JP2021085852A - Electrode for enzyme sensor and enzyme sensor - Google Patents

Abstract

To provide an electrode for an enzyme sensor excellent in sensitivity and further excellent in resistance against corrosion and cost, and to provide an enzyme sensor.SOLUTION: Disclosed is an electrode which includes: a conductive layer arranged on a substrate; and an oxidoreductase. The conductive layer includes: a conductive carbon material (A); and a binder (B). A carbon material (A) includes: at least graphite (A-a); and a conductive carbon material (A-b) other than graphite. The 60° gloss on the surface of the conductive layer is 0.5-120.SELECTED DRAWING: None

Description

The present invention relates to electrodes for enzyme sensors and enzyme sensors.

Enzyme sensors that easily measure specific components contained in biological samples such as blood and sweat and foods have been put into practical use. For example, a blood glucose level sensor that detects or quantifies glucose in blood by an electrochemical means can be mentioned. This is to selectively oxidize glucose contained in blood by the substrate specificity of the enzyme, and the electric charge reaches the electrode through the mediator or directly to generate an electric current, and the glucose concentration is quantified from the electric current value. Can be done.
As the electrode portion of the enzyme sensor that has been put into practical use, one in which a metal layer is formed by sputtering, plating, or the like may be used (for example, Patent Document 1). However, the measurement sensitivity is still not sufficient, and it is preferable not to use an expensive metal from the viewpoint of corrosion and cost.

Japanese Unexamined Patent Publication No. 2008-045877

An object of the present invention is to provide an electrode for an enzyme sensor and an enzyme sensor, which are excellent in sensitivity, resistance to corrosion, and cost.

The present inventors have reached the present invention as a result of repeated studies to solve the above problems.
That is, the present invention is an electrode containing a conductive layer arranged on a substrate and an oxidation-reducing enzyme, wherein the conductive layer contains a conductive carbon material (A) and a binder (B). An enzyme in which the carbon material (A) contains at least graphite (Aa) and a conductive carbon material (Ab) other than graphite, and the surface of the conductive layer has a 60 ° gloss of 0.5 to 120. Regarding electrodes for sensors.

The present invention also relates to the enzyme sensor electrode having a specific surface area of 5 to 800 m ^{2 / g of the conductive layer.}

The present invention also relates to the above-mentioned electrode for an enzyme sensor in which the binder (B) is a water-soluble resin (B-a) and / or water-dispersed resin fine particles (B-b).

Further, in the present invention, the content of the carbon material (A) in the total solid content of the conductive layer of 100% by mass is 50 to 90% by mass, and the content of the graphite (Aa) contained in the carbon material (A) is 50 to 90% by mass. The present invention relates to the above-mentioned electrode for an enzyme sensor having a content ((A) / (A) × 100) of 25 to 95% by mass.

The present invention also relates to an enzyme sensor formed by using the above-mentioned electrode for an enzyme sensor.

According to the present invention, it is possible to provide an electrode for an enzyme sensor and an enzyme sensor which are excellent in sensitivity, resistance to corrosion and cost.

<Electrodes for enzyme sensors>
The electrode for an enzyme sensor of the present invention comprises at least a conductive layer arranged on a substrate and an oxidoreductase. For example, a conductive composition containing a conductive carbon material (A), a binder (B), and a solvent, if necessary, on the surface of at least one side of a base material such as paper or PET (polyethylene terephthalate) film. Is applied, and if necessary, a press treatment or the like is performed to form a conductive layer, and then an oxidoreductase is supported to obtain an electrode.

<Conductive layer>
(Conductive carbon material (A))
In the present invention, the conductive carbon material (A) is used as the conductive material from the viewpoint of disposableness, biocompatibility and the like. As the conductive carbon material (A), since a conductive layer having excellent conductivity can be obtained, it contains graphite (Aa) and a conductive carbon material (Ab) other than graphite.
Examples of graphite (Aa) include artificial graphite and natural graphite, and examples of carbon materials (Ab) other than graphite include carbon black and conductive carbon fibers (carbon nanotubes, carbon nanofibers, carbon fibers). , Graphene, fullerene and the like. These can be used alone or in combination of two or more.

The content of graphite (A-a) contained in the conductive carbon material (A) contained in the conductive layer ((A-a) / (A) x 100) is preferably 25 to 95% by mass. It is more preferably 50 to 90% by mass, and even more preferably 60 to 80% by mass.

