Polymer-coated magnetic metal particle and method for producing same

Abstract

Polymer-coated magnetic metal particles according to the present invention each comprise: a magnetic metal particle; a coating layer that is provided on the surface of the magnetic metal particle and that is formed of silicon oxide; and a polymer layer that is provided on the surface of the coating layer and that contains a polymer formed of a structural unit represented by formula (1) and an alkoxysilane having an acrylic group or a methacrylic group.

Description

Polymer-coated metal magnetic particles and their manufacturing method

[0001] The present invention relates to polymer-coated magnetic metal particles and a method for producing the same.

[0002] In the field of medical diagnosis, target substances such as various proteins, nucleic acids, and cells are often separated, collected, and tested from sample liquids such as blood. One method for this testing involves, for example, carrying a carrier substance suitable for each target substance on the surface of specific particles, capturing the target substance, and then recovering the particles for analysis.

[0003] Magnetic particles are sometimes used as particles for carrying a carrier substance. By using magnetic particles, the carrier substance can be carried, and after capturing a target substance, the target substance can be recovered by applying an external magnetic field.

[0004] As such magnetic particles, for example, magnetic polymer particles have been proposed in which the surface of a core polymer particle is sequentially coated with a coating layer containing a nanomagnetic material and silicon oxide, and a polymer layer capable of binding a carrier substance (see, for example, Patent Document 1).

[0005] Japanese Patent Application Laid-Open No. 2021-60339

[0006] From the viewpoint of improving test accuracy, it is important that the test particles described above have a large capacity to carry carrier substances capable of binding to target substances. Furthermore, the test particles are required to have high saturation magnetization and to collect in a short time when a magnetic field is applied, i.e., to have high magnetic collecting properties.

[0007] In this regard, even if the particles of Patent Document 1 mentioned above can achieve a high loading amount, the core is a polymer particle, so the saturation magnetization tends to be low, and the desired magnetic collection may not be achieved.

[0008] Therefore, an object of the present invention is to provide a technique for increasing the amount of carrier material capable of binding to a target substance and for increasing the magnetic attraction to a certain level or more.

[0009] A first aspect of the present invention is a polymer-coated metal magnetic particle comprising: a metal magnetic particle; a coating layer formed on the surface of the metal magnetic particle and composed of silicon oxide; and a polymer layer formed on the surface of the coating layer and containing a polymer of an alkoxysilane having a structural unit represented by formula (1) and an acrylic group or a methacrylic group. (In formula (1), R １ represents a hydrogen atom or a methyl group, and R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms; R ３ represents an alkylene group having 2 to 6 carbon atoms, a cyclohexylene group, or a phenylene group.

[0010] The second aspect of the present invention is the same as the first aspect, wherein in the formula (1), R ２ is an ethylene group, and R ３ is an alkylene group, a phenylene group, or a cyclohexylene group.

[0011] The third aspect of the present invention is the second aspect, wherein R in formula (1) ３ is a phenylene group.

[0012] A fourth aspect of the present invention is the compound according to any one of the first to third aspects, wherein the alkoxysilane has an acrylic group or a methacrylic group and an alkylene group having 3 to 6 carbon atoms.

[0013] A fifth aspect of the present invention is the fourth aspect, wherein the alkoxysilane has an acryloxypropyl group or a methacryloxypropyl group.

[0014] A sixth aspect of the present invention is any one of the first to fifth aspects, wherein the metal magnetic particles are iron particles or iron-based alloy particles.

[0015] A seventh aspect of the present invention is any one of the first to sixth aspects, wherein the saturation magnetization is 100 Am ２ / kg or more 210Am ２ / kg or less.

[0016] An eighth aspect of the present invention is any one of the first to seventh aspects, wherein the volume-based cumulative 50% particle size measured with a laser diffraction particle size distribution analyzer is 0.2 μm to 10 μm.

[0017] A ninth aspect of the present invention is any one of the first to eighth aspects, wherein the C amount is 0.5 mass % or more and 10 mass % or less.

[0018] A tenth aspect of the present invention is any one of the first to ninth aspects, wherein the C content is 0.1% by mass or more and 10% by mass or less.

[0019] An eleventh aspect of the present invention is a method for producing polymer-coated metal magnetic particles, comprising the steps of: forming a coating layer composed of silicon oxide on the surface of a metal magnetic particle; and mixing the metal magnetic particle with the coating layer formed thereon, water, and an alkoxysilane having an acrylic group or a methacrylic group, and then adding a compound represented by formula (2) and polymerizing to form a polymer layer on the coating layer. (In formula (2), R １ represents a hydrogen atom or a methyl group, and R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms; R ３ represents an alkylene group having 2 to 6 carbon atoms, a cyclohexylene group, or a phenylene group.

[0020] The twelfth aspect of the present invention is the eleventh aspect, wherein in the formula (2), R ２ is an ethylene group, and R ３ is an alkylene group, a phenylene group, or a cyclohexylene group.

[0021] The thirteenth aspect of the present invention is the twelfth aspect, wherein R in the formula (2) ３ is a phenylene group.

[0022] A fourteenth aspect of the present invention is the compound according to any one of the eleventh to thirteenth aspects, wherein the alkoxysilane has an acrylic group or a methacrylic group and an alkylene group having 3 to 6 carbon atoms.

[0023] A fifteenth aspect of the present invention is the fourteenth aspect, wherein the alkoxysilane has an acryloxypropyl group or a methacryloxypropyl group.

[0024] A sixteenth aspect of the present invention is any one of the eleventh to fifteenth aspects, wherein the metal magnetic particles are iron particles or iron-based alloy particles.

[0025] A seventeenth aspect of the present invention is the method according to any one of the eleventh to sixteenth aspects, wherein in the step of forming the polymer layer, a water-soluble azo polymerization initiator having a carboxyl group is used as the polymerization initiator.

[0026] In the test particles, the amount of carrier material capable of binding to the target substance can be increased, and the magnetic attraction can be made to be equal to or greater than a certain level.

[0027] One embodiment of the present invention will now be described with reference to a polymer-coated magnetic metal particle and a method for producing the same according to one embodiment of the present invention. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0028] (1) Polymer-coated metal magnetic particles The polymer-coated metal magnetic particles of this embodiment are configured by laminating a coating layer and a polymer layer in this order on the surface of a metal magnetic particle. Hereinafter, the polymer-coated metal magnetic particles are also referred to simply as test particles.

