JP2019038870A - Aqueous conductive dispersion liquid, biosensor, and method for manufacturing biosensor - Google Patents

Abstract

To provide an electrode which can more efficiently manufacture an electrode having biocompatibility, and suppresses nonspecific absorption for stably measuring concentration of a measuring object (for example, glucose) with high sensitivity for a long period of time, and to provide a biosensor using the same.SOLUTION: An aqueous conductive dispersion contains a conductive material (A), a block polymer (B) and an aqueous liquid medium (D), where the block polymer (B) has an acrylic polymer block (B1) formed of an acrylic monomer having an average value of water/1-octanol distribution coefficient (LogP) of 0 or more and 2 or less and a polyethylene oxide block (B2), and a mass of polyethylene oxide block/[mass of total of acrylic polymer block and polyethylene oxide block] contained in the block polymer (B) is 0.01 to 0.3.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an aqueous conductive dispersion, and more particularly to an aqueous conductive dispersion excellent in biocompatibility, and particularly suitable for forming electrodes used for biosensors, and a biosensor using the same.

In recent years, measurement and detection of chemical substances by sensors have been performed in various fields. Among various types of sensors, biosensors using a molecular identification function are very excellent in substance selectivity, and thus are widely applied in the medical and biochemical fields.
For example, in the field of diabetes treatment, blood glucose level measurement using a biosensor has been performed. Diabetes is a disease that has increased rapidly in recent years, and it is important to measure blood glucose levels continuously or continuously safely and simply. Conventionally used biosensors employ a method of measuring blood sugar level by sampling blood. In recent years, a method for measuring the glucose concentration in body fluids such as tears, mucus, sweat, and saliva other than blood has been proposed and reported as a flexible or wearable biosensor.

  Biosensors for measuring glucose concentration use enzyme electrodes that specifically detect various physiologically active substances using the reaction specificity of the enzyme. As such an enzyme electrode, an electrode constructed so as to be able to analyze a sample by an electrochemical method or an optical method is widely used. In an enzyme electrode for analyzing a sample by an electrochemical method, an enzyme or an electron acceptor is usually immobilized on the surface of an electrode such as a gold electrode, a platinum electrode, or a carbon electrode.

  In this enzyme electrode, glucose oxidase which is a complex protein with flavin adenine dinucleotide (hereinafter abbreviated as FAD) is used as an oxidoreductase, and ferrocene is used as an electron acceptor. A reaction system using an electron acceptor as a mediator can measure even a very small amount of glucose. In addition, an inexpensive biosensor can be manufactured by using inexpensive carbon for the electrode system on the substrate.

  When this biosensor is used for measuring the glucose concentration in blood or the like, the reaction between glucose and the enzyme is inhibited by nonspecific adsorption of proteins, blood cells, etc. on the surface of the enzyme electrode, resulting in a decrease in sensitivity. Furthermore, it is impossible to use it in a living body for a long period of time, for example, like a subcutaneous indwelling type.

  Thus, a method for suppressing nonspecific adsorption by coating or interposing a biocompatible 2-methacryloyloxyethyl phosphorylcholine (MPC) -containing polymer on the surface or inside of the enzyme electrode is disclosed (Patent Document 1, 2).

  In addition, a method for suppressing non-specific adsorption by producing an electrode using an MPC polymer to which an electron acceptor site is bonded has been disclosed (Patent Document 3).

Japanese Patent Laid-Open No. 04-283653 WO2010 / 090271 Japanese Patent Laid-Open No. 10-139832

However, even if biocompatibility is imparted to the enzyme electrode by the method disclosed in Patent Documents 1 to 3, nonspecific adsorption cannot be completely suppressed. In order to improve sensitivity and perform long-term stable measurement, a biocompatible polymer that further suppresses non-specific adsorption of proteins and the like is desired.
Moreover, since the biocompatible material and the electrode such as the carbon electrode are separately manufactured, the manufacture of the sensor is complicated. It is desired that the sensor can be manufactured more efficiently.

  The present invention can produce an electrode having biocompatibility more efficiently, and an electrode that suppresses nonspecific adsorption in order to measure the concentration of a measurement target (for example, glucose) with high sensitivity and stably for a long period of time. An object of the present invention is to provide a biosensor using this.

As a result of intensive studies to solve the above problems, the present inventors have found that a block polymer (B) incorporating a hydrophilic polyethylene oxide chain (hereinafter also referred to as PEG chain) in the main chain is a conductive material. Has been found to have a function of stabilizing the dispersion in an aqueous liquid medium, leading to the present invention.
That is, the present invention relates to the following (1) to (7).
(1) An aqueous conductive dispersion containing a conductive material (A), a block polymer (B), and an aqueous liquid medium (D),
The block polymer (B) comprises an acrylic polymer block (B1) formed from an acrylic monomer having an average value of water / 1-octanol partition coefficient (LogP) of 0 or more and 2 or less, and a polyethylene oxide block (B2). )
The mass of the polyethylene oxide block / [total mass of the acrylic polymer block and the polyethylene oxide block] included in the block polymer (B) is 0.01 to 0.3.
Aqueous conductive dispersion.

(2) The aqueous conductive dispersion according to (1), wherein the conductive material (A) is a carbon material.

(3) The block polymer (B) is bonded via any structure of the following formula (IA), (IB) or (IC), (1) or (2) The aqueous conductive dispersion described.

(4) The acrylic polymer block and polyethylene oxide block contained in the block polymer (B) are bonded to each other in the structure of the following formula (IA), (1) to (3) An aqueous conductive dispersion.

(5) The aqueous conductive dispersion according to any one of (1) to (4), further comprising water-dispersible resin particles (C).

(6) A biosensor having a base substrate and an electrode disposed on the base substrate and in direct contact with the liquid to be measured,
A biosensor in which the electrode is formed from the aqueous conductive dispersion according to any one of (1) to (5).

(7) A method for producing a biosensor having a base substrate and an electrode disposed on the base substrate and in direct contact with the liquid to be measured,
The aqueous conductive dispersion according to any one of (1) to (5) is applied to a predetermined position of the base substrate, the aqueous liquid medium (D) is removed, and the electrode is formed.
Biosensor manufacturing method.

According to the present invention, it is possible to provide an aqueous conductive dispersion excellent in dispersibility and storage stability of a conductive material, a biosensor including a biocompatible electrode using the same, and a method for manufacturing the same.
That is, by using a block polymer that is rich in hydrophilicity and biocompatible, it is possible to provide an aqueous conductive dispersion that is excellent in dispersibility and storage stability. It is now possible to produce compatible electrodes. Since this electrode contains a conductive polymer and a biocompatible vinyl polymer, the electrode itself can sufficiently suppress nonspecific adsorption of proteins without covering or interposing the electrode with a biocompatible material. As a result, it is possible to provide a biosensor that can measure the concentration of a measurement target (for example, glucose) with high sensitivity and stability over a long period of time.

FIG. 1 shows a schematic cross-sectional view of the biosensor of the present invention. FIG. 2 shows a schematic cross-sectional view of a biosensor according to another embodiment of the present invention.

  The aqueous conductive dispersion of the present invention, an electrode using the same and a biosensor will be described below with reference to preferred embodiments.

<Conductive material (A)>
The conductive material (A) is contained in order to increase the electron conductivity at the electrode. Here, conductive carbon materials and metal materials are mainly mentioned, but not limited thereto.

  The conductive carbon material used in the present invention is not particularly limited, but graphite, carbon black, conductive carbon fiber (carbon nanotube, carbon nanofiber, carbon fiber), graphene-based carbon material (graphene, graphene nano) Platelet), porous carbon, activated carbon, nanoporous carbon, fullerene and the like can be used alone or in combination of two or more.

