JP2010038569A - Chemical substance detecting element, chemical substance detector and manufacturing method of chemical substance detecting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chemical substance detecting element capable of detecting a specific substance with high selectivity and high sensitivity and capable of achieving the miniaturization of a chemical substance detector and the shortening of a measuring time, a chemical substance detector and a manufacturing method of the chemical substance detecting element. <P>SOLUTION: The chemical substance detecting element contains a carbon nano structure 74 of which the surface is modified by protein selectively reacting with the specific substance, for example, nitrile hydratase (NHase) 72 selectively reacting with nitrogen monoxide (NO) 76 through an amide bond. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a chemical substance detection element for detecting a specific substance, and more particularly to a technique that improves the sensitivity and selectivity of a chemical substance detection element with respect to a measurement target gas and enables rapid and simple detection.

  Japan is aging and declining birthrate, and in the near future it is predicted that one in three people will be 65 years of age or older. Under such circumstances, the urgent need is to curb national medical expenses. For this reason, the enhancement of preventive medicine has attracted attention. This is because medical expenses can be reduced if the number of people who get sick is reduced by the improvement of preventive medicine.

  In order to enhance preventive medicine, a system that can manage health by using health information measured by familiar devices is necessary. There are biological samples such as blood, urine, sweat, saliva and exhaled breath as an index for easily grasping an individual's health condition. Such a biological sample contains a plurality of substances (hereinafter referred to as “markers”) whose numerical values change due to disease or signs thereof, such as blood glucose level in blood. Therefore, there is a high possibility that an individual's health status can be grasped by measuring the amount of change in the marker, and health management and early detection of a disease can be performed by constantly measuring the marker. Among the above-mentioned biological samples, exhaled breath has little physical damage because it includes a plurality of types of markers, can be sampled and measured quickly and easily, and the measurement target is gaseous and can be measured non-invasively. From the point, it can be said that it is the most suitable biological sample for measurement.

  Non-Patent Document 1 shows the relationship between a disease and a marker during expiration. A part of this is quoted in Table 1.

Gas chromatography and chemiluminescence methods are known as methods for measuring markers in exhaled breath, but these measuring methods are practical because they require large and expensive measuring instruments and require familiarity with operation methods. is not. Although measurement using an oxide semiconductor gas sensor is also known, the detection limit is as low as 10 ³ ppm level and the sensitivity is low, and it is not suitable for measuring a marker in exhaled breath having a concentration on the order of ppm from ppb. Furthermore, since it is necessary to heat to 300 ° C. in order to operate as a gas sensor, it is not practical.

  As a method for solving such a problem, Non-Patent Document 2 proposes a gas sensor using carbon nanotubes (hereinafter sometimes referred to as “CNT (Carbon Nano Tube)”). CNT is a tubular carbon material having a diameter of nano order, and has a structure in which a graphene sheet is rolled into a cylindrical shape. This graphene sheet is obtained by continuously forming a two-dimensional graphite structure in which six carbon atoms form a regular hexagonal plate structure and are bonded. Since CNT has a high conductivity and is a nano-order material, the gas sensor disclosed in Non-Patent Document 2 can realize ultra-small size, low power consumption and portability, and is simple and practical. Ideal as a health check. However, since the selectivity with respect to the gas to be measured is low, the resistance change occurs in the same way regardless of which gas molecules approach, and there is a problem that a qualitative analysis of a substance present in the atmosphere cannot be performed.

  As shown in Table 1, nitric oxide (NO), which is one of the markers during expiration, is detected at a high concentration in the expiration of asthma patients. In addition, it is one of in vivo neurotransmitters and is known to play an important role in immune responses and blood pressure regulation. Therefore, by detecting the concentration of nitric oxide (NO) in exhaled breath, it is possible to know the prediction and extent of the disease, and the high-performance nitric oxide sensor (hereinafter referred to as “NO sensor”). Realization is desired.

Non-Patent Document 3 proposes a NO sensor using CNTs. The NO sensor disclosed in Non-Patent Document 3 improves the selectivity for the gas to be measured by modifying the CNT surface with a substance that reacts with a specific substance. That is, by using a CNT whose surface is modified with polyethyleneimine that reacts with nitrogen dioxide (NO ₂ ), and further providing a catalyst for converting nitrogen monoxide to nitrogen dioxide, it is a specific marker in the exhaled breath. Nitric oxide (NO) is detected.

Wenting Tsao et al., “Breath Analysis: Potential for Clinical Diagnosis and Exposure Assessment”, Clinical Chemistry, 52: 5, p. 800-p. 811, 2006 (Wenqing Cao et al., “Breath Analysis: Potential for Clinical Diagnosis and Exposure Assessment”, Clinical Chemistry, vol. 52: 5, p. Riichiro Saito, “Outline and Issues of Carbon Nanotubes”, Functional Materials, vol. 21, no. 5, p. 6-p. 14, May 2001 issue Alexander Star et al., “Carbon Nanotube Sensor for Breathing Components”, Nanotechnology, Vol. 18, p. 375502 (7 pp), 2007 (Alexander Star et al., “Carbon nanotube sensors for exhaled breath components”, Nanotechnology, vol. 18, p. 375502 (7 pp), 2007).

  In general, the nitric oxide concentration in the breath of a healthy person is about 10 ppb, and the nitric oxide concentration in the breath of an asthmatic patient is about 50 ppb. Therefore, nitric oxide (NO) in the breath is detected. Therefore, a NO sensor for which the detection lower limit is as high as the ppb level is required. In the NO sensor disclosed in Non-Patent Document 3, such a high sensitivity level that can detect nitric oxide (NO) in exhaled air has not been achieved.

In addition, the NO sensor disclosed in Non-Patent Document 3 does not operate normally unless the catalyst used is in an environment with a humidity of about 15% to 30%, so the humidity of the measurement target gas must be adjusted. In order to detect an accurate amount of nitric oxide, nitrogen dioxide (NO ₂ ) contained in the measurement target gas must be removed in advance. Therefore, when measuring nitric oxide (NO) in exhaled air by the NO sensor disclosed in Non-Patent Document 3, not only the catalyst but also nitrogen dioxide (NO ₂ ) contained in about 4% in the exhaled air. A configuration necessary for pretreatment such as removal and humidity adjustment has to be provided, and there is a problem that the apparatus becomes large. In addition, there is a problem that the measurement time becomes long because a multi-step process is required for the measurement.

  The present invention has been made in view of the above-mentioned problems, and its purpose is to detect a chemical substance capable of detecting a specific substance with high selectivity and high sensitivity, and further achieving downsizing of the apparatus and shortening of measurement time. An element, a chemical substance detection device, and a method for manufacturing a chemical substance detection element are provided.

