JP2007095903A - Magnetic grain - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide magnetic grains capable of bonding more proteins and being less likely to have the bonded proteins detached. <P>SOLUTION: The magnetic grains contain magnetic-substance fine grains and polymer sections, and the magnetic grains satisfy Formula (1): a volume mean grain size d=0.5×10<SP>-6</SP>to 5.0×10<SP>-6</SP>[m], Formula (2): a carboxylic-acid converted surface charge-quantity E=50 to 400 [μmol/g], and Formula (3): a specific surface area S=2 to 50 [m<SP>2</SP>/g]. The magnetic grains further satisfy Formula (4): (the specific surface area S)/(spherical corresponding specific surface-area Sg≥3) (where Sg=6/(d*ρ), and ρ[g/m<SP>3</SP>] is the density of the magnetic grains). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a magnetic particle that can bind many proteins and that does not easily desorb bound proteins.

  In recent years, magnetic particles can be easily washed by magnetic separation and can provide an excellent reaction field in the immune reaction between antigen and antibody and in the hybridization between DNAs or between DNA and RNA. Application to biochemical use is becoming active. In such applications, proteins such as IgG antibodies and avidin are often used by chemically binding to the surface of magnetic particles, allowing more proteins to be bound and less protein detachment after binding. Is required.

In particular, it is possible to increase the amount of binding of biochemical substances such as proteins by increasing the surface area by making the surfaces of magnetic particles porous. For example, US Pat. No. 4,774,265 discloses magnetic particles having a porous surface. However, the particles disclosed in the patent have a very large specific surface area of, for example, 128 to 472 [m ² / g] and can bind many proteins. Is not suitable.

Japanese Patent Laid-Open No. 2003-301114 discloses particles made of an inorganic substance having a specific surface area of 5 [m ² / g] or more, and Japanese Patent Laid-Open No. 2003-151817 has a specific surface area of 10 to 60. The particle | grains which consist of an inorganic substance of [m < ² > / g] are disclosed. However, these particles are inorganic particles obtained by firing, and cannot bind proteins stably, so that they are not suitable for biochemistry.
U.S. Pat. No. 4,774,265 JP 2003-301114 A JP 2003-151817 A

  An object of this invention is to provide the magnetic particle which can couple | bond many proteins and it is hard to detach | leave from the couple | bonded protein.

  The present inventors set the volume average particle size, surface charge amount, and specific surface area (and surface charge density as necessary) as specific conditions, thereby increasing the amount of protein binding and desorption of bound protein. The present inventors have found that it is possible to achieve both the small amount and the present invention.

  That is, the magnetic particles of the present invention include magnetic fine particles and a polymer portion, and satisfy the following formulas (1) to (4).

Volume average particle diameter d = 0.5 × 10 ^{−6 to} 5.0 × 10 ⁻⁶ [m] (1)
Carboxylic acid equivalent surface charge E = 50 to 400 [μmol / g] (2)
Specific surface area S = 2 to 50 [m ² / g] (3)
Specific surface area S / spherical equivalent specific surface area Sg ≧ 3 (where Sg = 6 / (d · ρ), ρ [g / m ³ ] is the density of magnetic particles) (4)
Here, in the magnetic particle of the present invention, the surface charge density E / S can be 30 [μmol / m ² ] or less.

  Here, in the magnetic particles of the present invention, proteins can be bound to the surface.

  In the present invention, “protein” refers to a product (polypeptide) obtained by dehydration polycondensation between an amino group and a carboxyl group of adjacent amino acids, and the molecular weight thereof is not particularly limited. That is, in the present invention, “protein” includes a lower molecular weight polypeptide generally called “peptide”.

  In the present invention, the “protein” includes not only a simple protein consisting only of a polypeptide chain but also a complex protein (for example, nucleoprotein, glycoprotein, lipoprotein, phosphoprotein, etc.) containing a site other than the polypeptide chain. included.

