WO2021241626A1

WO2021241626A1 - Cerium oxide nanoparticles, antibacterial agent, antiviral agent and method for producing cerium oxide nanoparticles

Info

Publication number: WO2021241626A1
Application number: PCT/JP2021/019961
Authority: WO
Inventors: 翔太関口; 雄介加川; 崇光本白水; 正照伊藤
Original assignee: 東レ株式会社
Priority date: 2020-05-27
Filing date: 2021-05-26
Publication date: 2021-12-02
Also published as: JPWO2021241626A1

Abstract

The present invention addresses the problem of providing cerium oxide nanoparticles having high antibacterial activity and antiviral activity. The present invention pertains to cerium oxide nanoparticles that are surface-coated with a polyvalent carboxylic acid and a compound having a heterocyclic amine structure.

Description

Methods for Producing Cerium Oxide Nanoparticles, Antibacterial Agents, Antiviral Agents and Cerium Oxide Nanoparticles

The present invention relates to nanoparticles of cerium oxide whose surface is coated with a vinyl polymer or polyamide, an antibacterial agent containing the nanoparticles, an antiviral agent, and a method for producing the nanoparticles.

In recent years, with increasing awareness of safety and hygiene management, antibacterial technology that decomposes microorganisms and harmful substances has been attracting attention. For example, titanium oxide has the property of oxidatively decomposing organic substances due to its photocatalytic properties. Such oxidative decomposition characteristics are expected to be used as antibacterial agents for inactivating microorganisms such as viruses, bacteria, molds and yeasts, as well as for decomposing low molecules such as acetaldehyde and ammonia and harmful substances such as allergens. ing.

On the other hand, nanoparticles of cerium oxide (nanoceria) have the same catalytic activity as oxidases such as oxidase and peroxidase, and are expected to be applied as antibacterial agents utilizing the oxidizing action. Since these catalytic activities do not require a special light source such as ultraviolet rays, they can be expected to be used for applications different from titanium oxide.
In general, metal oxides have the property of being positively charged, and nanoparticles of cerium oxide are also positively charged in the acidic to neutral pH range. However, positively charged cerium oxide nanoparticles have a problem of non-specific adsorption with serum proteins. When antibacterial processing is applied to medical devices and used in vivo, it is necessary to suppress non-specific adsorption that leads to a decrease in antibacterial activity. For such non-specific adsorption suppression, a method of coating the particle surface with a stabilizer has been studied.
For example, Non-Patent Document 1 discloses that nanoceria whose surface is covered with polyacrylic acid has antibacterial activity. Further, Non-Patent Document 2 discloses that cerium oxide produced by using ethylenediaminetetraacetic acid (EDTA) as a stabilizer has antibacterial activity.

The present inventors evaluated the antibacterial action of nanoparticles of cerium oxide using polyacrylic acid described in Non-Patent Document 1 and EDTA described in Non-Patent Document 2 as a stabilizer. However, it cannot be said that the growth inhibition rate of Escherichia coli was sufficient in either case. Therefore, further studies were conducted with the task of finding nanoparticles of cerium oxide having higher antibacterial activity.

As a result of studies to solve the above problems, the present inventors have made a compound having a heterocyclic amine skeleton in addition to polyacrylic acid and polyvalent carboxylic acid including EDTA, and surface of nanoparticles of cerium oxide. It was found that the antibacterial activity was improved by coating with. We also found that nanoparticles of cerium oxide whose surface was coated with a polyvalent carboxylic acid and a compound having a heterocyclic amine skeleton also improved antiviral performance, and completed the present invention.

The present invention comprises the following aspects.
(1) Cerium oxide nanoparticles whose surface is coated with a polyvalent carboxylic acid and a compound having a heterocyclic amine skeleton.
(2) The cerium oxide nanoparticles according to (1), wherein the polyvalent carboxylic acid has a valence of trivalent or higher.
(3) The cerium oxide nanoparticles according to (1) or (2), wherein the compound having a heterocyclic amine skeleton is a vinyl polymer or polyamide having a heterocyclic amine skeleton in the main chain or side chain.
(4) The cerium oxide nanoparticles according to any one of (1) to (3), wherein the heterocyclic amine skeleton is composed of any of piperazine, pyridine, imidazole or carbazole.
(5) The nanoparticles of cerium oxide according to (3) or (4), wherein the vinyl-based polymer is a polymer having the heterocyclic amine skeleton in the side chain.
(6) The nanoparticles of cerium oxide according to (3) or (4), wherein the polyamide is a polymer having the heterocyclic amine skeleton in the main chain.
(7) The compound having a heterocyclic amine skeleton is a monocyclic or bicyclic aromatic heterocyclic compound having a 5-membered ring and / or a 6-membered ring structure, (1) or (2). The nanoparticles of cerium oxide described in.

(8) The cerium oxide nanoparticles according to (1) or (2), wherein the compound having a heterocyclic amine skeleton is a compound represented by the general formula (I).

In formula (I), X represents NR ² , O, S, and R ¹ and R ² are hydrogen atoms, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, and 1 to 4 carbon atoms. The aminoalkyl group of the above, or the alkyl sulfonate group having 1 to 4 carbon atoms is shown. R ¹ and R ² may be the same or different.
(9) The antibacterial agent containing the nanoparticles of cerium oxide according to any one of (1) to (8).
(10) The antiviral agent containing the nanoparticles of cerium oxide according to any one of (1) to (8).
(11) A method for producing nanoparticles of cerium oxide whose surface is coated with a polyvalent carboxylic acid and a compound having a heterocyclic amine skeleton, which is a polyvalent carboxylic acid and a vinyl-based compound having a heterocyclic amine skeleton. A method for producing nanoparticles of cerium oxide, which comprises a step A of preparing a solution containing a polymer or a polyamide and cerium (III) ions, and a step B of adding an oxidizing agent to the solution obtained in the step A.

INDUSTRIAL APPLICABILITY According to the present invention, it becomes possible to obtain nanoparticles of cerium oxide having high antibacterial activity and antiviral performance.

The surface of the cerium oxide nanoparticles of the present invention is coated with a polyvalent carboxylic acid and a compound having a heterocyclic amine skeleton. Polycarboxylic acids and compounds having a heterocyclic amine skeleton are used in the present invention as stabilizers for nanoparticles of cerium oxide.

The polyvalent carboxylic acid is a carboxylic acid having a plurality of carboxyl groups or a salt thereof, or a mixture of the carboxylic acid and the salt thereof. Preferred polyvalent carboxylic acids are trivalent or higher carboxylic acids and / or salts thereof. The trivalent carboxylic acid is citric acid, nitrilotriacetic acid (NTA), hydroxyethylethylenediaminetriacetic acid (HEDTA), and the tetravalent carboxylic acid is ethylenediaminetetraacetic acid (EDTA), ethylenediaminediaminedic acid (EDDS), glycol ether. Diaminetetraacetic acid (EGTA), hydroxyethylethylenediaminetetraacetic acid (HEDTA), (DTPA) as pentavalent carboxylic acid, triethylenetetraminehexacetic acid (TTHA) as hexavalent carboxylic acid, as carboxylic acid of 7 or more valence Includes polyacrylic acid and / or salts thereof.

