JP2001305094A - Biosensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a conventional biosensor of incapability of continuous measurement. SOLUTION: One electrode 22 is brought into direct contact with urine, that is, opened to the atmosphere. Foaming generated to the electrode 22 is thereby released easily into the atmosphere to provide the biosensor capable of continuous measurement without the degradation of transmission capacity of electric charge.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biosensor for mainly examining sugar in urine.

[0002]

2. Description of the Related Art Urine is an important source of information on the health of individuals, and various functional disorders can be examined by quantitative analysis of urine components. As a means for responding to this need, there is a urine test paper used in health examinations and medical institutions. Urine test paper detects the discharge of sugar, protein, urobilinogen, occult blood and the like into urine by a chemical reaction. That is, the amount of the substance is determined based on a change in the color tone of the test paper. Test strips have the advantage that they are easy to use and can be used by anyone, but they are problematic from the viewpoint of quantitative analysis because they are qualitative or semi-quantitative.

Therefore, as a method for quickly and easily quantifying a specific component in urine, measurement using a biosensor that links an enzyme reaction to an electrode reaction is performed.

FIG. 2 is an explanatory diagram for explaining the configuration and operation of a conventional biosensor. Urine that has entered through the urine collection port 5 reaches the glucose oxidase layer 6 through the interfering substance removing film 5. The glucose oxidase layer 6 has glucose oxidase, and decomposes glucose in urine into gluconic acid and hydrogen peroxide. This hydrogen peroxide is further decomposed into hydroxyl ions and hydrogen ions. When a DC voltage is applied between the negative electrode 21 and the positive electrode 22, the hydrogen ions flow through the ion exchange membrane 2, and the negative electrode 21 and the positive electrode 22
It flows between. The magnitude of this current depends on the amount of glucose contained in urine. Therefore, the amount of glucose in the urine of the subject is determined from the magnitude of the current. (Formula 1) shows this reaction.

[0005]

Embedded image

That is, electrons generated by the decomposition reaction of hydrogen peroxide shown in Chemical formula 1 are transmitted between the negative electrode 21 and the positive electrode 22, and a current flows between the electrodes. A resistor is disposed in a circuit in which this current flows, and the voltage flowing across the resistor is measured to measure the current flowing, and this current is converted into the concentration of a specific substance.

[0007]

The conventional biosensor has a problem that continuous measurement cannot be performed. That is, it takes time for the generated hydrogen peroxide to adhere to the positive electrode surface of the electrode and to exit the reaction system. There is also a method in which a reverse charge is applied between the positive electrode and the negative electrode of the electrode to perform refreshing. However, this method also requires a refresh time of about 30 seconds.

[0008]

According to the present invention, one of the electrodes is brought into direct contact with urine, that is, opened to the atmosphere, so that the foam generated on the electrodes can be easily released into the atmosphere. The biosensor is capable of performing continuous measurement without deteriorating the charge transfer ability.

[0009]

DETAILED DESCRIPTION OF THE INVENTION According to the first aspect of the present invention, one of the electrodes is brought into direct contact with urine, that is, opened to the atmosphere, so that the foam generated on the electrodes can be easily introduced into the atmosphere. Can be released and the charge transfer ability is not degraded,
The biosensor is capable of continuous measurement.

[0010] The invention described in claim 2 is a biosensor which can eliminate even if an oxide is formed by using glucose oxidase as an enzyme and can perform accurate measurement.

[0011] The invention described in claim 3 is a biosensor capable of performing continuous measurement by using the electrode directly in contact with urine as a positive electrode, and the foam formed by the enzymatic reaction is immediately opened to the atmosphere.

According to a fourth aspect of the present invention, there is provided a biosensor in which the negative electrode is in contact with the ion exchange membrane, and the ion exchange membrane acts as an electron carrier, thereby enabling accurate measurement and continuous measurement. And

[0013]

Embodiments of the present invention will be described below. FIG. 1 is a cross-sectional view illustrating the configuration of the biosensor of the present embodiment. The biosensor of this embodiment includes a base 3a, a negative electrode 21 provided on the base 3a, an ion exchange membrane 2 provided on the base 3a so as to cover the negative electrode 21, , An interfering substance removing film 4, a positive electrode 22, a base 3b, and a base 3c.

The material of the bases 3a to 3c is not particularly limited as long as the bases 3a to 3c have sufficient strength to maintain the structure. In this embodiment, a molded article of polyethylene terephthalate is used. Also, the top base 3
There is an appropriate space between b and the base 3c, and this space is a urine collection port 5 for collecting urine.

