JPH09311116A - Biochemical measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the substance attached to the electrodes of sensor parts, and maintain the activity of the electrodes. SOLUTION: After completion of measurement, the positive polarity voltage that has been hitherto applied to the electrode 72a through the voltage impression circuit 61 is thereafter changed to a negative polarity voltage for the time T1 =30 seconds. Thereby, the substances attached on the electrodes 72a and 72b are separated; and in succession, the polarity of the voltage applied to the electrode 72a is changed to positive polarity for the time T2 =30 seconds, so that the sensor output being output through an amplifier 63 is stabilized in an early stage, and the recovery is made OK and the subsequent measurement can be enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biochemical measuring device for measuring a specific substance in a biological fluid by enzymatically reacting the biological fluid such as urine and blood.

[0002]

2. Description of the Related Art Conventionally, a biochemical measuring instrument for measuring a specific substance contained in a biological fluid such as urine or blood has a biosensor (immobilized enzyme) and a pair of electrodes in a detecting portion (biochemical sensor). There is a method in which urine is subjected to an enzymatic reaction in the detection unit and the specific substance is measured from the change in the amount of electricity output from the sensor. In this seed biochemical measuring instrument, the sample may be measured several times continuously over time. In this case, if the measurement is performed once, the detection part of the biosensor becomes dirty with the biological fluid, so when the measurement is completed, the detection part is washed,
The following measurements are prepared.

[0003]

In the above-mentioned conventional biochemical measuring device, the substance in the immobilized enzyme of the biosensor can be removed by washing, but the substance attached to the electrode surface by the electrochemical action is not so washed. There was a problem that it could not be removed sufficiently, the measurement accuracy deteriorated after several uses, and this shortened the life of the biosensor and accelerated the replacement time.

The present invention has been made in view of the above problems, and an object thereof is to provide a biochemical measuring instrument capable of removing the adhesion of a substance to an electrode of a sensor part and prolonging its life. There is.

[0005]

A biochemical measuring device according to claim 1 of the present application uses a pair of electrodes to electrochemically increase or decrease a substance which is increased or decreased by enzymatically reacting a biological fluid. A biochemical sensor for detecting the specific biochemical substance from the change in the quantity of electricity output from this biochemical sensor, and a measurement end confirmation means for confirming the end of measurement, and a response to the confirmation of the end of measurement. Then, it is characteristically provided with a voltage applying means for applying a voltage having a polarity opposite to that at the time of measurement / standby to the electrode for a certain period of time. In this biochemical measuring device, a substance is attached to the electrode by the chemical action of the electrode when a positive voltage is applied during the measurement. At the end of the measurement, by applying a voltage of opposite polarity, the substances attached to the electrodes are dispersed by the electrochemical action of the opposite direction.

A biochemical measuring device according to a second aspect of the present invention comprises a biochemical sensor for electrochemically detecting a substance that increases or decreases by enzymatically reacting a biological fluid using a pair of electrodes. In the case of measuring a specific biochemical substance from the change in the amount of electricity output from the sensor, the measurement end confirmation means for confirming the measurement end and the measurement / standby state for the electrode in response to the confirmation of the measurement end It is characteristically provided with a voltage applying means for applying a voltage of opposite polarity for a certain period of time and then applying a positive polarity voltage for a certain period of time. In this biochemical measuring instrument, the substance attached to the electrode is dispersed by the application of the reverse polarity voltage after the measurement is finished, and then the positive voltage is applied again to stabilize the sensor output quickly and Can be measured.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to embodiments. FIG. 1 is a block diagram showing a circuit configuration of a urine measuring device according to an embodiment of the present invention. The urine meter of this embodiment includes a sensor unit 1, a current-voltage converter 2 for converting a detection current flowing through the sensor unit 1 into a voltage, and an AD for converting its output into a digital signal.
The converter 3 and the MPU 4 that takes in digital signals from the AD converter 3 and executes various measurement processes.
An indicator 5 for displaying a measurement result, a judgment index of the result, a warning, an instruction, etc., a temperature measuring circuit 6, a calibration resistor 7, a sensor cover attachment / detachment detection switch 8, a calibration switch 9,
A buzzer 10, an EEPROM 11, an infrared communication interface 12, and a reset switch 13 are provided.