Examples of the compound having a heterocyclic amine skeleton used in the present invention include aromatic heterocyclic compounds, alicyclic amines, and vinyl polymers or polyamides having a heterocyclic amine skeleton in the main chain or side chain. can.

As the aromatic heterocyclic compound used in the present invention, a monocyclic or bicyclic aromatic heterocyclic compound having a 5-membered ring and / or a 6-membered ring structure is preferable, and for example, pyridine, pyridazine, pyrimidine, and imidazole are preferable. , Pyrazole, benzoimidazole, carbazole and the like are exemplified. The aromatic heterocyclic compound may have a substituent. The substituent here is an alkyl group, an acetyl group, a hydroxyl group, an amino group, a cyano group, a carboxyl group, an ester group, an aldehyde group, an amide group, an ether group, a ketone group, a halogen group, a sulfonic acid group or a phosphoric acid group. Is preferable. The number of substituents may be singular or plural.

As the alicyclic amine used in the present invention, an alicyclic amine represented by the general formula (I) is exemplified.

In formula (I), X represents NR ² , O, S, and R ¹ and R ² are hydrogen atoms, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, and 1 to 4 carbon atoms. The aminoalkyl group of the above, or the alkyl sulfonate group having 1 to 4 carbon atoms is shown. R ¹ and R ² may be the same or different.

As a more preferable embodiment of the alicyclic amine, in the above chemical formula (I), X represents NR ² and O, R ¹ and R ² are hydrogen atoms, an alkyl group having 1 to 2 carbon atoms, and 2 to 2 carbon atoms. It shows a hydroxyalkyl group of 3, an aminoalkyl group having 2 to 3 carbon atoms, and an alkyl sulfonate group having 2 to 3 carbon atoms. R ¹ and R ² may be the same or different.

Examples of the alicyclic amine include piperazine, 1-methylpiperazine, N, N'-dimethylpiperazine, 1-ethylpiperazine, N, N'-diethylpiperazine, 1- (2-hydroxyethyl) piperazine, and 1,4-bis. (2-Hydroxyethyl) piperazine, N- (2-aminoethyl) piperazine, 1,4-bis (2-aminoethyl) piperazine, 2- [4- (2-hydroxyethyl) -1-piperazinyl] ethanesulfonic acid , Piperazin-1,4-bis (2-ethanesulfonic acid), morpholine, 4-methylmorpholine, 4-ethylmorpholine, 4- (2-aminoethyl) morpholine, 4- (2-hydroxyethyl) morpholine, 2- Examples thereof include morpholinoethanesulfonic acid and 3-morpholinopropanesulfonic acid.

The vinyl-based polymer or polyamide having a heterocyclic amine skeleton in the main chain or side chain (hereinafter, may be abbreviated as "polymer having a heterocyclic amine skeleton") used in the present invention includes pyrrolidine, pyrrol, pyrazole, and the like. Those having a heterocyclic amine skeleton such as piperazine, pyridine, diazine, imidazole or carbazole in the main chain or side chain, and those having piperazine, pyridine, imidazole or carbazole in the main chain or side chain are preferable. The vinyl polymer or polyamide having the heterocyclic amine skeleton of the present invention may have a substituent at any position on the main chain or side chain, or may have a substituent at any position on the heterocyclic amine skeleton. May have. For example, a polymer having a heterocyclic amine skeleton in the main chain and a substituent in the side chain, a polymer having a heterocyclic amine skeleton having a substituent in the main chain, and a substituent in the side chain. Examples thereof include a polymer having a heterocyclic amine skeleton and a polymer having a heterocyclic amine skeleton in a side chain via a substituent. The substituent here is an alkyl group, an acetyl group, a hydroxyl group, an amino group, a cyano group, a carboxyl group, an ester group, an aldehyde group, an amide group, an ether group, a ketone group, a halogen group, a sulfonic acid group or a phosphoric acid group. Is preferable. The number of substituents may be singular or plural.

The vinyl-based polymer having a heterocyclic amine skeleton used in the present invention is a polymer (polyvinyl) having a polyethylene structure in which a vinyl-based monomer is condensed as a monomer in the main chain. As an example, the structure of a vinyl polymer having a piperazine skeleton in the main chain or side chain is shown in the following general formulas (II) and (III).
As shown in the general formula (II), when the piperazine skeleton is contained in the main chain, the piperazine skeleton is provided as a part of the polyethylene structure of the main chain. When another heterocyclic amine skeleton such as pyridine, imidazole or carbazole skeleton is contained in the main chain, the heterocyclic amine skeleton is also provided as a part of the polyethylene structure of the main chain, as in the general formula (II).

In formula (II), n represents an arbitrary integer.

In formula (III), n represents an arbitrary integer.

When the vinyl polymer having a heterocyclic amine skeleton used in the present invention has a piperazine skeleton in the side chain, for example, as shown in the general formula (III), the piperazine skeleton may be directly bonded to the polyethylene main chain. However, the piperazine skeleton may be bonded via an alkylene group, an amino group, or the like. In the case of having another heterocyclic amine skeleton such as pyridine, imidazole or carbazole skeleton, the same as the case of having the piperazine skeleton represented by the general formula (II), pyridine, imidazole or carbazole skeleton etc. are attached to the polyethylene main chain. The heterocyclic amine skeleton of the above may be directly bonded, or may be bonded via an alkylene group, an amino group, or the like.

The vinyl polymer having a heterocyclic amine skeleton used in the present invention is preferably a vinyl polymer having a piperazine, pyridine, imidazole or carbazole skeleton in the side chain. A vinyl-based polymer having a piperazine, pyridine, imidazole or carbazole skeleton on the side chain is obtained by a polymerization reaction of a vinyl-based monomer having a piperazine, pyridine, imidazole or carbazole skeleton.

Specific examples of the vinyl-based monomer in this case include 1-vinylpiperazin, (4-vinylpiperazin-1-yl) methaneamine, 2- (4-vinylpiperazin-1-yl) ethane-1-amine, and 2-vinyl. Piperazine, (3-vinylpiperazin-1-yl) methaneamine, 2- (3-vinylpiperazin-1-yl) ethane-1-amine, (2-vinylpiperazin-1-yl) methaneamine, 2- (2-vinyl) Piperazin-1-yl) ethane-1-amine, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, 2-vinylimidazole, 4-vinylimidazole, 9-vinylcarbazole and the like can be mentioned. .. Further, the vinyl-based monomer may have a substituent at any position other than the vinyl group, and may have, for example, a methyl group or a cyano group as a substituent.

The vinyl-based polymer having a heterocyclic amine skeleton used in the present invention may be a homopolymer or a copolymer made from two or more kinds of vinyl-based monomers.
Preferred specific examples of the vinyl polymer used in the present invention are poly (1-vinylpiperazin), poly ((4-vinylpiperazin-1-yl) methaneamine), poly (2- (4-vinylpiperazin-1-yl)). Etan-1-amine), poly (2-vinylpyridine), poly (3-vinylpyridine), poly (4-vinylpyridine), poly (1-vinylimidazole), poly (2-vinylimidazole), poly (4) -Vinylimidazole), poly (9-vinylcarbazole).