[0029] (Metallic Magnetic Particles) Metallic magnetic particles are the core of the test particles and are ferromagnetic particles made of a metal or alloy. Examples of metallic magnetic particles made of pure metal include iron particles, nickel particles, and cobalt particles, while examples of metallic magnetic particles made of an alloy include iron-based alloy particles. In this specification, iron-based alloy refers to an alloy containing 50% by mass or more of iron. Examples of iron-based alloy particles include Fe—B-based alloy particles, Fe—Si-based alloy particles, Fe—N-based alloy particles, Fe—Ni-based alloy particles, and Fe—C-based alloy particles. From the viewpoint of ensuring excellent saturation magnetization of the test particles, it is preferable to use iron particles or iron-based alloy particles as the metallic magnetic particles.

[0030] The particle diameter of the metal magnetic particles is preferably 0.2 μm to 10.0 μm. When test particles containing such metal magnetic particles are added to a sample solution, the test particles' own weight and buoyancy are balanced, achieving appropriate dispersibility in the sample solution. As a result, the adhesion of carrier substances to the test particles and the binding of target substances to the carrier substances can be more reliably achieved. Here, particle diameter refers to the cumulative 50% particle diameter on a volume basis measured using a laser diffraction particle size distribution analyzer. Hereinafter, particle diameter refers to a similarly measured value.

[0031] (Coating layer) The coating layer is formed on the surface of the metal magnetic particle and is made of silicon oxide. The coating layer coats the metal magnetic particle and acts to suppress the elution of metal components from the metal magnetic particle when the polymer layer is formed.

[0032] The thickness of the coating layer is not particularly limited, but if it is too thin, it may not be possible to uniformly cover the surface of the metal magnetic particles. Therefore, from the viewpoint of more reliably suppressing the elution of components from the metal magnetic particles during the formation of the polymer layer, the thickness of the coating layer is preferably 1 nm or more. On the other hand, if the coating layer is too thick, the magnetic properties of the test particles, such as saturation magnetization and coercive force, may decrease. Therefore, from the viewpoint of maintaining high magnetic properties, the thickness of the coating layer is preferably 80 nm or less. Note that the thickness of the coating layer can be measured, for example, by observing the cross section of the coating layer using a transmission electron microscope (TEM) or a scanning electron microscope (SEM) and measuring the average film thickness. Specifically, the average film thickness can be determined by taking a TEM or SEM photograph of the cross section and averaging 50 measurement points for any particle.

[0033] (Polymer Layer) The polymer layer is provided on the surface of the coating layer. The polymer layer contains a polymer of a structural unit represented by formula (1) and an alkoxysilane having an acrylic or methacrylic group, and is configured so as to be able to bind to a carrier substance that captures a target substance. Here, the target substance is, for example, a substance to be tested, such as a protein, nucleic acid, or cell contained in blood. The carrier substance is not particularly limited as long as it can capture the target substance, and can be changed appropriately depending on the type of target substance. Examples of the carrier substance that can be used include streptavidin, protein A, protein G, and antibodies.

[0034] In formula (1), R １ represents a hydrogen atom or a methyl group, and R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms; R ３ represents an alkylene group having 2 to 6 carbon atoms, a cyclohexylene group, or a phenylene group.

[0035] The polymer has a carboxyl group (—COOH group) at the end of the structural unit of formula (1), and is bonded to the carrier substance by the carboxyl group. ２ and R ３ The molecular chain is long and bulky. Therefore, the polymer easily binds to a carrier substance with a large molecular size, such as streptavidin. In other words, the polymer layer can increase the amount of carrier substance attached (carried) to its surface. ２ and R ３ With regard to the alkylene groups, when the number of carbon atoms in each of the alkylene groups is 1, the molecular chain becomes short, which is undesirable as there is a concern that the amount of support will be reduced, and when the number of carbon atoms in each of the alkylene groups is 7 or more, the hydrophobicity becomes high, which makes it difficult to carry out the polymerization reaction in the polymer layer formation step, which is undesirable as there is a concern that productivity will be reduced.

[0036] In the structural unit of formula (1), R ２ is an ethylene group, and R ３ is preferably an alkylene group or a phenylene group. ３It is more preferable that the structural unit is a phenylene group. Such a structural unit makes it possible to more stably form a polymer and more reliably increase the amount of the carrier substance supported.

[0037] The silane coupling agent for forming the polymer is not particularly limited as long as it is an alkoxysilane having an acrylic or methacrylic group so as to be polymerizable with the compound of formula (2). From the viewpoint of more reliably increasing the amount of carrier substance supported in the polymer layer, it is preferable that the silane coupling agent has a long molecular chain and a bulky chemical structure. Specifically, it is preferable that the silane coupling agent is an alkoxysilane having an acrylic or methacrylic group and an alkylene group having 3 to 6 carbon atoms. Furthermore, from the viewpoint of increasing the reactivity with the compound of formula (2) and more reliably polymerizing the polymer, it is preferable that the silane coupling agent has an acryloxypropyl group or a methacryloxypropyl group.

[0038] (C Amount) The amount of polymer contained in the test particles can be simply quantified as the C amount. The C amount of the test particles is preferably 0.1% by mass to 10% by mass, and may be 0.5% by mass to 10% by mass, from the viewpoint of ensuring high magnetic properties. If the C amount is excessively low, the surface of the coating layer cannot be uniformly covered with the polymer layer, and a high amount of carrier material cannot be maintained. On the other hand, if the C amount is excessively high, the proportion of magnetic components in the test particles decreases, and high magnetic properties cannot be maintained. In this regard, by keeping the C amount within the above range, a high level of balance between the amount of carrier material and magnetic properties can be achieved. The C amount indicates the content of carbon derived from the polymer layer per 100 parts by mass of the test particles (polymer-coated metal magnetic particles). The C amount can be measured, for example, using a carbon / sulfur analyzer, as described below in the Examples.

[0039] (Particle size) The particle size of the test particles is not particularly limited, but is preferably 0.2 μm to 10 μm. If the particle size is small, the volume of the magnetic particles also becomes small, which is undesirable because it becomes difficult to collect magnetic flux when a magnetic field is applied. Furthermore, if the particle size is too large, the test particles tend to settle in the solution, which is undesirable.

[0040] (Characteristics) The test particles of this embodiment are configured by laminating a coating layer and a polymer layer in this order on the surface of a metal magnetic particle as a core, which gives the test particles the following characteristics.