  Carbon black is a furnace black produced by continuously pyrolyzing a gas or liquid raw material in a reactor, especially ketjen black using ethylene heavy oil as a raw material. Channel black that has been rapidly cooled and precipitated, thermal black obtained by periodically repeating combustion and thermal decomposition using gas as a raw material, and particularly various types such as acetylene black using acetylene gas as a raw material, or 2 More than one type can be used in combination. Ordinarily oxidized carbon black, hollow carbon and the like can also be used.

  The oxidation treatment of carbon black is performed by treating the carbon black at a high temperature in the air or by treating it with nitric acid, nitrogen dioxide, ozone, etc., for example, phenol group, quinone group, carboxyl group, carbonyl group. This is a treatment for directly introducing (covalently bonding) such an oxygen-containing polar functional group to the carbon surface, and is generally performed to improve the dispersibility of carbon black.

As the specific surface area of the carbon black used increases, the number of contact points between the carbon black particles increases, which is advantageous in reducing the internal resistance of the electrode. Specifically, the specific surface area (BET) determined from the adsorption amount of nitrogen is 20 m ² / g or more and 1500 m ² / g or less, preferably 50 m ² / g or more and 1500 m ² / g or less, more preferably 100 m ^2. / G or more and 1500 m ² / g or less are desirable.

  Examples of commercially available carbon black include Toka Black # 4300, # 4400, # 4500, # 5500 (Tokai Carbon Co., Furnace Black), Printex L and the like (Degussa Co., Furnace Black), Raven 7000, 5750, 5250, 5000 ULTRA III, 5000 ULTRA, etc., Conductex SC ULTRA, Conductex 975 ULTRA, etc., PUER BLACK 100, 115, 205, etc. (manufactured by Colombian, Furnace Black), # 2350, # 2400B, # 2600B, # 3050B, # 3030B, # 3030B, # 3030B # 3350B, # 3400B, # 5400B etc. (Mitsubishi Chemical Co., Furnace Black), MONARCH1400, 1300, 900, VulcanXC-7 R, BlackPearls2000, etc. (Cabot Corporation, Furnace Black), Ensaco250G, Ensaco260G, Ensaco350G, SuperP-Li (manufactured by TIMCAL), Ketjen Black EC-300J, EC-600JD (manufactured by Lion), Denka Black, Denka Black HS Examples of graphite such as -100, FX-35 (manufactured by Denki Kagaku Kogyo Co., Ltd., acetylene black) include natural graphite such as artificial graphite, flake graphite, massive graphite, and earth graphite, but are not limited thereto. They may be used in combination of two or more.

  As the conductive carbon fibers, those obtained by firing from petroleum-derived raw materials are preferable, but those obtained by firing from plant-derived raw materials can also be used. For example, VGCF manufactured by Showa Denko Co., Ltd. manufactured with petroleum-derived raw materials can be mentioned.

As a carbon material other than carbon black, the use of a graphene-based carbon material, porous carbon, and nanoporous carbon is preferable from the viewpoint of specific surface area and the like and conductivity.
The graphene-based carbon material may be a carbon material in which carbon atoms are arranged in a hexagonal shape on the same plane, and the graphene that is a monoatomic layer constituting graphite has a single layer or a multilayer structure. Single-layer and multi-layer graphene is mechanically or chemically peeled off from graphite or synthesized from a hydrocarbon gas by a CVD method, etc. Ten layers of multilayer graphene may be preferred.
Examples of commercially available graphene-based carbon materials include graphene nanoplatelets made by XGSciences such as xGnP-C-750 and xGnP-M-5.

Carbon nanotubes have a nanoscale tube-like structure in which a graphene sheet is wound, and are distinguished into a single layer and a multilayer depending on the number of stacked graphene sheets. Carbon nanotubes can control various physical properties such as specific surface area and conductivity by controlling fiber diameter, length, crystallinity, and aggregated state according to raw materials and synthesis methods. Similar to the graphene-based carbon material, in consideration of synthesis cost and handling, multi-walled carbon nanotubes may be preferable to single-walled carbon nanotubes.
Examples of commercially available carbon nanotubes include carbon nanotubes manufactured by Showa Denko KK such as VGCF, VGCF-H, and VGCF-X, and carbon nanotubes manufactured by Meijo Nanocarbon.

Porous carbon is generally obtained by mixing a template material such as magnesium acetate and a carbon raw material, firing, and then removing the template material. The physical properties of the porous carbon obtained can be controlled by controlling the type, particle size, regularity, etc. of the mold material.
Commercially available porous carbon includes: Knob MH grade, Knob P (2) 010 grade, Knob P (3) 010 grade, Knob P (4) 050, Knob MJ (4) 030 grade, Knob MJ (4) 010 grade And porous carbons manufactured by Toyo Tanso Co., Ltd., such as Knobel MJ (4) 150 grade.

Nanoporous carbon is a spherical particle having a mesoporous structure on the surface and a particle size of about 20 to 50 nm. It has excellent adsorption capacity due to its high surface area and pore volume derived from the mesoporous structure.
Examples of commercially available nanoporous carbon include nanoporous carbon manufactured by Easy-N.

  As the graphite, fine powdery natural graphite and artificial graphite can be used without particular limitation. Natural graphite includes flaky scaly graphite, massive (scaly) graphite, low-crystalline earth-like graphite excavated from natural deposits, spheroidal graphite obtained by shaping scaly graphite into a spherical shape, and scaly graphite as sulfuric acid. Examples thereof include expanded graphite chemically treated by the above, expanded graphite by heat treatment at a high temperature and expanded, and then expanded. Examples of the artificial graphite include those obtained by heat-treating mesophase pitch and powder coke at high temperature, those obtained by pulverizing graphite electrodes, and those obtained by heat-treating thermosetting resin beads and graphitized.

  Examples of commercially available graphite include flaky graphite such as J-CPB, CGB-10, and SP-10 (manufactured by Nippon Graphite), HOP (manufactured by Nippon Graphite), SRP-7 (manufactured by Ito Graphite). Scale graphite, earth-like graphite such as CP2000M, 3000M (made by Ito Graphite), expanded graphite such as 9532400A, 9950200 (made by Ito Graphite), EC1500, EC1000, EC500, EC300, EC100, EC50 (made by Ito Graphite Industries) And artificial graphite such as SGO-10 and SGP-5 (manufactured by SEC Carbon Co.).

The metal material (metal powder) used in the present invention is not particularly limited, and for example, a metal material having an electric resistivity of 20 × 10 ⁻⁶ Ω · cm or less can be used.
Specific examples of the metal material include gold (Au), silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), nickel (Ni), and the like. One species may be used alone, or two or more species may be used in combination.
Among the above metal powders, it is more preferable to use spherical silver particles and / or copper particles for the reason that an electrode having a lower volume resistivity can be formed. In addition, from a viewpoint of improving oxidation resistance, it is preferable to use copper particles whose surfaces are modified or coated with an organic compound, an inorganic compound, an inorganic oxide, a metal other than copper, or the like.
In the present invention, the metal powder may be indefinite, agglomerated, scale-like, microcrystalline, spherical, flaky, etc., without particular limitation, but has printability (particularly screen printability). It is preferable to use a metal powder having an average particle size of 0.5 to 10 μm for the reason that it is good.

  Specific examples of commercially available silver particles include AG2-1C (spherical silver powder, average particle size: 1.0 μm, manufactured by DOWA Electronics), AG4-8F (spherical silver powder, average particle size: 2.2 μm, DOWA electronics) AG3-11F (spherical silver powder, average particle size: 1.4 μm, manufactured by DOWA Electronics), AgC-102 (flaky silver powder, average particle size: 1.5 μm, manufactured by Fukuda Metal Foil Powder Co., Ltd.), AgC-103 (flaky silver powder, average particle size: 1.5 μm, manufactured by Fukuda Metal Foil Powder Industries), AgC-A (flaky silver powder, average particle size: 6.5 μm, manufactured by Fukuda Metal Foil Powder Industries), AgC-B (flaky silver powder, average particle size: 3.5 μm, manufactured by Fukuda Metal Foil Powder Industry Co.), Ag-XF301 (flaky silver powder, average particle size: 4.0 μm, manufactured by Fukuda Metal Foil Powder Industrial Co., Ltd.), SA-0201 (flaky silver powder, average particle size: 2.4 μm, manufactured by METALOR), AA-3462 (flaky silver powder, average particle size: 4.3 μm, manufactured by METALOR), and the like.

