JP7513345B2 - Magnetic particles and test agents - Google Patents

Description

The present invention relates to magnetic particles containing a magnetic material. The present invention also relates to a test drug using the magnetic particles.

In fields such as pharmaceutical research and development and clinical testing, magnetic particles are used to measure the concentration of target substances in samples. For example, in immunoassays such as chemiluminescence immunoassay (CLIA), magnetic particles having antibodies or antigens on their surfaces are widely used. These magnetic particles are generally bound to the target substance, such as antigens or antibodies, and then attracted by a magnet or the like.

Conventionally, magnetic particles having a magnetic material inside a resin particle (see, for example, Patent Documents 1 and 2) and magnetic particles having a magnetic layer formed on the outer surface of a resin particle (see, for example, Patent Document 3) have been used as magnetic particles.

WO2004/056895A1 Japanese Patent Application Laid-Open No. 59-500691 Japanese Patent Application Laid-Open No. 07-063761

In conventional magnetic particles that have a magnetic material inside the resin particles or that have a magnetic layer on the outer surface of the resin particles, it is difficult to sufficiently increase the content of the magnetic material in the magnetic particles. Therefore, conventional magnetic particles may have low magnetic collection.

In addition, with conventional magnetic particles, the magnetic material can oxidize, causing a decrease in magnetic attraction over time.

Additionally, conventional magnetic particles can sometimes have poor dispersibility.

When magnetic particles with low magnetic collection properties are used, many magnetic particles cannot be collected by the magnet, which may reduce the measurement accuracy and sensitivity when measuring the concentration of target substances such as antibodies and antigens. Furthermore, when magnetic particles with low dispersibility are used, the magnetic particles may not be sufficiently redispersed after magnetic separation, which may reduce the measurement accuracy, measurement sensitivity, and measurement reproducibility.

The object of the present invention is to provide magnetic particles that can enhance magnetic collection and dispersibility and can maintain high magnetic collection. A limited object of the present invention is to provide magnetic particles that can maintain high magnetic collection for a long period of time. Another object of the present invention is to provide a test agent using the above magnetic particles.

According to a broad aspect of the present invention, there is provided a magnetic particle used for specifically interacting with a target substance, the magnetic particle comprising a magnetic-encapsulated resin particle containing a first magnetic body therein, a magnetic layer disposed on the outer surface of the magnetic-encapsulated resin particle and containing a second magnetic body, and a substance supported on the outer surface side of the magnetic layer and interacting specifically with the target substance.

In a particular aspect of the magnetic particles of the present invention, the first magnetic body is a metal or a metal oxide, and the second magnetic body is a metal or a metal oxide.

In a particular aspect of the magnetic particle of the present invention, the particle further comprises a shell layer disposed on the outer surface of the magnetic layer, the material of the shell layer comprising an inorganic oxide or an organic polymer, and the shell layer is bonded to the substance.

In a particular aspect of the magnetic particles of the present invention, the material of the shell layer comprises the inorganic oxide, which is an inorganic oxide having silicon atoms, germanium atoms, titanium atoms or zirconium atoms.

In a particular aspect of the magnetic particles of the present invention, the substance is an antigen or an antibody.

In a particular aspect of the magnetic particles of the present invention, the substance is avidin or streptavidin.

In a particular aspect of the magnetic particles of the present invention, the total content of the first magnetic body and the second magnetic body in 100 volume percent of the magnetic particles is 10 weight percent or more and 95 weight percent or less.

In a particular aspect of the magnetic particles of the present invention, the content of the first magnetic body is 10% by weight or more and 90% by weight or less, out of a total content of the first magnetic body and the second magnetic body of 100% by weight.

In a particular aspect of the magnetic particles of the present invention, the ratio of the content of the first magnetic material in 100 volume % of the region extending from the outer surface of the magnetic encapsulated resin particle toward the center to 1/3 of the thickness to the content of the first magnetic material in 100 volume % of the region extending from the center of the magnetic encapsulated resin particle toward the outer surface to 2/3 of the thickness is 0.8 or more and 4.0 or less.

In a particular aspect of the magnetic particles of the present invention, the magnetic particles are used as a test agent.

According to a broad aspect of the present invention, there is provided a test agent comprising the magnetic particles described above.

The magnetic particles according to the present invention are used to specifically interact with a target substance. The magnetic particles according to the present invention comprise magnetic body-encapsulated resin particles containing a first magnetic body therein, a magnetic layer that is disposed on the outer surface of the magnetic body-encapsulated resin particles and contains a second magnetic body, and a substance that is supported on the outer surface side of the magnetic layer and specifically interacts with the target substance. The magnetic particles according to the present invention have the above-mentioned configuration, and therefore can increase magnetic collection and dispersibility, and can maintain high magnetic collection.

FIG. 1 is a cross-sectional view illustrating a magnetic particle according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view showing a schematic diagram of a magnetic particle according to a second embodiment of the present invention. FIG. 3 is a cross-sectional view showing a schematic diagram of a magnetic particle according to a third embodiment of the present invention. FIG. 4 is a cross-sectional view showing a schematic diagram of a magnetic particle according to a fourth embodiment of the present invention. FIG. 5 is a schematic diagram for explaining each region in a magnetic substance-encapsulated resin particle for determining the content of the first magnetic substance.

The details of the present invention are described below.

(Magnetic Particles)
The magnetic particles according to the present invention are used to specifically interact with a target substance. The magnetic particles according to the present invention are magnetic particles that can specifically interact with a target substance. The magnetic particles according to the present invention include magnetic body-encapsulated resin particles that contain a first magnetic body therein, a magnetic layer that is disposed on the outer surface of the magnetic body-encapsulated resin particles and contains a second magnetic body, and a substance that is supported on the outer surface side of the magnetic layer and specifically interacts with the target substance.

The magnetic particles according to the present invention have the above-mentioned configuration, and therefore can enhance magnetic collection and dispersibility, and can maintain high magnetic collection. In the present invention, high magnetic collection can be maintained for a long period of time. In the magnetic particles according to the present invention, when measuring a target substance using the magnetic particles, the amount of binding with the target substance per unit weight of the magnetic particles can be increased, and therefore the measurement sensitivity can be increased.

Conventional magnetic particles may have low magnetic collection or dispersibility. In conventional magnetic particles having a magnetic body inside the resin particles, the space inside the resin particles is limited, so it is difficult to sufficiently increase the content of the magnetic body. Therefore, it is difficult to increase the magnetic collection with conventional magnetic particles. In addition, in conventional magnetic particles having a magnetic layer on the outer surface of the resin particles, if the content of the magnetic body contained in the magnetic layer is increased, the magnetic collection can be increased to a certain extent, but this is not preferable because the particle diameter of the magnetic particles increases and the binding amount of the target substance per unit area of the magnetic particles decreases. In addition, if the magnetic layer on the outer surface of the resin particles is made thicker, the repulsive force between the magnetic particles decreases and the dispersibility may decrease. Furthermore, in both conventional magnetic particles having a magnetic body inside the resin particles and conventional magnetic particles having a magnetic layer on the outer surface of the resin particles, the content of the magnetic body decreases as the particle diameter becomes smaller, so the magnetic collection decreases, and as a result, the measurement sensitivity may decrease.

Furthermore, in conventional magnetic particles having a magnetic material inside the resin particle or a magnetic layer on the outer surface of the resin particle, the magnetic material may oxidize, causing a decrease in magnetic collection ability over time.

In contrast, the magnetic particles according to the present invention can increase the content of the magnetic material while maintaining the particle diameter of the magnetic particles small, and can increase the magnetic collection. As a result, the magnetic collection can be increased while increasing the surface area per unit weight of the magnetic particles, and the measurement sensitivity can be increased. In addition, the magnetic particles according to the present invention can increase the dispersibility. Furthermore, in the magnetic particles according to the present invention, the magnetic collection can be maintained high even if the magnetic material is deteriorated to a certain extent. For example, in the magnetic particles according to the present invention, even if a specific magnetic layer containing the second magnetic material is deteriorated to a certain extent, the magnetic collection can be maintained high because the magnetic particles contain the first magnetic material. In the magnetic particles according to the present invention, the measurement accuracy, measurement sensitivity, and measurement reproducibility can be improved in the measurement of the target substance using the magnetic particles.

The average particle diameter of the magnetic particles is preferably 0.5 μm or more, more preferably 1.0 μm or more, and preferably 10 μm or less, more preferably 7 μm or less, even more preferably 5 μm or less, particularly preferably 4 μm or less, and most preferably 3.5 μm or less. When the average particle diameter of the magnetic particles is equal to or greater than the lower limit, the magnetic collection can be further improved. When the average particle diameter of the magnetic particles is equal to or less than the upper limit, the content of the substance that specifically interacts with the target substance per unit weight can be increased, and the amount of the target substance bound can be increased.

The average particle diameter of the magnetic particles is the number average particle diameter. The particle diameter of the magnetic particles is determined, for example, by observing 50 random magnetic particles with an electron microscope or optical microscope and calculating the average particle diameter of each magnetic particle. It is preferable to prepare a sample by drying the magnetic particles and observe the obtained sample with an electron microscope or optical microscope.

