JP2014041166A - Biosensor system, sensor chip and density measurement method of an analysis target in a blood sample - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biosensor system capable of preventing occurrence of measurement error caused from the temperature in application circumstances.SOLUTION: A biosensor system 100 includes a measurement device 101 having a calculation section 306 and a sensor chip 200 which is detachably attached to the measurement device 101 and on which a blood sample is introduced. The sensor chip 200 includes: a measurement section 41 (measurement section A which acquires a data a relevant to the density of an analysis target based on the amount of the current flowing in the blood sample based on a reaction related with oxidoreductase having a substrate of the analysis target in the blood sample; and a measurement section 42 (measurement section B) that acquires a data b for correcting the temperature of the data a from the blood sample. The calculation section 306 has a function to determine the density of the analysis target in the blood sample, which is corrected according to the temperature of the blood sample based on the data a and the data b.

Description

  The present invention relates to a biosensor system, a sensor chip, and a method for measuring an analyte concentration in a blood sample.

  A portable biosensor system comprising a measuring instrument having a calculation unit and a sensor chip detachably attached to the measuring instrument in order to measure the concentration of an analyte in a blood sample, for example, blood glucose concentration (blood glucose level) Is used.

  The concentration of the analyte is calculated based on the amount of oxidant or reductant generated by the enzyme cycling reaction via the oxidoreductase using the analyte as a substrate. The rate of the enzyme cycling reaction depends on the temperature at which the reaction proceeds (reaction temperature). For this reason, it is desirable to correct the concentration of the analyte based on the reaction temperature.

  The reaction temperature is measured by, for example, a temperature sensor arranged in a measuring instrument (Patent Document 1). However, in the biosensor system of Patent Document 1, since the internal temperature of the measuring device is measured, the measured reaction temperature does not accurately reflect the temperature of the blood sample. This may cause errors in the analyte concentration measurement.

  Patent Documents 2 to 4 disclose biosensor systems aimed at improving reaction temperature measurement accuracy. The biosensor systems of Patent Documents 2 and 3 have a heat conducting member in the vicinity of the blood sample holding part of the sensor chip, and the temperature of the blood sample transmitted through the heat conducting member is arranged in a measuring instrument. Detected by a temperature sensor. In the biosensor systems of Patent Documents 2 and 3, since the resin plate is disposed between the heat conducting member and the blood sample holding unit, the heat conducting member does not contact the blood sample. In the biosensor system of Patent Document 4, a temperature sensor and a heat conduction member are arranged in a mounting portion of a measuring instrument for attaching a sensor chip, and the temperature of the blood sample is transmitted to the temperature sensor via the heat conduction member. .

JP 2003-156469 A JP 2001-235444 A JP 2003-42995 A International Publication No. 2003/062812 Pamphlet

  When a user who carries a biosensor system moves in a place with a large temperature difference (for example, moving from outdoor to indoor in winter or summer), the measuring instrument cannot keep up with the sudden change in the environmental temperature and for a while. The temperature becomes higher or lower than the destination environment. For example, when the measuring device is moved from an environment of 40 ° C. or 10 ° C. to an environment of 25 ° C., it takes about 30 minutes for the temperature of the measuring device to converge to 25 ° C. (Patent Document 1). In measuring the reaction temperature with the temperature sensor of the measuring device, it is not easy to completely eliminate the influence of the temperature of the measuring device. For this reason, in the biosensor systems described in Patent Documents 2 to 4, too, if the temperature of the environment in which the sensor is used changes rapidly, an error is likely to occur in the measurement of the analyte concentration. In the biosensor systems described in Patent Documents 2 to 4, since the temperature of the blood sample is transferred to the temperature sensor via the resin plate and the heat conducting member, the measured reaction temperature is still the blood sample temperature. Does not accurately reflect temperature.

  An object of this invention is to provide the biosensor system which can suppress generation | occurrence | production of the measurement error resulting from the temperature of a use environment, and the sensor chip suitable for the said sensor system. Another object of the present invention is to provide a measurement method capable of improving the measurement accuracy of the analyte concentration in the blood sample.

  The present invention is a biosensor system comprising a measuring instrument having a calculation unit and a sensor chip that is detachably attached to the measuring instrument and into which a blood sample is introduced, wherein the sensor chip is included in the blood sample. A measurement unit A that acquires data a related to the concentration of the analyte based on the amount of current flowing in the blood sample due to a reaction involving an oxidoreductase having an analyte as a substrate, and temperature correction of the data a And a measurement unit B that acquires data b to be obtained from the blood sample, and the calculation unit is corrected according to the temperature of the blood sample based on the data a and the data b. A biosensor system having the function of determining the concentration of the analyte therein is provided.

  In another aspect, the present invention is a sensor chip used in the above biosensor system into which a blood sample is introduced, and a reaction involving an oxidoreductase having an analyte in the blood sample as a substrate. Measurement unit A that acquires data a related to the concentration of the analyte based on the amount of current flowing in the blood sample, and measurement that acquires data b for temperature correction of the data a from the blood sample A sensor chip having a portion B is provided.

  In another aspect, the present invention provides data related to the concentration of the analyte based on the amount of current flowing in the blood sample due to a reaction involving an oxidoreductase having the analyte in the blood sample as a substrate. a step for obtaining a, a step for obtaining data b for correcting the temperature of the data a from the blood sample, and a correction based on the temperature of the blood sample based on the data a and the data b. Determining the concentration of the analyte in the blood sample, wherein the step of obtaining the data b includes a pair of contacts with the blood sample. A concentration of the analyte in the blood sample, comprising the step of applying a voltage to the electrode and measuring the amount of current flowing in the blood sample as the redox material other than the analyte is oxidized or reduced To provide a measurement method.

