JP2006131771A - Polymer-coated magnetic bead and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide polymer-coated magnetic beads with large saturation magnetization and small residual magnetization and suitable for a carrier in high speed bioscreening, which are nanometer size ferrite microparticles thoroughly coated with a substance specifically reactive with a target substance, which can fix the target substance on the surface in large quantity whereas nonspecific adsorption of a substance other than the target is inhibited, where deactivation of a protein such as a bioreceptor bound to the particle is prevented, and to provide a method for producing the same. <P>SOLUTION: This polymer beads in which ferrite nanoparticles are coated with a polymer is obtained by the steps of strongly hydrophobizing the surface of the ferrite nanoparticle by modifying the surface with a highly hydrophobic saturated fatty acid, adding and dispersing the hydrophobized nanoparticle to a hydrophobic monomer liquid such as styrene to obtain a ferrite-dispersed monomer liquid, mixing a GMA (glycidyl methacrylate) monomer with the ferrite-dispersed monomer liquid, dropping the mixed monomer liquid into deionized water containing a polymerization initiator, stirring and applying ultrasonic waves to form an emulsion and polymerizing the emulsified monomer mixture. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polymer-coated magnetic bead and a method for producing the same.

  Currently, using specific adsorption that works between chemical substances that can be drug candidates and proteins that are biological receptors, between a pair of DNA single strands, between DNA double strands and chemical substances, Bio-screening used to isolate / identify drug candidates, proteins, DNA, etc., and to perform protein-protein interactions, DNA isolation / base sequence identification, etc. at high speed by using magnetic beads There is an increasing expectation for technology development that enables a large amount of processing, that is, high throughput.

  If high-speed bioscreening technology is established, the development of new drugs with better efficacy than existing drugs and the development of so-called tailor-made therapies that provide treatments suitable for patients based on their disease and individual genetic information Is expected to be possible. The magnetic fine particles used in this bioscreening are: (1) In order to fix as much of the target substance as possible on the surface as much as possible, the size is as small as possible and the specific surface area (surface area per unit volume) (2) A substance other than the target is hardly adsorbed on the surface, that is, non-specific adsorption is unlikely to occur, (3) The surface does not deactivate the protein, (4) Aqueous solution There are four points that are required to be dispersed without agglomeration, but to be quickly separated using a magnet and easily redispersed when the magnet is removed.

  Magnetic polymer beads currently in practical use are on the order of micrometers and are relatively large, and therefore have a relatively small specific surface area. Therefore, when used for bioscreening, the above chemical substances and biological receptors are used. There was a problem that the amount that could be fixed on the surface was small and the efficiency of screening was low. Therefore, although it is desirable to use magnetic beads having a particle size on the order of nanometers with a large specific surface area, all existing magnetic beads of nanometer size have weak magnetization, and magnetic separation using these is difficult. was there.

  Further, among the existing polymer-coated magnetic beads, those in which ferrite particles are coated with styrene polymer have a problem that it is difficult to bind to proteins such as biological receptors. On the other hand, when the ferrite particles are coated with dextran, dextran has a hydroxyl group and can bind to proteins, etc., but the binding force between dextran and ferrite particles is weak, and dextran itself However, since the mechanical strength was relatively small, there was a problem that dextran was detached from the particles during repeated use.

  As polymer magnetic beads suitable for specific adsorption, D.I. Horak et al. Have reported that magnetite nanoparticles are coated with polyglycidyl methacryl (poly-GMA) polymerized by polymerizing glycidyl methacrylate (GMA) ester (Non-patent Document 1). Since the glycidyl group of poly-GMA reacts well with an amino group or the like, adsorption specificity can be given by binding a protein which is a specific biological receptor through this group. However, these coated particles have a problem that their magnetization is weak because they are relatively large in a micrometer size and the content of magnetite responsible for magnetism is as small as 10 to 20% by weight.