  The magnetic particles of the present invention have a specific amount of volume average particle diameter, surface charge density, and specific surface area (and surface charge density if necessary), so that a large amount of protein is bound and the bound protein is removed. A small amount of separation can be achieved.

  The magnetic particles of the present invention can be used in a wide range of fields such as biochemical carriers such as diagnostic agents, paints, paper, electronic materials, electrophotography, cosmetics, pharmaceuticals, agricultural chemicals, foods, and catalysts. As an application example, the present invention can be applied to medical diagnostic agents, particularly to particles for automatic measuring instruments.

  Hereinafter, the magnetic particles of the present invention will be described in detail.

1. Magnetic Particle The magnetic particle of the present invention includes magnetic fine particles and a polymer portion, and satisfies the following formulas (1) to (4).

Volume average particle diameter d = 0.5 × 10 ^{−6 to} 5.0 × 10 ⁻⁶ [m] (1)
Carboxylic acid equivalent surface charge E = 50 to 400 [μmol / g] (2)
Specific surface area S = 2 to 50 [m ² / g] (3)
Specific surface area S / spherical equivalent specific surface area Sg ≧ 3 (where Sg = 6 / (d · ρ), ρ [g / m ³ ] is the density of magnetic particles) (4)
Examples of the presence form of the magnetic fine particles and the polymer part in the magnetic particles of the present invention include, for example, a form in which the magnetic fine particles are uniformly dispersed in the continuous phase of the polymer part, and the magnetic fine particles and the polymer part have a core / shell structure. An unevenly distributed form can be taken.

  When the magnetic particle of the present invention has a core / shell structure, the polymer portion is included in at least one of the core portion and the shell portion covering the core portion. In this case, magnetic fine particles can be mixed in at least one of the core portion and the shell portion.

  More specifically, when the magnetic particles of the present invention have a core / shell structure, (i) when the shell portion contains magnetic fine particles and the core portion does not substantially contain magnetic fine particles, (ii) ) The case where the core part contains magnetic fine particles and the shell part substantially does not contain the magnetic fine particles, and (iii) the case where both the core part and shell part contain magnetic fine particles.

  In the case of (i) or (iii), magnetic particles can be formed by adsorbing magnetic fine particles on the surface of the core portion (core particles) to form a shell portion containing the magnetic fine particles. As these specific methods, for example, methods disclosed in Japanese Patent No. 1804757, Japanese Patent Application Laid-Open No. 2004-205481, and the like are suitable.

  Here, examples of the method for adsorbing the magnetic fine particles on the surface of the core part include the following methods.

  For example, the magnetic particles can be attached to the surface of the core by mixing the core and the magnetic particles and physically adsorbing the magnetic particles on the surface of the core. Here, “physical adsorption” means adsorption without chemical reaction. The principle of “physical adsorption” includes, for example, hydrophobic / hydrophobic adsorption, melt bonding or adsorption, fusion bonding or adsorption, hydrogen bonding, van der Waals bonding, and the like. For the adsorption using hydrophobic / hydrophobic adsorption, for example, the surface of the core part and the surface of the magnetic fine particles are selected to be hydrophobic or hydrophobized, and the core part and the magnetic fine particles are dry blended. Alternatively, after sufficiently dispersing in a well-dispersible solvent (for example, toluene, hexane) without damaging both the core portion and the magnetic fine particles, there is a method of volatilizing the solvent under the mixing condition.

  Alternatively, for example, by applying a physically strong force from the outside to realize the composite of the core portion and the magnetic fine particles, the magnetic fine particles can be attached to the surface of the core portion. Examples of the addition of a physically strong force include mortars, automatic mortars, ball mills, blade pressure type powder compression methods, those using mechanochemical effects such as mechanofusion methods, jet mills, hybridizers, etc. The thing using a medium impact method is mentioned. It is desirable that the physical adsorption force is strong in order to efficiently and firmly perform the composite. As the method, it is mentioned that the peripheral speed of the stirring blade is preferably 15 m / second or more, more preferably 30 m / second or more, and further preferably 40 to 150 m / second in a vessel with a stirring blade. When the peripheral speed of the stirring blade is lower than 15 m / sec, it may not be possible to obtain sufficient energy to adsorb the magnetic fine particles on the surface of the core portion. In addition, although there is no restriction | limiting in particular about the upper limit of the circumferential speed of a stirring blade, It determines automatically from points, such as an apparatus to be used and energy efficiency.