The coefficient of variation (CV value) of the average particle size of the magnetic particles is preferably 10% or less, more preferably 5% or less. When the coefficient of variation of the average particle size of the magnetic particles is equal to or less than the upper limit, the measurement accuracy can be further improved in the measurement of a target substance using the magnetic particles.

The above coefficient of variation (CV value) can be measured as follows.

CV value (%) = (ρ/Dn) × 100
ρ: standard deviation of the particle diameter of the magnetic particles Dn: average particle diameter of the magnetic particles

The present invention will now be described in detail with reference to the drawings.

Figure 1 is a cross-sectional view showing a schematic of a magnetic particle relating to a first embodiment of the present invention.

The magnetic particle 1 shown in Figure 1 is used to specifically interact with a target substance. The magnetic particle 1 comprises a magnetic body-encapsulated resin particle 2, a magnetic layer 3, a shell layer 4, and a substance 5 that specifically interacts with the target substance. The substance 5 is, for example, a physiologically active substance such as avidin, streptavidin, an antigen, or an antibody.

The magnetic body-encapsulated resin particle 2 has a resin particle 21 and a first magnetic body 22. The magnetic body-encapsulated resin particle 2 contains the first magnetic body 22 inside. In the magnetic body-encapsulated resin particle 2, the resin particle 21 contains the first magnetic body 22 inside. The first magnetic body 22 is dispersed inside the magnetic body-encapsulated resin particle 2. In the magnetic body-encapsulated resin particle 2, the first magnetic body 22 is dispersed inside the resin particle 21.

The first magnetic material 22 is uniformly distributed inside the magnetic body-encapsulated resin particle 2. The first magnetic material does not have to be uniformly distributed inside the magnetic body-encapsulated resin particle. For example, the first magnetic material may be arranged such that the content of the first magnetic material increases from the center to the outer surface of the magnetic body-encapsulated resin particle.

The magnetic layer 3 is disposed on the outer surface of the magnetic body-encapsulated resin particle 2. The magnetic layer 3 is disposed on the outer surface of the resin particle 21 in the magnetic body-encapsulated resin particle 2. The magnetic layer 3 contains a second magnetic material. The shell layer 4 is disposed on the outer surface of the magnetic layer 3. Substance 5 is supported on the outer surface side of the magnetic layer 3. Substance 5 is supported on the outer surface of the shell layer 4. The shell layer 4 and substance 5 are bonded. Substance 5 is present on the surface of the magnetic particle 1.

The magnetic layer 3 is a single-layer magnetic layer. The magnetic layer 3 covers the entire outer surface of the magnetic encapsulated resin particle 2. In the magnetic particle, the magnetic layer may cover the entire outer surface of the magnetic encapsulated resin particle, or the magnetic layer may cover a portion of the surface of the magnetic encapsulated resin particle. In the magnetic particle, the magnetic layer may be a single-layer magnetic layer, or may be a multi-layer magnetic layer composed of two or more layers.

The shell layer 4 is a single-layer shell layer. The shell layer 4 covers the entire outer surface of the magnetic layer 3. In the magnetic particles, the shell layer may cover the entire outer surface of the magnetic layer, or the shell layer may cover only a portion of the surface of the magnetic layer.

Figure 2 is a cross-sectional view showing a schematic of a magnetic particle according to a second embodiment of the present invention.

The magnetic particle 1A shown in FIG. 2 is used to specifically interact with a target substance. The magnetic particle 1A comprises a magnetic body-encapsulated resin particle 2A, a magnetic layer 3A, and a substance 5A that specifically interacts with the target substance. The substance 5A is, for example, avidin, streptavidin, an antigen, an antibody, etc. The magnetic particle 1A does not comprise the above-mentioned shell layer.

The magnetic body-encapsulated resin particle 2A has a resin particle 21A and a first magnetic body 22A. The distribution state of the first magnetic body is different between the magnetic body-encapsulated resin particle 2 shown in FIG. 1 and the magnetic body-encapsulated resin particle 2A shown in FIG. 2.

In the magnetic body-encapsulated resin particle 2A, the first magnetic material 22A is not uniformly distributed inside the magnetic body-encapsulated resin particle 2A. The first magnetic material 22A is arranged so that the content of the first magnetic material 22A increases from the center to the outer surface of the magnetic body-encapsulated resin particle 2A. The first magnetic material may be uniformly distributed inside the magnetic body-encapsulated resin particle.

The magnetic layer 3A is disposed on the outer surface of the magnetic body-encapsulated resin particle 2A. The magnetic layer 3A includes a second magnetic body. A substance 5A is supported on the outer surface of the magnetic layer 3A. The substance 5A is present on the surface of the magnetic particle 1A.

The magnetic layer 3A is a single-layer magnetic layer. The magnetic layer 3A covers the entire outer surface of the magnetic encapsulated resin particle 2A. In the magnetic particle, the magnetic layer may be a single-layer magnetic layer or a multi-layer magnetic layer composed of two or more layers.

Figure 3 is a cross-sectional view showing a schematic of a magnetic particle according to a third embodiment of the present invention.

The magnetic particle 1B shown in Figure 3 is used to specifically interact with a target substance. The magnetic particle 1B comprises a magnetic body-encapsulated resin particle 2B, a magnetic layer 3B, a shell layer 4B, and a substance 5B that specifically interacts with the target substance. The substance 5B is, for example, a physiologically active substance such as avidin, streptavidin, an antigen, or an antibody.

The magnetic body-encapsulated resin particle 2B has a resin particle 211B, a first magnetic body 22B, and a resin layer 212B. The magnetic body-encapsulated resin particle 2B contains the first magnetic body 22B inside. In the magnetic body-encapsulated resin particle 2B, the first magnetic body 22B is contained in layers. The magnetic body-encapsulated resin particle 2B has a magnetic layer containing the first magnetic body 22B inside. The resin particle 211B does not contain the first magnetic body 22B. The first magnetic body 22B is disposed between the resin particle 211B and the resin layer 212B, so that the magnetic body-encapsulated resin particle 2B contains the first magnetic body 22B inside. In the magnetic body-encapsulated resin particle 2B, a magnetic layer containing the first magnetic body 22B is disposed on the outer surface of the resin particle 211B, and a resin layer 212B is disposed on the outer surface of the magnetic layer.

The magnetic layer 3B is disposed on the outer surface of the magnetic body-encapsulated resin particle 2B. The magnetic layer 3B contains a second magnetic body. The shell layer 4B is disposed on the outer surface of the magnetic layer 3B. Substance 5B is supported on the outer surface side of the magnetic layer 3B. Substance 5B is supported on the outer surface of the shell layer 4B. The shell layer 4B and substance 5B are bonded. Substance 5B is present on the surface of the magnetic particle 1B.

The magnetic layer 3B is a single-layer magnetic layer. The magnetic layer 3B covers the entire outer surface of the magnetic encapsulated resin particle 2B. In the magnetic particle, the magnetic layer may be a single-layer magnetic layer or a multi-layer magnetic layer composed of two or more layers.

The shell layer 4B is a single-layer shell layer. The shell layer 4B covers the entire outer surface of the magnetic layer 3B.

Figure 4 is a cross-sectional view showing a schematic of a magnetic particle according to a fourth embodiment of the present invention.

The magnetic particle 1C shown in Figure 4 is used to specifically interact with a target substance. The magnetic particle 1C comprises a magnetic body-encapsulated resin particle 2C, a magnetic layer 3C, a shell layer 4C, and a substance 5C that specifically interacts with the target substance. The substance 5C is, for example, a physiologically active substance such as avidin, streptavidin, an antigen, or an antibody.

The magnetic body-encapsulated resin particle 2C has a resin particle 211C, first magnetic bodies 221C, 222C, and a resin layer 212C. The magnetic body-encapsulated resin particle 2C contains the first magnetic bodies 221C, 222C inside. The first magnetic body 221C is dispersed inside the magnetic body-encapsulated resin particle 2C. The first magnetic body 221C is dispersed inside the resin particle 211C. In the magnetic body-encapsulated resin particle 2C, the first magnetic body 221C is dispersed inside the resin particle 211C. In the magnetic body-encapsulated resin particle 2C, the first magnetic body 222C is contained in a layer shape. The magnetic body-encapsulated resin particle 2C has a magnetic layer containing the first magnetic body 222C inside. The first magnetic body 222C is disposed between the resin particle 211C and the resin layer 212C, so that the magnetic substance-encapsulated resin particle 2C contains the first magnetic body 222C therein. In the magnetic substance-encapsulated resin particle 2C, a magnetic layer containing the first magnetic body 222C is disposed on the outer surface of the resin particle 211C, and the resin layer 212C is disposed on the outer surface of the magnetic layer.

The magnetic layer 3C is disposed on the outer surface of the magnetic body-encapsulated resin particle 2C. The magnetic layer 3C contains a second magnetic body. The shell layer 4C is disposed on the outer surface of the magnetic layer 3C. Substance 5C is supported on the outer surface side of the magnetic layer 3C. Substance 5C is supported on the outer surface of the shell layer 4C. The shell layer 4C and substance 5C are bonded. Substance 5C is present on the surface of the magnetic particle 1C.