[0041] In the test particles, the polymer layer contains a polymer of a structural unit represented by formula (1) and an alkoxysilane having an acrylic or methacrylic group, and is easily bound to a carrier substance that captures a target substance. In other words, the test particles are configured to carry a large amount of carrier substance. Specifically, streptavidin is loaded onto the test particles as the carrier substance, and ALP-biotin (alkaline phosphatase-biotin) and a luminescent dye (e.g., Lumiphos Plus) are bound to 50 μg of the streptavidin-immobilized particles, and the luminescence intensity is measured. A calibration curve showing the correlation between luminescence intensity and ALP-biotin concentration is created, and the ALP-biotin concentration is calculated from the luminescence intensity to determine the amount of biotin bound. The test particles of this embodiment have a high amount of biotin bound and excellent carrier substance carrying capacity.

[0042] Furthermore, since the core of the test particle is a metal magnetic particle, the ratio of the magnetic component in the particle is higher than that of a magnetic polymer particle, for example, in which the core is a polymer particle and magnetic particles are attached to the periphery of the polymer particle. Therefore, the test particle has a high saturation magnetization. Specifically, the saturation magnetization of the test particle is 100 Am ２ The upper limit is not particularly limited, but is preferably 210 Am ２ / kg or less. Test particles having such saturation magnetization have high magnetic collecting properties, and the time required to recover the test particles by applying a magnetic field can be shortened. The method for measuring saturation magnetization will be described in detail in the Examples.

[0043] Furthermore, since the core of the test particles is a metal magnetic particle, the test particles are configured to have a lower coercive force than magnetic polymer particles. Specifically, the coercive force Hc of the test particles is preferably 20 Oe or less. The lower limit is not particularly limited, but is, for example, 3 Oe or more. Test particles having such a coercive force can improve the dispersibility of the particles.

[0044] (2) Method for Manufacturing Polymer-Coated Metal Magnetic Particles Next, a method for manufacturing polymer-coated metal magnetic particles will be described. The manufacturing method of this embodiment includes a preparation step, a coating layer formation step, and a polymer layer formation step. Each step will be described in detail below.

[0045] (Preparation Step) First, metal magnetic particles that will become cores are prepared. The saturation magnetization of the prepared metal magnetic particles is 100 Am ２ / kg or more 210Am ２ In order to ensure excellent saturation magnetization of the resulting particles for testing, it is preferable to use iron particles or iron-based alloy particles as the metal magnetic particles.

[0046] (Coating Layer Forming Step) Next, a coating layer made of silicon oxide is formed on the surface of the metal magnetic particles, for example, by a sol-gel method.

[0047] Specifically, metal magnetic particles are first added to a solvent containing water to obtain a slurry in which the metal magnetic particles are dispersed. Next, silicon alkoxide is added to this slurry while stirring it. The alkoxy groups of silicon alkoxide are hydrolyzed by the action of water to produce silanol derivatives. The amount of silicon alkoxide added is preferably 0.1 to 5.0 parts by mass in terms of Si mass per 100 parts by mass of metal magnetic particles. The silanol derivatives adhere to the surfaces of the metal magnetic particles to form a reaction layer. Next, after a predetermined time has passed since the addition of the silicon alkoxide, a hydrolysis catalyst is added to the solvent containing the slurry while stirring it. This hydrolyzes the alkoxy groups remaining in the silanol derivatives. The solvent is also heated along with the addition of the hydrolysis catalyst. The silanol derivatives are condensed or polymerized by heating to form a polysiloxane structure, and further heating produces silica (SiO ２ The solvent is then dried to obtain silica-coated particles in which a coating layer made of silicon oxide is formed on the surface of the metal magnetic particles.

[0048] As the silicon alkoxide, a conventionally known one can be used, for example, trimethoxysilane, tetramethoxysilane, triethoxysilane, tetraethoxysilane, tripropoxysilane, tetrapropoxysilane, tributoxysilane, tributoxysilane, etc.

[0049] As the hydrolysis catalyst, an alkaline catalyst is preferably used from the viewpoint of suppressing dissolution of the metal components that make up the metal magnetic particles. As the alkaline catalyst, for example, ammonia water can be used.

[0050] The amounts of silicon alkoxide and hydrolysis catalyst added, and the reaction times of the silicon alkoxide and hydrolysis catalyst may be appropriately adjusted depending on the thickness of the coating layer. For example, the thickness of the coating layer may be adjusted appropriately to be 1 nm to 80 nm. The heating temperature of the solvent containing the slurry may be set to, for example, 20°C to 70°C, from the viewpoint of the hydrolysis of the silicon alkoxide and the reactivity of the adhesion of the silanol derivative to the surface of the metal magnetic particles. The solvent may be water alone, or a mixed solvent containing water and an organic solvent.

[0051] (Polymer Layer Forming Step) Subsequently, a polymer layer is formed on the surface of the silica-coated particles.

[0052] Specifically, silica-coated particles are first mixed with a solvent containing water to prepare a dispersion. Then, while stirring this dispersion, an alkoxysilane having an acrylic or methacrylic group is added as a silane coupling agent and mixed. It is believed that the alkoxy group of the alkoxysilane is hydrolyzed by reaction with water, and bonds to the coating layer made of silicon oxide. After adding the silane coupling agent, a solution of preferably NaOH, NH ３After adding an alkali such as HCl to raise the pH of the solution to 8 or higher, the compound represented by formula (2) is added. The addition of this alkali has the effect of improving the reactivity of the silane coupling agent and the solubility of the compound of formula (2) in water. It is believed that a polymer layer is formed by bonding, starting from the silane coupling agent bound to the coating layer, to the acrylic or methacrylic group of the silane coupling agent and the acrylic or methacrylic group in the chemical structure of the compound of formula (2), or the acrylic or methacrylic group in an unbound silane coupling agent. The polymer constituting the polymer layer has a structural unit represented by formula (1) above and a chemical structure derived from the silane coupling agent.

[0053] In formula (2), R １ represents a hydrogen atom or a methyl group, and R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms; R ３ represents an alkylene group having 2 to 6 carbon atoms, a cyclohexylene group, or a phenylene group. ２ and R ３ With regard to the alkylene groups, if the number of carbon atoms in each is 1, the molecular chain will be short, which is undesirable as there is a concern that the amount of carrier substance supported will be reduced, and if the number of carbon atoms in each is 7 or more, it will be undesirable as there is a concern that the hydrophobicity will be increased, making it difficult to carry out the polymerization reaction and reducing productivity.