The MPU 4 further incorporates an internal I / O circuit 1 for incorporating a timer 14 used for AD conversion, a sensor cover attachment / detachment detection switch 8 and a calibration switch 9 on / off.
5, a clock 16, an 8-bit AD converter 17 for taking in the temperature and the calibration resistance, a CPU 18, a ROM 19, a RAM 20, an LCD driver 21, a SiO channel 22, and a buzzer 10 for executing processing calculation for urine measurement, EEP
An I / O circuit 23 for connecting to the ROM 11 and the like is provided.

As the biosensor (enzyme sensor) of the sensor unit 1, a generally well-known one consisting of an immobilized enzyme and an electrode may be used. As an example thereof, the one shown in FIG. 2 will be briefly described. The enzyme sensor shown here is an integrated planar-type enzyme sensor 78 including a base electrode 70 attached to the sensor holder 1 a and an immobilized enzyme film 73 laminated on the base electrode 70. Base electrode 70
As the current-voltage converting element, a planar-type enzyme electrode / hydrogen peroxide electrode is used. In this case, an immobilized enzyme layer is formed on the surface of the sensitive part, and increase / decrease of enzyme and hydrogen peroxide due to the enzymatic reaction is captured as a change in oxidation current of the base electrode. Various metals are used as the electrode, but platinum (Pt) is mainly used as the working electrode, and gold (Au), platinum (Pt), silver (Ag), etc. are used as the reference electrode and the counter electrode.

Examples of the enzyme used in the enzyme sensor 78 are as follows. Glucose oxidase (GOD) Glucose + O ₂ → Gluconic acid + H ₂ O ₂ Enzyme (O ₂ ) consumption (decrease) and hydrogen peroxide (H ₂ O ₂ )
(Increasing) and generating gluconic acid (decreasing pH).

Lactate oxidase (LOD) L-Lactate + O ₂ → Pyruvate + H ₂ O ₂ Consumption (decrease) of enzyme (O ₂ ) and hydrogen peroxide (H ₂ O ₂ )
Occurrence (increased) of Urease Urea + H ₂ O → 2NH ₃ + CO ₂ Accompanied by generation of ammonia (increase in pH due to decrease in hydrogen ion concentration) and increase in CO ₂ gas.

Uricase Uric acid + O_Two+ 2H_TwoO → Allantoin + H_TwoO + CO_Two Enzyme (O_Two) Consumption (reduction) and hydrogen peroxide (H_TwoO_Two)
Generation (increase) and CO _TwoWith the increase of gas. Fixed fermentation
An example of the elementary film 73 is immobilization consisting of the above enzyme.
The sandwich structure that protects the enzyme enzyme layer 75 with the upper and lower layers is an alternative.
It is tabular. The immobilized enzyme layer 75 has a crosslink having a functional group.
Cross-linking method using material, envelope in gel lattice or polymer coating
It is formed by the closing method.

The lower protective film 74 restricts the permeation of interfering substances to the surface of the electrode as necessary, and the base electrode 70
In addition, the adhesiveness and stability with the immobilized enzyme layer 75 are required, and acetyl cellulose, an ion exchange membrane material, or the like is used. The upper protective film 76 protects the immobilized enzyme layer 75,
The purpose is to limit the diffusion of the substrate into the immobilized enzyme layer 75, and the adhesiveness to the immobilized enzyme layer 75 and the mechanical strength are required.

A thin and uniform film can be obtained by using a dip coating method or a spin coating method for forming each of these layers. For example, as the lower protective film 74, a 5% acetyl cellulose thin film (solvent composition; acetone: cyclohexanone = 3: 1) is dropped on the metal electrode 72 to obtain 2000 rp.
It can be formed by rotating at m for 5 seconds. Immobilized enzyme layer 75
Can be formed by spin coating an enzyme solution prepared by mixing a 0.5% glutaraldehyde solution adjusted with a 0.1 M phosphate buffer (pH 7.0) and an enzyme in the same manner as the lower protective film 74. The upper protective film 76 is a 2.5% acetyl cellulose thin film (solvent composition; acetone: ethanol = 1: 1).
Can be formed by dip coating at 1 cm / sec.