The magnetic layer 3C is a single-layer magnetic layer. The magnetic layer 3C covers the entire outer surface of the magnetic body-encapsulated resin particle 2C. In the magnetic particle, the magnetic layer may be a single-layer magnetic layer or a multi-layer magnetic layer composed of two or more layers.

The shell layer 4C is a single-layer shell layer. The shell layer 4C covers the entire outer surface of the magnetic layer 3C.

Further details of the magnetic particles are described below.

(Magnetic body-encapsulated resin particles)
The magnetic body-encapsulated resin particles include a resin. The magnetic body-encapsulated resin particles include resin particles. The magnetic body-encapsulated resin particles include a first magnetic body inside. The magnetic body-encapsulated resin particles preferably include a first magnetic body inside by having the following configuration (1) or (2). (1) Resin particles and a first magnetic body are included, and the first magnetic body is dispersed inside the resin particles. (2) Resin particles, a first magnetic body, and a resin layer are included, and on the outer surface of the resin particles, a magnetic layer including the first magnetic body and a resin layer are alternately arranged from the center of the magnetic body-encapsulated resin particles toward the outer surface. The magnetic body-encapsulated resin particles may include only the configuration (1), may include only the configuration (2), or may include both the configuration (1) and the configuration (2). In addition, when the magnetic body-encapsulated resin particles include the configuration (2), it is preferable that a magnetic layer including the first magnetic body is arranged on the outer surface of the resin particles, and it is preferable that the outermost layer of the magnetic body-encapsulated resin particles is a resin layer. The magnetic body-encapsulated resin particles having the above-mentioned configuration (1) are, for example, the magnetic body-encapsulated resin particles shown in Figures 1 and 2. The magnetic body-encapsulated resin particles having the above-mentioned configuration (2) are, for example, the magnetic body-encapsulated resin particles shown in Figure 3. The magnetic body-encapsulated resin particles having the above-mentioned configuration (1) and the above-mentioned configuration (2) are, for example, the magnetic body-encapsulated resin particles shown in Figure 4.

When the magnetic body-encapsulated resin particles have the above configuration (2), the magnetic body-encapsulated resin particles may have one resin layer and one magnetic layer containing a first magnetic material, or may have two or more resin layers and two or more magnetic layers containing the first magnetic material.

<Resin Particles and Resin Layer>
Examples of the material of the resin particles and the resin layer include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; polycarbonate, polyamide, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polyethylene terephthalate, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyamideimide, polyether ether ketone, polyether sulfone, divinylbenzene polymer, and divinylbenzene copolymer. Examples of the divinylbenzene copolymer include divinylbenzene-styrene copolymer and divinylbenzene-(meth)acrylic acid ester copolymer. The material of the resin particles and the resin layer may be used alone or in combination of two or more. Furthermore, when the magnetic substance-encapsulated resin particles have the above configuration (2), the material of the resin particles and the material of the resin layer may be the same as or different from each other.

From the viewpoint of obtaining the magnetic body-encapsulated resin particles satisfactorily, it is preferable that the resin particles have a porous structure. It is preferable that the resin particles in the magnetic body-encapsulated resin particles having the above configuration (1) have a porous structure. The resin particles in the magnetic body-encapsulated resin particles having the above configuration (2) may or may not have a porous structure.

The BET specific surface area of the resin particles is preferably ²⁰ m2/g or more, more preferably ⁴⁰ m2/g or more, even more preferably ¹⁰⁰ m2/g or more, and is preferably 800 ^m2 /g or less, more preferably 700 ^m2 /g or less, even more preferably 650 ^m2 /g or less. When the BET specific surface area is equal to or greater than the lower limit and equal to or less than the upper limit, the content of the first magnetic body encapsulated in the magnetic body-encapsulated resin particles can be increased, and the magnetic collection can be further improved.

The average pore diameter of the resin particles is preferably 0.5 nm or more, more preferably 1 nm or more, and preferably 30 nm or less, more preferably 10 nm or less. When the average pore diameter is equal to or more than the lower limit and equal to or less than the upper limit, the magnetic material can be more easily contained inside the resin particles, the content of the first magnetic material encapsulated in the magnetic material-encapsulated resin particles can be increased, and the magnetic collection can be further increased.

The BET specific surface area and average pore size of the resin particles can be measured from the nitrogen adsorption isotherm according to the BJH method. Examples of measuring devices for measuring the BET specific surface area and average pore size of the resin particles include the "NOVA4200e" manufactured by Quantachrome Instruments.

Resin particles satisfying the preferred ranges of the BET specific surface area and the average pore size can be obtained, for example, by a method for producing resin particles comprising the following steps. A step of mixing a polymerizable monomer with an organic solvent that does not react with the polymerizable monomer to prepare a polymerizable monomer solution. A step of adding the polymerizable monomer solution and an anionic dispersion stabilizer to a polar solvent and emulsifying to obtain an emulsion. A step of adding the emulsion in several portions to absorb the monomer into the seed particles to obtain a suspension containing seed particles in which the monomer is swollen. A step of polymerizing the polymerizable monomer to obtain resin particles. Examples of the polymerizable monomer include monofunctional monomers and polyfunctional monomers. The organic solvent that does not react with the polymerizable monomer is not particularly limited as long as it is incompatible with polar solvents such as water, which is the medium of the polymerization system. Examples of the organic solvent include cyclohexane, toluene, xylene, ethyl acetate, butyl acetate, allyl acetate, propyl acetate, chloroform, methylcyclohexane, and methyl ethyl ketone. The amount of the organic solvent added is preferably 1 part by weight to 80 parts by weight, and more preferably 20 parts by weight to 60 parts by weight, based on 100 parts by weight of the polymerizable monomer component. When the amount of the organic solvent added is within the above preferred range, the BET specific surface area and the average pore size can be controlled within more suitable ranges, making it easier to obtain dense pores inside the particles.

The average particle diameter of the resin particles is preferably 0.5 μm or more, more preferably 1 μm or more, preferably 10 μm or less, more preferably 7 μm or less, even more preferably 5 μm or less, particularly preferably 4 μm or less, and most preferably 3.5 μm or less. When the average particle diameter of the resin particles is equal to or greater than the lower limit, the magnetic collection can be further improved. When the average particle diameter of the resin particles is equal to or less than the upper limit, the sedimentation of the magnetic particles can be effectively suppressed, the dispersibility can be further improved, and the particle diameter of the magnetic particles can be reduced, allowing the target substance to interact effectively.

The average particle diameter of the resin particles is the number average particle diameter. The average particle diameter of the resin particles is determined by observing 50 random resin particles with an electron microscope or optical microscope and calculating the average particle diameter of each resin particle. It is preferable to prepare a sample by drying the magnetic particles or the resin particles, and observe the obtained sample with an electron microscope or optical microscope.

<First Magnetic Body>
The first magnetic material is preferably a metal or a metal oxide, and more preferably a ferromagnetic material or a paramagnetic material.

Examples of the first magnetic material include iron, cobalt, nickel, ruthenium, lanthanoid, and ferrite. Examples of the ferrite include maghemite (γFe ₂ O ₃ ) and a compound represented by MFe ₂ O ₄ (in MFe ₂ O ₄ , M is Co, Ni, Mn, Zn, Mg, Cu, Fe, Li _0.5 Fe _0.5 , etc.). The ferrite is preferably triiron tetroxide (Fe ₃ O ₄ ). The first magnetic material may be an alloy. Examples of the alloy include a nickel-cobalt alloy, a cobalt-tungsten alloy, an iron-platinum alloy, and an iron-cobalt alloy. The metal may be a metal ion. Only one type of the first magnetic material may be used, or two or more types may be used in combination.

From the viewpoint of further increasing the magnetic collection and maintaining high magnetic collection for a longer period of time, the first magnetic body is preferably cobalt or ferrite, more preferably cobalt or triiron tetroxide, and even more preferably cobalt.

In 100% by volume of the magnetic particles, the content of the first magnetic material is preferably 10% by volume or more, more preferably 20% by volume or more, preferably 80% by volume or less, more preferably 70% by volume or less. When the content of the first magnetic material is equal to or greater than the lower limit, the magnetic collection can be further increased. When the content of the first magnetic material is equal to or less than the upper limit, the dispersibility can be further increased.

Of the total of the first magnetic body and the second magnetic body (100% by weight), the content of the first magnetic body is preferably 10% by weight or more, more preferably 20% by weight or more, preferably 90% by weight or less, more preferably 85% by weight or less. When the content of the first magnetic body is equal to or more than the lower limit and equal to or less than the upper limit, the magnetic collection can be further increased and the high magnetic collection can be maintained for a longer period of time.

Of the 100 volume % of the region (R1) from the outer surface of the magnetic body-encapsulated resin particle to 1/3 of the thickness toward the center, the content of the first magnetic material (hereinafter sometimes referred to as content (1)) is preferably 20 volume % or more, more preferably 30 volume % or more, and preferably 70 volume % or less, more preferably 60 volume % or less. When the content (1) is equal to or more than the lower limit and equal to or less than the upper limit, the magnetic collection can be further increased. Furthermore, when the content (1) is equal to or less than the upper limit, the resin skeleton is well maintained and the particle shape can be well maintained. The region (R1) is the region outside the dashed line L1 of the magnetic body-encapsulated resin particle 2 in Figure 5.