As the graphite (Aa), for example, artificial graphite, natural graphite, or the like can be used. Artificial graphite is made by artificially orienting irregularly arranged micrographite crystals by heat treatment of amorphous carbon, and is generally manufactured using petroleum coke or coal-based pitch coke as the main raw material. To. As the natural graphite, spherical graphite, scaly graphite, lump graphite, earth graphite and the like can be used. It is also possible to use expanded graphite (also referred to as expansive graphite) obtained by chemically treating scaly graphite, or expanded graphite obtained by heat-treating expanded graphite to expand it and then refining it or pressing it. You can. Among these graphites, when used for the conductive layer of the conductive base material, natural graphite is preferable from the viewpoint of conductivity, and flaky graphite such as spherical graphite, scaly graphite expanded graphite, and flaky graphite is preferable. ..

The average particle size of the graphite (Aa) used is preferably 0.5 to 500 μm, and particularly preferably 2 to 100 μm.

The average particle size referred to in the present invention is a particle size (D50) that becomes 50% when the volume ratio of the particles is integrated from the fine particle size distribution in the volume particle size distribution, and is generally used. It is measured with a standard particle size distribution meter, for example, a dynamic light scattering type particle size distribution meter (“Microtrack UPA” manufactured by Nikkiso Co., Ltd.).

As commercially available graphite, for example, as flaky graphite, CMX, UP-5, UP-10, UP-20, UP-35N, CSSP, CSPE, CSP, CP, CB-150, CB manufactured by Nippon Graphite Industry Co., Ltd. -100, ACP, ACP-1000, ACB-50, ACB-100, ACB-150, SP-10, SP-20, J-SP, SP-270, HOP, GR-60, LEP, F # 1, F # 2, F # 3, CX-3000, FBF, BF, CBR, SSC-3000, SSC-600, SSC-3, SSC, CX-600, CPF-8, CPF-3, CPB- manufactured by Chuetsu Graphite Co., Ltd. 6S, CPB, 96E, 96L, 96L-3, 90L-3, CPC, S-87, K-3, CF-80, CF-48, CF-32, CP-150, CP-100, CP, HF- 80, HF-48, HF-32, SC-120, SC-80, SC-60, SC-32, EC1500, EC1000, EC500, EC300, EC100, EC50 manufactured by Ito Graphite Industry Co., Ltd. 10099M manufactured by Nishimura Graphite Co., Ltd. , PB-99 and the like. Examples of spherical natural graphite include CGC-20, CGC-50, CGB-20, and CGB-50 manufactured by Nippon Graphite Industry Co., Ltd. Examples of earth-like graphite include blue P, AP, AOP, P # 1 manufactured by Nippon Graphite Industry Co., Ltd., and APR, S-3, AP-6, 300F manufactured by Chuetsu Graphite Co., Ltd. As artificial graphite, PAG-60, PAG-80, PAG-120, PAG-5, HAG-10W, HAG-150 manufactured by Nippon Graphite Industry Co., Ltd., RA-3000, RA-15, RA- of Chuetsu Graphite Co., Ltd. 44, GX-600, G-6S, G-3, G-150, G-100, G-48, G-30, G-50, SGP-100, SGP-50, SGP-25 manufactured by SEC Carbon Co., Ltd. , SGP-15, SGP-5, SGP-1, SGO-100, SGO-50, SGO-25, SGO-15, SGO-5, SGO-1, SGX-100, SGX-50, SGX-25, SGX -15, SGX-5, SGX-1 can be mentioned.

The conductive carbon material (Ab) other than graphite is not particularly limited, but it is preferable to use carbon black or conductive carbon fiber from the viewpoint of cost and conductivity.

Carbon black includes furnace black, which is produced by continuously pyrolyzing a gas or liquid raw material in a reactor, especially acetylene black, which is made from ethylene heavy oil, and the raw material gas is burned to burn the flame to the bottom of the channel steel. Various types such as channel black that has been rapidly cooled and precipitated, thermal black that is obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, and acetylene black that uses acetylene gas as a raw material, alone or 2 More than one type can be used together. In addition, normally oxidized carbon black, hollow carbon, and the like can also be used.
Oxidation treatment of carbon is performed by treating carbon at a high temperature in air or secondary treatment with nitrate, nitrogen dioxide, ozone, etc., for example, phenol group, quinone group, carboxyl group, carbonyl group, etc. It is a process of directly introducing (covalently bonding) an oxygen-containing polar functional group to the carbon surface, and is generally performed to improve the dispersibility of carbon.