  The chemical substance detection element according to the first aspect of the present invention includes a carbon nanostructure that is surface-modified with a protein that selectively reacts with a specific substance. Thereby, a specific substance can be detected with high selectivity and high sensitivity. In addition, since the specific substance can be directly detected without being converted into another substance, it is possible to omit the configuration and process required for the conversion and the configuration and process required for the pretreatment accompanying the conversion. Therefore, it is possible to reduce the size of the chemical substance detection element and shorten the measurement time.

  Preferably, the carbon nanostructure is made of a carbon-based conductive material selected from the group consisting of carbon nanotubes, carbon nanofibers, carbon nanohorns, and fullerenes. Since the carbon nanostructure selected from such a group has a nano-order fine structure, the responsiveness and the detection lower limit are greatly improved. Therefore, it is possible to detect a very small amount of a specific substance on the order of ppb, which is difficult with a conventional chemical substance detection element.

  More preferably, the carbon nanostructure is surface-modified with 0.30 μmol to 0.50 μmol of protein with respect to 1 mg of the carbon nanostructure. As a result, the resistance of the chemical substance detection element can be optimized so that the sensitivity of sensing is optimal, and therefore, the specific substance can be detected with higher selectivity and higher sensitivity.

  More preferably, the carbon nanostructure has an amino group or carboxylic acid for forming an amide bond with the carboxylic acid or amino group of the protein, and the protein is surface-modified to the carbon nanostructure by the amide bond. . In this way, the protein is firmly fixed to the surface of the carbon nanostructure by being surface-modified through an amide bond, so that the high selectivity and high sensitivity of the chemical substance detection element are maintained over a long period of time. can do.

  More preferably, the specific substance is nitric oxide. Thereby, nitric oxide can be detected with high selectivity and high sensitivity. Moreover, since it can detect directly, without converting nitric oxide into nitrogen dioxide, the structure and process which are required for conversion, and the structure and process which are required for the pre-processing accompanying conversion can be omitted. Therefore, it is possible to reduce the size of the chemical substance detection element and shorten the measurement time.

  More preferably, the protein comprises nitrile hydratase. Nitrile hydratase is a protein that can be isolated from microorganisms and easy to handle because it can be used in the atmosphere. Therefore, the convenience of the chemical substance detection element can be further improved.

  More preferably, the nitrile hydratase is an iron-type nitrile hydratase. This makes it possible to regenerate the chemical substance detection element using photoresponsiveness, so that the high selectivity and high sensitivity of the chemical substance detection element can be maintained over a long period of time.

  A chemical substance detection apparatus according to a second aspect of the present invention includes the above-described chemical substance detection element, and a detection unit that is electrically connected to the chemical substance detection element and detects a change in electrical resistance of the chemical substance detection element. Including. As described above, since the chemical substance detection apparatus includes the above-described chemical substance detection element, the specific substance can be detected with high selectivity and high sensitivity, and further downsizing of the apparatus and shortening of the measurement time can be achieved.

  In the method for producing a chemical substance detection element according to the third aspect of the present invention, in the first step, a protein that selectively reacts with a specific substance, a carboxylic acid, and an amino group are condensed to form an amide bond. A carbon nanostructure having an amino group or a carboxylic acid for forming an amide bond with the surface modification solution prepared in the second step by preparing a surface modification solution containing a condensing agent and a solvent After the body is put in, a carbon nanostructure whose surface is modified with protein is produced by irradiating ultrasonic waves.

  Thus, since the carbon nanostructure having an amino group or carboxylic acid can be uniformly dispersed in the surface modification solution by using ultrasonic waves, the surface of the carbon nanostructure can be uniformly modified with protein. Therefore, a chemical substance detection element capable of detecting a specific substance with higher selectivity and sensitivity can be manufactured. In addition, since the surface of the protein is modified to the carbon nanostructure by an amide bond, the protein can be firmly fixed on the surface of the carbon nanostructure. Therefore, a chemical substance detection element capable of maintaining high selectivity and high sensitivity over a long period can be manufactured.

  Preferably, in the first step, a surface modifying solution further containing a base for making the surface modifying solution into a basic condition is prepared. As a result, the amide bond formation reaction can be further promoted, so that a carbon nanostructure having a surface modified with a protein can be more easily produced.

  More preferably, the method for producing a chemical substance detection element further includes a third step of producing a sheet-like substrate including carbon nanostructures surface-modified with proteins. As a result, carbon nanostructures surface-modified with proteins can be reacted in a uniform state with a specific substance, so that a specific substance can be detected with higher selectivity and sensitivity. A detection element can be manufactured.

  More preferably, the third step includes a step of preparing a dispersion in which carbon nanostructures surface-modified with proteins are dispersed, and a step of filtering the dispersion. Thereby, the base | substrate containing the carbon nanostructure by which the surface modification was uniformly performed can be formed in uniform thickness and for a short time.

  According to the present invention, the chemical substance detection element includes a carbon nanostructure surface-modified with a protein that selectively reacts with a specific substance. Thereby, a specific substance can be detected with high selectivity and high sensitivity. In addition, since the specific substance can be directly detected without being converted into another substance, it is possible to omit the configuration and process required for the conversion and the configuration and process required for the pretreatment accompanying the conversion. Therefore, it is possible to reduce the size of the chemical substance detection element and shorten the measurement time.

  In the following description and drawings, the same reference numerals and names are assigned to the same components. Their functions are also the same. Therefore, detailed description thereof will not be repeated each time.

−Configuration−
FIG. 1 is a configuration diagram of a chemical substance detection apparatus 20 including a chemical substance detection element 32 according to an embodiment of the present invention. Referring to FIG. 1, a chemical substance detection device 20 includes a DC power supply 30, a chemical substance detection element 32 according to the present embodiment, one end of which is connected to a positive terminal of the DC power supply 30, and a chemical substance detection element 32. An input is connected to the load resistor 34 connected between the other end of the DC power source 30 and the negative terminal of the DC power supply 30, and the contact point between the chemical substance detection element 32 and the load resistor 34, and the potential change at this contact point is amplified. And an amplifier 36. When detecting a chemical substance, a DC voltmeter (not shown) is connected to the other terminal of the amplifier 36 in order to measure this potential change.

  2A and 2B are diagrams showing the configuration of the chemical substance detection element 32, FIG. 2A is a side view, and FIG. 2B is a top view. Referring to FIG. 2, the chemical substance detection element 32 includes a chemical substance detection unit 42 composed of an assembly of carbon nanostructures whose surface is modified by a protein that selectively reacts with a specific substance, which will be described later, and a chemical substance detection unit. The electrode 44 and the electrode 46 arrange | positioned at the both ends of the part 42, and the board | substrate 48 with which these are installed on the surface are included.

  Hereinafter, the chemical substance detection unit 42, the electrode 44 and the electrode 46, and the substrate 48 constituting the chemical substance detection element 32 will be described in detail.