Of the 100 volume % of the region (R2) extending from the center of the magnetic body-encapsulated resin particle to 2/3 of the thickness toward the outer surface, the content of the first magnetic material (hereinafter sometimes referred to as content (2)) is preferably 15 volume % or more, more preferably 30 volume % or more, and preferably 70 volume % or less, more preferably 60 volume % or less. When the content (2) is equal to or more than the lower limit and equal to or less than the upper limit, the magnetic collection can be further improved. The region (R2) is the region inside the dashed line L1 of the magnetic body-encapsulated resin particle 2 in Figure 5.

The ratio of the content (1) to the content (2) (content (1)/content (2)) is preferably 0.8 or more, more preferably 1.0 or more, and is preferably 4.0 or less, more preferably 3.0 or less. When the ratio (content (1)/content (2)) is equal to or more than the lower limit and equal to or less than the upper limit, the magnetic collection and dispersibility can be further improved.

The absolute value of the difference between the above content (1) and the above content (2) is preferably 25 volume % or less, more preferably 10 volume % or less. The first magnetic material is preferably present uniformly inside the magnetic body-encapsulated resin particles, and is preferably uniformly contained inside the magnetic body-encapsulated resin particles.

The above content (1) and the above content (2) can be measured as follows.

The magnetic particles are added to Kulzer's Technovit 4000 so that the content of the magnetic particles is 30% by weight, and dispersed to prepare an embedded resin body for magnetic particle inspection. A cross section of the magnetic particles is cut out using an ion milling device (Hitachi High-Technologies Corporation's IM4000) so as to pass through the vicinity of the center of the magnetic particles dispersed in the embedded resin body for inspection. Then, using a field emission transmission electron microscope (JEOL Ltd.'s JEM-2010FEF) and an energy dispersive X-ray analyzer (EDS), the content of the first magnetic body in the thickness direction of the magnetic body-encapsulated resin particles is measured, thereby obtaining the distribution result of the content of the first magnetic body in the thickness direction of the magnetic body-encapsulated resin particles. From this result, the above content (1) and the above content (2) can be calculated. The above content (1) and the above content (2) are preferably average contents calculated by arithmetically averaging the contents (1) and (2) of 20 arbitrarily selected magnetic body-encapsulated resin particles.

The manufacturing method of the magnetic body-encapsulated resin particles is not particularly limited. For example, the resin particles having a porous structure and the first magnetic body are mixed, and the first magnetic body is introduced into the interior of the resin particles to obtain magnetic body-encapsulated resin particles having the above configuration (1). In addition, for example, the resin particles having a solid structure and the first magnetic body are mixed, the outer surface of the resin particles is coated with the first magnetic body, and then the outer surface of the first magnetic body is coated with a resin to obtain magnetic body-encapsulated resin particles having the above configuration (2).

(Magnetic Layer)
The magnetic particles according to the present invention include a magnetic layer including a second magnetic body. The magnetic layer including the second magnetic body is disposed on the outer surface of the magnetic body-encapsulated resin particle. The first magnetic body and the second magnetic body may be the same or different.

The second magnetic material is preferably a metal or a metal oxide, and more preferably a ferromagnetic or paramagnetic material.

Examples of the second magnetic material include iron, cobalt, nickel, ruthenium, lanthanoids, and ferrite. Examples of the ferrite include maghemite (γFe ₂ O ₃ ) and a compound represented by MFe ₂ O ₄ (in MFe ₂ O ₄ , M is Co, Ni, Mn, Zn, Mg, Cu, Fe, Li _0.5 Fe _0.5 , etc.). The ferrite is preferably triiron tetroxide (Fe ₃ O ₄ ). The second magnetic material may be an alloy. Examples of the alloy include a nickel-cobalt alloy, a cobalt-tungsten alloy, an iron-platinum alloy, and an iron-cobalt alloy. The metal may be a metal ion. Only one type of the second magnetic material may be used, or two or more types may be used in combination.

From the viewpoint of further increasing the magnetic collection and maintaining the high magnetic collection for a longer period of time, the second magnetic material is preferably ferrite, and more preferably triiron tetroxide.

Of the total of the first magnetic body and the second magnetic body (100% by weight), the content of the second magnetic body is preferably 10% by weight or more, more preferably 30% by weight or more, preferably 90% by weight or less, more preferably 70% by weight or less. When the content of the second magnetic body is equal to or more than the lower limit and equal to or less than the upper limit, the magnetic collection can be further increased and the high magnetic collection can be maintained for a longer period of time.

In 100% by volume of the magnetic particles, the content of the second magnetic material is preferably 4% by volume or more, more preferably 8% by volume or more, preferably 40% by volume or less, more preferably 25% by volume or less. When the content of the second magnetic material is equal to or greater than the lower limit, the magnetic collection can be further increased. When the content of the second magnetic material is equal to or less than the upper limit, the dispersibility can be further increased.

In 100% by weight of the magnetic particles, the total content of the first magnetic body and the second magnetic body is preferably 10% by weight or more, more preferably 15% by weight or more, preferably 95% by weight or less, more preferably 80% by weight or less. When the total content is equal to or greater than the lower limit, the magnetic collection can be further improved. When the total content is equal to or less than the upper limit, the dispersibility can be further improved.

In 100% by volume of the magnetic particles, the total content of the first magnetic body and the second magnetic body is preferably 20% by volume or more, more preferably 30% by volume or more, preferably 80% by volume or less, more preferably 70% by volume or less. When the total content is equal to or greater than the lower limit, the magnetic collection can be further improved. When the total content is equal to or less than the upper limit, the dispersibility can be further improved.

Of the total surface area (100%) of the outer surface of the magnetic body-encapsulated resin particles, the surface area covered by the magnetic layer containing the second magnetic body is preferably 70% or more, more preferably 80% or more, even more preferably 95% or more, and most preferably 100%. If the surface area is equal to or greater than the lower limit, the magnetic collection can be further increased, high magnetic collection can be maintained for a longer period of time, and dispersibility can be further increased.

The thickness of the magnetic layer is preferably 20 nm or more, more preferably 50 nm or more, and preferably 1000 nm or less, more preferably 200 nm or less. The thickness of the magnetic layer is the thickness of the entire magnetic layer when the magnetic layer is multi-layered. If the thickness of the magnetic layer is equal to or greater than the lower limit, the magnetic collection can be further increased and the high magnetic collection can be maintained for a longer period of time. If the thickness of the magnetic layer is equal to or less than the upper limit, the settling of the magnetic particles can be effectively suppressed, the dispersibility can be further increased, and the particle diameter of the magnetic particles can be reduced, so that the amount of the target substance bound per unit weight of the magnetic particles can be increased.

The thickness of the magnetic layer can be measured, for example, by observing the cross section of the magnetic particle using a transmission electron microscope (TEM). It is preferable to calculate the thickness of the magnetic layer by averaging the thickness of five arbitrary magnetic layers as the thickness of the magnetic layer of one magnetic particle, and it is more preferable to calculate the average thickness of the entire magnetic layer as the thickness of the magnetic layer of one magnetic particle. The thickness of the magnetic layer is preferably calculated by calculating the average thickness of the magnetic layer of each of the arbitrary ten magnetic particles.

The magnetic layer may be a continuous layer, or may be a layer formed by granular matter in which the second magnetic body is aggregated in a particle form. The magnetic layer may cover the entire outer surface of the resin particle, or may cover only a part of it. The magnetic layer may have a sea-island structure. From the viewpoint of effectively suppressing the decrease in magnetic collection, it is preferable that the magnetic layer is a continuous layer. The continuous layer refers to a layer having a structure with few or no seams, unlike a shape in which there are countless seams (for example, 1000 or more per magnetic particle) in the magnetic layer, such as an aggregate of fine particles. From the viewpoint of further increasing magnetic collection, it is preferable that the magnetic layer is a layer formed by granular matter in which the second magnetic body is aggregated in a particle form.

When the magnetic layer is a layer formed by granular matter in which the second magnetic body is aggregated in a particulate form, the average particle size of the granular matter is preferably 1 nm or more, more preferably 2 nm or more, preferably 50 nm or less, more preferably 20 nm or less. When the average particle size of the granular matter is equal to or greater than the lower limit, the magnetic collection can be further improved. When the average particle size of the granular matter is equal to or less than the upper limit, the second magnetic body can be well arranged on the outer surface of the magnetic body-encapsulated resin particles, and the magnetic layer can be well formed.

The method for forming the magnetic layer is not particularly limited. For example, the magnetic layer can be formed on the outer surface of the magnetic body-encapsulated resin particles by mixing the magnetic body-encapsulated resin particles with the second magnetic body granules.

(Shell layer)
The magnetic particles according to the present invention preferably have a shell layer. The material of the shell layer includes an inorganic oxide or an organic polymer. The shell layer is an inorganic oxide shell layer containing the inorganic oxide as the material of the shell layer, or an organic polymer shell layer containing the organic polymer as the material of the shell layer. The shell layer is preferably arranged on the outer surface of the magnetic layer containing the second magnetic material. By providing the magnetic particles with the shell layer, a substance that specifically interacts with the target substance can be well arranged on the surface of the magnetic particles, and the dispersibility of the magnetic particles can be further improved. In addition, by providing the magnetic particles with a shell layer, it is possible to firmly prevent the elution of impurities from magnetic body-encapsulated resin particles, the elution of magnetic bodies, and the elution of impurities from the magnetic layer. Therefore, when the magnetic particles have the shell layer, they can be suitably used as a test drug.

