JPH09285459A - Biosensor - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a biosensor that enables easy measurement operation and enables reliable component concentration measurement. SOLUTION: A compression coil spring 13A is provided in a sensor body 3.
The sensor unit 2 is inserted through the switch mechanism 14
The sensor unit 2 is locked by the
The main body cover 4 is mounted with the unit sensor 2 inserted therein. Therefore, the switch mechanism 1
4 prevents the sensor unit 2 from being fired. A blood introduction path 5C is formed in the needle 5 of the sensor unit 2, and the blood introduction path 5C is electrically connected to the space inside the slit 10 of the spacer 7. In this space, the counter electrode and the working electrode are arranged so as to face each other.
With such a configuration, the needle 5 can be easily operated.
The blood introduced from (1) can be brought into contact with the counter electrode and the working electrode at the same time, and the substrate concentration can be reliably measured.

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 for measuring the concentration of various components in blood.

[0002]

2. Description of the Related Art Conventionally, as a biosensor for measuring the concentration of components in blood, for example, a biosensor in which a working electrode (anode) and a counter electrode (cathode) are arranged at a predetermined distance on a single substrate is known. ing. An enzyme that causes an enzyme reaction with a predetermined component is immobilized on the surface of the working electrode. The procedure described below is used to measure the concentration of components in blood using such a biosensor. First, scratch the skin surface with a needle attached to a blood collection device prepared separately,
Blood that appears on the surface of the skin is collected using a blood sampling device. Next, the collected blood is dropped by a blood collecting instrument so as to come into contact with the working electrode and the counter electrode of the biosensor.
In this way, with blood in contact with both electrodes, a predetermined voltage is applied between both electrodes, and the current value flowing between both electrodes is measured to determine the concentration of blood components that cause an enzymatic reaction. There is.

[0003]

However, in the above-mentioned conventional biosensor, a technique for accurately mounting blood on the biosensor is required. Further, in the conventional biosensor, the measured current value may change depending on the amount of blood contacting both electrodes. In addition to the biosensor having the above-described configuration, a configuration in which a working electrode and a counter electrode provided on separate substrates are opposed to each other and blood is introduced between both electrodes by utilizing a capillary phenomenon has been proposed. However, it is similar to the above-described biosensor in that a blood sampling instrument is used, and it requires at least two operations of a blood sampling step and a measurement step. In particular, when using a blood sampling device, more blood than is necessary for measurement was required.

The problem to be solved by the present invention is what kind of means should be taken in order to obtain a biosensor which is simple in measurement operation and which enables reliable component concentration measurement.

[0005]

According to the first aspect of the present invention,
A sensor having a sampling needle having a test liquid introducing path, a test liquid introducing space communicating with the test liquid introducing path, and a counter electrode and a working electrode provided on opposite surfaces of the test liquid introducing space It is characterized by having a unit.

According to the first aspect of the invention, since the test solution introducing space provided with the counter electrode and the working electrode communicates with the sampling needle, the test solution can be simply measured by directly collecting the test solution from the sampling needle. be able to. Further, since the test liquid can be sampled in a small amount and quantitatively by setting the volume of the test liquid introduction space, it is possible to measure with high accuracy.

According to a second aspect of the invention, a sensor main body in which a unit insertion space for inserting the sensor unit and a spring for urging the sensor unit are arranged, and the sensor unit is predetermined from an opening of the unit insertion space. Locking means for locking the sensor unit in a state of being inserted against the biasing force of the spring to a position, and attached to the opening side of the unit insertion space of the sensor unit,
A main body cover that projects only the sampling needle of the sensor unit outward when the locked state of the locking means is released.

According to the second aspect of the invention, when the sensor unit which is locked by the locking means at the predetermined position of the unit insertion space of the sensor body is released from the locked state, it is pushed out by the biasing force of the spring and only the sampling needle is taken. Protrudes outward, and the test liquid can be collected.