  Subsequently, the core part (core particle) with the magnetic fine particles attached to the surface is reacted with the monomer in the dispersion medium, whereby the shell part including the magnetic fine particles and the polymer part can be formed. Here, what is illustrated as a monomer for forming the polymer part mentioned later can be used as a monomer. In particular, by using a monomer having a carboxyl group represented by acrylic acid, methacrylic acid or the like as a monomer for forming the shell portion, the surface charge amount in terms of carboxylic acid described later can be adjusted.

  The magnetic particles of the present invention can be used by being dispersed in a dispersion medium. Examples of the dispersion medium include an aqueous medium. The aqueous medium is not particularly limited, and examples thereof include water and water containing an aqueous solvent. Examples of the aqueous solvent include alcohols (for example, ethanol, alkylene glycol, monoalkyl ether, etc.).

  Below, the component of the magnetic particle of this invention is demonstrated, respectively.

1-1. Magnetic Fine Particles The composition of the magnetic fine particles is not particularly limited as long as it is a magnetic substance, but iron oxide-based substances are typical, and MFe ₂ O ₄ (M = Co, Ni, Mg, Cu, Li _{0 .5} Fe _0.5 or the like), magnetite represented by Fe ₃ O ₄ , or γFe ₂ O ₃ . In particular, γFe ₂ O ₃ and Fe ₃ O ₄ are preferable as magnetic materials having high saturation magnetization and low residual magnetization.

  The magnetic fine particles used in the present invention are required to have little residual magnetization. For example, fine particles of ferrite and / or magnetite having a particle diameter of about 5 to 20 nm can be suitably used.

  Further, as the magnetic fine particles, those whose surface is subjected to a hydrophobic treatment can be used. The method for hydrophobizing the surface of the magnetic fine particles is not particularly limited. For example, a method of bringing a magnetic fine particle into contact with a magnetic fine particle and bonding a compound having a very high affinity portion and a hydrophobic portion in the molecule. Can be mentioned. Examples of such compounds include silane compounds represented by silane coupling agents and surfactants represented by long-chain fatty acid soaps.

  Hydrophobization with a silane compound is excellent in chemical resistance, particularly alkali resistance, and peeling of the magnetic material due to the removal of the hydrophobic portion during use, deterioration of magnetic performance, and detached magnetic fine particles and surfactant It is possible to effectively prevent contamination from entering the system due to floating of the water. In the present invention, it can be said that the surface is sufficiently hydrophobized when the magnetic fine particles whose surface has been hydrophobized can be satisfactorily dispersed in, for example, toluene.

1-2. Polymer Part The polymer part constituting the magnetic particles of the present invention is preferably composed of a vinyl polymer, and examples of the vinyl monomer used for the production thereof include styrene, α-methylstyrene, halogenated styrene, divinylbenzene, and the like. Aromatic vinyl monomers, vinyl acetates such as vinyl acetate and vinyl propionate, unsaturated nitriles such as acrylonitrile, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, Ethylenically unsaturated carboxylic acid alkyl esters such as 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, cyclohexyl acrylate, and cyclohexyl methacrylate Multifunctional (meth) acrylate such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, glycidyl acrylate, glycidyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, methoxy Examples thereof include (meth) acrylate having a functional group such as ethyl acrylate and methoxyethyl methacrylate. This vinyl polymer may be a homopolymer or a copolymer composed of two or more monomers selected from the vinyl monomers. Copolymerization of vinyl monomers with conjugated diolefins such as butadiene and isoprene, acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, diallyl phthalate, allyl acrylate, allyl methacrylate, etc. Copolymers with possible monomers can also be used. Here, by copolymerizing a monomer having a carboxyl group typified by acrylic acid, methacrylic acid and the like as a monomer in an appropriate amount, a surface charge amount in terms of carboxylic acid described later can be adjusted.