The shell layer may or may not contain a magnetic material. It is more preferable that the shell layer does not contain a magnetic material. It is more preferable that the shell layer is a non-magnetic layer that does not contain a magnetic material.

From the viewpoint of further enhancing the dispersibility of the magnetic particles, it is preferable that the material of the shell layer contains the inorganic oxide, and it is more preferable that the shell layer is an inorganic oxide shell layer containing an inorganic oxide.

<Inorganic oxide>
The inorganic oxide means a compound having at least a metal element or a metalloid element and an oxygen atom. The inorganic oxide is not particularly limited. The inorganic oxide may be used alone or in combination of two or more kinds.

The inorganic oxide is preferably an inorganic oxide having silicon atoms, germanium atoms, titanium atoms, or zirconium atoms. The inorganic oxide preferably has a functional group capable of reacting with the outer surface of the magnetic layer. The method of reacting the magnetic surface with the non-magnetic layer is not particularly limited, but examples thereof include covalent bonds and coordinate bonds.

Specific examples of the inorganic oxides include silane compounds such as alkoxysilanes, such as tetraethyl orthosilicate, and their hydrolysates; germanium compounds such as alkoxygermaniums, such as germanium tetraethoxide, and their hydrolysates; titanium compounds such as alkoxytitaniums, such as titanium tetraethoxide, and their hydrolysates; and zirconium compounds such as alkoxyzirconiums, such as zirconium tetrabutoxide, and their hydrolysates.

From the viewpoint of maintaining high dispersibility of the magnetic particles, it is preferable that the inorganic oxide is a compound with a low specific gravity, and among the above examples, the silane compound is most preferable.

Examples of the silane compounds include tetraethyl orthosilicate; vinyl group-containing silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and 7-octenyltrimethoxysilane; epoxy group-containing silane compounds such as 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and 8-glycidoxyoctyltrimethoxysilane. silane compounds containing a styryl group, such as p-styryltrimethoxysilane; silane compounds containing a methacryl group, such as 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 8-methacryloxyoctyltrimethoxysilane; silane compounds containing an acryl group, such as 3-acryloxypropyltrimethoxysilane; N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, amino group-containing silane compounds such as N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-triethoxysilyl-N-(1,3-dimethyl-butylidene)propylamine, N-phenyl-3-aminopropyltrimethoxysilane, N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride, and N-2-(aminoethyl)-8-aminooctyltrimethoxysilane; isocyanurate such as tris-(trimethoxysilylpropyl)isocyanurate; Examples of the silane compound include a silane compound containing a socyanurate group; a silane compound containing a ureido group, such as 3-ureidopropyltrialkoxysilane; a silane compound containing a mercapto group, such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane; a silane compound containing an isocyanate group, such as 3-isocyanatepropyltriethoxysilane; a silane compound containing a carboxylic acid anhydride, such as 3-trimethoxysilylpropylsuccinic anhydride; and a silane compound containing a carboxylic acid, such as a hydrolysate of 3-trimethoxysilylpropylsuccinic anhydride.

For example, by treating the surface of the magnetic layer with a silane compound having various functional groups, an inorganic oxide shell layer having silicon atoms can be formed on the outer surface of the magnetic layer.

Of the 100% by weight of the inorganic oxide shell layer, the content of the inorganic oxide is preferably 70% by weight or more, and more preferably 80% by weight or more.

<Organic Polymer>
The organic polymer is not particularly limited, but is preferably a vinyl polymer.

Examples of vinyl monomers used in the materials for the vinyl polymers include styrene monomers such as styrene, α-methylstyrene, chlorostyrene, and divinylbenzene; vinyl ether compounds such as methyl vinyl ether, ethyl vinyl ether, and propyl vinyl ether; acid vinyl ester compounds such as vinyl acetate, vinyl butyrate, vinyl laurate, and vinyl stearate; halogen-containing monomers such as vinyl chloride and vinyl fluoride; (meth)acrylic acid; alkyl (meth)acrylate compounds such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and ethylene glycol (meth)acrylate; 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and the like. Examples of the silane alkoxides include oxygen atom-containing (meth)acrylate compounds such as ethylene (meth)acrylate and glycidyl (meth)acrylate; halogen-containing (meth)acrylate compounds such as trifluoromethyl (meth)acrylate and pentafluoroethyl (meth)acrylate; and polymerizable double bond-containing silane alkoxides such as vinyltrimethoxysilane, vinyltriethoxysilane, dimethoxymethylvinylsilane, dimethoxyethylvinylsilane, diethoxymethylvinylsilane, diethoxyethylvinylsilane, ethylmethyldivinylsilane, methylvinyldimethoxysilane, ethylvinyldimethoxysilane, methylvinyldiethoxysilane, ethylvinyldiethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane.

The vinyl polymer may be a homopolymer formed by polymerization of one type of vinyl monomer, or a copolymer formed by polymerization of two or more types of vinyl monomer.

For example, in the presence of base particles, a copolymerizable monomer such as a vinyl monomer as the main raw material, and, if necessary, secondary raw materials such as a polymerization initiator, an emulsifier, a dispersant, a surfactant, an electrolyte, a crosslinking agent, and a molecular weight regulator, are added, and polymerization is carried out in a liquid, thereby forming an organic polymer shell layer on the outer surface of the magnetic layer.

In 100% by weight of the organic polymer shell layer, the content of the organic polymer is preferably 70% by weight or more, and more preferably 80% by weight or more.

It is preferable that the shell layer has functional groups such as carboxyl groups, hydroxyl groups, epoxy groups, amino groups, tosyl groups, thiol groups, triethylammonium groups, dimethylamino groups, and sulfonic acid groups before binding with the substance that specifically interacts with the target substance. When the shell layer has the functional groups, the substance that specifically interacts with the target substance can be well supported on the outer surface of the shell layer, and the substance can be well arranged on the surface of the magnetic particle.

The shell layer may have a linker portion on the outer surface. By having the linker portion in the shell layer, the functional group, which is the binding point with the substance that specifically interacts with the target substance, can be positioned at a position farther away from the outermost surface of the shell layer, and the functional group and the substance can come into contact with each other at a position with fewer steric hindrances. This makes it easier for the substance to bind, and the substance can be well positioned on the surface of the magnetic particle.

It is preferable that the linker part has a functional group capable of covalently bonding with the target substance, such as a carboxyl group, a hydroxyl group, an epoxy group, an amino group, a tosyl group, or a thiol group, at its end before binding to the substance that specifically interacts with the target substance. The shell layer can be chemically bonded to the substance by reacting the functional group with the functional group of the substance that specifically interacts with the target substance. The epoxy group may be an epoxy group derived from a glycidyl group-containing monomer. The hydroxyl group may be a hydroxyl group generated by ring-opening of the epoxy group.

The material of the linker part is preferably an epoxy compound having multiple epoxy groups at its terminal. The epoxy compound having multiple epoxy groups at its terminal is preferably polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, or trimethylolpropane polyglycidyl ether. The epoxy compound having multiple epoxy groups at its terminal is more preferably polyethylene glycol diglycidyl ether.

It is preferable that the shell layer and the substance that specifically interacts with the target substance are bonded, and more preferably chemically bonded.

Of the total surface area (100%) of the outer surface of the magnetic layer including the second magnetic body, the surface area covered by the shell layer is preferably 95% or more, more preferably 99% or more, and most preferably 100%. When the surface area is equal to or greater than the lower limit, the content of the substance that specifically interacts with the target substance can be increased, and as a result, the measurement accuracy and measurement sensitivity can be improved in the measurement of the target substance using magnetic particles.

The thickness of the shell layer is preferably 20 nm or more, more preferably 40 nm or more, and preferably 500 nm or less, more preferably 300 nm or less. When the thickness of the shell layer is equal to or greater than the lower limit and equal to or less than the upper limit, the sedimentation of the magnetic particles can be effectively suppressed, the dispersibility can be further improved, and the particle diameter of the magnetic particles can be reduced, so that the target substance can be effectively bound.

The thickness of the shell layer can be measured by observing the cross section of the magnetic particle using, for example, a transmission electron microscope (TEM). It is preferable to calculate the thickness of the shell layer by averaging the thickness of five arbitrary shell layers as the thickness of the shell layer of one magnetic particle, and it is more preferable to calculate the average thickness of the entire shell layer as the thickness of the shell layer of one magnetic particle. It is preferable to determine the thickness of the shell layer by calculating the average thickness of the shell layer of each of the arbitrary ten magnetic particles.

(Substance that specifically interacts with the target substance)
A substance that specifically interacts with a target substance is present on the surface of the magnetic particle according to the present invention. Examples of the substance include sugar chains, peptide chains, proteins, antigens, and nucleotide chains. The substance can be appropriately changed depending on the type of the target substance. Only one type of the substance may be used, or two or more types may be used in combination.