  In the aqueous conductive dispersion of the present invention, the conductive material (A) in the total mass of the dispersion is 0.1% by mass or more and 95% by mass or less, more preferably 1% by mass or more and 90% by mass or less. It is preferable to contain.

<Block polymer (B)>
The block polymer (B) used in the present invention comprises an acrylic polymer block (B1) formed from an acrylic monomer having an average value of water / 1-octanol partition coefficient (LogP) of 0 or more and 2 or less, and polyethylene oxide. By having the block (B2), the adsorptivity of proteins and the like is controlled. The acrylic polymer block (B1) and the polyethylene oxide block (B2) are bonded by a covalent bond.
The acrylic polymer block (B1) includes “acrylic polymer portion”, “acrylic polymer block (B1)”, “acrylic polymer portion (B1)”,
The polyethylene oxide block (B2) may be referred to as “polyethylene oxide portion”, “polyethylene oxide block (B2)”, and “polyethylene oxide portion (B2)”, respectively. Further, as described above, polyethylene oxide may be abbreviated as “PEG” (or “PEO”).
The acrylic polymer portion is a polymer block of an acrylic monomer, and this block portion may be either a homopolymer of an acrylic monomer or a copolymer of an acrylic monomer. In the case of a copolymer, any form of alternating copolymerization, random copolymerization, or block copolymerization may be used.
The block polymer (B) has a function of facilitating dispersion of the conductive material (A) in an aqueous liquid medium (D) to be described later and keeping the dispersion state stable.

  The block polymer (B) of the acrylic polymer block (B1) and the polyethylene oxide block (B2) is bonded via any one of the following formulas (IA), (IB) or (IC) (bonded structure). It is preferable. Although the synthesis method will be described later, it is not particularly limited. In addition, although it is preferable that the block polymer (B) includes one or more bonding structures represented by the following formulas (IA) to (IC), it may include a bonding structure other than these. A polymer formed by bonding via the structure of the following formula (IA) is more preferable.

An example of a method for synthesizing the block polymer (B) having the bond structure represented by the above formula (IA) will be given.
For example, when an acrylic polymer is synthesized using 4,4′-azobis (4-cyanovaleric acid) (for example, a commercial product “V-501” manufactured by Wako Pure Chemical Industries, Ltd.) as a radical polymerization initiator, An acrylic resin having a carboxyl group is obtained. The acrylic polymer block (B1) and the polyethylene oxide block (B2) are represented by the above formula (IA) by adding polyethylene glycol as a raw material constituting the polyethylene oxide block (B2) and performing an esterification reaction thereto. A block polymer formed by bonding can be obtained.

  Alternatively, the block polymer (B) having a bond structure represented by the above formula (IA) is a polyethylene oxide block (B) represented by the following formula (II) as a radical polymerization initiator when synthesizing an acrylic polymer. It can be preferably synthesized using B2) and a polymer azo polymerization initiator having a structural unit containing an azo group. In the formula, m and n are each independently an integer of 1 or more. The polymer azo polymerization initiator has a structure in which a polymer segment and an azo group (—N═N—) are repeatedly bonded. In this embodiment, the polymer azo polymerization initiator includes a polyethylene oxide block (B2) as a polymer segment. By using a molecular azo initiator, the block polymer (B) can be easily synthesized.

  When using a polymer azo polymerization initiator, the mass average molecular weight of the block polymer can be adjusted by appropriately changing the ratio of the total number of moles of the acrylic monomer to the number of moles of the azo group contained in the initiator. it can.

The mass average molecular weight of the polymer azo polymerization initiator is preferably about 5,000 to 100,000, and more preferably about 10,000 to 50,000. The molecular weight of the polyethylene oxide block (B2) as the initiator is preferably about 800 to 10,000, and more preferably about 1,000 to 8,000.
Moreover, preferably m is 15-200, More preferably, m is 20-100, Preferably n is 3-50, More preferably, n is 4-30.

Since the polymer azo polymerization initiator has a polyethylene oxide block (B2), it is soluble in water, alcohol, and organic solvent, and a block polymer is synthesized by solution polymerization, emulsion polymerization, or dispersion polymerization. Is possible. In addition, since it has a polymerization initiation part (radical generation part: -N = N-) in the molecular chain skeleton, it is not necessary to use a separate polymerization initiator, and more radically compared to the terminal reactive macromonomer. It has the feature of having high reactivity and stability.
The polymer azo polymerization initiator is: C (CH ₃ ) CN— (CH ₂ ) ₂ —COO— (CH ₂ CH ₂ O) _m —CO— (CH ₂ ) ₂ —C (CH ₃ ) CN A radical as shown below is generated, and an acrylic monomer described later is polymerized. And the main chain which the acrylic polymer block (B1) formed from an acrylic monomer and the said part derived from a radical couple | bonded is formed, and a block polymer is formed. The polyethylene oxide block (B2) is derived from a part of the radical.
Specific examples of the polymer azo polymerization initiator include a polymer azo initiator VPE0201 manufactured by Wako Pure Chemical Industries, Ltd. (the molecular weight of the (CH ₂ CH ₂ O) _m portion of the above formula (II) is about 2000, and n is about 6) And the like.

  In addition to the polymer azo polymerization initiator, an azo initiator such as 2,2'-azobisisobutyronitrile and an organic peroxide initiator such as benzoyl peroxide can be used in combination. By using these initiators in combination, the initiation efficiency can be increased, PEG can be efficiently incorporated into the acrylic polymer block (B1), and the residual monomer can be reduced.

When synthesizing the block polymer (B), the molecular weight and terminal structure are controlled by using a chain transfer agent such as mercaptans such as lauryl mercaptan and n-dodecyl mercaptan, α-methylstyrene dimer, limonene, etc. May be.

Next, a method for synthesizing the block polymer (B) in which the acrylic polymer block (B1) and the polyethylene oxide block (B2) are bonded via the structure of the above formula (IB) will be described.
For example, the block polymer (B) in which the acrylic polymer block (B1) and the polyethylene oxide block (B2) are bonded through the structure of the above formula (IB) has an acrylic monomer having a hydroxy group. A step of polymerizing using an azo polymerization initiator to obtain an acrylic polymer block having a hydroxy group at the terminal, and a step of urethanizing the acrylic polymer block (B1) and polyethylene glycol with a bifunctional isocyanate compound It can manufacture by the method containing.

For example, 2,2′-azobis [N- (2-hydroxyethyl) -2-methylpropanamide] (for example, a commercial product “VA-086” manufactured by Wako Pure Chemical Industries, Ltd.) is used as a radical polymerization initiator. When an acrylic polymer is synthesized, an acrylic resin having a hydroxyl group at the terminal is obtained. The acrylic polymer block (B1) and the polyethylene oxide block (B2) are added to this by adding polyethylene glycol as a raw material constituting the polyethylene oxide block (B2) and causing a urethanization reaction using a bifunctional isocyanate compound. A block polymer (B) formed by bonding can be obtained.
Examples of the bifunctional isocyanate compound used in the urethanization reaction include 2,2′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2, Examples include 6-tolylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate.

Further, a method for synthesizing the block polymer (B) in which the acrylic polymer block (B1) and the polyethylene oxide block (B2) are bonded via the structure of the above formula (IC) will be described.
For example, a block polymer in which an acrylic polymer block (B1) and a polyethylene oxide block (B2) are bonded by the structure of the above formula (IC), an acrylic monomer is used as an azo polymerization initiator having a carboxyl group. It can be produced by a method including a step of polymerizing using and obtaining an acrylic polymer block (B1) having a carboxyl group and a step of esterifying polyethylene glycol to the acrylic polymer block (B1).