The negative electrode 21 is provided on the base 3a, and the positive electrode 22 is provided on the interference substance removing film 4. The positive electrode 22 is partially exposed at the urine collection port 5. That is, the positive electrode 22 can directly contact urine, in other words, it is open to the atmosphere.

The interference substance removing film 4 is formed of a membrane film. The membrane film is porous with extremely small holes, and removes huge solid components other than glucose in urine, for example, urine protein (mainly albumin). Further, the interfering substance removing membrane 4 has a role of retaining the enzyme 1 adsorbed on the ion exchange membrane 2, and is greatly involved in its sustained release.

In this embodiment, glucose oxidase is used as the enzyme 1, and in this embodiment, the ion exchange membrane 2 is used.
It is provided by directly adsorbing it. Therefore, the ion exchange membrane 2
Is directly bonded to the free carbon atom of the enzyme 1 or is bonded via an oxygen molecule. For this reason, the enzyme 1 adsorbed on the surface of the ion exchange membrane 2 never has a layer structure and has a porous structure.

The operation of this embodiment will be described below.
Urine contains thousands of chemicals. The biosensor of this embodiment measures the sugar content, which is one of the indices indicating the health information of the human body. The sugar content is measured by representing glucose.

Urine is supplied to the urine collection port 5 with a DC voltage of about 1 V or less applied from a DC power supply (not shown) between the negative electrode 21 and the positive electrode 22. The urine supplied to the urine collection port 5 enters the inside through the interference substance removing film 4 provided at the uppermost part. The interfering substance removing film 4 is porous with an extremely small hole, and removes large solid components other than glucose, for example, urine protein (mainly albumin). Therefore, components that can enter the ion exchange membrane 2 are limited to urine components of relatively low molecular weight. At this time, in this embodiment, the enzyme 1 is disposed on the ion exchange membrane 2. The enzyme 1 selectively reacts only with glucose, and does not react with other urine substances.

Thus, glucose contained in urine is decomposed by the enzyme 1. At this time, in this embodiment, glucose oxidase is used as the enzyme 1 as described above. Glucose oxidase decomposes glucose in urine into gluconic acid and hydrogen peroxide as described in the conventional example. This hydrogen peroxide is further decomposed into hydroxyl ions and hydrogen ions. The hydrogen ions flow through the ion exchange membrane 2 when a DC voltage is applied between the negative electrode 21 and the positive electrode 22, and flow between the negative electrode 21 and the positive electrode 22.

That is, the generated hydrogen ions are exchanged for sodium ions in the ion exchange membrane 2, the hydrogen ion concentration in the ion exchange membrane 2 increases, and the hydrogen ions are guided toward the negative electrode 21. Thus, a current flows between the positive electrode 22 and the negative electrode 21. Even if an anion exchange membrane is used as the ion exchange membrane 2, anion exchange is performed on the ion exchange membrane 2. Therefore, the same current flows between the positive electrode 22 and the negative electrode 21.

A resistor is arranged in a circuit in which this current flows, and the current flowing is measured by measuring the voltage across the resistor, and this current value is converted into a glucose concentration. The magnitude of this current depends on the amount of glucose contained in urine. Therefore, the amount of glucose in the urine of the subject is determined from the magnitude of the current.

At this time, the DC voltage applied between the negative electrode 21 and the positive electrode 22 is preferably about 1 V or less as described above. The reason for this is that when the applied DC voltage increases, the current flowing due to the electrolysis of water in urine does not correspond to the amount of glucose.

At this time, glucose dehydrogenase can be used as the enzyme 1. When glucose dehydrogenase is used, hydrogen ions are generated when glucose is decomposed. Therefore, in this case, the electrode 22 shown in FIG. 1 can be used similarly as a negative electrode and the electrode 21 as a positive electrode.

At this time, in the present embodiment, the positive electrode 22 is provided at a position which is in direct contact with urine. That is,
At least a part of the positive electrode 22 is open to the atmosphere. For this reason, bubbles attached to the vicinity of the positive electrode 22 generated as a result of the reaction are easily released into the atmosphere. When bubbles are attached to the electrodes, the charge transfer ability is deteriorated, and accurate measurement cannot be performed. In this respect, in this embodiment, since the generated bubbles are immediately released into the atmosphere, the charge transfer ability does not decrease, and therefore, the sugar content in urine must be continuously measured. Becomes possible.

