JP6654320B2 - Antimicrobial agent and method for producing the same - Google Patents

Description

  The present invention relates to a hybrid antibacterial agent containing an inorganic antibacterial material and an organic antibacterial compound, and more particularly to a hybrid antibacterial agent containing silver clusters as an inorganic antibacterial material.

As antibacterial agents, inorganic antibacterial agents such as silver and organic antibacterial agents such as quaternary ammonium compounds and benzalkonium chloride are known (for example, Patent Documents 1 to 4). Inorganic antibacterial agents have the advantage that there are many types of effective bacteria, high heat resistance, and the ability to exhibit antibacterial properties over a long period of time. On the other hand, organic antibacterial agents have an immediate effect, and have the advantage of exhibiting antibacterial properties in a small amount.
Silver, which is an inorganic antibacterial agent, can be used in various forms such as silver ions, silver clusters, and silver nanoparticles (for example, Patent Literature 2 and Non-Patent Literature 1).

  BACKGROUND ART In medical products and daily necessities, resin products having antibacterial properties (antibacterial resin products) are widely used. These antibacterial resin products are manufactured by molding a resin material to which an antibacterial agent is added, or by applying a coating agent containing an antibacterial agent to the surface of the molded resin product. An antibacterial agent for an antibacterial resin product is dissolved in an organic solvent and added to a resin material or a coating agent.

  In recent years, antibacterial agents are also used for dissolving antibacterial agents in volatile organic solvents and spraying them onto clothing, etc., to deodorize clothing and suppress bacterial growth (so-called "deodorant antibacterial spray"). ing. Antibacterial agents for deodorizing antibacterial sprays are required to have antibacterial agents capable of realizing both an immediate-acting antibacterial that can immediately deodorize and a slow-acting antibacterial that can maintain antibacterial properties in the long term.

International Publication No. 2007/74484 WO 2001/41774 JP-A-2005-129149 JP-T-2013-536156A

Wang X et al, "Fluorescent Ag nanoclusters templated by carboxymethyl-β-cyclodextrin (CM-β-CD) and their in vitro antimicrobial activity", Mater. Sci. Eng. C Mater. Biol. Appl. (2013) 33, 656 -662

  Since the silver cluster has a very small particle size of 0.5 to 2.0 nm, the surface area per volume is large. Silver clusters also have active surface atoms with a unique electronic structure. From these characteristics, silver cluster is expected as an antibacterial agent having high antibacterial properties. For example, Non-Patent Document 1 discloses that water-soluble silver clusters are synthesized using carboxymethyl-β-cyclodextrin (CM-β-CD), and exhibit extremely high antibacterial properties.

However, water-soluble silver clusters do not dissolve in organic solvents and, as a result, cannot be added to resin materials or coatings. Therefore, antibacterial agents containing silver clusters could not be used as antibacterial agents for antibacterial resin products or antibacterial antibacterial sprays.
Further, since silver cluster is a slow-acting antibacterial agent, it does not satisfy the antibacterial performance required for an antibacterial agent for a deodorant antibacterial spray (capable of quick-acting antibacterial and slow-acting antibacterial).

  Accordingly, an object of the present invention is to provide an antibacterial agent that contains silver clusters, is soluble in an organic solvent, and has an antibacterial effect of immediate action and slow action, and a method for producing the same.

The antibacterial agent according to the present invention includes a silver cluster, a ligand bonded to the silver cluster, and an organic compound bonded to the ligand,
The ligand has a functional group containing a hetero atom and an acidic functional group,
The organic compound is an aliphatic amine having an alkyl group having ₄ to ₁₈ carbon atoms.

The aliphatic amine may include at least one selected from the group consisting of a primary amine, a secondary amine, a tertiary amine, and a quaternary ammonium salt. Specific examples of the aliphatic amine include hexylamine, octylamine, decylamine, dodecylamine, cyclohexylamine, 3- (N-ethylamino) -1-butanol, diphenylamine, N-ethylethanamine, and N-ethyl. At least one selected from the group consisting of -N-methylbutan-1-amine, N, N-dimethylmethanamine, tetraoctylammonium bromide, cetyltrimethylammonium bromide, benzalkonium chloride, cetylpyridinium chloride, benzethonium chloride and decalinium chloride One can be included.
It is particularly preferred that the aliphatic amine is a quaternary ammonium salt.

  The functional group containing a hetero atom of the ligand may include at least one selected from the group consisting of a thiol group, an amino group and a carboxyl group. Specific examples of the ligand include at least one selected from the group consisting of dihydrolipoic acid, glutathione, captopril, mercaptopropionic acid, mercaptohexanoic acid, mercaptooctanoic acid, mercaptoundecanoic acid, cysteine, methionine, and glutathione. be able to.

The production method of the antibacterial agent according to the present invention,
Synthesizing a silver cluster complex comprising a silver cluster and a ligand bonded to the silver cluster;
Reacting the silver cluster complex with an organic compound to bind the ligand and the organic compound,
The ligand has a functional group containing a hetero atom and an acidic functional group,
The organic compound is an aliphatic amine having an alkyl group having ₄ to ₁₈ carbon atoms.

The reacting step preferably includes stirring the aqueous solution containing the silver cluster and the organic solution containing the organic compound for 5 to 10 minutes.
After the reacting step, the method may further include a step of purifying the reactant.
The aliphatic amine may include at least one selected from the group consisting of a primary amine, a secondary amine, a tertiary amine, and a quaternary ammonium salt. It is particularly preferred that the aliphatic amine is a quaternary ammonium salt.
The functional group containing a hetero atom of the ligand may include at least one selected from the group consisting of a thiol group, an amino group and a carboxyl group.

The antibacterial agent of the present invention can make the silver cluster soluble in an organic solvent by complexing the silver cluster with an organic antibacterial compound. Further, according to the antibacterial agent of the present invention, it is possible to exhibit both immediate effect and slow effect antibacterial properties.
According to the production method of the present invention, the above-mentioned antibacterial agent can be produced efficiently.

FIG. 1 is an ESI-MS mass spectrum of the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ). FIG. 2 is a fluorescence spectrum of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ). FIG. 3 is an IR spectrum of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ). FIG. 4 is a structural formula of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ). FIG. 5A shows the UV-vis absorption spectrum of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ), and FIG. 5B shows the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) UV-vis. It is a vis absorption spectrum. FIG. 6A is a thermogravimetry (TG) curve of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ), and FIG. 6B is a silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ). It is a TG curve. Figure 7 shows the results of antibacterial test for Staphylococcus aureus hybrid antimicrobial agent _{(TOA-Ag 25 (DHLA)} 14). Figure 8 shows the results of antibacterial test for Klebsiella pneumoniae of hybrid antimicrobial agent _{(TOA-Ag 25 (DHLA)} 14). Figure 9 shows the results of antimicrobial comparative tests of the organic compound (TOAB) and hybrid antimicrobial agent _{(TOA-Ag 25 (DHLA)} 14).