1-3. Volume average particle diameter The volume average particle diameter d of the magnetic particles of the present invention is 0.5 × 10 ^{−6 to} 5 × 10 ⁻⁶ [m], preferably 0.8 × 10 ⁻⁶ to 4 × 10 ^{−. 6} [m]. The volume average particle diameter d can be measured by a light scattering method, and more specifically, can be measured by a particle size measuring device that monitors Mie scattering. When the volume average particle diameter d is less than 0.5 × 10 ⁻⁶ [m], magnetic separation may be difficult, while when it exceeds 5 × 10 ⁻⁶ [m], the amount of protein binding is inferior. .

1-4. Carboxylic acid equivalent surface charge amount The carboxylic acid equivalent surface charge amount E of the magnetic particles of the present invention is 50 to 400 [μmol / g], preferably 70 to 300 [μmol / g].

  In the magnetic particles of the present invention, the “surface charge amount in terms of carboxylic acid” refers to a value obtained by measuring the acid present on the surface of the magnetic particles by conductometric titration. In the present invention, per 1 g of magnetic particles. The number of moles of carboxyl groups present on the particle surface. References describing a method for measuring the surface charge amount E in terms of carboxylic acid include, for example, “J. Electronal. Chem., Vol. 37 P. 161 (1972)” and Japanese Patent Application Laid-Open No. 10-270233. Can do.

  In both cases where the carboxylic acid equivalent surface charge E is less than 50 [μmol / g] and more than 400 [μmol / g], the bound protein is easily detached. The carboxylic acid equivalent surface charge amount E can be adjusted by the amount of carboxyl groups introduced to the particle surface. The amount of carboxyl groups introduced into the particle surface can usually be controlled by selecting the type and amount of the above-described monomer components used to form the polymer portion. That is, the carboxylic acid equivalent surface charge amount E can be controlled by selecting the type and amount of the monomer component used for forming the polymer portion.

1-5. Specific surface area In the magnetic particles of the present invention, “specific surface area” refers to the total surface area [m ² ] of magnetic particles per gram of magnetic particles.

The specific surface area S of the magnetic particles of the present invention is 2~50 ^[m 2 / g], preferably 5~30 ^[m 2 / g]. The specific surface area S of the magnetic particles of the present invention is an adsorption surface area measured by the BET method using argon gas. A specific method for measuring the specific surface area S of the magnetic particles of the present invention is described in Examples described later.

When the specific surface area S of the magnetic particles of the present invention is less than 2 [m ² / g], the amount of protein binding is inferior. On the other hand, when the specific surface area exceeds 50 [m ² / g], the bound protein tends to be detached.

  Moreover, the magnetic particle of this invention satisfy | fills the following formula | equation (4).

Specific surface area S / Spherical equivalent specific surface area Sg ≧ 3 (4)
Meet. In equation (4),
Sg = 6 / (d · ρ) (5)
It is. In equation (4), ρ is the density of the magnetic particles expressed in grams per m ³ , and can be calculated by measuring the specific gravity of the aqueous dispersion in which the magnetic particles are dispersed with a specific gravity bottle. In the formula (4), d is a volume average particle diameter and can be obtained from the above formula (1). Outside the range of formula (4), the amount of protein binding is poor.

  In addition, as a form (Form which the specific surface area S is 3 times or more of spherical equivalent specific surface area Sg) which satisfy | fills Formula (4), the following cases are mentioned, for example.