[Chemical substance detection unit 42]
The chemical substance detection unit 42 includes an aggregate of carbon nanostructures whose surface is modified with a protein that selectively reacts with a specific substance. When a chemical substance adheres to the surface of the carbon nanostructure, electron transfer occurs and an electromotive force is generated. In other words, a potential difference or a change in electrical resistance occurs between two points of the carbon nanostructure. If this change in electrical resistance is detected, chemical substances can be detected (sensing). In addition, when the surface of the carbon nanostructure is modified with a protein that selectively reacts with a specific substance, the above-described change in electrical resistance is linked to the behavior of the protein modified on the surface, so only the specific substance Can be obtained. Thus, since the above-mentioned protein surface-modified carbon nanostructure having conductivity is used as the chemical substance detection unit 42, the change in conductivity, that is, the change in resistance can be measured. It becomes possible to detect specific substances. Therefore, it is not necessary to provide a configuration such as an electrolyte as compared with a chemical substance detection element or the like that uses a change in electrochemical behavior of the electrolyte solution containing the above-described protein, and thus the chemical substance detection element 32 can be further downsized. Can be achieved.

  The protein is not particularly limited as long as it reacts selectively with a specific substance. For example, a catalytic protein such as an enzyme, a transport protein, a protective protein such as an antibody, and the like can be used. However, it is preferable to use a gas molecule sensor protein because specific gas molecules can be recognized with high selectivity. Table 2 shows typical gas molecule sensor proteins.

Referring to Table 2, examples of gas molecular sensor proteins include nitrile hydratase (NHase) and sGC that selectively react with nitric oxide (NO), and CooA that selectively reacts with carbon monoxide (CO). And NPAS2, as well as FixL, DOS and HemAT, which react selectively with oxygen (O ₂ ). Among these, it is particularly preferable to use nitrile hydratase (NHase) because it can be isolated from microorganisms and can be used in the atmosphere, so that it is easy to handle. Thereby, the convenience of the chemical substance detection element 32 can be further improved.

  Hereinafter, nitrile hydratase (NHase) will be described in detail.

Nitrile hydratase (NHase) is an enzyme present in various actinomycetes and bacteria such as Pseudomonas, and catalyzes a hydrolysis reaction of a nitrile compound to an amide compound. Nitrile hydratase (NHase) has a trivalent iron atom (Fe (III)) or a trivalent cobalt atom (Co (III)) as an active center, and serine, cysteine sulfinic acid with respect to this active center. And a structure in which three amino acids of cysteine sulfenic acid are coordinated. That is, a thiol sulfur atom (S) of three cysteine residues in serine, cysteine sulfinic acid, and cysteine sulfenic acid, and two main-chain amido nitrogen atoms (N) in serine and cysteine sulfenic acid are arranged. Acts as a ligand. Here, the thiol sulfur atom, a sulfur atom constituting a group formed by removing a proton (H) from a thiol group (-SH), i.e., -S ^- indicates that the sulfur atom constituting a group represented by . The amido nitrogen atom (N) is a nitrogen atom constituting a group obtained by removing a proton (H) from a secondary amide group (—CONH—) composed of carbonyl and amine, that is, represented by —CON ⁻ —. Represents a nitrogen atom constituting the group. The ligand is an electron pair donor that donates an unshared electron pair of each ligand to the active center.

  In nitrile hydratase (NHase), a trivalent iron atom (Fe (III)) or a trivalent cobalt atom (Co (III)) is bonded to nitric oxide (NO), and further serine, cysteine sulfinic acid, And three oxygen atoms in cysteine sulfenic acid have a function of holding nitric oxide (NO). Therefore, nitrile hydratase (NHase) reacts selectively with nitric oxide molecules (NO), that is, has a significantly higher reactivity with other chemical species than with nitric oxide molecules (NO). It has low properties. Therefore, other chemical species are difficult to react with nitrile hydratase (NHase). The chemical substance detection unit 42 composed of an assembly of carbon nanostructures surface-modified with nitrile hydratase (NHase), which is a protein that selectively reacts with nitric oxide (NO), NO) can be detected with high selectivity and high sensitivity. Moreover, since it can detect directly, without converting nitric oxide into nitrogen dioxide, the structure and process which are required for conversion, and the structure and process which are required for the pre-processing accompanying conversion can be omitted. Therefore, the chemical substance detection element 32 can be downsized and the measurement time can be shortened.

  Hereinafter, those having an iron atom at the active center are referred to as iron-type nitrile hydratase, and those having a cobalt atom are referred to as cobalt-type nitrile hydratase. Iron-type nitrile hydratase exhibits photoresponsiveness to nitric oxide (NO). That is, under dark conditions, a trivalent iron atom (Fe (III)) and nitric oxide (NO) are bonded, and three oxygen atoms in serine, cysteine sulfinic acid, and cysteine sulfenic acid are one. Nitrogen oxide (NO) is retained, and it becomes an inactive type that does not exhibit catalytic action. On the other hand, under bright conditions, nitric oxide (NO) retained in the inactive type is dissociated and released to become an active type that exhibits catalytic action. The chemical substance detection unit 42 composed of an aggregate of carbon nanostructures surface-modified with iron-type nitrile hydratase (NHase) performs a regeneration process of the chemical substance detection unit 42 using photoresponsiveness. Therefore, the high selectivity and high sensitivity of the chemical substance detection element 32 can be maintained over a long period of time.

  The carbon nanostructure is preferably made of a carbon-based conductive material selected from the group consisting of carbon nanotubes (CNT), carbon nanofibers, carbon nanohorns, and fullerenes, and more preferably made of CNTs. Such carbon nanostructures can be produced using conventional methods. Moreover, what was processed with hydrochloric acid for impurity removal can also be used. Since the carbon nanostructure selected from the above group is a nano-order fine structure, the responsiveness and the lower detection limit are greatly improved. That is, the time from when the chemical substance adheres to the surface of the carbon nanostructure until the change in electric resistance of the carbon nanostructure occurs is very short due to the conductivity and nanostructure of the carbon nanostructure. In addition, due to the feature point that the surface area of carbon nanostructure is large and the feature point that all the constituent atoms constitute the surface, the influence of adhesion by chemical substances is reflected in the electrical resistance. Loss due to electron scattering is extremely small. Therefore, the carbon nanostructure selected from the above group can confirm the presence of a small amount of a specific substance of the order of ppb, for example, nitric oxide (NO), which has been difficult with a conventional chemical substance detection element. Become. In the case where the carbon nanostructure is composed of carbon nanotubes, the above-described effects are more remarkably exhibited. In this way, by detecting a small amount of a specific substance in the order of ppb, it is possible to obtain the chemical substance detection element 32 capable of measuring a marker or the like in exhaled breath. Therefore, it becomes possible to easily grasp an individual's health condition.