  By acquiring data for temperature correction of analyte concentration directly from the blood sample, in the measurement of the analyte concentration in the blood sample, measurement errors due to the temperature of the environment in which the measurement is performed are more reliably generated. Can be avoided. Therefore, according to the present invention, the measurement accuracy of the analyte concentration in the blood sample is increased.

It is a figure which shows an example of the biosensor system by this invention. It is a disassembled perspective view of an example of the sensor chip by this invention. It is a top view of an example of the sensor chip by the present invention. It is a figure which shows an example of the circuit structure in the biosensor system by this invention. It is a figure which shows an example of a conversion table. It is a figure which shows another example of a conversion table.

  The biosensor system according to the present invention acquires data for correcting the temperature of an analyte concentration from a blood sample by a measurement unit arranged on a sensor chip.

  FIG. 1 is a diagram for explaining an example of a biosensor system according to the present invention. The biosensor system 100 includes a rectangular parallelepiped measuring device 101 and a sensor chip 200. A mounting port 102 that is a rectangular hole is formed on the side wall surface of the measuring instrument 101. The sensor chip 200 is detachably attached to the attachment opening 102 and connected to the measuring instrument 101. A display unit 103 for displaying a measurement result is disposed at a substantially central portion of one main surface of the measuring instrument 101.

FIG. 2 is an exploded perspective view of the sensor chip 200, and FIG. 3 is a plan view thereof. The sensor chip 200 has a cover 203 on the insulating substrate 201 with a spacer 202 having a rectangular cutout 204 formed therein and leaving one end of the insulating substrate 201 (the right end in the figure). Has been placed.

  The members 201, 202, and 203 are integrated by, for example, adhesion or heat welding. The notch portion 204 of the spacer 202 becomes the capillary portion 40 that holds the blood sample after the integration of the members. The capillary portion 40 extends along the long side of the chip 200 and communicates with the outside at one end portion (left end portion in the drawing) of the spacer 202. In other words, the capillary section 40 communicates with the blood sample introduction port 16 that opens to the outside of the chip 200. The cover 203 has an exhaust port 15 at a portion corresponding to the end of the capillary portion 40 opposite to the end communicating with the outside. Thereby, a blood sample can be easily sucked into the capillary portion 40 from the sample introduction port 16 by capillary action.

  On the insulating substrate 201, the electrodes 11, 12, 13, 14 are arranged so that each part (parts 31, 32, 33, 34) faces the capillary part 40. The portion 31 of the electrode 11 is disposed at a position closer to the blood sample introduction port 16 than the portion 32 of the electrode 12 and the portion 33 of the electrode 13. The part 33 of the electrode 13 is a part of the electrode 13 branched in a U-shape, and is disposed at a position sandwiching the part 32 of the electrode 12. The reaction reagent layer 20 is formed on the insulating substrate 201 so as to cover the portion 32 of the electrode 12 and the portion 33 of the electrode 13. The reaction reagent layer 20 contains an oxidoreductase having an analyte in a blood sample as a substrate. The reaction reagent layer 20 is formed at a position away from the portion 31 of the electrode 11.

  The sensor chip 200 is constituted by an electrode system constituted by the part 32 of the electrode 12 and the part 33 of the electrode 13 and a partial space of the capillary part 40 that accommodates the reaction reagent layer 20 and the parts 32 and 33. And a measurement unit 41 (measurement unit A). Furthermore, the sensor chip 200 includes a measurement unit configured by an electrode system constituted by the part 31 of the electrode 11 and the part 32 of the electrode 12 and a partial space of the capillary part 40 that accommodates the part 31 and the part 32. 42 (measurement part B).

  As will be described later, the measurement unit A acquires data a related to the concentration of the analyte in the blood sample based on the amount of current flowing in the blood sample due to the reaction involving the oxidoreductase. Then, as will be described later, the measurement unit B uses the data b for correcting the temperature of the data a, more specifically, a reaction that does not involve the oxidoreductase used to acquire the data a and is not an analyte. Data b relating to the amount of current flowing in the blood sample accompanying the oxidation or reduction of the redox material is obtained from the blood sample. Thus, the measurement part B may be in the state which acquires the data b using the member which contacts a blood sample, more specifically, the electrode which contacts a blood sample. Here, the data related to the amount of current means the amount of the current or a converted value of the current amount. The redox substance other than the analyte is at least one selected from ascorbic acid, uric acid, acetaminophen, ferricyanide, p-benzoquinone, p-benzoquinone derivative, oxidized phenazine methosulfate, methylene blue, ferricinium, and ferricinium derivative. Can be illustrated. The redox substance other than the analyte may be a solvent, for example water in the case of a blood sample.

  In the measurement unit A, the electrode 12 functions as a working electrode and the electrode 13 functions as a counter electrode. In the measurement part B, the electrode 12 functions as a counter electrode, and the electrode 11 functions as a working electrode. The measurement part A and the measurement part B may be in a state where the electrode 12 is shared as shown in the figure, or may be in a state where each has a pair of electrodes. Thus, in the sensor chip 200, the measurement unit B has an electrode for applying a voltage to the blood sample.

The portion 34 of the electrode 14 is disposed in the vicinity of the end on the back side of the capillary section 40, in other words, in the vicinity of the end opposite to the end communicating with the outside. By applying a voltage between the electrode 14 and the electrode 11, it can be easily detected that the blood sample has been introduced into the capillary part 40. Note that a voltage may be applied between the electrode 12 or the electrode 13 and the electrode 14 instead of the electrode 11.

  The electrodes 11, 12, 13, and 14 are connected to leads (not shown), respectively. One end of the lead is exposed to the outside of the chip 200 at the end of the insulating substrate 201 not covered with the spacer 202 and the cover 203 so that a voltage can be applied between the electrodes.