[0054] As the compound of formula (2), from the viewpoint of increasing the amount supported by enhancing the binding between the polymer layer and the carrier substance as well as the reactivity with the silane coupling agent, R ２ is an ethylene group, and R ３ is preferably an alkylene group or a phenylene group. From the viewpoint of further increasing the amount of the carrier substance supported on the polymer layer, as shown in the examples described later, R ３ is more preferably a phenylene group.

[0055] As the silane coupling agent, an alkoxysilane having an acrylic or methacrylic group is used so as to be polymerizable with the compound of formula (2). From the viewpoint of more reliably increasing the amount of carrier material supported in the polymer layer, it is preferable that the alkoxysilane has a long molecular chain and a bulky chemical structure, specifically, it is preferable that it has an acrylic or methacrylic group and an alkylene group having 3 to 6 carbon atoms. Furthermore, from the viewpoint of increasing the reactivity with the compound of formula (2) and more reliably polymerizing the polymer, it is preferable that the alkoxysilane has an acryloxypropyl group or a methacryloxypropyl group.

[0056] The amounts of the silane coupling agent and the compound of formula (2) added may be adjusted within a range that allows the formation of a polymer layer with the desired thickness. For example, the amount of the silane coupling agent added is preferably 0.1 to 40 parts by mass, more preferably 5.0 to 40 parts by mass, even more preferably 15 to 40 parts by mass, and may be 0.1 to 10 parts by mass, relative to 100 parts by mass of the metal magnetic particles on which the coating layer is formed. By adding 15 to 40 parts by mass of the silane coupling agent relative to 100 parts by mass of the metal magnetic particles on which the coating layer is formed, the storage stability of the metal magnetic particles can be improved. Furthermore, the amount of the compound of formula (2) added is preferably 100 to 700 parts by mass, and may be 100 to 500 parts by mass, relative to 100 parts by mass of the metal magnetic particles on which the coating layer is formed. Furthermore, the amount of the compound of formula (2) added is preferably 10 to 100 times the amount of the silane coupling agent added by mass. Here, storage stability refers to the stability of the carrier substance carried on the polymer-coated metal magnetic particles, allowing the carrier substance to remain carried without detachment even after the passage of time. Specifically, the retention rate α of the loading amount, which serves as an indicator of storage stability, is calculated as α = B / A × 100 [%], where A is the initial loading amount when the carrier substance is carried on the polymer-coated metal magnetic particles, and B is the loading amount after a predetermined time has passed. High storage stability indicates that the loading amount B after a predetermined time has passed does not vary significantly from the initial loading amount A. The retention rate α is not particularly limited, but it is preferable that it be, for example, 30% or more.

[0057] When forming the polymer, it is preferable to add a polymerization initiator after adding the compound of formula (2). The addition of the polymerization initiator can further promote bonding between the silane coupling agent and the compound of formula (2). From the viewpoint of reactivity, it is preferable to use a water-soluble azo polymerization initiator having a carboxyl group as the polymerization initiator. The amount of polymerization initiator added is preferably 10 parts by mass to 100 parts by mass per 100 parts by mass of the metal magnetic particles on which the coating layer is formed.

[0058] After the polymerization reaction is completed, the test particles having a polymer layer formed on the surface of the coating layer are collected from the solvent using, for example, a magnet and washed, thereby obtaining the test particles of this embodiment.

[0059] A method for measuring a target substance using the above-described test particles is, for example, as follows. First, a carrier substance is bound to the test particles to obtain carrier substance-immobilized particles. These carrier substance-immobilized particles are added to a sample solution. Next, the target substance contained in the sample solution is captured by the carrier substance-immobilized particles. After that, the carrier substance-immobilized particles dispersed in the sample solution are collected by magnetic attraction. Then, the target substance captured by the collected carrier substance-immobilized particles is measured by a conventionally known method.

[0060] Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments and can be modified in various ways without departing from the spirit of the present invention.

[0061] The present invention will now be described in more detail based on examples, but is not limited to these examples. In these examples, a coating layer and a polymer layer were formed on the surface of metal magnetic particles to produce polymer-coated metal magnetic particles.

[0062] Example 1 (1) Preparation of Polymer-Coated Metal Magnetic Particles First, carbonyl iron powder (manufactured by BASF, HS grade D50: 2.3 μm) was prepared as metal magnetic particles.

[0063] Subsequently, a coating layer composed of silicon oxide was formed on the surface of the carbonyl iron powder. Specifically, 5451 g of isopropyl alcohol and 820 g of pure water were first added to a 10 L reaction vessel and stirred in a nitrogen atmosphere. 1650 g of carbonyl iron powder (hereinafter also referred to as Fe particles) was added to this solution and stirred at 40 ° C. Next, 257.4 g of tetraethoxysilane (Wako Pure Chemical Industries, Ltd.) and 50 g of isopropyl alcohol were added and stirred for 5 minutes. Then, 567.3 g of 25% ammonia water was added over 90 minutes. Simultaneously with the start of the addition of ammonia water, the liquid pump was operated to send the liquid to a high-pressure homogenizer (manufactured by SMT Corporation, LAB1000). Simultaneously with the liquid transfer, the high-pressure homogenizer was set to a pressure of 150 bar and a dispersion treatment was performed. The reaction solution after the dispersion treatment was set to return to the 10 L reaction vessel. After the addition of ammonia water, the mixture was stirred for 60 minutes. The dispersion treatment was continued until the reaction was completed. The obtained slurry was filtered, and the cake was dried in nitrogen at 110°C. This yielded silica-coated particles in which a silicon oxide coating layer was formed on the surface of the carbonyl iron powder.