  The carbon nanostructure is preferably surface-modified with 0.30 μmol to 0.50 μmol of protein with respect to 1 mg of the carbon nanostructure. As a result, the sensitivity of the chemical substance detection element 32 can be optimized so that the sensitivity of sensing can be optimized, so that the specific substance can be detected with higher selectivity and higher sensitivity. When the protein surface modification amount is less than 0.30 μmol with respect to 1 mg of the carbon nanostructure, the detection sensitivity of the chemical substance detection element 32 becomes too low, and a response to a specific substance such as nitric oxide (NO) cannot be confirmed. There is a fear. In addition, since the chemical substance can be sensed only with the carbon nanostructure, it may be difficult to distinguish the specific substance from other chemical substances. If the surface modification amount of the protein is more than 0.50 μmol with respect to 1 mg of the carbon nanostructure, the resistance value of the chemical substance detection element 32 becomes too large and it becomes difficult to detect the signal output from the chemical substance detection element 32. There is a risk.

  The carbon nanostructure has an amino group or carboxylic acid for forming an amide bond with the carboxylic acid or amino group of the protein, and the protein has an amino group of the carboxylic acid and the carbon nanostructure of the protein, or The carbon nanostructure is preferably surface-modified by an amide bond formed by the condensation of the amino group of the protein and the carboxylic acid of the carbon nanostructure. As described above, since the surface is modified through the amide bond, the protein is firmly fixed to the surface of the carbon nanostructure, so that the chemical substance detection element 32 has high selectivity and high sensitivity over a long period of time. Can be maintained.

  The amount of amino group or carboxylic acid introduced into the carbon nanostructure is preferably 0.30 mmol to 0.50 mmol with respect to 1 g of the carbon nanostructure. Thereby, since the surface modification amount of the protein with respect to the carbon nanostructure can be adjusted to be within the above-mentioned preferable range, the specific substance can be detected with higher selectivity and sensitivity. The amount of amino group introduced into the carbon nanostructure can be determined by a kaiser test or a picric acid test. The amount of carboxylic acid introduced into the carbon nanostructure can be determined by a test method generally used in the art. A method for introducing an amino group or a carboxylic acid and a method for forming an amide bond to the carbon nanostructure will be described later.

[Electrode 44 and Electrode 46]
The constituent materials of the electrode 44 and the electrode 46 are not particularly limited as long as they have conductivity, but materials made of gold, silver, platinum, palladium, nickel, tungsten, or alloys thereof can be used. . The distance between the electrode 44 and the electrode 46 is not particularly limited as long as it is a distance capable of sensing a specific substance, but is preferably 1.0 cm to 2.0 cm. The electrode 44 and the electrode 46 can be formed on the chemical substance detection unit 42 by a known method such as a vapor deposition method or a method of applying a conductive paste.

[Substrate 48]
The constituent material of the substrate 48 is not particularly limited as long as it has insulating properties, but a material made of a polymer material such as silicon, quartz, glass, or a fluororesin can be used. The thickness of the substrate 48 is not particularly limited as long as it has an appropriate mechanical strength, but it is preferably 100 μm to 1000 μm. As the substrate 48, it is preferable to use a membrane filter made of Teflon (registered trademark) (for example, a commercial product (trade name: OMNIPORE ^™ MEMBRANE FILTERS 0.2 μm (pore diameter) JG, manufactured by MILLIPORE), etc.).

-Manufacturing Method of Chemical Substance Detection Element 32-
Hereinafter, a method for manufacturing the chemical substance detection element 32 will be described. FIGS. 3A to 3D are diagrams for explaining an example of a method for manufacturing the chemical substance detection unit 42. An example of the manufacturing method of the chemical substance detection part 42 includes a first step to a third step, which will be described later, proceed in the order of FIGS.

  Referring to FIGS. 3A and 3B, in the first step, the above-mentioned protein that selectively reacts with a specific substance, a carboxylic acid and an amino group are condensed to form an amide bond. The surface modification solution 50 containing a condensing agent and a solvent is prepared, and in the second step, carbon having an amino group or a carboxylic acid for forming an amide bond is prepared with respect to the prepared surface modification solution 50. After introducing the nanostructure 52, the ultrasonic wave 54 is irradiated. By the first step and the second step, a carbon nanostructure surface-modified with the above-described protein (hereinafter referred to as “surface-modified carbon nanostructure”) can be produced. A method of performing surface modification using ultrasonic irradiation in this way is hereinafter referred to as an ultrasonic modification method.

  The condensing agent is not particularly limited as long as it is generally used as a coupling agent in an amide bond forming reaction such as peptide synthesis. For example, N-hydroxybenzotriazole such as 1-hydroxybenzotriazole (HOBt) is used. , Carbodiimides such as dicyclohexylcarbodiimide (DCC), BOP reagents such as O- (benzotriazol-1-yl) -N, N, N ′, N′-tetramethyluronium tetrafluoroborate (TBTU), and Those selected from the group consisting of O- (7-azabenzotriazol-1-yl) -N, N, N ′, N′-tetramethyluronium hexafluorophosphate (HATU) and the like can be used. Among these, it is preferable to use HATU from the viewpoint of easy handling and safety. The content of the condensing agent is not particularly limited as long as it is an amount generally used in the art, but for example, 1 mol to 1.5 mol with respect to 1 mol of a desired carboxylic acid for forming an amide bond. Preferably there is.

  The solvent is not particularly limited as long as it is soluble in the contents of the surface modification solution 50 such as a protein and a condensing agent and does not inhibit the amide bond formation reaction. For example, dimethylformamide (DMF) Or tetrahydrofuran (THF) etc. can be used. Among these, in order to suppress hydrolysis of the amide, it is preferable to use a dehydrated one. Furthermore, it is preferable to use dehydrated DMF from the viewpoint of excellent solubility. The amount of the solvent used in the surface modification solution 50 may be appropriately set according to the amount of carbon nanostructure 52 to be dispersed.

  The surface modification solution 50 preferably contains a base as necessary. The base is not particularly limited as long as it is generally used for making the reaction system in a basic condition in peptide synthesis, and N, N-diisopropylethylamine (DIEA) or the like can be used. Among these, it is preferable to use DIEA having a bulky substituent and low nucleophilicity from the viewpoint that the condensation reaction can proceed smoothly while suppressing the occurrence of side reactions. As described above, since the surface modification solution 50 further includes a base for making the surface modification solution 50 into a basic condition, the amide bond formation reaction can be further promoted. Nanostructures can be made even more easily. The content of the base is not particularly limited as long as it is an amount generally used in the art. For example, the content of the base is 10 mol to 1 mol with respect to 1 mol of an amino group introduced to the carbon nanotube as the carbon nanostructure. It is preferably 13 mol.