On the other hand, the polymer-coated magnetic particles of Patent Document 1 have a magnetite content as high as 32% by weight and a nano particle size of 300 nm. However, since the coating polymer is polystyrene, it has the above-mentioned problems, and sodium dodecyl benzene sulfonate is used as an emulsifier. Therefore, the sodium dodecyl benzene sulfonate as the emulsifier remains on the particle surface, There is a problem that the protein may be inactivated during screening.
JP 2004-99844 A D. Horak, N. Semenyuk, F. Lednicky, J. Polym. Sci., Part A: Polym. Chem. 2003, 41, 1848

  An object of the present invention is a nanometer-sized fine particle in which ferrite particles are sufficiently coated with a substance that specifically reacts with a target substance to solve each of the problems described above, and a large amount of the target substance can be immobilized on the surface. In addition, the present invention provides a polymer-coated magnetic bead in which nonspecific adsorption of a substance other than the target is prevented. Another object of the present invention is to produce polymer-coated magnetic beads without using an emulsifier, thereby preventing the deactivation of proteins bound to the particles and increasing the content of ferrite fine particles in the polymer-coated magnetic beads. Polymer-coated magnetic beads and their manufacture suitable for carriers for high-speed bioscreening, with high saturation magnetization while reducing residual magnetization, and can be quickly separated using a magnet and easily redispersed when the magnet is removed To provide a law.

  The inventors of the present invention conducted intensive studies to obtain polymer-coated magnetic beads that overcome the above-mentioned problems of the prior art. As a result, the following results were obtained.

  First, magnetite particles having an average particle size adjusted to about 7 nm as particles responsible for magnetism were prepared by a coprecipitation method. Next, the surface of the magnetite particles was treated with highly hydrophobic sodium stearate to strongly hydrophobize the surface. In this way, the magnetite whose surface has been treated with stearic acid is added and dispersed in a styrene monomer liquid to obtain a magnetite dispersed monomer liquid. The magnetite dispersed monomer liquid is mixed with a GMA monomer, and this is used as a polymerization initiator for ammonium persulfate (peroxoniton). As a result of adding dropwise to deionized water containing ammonium sulfate), stirring and ultrasonic irradiation, it was possible to form an emulsion in which monomer particles dispersed with magnetite were dispersed in continuous phase water without using an emulsifier. By polymerizing this and further adding GMA to this liquid and proceeding with polymerization, polymer-coated magnetic beads in which magnetite was coated with the polymer could be obtained.

  The beads made in this way are nanometer-sized microbeads coated with a polymer whose surface binds to a substance that specifically reacts with the target substance, and the target substance can be immobilized in large quantities on the surface and bonded to the particles. It was found that protein deactivation can be prevented, the content of ferrite fine particles in the beads can be increased, and the saturation magnetization of the beads can be increased. Therefore, as a result of developing this research based on these results, the inventors have reached the invention described below.

  The polymer-coated magnetic beads of the present invention are ferrite nanoparticles having an average particle diameter of 4 nm or more and 20 nm or less, saturated fatty acids that modify the surface of the ferrite nanoparticles, and the main components of the polymer-coated magnetic beads, and are modified with saturated fatty acids. And the hydrophobic polymer for fixing the ferrite nanoparticles, the average particle diameter of the polymer-coated magnetic beads is 200 nm or less, the content of the ferrite nanoparticles is 30% by weight or more, and the surface of the polymer-coated magnetic beads is It is composed of a polymer.

  The polymer-coated magnetic beads of the present invention have a high content ratio of ferrite nanoparticles contained in the beads and a large saturation magnetization, and the ferrite nanoparticles are well coated with a polymer. This is presumably because the ferrite nanoparticles are surface-modified with a saturated fatty acid such as stearic acid and have very strong hydrophobicity and high affinity for hydrophobic monomers.

  In the polymer-coated magnetic beads of the present invention, the ferrite nanoparticle has an average particle diameter of 4 nm or more and 20 nm or less, so that it has a high saturation magnetization, and when the magnetic field is zero, the residual magnetization is almost zero. Can do. If the average particle diameter of the ferrite nanoparticles is less than 4 nm, it is difficult to obtain a high saturation magnetization. On the other hand, if the average particle diameter exceeds 20 nm, it is difficult to make the residual magnetization almost zero. The average particle diameter of such ferrite nanoparticles is more preferably 5 nm or more and 15 nm or less.