  For example, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] tetrahydrate (for example, a commercial product “VA-057” manufactured by Wako Pure Chemical Industries, Ltd.) as a radical polymerization initiator. Etc.) to synthesize an acrylic polymer, an acrylic resin having a carboxyl group at the end can be obtained. To this, polyethylene glycol is added as a raw material constituting the polyethylene oxide block (B2), and an esterification reaction is performed, whereby the acrylic polymer block (B1) and the polyethylene oxide block (B2) are combined. A coalescence (B) can be obtained.

  In addition, when obtaining a block polymer (B) formed by bonding via any structure of formulas (IB) to (IC), when using an azo polymerization initiator that is not a polymer as described above, "Other initiators" described as those that can be used together when using a polymer azo polymerization initiator can also be used in combination as appropriate. Moreover, a chain transfer agent can also be used suitably.

<Acrylic polymer block (B1)>
In the present invention, the acrylic polymer block (B1) refers to a block structure portion containing 10% or more of (meth) acrylic monomers having at least one acryloyl group and / or methacryloyl group out of all monomers. The acrylic polymer block (B1) is composed of a monomer having an average value of water / 1-octanol partition coefficient (LogP) of 0 or more and 2 or less, so that the obtained polymer has excessive mutual interaction with protein or tissue piece. The action can be suppressed and excellent blocking performance can be obtained.

  LogP is one of the numerical values representing the properties of the chemical substance, and is a constant value that does not depend on the addition amount. The target substance is a mixture of water and 1-octanol, and the concentration of each phase is shown in the common logarithm for the case where the aqueous phase and the octanol phase are in an equilibrium state in contact with each other. . When LogP increases, the hydrophobicity tends to increase relatively, and when LogP decreases, the hydrophilicity tends to increase relatively.

  The measurement of LogP can be generally performed by a flask immersion method described in JIS Japanese Industrial Standard Z7260-107 (2000). In addition, LogP can be estimated by a computational chemical method or an empirical method instead of actual measurement. As a method and software used for calculating LogP, publicly known methods can be used, but in the present invention, LogP is obtained by using a program incorporated in the system: ChemdrawPro 11.0 of CambridgeSoft.

The monomer having a water / 1-octanol partition coefficient (LogP) of 0 or more and 2 or less is not particularly limited.
Alkyl ester (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl acrylate;
(Meth) acryl methoxymethyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, ethoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate, propoxymethyl (meth) acrylate, propoxyethyl (meth) acrylate, 2- (2-methoxyethoxy) ethyl (meth) acrylate, 2- [2- (2-methoxyethoxy) ethoxy] ethyl (meth) acrylate, 2- (2-ethoxyethoxy) ethyl (meth) acrylate, 2- [2- Alkoxy group-containing monomers such as (2-ethoxyethoxy) ethoxy] ethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate;
Vinyl group-containing monomers such as (meth) acrylonitrile, vinyl acetate, butadiene, isoprene;
Amide group-containing monomers such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, 1-vinylimidazole, N-isopropylacrylamide, N, N-dimethylacrylamide;
Carboxyl groups such as (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, or alkylene oxide-added succinic acid (meth) acrylate having a carboxyl group at the terminal where alkylene oxide such as ethylene oxide or propylene oxide is repeatedly added. Containing monomers;
Etc.
These may be used alone or in combination of two or more. Among these compounds, n-butyl acrylate and 2-methoxyethyl acrylate are particularly preferable from the viewpoints of economy and operability, and if (meth) acrylic acid is incorporated in the acrylic polymer block (B1), the conductivity is improved. When the material (A) is dispersed, the carboxyl group derived from (meth) acrylic acid is neutralized with dimethylaminoethanol or the like to function as a charge repulsion site, and the dispersibility and stability of the conductive material (A) It contributes to the improvement.

  In this invention, if LogP of the acryl-type monomer to be used is the range of 0-2, it can be used as a raw material of a homopolymer part. Moreover, even if LogP of the (meth) acrylic monomer used is outside the range of 0 to 2, if the mass average value of LogP including other (meth) acrylic monomers is in the range of 0 to 2, It can be used as a raw material for the copolymer part.

Among monomers outside the range of Log P of 0 to 2, for example, acrylates having an alkyl group having 5 to 22 carbon atoms, methacrylates having an alkyl group having 4 to 22 carbon atoms, vinyl group-containing monomers such as styrene, maleic acid Carboxyl group-containing monomers such as 4-hydroxystyrene, N-hydroxyethyl (meth) acrylamide and other hydroxyl group-containing monomers, polyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, propoxy Polyethylene glycol (meth) acrylate, n-butoxypolyethylene glycol (meth) acrylate, n-pentoxypolyethylene glycol (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate It relates such monomers having polyethylene oxide moieties in the side chain, such as.
These may be used alone or in combination of two or more. Among these compounds, aromatic-containing monomers such as styrene, acrylates having 5 to 22 carbon atoms, and methacrylates having 4 to 22 carbon atoms in the alkyl group are particularly preferable. If these monomers are incorporated into the acrylic polymer block (B1), the adsorption force of the block polymer (B) to the conductive material (A) can be effectively controlled, and the dispersibility and stability can be further improved.

  Adsorption of the measurement target component in the body fluid can be effectively controlled by the balance between the hydrophilic polyethylene oxide block (B2) and the hydrophobic acrylic polymer block (B1) constituting the block polymer (B). . The block polymer (B) preferably contains a large amount of an acrylic polymer portion relative to the PEG portion, and the mass of the polyethylene oxide block (B2) / [acrylic polymer block (B1) and polyethylene oxide block (B2) The total mass] is 0.01 to 0.3, preferably 0.1 to 0.25. That is, it is preferable that it is 1-30 mass%, and it is more preferable that it is 10-25 mass%.

The mass of the PEG moiety (B2) / [total mass of the acrylic polymer moiety (B1) and the PEG moiety (B2)] can be calculated from the mass of the monomer used in the synthesis.
When a polymer azo polymerization initiator having a PEG moiety is used, when calculating the mass of the PEG moiety (B2), strictly speaking, only the mass of PEG in the azo polymerization initiator should be calculated. However, in the present invention, the mass of the polymer azo polymerization initiator having the PEG moiety (B2) is applied as it is. The mass of the acrylic polymer part (B1) is the total amount of acrylic monomers used for polymerization.
That is, when synthesized using 90 parts by mass of an acrylic monomer and 10 parts by mass of a polymer azo polymerization initiator having a PEG part (B2), the mass of the PEG part (B2) / [acrylic polymer part (B1) and PEG The total mass of the part (B2)] is 0.1.

<Molecular weight>
The mass average molecular weight of the block polymer (B) is preferably 1000 to 10000000. When the molecular weight is 1000 or more, the dispersibility and storage stability of the conductive material (A) can be ensured. Moreover, since it is 10000000 or less, the solvent solubility of resin improves and the aqueous | water-based electroconductive dispersion liquid obtained becomes a suitable viscosity, Therefore Coating applicability improves.
<Measurement method of mass average molecular weight (Mw)>
For the measurement of the mass average molecular weight Mw, GPC (gel permeation chromatography) “GPC-101” manufactured by Showa Denko KK was used. GPC is liquid chromatography that separates and quantifies substances dissolved in a solvent (THF; tetrahydrofuran) based on the difference in molecular size. For the measurement in the present invention, “KF-805L” (manufactured by Showa Denko KK: GPC column: 8 mm ID × 300 mm size) is connected in series to the column, the sample concentration is 1 wt%, the flow rate is 1.0 ml / min, the pressure The measurement was performed under the conditions of 3.8 MPa and a column temperature of 40 ° C., and the mass average molecular weight (Mw) was determined in terms of polystyrene. In the data analysis, a calibration curve, molecular weight, and peak area were calculated using software built in the manufacturer, and a mass average molecular weight was obtained with a retention time of 15 to 30 minutes as an analysis target.