According to a third aspect of the present invention, a connector for individually contacting the counter electrode and the working electrode of the sensor unit with the sampling needle of the sensor unit protruding from the inner wall of the body cover or the sensor body. It is characterized in that members are arranged. In the invention according to claim 3, it is set so that the measurement of the substrate concentration in the test liquid is started with the sampling needle protruding from the main body cover.
Therefore, the concentration can be automatically measured when the locking state of the locking means is released.

The invention according to claim 4 is characterized in that the working electrode is formed with an enzyme immobilizing layer containing an enzyme which causes an enzyme reaction with a substrate in a test solution, or an enzyme and a mediator. . In the invention according to claim 4, the substrate undergoes an enzymatic reaction by receiving a catalytic action of the enzyme,
The substrate concentration can be determined by measuring the current flowing between the counter electrode and the working electrode. In the enzyme immobilization layer containing the enzyme and the mediator, for example, when the enzyme that has been converted to the reduced form by oxidizing the substrate returns to the original oxidized form, the mediator takes an electron from the enzyme and becomes the reduced mediator, and this reduction Type mediators donate electrons to the electrodes by an electrode reaction, which returns them to the original oxidized mediators. That is, if the substrate is present in the enzyme immobilization layer containing the enzyme and the mediator, the electron moves to the electrode via the enzyme and the mediator, and a current corresponding to the substrate concentration flows. Therefore, the substrate concentration can be determined by detecting this current.

According to a fifth aspect of the present invention, one end of the spring is fixed to the sensor body side, and a unit fixing piston for detachably mounting the sensor unit is fixed to the other end of the spring. Is characterized by. In the invention according to claim 5, since the sensor unit can be fixed to the unit fixing piston, it is possible to prevent the sensor unit from being fired from the sensor main body even when the main body cover is not attached to the sensor main body.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, details of a biosensor according to the present invention will be described based on embodiments shown in the drawings.

1 and 2 are sectional explanatory views of the biosensor according to the present embodiment, FIG. 3 is an exploded perspective view of the sensor unit, FIG. 4 is a sectional view of the sensor unit, and FIG. 5 is a partial sectional perspective view of the main body cover. 6 is an equivalent circuit diagram.

The configuration of the biosensor according to this embodiment will be described. As shown in FIGS. 1 and 2, the biosensor 1
Is composed of a sensor unit 2, a sensor body 3, and a body cover 4. A feature of the configuration of the biosensor 1 is that the sensor body 2 is loaded with the sensor unit 2 and the body cover 4 is attached. Therefore, in the present embodiment, the sensor unit 2 can be easily replaced.

The structure of the sensor unit 2 will be described in detail below. As shown in FIGS. 1 to 4, the sensor unit 2 is configured by integrally combining a needle 5 as a blood collecting needle, a counter electrode base body 6, a spacer 7, and a working electrode base body 8.

Like the well-known injection needle, the needle 5 has a blood introducing passage 5C penetrating from the vicinity of the apex (distal end) 5A toward the proximal end 5B. The diameter of this needle 5 is 1 mm
Although the diameter of the blood introducing passage 5C is about 0.2 mm, the needle 5 is drawn to have a relatively large diameter in the figure for convenience of description. A flat surface 5D for positioning is formed along the lengthwise direction on the peripheral side surface of the needle 5 near the base end 5B. In other words, the cross section of the portion of the needle 5 near the base end 5B has a circular shape in which a part of the arc is cut off. Further, the length of the needle 5 is set to be relatively short because it is sufficient that the needle 5 is stabbed shallowly from the skin surface of the human body as described later.

Next, the structure of the counter electrode substrate 6 will be described. The counter electrode substrate 6 is made of an electrically insulating material and is formed into a cylindrical container shape as shown in FIG. That is, a needle insertion port 6A for tightly fitting the base end 5B of the needle 5 described above is formed on the front surface of the counter electrode substrate 6. Then, as shown in FIG. 4, the bottom plate 6C of the counter electrode substrate 6 is formed with an inlet port 6D which communicates with the blood inlet passage 5C of the needle 5. Note that reference numeral 6B shown in FIG. 3 is a flat insertion port side wall corresponding to the flat surface 5D for positioning the needle 5. In such a structure, the base end 5B of the needle 5 has the needle insertion opening 6A.
It is attached and fixed to. Further, on the rear surface of the counter electrode substrate 6, a counter electrode (cathode) 9 made of an electrode material is formed at a predetermined position so as to be exposed. Further, a counter electrode connector (counter electrode contact electrode) 9A electrically connected to the counter electrode 9 is formed at a predetermined position on the peripheral surface of the counter electrode substrate 6.