(I) Particle surface is uneven (ii) Particle is non-spherical (iii) Particle size distribution is broad Among these, preferred form is (i). In (ii), since the gravity sedimentation is fast, there is a possibility that the reaction becomes non-uniform when used in the reaction system. In (iii), the magnetic separation property may be inferior.

  As a preferred method for making the particle surface uneven, for example, a shell containing a polymer domain that dissolves in an organic solvent after adsorbing magnetic fine particles on a core part including a polymer part and a polymer domain that does not dissolve in the organic solvent. A method of removing the polymer domain dissolved in the organic solvent from the shell part by treating the particles with the organic solvent after forming the part so as to cover the core part.

1-6. Surface Charge Density In the present invention, the surface charge density E / S is a value obtained by dividing the carboxylic acid equivalent surface charge amount E by the specific surface area S.

Further, the magnetic particles of the present invention preferably have a surface charge density E / S of 30 [μmol / m ² ] or less, and 5 to 20 [μmol / m ² ] in order to keep protein detachment extremely low. Most preferably it is.

1-7. Applications The magnetic particles of the present invention can be used in a wide range of fields such as biochemistry, paints, paper, electrophotography, cosmetics, pharmaceuticals, agricultural chemicals, foods, and catalysts.

  The main use of the magnetic particles of the present invention is as a biochemical carrier. Further, by immobilizing a substance having a binding site for biotins (biotin or biotin derivative described later) on the surface of the magnetic particle of the present invention, it can be used as biotins binding particles. Examples of the substance having a biotin binding site include avidin and avidin derivatives such as streptavidin.

  When the magnetic particles of the present invention are used as biochemical carrier particles, for example, an antigen such as a protein (for example, IgG) or an antibody is bound to the magnetic particles of the present invention, and the antibody to be measured or an antigen antibody with the antigen Quantitative and qualitative detection using turbidity change of solution due to passive agglutination reaction based on reaction, chemical substance such as virus, bacteria, cells, hormones, dioxins, etc. as antigen by binding antibody to magnetic particles of the present invention For example, by binding a nucleic acid analog such as DNA to the magnetic particles of the present invention and binding the nucleic acid to the nucleic acid analog using hybridization, and collecting / detecting it. In addition, the chemical particles such as proteins and dyes that bind to nucleic acids are bound to the nucleic acid analogs for recovery and detection, and the magnetic particles of the present invention described above are For binding and collecting biotins or biotins with a molecule containing biotins or avidin and recovering and detecting them, and binding the antibody or antigen to the magnetic particles of the present invention for colorimetry Examples thereof include use of the magnetic particles of the present invention as a carrier for a method or enzyme immunoassay utilizing chemiluminescence. In general, any diagnostic item using a 96-well plate or the like as a carrier can be used in place of an automatic analyzer utilizing magnetism by using the magnetic particles of the present invention. Substances to be diagnosed include biologically derived proteins, hormones such as luteinizing hormone and thyroid stimulating hormone, various cancer cells, proteins serving as cancer markers such as prostate-specific markers and bladder cancer markers, and hepatitis B virus Viruses such as hepatitis C virus and herpes simplex virus, bacteria such as Neisseria gonorrhoeae and MRSA, fungi such as Candida and cryptocox, protozoa and parasites such as Toxoplasma, or viruses, bacteria, fungi, protozoa and parasites Examples of such components include environmental pollutants such as proteins, nucleic acids, and dioxins, and chemical substances such as pharmaceuticals such as antibiotics and antiepileptics.

  The use of the magnetic particles of the present invention is not limited to the use for biochemical carriers, and can be used, for example, in the above-described fields.

2. Examples Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

2-1. Evaluation method 2-1-1. Volume average particle diameter d
Using an aqueous dispersion of magnetic particles, the volume average particle size d was measured by a laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation) SALD-200V.

2-1-2. Carboxylic acid equivalent surface charge E
Using an aqueous dispersion containing 1 g of solid content of magnetic particles, the apparent surface charge amount was determined by conductometric titration described in JP-A-10-270233, and only the dispersion medium (water) was used. The background charge amount was determined by the same measurement, and the carboxylic acid equivalent surface charge amount E of the magnetic particles was determined from the difference between these charge amounts.