[0064] Next, a polymer layer was formed on the surface of the silica-coated particles. Specifically, 1.88 g of silica-coated particles (silica content: 0.04 g) and 30 g of pure water were mixed and subjected to ultrasonic treatment for 30 minutes. The ultrasonically treated suspension and 204.76 g of pure water were placed in a 300 mL separable beaker, and nitrogen gas was bubbled at 0.1 L / min for 30 minutes. The nitrogen gas flow path was changed from bubbling into the liquid to flowing into the space above the liquid, and the mixture was stirred while heating to 35°C. After heating, 0.119 g of 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) represented by the following formula (3) was added as a silane coupling agent, and the mixture was stirred for 30 minutes. Furthermore, 6.67 g of 2-methacryloyloxyethyl phthalate (Tokyo Chemical Industry Co., Ltd.) shown in the following formula (4) as a compound (monomer) represented by formula (2) and 5 mL of 5 wt % aqueous sodium hydroxide solution were added and stirred for 30 minutes. The mixture was then heated to 65°C and stirred for another 30 minutes. 0.994 g of 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] n-hydrate (Wako Pure Chemical Industries, Ltd.) was dissolved in 5 g of pure water and added to the reaction vessel. After addition, the mixture was stirred for 4 hours. After the polymerization reaction was completed, the particles were collected with a magnet and the supernatant was removed. The particles were then redispersed in 50 g of pure water, collected with a magnet, and the supernatant was removed. This washing procedure from redispersion in pure water to removal of the supernatant was repeated four more times, and the resulting particles were dispersed in pure water. This resulted in a slurry in which the polymer-coated metal magnetic particles of Example 1 were dispersed.

[0065]

[0066]

[0067] The preparation conditions for Example 1 are shown in Table 1 below.

[0068]

[0069] (2) Evaluation The produced polymer-coated magnetic metal particles were evaluated for the amount of carrier material carried, the magnetic properties of saturation magnetization and coercive force, the carbon content, and the particle size by the following methods.

[0070] (Loading amount) The loading amount of the carrier substance was evaluated by the amount of biotin bound per unit mass of the test particles. In the following, EDC is 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide Hydrochloride manufactured by Tokyo Chemical Industry Co., Ltd., MES is 2-(N-morpholino)ethanesulfonic acid, NHS is N-Hydroxysuccinimide manufactured by Wako Pure Chemical Industries, Ltd., PBS is phosphate-buffered saline, TBS is Tris-buffered saline, and TBST is TBS containing Tween 20. First, the slurry in which the polymer-coated metal magnetic particles were dispersed was heated and dried to obtain polymer-coated metal magnetic particles. 1 mL of 0.01 mol / L MES buffer solution with an EDC concentration of 5 mg / mL was added to 1 mg of the obtained polymer-coated metal magnetic particles, and the mixture was stirred with a vortex mixer for 30 minutes. After stirring, the magnetic particles were separated using a magnet and washed three times with 1 mL of 0.01 mol / L MES buffer solution. Subsequently, 1 mL of 0.01 mol / L MES buffer solution with an NHS concentration of 0.8 mg / mL was added and stirred with a vortex mixer for 30 minutes. After stirring, the magnetic particles were separated using a magnet and washed three times with 1 mL of 0.01 mol / L MES buffer solution. Subsequently, 1 mL of 0.01 mol / L PBS buffer solution (pH 5.7) with a streptavidin (Wako Pure Chemical Industries, Ltd.) concentration of 0.2 mg / mL was added and stirred with a vortex mixer for 30 minutes. After stirring, the magnetic particles were separated using a magnet and washed three times with 1 mL of 0.01 mol / L PBS buffer solution, resulting in streptavidin-immobilized particles. Next, 100 μL of 1x TBS buffer solution containing 0.01 mg / mL ALP-Biotin (manufactured by Thermo Fisher Scientific) was added to 50 μg of streptavidin-immobilized particles, and the mixture was left to stand for 30 minutes. The particles were then separated using a magnet and washed three times with 200 μL of TBST buffer solution. The particles were then suspended in 50 μL of TBS and transferred to a well plate. 50 μL of Lumiphos plus (manufactured by Wako Pure Chemical Industries, Ltd.) was added as a luminescent dye. After 5 minutes, the luminescence intensity was measured using a microplate reader. A calibration curve between luminescence intensity and ALP-biotin concentration was then created, and the ALP-biotin concentration was calculated from the calibration curve, giving the amount of biotin bound.The amount of biotin bound per unit mass of test particles in Comparative Example 1, which will be described later, was set to 100, and the amount of biotin bound was calculated as a relative value. When this relative value is 130 or more, it is evaluated that the amount of biotin bound is large and the amount of carrier substance carried is large. Note that the luminescence intensity was measured using a microplate reader ("SH-9000Lab" manufactured by Corona Electric Co., Ltd.), and the measurement conditions were luminescence measurement and a gate time of 1.0 second.

[0071] (Storage Stability) Storage stability was evaluated using streptavidin-immobilized particles obtained using the above-described method for evaluating loading capacity. In this example, the initial biotin binding amount and the biotin binding amount after a predetermined time period were determined for the streptavidin-immobilized particles obtained using the above-described method for evaluating loading capacity, and their retention rates were calculated. Specifically, the calculated biotin binding amount for the streptavidin-immobilized particles obtained using the above-described method for evaluating loading capacity was used as the initial biotin binding amount. Meanwhile, the streptavidin-immobilized particles were left standing in an environment of 37°C for 4 days. After storage for the predetermined time, 100 μL of 1×TBS buffer solution containing 0.01 mg / mL ALP-Biotin (manufactured by Thermo Fisher Scientific) was added to 50 μg of streptavidin-immobilized particles and the particles were left standing for 30 minutes. The particles were then separated using a magnet and washed three times with 200 μL of TBST buffer solution. The suspension was then suspended in 50 μL of TBS and transferred to a well plate. 50 μL of Lumiphos plus (Wako Pure Chemical Industries, Ltd.) was added as a luminescent dye. After 5 minutes, the luminescence intensity was measured using a microplate reader. A calibration curve of luminescence intensity versus ALP-biotin concentration was then prepared, and the ALP-biotin concentration was calculated from the calibration curve to determine the amount of biotin bound. This amount of biotin bound was taken as the amount of biotin bound after 4 days at 37°C. The storage stability was then evaluated based on the retention rate calculated using the following formula. In this example, a retention rate of 30% or higher was considered to be excellent in storage stability. (Retention rate [%]) = (amount of biotin bound after 4 days at 37°C) / (initial amount of biotin bound) × 100

[0072] (Magnetic Properties) The slurry in which the polymer-coated metal magnetic particles were dispersed was heated and dried to obtain polymer-coated metal magnetic particles. The obtained polymer-coated metal magnetic particles were measured using a vibrating sample magnetometer (VSM) (VSM-5 manufactured by Toei Kogyo Co., Ltd.) in an applied magnetic field of 798 kA / m (10 kOe) with an M measurement range of 0.05 A m ２ The magnetic properties of saturation magnetization and coercive force were measured at a magnetic field of 50 emu, a time constant of 0.03 seconds, and a wait time of 0.1 seconds. The attached software (Ver. 2.1) manufactured by Toei Kogyo Co., Ltd. was used for this measurement. In this example, the saturation magnetization was 100 Am ２ If the coercive force is 20 Oe or less, the polymer-coated metal magnetic particles can be collected in a short time when a magnetic field is applied, and the magnetic particles are judged to have excellent magnetic collection properties. If the coercive force is 20 Oe or less, the polymer-coated metal magnetic particles disperse in a short time when removed from the magnetic field, and the magnetic particles are judged to have excellent dispersibility. In Table 1, the coercive force Hc is shown in both units [Oe] and [kA / m].