  The block polymer (B) may be 0.1 to 500 parts by mass, more preferably 1 to 400 parts by mass with respect to 100 parts by mass of the conductive material (A). preferable. From the viewpoint of dispersibility, storage stability, and biocompatibility of the conductive material (A), the block polymer (B) is preferably 0.1 parts by mass or more. Moreover, it is preferable that a block polymer (B) is 500 mass parts or less from the point of electroconductivity improvement.

  In the present invention, a commercially available water-soluble resin type dispersant may be used in combination with the block polymer (B) as necessary. Examples of commercially available water-soluble resin type dispersants include Disperbyk-180, 183, 184, 185, 187, 190, 191, 192, 193, 194, 198, 199, 2010, 2012, 2015, 2090, 2091, 2095. , 2096, etc. (manufactured by Big Chemie), SOLSPERSE 20000, 27000, 40000, 41090, 44000, 46000, 47000, 64000, 65000, 66000, etc. (manufactured by Japan Lubrizol), Floren G-700AMP, G-700DMEA, WK-13E, GW-1500, GW-1640, etc. (manufactured by Kyoeisha Chemical Co., Ltd.), Borchi® Gen 1350, 0851, 1253, SN95, WNS, etc. (manufactured by Matsuo Sangyo Co., Ltd.), TEGO Dispers 650, 651, 652, 65 , 660C, 715W, 740W, 750W, 752W, 755W, 760W, etc. (manufactured by Sakai Kogyo Co., Ltd.), polyvinylpyrrolidone PVP-K30, K85, K90, etc. (manufactured by ISP Japan), ESREC BL-1, BL-2, BL- 5, BL-10, BL-1H, BL-2H, BL-S, BM-S, BM-1, BM-2, BM-5, BH-A, BX-1, BX-3, BX-5, etc. (Manufactured by Sekisui Chemical Co., Ltd.), carboxymethyl cellulose CMC 1105, 1110, 1130, 1140, 1170, 1190, 1205, 1210, 1240, 1250, etc. (manufactured by Daicel Chemical Industries, Ltd.), but are not limited thereto. .

<Water-dispersible resin particles (C)>
The water-dispersible resin particles (C) are in the form of particles in the liquid aqueous dispersant (D) described later, but when the aqueous liquid medium (D) is removed by heating and drying, the resin particles are fused together, A film is formed. That is, the water-dispersible resin particles (C) mainly serve as a binder that binds the particles of the conductive material (A) when forming a film. Moreover, since the water resistance of the electrode film after heat-drying, abrasion resistance, etc. can be improved, it is preferable to contain water-dispersible resin particles (C) in the aqueous conductive dispersion.

  As the water-dispersible resin particles (C) to be used, conventionally known ones can be used. For example, acrylic resin, polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy resin, urea resin, melamine resin, alkyd Examples thereof include resins, formaldehyde resins, silicon resins, fluororesins, synthetic rubbers such as styrene-butadiene rubber and fluororubber, and polymer compounds containing fluorine atoms such as polyvinylidene fluoride, polyvinyl fluoride, and tetrafluoroethylene. Further, a modified product, a mixture, or a copolymer of these resins may be used and can be dispersed in the aqueous liquid medium (D) described later. These water-dispersible resin particles (C) can be used alone or in combination.

A dispersion in which water-dispersible resin particles (C) are dispersed in an aqueous liquid medium (D) described later can be obtained as follows.
For example, the monomer that is the raw material of the resin is polymerized in the aqueous liquid medium (D) (emulsion polymerization, suspension polymerization, etc.)
After polymerization in an organic solvent that can dissolve the monomer that is the raw material of the resin (solution polymerization), the organic solvent is replaced with an aqueous liquid medium (D),
Polymerization is performed in a mixed solution of an organic solvent capable of dissolving the monomer as the resin raw material and the aqueous liquid medium (D), and the resin is precipitated in the aqueous liquid medium (D), and then the organic solvent is removed. ,
Etc., and can be obtained by various methods.
An emulsifier can be appropriately used in order to stably disperse the water-dispersible resin particles (C) in the aqueous liquid medium (D) during the polymerization or after the polymerization.

  The water dispersible resin particles (C) are 0.1 parts by mass or more and 500 parts by mass or less, more preferably 5 parts by mass or more and 400 parts by mass or less with respect to 100 parts by mass of the conductive material (A). It is preferable. The water-dispersible resin particles (C) are preferably 0.1 parts by mass or more from the viewpoint that the conductive material (A) is bound to form an electrode having excellent water resistance and scratch resistance. Moreover, it is preferable that a water-dispersible resin particle (C) is 500 mass parts or less from the point of electroconductivity improvement.

<Aqueous liquid medium (D)>
As the aqueous liquid medium used in the present invention, it is preferable to use water, but if necessary, for example, a small amount of liquid medium compatible with water is used to improve the coating property to the base substrate. You may do it.
Liquid media compatible with water include alcohols, glycols, cellosolves, amino alcohols, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid esters, and phosphoric acid esters , Ethers, nitriles and the like, and may be used as long as they are compatible with water.

<Disperser / Mixer>
The aqueous conductive dispersion of the present invention contains a conductive material (A), a block polymer (B), and an aqueous liquid medium (D). When the conductive material (A) and the block polymer (B) are dispersed in the aqueous liquid medium (D), a disperser or a mixer that is usually used for pigment dispersion or the like can be used.

  For example, mixers such as dispersers, homomixers, or planetary mixers; homogenizers such as “Clairemix” manufactured by M Technique, or “Fillmix” manufactured by PRIMIX; paint shaker (manufactured by Red Devil), ball mill, sand mill (Shinmaru Enterprises "Dynomill", etc.), Attritor, Pearl Mill (Eirich "DCP Mill", etc.), or Coball Mill, etc .; Media type dispersers; Wet Jet Mill (Genus, "Genus PY", Sugino Media-less dispersers such as “Starburst” manufactured by Machine, “Nanomizer” manufactured by Nanomizer, etc., “Claire SS-5” manufactured by M Technique, or “MICROS” manufactured by Nara Machinery; or other roll mills, etc. These are mentioned The present invention is not limited. Moreover, as the disperser, it is preferable to use a disperser that has been subjected to a metal contamination prevention treatment from the disperser.

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

  When the aqueous conductive dispersion of the present invention contains water-dispersible resin particles (C), the conductive material (A) and the block polymer (B) are pre-dispersed in the aqueous liquid medium (D) and then dispersed in water. An aqueous dispersion of the water-soluble resin particles (C) can be added, or the conductive material (A) and the block weight can be added to the dispersion in which the water-dispersible resin particles (C) are dispersed in the aqueous liquid medium (D). The coalescence (B) can be added and dispersed.

  The aqueous conductive dispersion of the present invention may further contain an oxidoreductase or an electron acceptor.