As the specific surface area of the carbon black used increases, the contact points between the carbon black particles increase, which is advantageous in reducing the internal resistance of the electrode. Specifically, the specific surface area (BET) obtained from the amount of nitrogen adsorbed is preferably 20 m ² / g or more, more preferably 50 m ² / g or more, and even more preferably 100 m ² / g or more. Is desirable. If carbon black having a specific surface area of ^{less than 20 m 2} / g is used, it may be difficult to obtain sufficient conductivity.
The particle size of the carbon black used is preferably 0.005 to 1 μm in terms of primary particle size, and particularly preferably 0.01 to 0.2 μm. However, the primary particle size referred to here is an average of the particle sizes measured by an electron microscope or the like.

Commercially available carbon blacks include, for example, Tokai Carbon's Toka Black # 4300, # 4400, # 4500, # 5500, Degussa's Printex L, Colombian's Raven 7000, 5750, 5250, 5000 ULTRAIII, 5000 ULTRA, etc. Conductex SC ULTRA, Conductex 975 ULTRA, PUERBLACK100, 115, 205, Mitsubishi Chemicals # 2350, # 2400B, # 2600B, # 3050B, # 3030B, # 3230B, # 3350B, # 3400B, # 5400B, Cabot MONARCH1400, 1300, 900, VulcanXC-72R, BlackPearls2000, Ensaco250G, Ensaco260G, Ensaco350G, SuperP-Li, etc. , Etc., Denka Black manufactured by Denka Co., Ltd., Denka Black HS-100, FX-35 and other acetylene blacks, but the present invention is not limited to these, and two or more types may be used in combination. ..

As the conductive carbon fiber, those obtained by firing from a raw material derived from petroleum are preferable, but those obtained by firing from a raw material derived from a plant can also be used. Further, the carbon nanotubes include a single-walled carbon nanotube in which a graphene sheet forms a tube having a diameter in a nanometer region, and a multi-walled carbon nanotube in which the graphene sheet is a multi-walled layer. Therefore, the diameter of the multi-walled carbon nanotube shows a large value of 30 nm with respect to 0.7-2.0 nm of a typical single-walled carbon nanotube.

Commercially available conductive carbon fibers and carbon nanotubes include vapor-phase carbon fibers such as VGCF manufactured by Showa Denko Co., Ltd., EC1.0, EC1.5, EC2.0, EC1.5-P manufactured by Meijo Nanocarbon Co., Ltd., etc. Examples thereof include single-walled carbon nanotubes manufactured by CNano, FloTube9100, FloTube9100, FloTube9110, FloTube9200, NC7000 manufactured by Nanocyl, and 100T manufactured by Knano.

(Binder (B))
The type of the binder (B) is such that it can impart the dispersibility of the conductive carbon material (A), the adhesion to the base material, the flexibility of the conductive base material, and the stability of the conductive composition. The present invention is not particularly limited, and examples thereof include resins.

Examples of the binder (B) include polyurethane resin, polyamide resin, acrylonitrile resin, acrylic resin, butadiene resin, polyvinyl resin, polyvinyl butyral resin, polyolefin resin, polyester resin, polystyrene resin, and EVA resin. It can contain one or more kinds selected from the group consisting of resins, polyvinylidene fluoride-based resins, polytetrafluoroethylene-based resins, silicone-based resins, polyether-based resins, cellulose-based resins such as carboxymethyl cellulose, and the like. However, it is not limited to these resins. The binder resin may be used alone or in combination of two or more.

As the binder resin, a curable resin that undergoes a curing (crosslinking) reaction after the binder resin is applied to the base material can also be used.
As the binder resin, a soluble resin or dispersed resin fine particles that are soluble in an aqueous or non-aqueous solvent can also be used. Dispersed resin fine particles are those in which the resin fine particles are not dissolved in an aqueous or non-aqueous dispersion medium and exist in the state of fine particles, and the dispersion is also generally called an emulsion. These may be used alone or in combination of two or more.

The particle structure of the dispersed resin fine particles may be a multilayer structure, so-called core-shell particles. For example, by localizing a resin obtained by mainly polymerizing a monomer having a can response period in the core portion or the shell portion, or by providing a difference in Tg and composition between the core and the shell, the curability and drying can be achieved. It is possible to improve the property, film forming property, and mechanical strength of the binder.
The average particle size of the resin fine particles is preferably 10 to 1000 nm, preferably 10 to 300 nm, from the viewpoint of binding properties and particle stability. The average particle size in the present invention represents the volume average particle size and can be measured by a dynamic light scattering method.
The average particle size can be measured by the dynamic light scattering method as follows. Dilute 200 to 1000 times with the same dispersion as the dispersion medium, depending on the solid content of the resin fine particles. Approximately 5 ml of the diluted dispersion is injected into a cell of a measuring device (name black truck manufactured by Nikkiso Co., Ltd.), the refractive index conditions of the dispersion medium and the resin corresponding to the sample are input, and then the measurement is performed. It can be measured by the peak of the volume particle size distribution data (histogram) obtained at this time.
In addition, enzymes such as glucose oxidase (GOx) often carry those dispersed in an aqueous solution, and fuels such as glucose are often dissolved in an aqueous solvent. From the viewpoint of the above, the binder (B) is a water-soluble resin (BA) that is soluble in an aqueous solvent or an aqueous dispersion resin fine particle (B-) that exists in the state of fine particles without being dissolved in an aqueous dispersion medium. b) is preferably used.

