of the indicating electrode; and

e. a potentiometer in electrical connection with the indicating and reference electrodes.

16. The potentiometric biosensor of claim 15, wherein the reagent further comprises a buffer in an amount to provide and maintain a pH at which the enzyme catalyzes the reaction involving the enzyme, the redox mediator, and the analyte.

17. The potentiometric biosensor of claim 15, wherein the indicating electrode is selected from a group consisting of palladium, platinum, gold, silver, titanium, copper, and carbon.