JP2002506969A - Heated electrochemical cell - Google Patents

Abstract

(57) Abstract: The present invention is a method for measuring the concentration of an analyte in a sample, comprising heating the sample in a disposable test cell; and substantially controlling the temperature of the sample in the test cell. Measuring the concentration of an analyte, or an alternative species, in a sample at a predetermined point in the reaction profile by an independent means. The present invention also provides a spacer (3) pierced by an opening defining a cell wall, a first metal electrode (2) on one surface of the spacer extending to one side of the opening, A second metal electrode (4) on the other side of the spacer extending to the side of the opening opposite the first electrode, means for placing the sample in a cell chamber defined by the electrode and the cell wall, and a cell (10). A) providing an electrochemical cell for use in the method, comprising means for heating the sample contained therein.

Description

DETAILED DESCRIPTION OF THE INVENTION

 (Technical field)

The present invention relates to a method and an apparatus for measuring the concentration of an analyte in a solution.

[0002] The invention is particularly described for the measurement of blood glucose concentration, but is not limited to its use, but has general application to the measurement of analytes other than glucose and general application to the measurement of solutions other than blood. Application.

BACKGROUND OF THE INVENTION [0003] Humans suffering from diabetes routinely examine their blood glucose levels, and there is a need for simple, reliable and inexpensive means to facilitate such routine tests. .

[0004] A common method for conducting tests is to combine a blood sample with an enzyme, such as glucose dehydrogenase ("GDH"), which oxidizes glucose and is reduced in the process. , Ferricyanide) reacts with the reduced form of GDH to return the GDH to its initial form, producing ferrocyanide in the process, and then obtaining the resulting ferrocyanide concentration, for example, electrochemically or The signal is detected spectroscopically to obtain a signal, which can be interpreted as giving an estimate of the glucose concentration in the sample.

[0005] Our co-pending applications PCT / AU96 / 00723 and PCT / AU96
No./00724, which forms a part of this specification, describes a method and apparatus suitable for electrochemically measuring blood glucose concentration by electrochemical measurements.

[0006] A preferred method of accurately measuring the concentration of an analyte is to react all analytes present in the sample with a reagent to obtain a detectable species. This requires that the reaction of the subject be completed.

[0007] The reaction between GDH and glucose typically takes several minutes to be substantially complete. This is believed to be the time required for glucose to diffuse from the glucose-containing cells of the blood. Since this length of time is unacceptably long on the market, glucose concentrations can be measured in a shorter time (eg, 20-30 seconds) to allow less precise response, or as described in co-pending application PCT / AU96, for example. It is more common to apply certain factors to estimate glucose concentration by the kinetic extrapolation outlined in US / 00723. Although this measure reduces test time, it can lead to less accurate results.

[0008] It is an object of the present invention to provide a method and apparatus that avoids or ameliorates the above-mentioned disadvantages of the prior art.

DETAILED DESCRIPTION According to one aspect, the present invention is a method for measuring the concentration of an analyte in a sample, the method comprising heating the sample in a disposable test cell; Determining, by substantially independent means, the concentration of the analyte in the sample or the concentration of a species that substitutes for the analyte at a predetermined point in the reaction profile.

Those skilled in the art will understand that the term “reaction profile” as used herein means a relationship between reaction variables. For example, reaction profiles often show certain concentration changes over time. Such a profile, to those skilled in the art,
Both qualitative and quantitative information can be provided, including information about whether the reaction system has reached a steady state.

[0011] Preferably, the predetermined point in the reaction profile is in a steady state, and the species that substitutes for the analyte concentration is preferably a mediator (eg, an enzyme mediator).

In one embodiment of the invention, the sample is heated by an exothermic reaction caused by contact of the reagent with one or more suitable reagents.

In a second aspect of the invention, the sample is heated electrically, for example by means of passing a current through a resistive element coupled to the measuring means.

In a very preferred embodiment, the measuring means comprises co-pending application PCT / AU96 / 0
No. 0723 and PCT / AU96 / 00724, of an electrochemical cell type, wherein the sample is heated by applying an alternating voltage signal between the electrodes of the sensor.