Examples of the water-soluble resin include polyvinyl-based resins, polyurethane-based resins, polyester-based resins, polyether-based resins, cellulose-based resins such as carboxymethyl cellulose, formalin condensates, silicone-based resins, and composite resins thereof. Can be mentioned. Further, these two or more types may be used in combination.

Examples of the water-dispersed resin fine particles include (meth) acrylic emulsion, nitrile emulsion, urethane emulsion, polyolefin emulsion, fluorine emulsion (polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc.), and styrene-butadiene. Examples include system resins.
In addition, (meth) acrylic means methacrylic or acrylic.

From the viewpoints of slurry stability and coatability of the conductive composition, water resistance and flexibility of the conductive layer, etc., the water-soluble resin (BA) and the water-dispersed resin fine particles (B-b) can be used in combination. More preferred.

(Solvent (dispersion medium))
When the conductive carbon material (A) and the binder (B) are uniformly mixed, a solvent can be appropriately used. The solvent is not particularly limited as long as it can dissolve the resin or stably disperse the resin fine particle emulsion, and examples thereof include water and an organic solvent.

Organic solvents include alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol methyl ether and diethylene glycol methyl ether, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and the like. Suitable for the composition of the conductive composition from among ethers, hydrocarbons such as hexane, heptane and octane, aromatics such as benzene, toluene, xylene and cumene, and esters such as ethyl acetate and butyl acetate. Can be used.
Further, as the solvent, water and an organic solvent or two or more kinds of organic solvents may be used.

Further, the conductive composition used in the present invention contains, if necessary, an ultraviolet absorber, an ultraviolet stabilizer, a radical catching agent, a filler, a thixotropy-imparting agent, and an antistatic agent as long as the effects of the present invention are not impaired. , Antioxidant, Antistatic, Flame Retardant, Thermal Conductivity Improver, Plasticizer, Anti-Dripping Agent, Antifouling Agent, Preservative, Bactericide, Defoamer, Leveling Agent, Anti-blocking Agent, Hardener, Increase Various additives such as thickeners, pigment dispersants, and silane coupling agents may be added.

(Conductive composition)
The conductive composition contains a conductive carbon material (A), a binder (B), and a solvent (dispersion medium) as necessary, and is made into a slurry (paint or ink) using a disperser or a mixer. It was done.

The viscosity of the conductive composition depends on the coating method of the conductive composition, but is generally preferably 10 mPa · s or more and 30,000 mPa · s or less.

(Disperser / Mixer)
As an apparatus used for obtaining the conductive composition, a disperser or a mixer usually used for pigment dispersion or the like can be used.

For example, mixers such as disper, homomixer, or planetary mixer; homogenizers such as "Clearmix" manufactured by M-Technique or "Philmix" manufactured by PRIMIX; paint conditioner (manufactured by Red Devil), ball mill, sand mill. (Symmal Enterprises "Dyno Mill" etc.), Atwriter, Pearl Mill (Eirich "DCP Mill" etc.), or media type disperser such as Coball Mill; Wet Jet Mill (Genus "Genus PY", Sugino) Medialess dispersers such as Machine's "Starburst", Nanomizer's "Nanomizer"), M-Technique's "Claire SS-5", or Nara Machinery's "MICROS"; or other roll mills, etc. However, it is not limited to these.

For example, when using a media-type disperser, a method in which the agitator and vessel use a disperser made of ceramic or resin, or a disperser in which the surface of the metal agitator and vessel is treated with tungsten carbide spraying or resin coating. Is preferably used. As the medium, it is preferable to use glass beads, zirconia beads, or ceramic beads such as alumina beads. Only one type of dispersion device may be used, or a plurality of types of devices may be used in combination.

(Formation of conductive layer)
A conductive layer can be formed by applying a conductive composition to the above-mentioned base material and, if necessary, performing a press treatment or the like.
The method for coating the conductive composition on the base material is not particularly limited, and a known method can be used.