  In this production example, the carbon nanostructure has an amino group or carboxylic acid for forming an amide bond with the carboxylic acid or amino group of the protein. That is, the amide bond is formed by the condensation of the carboxylic acid that the protein has and the amino group that the carbon nanostructure has, or the amino group that the protein has and the carboxylic acid that the carbon nanostructure has. Therefore, when the carbon nanostructure has an amino group, all amino groups of the protein and carboxylic acids other than the desired carboxylic acid for forming an amide bond are protected with a protecting group before the condensation reaction. It is preferred that In addition, when the carbon nanostructure has a carboxylic acid, all carboxylic acids in the protein and amino groups other than the desired amino group for forming an amide bond are protected by a protecting group before the condensation reaction. It is preferred that

  The amino-protecting group is not particularly limited as long as it is generally used in the art, and examples thereof include a t-butoxycarbonyl (Boc) group, a 9-fluorenylmethyloxycarbonyl (Fmoc) group, A benzyloxycarbonyl (Cbz) group or an allyloxycarbonyl (Aloc) group can be used. Among these, it is preferable to use a t-butoxycarbonyl (Boc) group because it can be easily deprotected with trifluoroacetic acid or the like. The protecting group for the carboxylic acid is not particularly limited as long as it is generally used in the art, and for example, a benzyl ester (Bzl) group, an alkynylmethyl group, or a t-butyl ester group can be used. . These protective groups are preferably appropriately deprotected under the corresponding deprotection conditions after the desired amide bond is formed.

  The amino group or carboxylic acid may be introduced directly to the surface of the carbon nanostructure, or may be introduced via, for example, an alkylene group such as an ethylene group. The method for introducing an amino group or carboxylic acid into the carbon nanostructure is not particularly limited as long as it is a method generally used in the art. For example, when introducing a carboxylic acid, there is a method of irradiating ultrasonic waves after putting a carbon nanostructure in a mixed acid of sulfuric acid: nitric acid = 3: 1. In the case of introducing an amino group, for example, the carboxylic acid introduced on the surface of the carbon nanostructure is converted into an alcohol by reduction with a reducing agent such as lithium aluminum hydride (LAH), and further, diethylazodi Under the Mitsunobu reaction conditions using carboxylate (DEAD), triphenylphosphine and the like, there is a method in which the obtained alcohol is converted to phthalimide and then hydrolyzed with trifluoroacetic acid or the like. In the case of introducing an amino group through an alkylene group or the like, there is a method in which an amide bond is formed by condensing a carboxylic acid introduced on the surface of a carbon nanostructure and an alkylene diamine using a condensing agent. Whether or not an amino group or a carboxylic acid has been introduced into the carbon nanostructure is confirmed by X-ray photoelectron spectroscopy (XPS (X-ray photoelectron spectroscopy)), an XPS spectrum, and infrared spectroscopy ( It can be performed based on whether or not a peak derived from an amino group or a peak derived from a carboxylic acid can be confirmed in an IR spectrum or the like obtained by IR (Infrared spectroscopy).

  In the second step, the frequency of the ultrasonic wave 54 to be irradiated may be appropriately set to such an extent that the amide bond formation reaction can be promoted, but is preferably 40 kHz to 60 kHz. The time for irradiating the ultrasonic wave 54 is not particularly limited as long as the surface modification by the protein is reliably performed, that is, the time when the formation reaction of the amide bond is surely completed. Preferably there is. Irradiation of the ultrasonic wave 54 uses an ultrasonic generator such as a generally used ultrasonic cleaner (for example, a commercially available product (trade name: Sure Ultrasonic Cleaner CS-20, manufactured by Ishizaki Electric Co., Ltd.)). Can be done.

The surface-modified carbon nanostructure produced as described above is preferably taken out of the reaction system, washed with a washing solvent, and further dried under reduced pressure for a certain time. The cleaning solvent is not particularly limited as long as it can remove the contents of the surface modification solution 50 and the like. For example, diethyl ether, methanol, or a mixed solvent thereof can be used. The decompression condition is not particularly limited as long as the solvent for cleaning and the like can be completely removed, but is 1.0 × 10 ⁻⁶ MPa to 1.0 × 10 ⁻⁵ MPa for 1 hour to 3 hours. It is preferable to dry.

  As described above, in the example of the method for manufacturing the chemical substance detection unit 42, the surface-modified carbon nanostructure is manufactured by the ultrasonic modification method through the first step and the second step. That is, in the first step, a solution for surface modification comprising the above-mentioned protein that selectively reacts with a specific substance, a condensing agent for condensing a carboxylic acid and an amino group to form an amide bond, and a solvent. 50, and in the second step, after the carbon nanostructure 52 having an amino group or carboxylic acid for forming an amide bond is introduced into the prepared surface modification solution 50, the ultrasonic wave 54 is irradiated. To do. Thus, since the carbon nanostructure 52 having an amino group or a carboxylic acid can be uniformly dispersed in the surface modification solution 50 by using the ultrasonic wave 54, the surface of the carbon nanostructure 52 is made more uniform by the protein. Can be modified. Therefore, it is possible to manufacture the chemical substance detection element 32 that can detect a specific substance with higher selectivity and sensitivity. Further, since the surface of the protein is modified to the carbon nanostructure 52 by an amide bond, the protein can be firmly fixed on the surface of the carbon nanostructure 52. Therefore, the chemical substance detection element 32 that can maintain high selectivity and high sensitivity over a long period of time can be manufactured.

  Referring to FIGS. 3C and 3D, in the third step, a sheet-like substrate 56 including the surface-modified carbon nanostructures produced by the first step and the second step is produced. To do. This third step preferably includes a step of preparing a dispersion 58 in which the surface-modified carbon nanostructures are dispersed and a step of filtering the dispersion 58.

  The dispersion solvent for dispersing the surface-modified carbon nanostructure in the dispersion liquid 58 is not particularly limited as long as the surface-modified carbon nanostructure can be dispersed. For example, water, methanol, ethanol or Dimethylformamide (DMF) or the like can be used. Among these, water is particularly preferable from the viewpoint of safety and cost. By dispersing the surface-modified carbon nanostructure using such a dispersion solvent, the substrate 56 including the carbon nanostructure that has been uniformly surface-modified can be formed with a uniform thickness. When a solvent in which the surface-modified carbon nanostructure is difficult to disperse is used as a solvent for dispersion, the surface-modified carbon nanostructure is locally aggregated, so that there is a possibility that the substrate 56 having a uniform thickness may not be formed. The amount of the dispersion solvent used in the dispersion 58 may be appropriately set according to the amount of the surface-modified carbon nanostructure to be dispersed.