[0073] The polymer-coated magnetic metal particles were dispersed in a slurry, which was then heated and dried to obtain the polymer-coated magnetic metal particles. The carbon content of the resulting polymer-coated magnetic metal particles was measured using a carbon / sulfur analyzer (EMIA-920V2 manufactured by Horiba, Ltd.).

[0074] (Particle diameter) The particle diameter of the polymer-coated metal magnetic particles was determined by measuring the particle size distribution of a slurry in which the polymer-coated metal magnetic particles were dispersed using a laser diffraction / scattering particle size distribution measuring device (SYNC manufactured by Microtrac Bell Co., Ltd.), and determining the cumulative 50% diameter D50 (unit: μm) based on the obtained volume-based particle size distribution.

[0075] (3) Evaluation Results The evaluation results are summarized in Table 2.

[0076]

[0077] As shown in Table 2, the polymer-coated metal magnetic particles of Example 1 had a D50 of 2.2 μm, a biotin binding amount of 303, and a saturation magnetization of 197 Am. ２ / kg, coercive force Hc of 5 Oe, and C content of 3%. That is, it was confirmed that Example 1 had a large amount of carrier material carried, high saturation magnetization and excellent magnetic collection, and low coercive force and excellent magnetic separation. When the thickness of the coating layer was observed with a transmission electron microscope, it was confirmed that the thickness was in the range of 1 nm to 80 nm.

[0078] The increased loading amount was achieved by forming the polymer layer using an alkoxysilane having an acrylic or methacrylic group and 2-methacryloyloxyethyl phthalic acid as the compound of formula (2). In Example 1, the polymer forming the polymer layer is derived from 2-methacryloyloxyethyl phthalic acid and is configured to include a structural unit satisfying formula (1) and a structural unit derived from a specific alkoxysilane. The structural unit derived from 2-methacryloyloxyethyl phthalic acid has a long molecular chain due to an ethyl group, a methacrylic group, and a phenylene group. Therefore, the polymer layer easily binds streptavidin, allowing for an increased loading amount. Furthermore, in Example 1, the core was made of Fe particles, which is believed to have increased saturation magnetization and improved magnetic collection, while lowering coercive force and improving magnetic separation. Furthermore, the amount of C derived from the polymer layer was 0.5% by mass to 10% by mass, and the polymer layer was formed to an appropriate thickness, which is believed to have enabled both loading amount and magnetic properties to be achieved.

[0079] Furthermore, the polymer-coated metal magnetic particles of Example 1 were confirmed to have a high retention rate of 37% and excellent storage stability. This is thought to be because the polymer layer was able to be formed uniformly on the coating layer by adding 5.0 to 40 parts by mass of the silane coupling agent relative to 100 parts by mass of the metal magnetic particles on which the coating layer was formed, and by adding 100 to 500 parts by mass of the compound of formula (2) relative to 100 parts by mass of the metal magnetic particles on which the coating layer was formed.

[0080] (Examples 2 to 5) In Examples 2 to 5, polymer-coated metal magnetic particles were prepared in the same manner as in Example 1, except that the types of alkoxysilane, compound of formula (2), and metal magnetic particles were appropriately changed as shown in Table 1.

[0081] As the alkoxysilane, 3-acryloxypropyltrimethoxysilane shown in the following formula (5) was used.

[0082]

[0083] As the compound of formula (2), 2-acryloyloxyethyl succinic acid shown in the following formula (6) was used.

[0084]

[0085] As the metal magnetic particles, Fe—B alloy particles or Fe—Ni alloy particles were used. The Fe—B alloy particles were prepared as follows: First, iron chloride (FeCl ２ 11.3 g of ammonium chloride, 15.9 g of ammonium chloride, and 62.3 g of sodium gluconate were dissolved in 285.7 g of water at 30°C. Subsequently, 28.2 g of 25% aqueous ammonia was added, and the pH of the raw solution was adjusted to 9. The liquid temperature was then adjusted to 50°C, and a solution of 214.2 g of water and 21.7 g of sodium borohydride was added while stirring at 300 rpm, and the mixture was aged for 10 minutes. The resulting particles were collected with a magnet and washed with ethanol to obtain Fe—B alloy particles. The boron content was 9.2 wt%. The Fe—Ni alloy particles used were particles with an Fe content of 50% and a Ni content of 50%.

[0086] The polymer-coated metal magnetic particles of Examples 2 to 5 were evaluated in the same manner as in Example 1. As a result, as shown in Table 2, it was confirmed that Examples 2 to 5 had a large amount of biotin bound, a high saturation magnetization, and a low coercive force, just like Example 1. It was also confirmed that Examples 2 to 5 had similar coating layer thicknesses and storage stability to Example 1.

[0087] Furthermore, in Examples 1 to 5, an alkoxysilane having an acrylic or methacrylic group and an alkylene group having 3 to 6 carbon atoms was used as the silane coupling agent. Specifically, an alkoxysilane having an acryloxypropyl group or a methacryloxypropyl group was used, and it was confirmed that the amount of support on the polymer-coated metal magnetic particles could be further increased.

[0088] In addition, when Examples 1 to 5 are compared, the compound of formula (2) is R ３ In Examples 1, 3, and 4, in which the phthalic acid of formula (4) in which R is a phenylene group was used, ３ It was confirmed that the amount of biotin bound could be made higher than in Examples 2 and 5, which used succinic acid of formula (6) in which is an alkylene group. From this, it is thought that by introducing a bulkier chemical structure into the polymer layer, the amount of streptavidin carried can be increased, and as a result, more biotin can be captured.

