ELECTROCHEMICAL BIOSENSOR ANALYSIS SYSTEM

• US 20090020439A1
• Filed: 07/22/2008
• Published: 01/22/2009
• Est. Priority Date: 01/25/2006
• Status: Active Grant

• Current Assignee: Roche Diabetes Care Inc. (Roche Holding AG)
• Original Assignee: Roche Diagnostics Operations Incorporated (Roche Holding AG)
• Inventors: Kotzan, Holger, Lungu, Mihail-Onoriu, Unkrig, Volker, Zapf, Udo, Marquant, Michael, Bainczyk, Gregor
• Granted Patent: US 8,357,274 B2
• Time in Patent Office: Days
• US Class Current: 205/792
• CPC Class Codes: C12Q 1/001 Enzyme electrodes
• CPC Class Codes: G01N 27/3273 Devices therefor, e.g. test element readers, circuitry details not specific to biochemical electrodes G01N33/4875
• CPC Class Codes: G01N 27/3274 Corrective measures, e.g. error detection, compensation for temperature or hematocrit, calibration coding of calibration information G01N33/48771

Abstract

An electrochemical biosensor analysis system is provided for analyzing a sample liquid, comprising a biosensor having an electrode structure made of at least two electrodes, a test field, covering the electrode structure and capable of absorbing the sample liquid, and a defined sample application surface on the top side of the test field. The system also includes an analysis instrument comprising an evaluation unit for determining the desired analysis data. The analysis instrument comprises an AC resistance measuring device for measuring an AC resistance value between two electrodes of the electrode structure by means of an area compensation measurement. The measured AC resistance value is used, in the determination of the analysis data, as a measure of the partial area of the effective electrode structure area wetted by the sample liquid.

Claims

1. An electrochemical biosensor analysis system for analyzing a sample liquid, comprising:

a biosensor comprising a carrier layer, an electrode structure located on the carrier layer and comprising at least two electrodes, a test field located on the carrier layer and covering the electrode structure, and comprising at least one layer of a material configured to absorb the sample liquid, the test field further comprising a reagent system configured to react with the sample liquid and to produce a change of an electrical measurement variable, said measurement variable being characteristic for a desired analysis result and measurable by means of an analysis measurement employing at least two of the electrodes, the biosensor further comprising a sample application surface on an upper side of the test field, facing generally away from the carrier layer, and

an analysis instrument comprising an analytical measuring device configured for measuring the measurement variable of a sample liquid on the biosensor when the biosensor is positioned in a measurement position and electrically connected to the measuring device, the instrument further comprising an evaluation unit configured for determining the desired analysis data from measured values of the measurement variable;

wherein

the electrode structure is distributed on an effective electrode structure area, which area is wettable by the sample liquid, the distribution of the electrode structure on the electrode structure area being generally homogeneous with respect to an AC resistance measurement performed on a liquid layer having a defined conductivity and layer thickness;

the test field is configured for spreading a droplet of sample liquid applied to the sample application surface over at least a partial area of the sample application surface and for wetting a corresponding area of the effective electrode structure area; and

the analysis instrument comprises an AC resistance measuring device configured for performing an area compensation measurement by measuring an AC resistance value between two electrodes of the electrode structure, the measured AC resistance value being used, in the determination of the analysis data, as a measure of the extent that the area of the effective electrode structure area is wetted by the sample liquid.

2. The analysis system according to claim 1, wherein the analysis instrument comprises a heating device configured for heating the test field of a biosensor positioned in the measurement position.

3. The analysis system according to claim 2, wherein the analysis instrument further comprises a temperature measuring device configured for measuring the temperature of the test field of a biosensor positioned in the measurement position.

4. The analysis system according to claim 3, wherein the analysis instrument further comprises thermostatic control electronics configured to provide thermostatic control of the test field temperature to a desired setpoint temperature, said electronics being operatively connected with the temperature measuring device and the heating device.

5. The analysis system according to claim 1, wherein the analysis instrument is configured to use AC resistance values for eliminating measurement errors caused by at least one of variations of concentrations of components in the sample liquid and changes in the temperature of the test field.