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, a term indicating a specific direction or position (for example, “above”, “below”, “right”, “left”, and another term including those terms) is used as necessary. . The use of these terms is to facilitate understanding of the invention with reference to the drawings, and the technical scope of the present invention is not limited by the meaning of the terms. In addition, the same reference numeral in a plurality of drawings indicates the same part or member.

<First Embodiment>
The antibacterial agent of the present invention is an inorganic-organic hybrid antibacterial agent containing a silver cluster, a ligand bonded to the silver cluster (coordination bond), and an organic compound bonded to the ligand (hereinafter, referred to as an antibacterial agent). , The antibacterial agent of the present invention may be referred to as a “hybrid antibacterial agent”). The organic compound is an aliphatic amine containing an alkyl group having a carbon number of C ₄ -C _18, it is soluble in organic solvents. The silver cluster becomes soluble in an organic solvent by binding to the organic compound via a ligand. Accordingly, the hybrid antibacterial agent can be used as an antibacterial agent for a resin antibacterial product and as an antibacterial agent for a deodorant antibacterial spray.

  The aliphatic amine used as the organic compound in the present invention exhibits antibacterial properties by protonating the amine to form a cation. That is, the organic compound used in the present invention is an organic antibacterial compound and functions as an immediate-acting antibacterial agent. In the hybrid antibacterial agent, the silver cluster functions as a slow-acting antibacterial agent, and the organic compound functions as a fast-acting antibacterial agent. Therefore, the hybrid antibacterial agent of the present invention is suitable as an antibacterial agent for a deodorant antibacterial spray.

  The antibacterial agent of the present invention does not simply coexist with the silver cluster and the organic compound, but forms a composite of the silver cluster and the organic compound, that is, the binding of the silver cluster and the organic compound through a ligand, thereby stabilizing the silver cluster. (In particular, stability to light and stability to heat) are improved.

Silver clusters have low resistance to light, and when irradiated with visible light to violet rays, the silver clusters are decomposed. Therefore, when an antibacterial agent containing silver clusters is used in a product that is used in an environment where visible light to ultraviolet light is irradiated (construction materials placed outdoors, medical equipment that sterilizes by ultraviolet light, etc.), silver clusters in the antibacterial agent are decomposed. As a result, the original antibacterial performance could not be exhibited.
Further, the silver cluster has a low resistance to heat, and when heated, the silver cluster is easily thermally decomposed. Therefore, when the antibacterial resin product is used in an environment where the temperature is high (for example, 50 ° C. or higher), silver clusters in the antibacterial agent may be decomposed. Therefore, products using silver cluster-containing antibacterial agents in an environment of 50 ° C. or higher (for example, products placed in an environment where direct sunlight is irradiated (building materials placed outdoors, interiors of automobiles, etc.), heaters, etc.) When used in heating equipment housings and products used in the vicinity of heating equipment, medical equipment that is disinfected by boiling, etc.), silver clusters in the antibacterial agent may be decomposed and the original antibacterial performance may not be exhibited. there were.

  However, when the silver cluster is combined with the organic compound, the light resistance and heat resistance of the silver cluster are improved. Therefore, decomposition of silver clusters is suppressed even when used in a product used in an environment where visible light to ultraviolet light is irradiated, a product used in an environment where the temperature is 50 ° C. or higher, and the antibacterial resin product has an advantage in that the silver cluster is not used. Can exhibit antibacterial performance.

  Further, the antibacterial agent of the present invention can exhibit sufficient antibacterial performance at a lower concentration than conventional antibacterial agents (organic antibacterial agents and inorganic antibacterial agents). Thereby, sufficient antibacterial properties can be obtained while reducing the amount of the antibacterial agent to be used.

  Hereinafter, the hybrid antibacterial agent of the present invention will be described in detail.

(Silver cluster)
Silver clusters are inorganic antibacterial agents, and their antibacterial properties are slow-acting. Silver clusters exhibit antimicrobial properties against many bacteria such as bacteria, molds, and yeasts.
The term “silver cluster (Ag cluster)” as used herein refers to an aggregate composed of silver atoms (Ag (O)) and / or silver ions (Ag (I)), and the number of silver atoms and silver ions Is 200 or less and the particle size is 0.5 to 2.0 nm. The silver cluster includes one composed only of silver atoms, one composed only of silver ions, and one composed of a mixture of silver atoms and silver ions.

Silver clusters can be distinguished from other forms of silver (eg, silver nanoparticles and silver ions) by UV-Vis absorption spectra. In the UV-Vis absorption spectrum of the silver cluster, a plurality of absorption peaks are observed at 300 to 800 nm. On the other hand, in the UV-Vis absorption spectrum of silver nanoparticles, only one plasmon absorption peak is observed at 400 to 500 nm, and no plasmon absorption peak is observed for silver ions.
In many silver clusters, light emission (PL) is observed by irradiation with ultraviolet light. In many cases, the PL can be distinguished from silver nanoparticles and silver ions by observing the PL.

  Since silver clusters are much smaller than silver nanoparticles (3-100 nm), silver clusters have a larger surface area per volume than silver nanoparticles. In addition, the surface of the silver cluster has active surface atoms having a unique electronic structure. Therefore, it is expected to exhibit higher antibacterial properties than silver nanoparticles. Antibacterial agents containing silver clusters have an antibacterial effect on more types of bacteria than antibacterial agents containing silver nanoparticles, and against the same bacteria (eg, Escherichia coli (gram negative) and Staphylococcus aureus (gram positive)). And has a higher antibacterial effect. In particular, antibacterial agents containing silver clusters have antibacterial properties against multiple multidrug-resistant bacteria.

  In a plurality of silver clusters, the number of atoms of one silver cluster and the number of atoms of another silver cluster may be the same or different. Since the number of atoms of a silver cluster stabilized under a predetermined condition is substantially constant, a plurality of silver clusters having a substantially constant number of atoms can be obtained by performing a process of stabilizing the silver cluster in the manufacturing process.

(Organic compound)
The organic compound used for the hybrid antibacterial agent is an aliphatic amine containing an alkyl group having C _{4 to} C ₁₈ (hereinafter, the organic compound of the present invention may be simply referred to as “aliphatic amine”). Aliphatic amines exhibit antimicrobial properties by protonating the amine to form a cation.
The aliphatic amine used in the present invention contains an alkyl group having ₄ to ₁₈ carbon atoms in the alkyl group. Therefore, it shows hydrophobicity and is soluble in organic solvents such as methanol, ethanol, toluene, acetone, THF, and acetonitrile. When the aliphatic amine binds to the hydrophilic silver cluster complex, the silver cluster complex becomes hydrophobic and becomes soluble in an organic solvent.