  Analytes in the blood sample include substances other than blood cells, such as glucose, albumin, lactic acid, bilirubin and cholesterol. As the oxidoreductase, one using the target analyte as a substrate is used. Examples of the oxidoreductase include glucose oxidase, glucose dehydrogenase, lactate oxidase, lactate dehydrogenase, bilirubin oxidase and cholesterol oxidase. Examples of the amount of oxidoreductase in the reaction reagent layer include a range of 0.01 to 100 units (U), preferably 0.05 to 10 U, and more preferably 0.1 to 5 U.

  The reaction reagent layer 20 includes an electronic mediator having a function of transferring electrons generated by the enzyme reaction to the electrode, such as potassium ferricyanide, p-benzoquinone, p-benzoquinone derivative, oxidized phenazine methosulfate, methylene blue, ferricinium, and ferricinium derivative. It is desirable to contain. The reaction reagent layer 20 may contain a water-soluble polymer compound in order to improve the moldability of the reaction reagent layer. Examples of water-soluble polymer compounds include carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, carboxyethyl cellulose, polyvinyl alcohol, polyvinyl pyrrolidone and polyzine, polystyrene sulfonic acid, gelatin and derivatives thereof, poly Examples thereof include at least one selected from acrylic acid and salts thereof, polymethacrylic acid and salts thereof, starch and derivatives thereof, maleic anhydride polymer and salts thereof, agarose gel and derivatives thereof.

  As materials for the insulating substrate 201, the spacer 202, and the cover 203, resins such as polyethylene terephthalate, polycarbonate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyoxymethylene, monomer cast nylon, polybutylene terephthalate, methacrylic resin, and ABS resin are used. Furthermore, glass can be illustrated.

  The electrodes 11, 12, 13, and 14 can be made of a known conductive material such as palladium, platinum, gold, silver, titanium, copper, nickel, and carbon.

  FIG. 4 is a diagram illustrating an example of a circuit configuration for measuring an analyte concentration in a blood sample in the biosensor system 100. The measuring instrument 101 includes a control circuit 300 that applies a voltage between at least two of the electrodes 11, 12, 13, and 14 in the sensor chip 200, and a liquid crystal display (LCD) 400 that corresponds to a display unit of the measuring instrument. have.

  The control circuit 300 includes four connectors 301a, 301b, 301c, and 301d, a switching circuit 302, a current / voltage conversion circuit 303, an analog / digital (A / D) conversion circuit 304, a reference voltage source 305, an arithmetic operation Part 306. The control circuit 300 can switch the potential applied to the electrode through the switching circuit 302 so that one electrode can be used as a positive electrode or a negative electrode.

The calculation unit 306 includes a known central processing unit (CPU) and a conversion table for determining the analyte concentration in the blood sample based on the data a and data b. In the conventional biosensor system, the analyte concentration is corrected by referring to a conversion table in which a correction coefficient based on the environmental temperature is described. More specifically, in the conventional biosensor system, the analyte concentration is provisionally calculated with reference to the conversion table for temporary measurement, and then the analyte concentration is corrected with reference to the conversion table for temperature correction. It was. When the temperature of the blood sample fluctuates, the present inventor determines the amount of current flowing in the blood sample due to a reaction involving oxidoreductase, and a reaction not involving the oxidoreductase and a redox substance other than the analyte. It has been found that the amount of current flowing in a blood sample can vary as well as the oxidation or reduction of. And, as will be described later, the blood sample in the measurement of the analyte concentration without measuring the temperature of the blood sample or the like based on the conversion table constructed using this relationship by appropriately designing the biosensor system The influence of temperature can be eliminated.

  The calculation unit 306 is in a state of storing one conversion table constructed in this way, and is not in a state of storing a plurality of conversion tables constructed for each temperature of a blood sample or the like. FIG. 5 is a diagram illustrating an example of a conversion table included in the calculation unit 306, and FIG. 6 is a diagram illustrating another example thereof. As shown in FIG. 5, the conversion table of the calculation unit 306 has the same voltage application condition as that for acquiring the data a from the reference blood sample in which the analyte concentration is clear and the temperature is fixed to one value. The data c related to the amount of current flowing through the reference blood sample and the amount of current flowing through the reference blood sample obtained from the reference blood sample under the same voltage application conditions as the acquisition of data b above. Three types of data consisting of related data d and data c and the analyte concentration in the reference blood sample corresponding to data d may be described. As described above, the data related to the amount of current means the amount of the current or a converted value of the current amount. As shown in FIG. 6, instead of data c and data d, one conversion value based on data c and data d may be described in the conversion table included in calculation unit 306. More specifically, the conversion table includes data obtained by dividing data d by data c instead of data c and data d, and analyte concentration 2 corresponding to data c and data d. Types of data may be described. As described above, the conversion table of the calculation unit 306 is not in a state in which the relationship between the blood sample temperature or the environmental temperature and the analyte concentration is described. It is desirable to prepare a conversion table for each biosensor system. As will be described later, the temperature of the reference blood sample is preferably in the range of more than 10 ° C. and less than 40 ° C., more preferably in the range of 17 ° C. or more and 33 ° C. or less.

  The measurement of the analyte concentration in the blood sample using the biosensor system 100 is performed as follows, for example.

  First, in response to a command from the CPU of the calculation unit 306, the electrode 13 is connected to the current / voltage conversion circuit 303 via the connector 301c, and the electrode 14 is connected to the reference voltage source 305 via the connector 301b. Thereafter, a constant voltage is applied between both electrodes in accordance with a command from the CPU. The voltage is, for example, a voltage of 0.01 to 2 V, preferably 0.1 to 1 V, more preferably 0.2 to 0.5 V when the electrode 14 is represented as a positive electrode and the electrode 13 is represented as a negative electrode. is there. This voltage is applied after the sensor chip is inserted into the measurement unit until the blood sample is introduced to the back of the capillary unit 40. When a blood sample is introduced into the capillary section 40 from the blood sample introduction port of the sensor chip 200, a current flows between the electrode 14 and the electrode 13. By identifying the amount of increase in current per unit time at that time, it is detected that the capillary part is filled with the blood sample. The current value is converted into a voltage value by the current / voltage conversion circuit 303, then converted into a digital value by the A / D conversion circuit 304, and input to the CPU. The CPU detects that the blood sample has been introduced to the back of the capillary section based on the digital value.