The polyamide having a heterocyclic amine skeleton used in the present invention is a polymer having an amide bond in the main chain and has a heterocyclic amine skeleton such as piperazine, pyridine, imidazole or carbazole skeleton in the main chain or side chain. Has. The following general formula (IV) shows the structure of a polyamide having a piperazine skeleton as a heterocyclic amine bone in the main chain. Here, it has a piperazine skeleton as a part of the amide structure which is the main chain, and nitrogen and a carbonyl group in the heterocycle of the piperazine skeleton form an amide bond. In the case where the main chain has another heterocyclic amine skeleton such as a pyridine, imidazole or carbazole skeleton having an amino group as a substituent, the heterocyclic amine is used as a part of the amide structure as in the general formula (IV). Has a skeleton.

In equation (IV), n represents an arbitrary integer.

When the piperazine skeleton is provided in the side chain of the polyamide having the heterocyclic amine skeleton used in the present invention, for example, the piperazine skeleton may be directly bonded to the polyamide main chain as shown in the following general formula (V). However, the piperazine skeleton may be bonded via an alkyl group, an amino group, or the like. In the case of having another heterocyclic amine skeleton such as pyridine, imidazole or carbazole skeleton, as in the case of having a piperazine skeleton represented by the general formula (V), a complex such as pyridine, imidazole or carbazole skeleton is used in the polyamide backbone. The cyclic amine skeleton may be directly bonded, or may be bonded via an alkylene group, an amino group, or the like.

In equation (V), n represents an arbitrary integer.

As the polyamide having a heterocyclic amine skeleton used in the present invention, a polymer having a heterocyclic amine skeleton such as a piperazine skeleton represented by the general formula (IV) in the main chain is preferable.
The polyamide having a piperazine skeleton in the main chain used in the present invention is obtained by a condensation reaction between an amine having a heterocyclic amine skeleton such as a piperazine skeleton and a dicarboxylic acid.

Preferred examples of amines having a heterocyclic amine skeleton are piperazine, (aminomethyl) piperazine, (aminoethyl) piperazine, (aminopropyl) piperazine, (aminobutyl) piperazine, 1,4-bis (aminomethyl) piperazine. , 1,4-Bis (2-aminoethyl) piperazine, 1,4-bis (3-aminopropyl) piperazine, 1,4-bis (4-aminobutyl) piperazine, diaminopyridine, aminoimidazole, aminocarbazole, etc. Can be mentioned. Among these, (aminoethyl) piperazine and 1,4-bis (3-aminopropyl) piperazine are more preferable. Further, these amines may have a substituent at any position other than nitrogen which can form an amide bond.

Further, as a preferable example of the above dicarboxylic acid, 1H-imidazole-2,4-dicarboxylic acid, 1H-imidazole-2,5-dicarboxylic acid, 1H-imidazole-4,5-dicarboxylic acid, pyridine-2,3- Dicarboxylic acid, pyridine-2,4-dicarboxylic acid, pyridine-2,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-3,4-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, adipic acid , Sevacinic acid, dodecadicarboxylic acid, terephthalic acid, isophthalic acid and the like. Further, these dicarboxylic acids may have a substituent at any position other than the carboxyl group capable of forming an amide bond.

As the polyamide having a heterocyclic amine skeleton used in the present invention, a polyamide obtained by combining the above amine and a dicarboxylic acid can be preferably used, and a polyamide obtained by combining (aminoethyl) piperazin and adipic acid is particularly preferable. ..
Further, the polyamide having a heterocyclic amine skeleton used in the present invention may have a polyalkylene glycol structure in a part of the polyamide main chain. Specific examples thereof include polyamides having a skeleton of (aminoethyl) piperazine, adipic acid, and bis (aminopropyl) polyethylene glycol.

Further, the polyamide having a heterocyclic amine skeleton used in the present invention may be a copolymer of a polyamide having a heterocyclic amine skeleton such as piperazine, pyridine, imidazole or carbazole and another polymer. In this case, specific examples of other polymers include polycaproamide (nylon 6), polyhexamethylene adipamide (nylon 66), polytetramethylene adipamide (nylon 46), and polypentamethylene adipamide (nylon). 56), Polypentamethylene sebacamide (nylon 510), polyhexamethylene sebacamide (nylon 610), polyhexamethylene dodecamide (nylon 612), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (nylon) 66 / 6T), Polyhexamethylene adipamide / Polyhexamethylene terephthalamide / Polyhexamethylene isophthalamide copolymer (nylon 66 / 6T / 6I), Polyhexamethylene terephthalamide / Polyhexamethylene isophthalamide copolymer (Nylon 6T / 6I) ), Polyxylylene adipamide (nylon XD6) and the like.

The molecular weight of the vinyl polymer or polyamide having a heterocyclic amine skeleton used in the present invention is preferably 3000 or more and 1,000,000 or less, and more preferably 10,000 or more and 50,000 or less.

Cerium oxide nanoparticles of the present invention, Ce ₂ O ₃ and (the particles, called. "Central nucleus" hereinafter) cerium oxide particles constituted of a mixture of CeO ₂ as the center and the surface polycarboxylic acid , And a structure coated with a compound having a heterocyclic amine skeleton. The particle size of the central core is preferably about 1 nm or more and 100 nm or less. The particle size can be calculated by measuring two or more of the major axis diameter, the minor axis diameter, and the directional diameter using a transmission electron microscope, and calculating the average value as the particle diameter.

_Ce 2 _{O 3} and CeO ₂ in the ratio of the central core can be calculated cerium (III) and as the ratio of the cerium (IV). When calculating the ratio, the nanoparticles of cerium oxide of the present invention may be dried and calculated by X-ray photoelectron spectroscopy (XPS).

The particle size of the nanoparticles of cerium oxide of the present invention is preferably 200 nm or less as the hydrodynamic diameter including the compound layer on the surface. The hydrodynamic diameter is analyzed by the Marquart method, in which nanoparticles of cerium oxide of the present invention are dissolved in any solvent such as water and ethanol, dynamic light scattering is measured to derive an autocorrelation function, and the autocorrelation function is derived. Then, it is calculated as the average particle size from the number conversion histogram. ELS-Z manufactured by Otsuka Electronics Co., Ltd. is used for the measurement of dynamic light scattering.

The cerium oxide nanoparticles of the present invention are used in step A for obtaining a solution containing a polyvalent carboxylic acid, a compound having a heterocyclic amine skeleton, and cerium (III) ion, and an oxidizing agent in the solution obtained in step A. Can be produced by a method for producing nanoparticles of cerium oxide, which comprises the step B of adding cerium oxide. Hereinafter, the method for producing nanoparticles of cerium oxide of the present invention will be described for each step.

In step A, a polyvalent carboxylic acid (including an ion or salt of the polyvalent carboxylic acid), a compound having a heterocyclic amine skeleton, and a cerium (III) ion (including a cerium (III) salt) are mixed and mixed. Is the process of obtaining.
The polyvalent carboxylic acid used in the step A can be used as a solution in which the above-mentioned polyvalent carboxylic acid or a salt thereof is dissolved in an arbitrary solvent. In this case, the solvent is preferably water or a solvent compatible with water. If the polyvalent carboxylic acid is difficult to dissolve in the solvent, it may be dissolved by heating or sonication, or the pH may be adjusted with an acid or a base.