<Redox enzyme>
The oxidoreductase is appropriately selected depending on the component to be detected.
For example,
When the detection target component is alcohol, alcohol oxidase or alcohol dehydrogenase is used as an enzyme,
When the detection target component is glucose, β-D-glucose oxidase or glucose dehydrogenase is used as an enzyme,
When the detection target component is cholesterol, cholesterol oxidase or cholesterol dehydrogenase is used as an enzyme,
When the detection target component is phosphatidylcholine, phospholipase and choline oxidase are used as enzymes,
If the component to be detected is urea, use urease as the enzyme,
When the detection target component is uric acid, use uricase as an enzyme,
When the detection target component is lactic acid, lactate dehydrogenase is used as the enzyme,
When the component to be detected is oxalic acid, oxalate decarboxylase is used as the enzyme,
When the detection target component is pyruvate, pyruvate oxidase and pyruvate dehydrogenase are used as enzymes,
When the detection target component is ascorbic acid, ascorbate oxidase is used as an enzyme,
If the component to be detected is lactic acid, lactate oxidase is used as the enzyme,
When the detection target component is xanthine, xanthine oxidase is used as an enzyme,
When the detection target component is fructose, fructose dehydrogenase is used as an enzyme,
When the detection target component is creatine, creatine phosphokinase and creatine kinase are used as enzymes,
When the detection target component is glycerol, glycerol oxidase is used as an enzyme,
When the detection target component is acyl-coenzyme A, acyl-coenzyme A oxidase is used as the enzyme,
When the detection target component is tyramine, tyramine oxidase is used as an enzyme,
When the detection target component is an amino acid, an amino acid oxidase is used as an enzyme,
When the component to be detected is glycolate, glycolate oxidase is used as an enzyme,
When the detection target component is bilirubin, bilirubin oxidase is used as an enzyme,
When the detection target component is galactose, galactose oxidase is used as an enzyme,
When the detection target component is pyridoxal, pyridoxal-4-oxidase is used as an enzyme,
When the detection target component is sorbose, use sorbose oxidase as an enzyme,
When the component to be detected is glourolactose, globulactose oxidase is used as the enzyme,
When the detection target component is trimethylamine, flavin-containing monooxidase is used as the enzyme.

<Electron acceptor>
An electron acceptor is a low-molecular redox substance that is oxidized or reduced in response to a reaction of a biocatalyst such as an enzyme, and mediates electron transfer between the biocatalyst and the carbon substrate. Therefore, any electron acceptor can be used as long as it can exchange electrons with a biocatalyst such as an enzyme and can also exchange electrons with a carbon substrate.

  A specific example of the electron acceptor used in the present invention is preferably a π-conjugated compound in which single bonds and double bonds are alternately arranged. For example, although not specifically limited, phenazines such as 5-methylphenazinium methyl sulfate (phenazine methosulfate: PMS), 5-ethylphenazinium methyl sulfate (phenazine etsulfate: PES), etc. Compounds, phenothiazine compounds, ferricyanides such as potassium ferricyanide, ferrocene compounds such as ferrocene, dimethylferrocene, and ferrocenecarboxylic acid, quinone compounds such as naphthoquinone, anthraquinone, hyodoquinone, pyrroloquinoline quinone, cytochrome compounds, benzyl viologen And viologen compounds such as methyl viologen, and indophenol compounds such as dichlorophenol indophenol.

<Biosensor>
The biosensor of the present invention has a base substrate and an electrode disposed on the base substrate and in direct contact with the liquid to be measured, and the electrode is formed from the aqueous conductive dispersion described above. It is.
The cross-sectional schematic diagram of the biosensor of FIG. 1 is an example of an embodiment of the present invention.
Reference numeral 1 denotes an insulating base substrate made of a resin such as polyester, PET (polyethylene terephthalate), or polycarbonate (PC), and a base lead electrode 2 is formed thereon. On the lead electrode 2, electrodes 3 and 4 formed using the aqueous conductive dispersion of the present invention are provided. One electrode 3 is used as a working electrode, and the other electrode 4 is a counter electrode. A reaction layer 5 containing an electron acceptor and an enzyme is provided on the working electrode 3. Reference numeral 6 denotes an insulating layer that insulates the electrodes 3 and 4 from each other. A cover substrate 7 is provided to form a flow path 8 for a sample such as blood. For example, by introducing a blood sample into the channel 8, the concentration of the test substance in the blood is electrochemically analyzed.

<Method for producing electrode>
The electrodes 3 and 4 can be produced by applying the aqueous conductive dispersion of the present invention on the base substrate 1 and the base lead electrode 2 and removing the aqueous liquid medium (D).
The method for applying the dispersion is not particularly limited, and examples thereof include knife coaters, bar coaters, blade coaters, sprayers, dip coaters, spin coaters, roll coaters, die coaters, curtain coaters, screen printing, and the like. The general method of can be applied.

  In the biosensor of the present invention, the electrode itself exhibits biocompatibility. Therefore, even without covering or interposing the electrode with a biocompatible material, sufficient suppression of protein and cell adsorption, adhesion and activation of platelets can be achieved. Can be suppressed. That is, an electrode having biocompatibility can be produced more efficiently, enabling highly sensitive measurement of glucose concentration and stable measurement for a long time.

  The following examples further illustrate the present invention, but the following examples do not limit the scope of the present invention in any way. In the examples, “parts” and “%” represent “parts by mass” and “mass%”, respectively.

[Production Example 1]
<Preparation of block polymer (B)>
In a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, a reflux condenser, and a dropping tube, 150 parts by mass of methyl ethyl ketone (hereinafter abbreviated as MEK) as an organic solvent is charged in a nitrogen stream and stirred at 80 ° C. for 30 minutes. Heated for minutes. 80 parts by mass of methoxyethyl acrylate as a monomer in the dropping tube, 20 parts by mass of 2-ethylhexyl acrylate, 25 parts by mass of VPE0201 (manufactured by Wako Pure Chemical Industries, Ltd .: Macroazo Initiator) as a polymerization initiator, and 10 masses of MEK as a solvent The preparation was added dropwise over 2 hours. After completion of dropping, the mixture was aged for 6 hours. Then, it cooled to room temperature and stopped reaction. Thereafter, MEK was removed with a diaphragm pump to obtain a block polymer (B-1). Mw of the obtained polymer was 57400.

[Production Examples 2 to 7] [Comparative Production Examples 1 and 2]
A block polymer (B) was synthesized in the same manner as in Production Example 1 with the composition shown in Table 1.

[Comparative Production Example 3]
A reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer was charged with 98.0 parts of 1-butanol and replaced with nitrogen gas. The reaction vessel was heated to 110 ° C., and a mixture of 20 parts of 2-ethylhexyl methacrylate, 50 parts of styrene, 30 parts of acrylic acid and 2.0 parts of 2,2′-azobis (isobutyronitrile) was taken over 2 hours. Then, the polymerization reaction was carried out. After completion of the dropping, the reaction was further carried out at 110 ° C. for 3 hours, and after confirming that the conversion rate exceeded 98% by solid content measurement, the reaction was stopped by cooling to room temperature. Thereafter, 1-butanol was removed by a diaphragm pump to obtain a comparative copolymer (BH-3), and the mass average molecular weight was 52300.

The symbols in the table are as follows.
MEA: Methoxyethyl acrylate, Log P = 0.48
BA: Butyl acrylate, Log P = 1.88
MMA: methyl methacrylate, Log P = 1.11
AA: Acrylic acid, Log P = 0.38
BMA: Butyl methacrylate, Log P = 2.23
St: Styrene, LogP = 2.70
2EHA: 2-ethylhexyl acrylate, LogP = 3.53
LMA: lauryl methacrylate, Log P = 6.64
ISTA: Isostearyl acrylate, Log P = 7.47
VPE0201: Macroazo initiator AIBN manufactured by Wako Pure Chemical Industries, Ltd .: 2,2′-azobis (isobutyronitrile)

<Preparation of aqueous conductive dispersion>
[Example 1]
A mixture having the following composition was dispersed with a disper to obtain an aqueous conductive dispersion (S-1).
Ketjen Black (KB) EC-300J (manufactured by Lion Corporation) 2.5 parts Graphite SGO-10 (manufactured by SEC Carbon Corporation) 7.5 parts pure water 85.5 parts Block polymer of Production Example 1 (B-1) 3.0 parts aqueous dispersion of water-dispersible resin particles W-168 (solid content 50%) (manufactured by Toyochem)
1.5 parts

[Examples 2 to 10], [Comparative Examples 1 to 6]
The aqueous conductive dispersion is the same as the aqueous conductive dispersion (S-1) except that the conductive material (A), the block polymer (B), and other components are changed as shown in Table 2. Bodies (S-2 to 10) and comparative aqueous conductive dispersions (SH-1) to (SH-6) were obtained.