The spacer 7 is made of an electrically insulating material and is formed into a disk shape having the same diameter as the counter electrode substrate 6. And, in this spacer 7,
A slit 10 is formed by cutting out toward the center of the disc. The spacer 7 is the counter electrode substrate 6 described above.
A slit 10 is adhered and fixed to the rear surface of the counter electrode base 6 so as to face the counter electrode 9.

Next, the structure of the working electrode substrate 8 will be described. The working electrode substrate 8 has a substantially disc structure having the same diameter as the spacer 7 and the counter electrode substrate 6 described above. The working electrode substrate 8 is also made of a material having an electric insulating property. Further, as shown in FIG. 3, a working electrode 11 made of a predetermined electrode material is formed at a predetermined position on the front surface of the working electrode substrate 8. An enzyme-immobilized layer 12 is formed at the tip of the working electrode 11, for example, glucose oxidase (GOD) and bovine serum albumin (BSA) are immobilized. further,
A working electrode connector (working electrode contact electrode) 11A electrically connected to the working electrode 11 is formed on the peripheral surface of the working electrode substrate 8. In addition, as shown in FIG.
A positioning protrusion 8A that protrudes rearward is formed in the center of the rear surface. The positioning protrusion 8A may be a protrusion having an appropriate shape such as a one-letter shape or a cross shape when viewed from the rear. The working electrode substrate 8 having such a structure is adhered and fixed to the rear surface of the spacer 7 so that the working electrode 11 and the enzyme immobilization layer 12 face the slit 10 of the spacer 7.

The mutual positional relationship among the needle 5, the counter electrode substrate 6, the spacer 7 and the working electrode substrate 8 will be described below.
Positioning plane 5 formed on the peripheral surface of the proximal end 5B of the needle 5.
D, and the insertion port side wall 6B in the needle insertion port 6A of the counter electrode substrate 6
When the needle 5 is fitted into the counter electrode base body 6 so that and, overlap with each other, both the needle 5 and the counter electrode base body 6 are closely fitted and positioned. At this time, the blood introduction path 5C of the needle 5 and the introduction port 6D of the counter electrode substrate 6 are set to communicate with each other. Also,
As described above, the counter electrode 9 formed on the counter electrode substrate 6, the inlet 6D and the working electrode 11 (including the enzyme immobilization layer 12) formed on the working electrode substrate 8 are formed by the slits 10 formed in the spacer 7. It is set to face the space formed. Therefore, the counter electrode 9 and the working electrode 11 (enzyme immobilization layer 12
(Including) are opposed to each other through the space in the slit 10. The space inside the slit 10 sandwiched between the bottom surface (rear surface) of the counter electrode substrate 6 and the front surface of the working electrode substrate 8 becomes a blood introducing space 10A. Then, the counter electrode connector 9A formed on the peripheral surface of the counter electrode base 6, and the working electrode base 8
The working electrode connector 11A formed on the circumferential surface of the above is set so as to be displaced from each other by a predetermined angle in the circumferential direction. The positioning projection 8A formed at the center of the rear surface of the working electrode substrate 8 has a positioning function with respect to a member on the sensor body 3 side, which will be described later.