[0089] (Comparative Examples 1 to 5) In Comparative Examples 1 to 5, polymer-coated metal magnetic particles were prepared in the same manner as in Example 1, except that the type of alkoxysilane was changed to the compounds of the following formulas (7) to (8), and the type of compound of formula (2) was changed to the compounds of the following formulas (9) to (11), as shown in Table 1. Formula (7) represents trimethoxy-4-vinylphenylsilane, and formula (8) represents triethoxyvinylsilane. Formula (9) represents styrene, formula (10) represents 2-carboxyethyl acrylate, and formula (11) represents 4-vinylbenzoic acid. The polymer-coated metal magnetic particles of Comparative Examples 1 to 5 were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0090]

[0091]

[0092]

[0093]

[0094]

[0095] As shown in Table 2, in Comparative Examples 1 to 3, the saturation magnetization was high and the coercive force was low, but it was confirmed that the amount of biotin bound was lower compared to Examples 1 to 5. This is because styrene, 2-carboxyethyl acrylate, and 4-vinylbenzoic acid were used in forming the polymer layer, instead of a compound satisfying formula (2). It is presumed that in Comparative Examples 1 to 3, unlike Examples 1 to 5, the molecular chains were long in the polymer layer, making it impossible to introduce a bulky chemical structure, and therefore, efficient binding with streptavidin was not possible.

[0096] Furthermore, as shown in Table 2, it was confirmed that Comparative Examples 4 and 5 tended to have lower biotin binding amounts and lower magnetic properties compared to Examples 1 to 5. This is because, in forming the polymer layer, an alkoxysilane having an acrylic or methacrylic group was not used as the silane coupling agent, and instead, trimethoxy-4-vinylphenylsilane or triethoxyvinylsilane, which do not have an acrylic or methacrylic group, were used. This is presumably because, in Comparative Examples 4 and 5, the polymer layer could not be configured to facilitate binding of streptavidin, and the C content could not be configured to be 0.5% by mass to 10% by mass. Note that, since the biotin binding amounts were low in Comparative Examples 1 to 5, storage stability was not evaluated.

[0097] (Examples 6 to 16) In Examples 6 to 16, polymer-coated metal magnetic particles were prepared in the same manner as in Example 1, except that the types of alkoxysilane (silane coupling agent), compound of formula (2), and metal magnetic particles were changed as appropriate, as shown in Table 3. The prepared polymer-coated metal magnetic particles were then evaluated in the same manner as in Example 1. The evaluation results for Examples 6 to 16 are summarized in Table 4.

[0098] As the alkoxysilane, 3-methacryloxypropylmethyldimethoxysilane shown in the following formula (12) or 3-methacryloxypropylmethyldiethoxysilane shown in the following formula (13) was used.

[0099]

[0100]

[0101] As the compound of formula (2), 2-methacryloyloxyethyl succinic acid shown in formula (14) below, 2-acryloyloxyethyl phthalic acid shown in formula (15) below, and 2-acryloyloxyethyl hexahydrophthalic acid shown in formula (16) below were used.

[0102]

[0103]

[0104]

[0105]

[0106] In Example 6, similar to Example 5, a silicon oxide coating layer was formed on the surface of Fe—Ni alloy particles containing 50% Fe and 50% Ni, thereby obtaining silica-coated particles. Subsequently, a polymer layer was formed on the surface of the silica-coated particles. Specifically, 8.00 g of silica-coated particles (silica content: 0.16 g) were mixed with 40 g of pure water and subjected to ultrasonic treatment for 10 minutes. The ultrasonically treated suspension and 488.63 g of pure water were placed in a 1 L beaker and bubbled with nitrogen gas at 0.1 L / min for 30 minutes. The nitrogen gas flow path was changed from bubbling into the liquid to flowing into the overhead space above the liquid, and the mixture was stirred while heating to 35°C. After heating, 1.61 g of 3-methacryloxypropylmethyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) represented by the above formula (12) was added as a silane coupling agent and stirred for 30 minutes. Furthermore, 44.94 g of 2-methacryloyloxyethyl phthalate (Tokyo Chemical Industry Co., Ltd.) shown in formula (15) above, a compound (monomer) represented by formula (2), was dissolved in 150 g of pure water and 70 g of 10 wt % aqueous sodium hydroxide solution, and the solution was added to a reaction vessel and stirred for 30 minutes. The mixture was then heated to 65°C and stirred for an additional 30 minutes. 6.69 g of 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] n-hydrate (Wako Pure Chemical Industries, Ltd.) was dissolved in 30 g of pure water and added to the reaction vessel. After addition, the mixture was stirred for 4 hours. After the polymerization reaction was completed, the particles were collected with a magnet and the supernatant was removed. The particles were then redispersed in 200 g of pure water, and the supernatant was removed. This washing procedure, from redispersion in pure water to removal of the supernatant, was repeated four more times, and the resulting particles were dispersed in pure water. As a result, a slurry in which the polymer-coated magnetic metal particles of Example 6 were dispersed was obtained.

[0107] In Examples 7 to 9, polymer-coated metal magnetic particles were prepared in the same manner as in Example 6, except that the type of compound (monomer) represented by formula (2) was changed appropriately as shown in Table 3.

[0108] In Example 10, a polymer layer was formed on the surface of silica-coated particles prepared in the same manner as in Example 1. Specifically, 8.00 g of silica-coated particles (silica content: 0.16 g) and 40 g of pure water were mixed and subjected to ultrasonic treatment for 10 minutes. The ultrasonically treated suspension and 517.94 g of pure water were placed in a 1 L beaker, and nitrogen gas was bubbled at 0.1 L / min for 30 minutes. The nitrogen gas flow path was changed from bubbling into the liquid to flowing into the space above the liquid, and the mixture was stirred while heating to 35°C. After heating, 1.84 g of 3-methacryloxypropylmethyldimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) represented by the above formula (12) was added as a silane coupling agent, and the mixture was stirred for 30 minutes. Furthermore, 30.8 g of 2-methacryloyloxyethyl phthalate (Tokyo Chemical Industry Co., Ltd.) represented by the above formula (15) as a compound (monomer) represented by formula (2) was dissolved in 150 g of pure water and 55 g of 10 wt % aqueous sodium hydroxide solution, and the solution was added to a reaction vessel and stirred for 30 minutes. The mixture was then heated to 65°C and stirred for an additional 30 minutes. 4.59 g of 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] n-hydrate (Wako Pure Chemical Industries, Ltd.) was dissolved in 20 g of pure water and added to the reaction vessel. After addition, the mixture was stirred for 4 hours. After the polymerization reaction was completed, the particles were collected with a magnet and the supernatant was removed. The particles were then redispersed in 200 g of pure water, and the supernatant was removed. This washing procedure, from redispersion in pure water to removal of the supernatant, was repeated four more times, and the resulting particles were dispersed in pure water. This resulted in a slurry in which the polymer-coated magnetic metal particles of Example 10 were dispersed.