As used herein, the term "aliphatic amine" refers to a primary amine (one alkyl group and two hydrogen atoms (H) bonded to a nitrogen atom (N)), a secondary amine (two alkyl groups to N). One H is bonded), a tertiary amine (N has three alkyl groups bonded) and a quaternary ammonium salt (A quaternary ammonium cation having four alkyl groups bonded to N, and an anion such as H ⁺ Salt).

Secondary amines, tertiary amines and quaternary ammonium salts contain multiple alkyl groups. The aliphatic amines of the present invention, at least one of the plurality of alkyl groups, an alkyl group having a carbon number of C ₄ -C _18. More preferably, all of the plurality of alkyl groups are alkyl group having a carbon number of C ₄ -C _18. In addition, the said alkyl group may be linear or cyclic, and may have a side chain.

As primary amines, for example, hexylamine, octylamine, decylamine, dodecylamine and cyclohexylamine can be used.
As the secondary amine, for example, 3- (N-ethylamino) -1-butanol, diphenylamine and N-ethylethanamine can be used.
As the tertiary amine, for example, N-ethyl-N-methylbutan-1-amine and N, N-dimethylmethanamine can be used.
As the quaternary ammonium salt, for example, tetraoctylammonium bromide (TOAB), cetyltrimethylammonium bromide, benzalkonium chloride, cetylpyridinium chloride, benzethonium chloride and decalinium chloride can be used.

  As the aliphatic amine of the present invention, a quaternary ammonium salt is particularly preferred. Since the quaternary ammonium salt is a strong electrolyte, it is always positively charged. Therefore, when reacting the ligand with the aliphatic amine, the reactivity with the acidic functional group of the ligand is high. Therefore, the reaction between the ligand and the aliphatic amine is promoted, the reaction time (stirring time) can be shortened, and the yield of the hybrid antibacterial agent can be increased.

As the ligand coordinated to the silver cluster, one having a functional group containing a hetero atom and an acidic functional group is used.
As used herein, the term "heteroatom" refers to an atom excluding carbon and hydrogen. The “functional group containing a hetero atom” includes, for example, a thiol group (—SH), an amino group (—NH ₂ ), and a carboxyl group (—COOH). Particularly, a thiol group is preferable. Functional groups containing heteroatoms can coordinate to silver clusters.

In the present specification, the “acidic functional group” is a functional group having acidity and reacts with an amine. The acidic functional group can form an ionic bond by reacting with an organic compound (specifically, an aliphatic amine) used in the hybrid antibacterial agent. Acidic functional groups include, for example, carboxyl groups (—COOH), phosphate groups (H ₂ PO ₄ ⁻ ), and sulfate groups (HSO ₄ ⁻ ). Particularly, a carboxyl group is preferable.

  The ligand used in the hybrid antibacterial agent contains a functional group that coordinates with the silver cluster (functional group containing a hetero atom) and a functional group that reacts with the aliphatic amine (acidic functional group). The silver cluster and the aliphatic amine can be bonded (complexed) via a ligand.

`` Ligand having a heteroatom-containing functional group and an acidic functional group '' is dihydrolipoic acid (DHLA), glutathione, captopril, mercaptopropionic acid (MPA), mercaptohexanoic acid (MHA), mercaptooctanoic acid ( MOA), mercaptoundecanoic acid (MUA), cysteine, methionine, glutathione, polymethacrylic acid and polyacrylic acid. Particularly, dihydrolipoic acid (a compound containing a thiol group and a carboxyl group) is preferable.
When a plurality of ligands can coordinate with one silver cluster, the plurality of ligands may include only one kind of ligand, or may include a plurality of kinds of ligands. It may contain a ligand. From the viewpoint of ease of production, a silver cluster complex containing only one kind of ligand is preferable.
In a plurality of silver cluster complexes, the ligand contained in one silver cluster complex and the ligand contained in another silver cluster complex are all the same, partially different, or completely different. May be different.

  Next, a method for producing a hybrid antibacterial agent will be described.

<Step 1. Synthesis of Silver Cluster Complex>
A silver compound aqueous solution containing silver ions is added to an aqueous solution containing a ligand (protecting agent), and a reducing agent is further added, followed by stirring for 1 to 10 hours. The stirring is preferably performed under light shielding. In addition, a stirrer such as a magnet stirrer can be used for stirring. Silver ions in the aqueous solution are reduced by a reducing agent to generate silver atoms. A plurality (for example, 15 to 40) of silver atoms aggregate to form a silver cluster. The ligand in the aqueous solution coordinates with the silver cluster to obtain a silver cluster complex.

As a specific example, the synthesis of a silver cluster complex using dihydrolipoic acid (DHLA) as a ligand will be described. A reducing agent (for example, an aqueous solution of sodium borohydride (NaBH ₄ )) is added to the aqueous solution of α-lipoic acid and stirred for 10 to 60 minutes to obtain an aqueous solution of dihydrolipoic acid (corresponding to “an aqueous solution containing a ligand”). An aqueous silver nitrate (AgNO ₃ ) solution (corresponding to “aqueous silver compound solution containing silver ions”) is added thereto, and a reducing agent (for example, an aqueous NaBH ₄ solution) is further added thereto, followed by stirring for about 1 to 10 hours. The color of the solution is opaque black before stirring, but becomes transparent orange when stirring is completed. Such a change in color makes it possible to visually recognize the formation of the silver cluster complex.

<Step 2. Reaction of silver cluster complex with organic compound (aliphatic amine)>
An organic solution is prepared by dissolving an aliphatic amine containing an alkyl group having ₄ to ₁₈ carbon atoms in an organic solvent (for example, toluene). Step 1. The organic solution is added to the silver cluster complex aqueous solution obtained in the above, and the mixture is stirred for 5 to 10 minutes. As a result, the silver cluster complex reacts with the aliphatic amine (more precisely, the ligand of the silver cluster complex reacts with the aliphatic amine) to produce a hybrid antibacterial agent. Stirring can be performed by shaking firmly by hand or stirring with a vortex mixer in a state of being sealed in a closed container.

If the stirring is not sufficient, the silver cluster complex and the aliphatic amine do not sufficiently react, and a hybrid antibacterial agent cannot be obtained. Therefore, when stirring, it is important to stir vigorously for a sufficient time. Even when the silver cluster complex and the aliphatic amine coexist, it is not easy for the hydrophilic silver cluster complex and the hydrophobic aliphatic amine to approach each other, and the reaction hardly proceeds spontaneously.
Usually, the silver cluster complex is orange or the like. As the reaction proceeds, the silver cluster complex in the aqueous layer reacts with the aliphatic amine to become a hybrid antibacterial agent and moves to the organic layer, so that the organic layer is colored and the color of the aqueous layer is lightened. Thus, by visually checking the colors of the aqueous layer and the organic layer, it can be confirmed that the reaction is in progress.