Here, the planar type hydrogen peroxide electrode as the base electrode 70 is a metal electrode 72 on the surface of an insulating film 71 made of, for example, a ceramic or resin film.
For example, a thin film of platinum / gold / silver is selectively formed. In addition, the immobilized enzyme film 73 crosslinks and fixes GOD and LOD as the immobilized enzyme layer 75, and further, the upper protective film 76.
In order to strengthen the function of the above, a surface protective film 77 made of nylon lattice or polycarbonate is separately provided on the upper protective film 76.
It is in close contact with. The urine meter of this embodiment may use an enzyme sensor other than that shown in FIG.

The embodiment of the urine measuring device, as shown in FIG.
A sensor 33 is detachably attached to the measuring device main body 32,
A display unit [corresponding to the display device 5 in FIG. 1] 34 for displaying measured values (urine sugar, etc.) and various instructions is provided on the surface side of the measurement device main body 32, and a battery cover is provided on the head of the measurement device main body 32. 35 is detachably attached. A detection unit 33a for detecting urine is opened at the tip of the sensor 33, and urine is attached to the detection unit 33a. A calibration switch 36 for performing calibration is provided on the back side of the measuring device body 32. Most of the circuits such as the MPU 4 in FIG. 1 are built in or provided in the measuring device main body 32. The sensor unit 1 of FIG. 1 corresponds to the sensor 33 of FIG.

FIG. 4 is an external perspective view of a case for storing the urine meter 31 of the embodiment. Not only can this storage case be placed on the floor of the toilet, but it can also be attached to the wall surface using the wall mounting plate. This storage case includes a urine measuring device storage port (measuring device storing section) 42 for storing a urine measuring device 31 as shown in FIG. A storage liquid container mounting port (storage liquid container storage portion) 44 that is arranged at the bottom of the storage device 40 and that detachably stores the storage liquid container that stores the storage liquid of the sensor 33 of the urine meter 31, and the case body 40 can be opened and closed. A main body cover 45 that is attached to the urine measuring device 31 and covers the urine measuring device 31 portion that emerges from the storage port 42 in a state where the urine measuring device 31 is stored in the storage port 42; Temporary cup storage section for detachable storage (measuring instrument temporary storage section and inside space of the body cover 45) 4
8 and a calibration liquid cup attachment port (calibration liquid container storage portion) 50 that detachably stores a calibration liquid cup (calibration liquid container) that stores the calibration liquid of the sensor 33 of the urine measuring device 31.

A cover 52 that closes the storage port 42 when the urine meter 31 is taken out from the storage port 42 is attached to the case body 40 so as to be openable and closable. Case body 40
On the back side (back plate 54) of the wall mounting hole (small hole 5
6b etc.). On the front surface of the bottom of the case body 40,
A confirmation window 58 for visually recognizing the preservative solution in the preservative solution container is provided so that the stain and the remaining amount of the preservative solution can be easily confirmed. The storage solution (also referred to as a buffer solution) keeps the sensor 33 of the urine measuring device 31 in a wet state and keeps the PH and the ion concentration constant. For example, phosphate is used.

FIG. 5 is a circuit diagram showing an electric circuit of the sensor unit 1. 5, is made from the voltage application circuit 61 to apply a voltage V _b to the electrode 72a of the sensor. The electrode 72b is connected to the input end of the amplifier 63 and is also connected to one end of the resistor 62. The other end of the resistor 62 is grounded. The sensor output is obtained from the amplifier 63. The voltage application circuit 61 receives +0.4 V of positive polarity and − of reverse polarity in response to the switching command signal M _E from the CPU 18.
It is configured to be switchable to 0.4V. In this circuit, when urine is applied to the detection unit 33a for measurement, the immobilized enzyme and the urine substance (substrate) cause an electrochemical reaction, which causes the voltage application circuit 61 → electrode 72a → enzyme membrane → electrode 7
A current flows in the order of 2b → resistor 62 → ground, and a voltage corresponding to the current is obtained at both ends of the resistor 62.
It is amplified by and is input to the A / D converter 3 as a sensor output. The substance in urine can be measured by detecting the degree of change in the sensor output. Such urine measurement processing is similar to conventional processing. Next, the operation of the embodiment urine measuring instrument from the start of measurement to the next measurement OK will be described. Since the processing after the measurement is characteristic, the operation after the end time will be described in detail.