Examples of interactions between the substance and the target substance include antigen-antibody reactions and interactions between enzymes and substrates. The interaction between the substance and the target substance may be a non-covalent interaction between the substance and the target substance, or a covalent bond between the substance and the target substance. Examples of non-covalent interactions include hydrophobic interactions, electrostatic interactions, van der Waals forces, hydrogen bonds, coordinate bonds, and ionic bonds.

It is preferable that the substance that specifically interacts with the target substance is a substance that is capable of non-covalent interaction with the target substance.

Examples of combinations of the above-mentioned substance that specifically interacts with the above-mentioned target substance and the target substance include a combination of an antibody and an antigen, a combination of a glycan and a protein such as a lectin, a combination of a protein such as an enzyme and an inhibitor, a combination of a peptide and a protein, a combination of a nucleotide chain and a nucleotide chain, a combination of a nucleotide chain and a protein, etc.

The substance that specifically interacts with the target substance is preferably a protein, and more preferably avidin or streptavidin. Also, the substance that specifically interacts with the target substance is preferably an antigen or an antibody.

The antibody may be a polyclonal antibody or a monoclonal antibody. The antibody may be treated with protease such as papain and pepsin, and may be in the form of Fab and F(ab')2 fragments.

The method of disposing the substance that specifically interacts with the target substance is not particularly limited. For example, the substance can be disposed on the surface of the magnetic particles by mixing the substance with the magnetic particles before the substance is supported.

(Target substance)
The target substance is a substance that specifically interacts with the above-mentioned substance.

The target substances include proteins, nucleic acids, hormones, cancer markers, respiratory markers, heart disease markers, and drugs.

The above proteins include lipid proteins such as high density lipoprotein (HDL), low density lipoprotein (LDL), and very low density lipoprotein; enzymes such as alkaline phosphatase, amylase, acid phosphatase, gamma-glutamyltransferase (gamma-GTP), lipase, creatine kinase (CK), lactate dehydrogenase (LDH), glutamic oxaloacetate transaminase (GOT), glutamic pyruvic transaminase (GPT), renin, protein kinase (PK), and tyrosine kinase. immunoglobulins such as IgG, IgM, IgA, IgD, IgE, etc. (or fragments thereof such as the Fc portion, the Fab portion, and the F(ab)2 portion); blood coagulation-related factors such as fibrinogen, fibrin degradation products (FDPs), prothrombin, thrombin, etc.; antibodies such as anti-streptolysin O antibody, anti-human hepatitis B virus surface antigen antibody (HBs antigen), anti-human hepatitis C virus antibody, and anti-rheumatoid factor; albumin, hemoglobin, myoglobin, transferrin, protein A, C-reactive protein (CRP), etc.

Examples of the above nucleic acids include DNA and RNA.

The above hormones include thyroid-stimulating hormone (TSH), thyroid hormones (FT3, FT4, T3, T4), parathyroid hormone (PTH), human chorionic gonadotropin (hCG), estradiol (E2), etc.

Examples of the above cancer markers include alpha-fetoprotein (AFP), PIVKA-II, carcinoembryonic antigen (CEA), CA19-9, and prostate-specific antigen (PSA).

Examples of the respiratory system-related markers include KL-6.

Examples of the above-mentioned cardiac disease markers include troponin T (TnT) and N-terminal fragment of human brain natriuretic peptide precursor (NT-proBNP).

The above drugs include antiepileptic drugs, antibiotics, and theophylline, etc.

(Other details of magnetic particles)
The magnetic particles are preferably used in measurements such as radioimmunoassay (RIA), enzyme immunoassay (EIA), fluorescence immunoassay (FIA), electrochemiluminescence assay (ECLIA), chemiluminescence immunoassay (CLIA and CLEIA), absorbance measurement, and surface plasmon resonance. The magnetic particles are preferably used in measurements such as sandwich method and competitive method.

The magnetic particles are suitable for use in measuring the concentration of the target substance in a sample.

The magnetic particles are preferably used as a test agent. The magnetic particles are preferably magnetic particles that can be used as a test agent.

Measurement of the concentration of a target substance using the above-mentioned magnetic particles can be performed, for example, as follows.

A liquid containing the magnetic particles (e.g., a test drug described below) is mixed with a specimen containing a target substance to obtain a mixed liquid. The resulting mixed liquid is heated or otherwise treated to obtain a reaction liquid in which the target substance in the specimen is bound to the substance in the magnetic particles that specifically interacts with the target substance (first reaction step). Next, a magnetic force is applied to the reaction liquid using a magnet or the like to collect the magnetic particles (magnetic collection step). After removing unreacted specimen, a washing liquid is added and mixed (washing step). The magnetic collection step and washing step may be repeated multiple times. Next, after removing the washing liquid, the target substance is reacted with a labeling substance to measure the concentration of the target substance (second reaction step).

Examples of the labeling substances include enzymes such as alkaline phosphatase, β-galactosidase, peroxidase, microperoxidase, glucose oxidase, glucose-6-phosphate dehydrogenase, malate dehydrogenase, luciferase, tyrosinase, and acid phosphatase, which are preferably used in enzyme immunoassay (EIA); radioisotopes such as 99mTc, 131I, 125I, 14C, 3H, and 32P, which are preferably used in radioimmunoassay (RIA); and fluorescein, dansyl, fluorescamine, coumarin, naphthylamine and their derivatives, green fluorescent protein, which are preferably used in fluorescence immunoassay (FIA). Examples of the labeling agent include fluorescent substances such as GFP (green fluorescent protein), luminescent substances such as luciferin, isoluminol, luminol, and bis(2,4,6-trifluorophenyl)oxalate, substances having absorption in the ultraviolet region such as phenol, naphthol, anthracene, and derivatives thereof, and compounds having properties as spin labeling agents such as compounds having an oxyl group such as 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl, 3-amino-2,2,5,5-tetramethylpyrrolidine-1-oxyl, and 2,6-di-t-butyl-α-(3,5-di-t-butyl-4-oxo-2,5-cyclohexadiene-1-ylidene)-p-trioxyl. From the viewpoint of increasing the measurement sensitivity, the labeling substance is preferably an enzyme or a fluorescent substance, more preferably alkaline phosphatase, peroxidase, or glucose oxidase, and even more preferably peroxidase.

(Testing agent)
The test agent includes the magnetic particles described above.

It is preferable that the test agent contains a buffer solution.

The buffer solution is preferably a buffer solution having a buffering capacity at a pH of 5.0 or more and 9.0 or less. Examples of the buffer solution include phosphate buffer, glycine buffer, veronal buffer, Tris buffer, borate buffer, citrate buffer, Good's buffer, etc.

The above test agent may contain other components such as sensitizers, polymeric compounds such as proteins, amino acids, and surfactants.

By including the sensitizer in the test agent, the reaction between the target substance and a compound capable of binding to the target substance can proceed efficiently, and the measurement accuracy can be improved. Examples of the sensitizer include alkylated polysaccharide compounds such as methylcellulose and ethylcellulose, pullulan, and polyvinylpyrrolidone.

Examples of the above proteins include albumin (bovine serum albumin, egg albumin, etc.), casein, and gelatin.

In the test drug (100% by weight), the content of the magnetic particles is preferably 0.5% by weight or more, more preferably 2% by weight or more, preferably 10% by weight or less, more preferably 5% by weight or less. When the content of the magnetic particles is equal to or more than the lower limit and equal to or less than the upper limit, the measurement accuracy of the target substance can be further improved.

The present invention will be specifically described below with reference to examples and comparative examples. The present invention is not limited to the following examples.

Example 1
Preparation of magnetic body-encapsulated resin particles:
Polystyrene particles having an average particle size of 0.69 μm were prepared as seed particles. 3.9 parts by weight of the polystyrene particles, 500 parts by weight of ion-exchanged water, and 120 parts by weight of a 5.0 wt% polyvinyl alcohol aqueous solution were mixed to prepare a mixed liquid. The mixed liquid was dispersed by ultrasonic waves, then placed in a separable flask and stirred uniformly.

Next, 150 parts by weight of divinylbenzene (monomer component) and 2.0 parts by weight of benzoyl peroxide (NOF Corp.'s "Niper BW") were mixed. Furthermore, 9.0 parts by weight of triethanolamine lauryl sulfate, 150 parts by weight of toluene (solvent), and 1,100 parts by weight of ion-exchanged water were added to prepare an emulsion.

The above emulsion was added in several portions to the above mixture in the separable flask and stirred for 12 hours to allow the seed particles to absorb the monomer, thereby obtaining a suspension containing seed particles swollen with the monomer.

Then, 490 parts by weight of a 5.0 wt% polyvinyl alcohol aqueous solution was added, heating was started, and the mixture was allowed to react at 85°C for 9 hours to obtain resin particles.

1 part by weight of the obtained resin particles and 50 parts by weight of 60% sulfuric acid were weighed into a 300 mL beaker containing a stirring bar, and then the mixture was stirred and reacted at 90°C for 24 hours to obtain resin particles with sulfone groups introduced therein.

After that, 1.0 part by weight of resin particles with sulfone groups introduced, 5.0 parts by weight of cobalt sulfate heptahydrate, and 25 mL of distilled water were weighed into a 200 mL beaker containing a stirring bar, and then stirred at room temperature for 24 hours. The above particles, 20 mL of distilled water, and 5.0 parts by weight of dimethylamine borane were then weighed, and reacted at 60°C for 1 hour under ultrasonic irradiation to obtain magnetic body-encapsulated resin particles containing cobalt as the first magnetic body.