  The stirred solution is allowed to stand to separate into an aqueous layer (lower layer) and an organic layer (upper layer). Since the hybrid antibacterial agent is dissolved in the organic solvent, it exists in the organic layer. Then, the organic layer (upper layer) is separated to obtain an organic solution containing the hybrid antibacterial agent.

<Step 3. Removal of unreacted compounds>
Step 3. Then, step 2. Is subjected to a purification step. Step 3. May be omitted.
Step 2. The organic layer obtained in may contain an unreacted compound in addition to the hybrid antibacterial agent. For example, when a silver cluster complex is reacted with an aliphatic amine, one of them may become excessive. If the silver cluster complex is excessive with respect to the aliphatic amine, the unreacted silver cluster complex exists in the solution. If there is an excess of the aliphatic amine relative to the silver cluster complex, there will be unreacted aliphatic amine in the solution.
Step 2. Then, the stirred solution is allowed to stand and separated into an aqueous layer (lower layer) and an organic layer (upper layer), and the organic layer is separated. As described above, since the hybrid antibacterial agent is dissolved in the organic solvent, it exists in the organic layer. On the other hand, the unreacted silver cluster complex is water-soluble and therefore exists in the aqueous layer. The unreacted aliphatic amine was dissolved in the organic solvent, but it was found that most of the unreacted aliphatic amine was present in a suspended state in the aqueous layer when left standing after stirring. Therefore, step 2. By simply separating the organic layer by the above, most of the unreacted compounds can be removed from the organic layer.

However, some unreacted compounds (particularly, aliphatic amines soluble in organic solvents) can remain in the organic layer together with the hybrid antibacterial agent. Therefore, in order to increase the purity of the finally obtained hybrid antibacterial agent, a purification operation for removing unreacted compounds from the separated organic layer may be performed. The purification operation can be performed as follows.
Pure water is added to the separated organic layer, and the mixture is stirred for 1 to 10 minutes. The stirring can be performed by shaking with a hand or the like in a state of being sealed in a closed container. Thereby, the unreacted compounds remaining in the organic layer are moved to the aqueous layer. An unreacted compound can be extracted from the organic layer by repeating a series of operations (purification operation) of addition of pure water, stirring, standing, and separation of the organic layer a plurality of times (for example, 2 to 10 times).

  From the viewpoint of obtaining a high-purity hybrid antibacterial agent, the above-described purification operation is preferably performed repeatedly (for example, 5 to 10 times) until the aqueous layer becomes colorless and transparent. On the other hand, from the viewpoint of the production cost of the hybrid antibacterial agent, the purification operation is performed after adjusting the ratio of the silver cluster complex and the aliphatic amine so that no unreacted compound is generated or the unreacted compound is reduced. Is preferably performed several times (for example, 1 to 3 times).

<Step 4. Removal of organic solvent>
Step 3. The organic solvent is removed from the organic layer (in the case where step 3 is omitted, the organic layer obtained in step 2) after the purification operation is performed to obtain a hybrid antibacterial agent. A vacuum dryer (evaporator) may be used for removing the organic solvent.

  The hybrid antibacterial agent thus obtained has a high antibacterial property, and also exhibits an immediate antibacterial property peculiar to an organic antibacterial agent and a delayed antibacterial property peculiar to an inorganic antibacterial agent. Further, the hybrid antibacterial agent is soluble in an organic solvent despite containing silver clusters, and thus can be widely used in antibacterial resin products. Further, since the photostability of the silver cluster is improved by combining the silver cluster with the organic compound, the silver cluster can be used as an antibacterial agent in products placed in an environment where light can be irradiated.

(Synthesis of hybrid antibacterial agent)
Hybrid antimicrobial agent _{(TOA-Ag 25 (DHLA)} 14) was synthesized by the following procedure.
(1) Synthesis of silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) To a brown screw tube, 19 mg (9.2 × 10 ⁻⁵ mol) of α-lipoic acid was added to 13 mL of pure water (sample A). Further, a solution of 6.8 mg of NaBH ₄ (1.8 × 10 ⁻⁴ mol) dissolved in 1 mL of pure water was added to Sample A, and α-lipoic acid was reduced to dihydrolipoic acid (DHLA) (Sample B). To Sample B, a solution of 3.0 mg of AgNO ₃ (1.8 × 10 ⁻⁵ mol) dissolved in 700 μL of pure water was added (Sample C). In sample C, 9.8 mg of NaBH ₄ (2.6 × 10 ⁻⁴ mol) was dissolved in 2 mL of pure water, the solution was added, and the mixture was stirred for several minutes. The solution immediately turned from colorless and transparent to black and polydisperse silver clusters formed. When the sample solution was further stirred for 4 hours, the solution turned from black to orange, and an aqueous solution of the silver cluster complex was obtained. The mass spectrum measurement revealed that the silver cluster was a 25-mer, that is, a cluster containing 25 silver atoms (hereinafter, the 25-mer silver cluster used in the examples is simply referred to as “Ag ₂₅ ”). May be written). In addition, as a result of mass spectrometry, it was found that 14 dihydrolipoic acids (DHLA) coordinated with the silver cluster (hereinafter, the silver cluster complex is referred to as “Ag ₂₅ (DHLA) ₁₄ ”). is there).

(2) Purification of silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) 16.7 mL of the synthesized aqueous solution of silver cluster complex was transferred to a 50 mL centrifuge tube, and 16 mL of 1-butanol and 4 mL of methanol were added thereto and shaken well. . By this operation, 1-butanol was gradually dissolved in methanol, and the aqueous solution of the silver cluster complex was concentrated. Centrifugation was performed at 6,000 rpm for 5 minutes using a KUBOTA table top centrifuge 4200. The upper layer was a colorless and transparent solution, and the lower layer was a brown solution containing a silver cluster complex. The colorless and transparent solution in the upper layer was removed with a pasteur, and 12 mL of 1-butanol was added thereto, shaken thoroughly, and centrifuged again under the same conditions. This operation was repeated until the brown portion became solid. The colorless and transparent solution in the upper layer was removed with a pasteur, and 2 mL of methanol was added and dissolved with a SANSYO D-SONIC ultrasonic cleaner. This was transferred to a 1.5 mL microtube in 1 mL portions. 200 μL of methanol was put into the centrifuge tube to wash the centrifuge tube, and the solution was added to the above-mentioned microtube by 100 μL each. The microtube containing the silver cluster complex was centrifuged at 14800 rpm for 10 minutes using a SIGMA micromini centrifuge. This supernatant solution was transferred to another 1.5 mL microtube, and dried under reduced pressure at normal temperature using an Isotemp vacuum oven Model 280A (manufactured by ThermoFisher Sientific) to solidify. Thereafter, 500 μL of ethanol was added to the solid sample to perform ultrasonic dispersion, and the mixture was dispersed and centrifuged at 14,800 rpm for 5 minutes using a micromini centrifuge to remove the supernatant. This operation was performed once again, and dried under reduced pressure at room temperature using a reduced pressure drier to obtain solid Ag ₂₅ (DHLA) ₁₄ . This sample was stored in the freezer. Approximately 4 mg of solid sample was obtained in the single synthesis described above.