<Dispersibility evaluation of aqueous conductive dispersion>
Immediately after producing the aqueous conductive dispersions (S-1) to (S-10) of Examples 1 to 10 and the aqueous conductive dispersions (SH-1) to (SH-6) of Comparative Examples 1 to 6. The dispersion liquid was visually confirmed and judged according to the following criteria.
A: The conductive material (A) is uniformly dispersed.
Δ: The conductive material (A) is uniformly dispersed, but the viscosity of the aqueous conductive dispersion is extremely high or gelled.
X: Separation or sedimentation of the conductive material (A) is confirmed.

<Evaluation of storage stability of aqueous conductive dispersion>
The aqueous conductive dispersions (S-1) to (S-10) of Examples 1 to 10 and the aqueous conductive dispersions (SH-1) to (SH-6) of Comparative Examples 1 to 6 were prepared, The dispersion was visually confirmed after standing at room temperature for 1 day, and judged according to the following criteria.
◯: No change immediately after production Δ: Significant difference in fluidity from immediately after production, but no separation or sedimentation of conductive material (A) is observed ×: Separation of conductive material (A) Sedimentation is confirmed

  Table 2 shows the evaluation results of the dispersibility and storage stability of the aqueous conductive dispersion according to the above criteria.

The symbols in the table are as follows.
DMAE: Dimethylaminoethanol CMC: Carboxymethylcellulose EC-300J: KB (manufactured by Lion)
SGO-10: Graphite (manufactured by SEC Carbon)

<Preparation of electrode membrane for biosensor>
The aqueous conductive dispersions (S-1) to (S-10) of Examples 1 to 10 and the aqueous conductive dispersions (SH-1) to (SH-6) of Comparative Examples 1 to 6 were made into PET ( Polyethylene terephthalate) was coated on a substrate so that the weight per unit area after drying was 2 mg / cm ^2, and dried in air at 80 ° C. for 10 minutes to prepare biosensor electrode films.

<Coating property evaluation>
The coating property evaluation of the produced biosensor electrode film was evaluated by the following method. The biosensor electrode film was observed with a video microscope VHX-900 (manufactured by Keyence Corporation) at a magnification of 500 times, and coating unevenness (unevenness: evaluated by the density of the cathode layer) and pinhole (no cathode layer applied) Evaluation based on the presence or absence of defects was made according to the following criteria.

(village)
○: The density of the electrode is not confirmed (good).
(Triangle | delta): There are 1 to 3 shades of electrodes, but it is a very small area (no problem in practical use).
X: The density of the electrode is confirmed at 4 or more places, or 1 or more (not good) with the length of the density stripes of 5 mm or more.
(Pinhole)
○: No pinholes are confirmed (good).
Δ: 1 to 3 pinholes but very small (no problem in practical use)
X: Four or more pinholes are confirmed, or one or more pinholes having a diameter of 1 mm or more (very bad).

<Evaluation of platelet adhesion>
The biosensor electrode membrane is punched into 15 mmφ, fixed to a 24-well plate with a silicone ring, and 1 ml of phosphate buffered saline (hereinafter referred to as PBS) is added to each well to equilibrate the surface overnight. To do. After equilibration, PBS in each well is removed by aspiration, and 0.7 ml of human platelet-rich plasma is added to each well and incubated at 37 ° C. for 3 hours.
After culturing, the electrode membrane piece is taken out from each well, rinsed three times with PBS, and fixed with a 2.5% glutaraldehyde solution for 1 hour. After immobilization, the electrode membrane piece is dehydrated with an aqueous ethanol solution, freeze-dried, and then vapor-deposited with gold. This was observed with a scanning microscope to evaluate platelet adhesion. Here, evaluation was performed based on the following four evaluation criteria.
(Double-circle): Platelet adhesion is not seen at all on 24 electrode membranes for biosensors.
◯: Adhesion of platelets is observed in a part of the 24 biosensor electrode films.
Δ: Platelet adhesion is observed in many of the 24 biosensor electrode films, but formation of fibrin net cannot be confirmed.
X: Fibrin net formation can be confirmed in many of the 24 biosensor electrode films together with platelet adhesion.

<Evaluation of antithrombotic properties>
In the same manner as in the evaluation of platelet adhesion, PBS is added to the biosensor electrode membrane in a 24-well plate, and the surface is equilibrated overnight. After equilibration, PBS in each well is removed by aspiration, 0.7 ml of the following calcium-replenished blood is dispensed into each well, and incubated for 1 hour.
After culturing, the electrode membrane piece was taken out from each well, rinsed with PBS, and the ease of peeling of the thrombus mass was visually confirmed to evaluate the whole blood contact. Here, the evaluation was performed based on the following three evaluation criteria.
A: Thrombus clumps are not observed at all on all 24 biosensor electrode films.
A: A small amount of thrombus is attached to some of the 24 biosensor electrode films.
X: Adhesion of a large amount of thrombus is observed in many of the 24 electrode films for biosensors.

Calcium re-added blood: 178 μl of calcium chloride aqueous solution (1 mol / l) added to 10 ml of human fresh blood citrated blood immediately before the experiment.

<Evaluation of protein adsorption>
The electrode membrane for biosensor is punched out to 15 mmφ (test piece), fixed to a 24-well plate with a silicone ring, and 1 ml of HRP-IgG (Horseradishperoxidase-ImmunoglobulinG) solution diluted 10,000 times with PBS (phosphate buffer), In addition to the above test piece, the test piece was immersed so that only one side (upper surface) of the test piece was in contact with the protein solution. After incubating at room temperature for 1 hour, the test piece was transferred to another empty well and washed 4 times with PBS-T (0.1% Tween 20).
After washing, 1 ml each of TMBZ (3,3 ′, 5,5′-Tetramethylbenzidine) solution was dispensed as a staining solution into the well containing the above sample piece and incubated at room temperature for 10 minutes. Subsequently, 1 ml of StopSolution (WashandStopSolution for ELISA Whistleout Sulfur Acid, manufactured by Takara Bio Inc.) was dispensed to each well, the test piece was removed, and the absorbance of the solution in each well was measured. The measuring instrument used the MITHRAS2LD943-M2M microplate reader and measured the light absorbency of 450 nm (subwavelength 650 nm).
Separately, as a control, the same treatment and measurement were performed using a PET film, and the absorbance was used as a reference value, and evaluation was performed based on the following four evaluation criteria.
A: 0.2 ≧ absorbance in case of test piece / absorbance in case of PET film ○: 0.5 ≧ absorbance in case of test piece / absorbance in case of PET film> 0.2
Δ: 1 ≧ absorbance in case of test piece / absorbance in case of PET film> 0.5
X: Absorbance in the case of test piece / absorbance in the case of PET film> 1

  Table 3 shows the results of the biosensor electrode coating property evaluation and the protein adsorption property evaluation according to the above criteria.

  As can be seen from the results in Table 3, the electrodes made of the aqueous conductive dispersions of Examples 1 to 10 are free from unevenness and pinholes on the electrode surface, have a uniform electrode film with high smoothness, and platelets. It was also shown that thrombus and protein adsorptivity are low. On the other hand, some of the electrodes made of the aqueous conductive dispersions of Comparative Examples 1 to 6 did not form a uniform electrode film, and had a large amount of protein adsorption.

<Output characteristics as a glucose sensor>
[Production 1 of biosensor for glucose analysis]
The base lead electrode 2 was printed on the polyester resin substrate 1 by a screen printing technique and then dried by heating. 7.0 μL of the aqueous conductive dispersion (S-1) of Example 1 diluted 10-fold with pure water was dropped on the lead electrode 2 and dried in air at 80 ° C. for 10 minutes. A pole 3 and a counter electrode 4 were produced. An insulating film 6 in which an opening having a diameter of 400 μm was provided in advance at the position of the working electrode 3 and the counter electrode 4 by lithography was overlaid on the substrate 1 and thermocompression bonded.
Here, 0.05 μL of a mixed solution composed of 2 parts of ferrocene and 98 parts of isopropyl alcohol was uniformly dropped into the opening on the working electrode 3 and dried, and then a glucose oxidase (GOD: 1500 unit / mL in PBS) solution was dropped thereon. This was dried to produce a glucose analysis biosensor.

