JPH09292355A - Biosensor - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a biosensor in which introduction of a biological sample is easy, and which can significantly suppress performance deterioration during storage in a high humidity environment and performance deterioration due to an adhesive. To do. SOLUTION: A substrate 1 having a base 1a having a predetermined shape and a narrow protrusion 1b protruding from a predetermined position of the base 1a, a cover member 2 having a planar shape substantially equal to the substrate 1, and the protrusion. It has an electrode system 3 provided at a predetermined position on the upper surface of 1b and reaction layers 4 and 4'provided at a predetermined position on the upper surface of the protrusion 1b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biosensor, and more particularly to a biosensor capable of quantifying a specific component contained in a small amount of biological sample.

[0002]

2. Description of the Related Art Conventionally, as a biosensor for quantifying a specific component in a biological sample such as blood, an electrode system and a reaction layer supporting an enzyme are provided on a substrate, and the electrode system is mounted on the substrate. And a first flat plate having a through hole including a reaction layer, a second flat plate is provided so as to cover the first flat plate, and an introduction port communicating with the through hole is provided at a predetermined position of the second flat plate. 1
There has been proposed a biosensor having a configuration in which each flat plate is provided with a lead-out port communicating with the through hole at a predetermined position.

With the biosensor having this structure, by introducing a biological sample such as blood from the inlet, the biological sample can be introduced into the reaction layer. In this reaction layer, the substance to be measured is reacted in the presence of the enzyme to produce a predetermined substance or to eliminate the predetermined substance. Then, an electric signal corresponding to the amount of the substance that is generated or lost is output from the electrode system. Therefore, it is possible to achieve the quantification of the specific measurement target substance in the biological sample based on the electrical signal output from the electrode system and the calibration curve obtained in advance.

[0004]

However, when the biosensor having the above-mentioned structure is adopted, since the inlet is relatively small, for example, a biological sample such as blood is directly introduced from a finger or the like. Therefore, there is an inconvenience that it becomes difficult to introduce the biological sample. Further, when directly introducing a biological sample such as blood from a finger or the like, if the finger or the like is too closely attached to the introduction port, the introduction port will be blocked and the biological sample cannot be introduced. There are also inconveniences.

Further, since the electrode system and the reaction layer are almost completely covered, when stored in a high humidity environment,
There is also a disadvantage that the performance of the biosensor deteriorates due to dew condensation inside the space including the electrode system and the reaction layer. Specifically, the electrical signal output from the electrode system changes considerably even if it is stored for 1 hour in an environment where the temperature is 35 ° C. and the humidity is 85%. This inconvenience seems to be caused by the fact that the dew condensation is absorbed by the water-absorbing material and the reaction layer is deformed. This is probably because the performance deteriorates only when the human body comes into contact with the reaction layer during the manufacturing process.

Furthermore, an adhesive or pressure-sensitive adhesive (hereinafter simply referred to as an adhesive) is indispensable for adhering the substrate, the first flat plate, and the second flat plate to each other, and the adhesive is used in the manufacturing process. The volatilized components have been for quite some time,
There is also an inconvenience in that the performance of the biosensor is deteriorated by being attached to the surface of the reaction layer or the like due to staying in the space.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is easy to introduce a biological sample, and further, performance deterioration during storage in a high humidity environment and performance deterioration due to an adhesive agent. It is an object of the present invention to provide a biosensor capable of significantly suppressing the above.

[0008]

A biosensor according to claim 1 is a substrate having an electrode system and a reaction layer carrying an enzyme,
In a test solution in the presence of an enzyme, the plate has a flat plate facing the substrate at a predetermined interval, and the gap is opened at the periphery of the plate and the flat plate to allow free flow of air inside the gap. The electric signal corresponding to the concentration of the substance generated or lost by the reaction of the measurement target substance is output from the electrode system.

In the biosensor of claim 2, the surface of the flat plate on the electrode system side is hydrophilic. A biosensor according to a third aspect of the present invention is such that a protrusion for holding a gap between the substrate and the flat plate is formed at a predetermined position of the flat plate.