(3) Synthesis of hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ )
In a 30 mL screw tube, 4 mg of Ag ₂₅ (DHLA) ₁₄ was dissolved in 10 mL of pure water (sample D). Also, in another 30 mL screw tube, 1.17 mg, 5.45 mg of tetraoctyl ammonium bromide (TOAB) (TOAB to Ag ₂₅ (DHLA) ₁₄ and molar ratio M (TOAB) / M (Ag ₂₅ (DHLA) ₁₄ ) = amount. here equivalent to 3.14, M (TOAB) is the number of moles of TOAB, were M a (Ag ₂₅ (DHLA) ₁₄₎ is the number of moles of Ag ₂₅ (DHLA) ₁₄₎ was dissolved in 5 mL of toluene . This TOAB toluene solution was added to a screw tube containing 10 mL of the silver cluster complex aqueous solution (sample D), and vigorously shaken with a vortex mixer for about 2 minutes. Silver cluster complex Ag ₂₅ (DHLA) ₁₄ reacted with TOAB to form a hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ). Since the hybrid antibacterial agent was soluble in an organic solvent, it was dissolved in the toluene layer. When the hybrid antibacterial agent dissolves in the toluene layer, the color of the toluene layer becomes visible and can be visually recognized. After standing and separating into an upper layer (toluene layer) and a lower layer (aqueous layer), the toluene layer was separated. To remove impurities (for example, unreacted compounds) in the toluene layer, 15 mL of pure water was added to the separated toluene layer, and the mixture was shaken by hand. After standing and separating into an upper layer (toluene layer) and a lower layer (aqueous layer), the toluene layer was separated. Note that water droplets are dispersed in the toluene layer to form an emulsion. In order to separate water droplets from the toluene layer, the fractionated upper toluene layer was separated into 1.5 mL microtubes, each 1 mL, and centrifuged at 14,800 rpm for 10 minutes using a micromini centrifuge. Then, the TOA-Ag ₂₅ (DHLA) ₁₄ solution was obtained by separating the upper layer (toluene layer).

(Mass spectrum measurement of silver cluster complex)
The silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) synthesized in Example 1 was measured with a mass spectrum to determine the number of atoms of the silver cluster and the number of ligands bonded to one silver cluster.
A solid sample of the silver cluster complex obtained in Example 1 (2) was dissolved in methanol to prepare a 1 mg / mL methanol solution of the silver cluster complex. The sample was measured in an ESI negative ion mode using an orbitrap mass spectrometer Exactive (manufactured by ThermoFisher Sientific). The spray voltage was -4 to -5 kV, and the capillary temperature was 250 ° C. The sample was introduced by infusion, and the sample introduction speed was 2.5 μL / min.

FIG. 1 shows an ESI-MS mass spectrum of the silver cluster complex. Peaks were found at m / z 1896.9, 1813.6 and 1422.4. 1896.9 and 1813.6 were detected as trivalent ions, and 1422.4 was detected as tetravalent ions. 1896.9 is the main peak. Here, DHLA, which is a ligand of a silver cluster, obtained by removing two Hs (composition formula C ₈ H ₁₄ O ₂ S ₂ ) is referred to as “L”. The peak interval is 7.3 with respect to the peak of the trivalent ion. This indicates that the mass (m) of the silver cluster is 7.3 (m / z) × 3 (z) = 21.9 ≒ 22. This was considered to be multiple peaks in which L was replaced with Na. L is represented by L _(H), and L-substituted L is represented by L _(Na) . A series of peaks in which the number of L _(Na) was 1 to 13 was observed. m / z 1,896.9 the _{[Ag 25 L (H) 9} L (Na) 5 - 3H] attributed with ^3- (Ag ₂₅ L ₁₄ experimental values 5583.8, theoretical 5585.3). Similarly, m / z 1813.6 is L is one decreased _{[Ag 25 L (H) 10} L (Na) 3 - 3H] attributed with ^3- (Ag ₂₅ L ₁₃ experimental values 5377.7, theoretical 5378.9). Further, m / z 1422.4 is a peak of a tetravalent ion, and is attributed to [Ag ₂₅ L _{(H) 9} L _(Na) 5-4H] ^4- (Ag ₂₅ L ₁₄ experimental value 5583.8, theoretical value 5585.3). You.
From the above results, it was found that the composition formula of the silver cluster complex synthesized in this experiment was Ag ₂₅ L ₁₄ (that is, Ag ₂₅ (DHLA) ₁₄ ).

(Fluorescence measurement)
It was confirmed whether the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) shows a fluorescence spectrum unique to silver clusters.
A toluene solution of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) obtained in Example 1 (3) was diluted 2-fold with toluene, and 2 mL was placed in a quadrilateral quartz cell. Using a fluorescence spectrophotometer (FP-6200 manufactured by JASCO), the measurement conditions were set as follows: excitation side bandwidth: 10 nm, fluorescence side bandwidth: 10 nm, response: Fast, sensitivity: Medium, data acquisition interval: 1 nm The fluorescence was measured at an excitation wavelength of 420.0 nm and a scanning speed of 250 nm / min.

  FIG. 2 shows a fluorescence spectrum of the hybrid antibacterial agent. The strongest peak appeared at 650 nm, and peaks were also confirmed at 700 nm and 800 nm. These were distinctly different from silver nanoparticles and had a fluorescence spectrum unique to silver clusters. This confirmed that the hybrid antibacterial agent contained silver clusters.