According to the present embodiment, the interference substance removing film 4
The urine component that has penetrated into the interior is released into the atmosphere because of the use of the urea. For this reason, the biosensor of this embodiment does not need to be disposable each time it is used, but can be used repeatedly.

It is to be noted that a one-time use disposable type biosensor must avoid contamination as much as possible in clinical tests such as measuring glucose concentration in a patient's blood and checking fermentation processes in the brewing industry. This is useful in areas where you have to do or where you have to work with numbers.

(Experiment 1) The results of an experiment conducted to verify the effect of the biosensor of this embodiment will be described below. In this experiment, the concentration of dissolved oxygen was compared between a case where the electrode was directly in contact with urine and a case where the electrode was not in contact with urine. A high dissolved oxygen concentration indicates that there are many bubbles generated near the electrode, which means that the measurement becomes inaccurate. In this experiment, the amount of generated oxygen was measured using a dissolved oxygen meter, and the measured temperature was 34 ° C. The concentration of glucose dropped on the biosensor is 500 mg / dl. The results of this experiment are shown in (Table 1). Note that the dissolved oxygen concentration is shown in ppm order.

[0029]

[Table 1]

As can be seen from the results, the amount of oxygen dissolved in the solution by the foaming phenomenon is larger in the structure in which the electrode and the urine are in direct contact, and smaller in the structure of the present embodiment. The reason is that if the positive electrode 22 is configured to come into contact with the atmosphere, the negatively charged substance in the raw urine is attracted to the vicinity of the positive electrode 22 and is easily released into the atmosphere therefrom. is there.

(Experimental Example 2) Next, an experiment for confirming the measurement accuracy of the apparatus of the present embodiment is performed. This experiment is
Using glucose whose concentration is known, it is checked whether the current flowing at this time is in accordance with the concentration. The glucose used in this experiment is 50 mg / dl, 250 mg / dl and 500 mg / dl. Glucose is prepared by dissolving glucose in phosphate buffered saline so as to have the above concentration. Further, the current flowing in the circuit is shown as a voltage generated across the resistor. The measurement results are shown in (Table 2).

[0032]

[Table 2]

As can be seen from Table 2, in the configuration of the present embodiment, the concentration of glucose and the value of the generated voltage are directly proportional. It is expensive.

[0034]

According to the first aspect of the present invention, there is provided an electrode which is energized at the time of measurement, an ion exchange membrane on which an enzyme is adsorbed, and an interfering substance removing film which removes interfering substances in urine. One is a configuration that comes into direct contact with urine, realizing a biosensor that can easily discharge foam generated on the electrode to the atmosphere, does not deteriorate the charge transfer ability, and can perform continuous measurement. It is.

The invention described in claim 2 realizes a biosensor that can eliminate even if an oxide is formed and that can perform accurate measurement by using glucose oxidase as the enzyme.

According to a third aspect of the present invention, there is provided a biosensor in which a foam formed by an enzymatic reaction is immediately opened to the atmosphere so that continuous measurement can be performed, in which the electrode directly in contact with urine is a positive electrode. Is what you do.

According to a fourth aspect of the present invention, there is provided a biosensor in which the negative electrode is in contact with an ion exchange membrane, the ion exchange membrane acts as an electron carrier, and accurate measurement is possible and continuous measurement is possible. Is realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a biosensor according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a configuration of a conventional biosensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Enzyme 2 Ion exchange membrane 3a base 3b base 3c base 4 Interfering substance removal membrane 5 Urine collection port 21 Negative electrode 22 Positive electrode

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G01N 33/483 G01N 27/30 353J 33/493 353A 27/46 338 F term (Reference) 2G045 AA16 BA01 BB04 DA31 FB01 FB05 4B029 AA07 BB16 CC03 CC11 FA12 4B063 QA01 QQ03 QQ15 QQ68 QR03 QS20 QS28 QS39 QX04

Claims (4)

[Claims] 1. An electrode which is energized at the time of measurement, an ion exchange membrane on which an enzyme is adsorbed, and an interfering substance removing membrane which removes an interfering substance in urine, wherein one of the electrodes is a biomaterial which directly contacts urine. Sensor. 2. The biosensor according to claim 1, wherein the enzyme is glucose oxidase. 3. The biosensor according to claim 1, wherein the electrode directly in contact with urine is a positive electrode. 4. The biosensor according to claim 1, wherein the negative electrode is in contact with an ion exchange membrane.