According to a second aspect, the invention relates to a spacer perforated by an opening defining a cell wall, a first metal on one surface of the spacer extending to one side of the opening. The sample is placed in a cell volume defined by the electrode, a second metal electrode on the other side of the spacer extending to the side of the opening opposite to the first electrode, the electrode and the cell wall. And an electrochemical cell comprising means for heating the sample contained in the cell.

BEST MODE FOR CARRYING OUT THE INVENTION In a preferred embodiment of the method of the present invention, PCT / AU96 / 00723 and P
Glucose concentrations are measured using an electrochemical cell of the type described in CT / AU96 / 00724 (our co-pending application). The measurement methods described in these applications use an algorithm that can calculate the diffusion coefficient value of the redox mediator and measure the concentration of the reduced mediator in a manner that is substantially independent of the temperature of the sample. I have. The method described herein differs from the prior art method of measuring the Cottrell current at a defined time after applying a voltage. The present invention differs in that the sample is heated.

In a first aspect of the invention, the blood sample is heated by means of an exothermic reaction before and / or during the electrochemical measurement. In a first embodiment, a reagent that releases heat when in contact with blood is placed in a sensor cell. Examples of such reagents include:
Salts that generate heat when dissolved (eg, aluminum chloride, lithium halide salts, lithium sulfate, magnesium halide salts, and magnesium sulfate). Another type of reagent that may be suitable is a reagent having two components that release heat when mixed. These two components are placed in separate locations on the sensor during assembly, for example while coating on the opposite internal cell wall, and at least one component dissolves when the sample is introduced into the sensor, and then It is arranged to be in contact with the second component. Upon contact, the two components react and release heat. The reagent used to generate heat must not deleteriously affect the function of other active elements in the sensor. For example, they must not corrode the electrodes, denature enzymes if present, or have any deleterious interaction with any mediators that may be present. When a blood sample is introduced into the sensor, heat is released and the temperature of the blood sample increases. This facilitates the reaction between glucose and GDH, and since the concentration of ferrocyanide is independent of temperature, an accurate assessment of glucose concentration can be made much shorter than otherwise.

After the sample has been placed in the cell, a reagent that generates heat can be added, but is less preferred.

The temperature of the sample is preferably increased by 5 to 15 ° C., for example, 20 to 10 seconds.
Preferably, the temperature is raised from 30 ° C to 30 ° C or 35 ° C. It is desirable that the temperature peak reach in 2-5 seconds.

A second aspect of the invention uses a cell containing an electrically resistive element. Then, the sample can be electrically heated by passing a current through the resistance element. For example, in FIG. 1, the plastic support 1 having the first electrode 2 (for example,
2 shows an electrochemical sensor comprising a separator layer 3 having a punched-out circular opening defining a cell chamber 10 to which the first electrode 2 is bonded on one side of the cylinder (sputtered gold layer). The opposite surface of the cylindrical cell 10 is covered with a second electrode layer 4 (for example, sputter-coated palladium), which is supported by a rubber or plastic layer 5. The metal foil layer 6 provides an electrical contact to a resistor bridge 9 formed in the rubber or plastic layer 5. Insulation layer 7 (for example,
Plastic) provides heat loss insulation through the metal foil. Openings 8 in layer 7 provide electrical contact with metal foil layer 6. The resistance bridge 9 is, for example, a metal foil 6.
It is formed from carbon particles injected into a rubber or plastic layer 5 having a composition and dimensions so as to provide an appropriate electric resistance between the electrode and the electrode layer 4. This method has the advantage of concentrating thermal effects on adjacent cells. The heating resistive element can be formed by other means, for example, if desired, using an electrically insulating layer that is made partially conductive in certain areas, for example, by exposure to certain chemicals and light. Can be formed by coating an electrically conductive support. When using a cell according to the second aspect, the sample is placed in the cell, a voltage is applied to the resistive element, after the required amount of heat has been generated, the voltage across the resistive element is cut off, after any waiting time, A voltage is applied between the first electrode and the second electrode, and an electrochemical assay of the subject is performed.

[0021] Alternatively, the voltage of the resistive element is maintained at an initial level during the assay of the analyte, or the temperature of the sample is maintained at a lower level sufficient to substantially maintain the temperature of the sample at a desired level. be able to.