  The filter medium 60 used for the filtration is not particularly limited as long as it has insulating properties and appropriate mechanical strength. However, a membrane filter or a silver membrane filter made of a polymer material such as a fluororesin is used. Glass fiber filter paper or filter paper can be used. Among these, it is particularly preferable to use a membrane filter made of Teflon (registered trademark) because of cost and ease of handling. As a filtration method, a general method such as reduced-pressure filtration or natural filtration can be used, but it is preferable to use reduced-pressure filtration from the viewpoint of a high filtration rate and easy formation of a substrate 56 having a uniform thickness. When natural filtration is used, since the filtration speed is slow, it may take a long time to form the substrate 56, and the substrate 56 with a uniform thickness may not be formed. The vacuum filtration is preferably performed using a vacuum filtration apparatus including a Buchner funnel 62 and a suction bottle (not shown), and more preferably after the dispersion liquid 58 is injected into the Buchner funnel 62. . When the dispersion 58 is injected after the pressure is reduced, there is a possibility that the base 56 having a thickness at the central portion larger than that of other portions may be formed. The substrate 56 manufactured as described above is preferably dried. The substrate 56 includes a substrate 48 and a chemical substance detection unit 42. In this case, the substrate 48 is a filter medium 60, and the chemical substance detection unit 42 is a filter material 64 remaining on the filter medium.

  As described above, in an example of the method for manufacturing the chemical substance detection unit 42, in the third step, the sheet-like substrate 56 including the surface-modified carbon nanostructure is manufactured. As a result, the surface-modified carbon nanostructure can be reacted with the specific substance in a uniform state, so that the chemical substance detection element 32 capable of detecting the specific substance with higher selectivity and sensitivity can be obtained. Can be manufactured. Furthermore, the substrate 56 including the surface-modified carbon nanostructure is prepared by preparing a dispersion 58 in which the surface-modified carbon nanostructure is dispersed and drying the dispersion 58 by vacuum filtration or the like. As a result, the substrate 56 including the carbon nanostructure with the surface modified uniformly can be formed in a uniform thickness and in a short time.

  The substrate 56 including the surface-modified carbon nanostructure produced in the third step is cut so as to have a desired shape such as a strip shape and a desired size as necessary. Thereafter, the electrode 44 and the electrode 46 are formed to have a desired inter-electrode distance by a known method such as a vapor deposition method or a method of applying a conductive paste on both ends of the surface of the chemical substance detection unit 42. The chemical substance detection element 32 according to the present embodiment can be manufactured.

-Operation-
With reference to FIG.1 and FIG.2, the chemical substance detection apparatus 20 which concerns on this Embodiment operate | moves as follows. A measurement target gas containing a specific substance is introduced to the surface of the chemical substance detection element 32 while a constant voltage is applied to both ends of the chemical substance detection element 32 and the load resistor 34 connected in series by the DC power source 30. When any substance in the measurement target gas adheres to the surface of the surface modified carbon nanostructure constituting the chemical substance detection unit 42 included in the chemical substance detection element 32, the electrical resistance between the electrodes 44 and 46 changes. The change is detected as a change in the output voltage of the amplifier 36 by a DC voltmeter (not shown). By knowing the change in output voltage in this way, the presence of some substance in the measurement target gas can be confirmed.

  This is for the following reason. In the chemical substance detection unit 42, since the individual carbon nanostructures are adjacent to each other and are in contact with each other, the whole is a collection of conductive materials. When any substance adheres to the surface of each individual carbon nanostructure constituting the chemical substance detection unit 42, the electric resistance changes, and the sum of them changes as an output voltage change. Therefore, by knowing the change in the electrical resistance at both ends of the chemical substance detection unit 42, it can be seen that some substance has adhered to the chemical substance detection unit 42, so that it is confirmed that some substance exists in the measurement target gas. Can do.

  FIG. 4 is a view showing a state in which nitric oxide (NO) 76 is adsorbed on the surface of the carbon nanostructure 74 whose surface is modified by nitrile hydratase (NHase) 72. Referring to FIG. 4, nitric oxide (NO) 76 approaches carbon nanostructure 74 surface-modified by nitrile hydratase (NHase) 72, which is a protein that selectively reacts with nitric oxide (NO) 76. Then, the nitric oxide (NO) 76 is selectively held in the active center 78 of the nitrile hydratase (NHase) 72 by the selectivity by the nitrile hydratase (NHase) 72. Thus, since the nitrile hydratase (NHase) 72 surface-modified on the carbon nanostructure 74 selectively captures nitric oxide (NO) 76, when the nitric oxide (NO) 76 is retained. The difference between when it is not and when it is not so remarkably appears as a change in the overall electrical resistance of the chemical substance detection unit 42. Therefore, by measuring the change in the electrical resistance of the chemical substance detection unit 42, the presence or absence of the specific substance, nitric oxide (NO) 76, and the amount thereof are more sensitive than other substances. Can be detected.

<Action and effect>
According to the present embodiment, the chemical substance detection element 32 includes a carbon nanostructure that is surface-modified with a protein that selectively reacts with a specific substance. Thereby, a specific substance can be detected with high selectivity and high sensitivity. In addition, since the specific substance can be directly detected without being converted into another substance, it is possible to omit the configuration and process required for the conversion and the configuration and process required for the pretreatment accompanying the conversion. Therefore, the chemical substance detection element 32 can be downsized and the measurement time can be shortened.

  Further, according to the present embodiment, the chemical substance detection device 20 is electrically connected to the chemical substance detection element 32 and the chemical substance detection element 32, and detects a change in the electrical resistance of the chemical substance detection element 32. An amplifier 36 and a DC voltmeter are included. Thus, since the chemical substance detection apparatus 20 includes the chemical substance detection element 32, the specific substance can be detected with high selectivity and high sensitivity, and further downsizing of the apparatus and shortening of the measurement time can be achieved.

  Further, according to the present embodiment, an example of a method for producing the chemical substance detection element 32 is a condensation for forming an amide bond by condensing a protein that selectively reacts with a specific substance, a carboxylic acid, and an amino group. A first step of preparing a surface modification solution 50 containing an agent and a solvent, and a carbon nanostructure 52 having an amino group or a carboxylic acid for forming an amide bond is added to the surface modification solution 50 After that, a second step of irradiating the ultrasonic wave 54 is included, thereby producing a surface-modified carbon nanostructure. Thus, since the carbon nanostructure 52 having an amino group or a carboxylic acid can be uniformly dispersed in the surface modification solution 50 by using the ultrasonic wave 54, the surface of the carbon nanostructure 52 is uniformly made with protein. Can be modified. Therefore, it is possible to manufacture the chemical substance detection element 32 that can detect a specific substance with higher selectivity and sensitivity. Further, since the surface of the protein is modified to the carbon nanostructure 52 by an amide bond, the protein can be firmly fixed on the surface of the carbon nanostructure 52. Therefore, the chemical substance detection element 32 that can maintain high selectivity and high sensitivity over a long period of time can be manufactured.