The compound having a heterocyclic amine skeleton used in the step A can be used as a solution by dissolving the above-mentioned compound having a heterocyclic amine skeleton in an arbitrary solvent. The solvent is preferably water or a solvent compatible with water. When the compound having a heterocyclic amine skeleton is difficult to dissolve in a solvent, it may be dissolved by heating or sonication, or the pH may be adjusted with an acid or a base.
Specific examples of solvents for polyvalent carboxylic acids and compounds having a heterocyclic amine skeleton include, for example, methanol, ethanol, propanol, isopropanol, butanol, tetrahydrofuran, glycerol, ethylene glycol, acetone, dimethylformamide (DMF), dimethyl. Examples include sulfoxide (DMSO), triethylamine, pyridine and the like.

The cerium (III) ion (including the cerium (III) salt) used in step A can be dissolved in any solvent and used as a solution. As the cerium (III) salt, for example, cerium nitrate (III) hexahydrate may be used.
The mixing method of the solution containing the polyvalent carboxylic acid or the salt of the polyvalent carboxylic acid, the solution of the compound having a heterocyclic amine skeleton, and the solution containing the cerium (III) ion or the cerium (III) salt is not particularly limited. For example, a method of adding a solution containing cerium (III) ions or a cerium (III) salt to a solution containing ions of a polyvalent carboxylic acid and a polymer having a heterocyclic amine skeleton is preferably used. In such a case, a method of mixing a solution containing an ion of a polyvalent carboxylic acid and a solution of a compound having a heterocyclic amine skeleton and adding a solution containing a cerium (III) ion or a cerium (III) salt, a heterocyclic amine. A method in which a compound having a skeleton is added to a solution containing polyvalent carboxylic acid ions to dissolve the solution, and a solution containing cerium (III) ions or a cerium (III) salt is added. Examples thereof include a method of dissolving in a solution of a compound having a skeleton and adding a solution containing cerium (III) ion or a cerium (III) salt. At this time, in order to dissolve the cerium salt, the solvent of the mixed solution may be finally water or a solvent compatible with the above water containing 10% or more of water.

In the mixed solution obtained in step A, the concentration of the polyvalent carboxylic acid is preferably 0.05 molar equivalents or more and 5 molar equivalents or less with respect to cerium (III) ions when the valence is trivalent or more and hexavalent or less. , 0.1 molar equivalent or more and 1 molar equivalent or less is more preferable. When the valence is 7 or more, the mass concentration is preferably 0.01% or more and 5% or less, and more preferably 0.1% or more and 1% or less.

Further, in the mixed solution, the concentration of the solution of the compound having a heterocyclic amine skeleton is preferably 0.01% or more and 5% or less, more preferably 0.1% or more and 2% or less in terms of mass concentration.
Further, in the mixed solution, the concentration of cerium (III) is the concentration of cerium (III) / hexahydrate for the compound having a heterocyclic amine skeleton when cerium (III) nitrate / hexahydrate is used. It is preferable to mix so that the mass ratio is 0.1 or more and 5.0 or less. The mixed solution is preferably mixed for at least 5 minutes until the solution becomes uniform.

Step B is a step of adding an oxidizing agent to the solution obtained in step A.
The oxidizing agents used in step B include nitric acid, potassium nitrate, hypochloric acid, chloric acid, chloric acid, perchloric acid, halogen, hydrogen halide, permanganate, chromic acid, dichromic acid, oxalic acid, and sulfide. Examples include hydrogen, sulfur dioxide, sodium thiosulfate, nitric acid, hydrogen peroxide and the like. Of these, hydrogen peroxide is particularly preferable. The addition amount may be 0.1 equivalent or more and 10 equivalent or less, preferably 0.5 equivalent or more and 2 equivalent or less, as a molar equivalent with respect to the cerium (III) ion.

Center The addition of oxidizing agent to the solution obtained in step A, cerium (III) ions are oxidized to cerium (IV), _Ce 2 _{O 3} and cerium oxide particles constituted of a mixture of CeO ₂ (the central core) As a result, the formation reaction of particles whose surface is coated with the above-mentioned polyvalent carboxylic acid and a compound having a heterocyclic amine skeleton is started. When an oxidizing agent is added to the solution obtained in step A, the reaction of forming nanoparticles of cerium oxide of the present invention begins. In the reaction, the solution is colored yellow, orange, red, brown or the like. This is the coloration caused by the conversion of cerium (III) ions to cerium (IV), and the degree of coloring is the ratio of cerium (III) and cerium (IV) present on the surface of the nanoparticles of cerium oxide. decide. The end of the reaction can be judged by the point where the color change disappears. The reaction is usually completed in about 30 minutes to 1 hour.

For example, 47 μl of 0.5 M EDTA solution is added to 10 ml of 0.5 mass% polyvinyl imidazole aqueous solution, 200 μl of 10 mass% cerium nitrate (III) hexahydrate aqueous solution is added and mixed, and then 1 When 200 μl of a 2% by mass aqueous hydrogen hydrogen solution is added and stirred at 25 ° C., the solution first turns yellow, then gradually becomes darker yellow, and finally turns brown to complete the reaction.

After the reaction is completed, the pH of the dispersion may be adjusted. The pH may be adjusted in step A, or after purification of the dispersion liquid such as filtration with an ultrafiltration membrane described later or dialysis with a semipermeable membrane. The pH of the dispersion liquid of the present invention may be in the range of pH 2 to 12. The pH may be adjusted by adding a buffer solution, or may be adjusted by adding an acid such as nitric acid, sulfuric acid or hydrochloric acid, or a base such as sodium hydroxide or potassium hydroxide.

The zeta potential of the nanoparticles of cerium oxide of the present invention has a feature that it is higher than that using a polyvalent carboxylic acid as a stabilizer and smaller than that using a compound having a heterocyclic amine skeleton as a stabilizer. The zeta potential can be adjusted by the concentration of the polyvalent carboxylic acid and the compound having a heterocyclic amine skeleton, and if the concentration of the polyvalent carboxylic acid is increased, the data potential of the particles is small, and the compound having a heterocyclic amine skeleton Increasing the concentration increases the zeta potential of the particles.

The nanoparticles of cerium oxide of the present invention may be stored in the dispersion after the reaction is completed, or the nanoparticles of cerium oxide of the present invention may be taken out from the dispersion after the reaction and stored in a dried state. You may. When storing in dispersion, refrigerated storage is preferable. When drying the nanoparticles of cerium oxide of the present invention, first, the solution after completion of the reaction is filtered with an ultrafiltration membrane or dialyzed with a translucent membrane, and remains in the dispersion after completion of the reaction. The unreacted polyvalent carboxylic acid, oxidizing agent, cerium (III) ion and excess compound may be removed and dried using an evaporator or a freeze-dryer.