  After the introduction of the blood sample, for example, the analyte in the blood sample is reacted with the oxidoreductase in the range of 0 to 60 seconds, preferably 0 to 30 seconds, more preferably 0 to 15 seconds.

  Subsequently, the data a is acquired as follows. First, in response to a command from the CPU, the switching circuit 302 is activated, the electrode 12 is connected to the current / voltage conversion circuit 303 via the connector 301a, and the electrode 13 is connected to the reference voltage source 305 via the connector 301c. Thereafter, a measurement sequence in the measurement unit A is input according to a command from the CPU. In this case, the voltage is, for example, 0.05 to 1 V, preferably 0.1 to 0.8 V, more preferably 0.2 to 0.6 V when the electrode 12 is represented as a positive electrode and the electrode 13 is represented as a negative electrode. It is a voltage that becomes a magnitude. The voltage application time is in the range of 0.1 to 30 seconds, preferably 0.1 to 15 seconds, more preferably 0.1 to 5 seconds. The amount of current flowing between the electrodes due to the application of the voltage is converted into a voltage value by the current / voltage conversion circuit 303 when a signal instructing acquisition of the data a is given from the control circuit to the measurement unit A. After that, it is converted into a digital value by the A / D conversion circuit 304 and input to the CPU, and stored as data a in the memory of the arithmetic unit 306. From the viewpoint of speeding up the measurement of the analyte concentration, the control circuit acquires the data a within a range of 0.5 seconds to less than 2.5 seconds from the time when the blood sample is introduced into the capillary part of the sensor chip. It is preferable to give a signal instructing to the measurement unit A.

  Thereafter, the data b is acquired as follows. First, in response to a command from the CPU, the switching circuit 303 is activated, the electrode 11 is connected to the current / voltage conversion circuit 303 via the connector 301d, and the electrode 12 is connected to the reference voltage source 305 via the connector 301a. Subsequently, a constant voltage is applied between both electrodes in the measurement unit B according to a command from the CPU. The voltage is, for example, a voltage of 0.1 to 5 V, preferably 0.2 to 3 V, more preferably 0.5 to 2.5 V when the electrode 11 is represented as a positive electrode and the electrode 12 is represented as a negative electrode. is there. The voltage application time is in the range of 0.1 to 30 seconds, preferably 0.1 to 10 seconds, and more preferably 0.1 to 5 seconds. The amount of current flowing between the electrodes due to the application of the voltage is converted into a voltage value by the current / voltage conversion circuit 303 when a signal instructing acquisition of the data b is given from the control circuit to the measurement unit B. After that, it is converted into a digital value by the A / D conversion circuit 304 and input to the CPU, and stored as data b in the memory of the arithmetic unit 306. Note that the data b may be acquired before the data a. In this case, the reduction type mediator is generated on the counter electrode when the data b is acquired. It is not preferable to use the working electrode as the counter electrode, and it is preferable to use the counter electrode when acquiring data a. In addition, an independent electrode different from the electrode used for data a acquisition may be provided as a counter electrode. At that time, it is preferable that an oxidized mediator is disposed on the counter electrode. From such a viewpoint, when one electrode is used as the working electrode and the counter electrode when acquiring the data a and the data b, the redox reaction on the surface of the electrode may be a rate-determining step. From the viewpoint of avoidance, the data b is preferably acquired after the data a. Further, by acquiring the data b in such an order, the current that flows in the blood sample with the oxidation or reduction of the redox substance other than the analyte is a reaction that does not involve the oxidoreductase used to acquire the data a. Can be detected more reliably.

  Subsequently, the computing unit 306 refers to the conversion table and determines the analyte concentration in the blood sample based on the data a and the data b. Then, the determined analyte concentration is displayed on the LCD 400 as an image. The calculation program for the determination may be appropriately designed according to the data structure of the conversion table. When numerical data that completely matches data a and data b is not described in the conversion table, the analyte is obtained by using a known linear interpolation method from data described in the conversion table and approximating data a and data b. What is necessary is just to determine a density | concentration.

According to the biosensor system of the present invention, the value of the data b is obtained from the blood sample X having a temperature of 17 ° C. and the blood sample Y having the same component as the blood sample X and having a temperature of 33 ° C. To the extent that the numerical value (Z) obtained by dividing by the value of a becomes substantially constant, the influence of the temperature of the blood sample in the measurement of the analyte concentration can be eliminated. More specifically, when the numerical values obtained from blood sample X and blood sample Y are respectively indicated as Z _X and Z _Y , the numerical value indicated by Z _X / Z _Y may be in the vicinity of 1.0. When measuring the glucose concentration in blood, the analyte concentration in blood sample X and blood sample Y may be in the range of greater than 0 mg / dl and less than or equal to 1000 mg / dl, for example, between 10 mg / dl and 600 mg / dl. If it is in the range.

  In order to eliminate the influence of the temperature of the blood sample in the measurement of the analyte concentration to the above extent, it is necessary to design the biosensor system appropriately. More specifically, various parameters such as the composition of the reaction reagent layer, the timing for measuring the amount of current flowing in the blood sample due to the reaction involving the oxidoreductase, and the dimensions of the capillary part are controlled.