When the urine measuring device 31 is housed in the case body 40, or when the urine measuring device 31 is not housed in the case body 40 but urine is not applied to the detecting part 33a, the detecting part of the sensor is detected. No reaction occurs at 33. Therefore, the voltage applying circuit 61 causes the electrode 7
As shown in FIG. 6B, a voltage of +0.4 V is applied to 2a, but the electrodes 72a, 72b, and the resistor 62 are applied.
No current flows through the sensor, and the sensor output is at 0 level, as shown in FIG.

When urine is applied to the detection portion 33a of the urine measuring device 31 with the urine measuring device 31 removed from the case body 40,
The sensor 33 starts the enzymatic reaction, and the electrodes 72a, 72b,
A current flows through the circuit of the resistor 62. As a result, the sensor output rises in accordance with the change in current, such as at the measurement start point a, as shown in FIG. During this period, as shown in FIG. 6B, the voltage applied to the electrode 72a is +0.4.
V is kept constant. The MPU 4 calculates the substance in the urine from the change in the sensor output, and displays the value on the display 5 (the display unit 34 in FIG. 3).

As the enzymatic reaction progresses, a change in electric current also occurs, and the sensor output becomes constant as shown in FIG. 6 (A). When the sensor output becomes constant, the stage of waiting for recovery and displaying the sensor being prepared is displayed, and the display unit 5 displays that effect.
At this stage, as shown in the flowchart of FIG. 7, first, it is determined whether or not the cover 45 is attached (step ST1). Here, if the cover 45 is not attached, it is estimated that the urine measuring device 31 is not attached to the case body 40, and the process returns to the stage of waiting for recovery, displaying the sensor preparation, and displaying the save instruction. Details of the processing at this stage are omitted.

The cover 45 is attached, and step S
If the determination in T1 is YES, it is estimated that the urine measuring device 31 is attached to the case body 40 and the detecting portion 33a of the sensor 33 is immersed in the liquid of the storage liquid container. Or? It is determined (step ST2). When the detection unit 33 is actually immersed in the storage solution, the detection unit 33
Since the urine a is washed, the sensor output starts to drop as the washing progresses, as shown in FIG. When the sensor output level becomes lower than the level V _TH1 [point b in FIG. 6 (A)], it is determined that the cleaning is in progress, and the cleaning is OK in step ST2? The determination is YES, and the process proceeds to step ST3.

At step ST3, the output of the sensor is shown in FIG.
(A) level V _TH2 has been reached, that is, whether or not the level has reached a good level by applying a reverse voltage to the electrode 72a. Here, the level V _TH2 is V _TH1 <V _TH2 , the sensor output is close to zero, and is a level for determining whether or not the sensors have reached an almost equal state before measurement. When the size becomes smaller than the point (point c), the cleaning is completed, and it is considered that the measurement is completed.

When the determination in step ST3 is YES,
As shown in FIG. 6B, reverse polarity −0.4 V is applied to the electrode 72a (step ST4). Then, the voltage of the opposite polarity is continuously applied for 30 seconds (= T ₁ ) (steps ST4 and ST5). By applying the voltage of the opposite polarity, a current flows in the order of ground → resistor 62 → electrode 72b → electrode 72a → voltage applying circuit 61, and a current of the opposite polarity to that during measurement flows. Due to this reverse current, the electrodes 72a and 72
In b, an electrochemical reaction opposite to that at the time of measurement occurs and the electrode 72
The substance adhering to a and the electrode 72b leaves the electrode 72a and the electrode 72b. As a result, the electrodes 72a and 72b are also in the clean state as before the measurement.