Formation of magnetic layer (magnetic layer including second magnetic material):
One part by weight of magnetic body-encapsulated resin particles and 4 parts by weight of magnetic fluid EMG707 (aqueous dispersion of triiron tetroxide nanoparticles with an average particle size of about 10 nm, manufactured by Ferrotec Corporation) (wherein the magnetic body content is about 17% by weight) were stirred at 250 rpm for 10 minutes. The obtained particle dispersion was filtered and washed with water, and a magnetic layer containing triiron tetroxide as a second magnetic body was formed on the outer surface of the magnetic body-encapsulated resin particles, thereby obtaining magnetic body-encapsulated resin particles having a magnetic layer.

Arrangement of substances that specifically interact with the target substance:
0.5 mL of an aqueous dispersion of magnetic encapsulated resin particles having a magnetic layer was added to a test tube, and the tube was washed three times with a PBS solution. After removing the dispersion medium, 0.5 mL of a PBS solution (0.75 mg/mL) containing a sialylated glycan antigen KL-6 (hereinafter abbreviated as KL-6) antibody was added, and the mixture was stirred overnight at 25°C. Then, 1.5 mL of a 1.0 wt% BSA solution was added, and the mixture was stirred for 4 hours at 25°C. Subsequently, dispersion was performed using 1.5 mL of the 1.0 wt% BSA solution, and magnetic collection onto the test tube wall using a magnet was repeated three times to prepare a magnetic particle dispersion sensitized with anti-KL-6 antibody.

The average particle size, BET specific surface area, and average pore size of the obtained resin particles, as well as the contents of the first magnetic material and the second magnetic material in the obtained magnetic particles, the ratio of content (1) to content (2), the absolute value of the difference between content (1) and content (2), and the average particle size are shown in Table 1. These were determined by the method described in the evaluation section below.

Example 2
Magnetic particles were prepared in the same manner as in Example 1, except that the resin particles were prepared using 80 parts by weight of toluene instead of 150 parts by weight of toluene, and the composition of the magnetic particles was changed as shown in Table 1.

Example 3
Magnetic particles were prepared in the same manner as in Example 1, except that the resin particles were prepared using 30 parts by weight of toluene instead of 150 parts by weight of toluene, and the composition of the magnetic particles was changed as shown in Table 1.

Example 4
In the same manner as in Example 1, magnetic body-encapsulated resin particles having a magnetic layer were obtained.

Shell layer formation:
To 1.0 part by weight of the obtained magnetic encapsulated resin particles having a magnetic layer, 400 parts by weight of ethanol and 20 parts by weight of 28% aqueous ammonia solution (manufactured by Nacalai Tesque, Inc.) were added. Next, 5.0 parts by weight of tetraethyl orthosilicate and 15 parts by weight of 8-glycidoxyoctyltrimethoxysilane were added and stirred for 1 hour. The obtained dispersion was filtered and then washed with water. In this way, magnetic encapsulated particles having an inorganic oxide shell layer having functional groups on the surface were obtained.

Arrangement of substances that specifically interact with the target substance:
In the same manner as in Example 1, magnetic particles having anti-KL-6 antibodies on the surface thereof were obtained.

(Examples 5 and 6)
Magnetic particles were obtained in the same manner as in Example 4, except that the configurations of the resin particles and magnetic particles were changed as shown in Table 1.

(Comparative Example 1)
Resin particles were obtained in the same manner as in Example 1, except that toluene was not used, 300 parts by weight of divinylbenzene was used instead of 150 parts by weight of divinylbenzene, and 4.0 parts by weight of benzoyl peroxide was used instead of 2.0 parts by weight of benzoyl peroxide. Furthermore, in Comparative Example 1, the first magnetic material was not used. Using the obtained resin particles, a magnetic layer was formed on the outer surface of the resin particles using the second magnetic material in the same manner as in Example 1.

Shell layer formation:
Using the resin particles having the obtained magnetic layer, a shell layer was formed on the outer surface of the magnetic layer in the same manner as in Example 4.

Arrangement of substances that specifically interact with the target substance:
The obtained resin particles having a shell layer and a magnetic layer were used to arrange an anti-KL-6 antibody in the same manner as in Example 1. In this manner, magnetic particles not having a first magnetic body were obtained.

(Comparative Example 2)
Resin particles were obtained in the same manner as in Comparative Example 1. Next, acetone was added to an oil-based magnetic fluid (an organic solvent dispersion of iron trioxide nanoparticles having an average particle size of about 10 nm, "EXP Series" manufactured by Ferrotec Corporation) to precipitate and precipitate the particles, which were then dried to obtain ferrite-based magnetic fine particles (average primary particle size: 10 nm) having a hydrophobic surface.

Next, 1.0 part by weight of the resin particles and 1.0 part by weight of the ferrite-based magnetic fine particles having the hydrophobic surface were thoroughly mixed in a mixer. The resulting mixture was treated for 5 minutes using a Hybridization System NHS-0 (manufactured by Nara Machinery Co., Ltd.) at a blade (stirring blade) peripheral speed of 100 m/s (16,200 rpm), forming a magnetic layer of the second magnetic material on the outer surface of the resin particles.

Shell layer formation:
10 parts by weight of the particles having the magnetic layer obtained and 300 parts by weight of a 0.5% aqueous solution of a nonionic emulsifier ("EMULGEN 150" manufactured by Kao Corporation) as a dispersant were placed in a 1 L separable flask and stirred. 24 parts by weight of cyclohexyl methacrylate and 60 parts by weight of 2-methacryloyloxyethyl succinic acid as monomers and 1.0 part by weight of di(3,5,5-trimethylhexanoyl) peroxide ("PEROIL 355" manufactured by NOF Corporation) as an initiator were added thereto, and the mixture was stirred at 80°C and 200 rpm for 8 hours. In this way, an organic polymer shell layer having a carboxyl group was formed on the outer surface of the magnetic layer. The organic polymer is a copolymer of cyclohexyl methacrylate and 2-methacryloyloxyethyl succinic acid.

Arrangement of substances that specifically interact with the target substance:
The obtained resin particles having a shell layer and a magnetic layer were used to arrange an anti-KL-6 antibody in the same manner as in Example 1. In this manner, magnetic particles not having a first magnetic body were obtained.

(Comparative Example 3)
Magnetic particles were obtained in the same manner as in Comparative Example 1, except that the configurations of the resin particles and magnetic particles were changed as shown in Table 1. The magnetic particles obtained in Comparative Example 3 did not have the first magnetic material.

(Comparative Example 4)
Magnetic particles were prepared in the same manner as in Example 1, except that the configurations of the resin particles and magnetic particles were changed as shown in Table 1. The magnetic particles obtained in Comparative Example 4 did not have a magnetic layer.

(Comparative Example 5)
Magnetic particles were obtained in the same manner as in Comparative Example 4, except that the configurations of the resin particles and magnetic particles were changed as shown in Table 1. In Comparative Example 5, a shell layer (organic polymer shell layer) containing polyglycidyl methacrylate (PGMA) was formed as the shell layer. The magnetic particles obtained in Comparative Example 5 do not have a magnetic layer.

(evaluation)
(1) Average particle size of resin particles and magnetic particles The average particle size of the resin particles and magnetic particles obtained was calculated using a scanning electron microscope ("Regulus 8220" manufactured by Hitachi High-Technologies Corporation). Specifically, the obtained magnetic particles were dried to prepare a sample, and the obtained sample was observed under a scanning electron microscope to measure the particle sizes of 50 random magnetic particles and the resin particles in the magnetic particles, and the average value was calculated.

(2) BET Specific Surface Area of Resin Particles The nitrogen adsorption isotherm of the obtained resin particles was measured using a "NOVA4200e" manufactured by Quantachrome Instruments, Inc. From the measurement results, the specific surface area of the resin particles was calculated according to the BET method.

(3) Average pore diameter of resin particles The nitrogen adsorption isotherm of the obtained resin particles was measured using a Quantachrome Instruments "NOVA4200e." From the measurement results, the average pore diameter of the resin particles was calculated according to the BJH method.

(4) Content of the first magnetic body and the second magnetic body The magnetic particles were added to "Technovit 4000" manufactured by Kulzer so that the content of the magnetic particles was 30% by weight, and dispersed to prepare an embedded resin body for magnetic particle inspection. A cross section of the magnetic particle was cut out using an ion milling device ("IM4000" manufactured by Hitachi High-Technologies Corporation) so as to pass through the vicinity of the center of the magnetic particles dispersed in the embedded resin body for inspection. Then, the content of the first magnetic body and the second magnetic body was measured by an energy dispersive X-ray analyzer (EDS) using a field emission transmission electron microscope ("JEM-2010FEF" manufactured by JEOL Ltd.), and the distribution result of the content of the first magnetic body and the second magnetic body inside the magnetic particle was obtained. From the obtained results, the content of the first magnetic body and the second magnetic body was calculated. The content of the first magnetic body and the second magnetic body was calculated by arithmetically averaging the content of the first magnetic body and the second magnetic body of 20 arbitrarily selected magnetic particles.