In another aspect, the means for applying a voltage to the resistive element monitors the current flowing through the resistive element and automatically adjusts the voltage to maintain the required output. This heats the sample in a reproducible manner, even if the resistance of the resistive element changes between sensors. Moreover, the required power level can be adjusted based on the ambient temperature measured by another sensor. This results in a more reproducible sample temperature that reaches higher than the ambient temperature using the sensor.

In a third aspect of the invention, a simple heating of a sample is achieved by applying an alternating voltage signal between the working and counter electrodes of the sensor, for example of the kind described in our co-pending application. Can be. If this AC voltage signal had the correct frequency and amplitude, it would be possible to heat the sample while still making precise measurements of the subject with the sensor. Since the voltage signals are alternating,
Any reaction that occurs during the half voltage cycle is reversed during the other half of the cycle, with no net change, but the energy is lost and appears as heat in the sample. This applies specifically to sensors of the type disclosed in our co-pending application above, in which any small potential that may occur in the cell as the cell returns to its initial state after the interruption of the AC voltage. Changes also disappear quickly.

When using a cell as disclosed in our co-pending application, the sample size is very small, so that heating can be achieved with low energy output.

Example of a Heated Strip Experiment Example 1 A disposable test of the type described in PCT / AU96 / 00724 by placing a metal bar, heating to 50 ° C., and contacting the sample receiving area in the strip. The strip was heated. A whole blood sample was introduced into the area of the strip that received the sample, and the glucose present in the sample was allowed to react with the sensor reagent for 13 seconds.
The current was then collected for 10 seconds and PCT / AU96 / 0072.
Analysis was performed according to the method described in No. 3. The hematocrit of the blood sample is 67.5%, 49.5% and 20%, and the glucose concentration is between 2.5 mM and 30 mM.
FIG. 2 shows the results of these tests in the case of the above.

Example 2 A disposable test strip of the type described in PCT / AU96 / 00724 was modified by bonding a heating element to the base of the strip beneath the sample receiving area. The heating element sputters two parallel low resistance metal tracks onto a polyester support and then sputters a thin resistance metal track to the right with respect to the low resistance metal track so that the resistance metal track is Contact was made with both of its parallel low resistance tracks. The heater was then adhered to the base of the disposable test strip using an adhesive, with the resistance track immediately below and facing the area for receiving the sample on the strip. The parallel low resistance tracks protruded from the end of the strip and provided electrical contact for power to power the heater. The power supply to the heater consisted of a battery and a variable resistor with adjustable heating rate. A whole blood sample was introduced into the sample receiving area of the strip and glucose present in the sample was contacted with the sensor reagent for 20 seconds. The current was then collected for 10 seconds and the PCT / AU96 / 0
The analysis was performed according to the method described in No. 0723. Hematocrit value of blood sample is 65
%, 46% and 20% and the glucose concentration is between 2.8 mM and 32.5 m.
The results of these tests when they are between M are shown in FIG.

Although the present invention has been described in terms of an electrochemical method for measuring glucose blood levels, the method can be applied to any suitable spectroscopic or other measurement method, and to non-blood samples, and to non-glucose samples. It will be appreciated that application to a subject is also possible.

[Brief description of the drawings]

FIG. 1 shows a schematic illustration of a longitudinal section of a sensor strip according to the invention, taken along the center line of the sensor strip.

FIG. 2 shows the results of tests performed on blood samples with varying hematocrit and glucose concentrations, according to one embodiment of the present invention.

FIG. 3 shows the results of tests performed on blood samples with varying hematocrit and glucose concentrations, according to another embodiment of the present invention.

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] February 10, 2000 (2000.2.10)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

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[0009] According to DETAILED DESCRIPTION one aspect, the present invention is directed to a method of measuring the concentration of an analyte in a sample, the method step of heating the sample in a disposable test cell; and in the test cell Measuring the concentration of the analyte in the sample or the concentration of a species that substitutes for the analyte at a predetermined point in the reaction profile by means substantially independent of the temperature of the sample .