Next, the structure of the sensor body 3 on which the above-mentioned sensor unit 2 is mounted will be described. Sensor body 3
1 has a substantially cylindrical container-like structure in which a cylindrical unit insertion space 3A into which the sensor unit 2 can be inserted in the axial direction is formed, as shown in FIGS. 1 and 2. The diameter of the unit insertion space 3A is set to be substantially the same as the outer diameter of the sensor unit 2. Also, this unit insertion space 3A
A substantially columnar unit-fixing piston 13 can be slidably fitted in the front and rear direction. That is, the outer diameter of the unit fixing piston 13 is also set to be substantially the same as the outer diameter of the sensor unit 2. Then, one end of the compression coil spring 13A is fixed to the center of the bottom surface inside the sensor body 3. The other end of the compression coil spring 13A is fixed to the center of the rear surface of the unit fixing piston 13 described above. Further, on the front surface of the unit fixing piston 13, there is formed a positioning groove 13B into which the above-mentioned positioning projection 8A of the working electrode base 8 is fitted and fixed. Although not shown, the unit fixing piston 13
The unit fixing piston 13 and the inner wall of the sensor body 3 are provided with a rotation preventing mechanism that is engaged with each other and is slidable only in the length direction so that the unit does not rotate about the axis in the unit insertion space 3A. There is. On the outer surface of the opening at the front end of the sensor main body 3, a screw portion 3B to which a screw portion 4B of the main body cover 4 described later is screwed is formed. A switch mechanism 14 is provided near the opening of the sensor body 3. The sensor body 3 has lead wires 16A and 16B which are respectively connected to a counter electrode contact plate 17A and a working electrode contact plate 17B of the body cover 4 which will be described later when screwed with the body cover 4.
Is provided.

The structure of the switch mechanism 14 will be described below with reference to FIGS. 1 and 2. First, this switch mechanism 1
Reference numeral 4 denotes two bearing pieces 14A facing each other, which are provided so as to project to the outer surface of the sensor body 3, and a pivot shaft 14B provided between the two bearing pieces 14A.
And a pivot rod 14 having an intermediate portion pivotally supported by the pivot shaft 14B.
C, a locking pin 14D that engages with the front end side of the pivot rod 14C, and penetrates the side wall of the sensor body 3 and appears in and out of the unit insertion space 3A, so that the pivot rod 14C falls forward. The torsion coil spring 14 </ b> E that urges the spring is generally configured. A guide hole 14G is formed in the front portion of the pivot rod 14C along the longitudinal direction. A guide shaft 14H is provided at the upper end of the locking pin 14D described above. The guide shaft 14H is slidably engaged with the guide hole 14G. The locking pin 14D moves in and out of the unit insertion space 3A as the pivot rod 14C pivots. At this time, the guide shaft 14H has a guide hole 14G.
Is guided by sliding along. The locking pin 14
D has a function of locking the front end of the counter electrode substrate 6 and preventing the sensor unit 2 from jumping forward when the sensor unit 2 is inserted into the unit insertion space 3A of the sensor body 3.

Next, the structure of the main body cover 4 will be described with reference to FIGS.
This will be described with reference to FIG. The main body cover 4 is formed in a tubular shape from an electrically insulating material such as a resin material. Inside the main body cover 4, there are provided a counter electrode contact plate 17A and a working electrode contact plate 17B to which the counter electrode connector 9A and the working electrode connector 11A are respectively connected when the sensor unit 2 projects, and the counter electrode contact plate 17A. The working electrode contact plate 17B is connected to the lead wires 16A and 16B of the sensor body 3 when the sensor body 3 and the body cover 4 are screwed together. Further, the opening at the front end of the main body cover 4 is formed by a flange-shaped flange portion 4 </ b> A that circulates inward. Therefore, the inner diameter of the flange portion 4A is shorter than the inner diameter of the inner (rear) portion thereof. Further, on the inner wall of the opening at the rear end of the main body cover 4, a screw portion 4B that is screwed with the above-mentioned screw portion 3B of the sensor main body 3 is formed. The inner walls of the sensor body 3 and the body cover 4 are set to be flush with each other when the threaded portions of the sensor body 3 and the body cover 4 are screwed together. That is, the sensor main body 3 and the main body cover 4 except for the flange portion 4A and the screw portion 4B of the main body cover 4.
The inner diameter dimensions of are set to be the same. Therefore, in a state where the sensor unit 2 is housed in the unit insertion space 3A of the sensor main body 3 and the main body cover 4 is assembled to the sensor main body 3, even when the sensor unit 2 is advanced to the maximum,
Since the counter electrode base body 6 engages with the flange portion 4A at the peripheral edge portion of the front end surface, only the needle 5 projects from the front surface of the main body cover 4.