2-1-3. Specific surface area S
About the heat-dried magnetic particle, the specific surface area S by argon gas adsorption | suction was measured using the fully automatic gas vapor | steam adsorption amount measuring apparatus (The Yuasa Ionics Co., Ltd. product) autosorb-1.

2-1-4. Spherical equivalent specific surface area Sg
The density ρ _disp of the aqueous dispersion containing about 10% by weight of magnetic particles was measured with a specific gravity bottle of 5 [ml]. Further, the solid content ratio f of this aqueous dispersion was determined from the change in weight before and after drying at 200 ° C. for 5 minutes, and the density ρ of the magnetic particles was determined from the following formula (6). In equation (6), ρ _water is the density of water.

1 / ρ _disp = (f / ρ) + ((1−f) / ρ _water ) (6)
Further, the spherical equivalent specific surface area Sg was determined by substituting the density ρ and the volume average particle diameter d of the magnetic particles into the above formula (5).

2-1-5. Protein binding amount To an aqueous dispersion having a solid content concentration of 1% in which 10 [mg] of magnetic particles are dispersed, an aqueous solution of 1-ethyl-3-dimethylaminopropylcarbodiimide hydrochloride (manufactured by Dojin Chemical) is added at room temperature to 2 The carboxyl group was activated by stirring for a period of time. Next, mouse IgG corresponding to 200 [μg] was added as a protein, and the mouse IgG was immobilized by rotating and stirring at room temperature for 8 hours, and then washed three times with a phosphate buffer to prepare protein-immobilized particles. .

  With respect to the protein-immobilized particles, the amount of protein binding per 1 [mg] of magnetic particles was determined by BCA method (color development by protein and bicinchoninic acid was quantified by absorbance at 562 nm).

2-1-6. Protein Desorption Amount The above protein-immobilized particles are dispersed in an aqueous solution containing 0.1% BSA (bovine serum albumin) and 0.01% Triron X-100 so as to form a 1% particle dispersion. Stored for days. Next, the protein concentration in the supernatant desorbed from the particles during storage was quantified by sandwich ELISA using an anti-mouse primary antibody / HRP-labeled anti-mouse secondary antibody by a plate method.

2-2. Example 1
With reference to the polymerization method described in JP-A-7-238105, styrene / divinylbenzene = 95/5 copolymer particles (average particle size 1.6 μm) were prepared, and after polymerization, only the particles were removed by centrifugation. Further, it was washed with water, dried and pulverized. Let this be a core part (core particle).

  Next, after adding acetone to oily magnetic fluid (trade name: “EXP series”, manufactured by Ferrotec Co., Ltd.) to precipitate particles and magnetically separate them, the supernatant is discarded and the precipitate is dried to make it hydrophobic. Ferrite-based magnetic fine particles (average primary particle size: 0.02 μm) having a treated surface were obtained.

  Next, the core portion 15g and the magnetic fine particles 15g whose surface has been hydrophobized are thoroughly mixed with a mixer, and this mixture is used with a hybridization system NHS-0 type (manufactured by Nara Machinery Co., Ltd.) By treating the blade (stirring blade) at a peripheral speed of 100 m / sec (16200 rpm) for 5 minutes to adsorb the magnetic fine particles to the core portion, the magnetic mother particles (1) having an average number particle diameter of 2.0 μm are obtained. Obtained.