(Reaction ratio between silver cluster complex and organic compound)
The reaction ratio between the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) synthesized in Example 1 and the organic compound (TOAB) was examined.
When reacting the organic compound (TOAB) with the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) in Example 1 (3), their molar ratio M (TOAB) / M (Ag ₂₅ (DHLA) ₁₄ ) Hybrid antibacterial agents were synthesized in place of 1, 3, 7, and 14. By observing the colors of the aqueous layer and the toluene layer after the synthesis of the hybrid antibacterial agent, the presence or absence of the synthesis of the hybrid antibacterial agent and the presence of unreacted compounds were confirmed.
An Ag ₂₅ (DHLA) ₁₄ aqueous solution and a solution of TOAB dissolved in toluene were placed in a single screw tube, shaken, and allowed to stand to separate a toluene layer (upper layer) and an aqueous layer (lower layer). The liquid colors of the obtained samples will be described below.

In the sample where M (TOAB) / M (Ag ₂₅ (DHLA) ₁₄ ) = 1, the toluene layer was dark brown and transparent, and the aqueous layer was light brown and transparent. Here, the liquid turns brown when the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) or the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) is present. The hybrid antibacterial agent dissolves in the toluene layer and the silver cluster complex dissolves in the aqueous layer. Therefore, the M (TOAB) / M (Ag 25 (DHLA) 14 = 1 sample, the hybrid type antibacterial agents have been formed, and a portion of the silver cluster complex remaining in the left water layer unreacted You can see that.

In the samples of M (TOAB) / M (Ag ₂₅ (DHLA) ₁₄ ) = 7 and 14, the toluene layer was dark brown and transparent, and the aqueous layer became cloudy. Close observation of the aqueous layer showed that the oil droplets were dispersed in the aqueous layer to form an emulsion. This is an emulsion in which TOAB dissolved in the toluene layer was dispersed in the aqueous layer. Therefore, the difference pull of M (TOAB) / M (Ag ₂₅ (DHLA) ₁₄ = 7 and 14 indicates that the hybrid antimicrobial agent is formed and that the organic compound is dispersed unreacted in the aqueous layer. I understand.

In the sample of M (TOAB) / M (Ag ₂₅ (DHLA) ₁₄ ) = 3, the toluene layer was dark brown and transparent, and the aqueous layer was almost colorless and transparent. Therefore, in the sample of M (TOAB) / M (Ag ₂₅ (DHLA) ₁₄ = 3, it is found that the hybrid antibacterial agent is formed and that the unreacted compound hardly remains.
Therefore, it was found that when the molar ratio M (TOAB) / M (Ag ₂₅ (DHLA) ₁₄ of the organic compound to the silver cluster complex was about 3, almost no unreacted compound was generated.
This result was in good agreement with the theoretical value assuming the equilibrium state of the following equation.

In hybrid antimicrobial agent _{(TOA-Ag 25 (DHLA)} 14), a silver cluster complex (Ag ₂₅ (DHLA) ₁₄₎ and an organic compound in order to verify that (TOAB) and are attached, ATR-IR measurements Was done.
For hybrid antimicrobial agent obtained in Example _{1 (3) (TOA- Ag 25} (DHLA) 14), it was ATR-IR measurements. Since the hybrid antibacterial agent was in a state of being dissolved in toluene, the toluene solution was placed in a Teflon container and dried under reduced pressure at room temperature for 3 hours by an evaporator to obtain a solid sample. A small amount of a solid sample was taken and ATR-IR measurement was performed using FT / IR-4200 (manufactured by JASCO).

FIG. 3 shows an IR spectrum of the hybrid antibacterial agent. FIG. 4 shows the structural formula of TOA-Ag ₂₅ (DHLA) ₁₄ , which is a hybrid antibacterial agent. In the IR spectrum, peaks were observed at 2924 cm ⁻¹ , 2859 cm ⁻¹ , 1466 cm ⁻¹ , 1380 cm ⁻¹ and 1218 cm ⁻¹ . Each of _{these, TOA-Ag 25 (DHLA)} 14 has CH ₂ (stretching), CH ₃ ^{(stretching), COO - TOA +, COO} - TOA +, attributed to S-CH ₂ (stretching). Since the peak attributed to COO ^- TOA ⁺ exists, the carbonyl group (-COOH) of the ligand (DHLA) of the silver cluster complex reacts with the organic compound (TOAB) to form a bond You can see that. That is, in the hybrid antibacterial agent produced in Example 1, the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) and the organic compound (TOAB) do not simply coexist, but they are chemically bonded. It was confirmed that.

(Solubility in organic solvents)
The solubility of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) in organic solvents was examined.
To give a solid sample of a toluene solution of a hybrid-type antibacterial agent obtained in Example 1 (3) (TOA-Ag 25 (DHLA) 14) was dried by an evaporator. Approximately 1 mg of the solid sample was placed in each of six containers, and methanol, ethanol, ethyl acetate, acetone, tetrahydrofuran (THF) and acetonitrile were added to each container in an amount of 1 mL each, stirred, and examined for dissolution in each organic solvent. . For comparison, a similar test was performed on a solid sample of the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) obtained in Example 1 (2).
Table 1 shows the test results. "OK" was given when all the solid samples were dissolved, and "NG" was given when the solid samples remained undissolved.

The hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) was dissolved in all organic solvents. On the other hand, the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) was soluble in methanol but not in other organic solvents. Therefore, in the hybrid-type antibacterial agent _{(TOA-Ag 25 (DHLA)} 14), by an organic compound (TOAB) is bonded to the hydrophilic silver cluster complex _{(Ag 25 (DHLA) 14)} , hydrophobicity is It was shown to rise and become soluble in various organic solvents.

(Light stability)
The photostability of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) was examined by UV-vis absorption measurement.
2 mL of a toluene solution (concentration: 4 mg / 20 mL) of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) obtained in Example 1 (3) was placed in a quadrilateral quartz cell, and the ultraviolet-visible spectrophotometer was used. Using a JASCO V-670 spectrophotometer, the measurement conditions were as follows: response Fast, bandwidth 2.0 nm, scanning speed 400 nm / min, start wavelength 1000 nm, end wavelength 300 nm, data acquisition interval 1.0 nm, and UV- The vis absorption spectrum was measured.
Then, in a quartz cell, a 405 nm pulse light (ト ル エ ン 1 ns) was irradiated to a toluene solution of the hybrid antibacterial agent with a Qauntaru-Tau apparatus manufactured by Hamamatsu Photonics Co., Ltd. for 300 minutes, and then UV-vis again. The absorption spectrum was measured. The effect of light irradiation on the silver clusters was examined by examining the spectral change caused by the decomposition of the silver clusters.
For comparison, a similar test was performed on an aqueous solution in which 3 mg of a solid sample of the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) obtained in Example 1 (2) was dissolved in 20 mL of pure water.

FIG. 5A shows the UV-vis absorption spectrum of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ), and FIG. 5B shows the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) UV-vis. It is a vis absorption spectrum.
Before light irradiation, the hybrid antibacterial agent and the silver cluster complex had similar spectra, and three peaks were confirmed at about 495 nm, about 425 nm, and about 330 nm. These are absorption peaks associated with transitions between levels at which the electron energy is discretized, and are peaks unique to silver clusters where a quantum size effect is observed.