The ionic components that can be added to the dispersion of cerium oxide nanoparticles of the present invention after completion of the reaction include acetic acid, phthalic acid, succinic acid, carbonic acid, and Tris (hydroxymethyl) aminomethane (Tris) as components that impart buffering performance. , 2-Morphorinoethanesulphonic acid, monohydrate (MES), Bis (2-hydroxythyl) iminotris (hydroxymethyl) meshane (Biz-Tris), N- (2-Acetamido) imidoid -Ethanesulphonic acid (PIPES), N- (2-Acetamido) -2-aminoethanesulphonic acid (ACES), 2-Hydroxy-3-morpholinopropanesulphonic acid (MOPSO), N, N-Biz (2-thyro) acid (BES), 3-Morphorinopropanesulphonic acid (MOPS), N-Tris (hydroxymethyl) methyl-2-aminoethanesulfonic acid (TES), 2- [4- (2-Hydroxymethyl) -1-pipher) 2-Hydroxy-N-tris (hydroxymethyl) metyl-3-aminopropanesulphonic (TAPSO), Piperazine-1,4-bis (2-hydroxy-3-propanesulphonic acid (POPSO), 2-Hyd 2-hydroxythyl) -1-piperazinyl] propanesulphonic acid (HEPSO), 3- [4- (2-Hydroxythyl) -1-piperazinyl] propanesulphonic acid (HEPPS), (Trisyl), (Trisyl), (Trisyl) glycine (Bicine), N-Tris (hydroxymethyl) metyl-3-aminopropanesulphonic aci d (TAPS) can be mentioned, and sodium chloride and potassium chloride can be mentioned as components that do not impart buffering performance. These ionic components can be added so that the final concentration is in the range of 0.1 mM to 1 M. These ionic components may be added to the dispersion after the reaction is completed, may be added after filtering the dispersion with an ultrafiltration membrane, may be used as a dialysate, or may be added to the dispersion after dialysis. You may. It may be added to dried cerium oxide nanoparticles to form a dispersion.

The dispersion of cerium oxide nanoparticles of the present invention may be sterilized before use. Examples of the sterilization method include a method of passing through a sterilization filter.

In the present invention, antibacterial refers to suppressing the growth of microorganisms such as viruses, bacteria, and fungi in general, and kills microorganisms (killing of microorganisms), sterilizes them (removal of microorganisms), and sterilizes them. It includes bacteriostatic (microbiostasis), bactericidal (control of microbe) or growth inhibition (microbial inhibition).

The nanoparticles of cerium oxide of the present invention can be used as an antibacterial agent.
As a method for evaluating the performance as an antibacterial agent, for example, a method of mixing a microbial suspension and a test solution, culturing in an agar medium and observing the growth state, and observing suppression of growth in an agar medium containing the test solution. And the method of measuring the growth inhibition circle. Another method is to add a test solution to a liquid medium and measure the suppression of growth. In these evaluations, the medium component can contain a nutrient source such as glucose, peptone derived from milk casein or soybean, and an extract derived from fish meat or yeast in order to promote the growth of microorganisms. When antibacterial activity is observed, the growth state of microorganisms deteriorates in the region where the test solution is present on the agar medium, and the size and number of colonies decrease. Further, if it is in a liquid medium, the increase in turbidity due to the growth of microorganisms disappears. In the present invention, a method of adding a test solution to a liquid medium and observing suppression of growth is preferably used for evaluation of antibacterial activity.
The method of adding a test solution to a liquid medium to suppress the growth of microorganisms is used as an index of antibacterial activity as an effect of suppressing the growth of microorganisms. Specifically, the microbial growth inhibition rate of the nanoparticles of cerium oxide of the present invention is calculated as follows. First, a solution of nanoparticles of cerium oxide of the present invention is mixed with a liquid medium, and microorganisms such as Escherichia coli are inoculated. As a control, the same treatment is performed on a liquid medium containing no nanoparticles of cerium oxide. The turbidity (OD600 value) of the solution is measured before the start of culture. Cultivate the microorganisms at a predetermined temperature and time while stirring using a shaker or the like. After culturing, the turbidity (OD600 value) of all the solutions is measured. For each solution, take the difference between the turbidity after culturing and the turbidity before culturing. The difference between the turbidity difference (I _c ) of the control and the turbidity difference (I) of the solution containing the nanoparticles of cerium oxide is taken, and the _{ratio to the turbidity difference (I c} ) of the control is calculated as the growth inhibition rate.

Examples of the target microorganism in which the nanoparticles of cerium oxide of the present invention exhibit antibacterial activity include the following. Examples of the bacterium include Gram-positive bacteria and Gram-negative bacteria. Examples of gram-negative bacteria include Escherichia bacteria such as Escherichia coli, Salmonella bacteria such as Salmonella, Pseudomonas bacteria such as Shigella, Shigella bacteria such as Shigella, and Klebsiella such as Klebsiella pneumoniae. Bacteria of the genus Regionella such as Regionella pneumophylla can be mentioned. Examples of gram-positive bacteria include bacteria of the genus Staphylococcus such as Staphylococcus, bacteria of the genus Bacillus such as Bacillus subtilis, and bacteria of the genus Mycobacterium such as tuberculosis. Examples of fungi include fungi and yeast. Examples of fungi include filamentous fungi of the genus Aspergillus such as black stag beetle, filamentous fungi of the genus Penicillium such as blue mold, filamentous fungi of the genus Cladosporium such as black mold, filamentous fungi of the genus Alternaria such as suscabi, and trichoderma such as tucia okabi. Examples include filamentous fungi of the genus, filamentous fungi of the genus Ketomium such as Ketama mold. Examples of yeasts include yeasts of the genus Saccharomyces such as baker's yeast and beer yeast, and yeasts of the genus Candida such as Candida albicans. Examples of the virus include poliovirus, rotavirus, norovirus, enterovirus, sapovirus, influenza virus, RS virus, adenovirus, herpesvirus and the like. The nanoparticles of the present invention show particularly high antibacterial activity against bacteria.

By making the nanoparticles of cerium oxide of the present invention into a dispersion, for example, they can be added to pools, bathtubs, hot springs, etc. as disinfectants, or used as body soaps, hand-washing detergents, disinfectants, mouthwashes, mouthwashes, etc. It can be used or used as a disinfectant for cleaning clothes, tableware, kitchens, toilets, washrooms, bathrooms, desks, chairs, tables, beds, medical equipment, etc. At this time, the dispersion liquid of the nanoparticles of cerium oxide may contain other components having a sterilizing, sterilizing, sterilizing, bacteriostatic, bacteriostatic, and growth inhibitory action. Specifically, solvent components such as ethanol and isopropyl alcohol, oxidizing agent components such as hydrogen peroxide, povidone iodine and sodium hypochlorite, and surfactant components such as benzalkonium chloride, benzethonium chloride and alkylpolyaminoethylglycine are used. Can be mentioned.