When 30 seconds have passed since the application of the reverse polarity was started, the determination in step ST5 is YES, and the process proceeds to step ST6. In step ST6, as shown in FIG. 6B, the positive applied voltage of +0.4 V is set again. As shown in FIG. 6 (A), the sensor output suddenly falls in a impulse-like manner once to a negative value by a voltage application of the opposite polarity, and then slowly returns to the zero level. If this is continued, it takes time to stabilize, so that the positive voltage is applied this time and the sensor output is returned in impulse again.
This positive voltage is applied here for 30 seconds (step ST7). By applying the positive voltage for about 30 seconds, the sensor output can be brought to zero level early and stabilized. The buzzer of recovery OK notifies by the determination in step ST7 (step ST8). As a result, the next measurement can be performed, and the urine measuring device is put in a standby state at the end of recovery.

The cleaning in FIG. 7 has been described with respect to the case of using the preservation solution, but the processes of ST2 to ST8 can be similarly applied to the case of cleaning with cleaning water (fresh water) and ending the measurement.

[0028]

According to the invention of claim 1 of the present application, when the measurement is completed, a voltage having a reverse polarity different from that during measurement and standby is applied to the electrode for a certain period of time. The substances attached to the electrodes can be dispersed and the electrode activity can be maintained.

According to the second aspect of the invention, when the measurement is completed, a voltage having a reverse polarity different from that during measurement and standby is applied to the electrode for a certain period of time, and then the positive polarity voltage is further maintained for a certain period of time. Since a voltage is applied, the substances attached to the electrodes can be dispersed, the electrode activity can be maintained, and the sensor output can quickly return to zero level and stabilize, so that the next measurement can be started early. You can

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration of a urine measuring device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an enzyme sensor used in the urine meter of the same embodiment.

FIG. 3 is an external perspective view of the urine measuring device according to the embodiment.

FIG. 4 is an external perspective view of a case for storing the urine measuring device according to the same embodiment.

FIG. 5 is a circuit diagram showing a circuit configuration of a detection unit of the sensor of the urine measuring device according to the same embodiment.

FIG. 6 is a waveform diagram showing the sensor output of the detection unit and the voltage applied to the electrodes.

FIG. 7 is a flowchart for explaining a recovery process from the end of measurement by the urine measuring device according to the embodiment to the next measurement OK.

[Explanation of symbols]

 61 voltage application circuit 62 resistance 63 amplifier 72a, 72b electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideki Endo 24, Yamanouchi Yamanoshitamachi, Ukyo-ku, Kyoto City Omron Life Science Institute, Inc. (72) Inasa Misako 24 Yamanouchi Yamanoshitamachi, Ukyo-ku, Kyoto Omron Life Co. Inside Science Institute

Claims (2)

[Claims] 1. A biochemical sensor for electrochemically detecting a substance, which increases or decreases by enzymatic reaction of a biological fluid, using a pair of electrodes, and a biochemical sensor for detecting a specific amount based on a change in the amount of electricity output from the biochemical sensor. In a biochemical measuring instrument for measuring biochemical substances, a measurement end confirming means for confirming the end of measurement and a voltage having a polarity opposite to that at the time of measurement / standby to the electrode in response to the confirmation of the end of measurement at a certain time. A biochemical measuring instrument, characterized in that it comprises a voltage applying means for applying the voltage across. 2. A biochemical sensor for electrochemically detecting a substance that increases or decreases by enzymatically reacting a biological fluid using a pair of electrodes, and a biochemical sensor that is specific to the change in the amount of electricity output from the biochemical sensor is provided. In a biochemical measuring instrument for measuring biochemical substances, a measurement end confirming means for confirming the end of measurement and a voltage having a polarity opposite to that at the time of measurement / standby to the electrode in response to the confirmation of the end of measurement at a certain time. Applied for a certain period of time,
A biochemical measuring instrument comprising a voltage applying means for applying a positive voltage.