Specific examples include a die coating method, a dip coating method, a roll coating method, a doctor coating method, a knife coating method, a spray coating method, a gravure coating method, a screen printing method, an electrostatic coating method, and the like, and drying. As the method, a neglected drying, a blower dryer, a warm air dryer, an infrared heater, a far infrared heater and the like can be used, but the method is not particularly limited thereto.

Further, after coating, a rolling process such as a planographic press or a calendar roll may be performed, or may be performed while heating in order to soften the conductive layer and facilitate pressing. The thickness of the conductive layer is generally 0.1 μm or more and 1 mm or less, preferably 1 μm or more and 200 μm or less.

(Composition of conductive layer)
The proportion of the conductive carbon material (A) contained in the conductive layer used in the present invention is preferably 50 to 90% by mass with respect to the total solid content of the conductive layer in view of conductivity, adhesion to a base material, and the like. , 60-80% by mass is more preferable. The component other than the conductive carbon material (A) is mainly a binder (B), but any component other than that may be contained. From the viewpoint of conductivity and adhesion, the total ratio of the conductive carbon material (A) and the binder (B) to the total solid content in the conductive layer is preferably 5 to 50% by mass, more preferably 5 to 50% by mass. It is 10 to 40% by mass.

(Gloss of conductive layer)
The gloss of the conductive layer used in the present invention is 0.5 to 120, preferably 1 to 80, and more preferably 1.5 to 60. There is a correlation between the orientation state of the carbon material in the conductive layer and the gloss, and in the above range of gloss, it is possible to obtain a conductive layer in which the orientation of the carbon material is high and reproducibility and excellent conductivity are ensured. The gloss value of the surface of the conductive layer can be obtained by measuring the surface of the conductive layer that is not in contact with the base material.

(Specific surface area of conductive layer)
The specific surface area of the conductive layer used in the present invention is preferably 5 to 800 m ² / g, more preferably 10 to 500 m ² / g, and further preferably 20 to 300 m ² / g.
If the specific surface area of the conductive layer is small, the area involved in the electrode reaction may be insufficient, and the electrochemical properties and the like may not be sufficiently exhibited. On the other hand, if the specific surface area is too large, the adhesion to the base material is lowered, so that the conductive layer may be detached and the conductivity may be lowered.

<Oxidoreductase>
The enzyme in the present invention is not particularly limited as long as it is an enzyme capable of transferring electrons by reaction, and is appropriately selected depending on the detection target.
For example, oxidases such as sugars and organic acids and dehydrogenases can be used. Among them, glucose oxidase and glucose dehydrogenase, which can detect glucose contained in a biological sample such as human blood or urine, may be preferable. In addition, fructose oxidase or fructose dehydrogenase capable of detecting fructose, or lactate oxidase or lactate dehydrogenase capable of detecting lactic acid may be preferable.
The enzyme used may be one type or two or more types. Further, it may be a combination of a catalyst such as an enzyme that makes the sensing target in a state where it can be oxidized or reduced by hydrolysis or the like, and an enzyme that promotes oxidation or reduction.

<Mediator>
Enzymes include direct electron transfer type (DET type) enzymes that can directly transfer electrons to electrodes and enzymes that cannot directly transfer electrons. In the case of a non-DET type enzyme, it is necessary to use a mediator that plays a role of transferring electrons generated by the oxidation of fuel from the enzyme to the electrode. The mediator is not particularly limited as long as it is a redox substance capable of transmitting electrons to the electrode, and conventionally known mediators can be used. As a method of using the mediator, there are a method of supporting it in or on an electrode, a method of dissolving it in an electrolytic solution, and the like. Examples of the mediator include non-metal compounds such as tetrathiafluvalene, hydroquinone and quinones such as 1,4-naphthoquinone, ferrocene, ferricianides, osmium complexes, and polymers modified with these compounds.

<Ion conductor>
As the ion conductor in the present invention, a conductor that conducts ions between electrodes may be used. The form of the ionic conductor is not particularly limited as long as it has ionic conductivity. As the ionic conductor, a liquid-soluble electrolyte, a solid polymer electrolyte, or the like may be used.

<Base material>
The properties of the base material are not particularly limited, and may be a natural material or a synthetic material. Examples of natural materials include paper, non-woven fabric, and cloth. Examples of the synthetic material include resin substrates such as PET (polyethylene terephthalate), PEN (polyethylene naphthalate), polyimide, polyvinyl chloride, polyamide, nylon, OPP (stretched polypropylene), and CPP (unstretched polypropylene). Further, a conductive base material such as carbon paper or carbon cloth can be mentioned as an example. The thickness of the base material is not particularly limited and can be selected according to the shape of the enzyme sensor and the like.