[0010]

According to the biosensor of claim 1, the substrate has an electrode system and a reaction layer carrying an enzyme, and a flat plate facing the substrate at a predetermined interval. Since the gap is opened to allow the free flow of the air inside the gap, the test liquid can be introduced from any place in the part where the gap is open, and the finger etc. The test liquid can be introduced without any inconvenience even if they are brought into close contact with each other, and since the gap is opened to allow free flow of air, there is almost no inconvenience that air is trapped in the gap, and dew condensation occurs. It is possible to significantly suppress the performance deterioration due to the storage in a high humidity environment due to the difficulty of performing. Furthermore, since the gap is opened in a wide range, the amount of adhesive used can be reduced, and the application position of the adhesive can be sufficiently separated from the electrode system and the reaction layer. In addition, the volatile component from the adhesive is rapidly diffused to the outside due to the high fluidity of the air, and the performance deterioration can be greatly suppressed.

According to the biosensor of claim 2, since the surface of the flat plate on the side of the electrode system has hydrophilicity, it is possible to facilitate the introduction of the test liquid, and the same as in claim 1. The action of can be achieved. According to the biosensor of claim 3, since the protrusion for holding the gap between the substrate and the flat plate is formed at a predetermined position of the flat plate, the desired gap can be kept maintained. It is possible to achieve the same effect as that of claim 1 or claim 2.

[0012]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 is an exploded perspective view showing an embodiment of the biosensor of the present invention, FIG. 2 is an enlarged plan view showing a main part, and FIG. 3 is a sectional view taken along the line III-III of FIG. This biosensor includes a base 1a having a predetermined shape and a narrow protrusion 1b formed by protruding from a predetermined position of the base 1a.
And a cover member 2 having substantially the same planar shape as the substrate 1, an electrode system 3 provided at a predetermined position on the upper surface of the protrusion 1b, and a electrode member 3 provided at a predetermined position on the upper surface of the protrusion 1b. It has reaction layers 4 and 4 '.

The cover member 2 has a protrusion 1b on the substrate 1.
Only a portion corresponding to is formed thin and a predetermined gap is formed between the projecting portion 1b and the cover member 2 in a state where the cover member 2 is adhesively fixed to the substrate 1. Here, the width of the protruding portion 1b is, for example, 1.2 mm or 1.5 mm.
And the gap is, for example, 250 μm or 50 μm.
It is set to 0 μm. By setting the width and the gap in this way, it is possible to obtain a sufficient capillary phenomenon when introducing the test liquid, and it is possible to enhance the fluidity of air in the space between the protrusion 1b and the cover member 2. . Here, the gap is open in most of the periphery of the gap, but may be open in the range of 1/2 or more.

The electrode system 3 includes a first counter electrode 3a and a first counter electrode 3a.
The working electrode 3b, the second counter electrode 3c, the second working electrode 3d, and the third counter electrode 3e are arranged in this order on the projecting portion 1b and in the longitudinal direction of the projecting portion 1b, and at the same time, the third counter electrode 3e. On the other hand, the reference electrode 3f is formed in a state of being juxtaposed in the width direction of the protruding portion 1b. The reaction layer 4 has a first
Counter electrode 3a, first working electrode 3b, and second counter electrode 3
The reaction layer 4'covers the second counter electrode 3c, the second working electrode 3d, the third counter electrode 3e, and the reference electrode 3f. The reaction layer 4 includes the first counter electrode 3a, the first working electrode 3b, and the second counter electrode 3c.
And an overcoat film 4b that covers the entire area of the immobilized enzyme film 4a.
The reaction layer 4'includes a second counter electrode 3c, a second working electrode 3d,
4a ′ covering the third counter electrode 3e and the reference electrode 3f,
The overcoat film 4b 'covers the entire area of 4a'.

On the edge of the base 1a opposite to the protrusion 1b, four contacts are provided side by side, and the first counter electrode 3a, the first working electrode 3b, the second counter electrode 3c, and the second counter electrode 3c. Two
The working electrode 3d, the third counter electrode 3e, and the reference electrode 3f are electrically connected to the corresponding contacts by wiring. However, all three counter electrodes are connected to one contact.

FIG. 4 is a perspective side view schematically showing the structure of an apparatus for measuring the concentration of a substance to be measured in a biological sample using the biosensor having the above structure. This apparatus includes a main body casing 11, a sensor cartridge 12 that accommodates a predetermined number of sensor single bodies 10 including the biosensor having the above-described configuration in a stacked state, and an operation member 13 that sends out the sensor single bodies 10 from the sensor cartridge 12 one by one. A signal indicating the concentration of the substance to be measured by applying a predetermined bias voltage to the sensor single unit 10 and performing processing (differentiation processing, maximum value detection processing, or the like) based on the electric signal output from the sensor single body 10. A signal processing unit (not shown) that outputs a signal, a concentration display unit 14 that visually displays the concentration of the target substance, and a power supply unit 1 that supplies an operating voltage to the signal processing unit.
5 is provided.