Here, the configurations of the main body cover 4 and the sensor unit 2 will be supplemented with reference to FIG. 2 showing a state where the sensor unit 2 has advanced to the maximum. When the locking pin 14D is sunk from the inner wall surface of the sensor body 3 due to the operation of the switch mechanism 14, the front surface of the counter electrode base 6 of the unit sensor 2 engages with the flange portion 4A by the urging force of the compression coil spring 13A.
At this time, the locking pin 14D is locked again in the unit insertion space 3A.
It is designed to prevent it from protruding inside. That is, in the state where the sensor unit 2 is pushed out to the flange portion 4A, the tip of the locking pin 14D is set to contact the peripheral surface of the unit fixing piston 13. Further, in the state where the sensor unit 2 is pushed out to the flange portion 4A, the counter electrode connector 9 of the sensor unit 2 is
A is connected to the counter electrode contact plate 17A, and the working electrode connector 11A is connected to the working electrode contact plate 17B.
The counter electrode contact plate 17A and the working electrode contact plate 17A
B is formed of an electrode material, and leads 16A, 16B
Connected to each other. These lead wires 16A, 1
6B are connected from the outside of the main body cover 4 so as to penetrate the main body cover 4 so that one ends thereof reach the contact plate. The other ends of the lead wires 16A and 16B are connected to a voltage applying circuit 18 and a current measuring circuit 19 which will be described later.
It is connected to the.

Next, the circuit configuration of the blood glucose level measuring system in the biosensor 1 of this embodiment will be described using the equivalent circuit shown in FIG. As shown in the figure, the counter electrode 9 is connected to a voltage application circuit 18 and a current measurement circuit 19 via a counter electrode connector 9A, a counter electrode contact plate 17A, and a lead wire 16A. The working electrode 11 (including the enzyme immobilization layer 12) includes a working electrode connector 11A and a working electrode contact plate 17.
It is connected to the voltage applying circuit 18 and the current measuring circuit 19 via B and the lead wire 16B. Further, the current measuring circuit 19 is connected to the computing means 20 and the display means 21. The current measuring circuit 19 is the voltage applying circuit 18
Is set so that the sample is filled between the counter electrode 9 and the working electrode 11, and the current value is measured after a lapse of a predetermined time from the start of the voltage application. Further, the voltage application circuit 18 is set to stop the voltage application after a longer time has elapsed from the start of the voltage application.

Next, the operation method, action, and operation of the biosensor 1 of this embodiment will be described. First, the sensor unit 2 is fixed by fitting the positioning protrusion 8A formed on the rear surface of the working electrode substrate 8 of the sensor unit 2 into the positioning groove 13B of the unit fixing piston 13 provided in the sensor body 3. At this time, the unit fixing piston 13 is connected to the sensor body 3 as described above.
The sensor unit 2 is fixed to the unit fixing piston 13 because it is set so as not to rotate inside.
Also does not rotate. Then, the sensor unit 2
The operation of pushing the compression coil spring 13A into the unit insertion space 3A is performed against the biasing force of the compression coil spring 13A. At this time, when the rear end of the unit fixing piston 13 is located in front of the locking pin 14D, the pivot rod 14C is operated (pivot rod 1
By pushing the rear end portion of 4C toward the sensor body 3, it is necessary to bring the locking pin 14D into a state of being sunk from the inner wall of the sensor body 3. When the front end of the counter electrode base body 6 of the sensor unit 2 advances to the rear of the locking pin 14D, the biasing force of the torsion coil spring 14E is applied to the locking pin 14D by the pivot rod 1.
4C, the unit insertion space 3
It projects into A. By thus projecting the locking pin 14D into the unit insertion space 3A, the front end of the sensor unit 2 is locked by the locking pin 14D, and the sensor unit 2 is set in a state in which it is prevented from jumping forward. It