[Procedural Amendment] Submission of translation of Article 34 Amendment of the Patent Cooperation Treaty

[Submission date] June 15, 2000 (2000.6.15)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

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[Claims]

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), OA (BF, BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, KE, LS, MW, SD, SL, SZ, UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR , BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS , JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, UG, US, UZ, VN, YU, ZW (72) Inventor Thomas William Beck Australia 2754 New No. 121 Kedah Circuit, North Richmond, South Wales

Claims (36)

[Claims] 1. A method for determining the concentration of an analyte in a sample, the method comprising: heating the sample in a disposable test cell; and determining the reaction profile by means substantially independent of temperature. Measuring the concentration of the analyte in the sample at that time or the concentration of the species in place of it. 2. The method of claim 1, wherein the predetermined point in the reaction profile is in a steady state. 3. The method of claim 1, wherein the alternative to the analyte concentration is a mediator.
Or the method of 2. 4. The method according to claim 3, wherein the mediator is an enzyme mediator. 5. The method according to claim 1, wherein the sample is heated by an exothermic reaction that occurs when the sample is brought into contact with at least one suitable reagent. 6. The method of claim 5, wherein the at least one suitable reagent is a salt that releases heat when dissolved. 7. The method of claim 6, wherein the salt is selected from the group consisting of aluminum chloride, lithium halide, lithium sulfate, magnesium halide and magnesium sulfate. 8. The method of claim 1, wherein the at least one suitable reagent releases heat when mixed.
The method of claim 5, which is a component system. 9. The method of claim 8, wherein each of the two components is placed at a different location on the sensor during assembly. 10. The method of claim 9, wherein the two components are placed as coatings on opposing internal cell walls of the sensor. 11. The method according to claim 1, wherein the sample is electrically heated. 12. The method of claim 11, wherein the sample is heated by means for passing a current through a resistive element coupled to the measuring means. 13. The method according to claim 1, wherein the concentration of the analyte is measured by an electrochemical measurement method. 14. The method according to claim 13, wherein the sample is heated before and / or during the performance of the electrochemical measurement. 15. The method according to claim 1, wherein the temperature of the sample increases by 5 ° C. to 15 ° C. 16. The method according to claim 1, wherein the temperature of the sample increases for 2 to 10 seconds. 17. The method according to claim 1, wherein the maximum temperature is reached within 2-5 seconds. 18. The method according to claim 1, wherein the analyte is glucose. 19. The method according to claim 1, wherein the sample is blood. 20. The method of claim 19, wherein the blood sample is combined with an enzyme. 21. The method according to claim 20, wherein the enzyme is glucose dehydrogenase which oxidizes glucose and converts it to reduced GDH. 22. The method of claim 21, wherein an oxidized mediator is present. 23. The oxidized mediator is ferricyanide.
3. The method according to 2. 24. The method of claim 23, wherein the ferricyanide is reacted with the formed GDH to form a ferrocyanide. 25. The method of claim 24, wherein the generated ferrocyanide is detected to obtain a signal that is indicative of the glucose concentration in the sample. 26. The method according to claim 25, wherein the sensing is performed by electrochemical means. 27. The method according to claim 25, wherein the sensing is performed by spectroscopic means. 28. A spacer perforated by an opening defining a cell wall, a first metal electrode on one side of the spacer extending to one side of the opening, and an opposite side of the first electrode. Including a second metal electrode on the other side of the spacer extending to the side of the opening, means for placing the sample in the cell chamber defined by the electrode and the cell wall, and means for heating the sample contained in the cell Electrochemical cell. 29. The means for heating a sample is an electrical resistance element.
An electrochemical cell according to claim 1. 30. Applying a voltage to the resistive element to regenerate the required amount of heat, cutting off the voltage across the resistive element, and using the first electrode and the first electrode to perform an electrochemical assay on the subject. 29. A method comprising applying a voltage between two electrodes.
A method for heating an electric cell according to claim 1. 31. The voltage of the resistive element is maintained at an initial level during the assay of the analyte, or at a lower level sufficient to substantially maintain a desired level of sample temperature. 30. The method according to 30. 32. The method according to claim 30, wherein the means for applying a voltage to the resistance element monitors a current flowing through the resistance element and automatically adjusts the voltage so as to maintain a required output. The described method. 33. The method of claim 32, wherein the power can be adjusted based on ambient temperature measured by another sensor. 34. A method for determining a concentration of an analyte in a sample, substantially as herein described for any one of the embodiments. 35. An electrochemical cell substantially as herein described with reference to FIG. 1 or any one of the embodiments. 36. A method of heating an electrochemical cell substantially as described herein for any one of the embodiments.