In addition, the content of the first magnetic material in 100 volume % of the region (R1) extending from the outer surface of the magnetic particle to 1/3 of the thickness inward was determined as content (1). The content of the first magnetic material in 100 volume % of the region (R2) extending from the center of the magnetic particle to 2/3 of the thickness inward was determined as content (2).

The magnetic particles were added to Kulzer's Technovit 4000 so that the content of the magnetic particles was 30% by weight, and dispersed to prepare an embedded resin body for magnetic particle inspection. A cross section of the magnetic particles was cut out using an ion milling device (Hitachi High-Technologies Corporation's IM4000) so as to pass through the vicinity of the center of the magnetic particles dispersed in the embedded resin body for inspection. Then, using a field emission transmission electron microscope (JEOL Ltd.'s JEM-2010FEF) and an energy dispersive X-ray analyzer (EDS), the content of the first magnetic body in the thickness direction of the magnetic body-encapsulated resin particles was measured, and the distribution of the content of the first magnetic body in the thickness direction of the magnetic body-encapsulated resin particles was obtained. From the obtained results, the above content (1) and the above content (2) were calculated. The above content (1) and the above content (2) were calculated by arithmetically averaging the content (1) and the content (2) of 20 arbitrarily selected magnetic particles.

In addition, from the results obtained, the ratio of the content (1) to the content (2) (content (1)/content (2)) and the absolute value of the difference between the content (1) and the content (2) were calculated.

(5) Magnetic collectivity A liquid in which magnetic particles with an absorbance adjusted to 0.9 to 1.1 at a wavelength of 550 nm were dispersed in water was prepared as a sample solution. 1.3 mL of the sample solution was poured into a quartz cell placed on a spectrophotometer ("U-3900H" manufactured by Hitachi, Ltd.) in a state where a magnet (2800 G, W10 mm x D10 mm x H1 mm) was applied via a spacer (W10 mm x D10 mm x H4 mm), and the absorbance at a wavelength of 550 nm was measured 5 to 125 seconds after the sample solution was poured. The absorbance decay rate over this 120 seconds was calculated using the following formula, which was taken as the magnetic collectivity.

Magnetic collection rate (%) = [{(absorbance after 5 seconds) - (absorbance after 125 seconds)} / (absorbance after 5 seconds)] x 100

[Criteria for magnetic collection rate]
○○: Magnetic collection rate is 80% or more. ○: Magnetic collection rate is 60% or more and less than 80%. △: Magnetic collection rate is 40% or more and less than 60%. ×: Magnetic collection rate is less than 40%.

(6) Dispersion rate A liquid in which magnetic particles with an absorbance adjusted to 0.9 to 1.1 at a wavelength of 550 nm were dispersed in water was prepared as a sample solution. 1.3 mL of the sample solution was placed in a quartz cell installed in a spectrophotometer (Hitachi's "U-3900H"), and the absorbance at a wavelength of 550 nm was measured. Next, magnetic collection was performed using a magnet (28000 G, W40 mm x D40 mm x H10 mm) until the absorbance of the supernatant became 0. Thereafter, the magnetic particles were dispersed by a vortex at 2000 rpm for 5 seconds, and the absorbance at a wavelength of 550 nm was measured. The rate of change in absorbance was calculated from the absorbance before magnetic collection and the absorbance after magnetic collection and dispersion using the following formula, and was taken as the dispersion rate.

Dispersion rate (%) = {(absorbance after magnetization and dispersion) / (absorbance before magnetization)} x 100

[Dispersion ratio criteria]
○○: Dispersion rate is 95% or more. ○: Dispersion rate is 90% or more but less than 95%. △: Dispersion rate is 85% or more but less than 90%. ×: Dispersion rate is less than 85%.

(7) Magnetic collection rate (after leaving it for one month)
The obtained magnetic particles were allowed to stand for one month at 25° C. After standing, the magnetic collectivity was determined in the same manner as in (5) Magnetic collectivity.

[Criteria for magnetic collection rate (after leaving for one month)]
○○: Magnetic collection rate is 80% or more. ○: Magnetic collection rate is 60% or more and less than 80%. △: Magnetic collection rate is 40% or more and less than 60%. ×: Magnetic collection rate is less than 40%.

(8) Immunoassay (luminescence amount per unit weight of magnetic particles)
A solution not containing KL-6 (antigen-free solution) and a solution containing 5000 U/mL KL-6 (antigen-containing solution) were prepared. The binding ability between the magnetic particles and the target substance (KL-6) was evaluated by determining the difference in the amount of luminescence in an immunoassay using the antigen-free solution and the antigen-containing solution. Specifically, the evaluation was performed according to the following procedure.

Preparation of ruthenium complex-labeled anti-KL-6 antibody (secondary antibody):
To a polypropylene tube, 0.5 mL of a PBS-1 solution of anti-KL-6 antibody (anti-KL-6 antibody concentration 2.0 mg/mL) was added, followed by the addition of 13 μL of Ru-NHS (10 mg/mL). After shaking and stirring at 25° C., the mixture was purified using a Sephadex G25 column to obtain a ruthenium complex-labeled anti-KL-6 antibody.

Immunoassay:
The amount of luminescence was measured using an ECLIA automatic analyzer ("Picolumi III" manufactured by Sekisui Medical Co., Ltd.) using electrochemiluminescence immunoassay as the measurement principle, as follows. 20 μL of a solution containing 5000 U/mL KL-6 (antigen-containing solution) was added to 200 μL of reaction solution (buffer containing normal rabbit serum), and then 25 μL of magnetic particles were added. After reacting for 9 minutes at 30 ° C, 350 μL of Picolumi BF washing solution (10 mM Tris buffer) was added, and the magnetic particles were washed three times while trapped with a magnet. Next, 200 μL of a ruthenium-labeled antibody-containing solution containing 1.0 μg/mL ruthenium complex-labeled anti-KL-6 antibody was added, and reacted for 9 minutes at 30 ° C, after which 350 μL of Picolumi BF washing solution (10 mM Tris buffer) was added, and the magnetic particles were washed three times while trapped with a magnet. Next, 300 μL of picolumi luminescent electrolyte solution containing 0.1 M tripropylamine was added and delivered to the electrode surface, and the amount of luminescence of the ruthenium complex bound to the magnetic particles was measured. The difference X between the amount of luminescence in the immunoassay using the antigen-free solution and the amount of luminescence in the immunoassay using the antigen-containing solution was calculated.

[Criteria for determining the amount of light emitted per unit weight of magnetic particles]
○○: Difference X is 150,000 or more. ○: Difference X is 125,000 or more and less than 150,000. △: Difference X is 100,000 or more and less than 125,000. ×: Difference X is less than 100,000.

The magnetic particle composition and results are shown in Tables 1 and 2 below.

Reference Signs List 1, 1A, 1B, 1C... magnetic particles 2, 2A, 2B, 2C... magnetic body-encapsulated resin particles 3, 3A, 3B, 3C... magnetic layer 4, 4B, 4C... shell layer 5, 5A, 5B, 5C... substance 21, 21A, 211B, 211C... resin particles 22, 22A, 22B, 221C, 222C... first magnetic body 212B, 212C... resin layer

Claims (10)

A magnetic particle used for specifically interacting with a target substance,
a magnetic body-encapsulated resin particle including a first magnetic body therein;
a magnetic layer disposed on an outer surface of the magnetic body-encapsulated resin particle and including a second magnetic body;
a substance supported on the outer surface side of the magnetic layer and capable of specifically interacting with the target substance ;
Magnetic particles, in which the ratio of the content of the first magnetic material in 100 volume % of the region from the outer surface to the center of the magnetic-encapsulated resin particle up to 1/3 of the thickness to the content of the first magnetic material in 100 volume % of the region from the center of the magnetic-encapsulated resin particle up to 2/3 of the thickness toward the outer surface is 0.8 or more and 4.0 or less . the first magnetic material is a metal or a metal oxide,
The magnetic particle according to claim 1 , wherein the second magnetic material is a metal or a metal oxide. a shell layer disposed on an outer surface of the magnetic layer;
the material of the shell layer comprises an inorganic oxide or an organic polymer;
The magnetic particle according to claim 1 or 2, wherein the shell layer and the substance are bonded to each other. the material of the shell layer includes the inorganic oxide,
The magnetic particle according to claim 3 , wherein the inorganic oxide is an inorganic oxide having silicon atoms, germanium atoms, titanium atoms or zirconium atoms. The magnetic particle according to any one of claims 1 to 4, wherein the substance is an antigen or an antibody. The magnetic particle according to any one of claims 1 to 4, wherein the substance is avidin or streptavidin. The magnetic particles according to any one of claims 1 to 6, wherein the total content of the first magnetic body and the second magnetic body is 10% by weight or more and 95% by weight or less in 100% by weight of the magnetic particles. The magnetic particles according to any one of claims 1 to 7, wherein the content of the first magnetic body is 10% by weight or more and 90% by weight or less out of a total of 100% by weight of the first magnetic body and the second magnetic body. The magnetic particle according to any one of claims 1 to 8 , which is used as a test drug. A test agent comprising the magnetic particles according to any one of claims 1 to 8 .