The sensor unit 10 further has a flat plate member that extends outward from the contact side edge of the biosensor having the above-described structure, and exposes the upper surface of the flat plate member to the outside and exposes it to the exposed portion. It has a contact electrically connected to the contact. The sensor cartridge 12 has an urging member 12a composed of a coil spring or the like for urging the stacked sensor single bodies 10 upward, and a sending opening for allowing the sensor single body 10 located at the uppermost part to be sent out. (Not shown) and an opening for receiving an operating member (not shown) that allows the tip of the operating member 13 to enter.
In addition, when the sensor unit 10 is sent out by a predetermined length shorter than the total length of the biosensor, the contact point of the flat plate member and the contact point (not shown) provided at a predetermined position of the main body casing 11 are provided. ) Has an opening (not shown) that allows electrical connection with the device. The sensor cartridge 12 is housed in the main body casing 11 so as to be removable.

FIG. 5 is an electric circuit diagram showing a main part of an electric circuit for measuring concentration. The first working electrode 3b is connected to the inverting input terminal of the operational amplifier 21, and the operational amplifier 2
The work electrode potential is supplied to the non-inverting input terminal of No. 1 and the resistor 21a is provided between the inverting input terminal and the output terminal of the operational amplifier 21.
To form a first current-voltage converter, connect the second working electrode 3d to the inverting input terminal of the operational amplifier 22, and supply the work electrode potential to the non-inverting input terminal of the operational amplifier 22 to The resistor 22a is connected between the inverting input terminal and the output terminal to form a second current-voltage converter, and the inverting input terminal of the operational amplifier 23, to which the applied voltage that is changed is supplied to the non-inverting input terminal, is connected to the counter electrode 3
The output terminal of the operational amplifier 23 is connected to the reference electrode 3f while being connected to a, 3c, and 3e.

Therefore, by fixing the work electrode potential and changing the applied voltage, a reverse bias for refreshing and a forward bias for measurement can be supplied. Then, the first working electrode 3b and the second working electrode 3d
The current output from can be converted into a voltage by a current-voltage converter. This converted voltage is, for example, A /
The signal is converted into a digital signal by the D converter and supplied to the signal processing unit.

When the concentration of the substance to be measured in the biological sample is measured using the apparatus having the above-described structure, first, the operating member 13 is operated to make the uppermost sensor unit 10 shorter than the entire length of the biosensor. It is sent out for a predetermined length, and an electrical connection between the biosensor and the main body casing 11 side is achieved. In this state, if the distal end of the portion consisting of the protruding portion 1b of the substrate 1 and the cover member 2 is brought close to the biological sample intake portion (for example, a finger or the like), the biological sample will be ejected by the capillary phenomenon. It is introduced into the gap between the two.

The introduced biological sample is passed through the overcoat membranes 4b and 4b ', and the immobilized enzyme membrane 4a and membrane 4a'.
And the substance to be measured in the biological sample guided to the membrane 4a ′ performs a predetermined reaction. Specifically, for example, when glucose oxidase is used as the enzyme, glucose and water in the biological sample react in the presence of glucose oxidase to generate gluconolactone and hydrogen peroxide. Then, in the second working electrode 3d, hydrogen peroxide is decomposed to generate hydrogen ions, oxygen and electric charges, and in the counter electrodes 3c and 3e, water is generated from the hydrogen ions, oxygen and electric charges generated by the decomposition. Let Therefore, due to these reactions, a current corresponding to the glucose concentration is output from the second working electrode 3d. Also,
From the first working electrode 3b, a current irrelevant to the glucose concentration (current caused by interfering substances such as blood cells) is output. Therefore, by converting the current output from both working electrodes into a voltage and taking the difference, a voltage corresponding to only the glucose concentration can be obtained.By supplying this voltage to the signal processing unit, the glucose concentration can be changed. A corresponding electric signal can be obtained and visually displayed by the concentration display unit 14.