In addition, the nanoparticles of cerium oxide of the present invention are added at the time of molding of fibers, tubes, beads, rubber, films, plastics and the like as additives for imparting antibacterial activity, or are applied to the surfaces thereof. Therefore, it can be used for antibacterial processing. Examples of the cerium oxide dispersion of the present invention that can be antibacterial processed include a drainage chrysanthemum crack cover for a kitchen sink, a drainage plug, a packing for fixing a window glass, a packing for fixing a mirror, a bathroom, and a washbasin. And kitchen waterproof packing, refrigerator door lining packing, bath mat, washbasin and chair non-slip rubber, hose, shower head, packing used for water purifier, plastic products of water purifier, packing used for washing machine, Washing machine plastic products, masks, medical caps, medical shoe covers, air conditioner filters, air purifier filters, vacuum cleaner filters, ventilation fan filters, vehicle filters, air conditioner filters, air conditioner fins, air conditioner blowouts Plastic parts such as mouth louvers and blower fans, car air conditioner fins, car air conditioner outlet louvers and other plastic parts, blower fans, clothing, bedding, nets for net doors, nets for chicken houses, nets such as mosquito shops, wallpapers Air conditioners, windows, blinds, interior materials for buildings such as hospitals, interior materials for trains and automobiles, seats for vehicles, blinds, chairs, sofas, equipment for handling viruses, doors, ceiling boards, floor boards, windows and other building materials. And so on. As described above, the product processed with the dispersion liquid of the nanoparticles of cerium oxide of the present invention can be used in various fields as a sanitary material.

Further, the cerium oxide nanoparticles of the present invention or a dispersion thereof can be used as an antiviral agent. As a method for evaluating the performance as an antiviral agent, the amount of virus is quantified after contacting or mixing the nanoparticles of cerium oxide of the present invention or a dispersion thereof with the virus. As a method for quantifying a virus, a method for measuring the amount of virus antigen by the ELISA method, a method for quantifying the viral nucleic acid by PCR, a method for measuring the infectious titer by the plaque method, and a method for measuring the infectious titer by the 50% infectious dose measuring method. The method etc. can be mentioned. In the present invention, as the antiviral performance, a method of measuring the infectious titer by a plaque method or a 50% infection amount measuring method is preferably used. In the 50% infectious dose measurement method, the unit of virus infectious titer is TCID ₅₀ (Tissue culture infectious dose 50) _{when tested on cultured cells, EID 50} (Egg infectious dose 50) when using hatched chicken eggs, and animals. Then, _{it is expressed by LD 50} (Lethal dose 50). Further, in the 50% infection amount measurement method, there are Reed-Muench method, Behrens-Kaeber method, Spearman-Karber method and the like as a method of calculating the infection titer from the obtained data, but in the present invention, the Reed-Muench method is used. Is preferable. The criteria for determining the antiviral performance are generally that the logarithmic reduction value of the infectious titer is 2.0 or more with respect to the infectious titer before the nanoparticle of cerium oxide of the present invention is allowed to act or the control containing no nanoparticles of the present invention. If so, the antiviral performance is determined to be effective.

The virus that can be inactivated by the nanoparticles of cerium oxide of the present invention or a dispersion thereof is, for example, rhinovirus, poliovirus, mouth-foot disease virus, rotavirus, norovirus, enterovirus, hepatvirus, astrovirus, sapovirus, hepatitis E virus. , A, B, C influenza virus, parainfluenza virus, mumps virus (Otafukukaze), measles virus, human metapneumovirus, RS virus, nipavirus, Hendra virus, yellow fever virus, dengue virus, Japanese encephalitis virus, West Nile virus, hepatitis B, C hepatitis virus, eastern and western horse encephalitis virus, onyonnyon virus, ruin virus, lassa virus, funin virus, machupo virus, guanaritovirus, savia virus, crimia congo hemorrhagic fever virus, snail Fever, Hunter virus, Shinnonbre virus, Mad dog disease virus, Ebola virus, Marburg virus, Bat morilissa virus, Human T-cell leukemia virus, Human immunodeficiency virus, Human corona virus, SARS corona virus, SARS corona virus 2, Human porbo Examples include viruses, polyomavirus, human papillomavirus, adenovirus, herpesvirus, varicella-like rash virus, EB virus, cytomegalovirus, natural pox virus, monkey pox virus, bovine pox virus, morasipox virus, parapox virus, etc. ..

When used as an antiviral agent, the nanoparticles of cerium oxide of the present invention or a dispersion thereof are kneaded into materials such as fibers, tubes, beads, rubber, films, and plastics as additives, or applied to the surface of these materials. It can be used as a rubber. For example, masks, medical caps, medical shoe covers, air conditioner filters, air conditioner filters, vacuum cleaner filters, ventilation fan filters, vehicle filters, air conditioner filters, air conditioner fins, air conditioner outlet louvers, etc. Plastic parts and blower fans, car air conditioner fins, car air conditioner outlet louvers and other plastic parts, blower fans, clothing, bedding, nets for net doors, chicken house nets, nets such as mosquito houses, wallpapers, windows, blinds , Various fields as interior materials for buildings such as hospitals, interior materials for trains and automobiles, seats for vehicles, blinds, chairs, sofas, equipment for handling viruses, doors, ceiling boards, floor boards, windows, etc. Can be used for.

The present invention will be described in more detail with reference to the following examples.
<Materials and methods>
Sodium polyacrylate and M9 Minimal Salts from Merck Co., Ltd., Poly (1-vinylimidazole) from Maruzen Petrochemical Co., Ltd., Cerium nitrate (III) hexahydrate and 30% by mass hydrogen peroxide solution from Fujifilm. Luria Broth Base was obtained from Thermo Fisher Co., Ltd., and Escherichia coli (DH5α) was obtained from Takara Bio Co., Ltd. and used.
Other reagents were purchased from Fujifilm Wako Pure Chemical Industries, Ltd., Tokyo Kasei Co., Ltd., and Sigma-Aldrich Japan GK, and used as they were without any particular purification.

In the following examples, as the polyamide having a heterocyclic amine skeleton in the main chain, a polymer (polyamide (1)) having (aminoethyl) piperazine and adipic acid as structural units, (aminoethyl) piperazine and bis (aminopropyl). ) A polymer having polyethylene glycol and adipic acid as structural units (polyamide (2)) was used, and these polymers were prepared with reference to JP-A-11-166121.

The LB liquid medium was prepared by dissolving Luria Bouillon Base at a concentration of 25 g / l and sterilizing it in an autoclave. M9 liquid medium was prepared by mixing sterile distilled water _{890ml, 10 × M9 Minimal Salts100ml,} 1M MgSO 4 1ml, 20% glucose 10 ml, a 1M CaCl ₂ 100 [mu] l.
Otsuka Electronics Co., Ltd.'s zeta potential / particle measurement system ELS-Z was used to measure the hydrodynamic diameter and zeta potential of cerium oxide nanoparticles, and Beckman Coulter's DU530 was used to measure the OD600 value. The shaker used was TAITEC BIO-SHAKER BR-40LF.

(Example 1) Synthesis of nanoparticles of cerium oxide coated with polyacrylic acid and poly (1-vinylimidazole) 5 ml of 1% by mass sodium polyacrylate aqueous solution and 5 ml of 1% by mass polyvinyl imidazole aqueous solution were mixed. 200 μl of a 10 mass% cerium nitrate (III) hexahydrate aqueous solution was added, and the mixture was stirred for 15 minutes. Then, 200 μl of a 1.2 mass% hydrogen peroxide aqueous solution was added, and the mixture was reacted at room temperature for 1 hour. The reaction solution was purified with a 30 kD ultrafiltration membrane to obtain an orange dispersion containing nanoparticles of cerium oxide.