<Enzyme sensor / Electrode for enzyme sensor>
The enzyme sensor is composed of at least the working electrode and the counter electrode, or the working electrode, the counter electrode and the reference electrode. Further, if necessary, a spacer, a cover, or the like for introducing a sample such as blood into the electrode may be provided.
A plurality of electrodes used for an enzyme sensor may be produced by forming conductive layers on different base materials, or when forming a conductive layer for each electrode on the same base material, or on the same base material. An electrode may be produced by forming a non-conductive portion after installing the conductive layer on the surface. Further, the electrode may be produced by forming a metal layer on the base material by metal sputtering or the like in advance and then forming a conductive layer of each electrode. When the reference electrode is installed, it is produced by, for example, further laminating silver, silver chloride, or the like on the upper part of the conductive layer. For the lead portion of each electrode, a method of forming a metal layer by metal sputtering or the like, a method of extending the conductive layer and using it, a method of further forming a metal layer by metal sputtering or the like on the upper or lower part of the extended conductive layer, etc. It can be exemplified.
As a method of installing the oxidoreductase or the mediator, a method of incorporating the oxidoreductase or the mediator as needed in the upper part of these electrodes or the upper part and / or the inside of the working electrode, the oxidoreductase or as necessary Examples thereof include a method of forming a mixture layer to which a mediator is added, a method of dispersing the mixture in the composition in advance, coating and printing, and then drying and placing the mixture in the electrode. When forming a mixture layer containing an oxidoreductase or a mediator, a hydrophilic compound and / or a hydrophilic resin may be mixed.

As described above, the enzyme sensor selectively oxidizes or reduces a specific component contained in a biological sample such as blood or food, depending on the substrate specificity of the enzyme, and qualitatively or quantifies it from the current value or the like. Applications of enzyme sensors include, for example, organic matter sensors for various organic substances, biological sensors for organic substances and body fluids in biological samples such as blood, sweat, urine, stool, tears, saliva, and exhaled breath, and water. Moisture sensor, food sensor for fruits and sugar in food, IoT sensor, environmental sensor for organic matter in the environment such as air, rivers and soil, animals and plants for animals, insects and plants Examples include sensors. Examples of biological sensors include a blood glucose level sensor that senses sugar in blood, a urine sugar level sensor that senses sugar in urine, a fatigue sensor and heat stroke sensor that senses lactic acid level in sweat, and sweat and urine. Examples include a sweating sensor and a urine sensor that sense the moisture inside. Further, as an application as a wearable sensor for a living body, for example, a urination sensor or a urine sugar level sensor in which a sensor is installed in a diaper, a percutaneous sticking type sweating sensor, a heat stroke sensor and the like can be mentioned.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the following Examples do not limit the scope of rights of the present invention at all.

<Preparation of conductive composition>
(Production Example 1: Preparation of Conductive Composition (1))
5 parts by mass of a water-soluble resin (B-1: CMC Daicel # 1240 (manufactured by Daicel Chemical Industries, Ltd.)) was added to 500 parts by mass of ion-exchanged water with stirring to dissolve it. After that, 72 parts by mass of graphite (A-1: spheroidized graphite CGB-50 (manufactured by Nippon Graphite Co., Ltd.)) and 8 parts by mass of carbon material other than graphite (A-4: Lionite EC-200L (manufactured by Lion Co., Ltd.)) were added. Added. Then, dispersion was performed with a sand mill.
Next, 30 parts by mass of water-dispersible resin fine particles (B-4: acrylic resin water dispersion W-168 (solid content 50% by mass manufactured by Toyochem Co., Ltd.)) was added and mixed, and the conductive composition (1) shown in Table 1 was added and mixed. ) Was obtained.

The conductive compositions (2) to (7) and (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9) to (9), respectively 11) was obtained.

(Production Example 2: Preparation of Conductive Composition (8))
5 parts by mass of a water-soluble resin (B-1CMC Daicel # 1240 (manufactured by Daicel Chemical Industries, Ltd.)) was added to 500 parts by mass of ion-exchanged water with stirring to dissolve it. After that, 64 parts by mass of graphite (A-1: spheroidized graphite CGB-50 (manufactured by Nippon Graphite Co., Ltd.)) and 16 parts by mass of carbon material other than graphite (A-4: Lionite EC-200L (manufactured by Lion Co., Ltd.)) were added. Added. Next, the dispersion method was changed from Production Example 1 and dispersion was performed with a disperser.
Next, 30 parts by mass of water-dispersible resin fine particles (B-4: acrylic resin water dispersion W-168 (solid content 50% by mass manufactured by Toyochem Co., Ltd.)) was added and mixed, and the conductive composition (8) shown in Table 1 was added and mixed. ) Was obtained.