After the light irradiation, the spectrum of the hybrid antibacterial agent shows three peaks although the peak intensity slightly fluctuates as compared to that before the light irradiation (FIG. 5 (a)). On the other hand, in the spectrum of the silver cluster complex after light irradiation, the three peaks disappeared and became broad.
In the case of the silver cluster complex, it can be seen that the silver cluster was decomposed by light irradiation. In other words, the silver cluster complex has low photostability.
On the other hand, in the hybrid antibacterial agent, the silver cluster did not decompose even when irradiated with light. That is, the hybrid antibacterial agent has higher light stability than the silver cluster complex. It can be said that in the hybrid antibacterial agent, the light resistance was improved due to the binding of the organic compound to the silver cluster complex.

(Thermal stability)
Thermogravimetric (TG) measurement, was examined the thermal stability of hybrids antibacterial agent _{(TOA-Ag 25 (DHLA)} 14).
A 4 mg solid sample of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) obtained in Example 1 (3) was placed in an aluminum container, and was then subjected to thermal analysis (Rigaku Thermo plus EVO). The TG curve was measured from room temperature (25 ° C.) to 200 ° C. at a temperature rising rate of 5 ° C./min.
For comparison, a similar test was performed on a 2 mg solid sample of the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ) obtained in Example 1 (2).

FIG. 6A is a TG curve of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ). FIG. 6B is a TG curve of the silver cluster complex (Ag ₂₅ (DHLA) ₁₄ ). In the case of the silver cluster complex, the weight loss due to thermal decomposition started around 50 ° C, and the weight loss was observed over a wide temperature range (50 ° C to 140 ° C). In other words, it can be seen that the silver cluster complex can be decomposed even at a low temperature of about 50 ° C. In other words, the silver cluster complex has low thermal stability.
On the other hand, the hybrid antibacterial agent showed no weight loss due to thermal decomposition up to around 160 ° C., and showed a weight loss above 160 ° C. The hybrid antibacterial agent was found to have heat resistance of about 160 ° C.

  The hybrid type antibacterial agent has heat resistance higher than 100 ° C. as compared with the silver cluster complex. It can be said that in the hybrid antibacterial agent, the heat resistance was remarkably improved due to the binding of the organic compound to the silver cluster complex.

(Antibacterial test)
It was investigated antimicrobial hybrid antimicrobial agent _{(TOA-Ag 25 (DHLA)} 14).
A toluene solution of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) obtained in Example 1 (3) was placed in a Teflon container, and dried under reduced pressure at room temperature for 3 hours using an evaporator to obtain a solid sample. Then, the solid sample was dissolved in ethanol to prepare an ethanol solution of the hybrid antibacterial agent (abbreviated as “hybrid antibacterial agent solution” in this example). Five ethanol solutions were prepared at different concentrations (0.001 wt%, 0.01 wt%, 0.1 wt%, 1 wt% and 5 wt%).
Five 5 cm square glass plates were prepared and washed with methanol. 200 μL of ethanol solutions having different concentrations were dropped on the upper surface of each glass plate, respectively, and applied to the entire upper surface of the glass plate using a spin coater (ACTIVE Spincoater) at a rotation speed of 400 rpm and 45 s. Ethanol in the ethanol solution evaporated immediately, and a film of the hybrid antibacterial agent was formed on the upper surface of the glass plate. This hybrid antibacterial agent-coated glass plate was used as a test piece.

  Staphylococcus aureus (NB Staphylococus aureus NBRC 12732) and Klebsiella pneumonie IAM 12015 in 5 mL of normal bouillon medium (Eiken Chemical Co., Ltd.) were cultured at 27 ° C. overnight at a final concentration of 1/50. Diluted with sterile water containing normal broth medium at a concentration. A test piece (a glass plate coated with a hybrid antibacterial agent) was placed in a Petri dish, and 0.4 mL of the bacterial suspension was placed thereon. After covering this bacterial suspension with a polyethylene sheet (4 cm × 4 cm), the dish was covered and left at 30 ° C. Twenty-four hours later, the bacterial suspension on the test piece was recovered in 4.5 mL of sterile physiological saline, and subjected to four-fold dilutions by 10 times. The number of viable bacteria in 1 mL of the diluted solution was measured.

FIG. 7 shows the experimental results of the antibacterial test of the hybrid antibacterial agent against Staphylococcus aureus, and FIG. 8 shows the experimental results of the antibacterial test of the hybrid antibacterial agent against Klebsiella pneumoniae. In the bar graphs of FIGS. 7 and 8, the vertical axis represents the increase rate of the viable cell count based on the time of inoculation.
As can be seen from FIG. 7, in the control test piece (without silver cluster coat), the viable count of Staphylococcus aureus after 24 hours increased about 100 times compared to the time of inoculation. In the test piece coated with the 0.001 wt% hybrid antibacterial agent solution, the increase was about 80 times that at the time of inoculation. The 0.005 wt% hybrid antibacterial agent solution is about 0.16 times that at the time of inoculation, and the number of viable bacteria is drastically reduced. Furthermore, in the test pieces coated with the hybrid antibacterial agent solutions of 0.01 wt%, 0.1 wt%, 1.0 wt% and 5.0 wt%, the viable cell count was below the detection limit (ND). That is, the test piece coated with the hybrid antibacterial agent solution having a concentration of 0.01 wt% or more had bactericidal activity against Staphylococcus aureus.

As can be seen from FIG. 8, in the case of Klebsiella pneumoniae, the viable count of Klebsiella pneumoniae after 24 hours increased about 27 times in the control test piece (without silver cluster coat). In the test piece coated with the 0.001 wt% hybrid antibacterial agent solution, the increase was about 10 times that at the time of inoculation. Test pieces coated with 0.005 wt%, 0.01 wt%, 0.1 wt%, 1.0 wt% and 5.0 wt% of the hybrid antibacterial agent solution showed that the viable cell count was below the detection limit (ND). That is, the test piece coated with the hybrid antibacterial agent solution having a concentration of 0.005 wt% or more had bactericidal activity against Klebsiella pneumoniae.
From the results of FIGS. 6 and 7, by applying the hybrid antibacterial agent solution at a very low concentration of 0.005 wt% (50 ppm), an excellent antibacterial action against both Staphylococcus aureus and Klebsiella pneumoniae was obtained. It turned out to show.