  For example, when the reaction reagent layer does not contain a water-soluble polymer compound or the amount of the water-soluble polymer compound in the reaction reagent layer is less than 0.2% by mass, It is preferable to have a control circuit that gives the measurement unit A a signal instructing acquisition of the data a within a range of 0.5 seconds or more and less than 2.5 seconds from the time of introduction. Further, for example, when the amount of the water-soluble polymer compound in the reaction reagent layer is 0.2% by mass or more, the measuring instrument is not less than 2.5 seconds after the blood sample is introduced into the sensor chip. It is preferable to have a control circuit that gives the measurement unit A a signal instructing acquisition of the data a. The reason for this is not clear at this time, but the present inventor thinks as follows. When the reaction reagent layer contains 0.2% by mass or more of the water-soluble polymer compound, the dissolution rate of the reagent that contributes to the reaction in the reaction reagent layer elutes into the blood sample is slow, and the diffusion rate is also slow and the reaction is smoothly performed. It takes 2.5 seconds or more to progress. As shown in the examples described later, when the width of the capillary is in the range of 0.8 mm or less, it is desirable to adopt the design. In addition, when the amount of the water-soluble polymer compound in the reaction reagent layer is 0.2% by mass or more, the upper limit of the content of the water-soluble polymer compound can be exemplified by 2% by mass, and an instruction to obtain data a As an upper limit of the time for, 15 seconds can be exemplified.

  In addition, for example, when the amount of enzyme in the reaction reagent layer is 1.8 U or more and the width of the capillary part is in a range exceeding 0.8 mm, as shown in the examples described later, the measuring instrument is a sensor chip, It is preferable to have a control circuit that gives the measurement unit A a signal for instructing the acquisition of the data a within a range of 0.5 seconds or more, further 1.5 seconds or more, particularly 2.0 seconds or more from the time when it was introduced into the measurement section A. . As an upper limit of the time for the instruction, 15 seconds can be exemplified.

  Further, for example, as shown in the examples described later, the capillary portion has a low height when the enzyme amount in the reaction reagent layer is the same, more specifically, 0.3 mm or less, and further 0.15 mm. Is preferably within a range of less than 0.1 mm, particularly 0.1 mm or less. The reason for this is not clear at this time, but the present inventor thinks as follows. If the height of the capillary part is too high, the oxidoreductase eluted from the reaction reagent layer tends to diffuse away from the electrode surface, and the enzyme involved in the enzyme cycling reaction is insufficient in the vicinity of the electrode surface. An example of the lower limit of the height of the capillary portion is 0.05 mm.

  The biosensor system according to the present invention can measure the analyte concentration with high accuracy even when the temperature of the environment in which the sensor is used changes rapidly. For this reason, it is not necessary to arrange | position the environmental temperature measurement part represented by the thermistor in a measuring device. However, this is not intended to exclude the installation of the environmental temperature measurement unit in the biosensor system according to the present invention.

That is, in the biosensor system according to the present invention, the measuring device may further include an environmental temperature measurement unit that measures the temperature of the environment (measurement environment) in which the biosensor system is used. In the biosensor system according to the present invention, in addition to the conversion table (first conversion table), the calculation unit corrects the data c and the data c according to the temperature of the measurement environment (data You may further have the 2nd conversion table in which e) was described. If the temperature of the measurement environment is too high or too low, the analyte concentration measurement accuracy using the first conversion table may decrease. In such a case, the analyte concentration may be corrected by using the second conversion table instead of the first conversion table. Examples of the temperature of the measurement environment in which substitution of the second conversion table is preferable include a range of 10 ° C. or lower and a range of 40 ° C. or higher. An example of the lower limit of the temperature is 0 ° C., and an example of the upper limit of the temperature is 50 ° C. If the temperature of the measurement environment is in the range of more than 10 ° C. and less than 40 ° C., it is sufficient to use the first conversion table.

  In the biosensor system according to the present invention, the first conversion table and the second conversion table are stored in one data table, more specifically, the data c, the data d, and the data e are mutually connected. It is not excluded that they are associated and described in one data table. For example, when the temperature of the measurement environment is in the range of 10 ° C. or lower and the range of 40 ° C. or higher, such a data table shows the analyte concentration calculated by referring to the first conversion table. It may further have data (correction coefficient) to be corrected by.

In the biosensor system according to the present invention, the measuring device outputs a signal instructing to perform the first temperature measurement before acquiring the data a and data b, and the second temperature after acquiring the data a and data b. You may further have a control circuit which gives the signal which instruct | indicates implementation of an measurement to an environmental temperature measurement part. When the biosensor system according to the present invention displays the temperature measured in the first temperature measurement and the second temperature measurement as the first temperature and the second temperature, respectively,
i) When the first temperature and the second temperature satisfy the following relational expression (1), the concentration of the analyte in the blood sample is determined based on the data a and the data b by referring to the first conversion table. And then
2.5 ° C. ≦ | (second temperature) − (first temperature) | (1)
ii) When the first temperature and the second temperature satisfy the following relational expression (2), by referring to the second conversion table, data related to the first temperature and / or the second temperature instead of the data b And determining the concentration of the analyte in the blood sample based on the data a,
| (Second temperature)-(First temperature) | <2.5 ° C (2)
It can also be configured.

  From the viewpoint of more reliably detecting changes in the environmental temperature, the second temperature measurement may be performed after 5 seconds or more, preferably 15 seconds or more, and more preferably 30 seconds or more have elapsed since the first temperature measurement. As described above, the biosensor system of the present invention provides a signal for instructing the second temperature measurement after 5 seconds or more, preferably 15 seconds or more, more preferably 30 seconds or more after the first temperature measurement. You may have the control circuit given to an environmental temperature measurement part. As data related to the first temperature and / or the second temperature, for example, an average value of the first temperature and the second temperature can be used. The data may be temperature or a converted value of temperature.