  In the above embodiment, an example of the method for manufacturing the chemical substance detection element 32 has been described. However, the present invention is not limited to such an embodiment. For example, as another example of the manufacturing method of the chemical substance detection element 32, in the first step, a surface modification solution containing a protein that selectively reacts with a specific substance and a solvent is prepared, and in the second step, the preparation is performed. The surface modification solution is charged with a carbon nanostructure having an amino group or carboxylic acid for forming an amide bond, and a condensing agent for condensing the carboxylic acid and the amino group to form an amide bond. Then, the surface-modified carbon nanostructure may be produced by irradiating ultrasonic waves. Further, in the second step, a configuration may be employed in which stirring is performed without performing ultrasonic irradiation.

  Moreover, in the method for manufacturing the chemical substance detection element 32 in the above embodiment, the surface of the protein is modified to the carbon nanostructure 52 by an amide bond, but the present invention is not limited to such an embodiment. For example, the protein may be surface-modified by physically attaching to the carbon nanostructure 52. In such a case, as a manufacturing method of the chemical substance detection element 32, a spray method in which a coating solution containing a protein and a solvent is sprayed on an unmodified carbon nanostructure, an unmodified carbon nanostructure is used. A dipping method in which the carbon nanostructure is dipped after being immersed in the above-described coating solution, or an impregnation method in which an unmodified carbon nanostructure is immersed in the above-described coating solution can be used.

  Although the said embodiment is concretely demonstrated using an Example and a comparative example below, the said embodiment is not specifically limited to a present Example, unless the summary is exceeded. Unless otherwise specified, in the examples and comparative examples, an XPS spectrum is measured using an X-ray photoelectron spectrometer (trade name: MICRO LAB 300A, manufactured by VG SCIENTIFIC), and an IR spectrum is measured. Uses an infrared spectrophotometer (trade name: 20D FTIR SPECTROMETER, manufactured by Nicolet), and a resistance value measuring device (trade name: 3468A MULTITIMER, manufactured by Hewlett-Packard (hp)) is used for measuring the resistance value. used. Further, the amount of amino group introduced in the CNT having an amino group introduced on the surface (hereinafter referred to as “amino group-introduced CNT”) was measured by the picric acid test shown below.

[Picric acid test]
The dried amino group-introduced CNT is put into a dedicated container, and the added amino group-introduced CNT is 4 times with 2 ml of 5% dichloromethane solution of N, N-diisopropylethylamine (DIEA), 4 times with 2 ml of dichloromethane, and picric acid. An operation of washing 4 times with 2 ml of a 0.1 mol / L ethanol solution in this order was carried out in this order to prepare an amino group-introduced CNT picrate. The resulting picrate was further washed 4 times with 2 ml of dichloromethane to remove excess picric acid. The operation of washing 4 times with 2 ml of a 5% dichloromethane solution of DIEA and 4 times with 2 ml of dichloromethane was performed in this order on the picrate of amino group-introduced CNT after washing. Next, 16 ml of the washing solution containing DIEA picrate washed away was collected, and 1 ml of the washing solution was diluted 10-fold with 9 ml of ethanol to prepare a sample solution, and 1 ml of a 5% dichloromethane solution of DIEA and 1 ml of dichloromethane were prepared. A blank solution was prepared by diluting 1 ml of the mixed solution consisting of the above with 9 ml of ethanol.

Using the blank solution as a blank, the absorbance at 358 nm of the sample solution was measured with a spectrophotometer (trade name: Hitachi spectrophotometer U-3310, manufactured by Hitachi High-Technologies Corporation), and based on the following formula (1), The amino group introduction amount X (mol / g) was calculated.
X = (aVn) / (εwL) (1)
(A: absorbance, V: volume of washing solution (cm ³ ), n: dilution ratio, ε: molar extinction coefficient of picric acid (ε = 14500 cm ² mol ⁻¹ ), w: amino group-introduced CNT used in picric acid test Mass (g), L: cell length (cm))

[Manufacture of chemical substance detection elements]
(Example)
First, after introducing carboxylic acid on the surface of CNT which is a carbon nanostructure as follows, an amino group was introduced. After adding 5 mg of SWCNT (trade name: Single-wall nanotube, manufactured by Honjo Chemical Co., Ltd.) to a mixed acid composed of 1.5 mL of sulfuric acid and 0.5 mL of nitric acid, an ultrasonic cleaner (trade name: Sure ultrasonic cleaning) 46 kHz ultrasonic wave was irradiated for 5 hours with a device CS-20, manufactured by Ishizaki Electric Manufacturing Co., Ltd. After ultrasonic irradiation, the membrane was filtered using a Teflon (registered trademark) membrane filter (trade name: OMNIPORE ^™ MEMBRANE FILTERS 0.2 μm (pore size) JG, manufactured by MILLIPORE) using a vacuum filtration device, and the filtrate was collected. And dried to obtain a CNT having a carboxylic acid introduced on the surface (hereinafter referred to as “carboxylic acid-introduced CNT”). Subsequently, 2 mg of carboxylic acid-introduced CNT obtained as described above was added to 1 mL of ethylenediamine (trade name, manufactured by Wako Pure Chemical Industries, Ltd.), and then the ultrasonic wave of 46 kHz was applied using the ultrasonic cleaner described above. Irradiation was performed for 10 minutes, and dispersion of the carboxylic acid-introduced CNT in ethylenediamine was confirmed. After confirming the dispersion, 0.1 mg of HATU (condensing agent, manufactured by Sigma-Aldrich) was added, and ultrasonic waves were further irradiated for 4 hours. After irradiation with ultrasonic waves, the solution was diluted with methanol and filtered under reduced pressure using the above-mentioned Teflon (registered trademark) membrane filter, and the filtrate was washed with methanol to remove the remaining HATU. The washed filtrate was collected and air-dried, and then dried at 9.3 × 10 ⁻⁶ MPa under reduced pressure for 2 hours to obtain amino group-introduced CNT. In the obtained amino group-introduced CNT, in the XPS spectrum, an amino group-derived peak (404 eV) was confirmed in the N1s region, and a carboxylic acid-derived peak (533 eV) was confirmed in the O1s region. The IR spectrum (around 1570 cm ^-1, 3390 cm around ^-1) peak derived from the amino group reaffirmed confirmed the peak derived from the carbonyl group (1660 cm around ^-1). Moreover, the amino group introduction amount in the obtained amino group-introduced CNT was 0.30 mmol / g to 0.50 mmol / g.