In addition, TOAB which is a quaternary ammonium salt shows antibacterial properties even when used alone. Therefore, the antibacterial properties of TOAB and the hybrid antibacterial agent were compared. Using a 0.005 wt% TOAB solution, a TOAB-coated glass plate was prepared in the same manner as the hybrid antibacterial agent-coated glass plate, and used as a sample piece. Using the TOAB-coated glass plate, an antibacterial test against Staphylococcus aureus and Klebsiella pneumoniae was performed in the same manner as the hybrid antibacterial agent-coated glass plate.
FIG. 9 shows the experimental results of a test piece coated with a 0.005 wt% TOAB solution and a test piece coated with a 0.005 wt% hybrid antibacterial agent solution. In the test piece to which the TOAB solution was applied, the viable cell count of Staphylococcus aureus increased about 2.2 times that at the time of inoculation and the viable cell count of Klebsiella pneumoniae decreased about 0.88 times at the time of inoculation. The hybrid-type antibacterial agent was found to exhibit an extremely higher antibacterial effect on both Staphylococcus aureus and Klebsiella pneumoniae than the TOAB solution.

Conventional silver antibacterial agents are said to exhibit antibacterial properties at a concentration of several hundred ppm. In contrast, the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) exhibits antibacterial properties at a concentration of 50 ppm. Therefore, it was found that the hybrid antibacterial agent had an extremely high antibacterial activity.

(Elution of silver ions)
The amount of silver ions eluted from the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) was examined.
A toluene solution of the hybrid antibacterial agent (TOA-Ag ₂₅ (DHLA) ₁₄ ) obtained in Example 1 (3) was placed in a Teflon container, and dried under reduced pressure at room temperature for 3 hours using an evaporator to obtain a solid sample. Then, the solid sample was dissolved in ethanol to prepare a 0.01 wt% ethanol solution of the hybrid antibacterial agent (in this example, abbreviated as “hybrid antibacterial agent solution”).
Six 5 cm square glass plates were prepared and washed with methanol. On the upper surface of each glass plate, 200 μL of an ethanol solution was dropped, and the whole solution was applied to the entire upper surface of the glass plate using a spin coater (ACTIVE Spincoater) at a rotation speed of 400 rpm and 45 s. Ethanol in the ethanol solution evaporated immediately, and a film of the hybrid antibacterial agent was formed on the upper surface of the glass plate. This hybrid antibacterial agent-coated glass plate was used as a test piece.

Six test pieces (glass plates coated with a hybrid antibacterial agent) were placed in a Petri dish, and 1 mL of pure water was dropped per glass plate. After covering the pure water with a polyethylene sheet (4 cm × 4 cm), the dish was covered and left at room temperature (23 ° C.) for 24 hours. After standing, 4.35 mL was collected from the dropped pure water (6 mL for 6 plates), and 5.65 mL of pure water was added to make 10 mL (corresponding to 2.3-fold dilution). The diluted solution was subjected to ICP-MS measurement.
The elution result of silver ion in the water diluted 2.3 times was 8.4 μg / L (8.4 ppb). When this value was converted, it was found that 8.4 × 2.3 = 19.3 ppb of silver ions was eluted in the water before dilution.

It has been reported that silver ions are harmful to the human body when taken into the body for a long time. In the most stringent United States, the United States Environmental Protection Agency's (EPA) drinking water standard specifies a limit of 100 ppb for silver in drinking water. In addition, there is a report that water containing silver ions of 100 ppb or more has cytotoxicity.
In the hybrid-type antibacterial agent _{(TOA-Ag 25 (DHLA)} 14), even specimens with 0.01 wt% ethanol solution which can exhibit sufficient antibacterial performance, elution concentration of silver ions very about 10 ppb It was low. Therefore, the hybrid antibacterial agent can be used at a concentration capable of exhibiting the antibacterial ability (0.005 wt% or more) and can suppress the elution amount of silver ions without any problem in safety and health.

  The present invention, for example, medical equipment, baby products, nursing care products, bath products, kitchenware, tableware, drinking water plumbing parts, household hygiene products, home appliances, clothing, building materials, agricultural materials, automotive interior parts, It can be used to impart antibacterial properties to various products such as stationery.

Claims (12)

A silver cluster, a ligand bonded to the silver cluster, and an organic compound bonded to the ligand,
The ligand has a functional group containing a hetero atom and an acidic functional group,
The organic compound is an antibacterial agent which is an aliphatic amine containing an alkyl group having a carbon number of C ₄ -C _18.   The antibacterial agent according to claim 1, wherein the aliphatic amine includes at least one selected from the group consisting of a primary amine, a secondary amine, a tertiary amine, and a quaternary ammonium salt.   The antibacterial agent according to claim 2, wherein the aliphatic amine is a quaternary ammonium salt.   The aliphatic amine is hexylamine, octylamine, decylamine, dodecylamine, cyclohexylamine, 3- (N-ethylamino) -1-butanol, diphenylamine, N-ethylethanamine, N-ethyl-N-methylbutane-1 And at least one selected from the group consisting of -amine, N, N-dimethylmethanamine, tetraoctylammonium bromide, cetyltrimethylammonium bromide, benzalkonium chloride, cetylpyridinium chloride, benzethonium chloride and decalinium chloride. Or the antibacterial agent according to 2.   The antimicrobial agent according to any one of claims 1 to 4, wherein the functional group containing a hetero atom of the ligand includes at least one selected from the group consisting of a thiol group, an amino group, and a carboxyl group. .   The ligand comprises at least one selected from the group consisting of dihydrolipoic acid, glutathione, captopril, mercaptopropionic acid, mercaptohexanoic acid, mercaptooctanoic acid, mercaptoundecanoic acid, cysteine, methionine and glutathione. 6. The antibacterial agent according to any one of 5. Synthesizing a silver cluster complex comprising a silver cluster and a ligand bonded to the silver cluster;
Reacting the silver cluster complex with an organic compound to bind the ligand and the organic compound,
The ligand has a functional group containing a hetero atom and an acidic functional group,
The organic compound is an aliphatic amine containing an alkyl group having a carbon number of C ₄ -C _18, a manufacturing method of the antimicrobial agent.   The method according to claim 7, wherein the reacting comprises stirring the aqueous solution containing the silver cluster and the organic solution containing the organic compound for 5 to 10 minutes.   The method according to claim 7 or 8, further comprising a step of purifying the reactant after the step of reacting.   The aliphatic amine according to any one of claims 7 to 9, wherein the aliphatic amine comprises at least one selected from the group consisting of a primary amine, a secondary amine, a tertiary amine and a quaternary ammonium salt. Manufacturing method.   The method according to any one of claims 7 to 10, wherein the aliphatic amine is a quaternary ammonium salt.   The method according to any one of claims 7 to 11, wherein the functional group containing a hetero atom of the ligand includes at least one selected from the group consisting of a thiol group, an amino group, and a carboxyl group. .

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