[0109] In Examples 11 to 14, polymer-coated metal magnetic particles were prepared in the same manner as in Example 10, except that the type of compound (monomer) represented by formula (2) was changed appropriately as shown in Table 3.

[0110] In Example 15, as shown in Table 3, polymer-coated metal magnetic particles were prepared in the same manner as in Example 10, except that when forming the polymer layer, the silane coupling agent was changed to 2.05 g of 3-methacryloxypropylmethyldiethoxysilane shown in formula (13) above.

[0111] In Example 16, as shown in Table 3, polymer-coated metal magnetic particles were prepared in the same manner as in Example 10, except that the silane coupling agent used when forming the polymer layer was changed to 1.85 g of 3-acryloxypropyltrimethoxysilane shown in formula (5) above.

[0112]

[0113] As shown in Table 4, it was confirmed that in Examples 6 to 9, the amount of biotin bound was large, the saturation magnetization was high, and the coercive force was low, similar to Example 5. It was also confirmed that in Examples 10 to 16, the amount of biotin bound was large, the saturation magnetization was high, and the coercive force was low, similar to Example 1. It was also confirmed that in Examples 6 to 16, the thickness of the coating layer was equivalent to that of Example 1.

[0114] Furthermore, it was confirmed that Examples 6 to 16 had a higher retention rate of the supported amount and were excellent in storage stability compared to Examples 1 to 5. This is presumably because in Example 6 and the like, the amount of silane coupling agent added was greater than in Example 1, allowing a thicker and more uniform polymer layer to be formed on the coating layer.

[0115] As described above, in the polymer-coated metal magnetic particles, by configuring the polymer layer to contain a polymer of the structural unit represented by formula (1) and an alkoxysilane having an acrylic or methacrylic group, it is easy to bind a carrier substance capable of capturing the target substance to be tested, such as streptavidin, and the amount of the carrier substance can be increased. Furthermore, by using a metal magnetic particle as the core, the proportion of magnetic metal in the polymer-coated metal magnetic particles can be increased, and their magnetic collection and magnetic separation properties can be improved.

Claims

1. A polymer-coated metal magnetic particle comprising: a metal magnetic particle; a coating layer provided on the surface of the metal magnetic particle and composed of a silicon oxide; and a polymer layer provided on the surface of the coating layer and containing a polymer of a structural unit represented by the formula (1) and an alkoxysilane having an acrylic group or a methacrylic group. (In the formula (1), R １ represents a hydrogen atom or a methyl group, and R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms, and R ３ represents an alkylene group having 2 to 6 carbon atoms, a cyclohexylene group, or a phenylene group.) 2. In the formula (1), R ２ is an ethylene group, and R ３ is an alkylene group, a phenylene group or a cyclohexylene group. The polymer-coated metal magnetic particles according to claim 1.

3. R in the formula (1) ３ is a phenylene group, and the polymer-coated metal magnetic particle according to claim 2.

4. The polymer-coated metal magnetic particles according to claim 1 or 2, wherein the alkoxysilane has an acrylic group or a methacrylic group and an alkylene group having 3 to 6 carbon atoms.

5. The polymer-coated metal magnetic particles according to claim 4, wherein the alkoxysilane has an acryloxypropyl group or a methacryloxypropyl group.

6. The polymer-coated metal magnetic particles according to claim 1 or 2, wherein the metal magnetic particles are iron particles or iron-based alloy particles.

7. The saturation magnetization is 100 A·m ２ / kg or more and 210 A·m ２ / kg or less. The polymer-coated metal magnetic particles according to claim 1 or 2.

8. The polymer-coated metal magnetic particles according to claim 1 or 2, wherein the volume-based cumulative 50% particle diameter measured by a laser diffraction particle size distribution measuring device is 0.2 μm to 10 μm.

9. The polymer-coated metal magnetic particles according to claim 1 or 2, wherein the C content is 0.5% by mass or more and 10% by mass or less.

10. The polymer-coated metal magnetic particles according to claim 1 or 2, wherein the C content is 0.1% by mass or more and 10% by mass or less.

11. A method for producing polymer-coated metal magnetic particles, comprising: a step of forming a coating layer composed of silicon oxide on the surface of the metal magnetic particles; and a step of forming a polymer layer on the coating layer by adding and polymerizing a compound represented by the formula (2) after mixing the metal magnetic particles having the coating layer, water, and an alkoxysilane having an acrylic group or a methacrylic group. A method for producing polymer-coated metal magnetic particles. (In the formula (2), R １ represents a hydrogen atom or a methyl group, and R ２ represents a linear or branched alkylene group having 2 to 6 carbon atoms, and R ３ represents an alkylene group having 2 to 6 carbon atoms, a cyclohexylene group, or a phenylene group.) 12. In the formula (2), R ２ is an ethylene group, and R ３ is an alkylene group, a phenylene group or a cyclohexylene group. The method for producing a polymer-coated metal magnetic particle according to claim 11.

13. R in the formula (2) ３ The method for producing a polymer-coated metal magnetic particle according to claim 12, wherein is a phenylene group.

14. The method for producing polymer-coated metal magnetic particles according to claim 11 or 12, wherein the alkoxysilane has an acrylic group or a methacrylic group and an alkylene group having 3 to 6 carbon atoms.

15. The method for producing polymer-coated metal magnetic particles according to claim 14, wherein the alkoxysilane has an acryloxypropyl group or a methacryloxypropyl group.

16. The method for producing polymer-coated metal magnetic particles according to claim 11 or 12, wherein the metal magnetic particles are iron particles or iron-based alloy particles.

17. The method for producing polymer-coated metal magnetic particles according to claim 11 or 12, wherein in the step of forming the polymer layer, a water-soluble azo polymerization initiator having a carboxyl group is used as the polymerization initiator.

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