(Example 2) Synthesis of nanoparticles of cerium oxide coated with polyacrylic acid and polyamide (1) In Example 1, a 1% by mass polyamide (1) aqueous solution was used instead of 5 ml of a 1% by mass polyvinyl imidazole aqueous solution. The reaction was carried out under the same conditions as in Example 1 except that the above was used to obtain an orange aqueous solution containing nanoparticles of cerium oxide.

(Example 3) Synthesis of nanoparticles of cerium oxide coated with polyacrylic acid and polyamide (2) In Example 1, a 1% by mass polyamide (2) aqueous solution was used instead of 5 ml of a 1% by mass polyvinyl imidazole aqueous solution. The reaction was carried out under the same conditions as in Example 1 except that the above was used to obtain an orange aqueous solution containing nanoparticles of cerium oxide.

(Example 4) Synthesis of nanoparticles of cerium oxide coated with EDTA and poly (1-vinylimidazole) To 10 ml of a 0.5 mass% polyvinyl imidazole aqueous solution, 47 μl of a 0.5 M EDTA / 2Na aqueous solution was added. 200 μl of a 10 mass% cerium nitrate (III) hexahydrate aqueous solution was added, and the mixture was stirred for 15 minutes. Then, 200 μl of a 1.2 mass% hydrogen peroxide aqueous solution was added, and the mixture was reacted at room temperature for 1 hour. The reaction solution was purified with a 30 kD ultrafiltration membrane to obtain a brown dispersion containing nanoparticles of cerium oxide.

(Example 5) Synthesis of EDTA and polyamide (1) -coated nanoparticles of cerium oxide In Example 4, 0.5% by mass of polyamide (1) was used instead of 10 ml of 0.5% by mass of polyvinyl imidazole aqueous solution. ) The reaction was carried out under the same conditions as in Example 4 except that the aqueous solution was used to obtain a brown aqueous solution containing nanoparticles of cerium oxide.

(Example 6) Synthesis of EDTA and polyamide (2) -coated nanoparticles of cerium oxide In Example 4, 0.5% by mass of polyamide (2) was used instead of 10 ml of 0.5% by mass of polyvinyl imidazole aqueous solution. ) The reaction was carried out under the same conditions as in Example 4 except that the aqueous solution was used to obtain a brown aqueous solution containing nanoparticles of cerium oxide.

(Example 7) Synthesis of nanoparticles of cerium oxide coated with polyacrylic acid and piperazine In Example 1, a 24.6 mg / 5 ml piperazine aqueous solution was used instead of 5 ml of a 1 mass% polyvinyl imidazole aqueous solution. The reaction was carried out under the same conditions as in Example 1 except that a yellow aqueous solution containing nanoparticles of cerium oxide was obtained.

(Example 8) Synthesis of nanoparticles of cerium oxide coated with polyacrylic acid and N- (2-aminoethyl) piperazin In Example 1, instead of 5 ml of 1 mass% polyvinyl imidazole aqueous solution, 20 mg / 5 ml The reaction was carried out under the same conditions as in Example 1 except that an N- (2-aminoethyl) piperazine aqueous solution was used to obtain a yellow aqueous solution containing nanoparticles of cerium oxide.

(Example 9) Synthesis of nanoparticles of cerium oxide coated with polyacrylic acid and 2- [4- (2-hydroxyethyl) -1-piperazinyl] ethanesulfonic acid In Example 1, 1% by mass of polyvinylimidazole The reaction was carried out under the same conditions as in Example 1 except that 36.8 mg / 5 ml of 2- [4- (2-hydroxyethyl) -1-piperazinyl] ethanesulfonic acid aqueous solution was used instead of 5 ml of the aqueous solution. , A yellow aqueous solution containing nanoparticles of cerium oxide was obtained.

(Example 10) Synthesis of nanoparticles of cerium oxide coated with polyacrylic acid and morpholine In Example 1, 27 mg / 5 ml of morpholine aqueous solution was used instead of 5 ml of 1 mass% polyvinyl imidazole aqueous solution. The reaction was carried out under the same conditions as in Example 1 to obtain a yellow aqueous solution containing nanoparticles of cerium oxide.

(Example 11) Synthesis of nanoparticles of cerium oxide coated with EDTA and piperazine In Example 4, a 24.6 mg / 10 ml piperazine aqueous solution was used instead of 10 ml of a 0.5 mass% polyvinyl imidazole aqueous solution. The reaction was carried out under the same conditions as in Example 4 except that a brown aqueous solution containing nanoparticles of cerium oxide was obtained.

(Example 12) Synthesis of nanoparticles of cerium oxide coated with polyacrylic acid and pyridine Except that in Example 1, a 12 mg / 5 ml piperazine aqueous solution was used instead of 5 ml of a 1 mass% polyvinyl imidazole aqueous solution. The reaction was carried out under the same conditions as in Example 1 to obtain a yellow aqueous solution containing nanoparticles of cerium oxide.

(Example 13) Synthesis of nanoparticles of cerium oxide coated with polyacrylic acid and imidazole In Example 1, a 10 mg / 5 ml imidazole aqueous solution was used instead of 5 ml of a 1 mass% polyvinyl imidazole aqueous solution. The reaction was carried out under the same conditions as in Example 1 to obtain a yellow aqueous solution containing nanoparticles of cerium oxide.

(Example 14) Synthesis of nanoparticles of cerium oxide coated with polyacrylic acid and benzimidazole In Example 1, an 18 mg / 5 ml benzimidazole aqueous solution was used instead of 5 ml of a 1 mass% polyvinyl imidazole aqueous solution. The reaction was carried out under the same conditions as in Example 1 except that a yellow aqueous solution containing nanoparticles of benzyloxide was obtained.

(Example 15) Synthesis of nanoparticles of cerium oxide coated with EDTA and pyridine Except that in Example 4, a 12 mg / 10 ml pyridine aqueous solution was used instead of 10 ml of a 0.5 mass% polyvinyl imidazole aqueous solution. The reaction was carried out under the same conditions as in Example 4 to obtain a brown aqueous solution containing nanoparticles of cerium oxide.

(Comparative Example 1) Synthesis of cerium oxide coated with polyacrylic acid With reference to Non-Patent Document 1, nanoparticles of cerium oxide were prepared for comparison of antibacterial activity.
To 10 ml of a 0.5 mass% sodium polyacrylate aqueous solution, 200 μl of a 10 mass% cerium (III) nitrate hexahydrate aqueous solution was added, and the mixture was stirred at room temperature for 5 minutes. Then, 200 μl of a 1.2% by mass hydrogen peroxide aqueous solution was added, and the mixture was heated to 40 ° C. and reacted for 1 hour. The reaction solution was purified with a 30 kD ultrafiltration membrane to obtain a yellow dispersion containing nanoparticles of cerium oxide.