The material used in the production example of the conductive composition and the method of dispersing the conductive carbon material (A) are shown below.
(Conductive carbon material (A))
Graphite (A-a)
-A-1: Spheroidized graphite CGB-50 (manufactured by Nippon Graphite Co., Ltd.)
-A-2: Scaled graphite CB-150 (manufactured by Nippon Graphite Co., Ltd.)
-A-3: Thinned graphite UP-20 (manufactured by Nippon Graphite Co., Ltd.)
Carbon material other than graphite (Ab)
・ A-4: Lionite EC-200L (manufactured by Lion Specialty Chemicals)
・ A-5: Ketjen Black EC-300J (manufactured by Lion Specialty Chemicals)
(Binder (B))
Water-soluble resin (BA)
-B-1: CMC Daicel # 1240 (manufactured by Daicel Chemical Industries, Ltd.)
・ B-2: Kuraray Poval PVA235 (manufactured by Kuraray)
Water-insoluble resin B-3: KF polymer # 9100 (manufactured by Kureha Corporation)
Water-dispersed resin fine particles (Bb)
B-4: Acrylic resin aqueous dispersion W-168 (solid content 50% by mass manufactured by Toyochem Co., Ltd.)
Dispersion method of conductive carbon material (A) ・ D-1: Sand mill ・ D-2: Disper

<Manufacturing electrodes for enzyme sensors>
[Example 1]
(Preparation of electrode (1) for enzyme sensor)

-Preparation of conductive layer The conductive composition (1) was applied to a PET base material (Lumirror (manufactured by Toray Industries, Inc.)) having a thickness of 100 μm as a non-conductive base material using a doctor blade, and then heat-dried. A conductive layer (1) was obtained.

-Preparation of Electrode for Enzyme Sensor After cutting out the conductive layer (1) to 10 × 30 mm, masking treatment was performed on the lower portion other than 5 × 5 mm with tape. A methanol solution of ferrocene, which is a mediator, and an aqueous solution of glucose oxidase, which is an oxidoreductase, are added dropwise and air-dried to a 5 x 5 mm conductive layer that has not been masked to support the mediator and enzyme. (1) was obtained.

[Example 2, Examples 4 to 5, Examples 7 to 9, Example 11, Comparative Examples 1 to 3]
(Preparation of electrodes (2), (4) to (5), (7) to (9), (11) to (14) for enzyme sensors)

-Preparation of conductive layer Conductive layers (2), (4) to (5), (7) by the same method as the method for producing a conductive layer of Example 1 except that the composition was changed to the conductive composition shown in Table 2. )-(9) and (11)-(14) were obtained.

-Making the electrode for the enzyme sensor Using the conductive layer prepared above, the electrode for the enzyme sensor (2) was obtained by the same method as the method for manufacturing the electrode for the enzyme sensor in Example 1 except that the conductive layer was changed to the conductive layer shown in Table 2. ), (4) to (5), (7) to (9), and (11) to (14) were obtained.

[Example 3]
(Creation of electrode (3) for enzyme sensor)

-Preparation of conductive layer The conductive composition (2) is applied to a PET base material (Lumirror (manufactured by Toray Industries, Inc.)) having a thickness of 100 μm as a non-conductive base material using a doctor blade, and then heat-dried. It was. Then, a roll press was performed to obtain a conductive layer (3).

-Preparation of Electrode for Enzyme Sensor After cutting out the conductive layer (3) to 10 × 30 mm, masking treatment was performed on the lower portion other than 5 × 5 mm with tape. A methanol solution of ferrocene, which is a mediator, and an aqueous solution of glucose oxidase, which is an oxidoreductase, are added dropwise and air-dried to a 5 x 5 mm conductive layer that has not been masked to support the mediator and enzyme. (3) was obtained.

[Examples 6 and 10]
(Preparation of electrodes (6) and (10) for enzyme sensors)

-Preparation of conductive layer Conductive layers (6) and (10) were obtained by the same method as the method for producing a conductive layer in Example 3 except that the composition was changed to the conductive composition shown in Table 2.

-Making the electrode for the enzyme sensor Using the conductive layer prepared above, the electrode for the enzyme sensor (6) was obtained by the same method as the method for manufacturing the electrode for the enzyme sensor in Example 3 except that the conductive layer was changed to the conductive layer shown in Table 2. ), (10) were obtained.