  The biosensor system according to the present invention has a control circuit that measures the environmental temperature at regular intervals from the first temperature measurement and provides a signal for detecting a temperature transition per unit time to the environmental temperature measurement unit. May be. Thereby, it is possible to easily determine the reliability (the presence or absence of a failure or a sudden change in the external temperature) of the environmental temperature measurement unit represented by the thermistor.

  As described above, the method for measuring the concentration of an analyte according to the present invention applies a voltage to a pair of electrodes in contact with a blood sample, and a current flowing in the blood sample accompanying oxidation or reduction of a redox substance other than the analyte. The above data b is obtained by including the step of measuring the amount of. The concentration of the analyte in the blood sample based on data a and data b can be determined by referring to the first conversion table.

  The method for measuring an analyte concentration according to the present invention may further include a step of measuring an ambient temperature around the blood sample. The step includes a first temperature measuring step for measuring the environmental temperature before acquiring the data a and data b, and a second temperature measuring step for measuring the environmental temperature after acquiring the data a and data b. May be.

In the analyte concentration measuring method according to the present invention, when the temperatures measured in the first temperature measuring step and the second temperature measuring step are respectively expressed as the first temperature and the second temperature,
i) When the first temperature and the second temperature satisfy the following relational expression (1), the concentration of the analyte in the blood sample is determined based on the data a and the data b by referring to the first conversion table. Decide
2.5 ° C. ≦ | (second temperature) − (first temperature) | (1)
ii) When the first temperature and the second temperature satisfy the following relational expression (2), the first temperature and / or the second temperature is related to the data b instead of the data b by referring to the second conversion table. Determining the concentration of the analyte in the blood sample based on the data and data a.
| (Second temperature)-(First temperature) | <2.5 ° C (2)
You may comprise as follows. From the viewpoint of more reliably detecting changes in the environmental temperature, the second temperature measurement may be performed after 5 seconds or more, preferably 15 seconds or more, and more preferably 30 seconds or more have elapsed since the first temperature measurement. As data related to the first temperature and / or the second temperature, for example, an average value of the first temperature and the second temperature can be used. The data may be temperature or a converted value of temperature.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
The sensor chip shown in FIGS. 2 and 3 was produced. The capillary part was designed to have a width of 0.6 mm, a length (depth) of 2.5 mm, and a height of 0.1 mm. The reaction reagent layer was formed as follows. Glucose dehydrogenase, potassium ferricyanide (manufactured by Kanto Chemical Co., Inc.), taurine (manufactured by Nacalai Tesque Co., Ltd.) and maltitol (manufactured by Hayashibara Co., Ltd.) were obtained by dissolving them in an aqueous CMC solution (Serogen HE-1500F manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). The reagent solution has an enzyme amount of 2.0 U / sensor in the reaction reagent layer, a CMC amount of 0.05 mass%, a potassium ferricyanide amount of 2.5 mass%, a taurine amount of 1.5 mass%, and a maltitol amount. After applying on a polyethylene terephthalate substrate so that it might become 0.1 mass%, it was dried in the atmosphere of humidity 45% and temperature 21 degreeC. Each electrode was composed of palladium.

  Blood was collected from 3 subjects. Blood samples were prepared by adding glucose concentrate to each blood such that the glucose concentration was 50 mg / dl, 100 mg / dl, 250 mg / dl, 400 mg / dl, 600 mg / dl.

  The blood sample was introduced into the capillary part of the sensor chip. The temperature of the blood sample was 17 ° C, 25 ° C or 33 ° C. Next, a voltage of 0.25 V is applied between the working electrode (electrode 12) and the counter electrode (electrode 13) in the measurement unit A, and 1 second after the introduction of the blood sample is completed, the above enzyme and glucose The current (glucose response) flowing between the electrodes was measured by an enzyme cycling reaction involving the.

  Thereafter, a voltage of 2.5 V is applied between the working electrode (electrode 11) and the counter electrode (electrode 12) in the measurement unit B, and the current flowing between the electrodes 3 seconds after the introduction of the blood sample is completed. (Temperature correction response) was measured.

Table 1 shows the response current value of the glucose response and the response current value of the temperature correction response. Also,
Table 1 also shows a numerical value (Z) obtained by dividing the response current value of the response for temperature correction by the response current value of the glucose response. A numerical value (Z _x / Z _y ) obtained by dividing the numerical value (Z _x ) obtained from the blood sample at a temperature of 17 ° C. by the numerical value (Z _y ) obtained from the blood sample at a temperature of 33 ° C. Table 1 shows. Further, Table 2 shows the dimensions of the capillary section, the measurement timing of each response, the amount of enzyme, the amount of CMC, and the maximum deviation rate (maximum fluctuation width) from 1.0 of the value of Z _x / Z _y . These values for the following examples and reference examples are also shown in Table 2.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 1 was in the range of 12% or less.

(Example 2)
Various current responses were measured in the same manner as in Example 1 except that the glucose response was measured 2.5 seconds after the introduction of the blood sample into the capillary section was completed. Numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 3.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 2 was in the range of 17% or less.

(Example 3)
Various current responses were measured in the same manner as in Example 1 except that a sensor chip having an enzyme amount of 0.5 U per sensor was used. Table 5 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 3 was in the range of 12% or less.

Example 4
Various current responses were measured in the same manner as in Example 1 except that a sensor chip having an enzyme amount of 1.0 U per sensor was used. Table 5 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 4 was in the range of 17% or less.

(Example 5)
Various current responses were measured in the same manner as in Example 3 except that the glucose response was measured 2.5 seconds after the introduction of the blood sample into the capillary part was completed. Numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 6.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 5 was in a range exceeding 17%.

(Example 6)
Various current responses were measured in the same manner as in Example 4 except that the glucose response was measured 2.5 seconds after the introduction of the blood sample into the capillary section was completed. The numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 7.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 6 was in a range exceeding 17%.