(Comparative Example 2) Synthesis of EDTA-coated nanoparticles of cerium oxide In Comparative Example 1, 10 ml of a 2.35 mM EDTA / 2Na aqueous solution was used instead of 10 ml of a 0.5 mass% sodium polyacrylate aqueous solution. Except for this, the reaction was carried out under the same conditions as in Comparative Example 1 to obtain a brown dispersion containing nanoparticles of cerium oxide.

(Comparative Example 3) Synthesis of nanoparticles of cerium oxide coated with poly (1-vinylimidazole) In Comparative Example 1, 0.5% by mass was used instead of 10 ml of a 0.5% by mass sodium polyacrylate aqueous solution. The reaction was carried out under the same conditions as in Comparative Example 1 except that 10 ml of a poly (1-vinylimidazole) aqueous solution was used to obtain an orange dispersion containing nanoparticles of cerium oxide.

(Example 16) Measurement of hydrodynamic diameter of nanoparticles of cerium oxide Dynamic light scattering (DLS) is the hydrodynamic diameter of nanoparticles of cerium oxide prepared in Examples 1 to 15 and Comparative Examples 1 to 3. Measured by. The solvent at the time of measurement was M9 medium, and the average particle size of the hydrodynamic diameter was obtained by number conversion. The obtained values are shown in Table 1.
It was confirmed that the particles obtained in Examples 1 to 15 were nanoparticles having an average particle size of 3.3 to 18.2 nm. Further, it was confirmed that the particles obtained in Comparative Examples 1, 2 and 3 were nanoparticles having an average particle diameter of 5.0 nm, 3.0 nm and 12.4 nm, respectively.

(Example 17) Suppression of Escherichia coli growth of cerium oxide nanoparticles As an evaluation of the antibacterial activity of the cerium oxide nanoparticles of the present invention, evaluation of suppression of Escherichia coli growth was performed.
Solutions of nanoparticles of cerium oxide prepared in Examples 1 to 15 and Comparative Examples 1 and 2 were prepared at a concentration of 2 mg / ml, respectively, and passed through a 0.2 μm ultrafiltration membrane. The flow-through solution was used to evaluate the suppression of E. coli growth.
As a preculture, Escherichia coli was inoculated into an LB liquid medium and cultured at 32 ° C. for 24 hours while stirring at 200 rpm using a shaker. After culturing, the supernatant was removed by centrifugation (4000 rpm, 5 minutes), and the pellets of E. coli were washed with 2 ml of physiological saline. This wash was performed once more and the pellet was resuspended in 2 ml of M9 liquid medium.
9.5 ml of M9 liquid medium and 500 μl of a solution of 2 mg / ml cerium oxide nanoparticles were mixed, and 25 μl of the resuspended E. coli suspension was added. As a control, a solution in which physiological saline was added instead of a solution of nanoparticles of cerium oxide was also prepared. The cells were cultured at 32 ° C. for 24 hours with stirring at 200 rpm using a shaker, and the OD600 value was measured. The OD600 value of each solution at the start of culture was 0.033.
The analysis of the growth inhibition rate was performed by taking a difference of 0.033, which is an initial value, from the control after culturing and the OD600 value of each example. The difference between the OD600 value of the control and the OD600 value of each example was taken, and the ratio of the control to the OD600 value was calculated as the growth suppression rate. The results obtained are shown in Table 2.

Comparing Examples 1 to 15 with Comparative Examples 1 and 2 described later, the polyvalent carboxylic acid and the heterocyclic amine skeleton of the present invention are compared with the nanoparticles of cerium oxide coated only with the polyvalent carboxylic acid. It was clarified that the nanoparticles of cerium oxide whose surface was coated with the vinyl-based polymer or polyamide having the nanoparticles had a growth inhibition rate of 95% or more for all of the E. coli, and the antibacterial activity was greatly improved.

(Example 18) Virus inactivation of cerium oxide nanoparticles Virus in 0.9 ml of dispersion of cerium oxide nanoparticles prepared in Examples 1 to 15 and Comparative Examples 1 to 3 prepared to be 5 mg / ml. 0.1 ml of the solution (influenza virus, ATCC, VR-1679, Influenza A virus (H3N2)) was mixed and allowed to act for 1 hour. Then, PBS was added as an action-stopping solution to stop the action on the virus. The infectious titer was measured by a plaque measurement method using this solution as a stock solution of a sample for virus titer measurement.
Table 3 shows the logarithmic reduction value of the infectious titer with respect to the infectious titer before the nanoparticle of cerium oxide was allowed to act. From this result, it was found that the nanoparticles of cerium oxide of Comparative Examples 1 and 2 had no antiviral activity, and the nanoparticles of cerium oxide of Comparative Example 3 had antiviral activity. It was confirmed that the antiviral activity of the cerium oxide nanoparticles of Examples 1 to 15 was relatively higher than that of the cerium oxide nanoparticles of Comparative Example 3.

Claims

Cerium oxide nanoparticles whose surface is coated with a polyvalent carboxylic acid and a compound having a heterocyclic amine skeleton.
The cerium oxide nanoparticles according to claim 1, wherein the polyvalent carboxylic acid has a valence of trivalent or higher.
The cerium oxide nanoparticles according to claim 1 or 2, wherein the compound having a heterocyclic amine skeleton is a vinyl polymer or polyamide having a heterocyclic amine skeleton in the main chain or side chain.
The cerium oxide nanoparticles according to any one of claims 1 to 3, wherein the heterocyclic amine skeleton is composed of any of piperazine, pyridine, imidazole or carbazole.
The nanoparticles of cerium oxide according to claim 3 or 4, wherein the vinyl-based polymer is a polymer having the heterocyclic amine skeleton in the side chain.
The nanoparticles of cerium oxide according to claim 3 or 4, wherein the polyamide is a polymer having the heterocyclic amine skeleton in the main chain.
The cerium oxide according to claim 1 or 2, wherein the compound having a heterocyclic amine skeleton is a monocyclic or bicyclic aromatic heterocyclic compound having a 5-membered ring and / or a 6-membered ring structure. Nanoparticles.
The nanoparticles of cerium oxide according to claim 1 or 2, wherein the compound having a heterocyclic amine skeleton is a compound represented by the general formula (I).

(In the formula (I), X represents NR 2 , O, S, R 1 and R 2 are hydrogen atoms, an alkyl group having 1 to 4 carbon atoms, a hydroxyalkyl group having 1 to 4 carbon atoms, and 1 to 4 carbon atoms. It indicates an aminoalkyl group of 4 or an alkyl sulfonate group having 1 to 4 carbon atoms. R 1 and R 2 may be the same or different.)
An antibacterial agent containing nanoparticles of cerium oxide according to any one of claims 1 to 8.
An antiviral agent containing cerium oxide nanoparticles according to any one of claims 1 to 8.
A method for producing nanoparticles of cerium oxide whose surface is coated with a polyvalent carboxylic acid and a compound having a heterocyclic amine skeleton.
Step A to prepare a solution containing a polyvalent carboxylic acid, a compound having a heterocyclic amine skeleton, and cerium (III) ions, and step B to add an oxidizing agent to the solution obtained in the step A.
A method for producing nanoparticles of cerium oxide, including.