  Next, 750 g of an aqueous solution containing 0.25% by weight of sodium dodecylbenzenesulfonate and 0.25% by weight of a nonionic emulsifier (trade name: “Emulgen 150”, manufactured by Kao Corporation) was charged into a 1 L separable flask. Next, 30 g of the magnetic mother particles (1) were added, dispersed with a homogenizer, and then heated to 60 ° C. Subsequently, 30 g of cyclohexyl methacrylate, tert-dodecanethiol were added to 50 g of an aqueous solution containing 0.5% by weight of sodium dodecylbenzenesulfonate and 0.5% by weight of a nonionic emulsifier (trade name: “Emulgen 150”, manufactured by Kao Corporation). 1.2 g and a pre-emulsion in which 1.5 g of tertiary butyl peroxy 2-ethylhexanate (manufactured by NOF Corporation; Perbutyl O) was added and dispersed in the 1 L separable flask controlled at 60 ° C. over 2 hours. (The above is the first step of shell formation).

  Next, the reaction solution was cooled to room temperature, and then added to 50 g of an aqueous solution containing 0.5% by weight of sodium dodecylbenzenesulfonate and 0.5% by weight of a nonionic emulsifier (trade name: “Emulgen 150”, manufactured by Kao Corporation). A pre-emulsion in which 0.375 g of tertiary butyl peroxy 2-ethylhexanate (trade name: “Perbutyl O”, manufactured by NOF Corporation) was added and dispersed was introduced into the 1 L separable flask, For 15 hours. Next, 2.25 g of methacrylic acid and ethylene glycol were added to 50 g of an aqueous solution containing 0.5% by weight of sodium dodecylbenzenesulfonate and 0.5% by weight of a nonionic emulsifier (trade name: “Emulgen 150”, manufactured by Kao Corporation). The pre-emulsion in which 9.0 g of dimethacrylate was added and dispersed was put into the 1 L separable flask stirred at room temperature for 15 hours, and further stirred at room temperature for 2 hours. Next, the temperature of the 1 L separable flask was raised to 80 ° C., and the polymerization was further continued for 2 hours to complete the reaction (the second stage of shell formation).

  The obtained aqueous dispersion of magnetic particles was subjected to magnetic purification and gravity sedimentation purification, and then an aqueous dispersion of magnetic particles having a solid content concentration of 1% was obtained.

  Next, in order to remove water from the aqueous dispersion of magnetic particles, the aqueous dispersion was washed twice with 1 L of acetone. Next, the particles were dispersed in 1 L of acetone and stirred for 2 hours to bring the particles into contact with acetone (organic solvent). Thereby, a part of the polymer portion was eluted from the particles using acetone. Subsequently, it was washed twice with 1 L of acetone, and further washed with water to remove acetone, thereby obtaining magnetic particles having an uneven particle surface. Table 1 shows the evaluation results of the magnetic particles.

2-3. Example 2 and Comparative Examples 1 and 2
Magnetic particles having the physical properties shown in Table 1 were obtained in the same manner as in Example 1 except that the amount of the monomer used in Example 1 was changed.

  As shown in Table 1, since the magnetic particles of Examples 1 and 2 satisfy all of the above formulas (1) to (4), the amount of protein binding is large, and the bound protein The amount of desorption was small.

  On the other hand, the magnetic particles of Comparative Example 1 having a carboxylic acid equivalent surface charge amount E of less than 50 [μmol / g] have a large amount of protein desorption and the magnetic particles of Comparative Example 2 having an S / Sg of less than 3. Had less protein binding.

Claims (3)

Magnetic particles comprising magnetic fine particles and a polymer portion and satisfying the following formulas (1) to (4).
Volume average particle diameter d = 0.5 × 10 ^{−6 to} 5.0 × 10 ⁻⁶ [m] (1)
Carboxylic acid equivalent surface charge E = 50 to 400 [μmol / g] (2)
Specific surface area S = 2 to 50 [m ² / g] (3)
Specific surface area S / spherical equivalent specific surface area Sg ≧ 3 (where Sg = 6 / (d · ρ), ρ [g / m ³ ] is the density of magnetic particles) (4) In claim 1,
Magnetic particles having a surface charge density E / S of 30 [μmol / m ² ] or less. In claim 1 or 2,
Magnetic particles with proteins bound to the surface.