Next, the surface modification of nitrile hydratase (NHase) on the carbon nanostructure CNT was performed as follows. Nitrile hydratase (NHase) 82.8 mg (1.8 μmol), HATU (condensing agent) 0.76 mg (2.0 μmol), DIEA (base) 1 with N-terminal and side chain amino groups protected by a Boc group 6 mg (12 μmol) was dissolved in 2 mL of dehydrated dimethylformamide (dehydrated DMF) to prepare a solution for surface modification. After 2 mg of amino group-introduced CNT obtained as described above was added to 2 mL of this surface modification solution, an ultrasonic cleaner (trade name: Sure Ultrasonic Cleaner CS-20, manufactured by Ishizaki Electric Co., Ltd.) The amide bond was generated by condensing the CNT amino group and NHase carboxylic acid by irradiating with 46 kHz ultrasonic waves for 2 hours. After deprotecting the Boc group by adding 0.5 mL of trifluoroacetic acid to the reaction system, CNTs were taken out from the reaction system. The extracted CNTs were washed with diethyl ether and methanol, and then dried at 9.3 × 10 ⁻⁶ MPa under reduced pressure for 2 hours, whereby nitrile hydratase (NHase) was surface-modified (hereinafter “surface-modified CNT”). Was obtained.)

  After preparing a dispersion in which the surface-modified CNT obtained as described above was dispersed in 5 mL of water, the dispersion was subjected to vacuum filtration with a vacuum filtration device using the above-mentioned Teflon (registered trademark) membrane filter. Then, a sheet-like substrate on which a filter made of surface-modified CNTs was formed on a membrane filter was produced, and dried. Next, the obtained substrate is cut into a strip shape, and gold electrodes are formed on both ends of the strip substrate by vapor deposition so that the distance between the electrodes is 1.5 cm. A substance detection element was produced.

(Comparative example)
A chemical substance detection element of a comparative example was produced in the same manner as in the example except that the surface modification with nitrile hydratase (NHase) was not performed.

[Evaluation]
The chemical substance detection device employing the chemical substance detection element of the example was installed in a 300 cm ³ stainless steel (SUS) chamber capable of controlling the atmosphere, and then the inside of the chamber was 6.65 using a diaphragm pump. The pressure was reduced to about × 10 ³ Pa. Next, nitrogen was circulated in the chamber until a atmospheric pressure (1.01325 × 10 ⁵ Pa) was reached while a current of 150 μA was applied to the chemical substance detection element by a direct current power source. Five minutes after the start of nitrogen circulation (after 300 seconds), a measurement target gas having a nitrogen monoxide (NO) concentration of 1 ppm was circulated at a flow rate of 50 mL / min for 10 minutes (600 seconds) while maintaining atmospheric pressure. The change in electrical resistance at the contact point between the chemical substance detection element and the load resistance at this time was amplified in an amplifier, and the amplified change in electrical resistance was measured as a change in the output voltage of the amplifier with a DC voltmeter. The measurement was performed at a measurement interval of 1 second for 20 minutes (1200 seconds) after the start of nitrogen flow. The same operation as described above was also performed for a chemical substance detection apparatus employing the chemical substance detection element of the comparative example. The result is shown in FIG. FIG. 5 is a graph showing a change in the resistance value of the chemical substance detection element with respect to the elapsed time. A is a graph showing the results of the example, and B is a graph showing the results of the comparative example.

  Referring to FIG. 5, the chemical substance detection apparatus employing the chemical substance detection element of the example includes a chemical substance detection unit composed of an aggregate of CNTs that are surface-modified with nitrile hydratase (NHase), and thus is unmodified. It can be seen that nitric oxide (NO) can be detected with higher sensitivity than the chemical substance detection device of the comparative example including the chemical substance detection unit made of the aggregate of CNTs.

  The embodiment disclosed herein is merely an example, and the present invention is not limited to the above-described embodiment. The scope of the present invention is indicated by each claim in the claims after taking into account the description of the detailed description of the invention, and all modifications within the meaning and scope equivalent to the wording described therein are included. Including.

It is a block diagram of the chemical substance detection apparatus containing the chemical substance detection element which concerns on one embodiment of this invention. It is the side view and top view which show the structure of a chemical substance detection element. It is a figure for demonstrating an example of the manufacturing method of a chemical substance detection part. It is a figure which shows a mode that nitric oxide adsorb | sucks to the carbon nanostructure surface modified by the nitrile hydratase. It is a graph which shows the change of the resistance value of the chemical substance detection element with respect to elapsed time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 20 Chemical substance detection apparatus 30 DC power supply 32 Chemical substance detection element 34 Load resistance 36 Amplifier 42 Chemical substance detection part 44,46 Electrode 48 Substrate 50 Surface modification solution 52 Carbon nanostructure 54 Ultrasonic wave 56 Base 58 Dispersion liquid 60 Filter medium 62 Buchner funnel 64 filtrate 72 nitrile hydratase 74 carbon nanostructure 76 nitric oxide 78 active center

Claims (12)

  A chemical substance detection element comprising a carbon nanostructure surface-modified with a protein that selectively reacts with a specific substance.   The chemical substance detection element according to claim 1, wherein the carbon nanostructure is made of a carbon-based conductive material selected from the group consisting of carbon nanotubes, carbon nanofibers, carbon nanohorns, and fullerenes.   3. The chemical substance detection according to claim 1, wherein the carbon nanostructure is surface-modified with 0.30 μmol to 0.50 μmol of the protein with respect to 1 mg of the carbon nanostructure. element. The carbon nanostructure has an amino group or carboxylic acid for forming an amide bond with the carboxylic acid or amino group of the protein,
4. The chemical substance detection element according to claim 1, wherein the protein is surface-modified to the carbon nanostructure by the amide bond. 5.   The chemical substance detection element according to any one of claims 1 to 4, wherein the specific substance is nitric oxide.   The chemical substance detection element according to claim 5, wherein the protein includes nitrile hydratase.   The chemical substance detection element according to claim 6, wherein the nitrile hydratase is an iron-type nitrile hydratase. The chemical substance detection element according to any one of claims 1 to 7,
A chemical substance detection apparatus, comprising: a detecting means which is electrically connected to the chemical substance detection element and detects a change in electric resistance of the chemical substance detection element. A first step of preparing a solution for surface modification comprising a protein that selectively reacts with a specific substance, a condensing agent for condensing a carboxylic acid and an amino group to form an amide bond, and a solvent;
A second step of irradiating the surface modification solution with ultrasonic waves after introducing a carbon nanostructure having an amino group or carboxylic acid for forming the amide bond;
The method for producing a chemical substance detection element, wherein the carbon nanostructure having a surface modified with the protein is produced by the first step and the second step.   10. The method for producing a chemical substance detection element according to claim 9, wherein in the first step, a surface modification solution further containing a base for making the surface modification solution into a basic condition is prepared.   The method for producing a chemical substance detection element according to claim 9 or 10, further comprising a third step of producing a sheet-like substrate including the carbon nanostructure surface-modified with the protein. .   The third step includes a step of preparing a dispersion in which the carbon nanostructures surface-modified with the protein are dispersed, and a step of filtering the dispersion. The manufacturing method of the chemical substance detection element of description.

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