Next, the case where the blood glucose level is measured using the biosensor 1 with the sensor unit 2 set as described above will be described. First, biosensor 1
The opening of the body cover 4 of the sensor mechanism 3 is applied to the skin of a person's arm or the like, and the rear end of the pivot rod 14C of the switch mechanism 14 is attached to the sensor body 3
Hold it against the outer wall of. As a result, the pivot rod 14C
It rotates clockwise in the figure and pulls the locking pin 14D toward the outside of the sensor body 3. When the tip of the locking pin 14D is sunk from the inner wall of the sensor body 3, the sensor unit 2 is moved by the biasing force of the compression coil spring 13A so that the counter electrode base 6
The front end surface of the is projected forward until it contacts the flange portion 4A. At this time, only the needle 5 projects from the opening of the main body cover 4 and pierces the skin, damaging the subcutaneous capillaries. Along with this, blood is introduced into the blood introduction space 10A through the blood introduction path 5C of the needle 5 and the introduction port 6D of the counter electrode substrate 6 by the capillary phenomenon. At this time, the counter electrode connector 9A and the working electrode connector 11A are respectively connected to the counter electrode contact plate 17A and the working electrode contact plate 17B, and a predetermined voltage is applied between the counter electrode 9 and the working electrode 11 by the voltage applying circuit 18. Voltage is being applied. Thereafter, the enzyme in the enzyme immobilization layer 12 causes glucose in the blood to undergo an enzymatic reaction (a reaction in which glucose is oxidized), and the glucose is contained in the enzyme immobilization layer 12.
A current corresponding to the glucose concentration in blood, that is, the blood glucose level, flows between the counter electrode 9 and the working electrode 11 via the dissolved oxygen that is an electron acceptor (via the mediator when the mediator is included). It is possible to measure the current value according to the above-mentioned blood glucose level by measuring the current with the current measuring circuit 19 after a predetermined time has elapsed since the voltage application circuit 18 started applying the voltage between the electrodes 9 and 11. . It should be noted that the current after a certain period of time has passed after the voltage application is proportional to the glucose concentration in a certain concentration range. Therefore, by inputting a proportional coefficient into the calculating means 20 in advance, the current value is converted into the concentration and displayed. The blood glucose level can be displayed on the means 21. In addition, after such blood glucose level measurement is performed,
Further, the voltage application of the voltage application circuit 18 is stopped after a predetermined time has elapsed.

After the measurement of the blood glucose level is completed in this way, the main body cover 4 may be removed from the sensor main body 3, and then the sensor unit 2 may be removed from the unit fixing piston 13. When the blood glucose level is measured again, the sensor unit 2 may be replaced and the above operation may be repeated.

In the present embodiment, the amount of blood required for measurement can be set to a predetermined volume in the blood introducing space 10A, so that the volume is constant and extremely small (the space volume of the path for introducing blood may be extremely small. Therefore, there is no problem of unreasonably drawing blood, and since the blood can be collected quantitatively, the generated current can also be measured quantitatively, and the blood glucose level can be measured with high accuracy. Also, since it is only necessary to stab the needle 5,
The amount of bleeding from the skin can be suppressed. In addition, this embodiment has an advantage that blood introduction and measurement can be performed in one step without the need for a blood sampling device. further,
Since blood is introduced between the counter electrode 9 and the working electrode 11 by utilizing the capillary phenomenon, there is an advantage that the measurement can be reliably performed.

Although the present embodiment has been described above, the present invention is not limited to this, and various modifications accompanying the gist of the configuration can be made. For example, in the above embodiment, glucose oxidase was used as the enzyme,
Of course, other enzymes may be immobilized in order to measure the concentrations of other components in blood, such as lactic acid, alcohol, cholesterol, uric acid and the like. Further, the enzyme immobilization layer 12 may include a mediator. Further, in the above-described embodiment, the cylindrical sensor main body 3 is used, but the cross-sectional shape may not be circular as a matter of course. Furthermore, the contact plate that contacts each connector formed on the peripheral surface of the sensor unit 2 may be formed not on the main body cover 4 but on the sensor main body 3 side.