6. The analysis system according to claim 5, wherein a plurality of AC voltages with different frequencies are applied to the electrodes during the measurement of the AC resistance values.

7. The analysis system according to claim 1, wherein the biosensor comprises an elongate test strip having an insertion end configured for insertion into a holder of the analysis instrument, and a handling end opposite to the insertion end, the test field being located generally between the insertion end and the handling end.

8. The analysis system according to claim 1, wherein the analysis instrument comprises a holder configured for holding a biosensor in the measurement position and a biosensor support configured for supporting a biosensor inserted into the holder, the biosensor support generally protruding relative to adjacent portions of the analysis instrument.

9. The analysis system according to claim 1, wherein the biosensor comprises a component of a biosensor band comprising a plurality of biosensors connected to one another.

10. A biosensor for an analysis system, said biosensor comprising:

a carrier layer;

an electrode structure located on the carrier layer, the electrode structure comprising at least two electrodes;

a test field located on the carrier layer and generally covering the electrode structure, the test field being capable of absorbing a sample liquid applied to the biosensor and containing a reagent system configured to react with the sample liquid and to produce a change of an electrical measurement variable, said measurement variable being characteristic for a desired analysis result and measurable by means of an analysis measurement employing at least two of the electrodes, the test field further comprising a sample application surface on an upper side of the test field and facing generally away from the carrier layer;

wherein

two electrodes of the electrode structure are provided in an interdigitated array, each electrode comprising a primary conductor and a plurality of secondary conductors branching from the primary conductor and running transversely to the direction of the primary conductor, the secondary conductors of each electrode alternately interleaving with the secondary conductors of the other electrode.

11. The biosensor according to claim 10, wherein the direction in which the secondary conductors run changes a plurality of times over their length.

12. The biosensor according to claim 10, wherein the sample application surface is delimited by a masking layer.

13. The biosensor according to claim 10, wherein the test field comprises a swellable material configured and adapted such that the volume of the test field increases upon absorption of the sample liquid.

14. The biosensor according to claim 10, wherein the test field is further configured for separating undesirable components from the sample liquid and limiting said components from reaching and wetting the electrode structure.

15. The biosensor according to claim 10, wherein the biosensor further comprises a capillary chamber adjacent to the sample application surface, said chamber configured for absorbing an excess volume of the sample liquid.

16. A method for analyzing a sample liquid using a biosensor analysis system, comprising:

providing a biosensor comprising a carrier layer, an electrode structure located on the carrier layer and comprising at least two electrodes, and a test field located on the carrier layer and generally covering the electrode structure, the test field being capable of absorbing the sample liquid and containing a reagent system configured to react with the sample liquid and to produce a change of an electrical measurement variable, said measurement variable being characteristic for a desired analysis result and measurable by means of an analysis measurement employing at least two of the electrodes, the test field further comprising a sample application surface on an upper side of the test field and facing generally away from the carrier layer, the electrode structure being distributed on an effective electrode structure area which area is wettable by the sample liquid, the distribution of the electrode structure on the electrode structure area being generally homogeneous with respect to an AC resistance measurement performed on a liquid layer having a defined conductivity and layer thickness;

providing an analysis instrument comprising an analytical measuring device configured for measuring the measurement variable while the biosensor is positioned in a measurement position and electrically connected to the measuring device, the analysis instrument further comprising an evaluation unit configured for determining the desired analysis data from the measured values of the measurement variable;

contacting the sample application surface from above with a droplet of the sample in such a manner that it diffuses over at least a partial area of the sample application surface and causes a corresponding partial area of the effective electrode structure area to be wetted;

performing, within a time period during which the size;

of the wetted area does not significantly change, an analysis measurement in which the measurement variable is measured using the electrodes;

performing, within a time period during which the size of the wetted area does not significantly change, an area compensation measurement in which an AC resistance value is measured between two electrodes of the electrode structure; and

using the measured AC resistance value, when determining the analysis data, as a measure of the partial area of the effective electrode structure area wetted by the sample liquid.