Method for measuring the concentration or change in concentration of a redox-active substance and corresponding device

• US 20080099347A1
• Filed: 01/26/2005
• Published: 05/01/2008
• Est. Priority Date: 01/29/2004
• Status: Active Grant

• Current Assignee: Boehringer Ingelheim Vetmedica GmbH (C.H. Boehringer Sohn AG & Co. KG)
• Original Assignee: Siemens AG
• Inventors: Gumbrecht, Walter, Barlag, Heike, Mund, Konrad
• Granted Patent: US 8,105,478 B2
• Time in Patent Office: Days
• US Class Current: 205/793.5
• CPC Class Codes: G01N 2333/916 acting on ester bonds (3.1), e.g. phosphatases (3.1.3), phospholipases C or phospholipases D (3.1.4)
• CPC Class Codes: G01N 27/3277 being a redox reaction, e.g. detection by cyclic voltammetry voltammetry per se G01N27/42, G01N27/48
• CPC Class Codes: Y10T 436/143333 Saccharide [e.g., DNA, etc.]

Abstract

In order to follow the change in concentration of a redox-active substance, potential suitable for a reducing process or oxidation process are applied to the working electrode of a measuring device. The potential of the working electrode is pulsed and measuring phases and relaxation phases are alternately produced, the pulse lengths of the measuring phase and relaxation phase being predetermined in a suitable manner. In this manner, a rapid relaxation of the concentration gradient is forced electrochemically so that the measurement can be carried out on simple transducer arrays. The device includes a transducer array in addition to a suitable potentiostat. The transducer array may include a planar metal substrate on which at least one flexible insulator having a firm connection between the metal surface and the insulator surface is located. The array is generated by suitably structuring the substrate.

Claims

1. Method for selecting pulse lengths for measuring the at least one of a concentration and change in concentration of a redox-active substance as a mediator in a molecular-biological detection system, in which as a result of application of suitable potentials to a working electrode, at least one of a reduction process and an oxidation process takes place as a redox reaction, the method comprising:

pulsing the potential of the working electrode and alternately forming measuring phases and relaxation phases;

selecting, in this connection, the measuring-phase pulse lengths so that, towards the end of the pulse, the capacitive current is relatively small in comparison with the Faraday current; and

selecting the relaxation-phase pulse lengths so that, towards the end of the pulse, the concentration gradient is relaxed so that at the beginning of a following measuring phase, the change in concentration of the mediator, brought about by the consumption of the mediator by the measurement itself, is reversible to the greatest possible extent.

2. Method according to claim 1, wherein a current, measurable at the end of the measuring phase, forms the measuring signal.

3. Method according to claim 1, wherein, when measuring oxidation currents, an adequate reduction potential is set during the relaxation phase and the species oxidized during the measuring phase and still located in front of the electrode are reduced again pulsed redox-cycling).

4. Method according to claim 1, wherein, when measuring reduction currents, an adequate oxidation potential is set during the relaxation phase and the species reduced during the measuring phase and still located in front of the electrode are oxidized again pulsed redox-cycling).

5. Method according to claim 3 wherein the repetition rate for the pulsed redox-cycling amounts to at least 1/10 Hz.

6. Method according to claim 3, wherein the pulsed redox-cycling is carried out with predeterminable pulse shapes.

7. Method according to claim 1, wherein the relaxation phase is at least as long as the measuring phase.

8. Method according to claim 7, wherein the relaxation phase is considerably longer than the measuring phase.

9. Method according to claim 8, wherein,—

with a repetition rate of 1 Hz, the pulse lengths of the measuring phases amount to 100 to 300 ms, and the relaxation phase amounts to between 700 and 900 ms.

10. Method according to claim 1, wherein the potentials are selected so that the reactions occur in the diffusion limiting current range.

11. Device for carrying out the measuring method according to claim 1, comprising:

a facility for producing potentials that are determinable with respect to time and are variable electrically; and

a transducer array.

12. Device according to claim 11, wherein the transducer array comprises at least one flexible planar metal substrate, arranged on which there is at least one flexible insulator with a fixed connection between the metal surface and insulator surface, with the metal substrate being structured in such a way that metal regions exist that are electrically insulated from each other, and with the insulator that is located on the metal substrate being structured in such a way that cavities with open metal surfaces are defined in the insulator, with the metal regions being contactable from the side that is remote from or lies opposite the sensor area.

13. Device according to claim 11, wherein the transducer array comprises areal electrodes, whose smallest extent is relatively greater than typical diffusion lengths.

14. Device according to claim 13, wherein the areal electrodes have an extent of at least 30 μ

m preferably 50 μ

m.

15. Device according to claim 14, the areal electrodes are formed using thin-film technology on a non-conductive, rigid substrate.

16. Device according to claim 15, wherein the rigid substrate is silicon.

17. Device according to claim 16, wherein an insulator is provided on the substrate.

18. Device according to claim 11, wherein the facility for producing predeterminable electric potentials is a potentiostat.

19. Device according to claim 18, wherein associated with the potentiostat for producing pulsed electric potentials there is a pulse generator.

20. Device according to claim 19, wherein operational amplifiers and a defined measuring resistor are provided in the potentiostat.

21. Method according to claim 3, wherein the repetition rate for the pulsed redox-cycling amounts to at least 1/10 Hz.

22. Method according to claim 6, wherein the pulsed redox-cycling is carried out with at least one of a rectangular, triangular and sinusoidal course.

23. Method according to claim 4, wherein the pulsed redox-cycling is carried out with predeterminable pulse shapes.

24. Method according to claim 23, wherein the pulsed redox-cycling is carried out with at least one of a rectangular, triangular and sinusoidal course.

25. Method according to claim 8, wherein, with a repetition rate of 1 Hz, the pulse lengths of the measuring phases amount to 250 ms, and the relaxation phase amounts to 750 ms.

28. Method according to claim 1, further comprising:

measuring at least one of a concentration and change in concentration of a redox-active substance as a mediator, in a molecular-biological detection system, using the selected pulse lengths.

26. Device for selecting pulse lengths for measuring at least one of a concentration and change in concentration of a redox-active substance as a mediator in a molecular-biological detection system, in which as a result of application of suitable potentials to a working electrode, at least one of a reduction process and an oxidation process takes place as a redox reaction, the device comprising:

means for pulsing the potential of the working electrode, and alternately forming measuring phases and relaxation phases;

means for selecting, in this connection, the measuring-phase pulse lengths so that, towards the end of the pulse, the capacitive current is relatively small in comparison with the Faraday current; and

means for selecting the relaxation-phase pulse lengths so that, towards the end of the pulse, the concentration gradient is relaxed so that at the beginning of a following measuring phase, the change in concentration of the mediator, brought about by the consumption of the mediator by the measurement itself, is reversible to the greatest possible extent.

27. Device according to claim 26, further comprising:

means for measuring at least one of a concentration and change in concentration of a redox-active substance as a mediator, in a molecular-biological detection system, using the selected pulse lengths.