  In the same manner, the aqueous conductive dispersion (S-1) of Example 1 was changed to aqueous conductive dispersions (S-2) to (S-10) in Examples 2 to 10, and in Comparative Examples 1 to 6. The working electrode 3 and the counter electrode 4 were prepared by changing to aqueous conductive dispersions (SH-1) to (SH-6), respectively, and a glucose analysis biosensor was prepared.

[Preparation of sample solution 1]
Glucose was dissolved in a phosphate buffer solution (PBS), and the solution was adjusted so that the glucose concentration was 50, 100, 200, 250, or 300 mg / dl. In addition, a solution having a glucose concentration of 0 mg / dl was also prepared.

[Preparation of sample solution 2]
Albumin (4.5 g / dl) and γ-globulin (1.6 g / dl) were dissolved in phosphate buffer (PBS) to prepare a protein solution. 5 ml of a 1.25 g / dl glucose solution was added to 20 ml of the solution to adjust the glucose concentration to 250 mg / dl.
Similarly, the solution was adjusted so that the glucose concentrations were 50, 100, 200, and 300 mg / dl. In addition, a solution having a glucose concentration of 0 mg / dl was also prepared.

<Response sensitivity as a glucose sensor>
[Measurement of oxidation current of sample solution 1]
A plurality of glucose analysis sensors of each example and each comparative example (a number corresponding to the type of glucose concentration of the sample solutions 1 and 2) were prepared, and both electrodes of the enzyme reaction layer 5 and the counter electrode 4 of each glucose analysis sensor were prepared. A glucose solution of each concentration was dropped so as to cover, and a constant voltage of +350 mV, which is the oxidation-reduction potential of ferrocene, was applied to the working electrode 3 with reference to the counter electrode 4, and the oxidation current after 30 seconds was measured.
[Measurement of oxidation current of sample solution 2]
For sample solution 2, as in sample solution 1, the oxidation current was measured when the glucose concentration was 0, 50, 100, 200, 250, and 300 mg / dl.

[Evaluation]
Using the oxidation current value of sample solution 1 as a reference, the oxidation current values of sample solution 2 having the same glucose concentration were compared and evaluated according to the following criteria.
(Double-circle): The oxidation current value of the sample liquid 2 holds 50% or more of the oxidation current value of the sample liquid 1 in the entire concentration region.
○: In the concentration region of 100 mg / dl or more, the oxidation current value of the sample solution 2 holds ± 50% or more of the oxidation current value of the sample solution 1, but in the concentration region of less than 100 mg / dl, the oxidation of the sample solution 2 The current value is less than 50% of the oxidation current value of the sample solution 1.
Δ: The oxidation current value of the sample solution 2 holds 50% or more of the oxidation current value of the sample solution 1 in the concentration region of 200 mg / dl or more, but the oxidation current of the sample solution 2 in the concentration region of less than 200 mg / dl. The value is less than 50% of the oxidation current value of the sample solution 1.
X: Although the oxidation current value of the sample solution 2 holds 50% or more of the oxidation current value of the sample solution 1 at a concentration of 300 mg / dl, the oxidation current value of the sample solution 2 is at a concentration region of 250 mg / dl or less. The oxidation current value of sample solution 1 is less than 50%.

<Stability as a glucose sensor>
A sample solution 2 having a glucose concentration of 250 mg / dl was dropped so as to cover both electrodes of the enzyme reaction layer 5 and the counter electrode 4, and immediately, the counter electrode 4 was used as a reference, and the working electrode 3 was set at +350 mV, which is the oxidation-reduction potential of ferrocene. A voltage was applied, and the oxidation current after 30 seconds was measured. This was the initial current value.
Next, a sample solution 2 having a glucose concentration of 250 mg / dl added dropwise so as to cover both the enzyme reaction layer 5 and the counter electrode 4 was left at room temperature for one day. In addition, the sample solution was appropriately dropped so that the sample solution on the electrode was not dried. After 1 day, a constant voltage of +350 mV, which is the oxidation-reduction potential of ferrocene, was applied to the working electrode 3 with reference to the counter electrode 4, and the oxidation current after 30 seconds was measured. This was defined as the current value after one day.

Evaluation was performed based on the following three-level evaluation criteria.
◎: Holds a value of 90% or more of the initial value ○: Holds a value of 50% or more of the initial value ×: Holds a value of less than 50% of the initial value

Table 4 shows the results of evaluating the output characteristics of the glucose sensor according to the above criteria.

As can be seen from the results in Table 4, the glucose sensor using the electrodes made of the aqueous conductive dispersions of Examples 1 to 10 showed high-sensitivity output characteristics in a wide range of concentration even in the protein solution, and the day time passed. The sensitivity after the past was also maintained. From this, it was shown that highly sensitive measurement can be stably performed.
On the other hand, in the glucose sensor using the electrode composed of the aqueous conductive dispersion of Comparative Examples 1 to 6, the oxidation current value obtained in the protein solution is low, and the output value does not increase particularly in the region where the glucose concentration is low. It was. Furthermore, the sensitivity after a day had also dropped.

  From the above results, the glucose sensor using the electrode composed of the aqueous conductive dispersion of the present invention was able to perform stable and highly sensitive analysis because protein adsorption was suppressed. Moreover, since the electrode itself can suppress protein adsorption without coating or interposing the electrode with a biocompatible material, a glucose sensor can be produced more efficiently.

  The aqueous conductive dispersion of the present invention can be applied to an electrode for a biosensor excellent in dispersibility and storage stability of a conductive material and excellent in biocompatibility. By adding a sample solution to the biosensor, the substrate concentration can be measured. And the influence on the response by adsorption of solid components such as proteins and erythrocytes is eliminated, and stable and highly sensitive analysis can be performed for a long time. Furthermore, since the electrode itself can suppress protein adsorption without covering or interposing the electrode with a biocompatible material, a biosensor can be more efficiently produced.

1: Base material 2: Base lead electrode 3: Working electrode 4: Counter electrode 5: Reaction layer 6 containing electron acceptor and enzyme 6: Insulating layer 7: Cover substrate 8: Flow path

Claims (7)

An aqueous conductive dispersion comprising a conductive material (A), a block polymer (B), and an aqueous liquid medium (D),
The block polymer (B) comprises an acrylic polymer block (B1) formed from an acrylic monomer having an average value of water / 1-octanol partition coefficient (LogP) of 0 or more and 2 or less, and a polyethylene oxide block (B2). )
The mass of the polyethylene oxide block / [total mass of the acrylic polymer block and the polyethylene oxide block] included in the block polymer (B) is 0.01 to 0.3.
Aqueous conductive dispersion.   The aqueous conductive dispersion according to claim 1, wherein the conductive material (A) is a carbon material. 3. The aqueous conductive material according to claim 1, wherein the block polymer (B) is bonded via a structure of any one of the following formulas (IA), (IB) or (IC): Dispersion.

The aqueous conductive dispersion according to any one of claims 1 to 3, wherein an acrylic polymer block and a polyethylene oxide block contained in the block polymer (B) are bonded with a structure of the following formula (IA). body.

  The aqueous conductive dispersion according to any one of claims 1 to 4, further comprising water-dispersible resin particles (C). A biosensor having a base substrate and an electrode disposed on the base substrate and in direct contact with the liquid to be measured,
A biosensor in which the electrode is formed from the aqueous conductive dispersion according to any one of claims 1 to 5. A biosensor manufacturing method comprising: a base substrate; and an electrode disposed on the base substrate and in direct contact with the liquid to be measured,
The aqueous conductive dispersion according to any one of claims 1 to 5 is applied to a predetermined position of the base substrate, the aqueous liquid medium (D) is removed, and the electrode is formed.
Biosensor manufacturing method.