(Example 7)
Various current responses were measured in the same manner as in Example 4 except that a sensor chip whose reaction reagent layer did not contain CMC was used. The numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 8.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 7 was in the range of 12% or less.

(Example 8)
Various current responses were measured in the same manner as in Example 4 except that a sensor chip having a CMC amount of 0.1% by mass in the reaction reagent layer was used. The numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 9.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 8 was in the range of 17% or less.

Example 9
Various current responses were measured in the same manner as in Example 6 except that a sensor chip having a CMC amount of 0.25% by mass in the reaction reagent layer was used. Numerical values obtained from each blood sample (Z, Z _x /
Z _y ) is shown in Table 10.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 9 was in the range of 12% or less.

(Example 10)
Various current responses were measured in the same manner as in Example 6 except that a sensor chip having a CMC amount of 0.5 mass% in the reaction reagent layer was used. Table 11 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 10 was in the range of 17% or less.

(Example 11)
Various current responses were measured in the same manner as in Example 7 except that the glucose response was measured 2.5 seconds after the introduction of the blood sample into the capillary section was completed. The numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 12.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 11 was in a range exceeding 17%.

(Example 12)
Various current responses were measured in the same manner as in Example 8 except that the glucose response was measured 2.5 seconds after the introduction of the blood sample into the capillary section was completed. The numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 13.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 12 was in a range exceeding 17%.

(Example 13)
Various current responses were measured in the same manner as in Example 9 except that the glucose response was measured 1.5 seconds after the introduction of the blood sample into the capillary section was completed. Table 14 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 13 was in a range exceeding 17%.

(Example 14)
Various current responses were measured in the same manner as in Example 10 except that the glucose response was measured 1.0 seconds after the introduction of the blood sample into the capillary part was completed. The numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 15.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 14 was in a range exceeding 17%.

(Example 15)
Various current responses were measured in the same manner as in Example 4 except that a sensor chip having a capillary part width of 1.0 mm and a length of 3.0 mm was used. The numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 16.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 15 was in the range of 17% or less.

(Example 16)
Various current responses were measured in the same manner as in Example 15 except that the glucose response was measured 1.5 seconds after the introduction of the blood sample into the capillary section was completed. Table 17 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 16 was in the range of 12% or less.

(Example 17)
Various current responses were measured in the same manner as in Example 2 except that a sensor chip having a capillary part width of 1.0 mm and a length of 3.0 mm was used. Table 18 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 17 was in the range of 12% or less.

(Example 18)
Various current responses were measured in the same manner as in Example 1 except that a sensor chip having a capillary part width of 1.0 mm and a length of 3.0 mm was used. Table 19 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 18 was in the range of 17% or less.

(Example 19)
Various current responses were measured in the same manner as in Example 18 except that the glucose response was measured 1.5 seconds after the introduction of the blood sample into the capillary part was completed. The numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 20.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 19 was in the range of 17% or less.

(Example 20)
Various current responses were measured in the same manner as in Example 3 except that a sensor chip having a capillary part width of 1.0 mm and a length of 3.0 mm was used. Table 21 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 20 was in the range of 17% or less.

(Example 21)
Various current responses were measured in the same manner as in Example 5 except that a sensor chip having a capillary part width of 1.0 mm and a length of 3.0 mm was used. The numerical values (Z, Z _x / Z _y ) obtained from each blood sample are shown in Table 22.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 21 was in a range exceeding 17%.

(Example 22)
Various current responses were measured in the same manner as in Example 6 except that a sensor chip having a capillary part width of 1.0 mm and a length of 3.0 mm was used. Table 23 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 22 was in a range exceeding 17%.

(Example 23)
Various current responses were measured in the same manner as in Example 6 except that a sensor chip having a capillary part height of 0.15 mm was used. Table 24 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 23 was in a range exceeding 17%.

(Example 24)
Various current responses were measured in the same manner as in Example 4 except that a sensor chip having a capillary part height of 0.15 mm was used. Table 25 shows the numerical values (Z, Z _x / Z _y ) obtained from each blood sample.

As shown in Table 2, the maximum fluctuation width of the value of Z _x / Z _y in Example 24 was in a range exceeding 17%.

  In the measurement of the concentration of an analyte in a blood sample, the present invention is very important in various fields where high accuracy of measurement is required to suppress the occurrence of measurement errors due to the temperature of the environment in which the measurement is performed. Has utility value.

11, 12, 13, 14 Electrode 15 Exhaust port 16 Blood sample introduction port 20 Reaction reagent layer 31 Part of electrode 11 facing capillary part 32 Part of electrode 12 facing capillary part 33 Part of electrode 13 facing capillary part 34 Part of the electrode 14 facing the capillary part 40 Capillary part 41 Measuring part A
42 Measuring section B
DESCRIPTION OF SYMBOLS 100 Biosensor system 101 Measuring device 102 Mounting port 103 Display part 200 Sensor chip 201 Insulating substrate 202 Spacer 203 Cover 204 Notch part 300 Control circuit 301a, 301b, 301c, 301d Connector 302 Switching circuit 303 Current / voltage conversion circuit 304 Analog / digital (A / D) conversion circuit 305 Reference voltage source 306 Calculation unit 400 Liquid crystal display (LCD)

Claims (11)

