Electrochemical Analyte Detection Apparatus and Method

• US 20090026075A1
• Filed: 07/24/2008
• Published: 01/29/2009
• Est. Priority Date: 07/26/2007
• Status: Abandoned Application

• Current Assignee: Agamatrix Incorporated (AgaMatrix Holdings LLC d/b/a WaveForm Diabetes)
• Original Assignee: Agamatrix Incorporated (AgaMatrix Holdings LLC d/b/a WaveForm Diabetes)
• Inventors: Harding, Ian, Williams, Richard, Iyengar, Sridhar
• Application Number:
  US12/179,446
• Publication Number:
  US 20090026075A1
• Time in Patent Office: Days
• US Class Current: 204/403.140
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: G01N 2333/90 Enzymes; Proenzymes
• CPC Class Codes: G01N 2333/902 Oxidoreductases (1.)
• CPC Class Codes: G01N 27/4166 measuring a particular property of an electrolyte
• CPC Class Codes: G01N 33/5438 Electrodes
• CPC Class Codes: G01N 33/573 for enzymes or isoenzymes

Abstract

A method and apparatus for electrochemical detection of analyte in a sample makes use of a binding interaction and relies on the discovery that asymmetric distribution of a redox enzyme between two electrodes that occurs when a redox enzyme-containing reagent is immobilized at the surface of one electrode can be detected as a chemical potential gradient arising from an asymmetry, in the distribution of oxidized or reduced redox substrate. This chemical potential gradient can be detected potentiometrically by observing the potential difference between the electrodes in an open circuit, or amperometrically by observing the current flow between the electrodes when the circuit is closed. In both cases, the observation of asymmetry can be done without the application of an external potential or current to the electrodes.

Claims

1. A method for determining an analyte in a sample, comprising the steps of:

(a) introducing the sample to a test cell comprising first and second electrodes, a mobile test reagent comprising a redox enzyme portion, and reagents that interact with the mobile test reagent and/or the analyte, such that the mobile test reagent has a first distribution relative to the electrodes when analyte is present in the sample and a second distribution relative to the electrodes when analyte is not present sample, one of said first and second distributions being asymmetric with respect to a line between the electrodes, and the other of the first and second distributions being symmetric or less asymmetric with respect to the line between the electrodes,

(b) supplying a redox substrate for the redox enzyme in the test cell, said redox substrate being acted upon by the redox enzyme to produce a chemical potential gradient between the first and second electrodes, wherein the magnitude of the chemical potential gradient is determined by the distribution of the mobile test reagent and thus on the presence of analyte, and

(c) detecting the chemical potential gradient between the first and second electrodes to determine analyte in the sample, wherein the formation and detection of the chemical potential gradient are performed without application of an external potential or current.

2. The method of claim 1, wherein

the test cell comprises as one of the reagents that interact with the analyte an immobilized test reagent disposed on the surface of the first electrode, said immobilized test reagent comprising an analyte binding portion, and

the mobile test reagent comprises an analyte-binding portion and the redox enzyme portion,

whereby if analyte is present in the sample in the test cell, at least a portion of the mobile test reagent becomes immobilized on the first electrode thereby creating an asymmetric distribution of redox enzyme concentration between the first and second electrodes when analyte is present.

3. The method of claim 2, wherein the analyte binding portion of the immobilized test reagent and the analyte are an antibody-antigen pair or antibody/hapten pair.

4. The method of claim 3, wherein the redox enzyme and the redox substrate comprises glucose and a mediator compound.

5. The method of claim 2, wherein the analyte binding portion of the immobilized test reagent is a drug receptor.

6. The method of claim 5, wherein the redox enzyme and the redox substrate comprises glucose and a mediator compound.

7. The method of claim 2, wherein the analyte binding portion of the immobilized test reagent is a hormone receptor.

8. The method of claim 7, wherein the redox enzyme and the redox substrate comprises glucose and a mediator compound.

9. The method of claim 1, wherein the analyte binding portion of the immobilized test reagent and the analyte are an antibody-antigen pair or antibody/hapten pair.

10. The method of claim 9, wherein the redox enzyme and the redox substrate comprises glucose and a mediator compound.

11. The method of claim 1 wherein the analyte binding portion of the immobilized test reagent is a drug receptor.

12. The method of claim 11, wherein the redox enzyme and the redox substrate comprises glucose and a mediator compound.

13. The method of claim 1, wherein the analyte binding portion of the immobilized test reagent is a hormone receptor.

14. The method of claim 13, wherein the redox enzyme and the redox substrate comprises glucose and a mediator compound.

15. An apparatus for determining an analyte in a sample comprising

a test strip comprising first and second electrodes disposed to contact a test cell for receiving sample, said test strip further a mobile test reagent comprising a redox enzyme portion, and reagents that interact with the mobile test reagent and/or the analyte, such that the mobile test reagent has a first distribution relative to the electrodes when analyte is present in the sample and a second distribution relative to the electrodes when analyte is not present sample, one of said first and second distributions being asymmetric with respect to a line between the electrodes, and the other of the first and second distributions being symmetric or less asymmetric with respect to the line between the electrodes, and

a circuit for detecting the symmetric or asymmetric distribution of the mobile test reagent in the test cell in the absence of an applied external potential or current,

and means for communicating the detected distribution to a user.

16. The apparatus of claim 15, wherein the circuit detects the potential difference between the first and second electrode.

17. The apparatus of claim 15, wherein the circuit detects current flow in a circuit including the electrodes.

18. The apparatus of claim 15, wherein the first and second electrodes are in a facing configuration.

19. The apparatus of claim 15, wherein the first and second electrodes are in a side-by-side configuration.

20. The apparatus in accordance with claim 15, wherein,

the test cell comprises as one of the reagents that interact with the analyte an immobilized test reagent disposed on the surface of the first electrode, said immobilized test reagent comprising an analyte binding portion, and

the mobile test reagent comprises an analyte-binding portion and the redox enzyme portion,

whereby if analyte is present in the sample in the test cell, at least a portion of the mobile test reagent becomes immobilized on the first electrode thereby creating an asymmetric distribution of redox enzyme concentration between the first and second electrodes when analyte is present.

21. The apparatus of claim 15, wherein the analyte binding portion of the immobilized test reagent and the analyte are an antibody-antigen pair or antibody/hapten pair.

22. The apparatus of claim 15, wherein the analyte binding portion of the immobilized test reagent is a drug receptor.

23. The apparatus of claim 15, wherein the analyte binding portion of the immobilized test reagent is a hormone receptor.

24. The apparatus of claim 15, wherein the redox enzyme and the redox substrate comprises glucose and a mediator compound.