Further, in the above-described embodiment, the two electrodes, the counter electrode 9 and the working electrode 11 (including the enzyme immobilization layer), were used for measuring the component concentration, but as in the modification shown in FIG. The reference electrode 22 may be provided near the working electrode 11 of the working electrode substrate 8. Reference numeral 22A in FIG. 7 denotes a reference electrode connector connected to the reference electrode 22 formed on the peripheral surface of the working electrode substrate 8. In this modified example, the reference electrode 22 is added as described above, and a reference electrode contact plate that contacts the reference electrode connector 22A is formed on the main body cover 4 side to form a circuit configuration in which the reference electrode 22 is added. Good.
Other configurations are the same as those in the above embodiment. In addition,
As shown in FIG. 8, an enzyme non-retaining working electrode 23 may be added to the configuration of the modification shown in FIG. In this way, with the configuration including the enzyme non-retaining working electrode 23,
It becomes possible to perform a more accurate measurement in consideration of the influence of the disturbing current of uric acid. Further, by making the working electrode 11 platinum or carbon containing rhodium, the disturbing current due to ascorbic acid or the like can be suppressed.

[0032]

As is apparent from the above description, according to the present invention, the amount of blood used for measurement can be reduced and the measurement operation can be simplified. Moreover, according to the present invention, it is possible to realize a biosensor that enables reliable component concentration measurement.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view showing a state in which a sensor unit is locked in an embodiment of a biosensor of the present invention.

FIG. 2 is a cross-sectional explanatory view showing a state where the sensor unit is unlocked in the embodiment of the biosensor of the present invention.

FIG. 3 is an exploded perspective view of a sensor unit according to the present embodiment.

FIG. 4 is a sectional view of a sensor unit according to the present embodiment.

FIG. 5 is a cross-sectional perspective view of the main body cover according to the present embodiment.

FIG. 6 is an equivalent circuit diagram of the present embodiment.

FIG. 7 is an exploded perspective view showing a modified example of the present invention.

FIG. 8 is an exploded perspective view showing a modified example of the present invention.

[Explanation of symbols]

 1 biosensor 2 sensor unit 3 sensor main body 4 main body cover 5 needle 9 counter electrode 9A counter electrode connector 10A blood introduction space 11 working electrode 11A working electrode connector 12 enzyme immobilization layer 13 unit fixing piston 13A compression coil spring 14 switch mechanism 17A Contact plate for counter electrode 17B Contact plate for working electrode

Claims (5)

[Claims] 1. A sampling needle having a test liquid introducing passage, a test liquid introducing space communicating with the test liquid introducing passage, and a counter electrode and a working electrode provided on opposite surfaces of the test liquid introducing space. And a sensor unit having: 2. A sensor main body in which a unit insertion space for inserting the sensor unit and a spring for urging the sensor unit are arranged, and the sensor unit is provided with the spring from an opening of the unit insertion space to a predetermined position. Locking means for locking the sensor unit in a state of being inserted against a force, and when the locking state of the locking means attached to the opening side of the unit insertion space of the sensor unit is released. The biosensor according to claim 1, further comprising: a main body cover that allows only the sampling needle of the sensor unit to project outward. 3. A connector member is arranged on the inner wall of the main body cover or the sensor main body so as to individually contact the counter electrode and the working electrode of the sensor unit with the sampling needle of the sensor unit protruding. The biosensor according to claim 2, wherein: 4. The enzyme-immobilized layer containing an enzyme that causes an enzyme reaction with a substrate in a test solution, or an enzyme immobilization layer containing the enzyme and a mediator is formed on the working electrode. Item 4. The biosensor according to any one of Item 3. 5. The unit fixing piston for detachably mounting the sensor unit is fixed to the other end of the spring, and one end of the spring is fixed to the sensor body side. The biosensor according to any one of claims 1 to 4.