A measuring instrument having a calculation unit;
A sensor chip that is detachable from the measuring instrument and into which a blood sample is introduced;
A biosensor system comprising:
The sensor chip is
A measuring unit A for acquiring data a related to the concentration of the analyte based on the amount of current flowing in the blood sample by a reaction involving an oxidoreductase having the analyte in the blood sample as a substrate; ,
In order to correct the temperature of the data a, the reaction does not involve the oxidoreductase, and is related to the amount of current that flows in the blood sample due to oxidation or reduction of a redox substance other than the analyte. measuring part B for obtaining b from the blood sample;
Have
The computing unit is
A reference blood sample having a clear analyte concentration and a fixed temperature is flowed in the reference blood sample by a reaction involving the oxidoreductase using the analyte in the reference blood sample as a substrate. Data c related to the amount of current, and a current that flows from the reference blood sample in the reference blood sample as a result of the oxidation or reduction of the redox substance other than the analyte, which is a reaction not involving the redox enzyme. A conversion value based on data d related to the quantity of
The concentration of the analyte in the reference blood sample corresponding to the one reduced value based on the data c and the data d;
Stores a conversion table that describes multiple data with
The computing unit is
Calculating one conversion value corresponding to the one conversion value based on the data c and the data d based on the data a and the data b;
Selecting the one converted value based on the data c and the data d that matches or approximates the one converted value based on the calculated data a and the data b;
Reading out the concentration of the analyte in the reference blood sample corresponding to the one converted value based on the selected data c and data d;
A biosensor system that determines the concentration of the analyte in the blood sample corrected according to the temperature of the blood sample based on the read concentration of the analyte in the reference blood sample. The computing unit is
(I) When the one converted value based on the data a and the data b is a value coinciding with the one converted value based on the data c and the data d, the read of the analyte Determining the concentration of the analyte in the blood sample such that the concentration is the concentration of the analyte in the blood sample;
(Ii) When the one converted value based on the data a and the data b is a value approximated to the one converted value based on the data c and the data d, the read of the analyte The biosensor system according to claim 1, wherein the concentration of the analyte in the blood sample is calculated based on the concentration. The one converted value based on the data c and the data d is calculated by dividing the value of the data d by the value of the data c,
The biosensor according to claim 1, wherein the calculation unit calculates the one converted value based on the data a and the data b by dividing the value of the data b by the value of the data a. system.   Control in which the measuring device gives a signal instructing the acquisition of the data a to the measuring unit A within a range of 0.5 seconds to less than 2.5 seconds from the time when the blood sample is introduced into the sensor chip. The biosensor system according to claim 1, further comprising a circuit. The sensor chip has a reaction reagent layer containing the oxidoreductase,
The reaction reagent layer does not contain a water-soluble polymer compound, or the amount of the water-soluble polymer compound in the reaction reagent layer is less than 0.2% by mass;
A control circuit in which the measuring device gives a signal for instructing the acquisition of the data a to the measuring unit A within a range from 0.5 second to less than 2.5 seconds from when the blood sample is introduced into the sensor chip The biosensor system according to claim 1, comprising: The sensor chip has a reaction reagent layer containing the oxidoreductase,
The amount of the water-soluble polymer compound in the reaction reagent layer is 0.2% by mass or more,
2. The control device includes a control circuit that provides the measurement unit A with a signal instructing acquisition of the data a after 2.5 seconds or more have elapsed since the blood sample was introduced into the sensor chip. The biosensor system according to any one of -3.   The biosensor system according to any one of claims 1 to 3, wherein the measuring device further includes an environmental temperature measurement unit that measures the temperature of the measurement environment. A sensor chip used in the biosensor system according to any one of claims 1 to 7,
A measurement unit A for acquiring data a related to the concentration of the analyte based on the amount of current flowing in the blood sample by a reaction involving an oxidoreductase having an analyte in the blood sample as a substrate;
In order to correct the temperature of the data a, the reaction does not involve the oxidoreductase, and is related to the amount of current that flows in the blood sample due to oxidation or reduction of a redox substance other than the analyte. measuring part B for obtaining b from the blood sample;
A sensor chip. Obtaining data a related to the concentration of the analyte based on the amount of current flowing in the blood sample by a reaction involving an oxidoreductase having an analyte in the blood sample as a substrate;
In order to correct the temperature of the data a, the reaction does not involve the oxidoreductase, and is related to the amount of current that flows in the blood sample due to oxidation or reduction of a redox substance other than the analyte. obtaining b from the blood sample;
Based on the data a and the data b, the oxidoreductase using the analyte in the reference blood sample as a substrate from a reference blood sample in which the analyte concentration is clear and the temperature is fixed to one value is obtained. Data c related to the amount of current flowing through the reference blood sample due to the reaction involved, and the oxidation or reduction of the redox substance other than the analyte, which is a reaction not involving the redox enzyme from the reference blood sample A conversion value based on data d related to the amount of current flowing in the reference blood sample is calculated,
Selecting the one converted value based on the data c and the data d that matches or approximates the one converted value based on the calculated data a and the data b;
Reading out the concentration of the analyte in the reference blood sample corresponding to the one converted value based on the selected data c and d,
Determining the concentration of the analyte in the blood sample corrected according to the temperature of the blood sample based on the read concentration of the analyte in the reference blood sample;
A method for measuring the concentration of an analyte in a blood sample. Determining the concentration of the analyte in the blood sample;
(I) When the one converted value based on the data a and the data b is a value coinciding with the one converted value based on the data c and the data d, the read of the analyte Determining the concentration of the analyte in the blood sample such that the concentration is the concentration of the analyte in the blood sample;
(Ii) When the one converted value based on the data a and the data b is a value approximated to the one converted value based on the data c and the data d, the read of the analyte The method for measuring the concentration of an analyte in a blood sample according to claim 9, wherein the concentration of the analyte in the blood sample is calculated based on the concentration. The one converted value based on the data c and the data d is calculated by dividing the value of the data d by the value of the data c,
In the step of calculating the one converted value corresponding to the one converted value based on the data c and the data d based on the data a and the data b, the value of the data b is set to the value of the data a. The method for measuring the concentration of an analyte in a blood sample according to claim 9 or 10, wherein the one converted value based on the data a and the data b is calculated by division.

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