After that, the operating member 13 is further operated in the same direction as described above, whereby the uppermost sensor unit 1
0 can be sent out by a length substantially equal to its total length, and can be naturally dropped from the main body casing 11. And
When the operation member 13 is moved back, all the sensor units 10 in the sensor cartridge 12 are pushed up by the biasing member 12a, and the next measurement can be prepared.

Further, as is apparent from the above description, even if the sensor unit 10 is individually packaged in a state of containing a desiccant after manufacturing, the packaging is discarded at the time of being housed in the sensor cartridge 12. Therefore, in a high-humidity environment, the sensor output fluctuates due to dew condensation or the like. In this case, like the conventional biosensor, if the electrode system and the reaction layer are completely enclosed except for the inlet and outlet, the fluidity of the air is extremely low, so that dew condensation may occur as the temperature decreases. Then, as shown in FIG. 6B, the sensor output fluctuates significantly. But,
In the biosensor of this embodiment, the protruding portion 1b of the substrate 2 is
Since the almost entire range of the gap formed by the cover member 2 and the cover member 2 is open, the fluidity of air is increased, and the fluctuation of the sensor output can be significantly reduced as shown in FIG. 6 (A). it can. In addition, the measurement result of FIG.
It was obtained by carrying out the measurement using 100 mg / dl test liquid after opening and storing at 90% H.

If the biosensor of this embodiment is adopted, the concentration of the substance to be measured can be measured with a remarkably small amount of the biological sample (for example, about 2 μl), and as a result, the influence of dissolved oxygen in the biological sample can be reduced. Hard to receive. Further, since the capillary phenomenon is used for introducing the biological sample, the operability is remarkably improved, and the influence of interfering substances such as blood cells can be almost eliminated. Further, it can be stored in a normal temperature and normal humidity atmosphere for a considerably long period of time, and furthermore, fluctuations in sensor output can be greatly suppressed.

In the above-described embodiment, the gap between the protrusion 1b and the cover member 2 is ensured by the shape retention of the cover member 2. However, the gap can be held more reliably. It is preferable that the protruding shaft member of the cover member 2 is provided so as to correspond to the tip of the protruding portion 1b.

[0026]

According to the invention of claim 1, the test liquid can be introduced from any place as long as the gap is open, and the test liquid can be introduced without any inconvenience even if a finger or the like is too closely attached. It can be introduced, and since the gap is open to allow free flow of air, there is almost no inconvenience that air is trapped in the gap, and it is difficult for dew condensation to occur in high humidity environments. It is possible to significantly suppress the deterioration of performance due to storage and to open the gap in a wide range, so it is possible to reduce the amount of adhesive used and to apply the adhesive. The position can be sufficiently separated from the electrode system and the reaction layer, and moreover, the volatile component from the adhesive is rapidly diffused to the outside due to the high fluidity of air, and by extension,
A unique effect is that performance deterioration can be significantly suppressed.

The invention of claim 2 can facilitate the introduction of the test liquid and has the same effect as that of claim 1. According to the invention of claim 3, the desired gap can be maintained, and the same effect as that of claim 1 or 2 can be obtained.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a biosensor of the present invention.

FIG. 2 is an enlarged plan view showing a main part of FIG.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

FIG. 4 is a perspective side view schematically showing the configuration of an apparatus for measuring the concentration of a measurement target substance in a biological sample using the biosensor of FIG.

FIG. 5 is an electric circuit diagram showing a main part of an electric circuit for measuring concentration.

FIG. 6 is a diagram showing a change in sensor output with respect to the number of days of storage of a biosensor.

[Explanation of symbols]

 1 substrate 2 cover member 3 electrode system 4 reaction layer

Claims (3)

[Claims] 1. A substrate (1) having an electrode system (3) and a reaction layer (4) carrying an enzyme, and a flat plate (2) facing the substrate (1) at a predetermined interval. , A gap is opened at the periphery of the substrate (1) and the flat plate (2) to allow free flow of air inside the gap, and is generated by the reaction of the substance to be measured in the test liquid in the presence of the enzyme. , Or a biosensor which outputs an electric signal corresponding to the concentration of the substance to be eliminated from the electrode system (3). 2. The biosensor according to claim 1, wherein a surface of the flat plate (2) on the side of the electrode system (3) has hydrophilicity. 3. The bio according to claim 1 or 2, wherein a protrusion for holding a gap between the substrate (1) and the flat plate (2) is formed at a predetermined position of the flat plate (2). Sensor.