[Evaluation of conductive layers and electrodes for enzyme sensors]
The conductive layer and the electrode for the enzyme sensor were evaluated as follows. The obtained evaluation results are shown in Table 2.

(Specific surface area of conductive layer)
The specific surface area of the conductive layer was evaluated by measuring the amount of nitrogen adsorbed (BELSORP-mini manufactured by Nippon Bell Co., Ltd.). Specifically, the powder obtained by peeling off the conductive layer produced on the non-conductive substrate was placed in a measuring container and heat-treated at 150 ° C. to remove adsorbed water. Then, the amount of nitrogen adsorbed was measured under liquid nitrogen (77K) with a nitrogen adsorption measuring device, and the specific surface area was calculated by BET plot. The evaluation results are shown in Table 2.

(Gloss of conductive layer)
The gloss of the conductive layer was evaluated by micro-TRI-Gloss (manufactured by BYK Adaptives & Instruments). Specifically, micro-TRI-Gloss was brought into contact with the surface of the conductive layer prepared on the non-conductive base material, and 60 ° gloss was measured at three places, and the average value was taken as the gloss value. The evaluation results are shown in Table 2.

<Electrochemical evaluation>
(Linear sweep voltammetry (LSV) measurement)
The electrode for the enzyme sensor prepared above is the working electrode, the counter electrode is the platinum coil electrode, the reference electrode is the Ag / AgCl electrode, and 0.1 M phosphate buffer (pH 7.0) is added as the electrolytic solution, and the reaction substrate (sensing object). ), D-glucose was added so as to be 20 mM, and LSV measurement was performed in the range of −0.2 V (vsAg / AgCl) to +0.5 V (vsAg / AgCl). From the current curve obtained by the LSV measurement, the maximum value (mA / cm2) of the current density was evaluated using the following criteria as an index. The evaluation results are shown in Table 2. It can be said that the larger the maximum value of the current density of the electrode for the enzyme sensor, the higher the sensitivity because it is easier to detect the substance to be sensed.

〇: "The percentage of the maximum value of the current density of Comparative Example 1 is 140% or more of the maximum value of the example or the comparative example."
Δ: “The percentage of the maximum value of the current density of Comparative Example 1 to the maximum value of the same maximum value of Example or Comparative Example is 105% or more and less than 140%”.
X; "The percentage of the maximum value of the current density of Comparative Example 1 to the maximum value of the example or the comparative example is less than 105%"

As shown in Table 2, it was confirmed that in the conductive layer of the present invention, the current value that can be detected by the electrode for the enzyme sensor is greatly improved by improving the orientation state of the carbon material and optimizing the specific surface area. .. It is considered that the optimization of the specific surface area of the conductive layer improved the carrying efficiency of the oxidoreductase and effectively oxidized the object to be sensed. It is also considered that by controlling the orientation state (gloss value) of the carbon material in the conductive layer, the electrons taken out by the oxidation of the sensing target move smoothly. Therefore, the electrode for the enzyme sensor and the enzyme sensor of the present invention using a carbon material having excellent resistance to corrosion and cost can obtain good sensitivity.
On the other hand, in Comparative Example 1, the orientation state of the carbon material is not insufficient, and in Comparative Example 3, graphite (Aa) is not contained and the conductivity is not insufficient, so that the electrons taken out by the oxidation of the sensing target are taken out. Does not occur smoothly, and it is assumed that the electrochemical characteristics have deteriorated. Further, in Comparative Example 1, it is assumed that the electrochemical properties are deteriorated because the support of the oxidoreductase is insufficient.

Claims (5)

An electrode containing a conductive layer and an oxidoreductase, which is arranged on a base material.
The conductive layer contains a conductive carbon material (A) and a binder (B), and the carbon material (A) contains graphite (Aa) and a conductive carbon material (Ab) other than graphite. ,
The surface of the conductive layer has a 60 ° gloss of 0.5 to 120.
Electrode for enzyme sensor. The electrode for an enzyme sensor according to claim 1, wherein the specific surface area of the conductive layer is 5 to 800 m ^{2 / g.} The electrode for an enzyme sensor according to claim 1 or 2, wherein the binder (B) contains a water-soluble resin (B-a) and / or water-dispersed resin fine particles (B-b). The content of the carbon material (A) in the total solid content of the conductive layer of 100% by mass is 50 to 90% by mass, and the content of graphite (Aa) contained in the carbon material (A) is ((A). The electrode for an enzyme sensor according to any one of claims 1 to 3, wherein −a) / (A) × 100) is 25 to 95% by mass. An enzyme sensor formed by using the electrode for an enzyme sensor according to any one of claims 1 to 4.