  The polymer-coated magnetic beads of the present invention have an average particle size of 200 nm or less, and if the average particle size of the polymer-coated magnetic beads exceeds 200 nm, the specific surface area of the beads becomes small and high specific adsorption cannot be obtained. . More preferably, the average particle size of the polymer-coated magnetic beads is 180 nm or less. On the other hand, from the viewpoint of handling, the average particle size of the polymer-coated magnetic beads is preferably 30 nm or more, and more preferably 50 nm or more.

  Furthermore, in the polymer-coated magnetic beads of the present invention, the content of ferrite nanoparticles is 30% by weight or more. When the content of ferrite nanoparticles is less than 30% by weight, high saturation magnetization cannot be obtained, and the excellent characteristics of the polymer-coated magnetic beads of the present invention in magnetic separation cannot be obtained. The content of ferrite nanoparticles is more preferably 35% by weight or more.

  The hydrophobic polymer used for the polymer-coated magnetic beads of the present invention is preferably a polymer formed by soap-free polymerization of a styrene monomer and a glycidyl methacrylate (GMA) monomer.

  By using polystyrene obtained by polymerizing styrene having strong hydrophobicity as the polymer of the polymer-coated magnetic beads of the present invention, a strong affinity can be obtained with the hydrophobized ferrite nanoparticles. Polystyrene is suitable as a main constituent material of beads because it has an appropriate hardness. On the other hand, since the glycidyl group of GMA reacts well with an amino group or the like, a bead having specific adsorption can be obtained by binding a protein or the like which is a biological receptor through this group. Further, by increasing the GMA ratio on the bead surface, the amount of adsorption can be remarkably increased by taking advantage of the large specific surface area of the beads.

  In the present invention, emulsification can be carried out without using an emulsifier such as a surfactant. Therefore, since soap-free emulsion polymerization is carried out, there is no fear that the bioactive substance is deactivated by the emulsifier.

  The polymer-coated magnetic beads of the present invention have a large ratio of ferrite nanoparticles contained in the beads and a large saturation magnetization, while the magnetite particles inside the polymer beads are each coated with stearic acid and the particles are well isolated. In addition, since the particle diameter itself exhibits superparamagnetism, the remanent magnetization after removing the magnetic field is as small as about 0.1 emu / g, so that the particles after magnetic separation can be easily redispersed. Has the advantage of being

  Moreover, since the polymer-coated magnetic beads of the present invention have ferrite nanoparticles completely trapped inside the polymer coating, only the properties of the polymer appear on the surface, and nonspecific adsorption and protein deactivation by the ferrite surface occur. There is no fear.

  The method for producing a polymer-coated magnetic bead of the present invention comprises a step of modifying the surface of a ferrite nanoparticle with saturated fatty acid to obtain a hydrophobized ferrite nanoparticle, and the hydrophobized ferrite nanoparticle is introduced into a hydrophobic monomer liquid and dispersed. A step of obtaining a ferrite nanoparticle-dispersed monomer solution, a step of adding this ferrite nanoparticle-dispersed monomer solution to water containing a hydrophilic initiator to obtain an emulsion, and a polymer obtained by polymerizing the monomers of this emulsion And a polymerization step to be formed.

  According to the present invention, since an emulsion can be obtained without using an emulsifier, polymer-coated magnetic beads can be produced by soapless emulsion polymerization. Thus, since the amount of ferrite nanoparticles fixed is large, saturation magnetization is large, and polymer-coated magnetic beads in which ferrite nanoparticles are well coated with a polymer can be obtained.

  In the method for producing polymer-coated magnetic beads of the present invention, a monomer liquid obtained by adding a glycidyl methacrylate monomer liquid to a styrene monomer liquid can be particularly preferably used as the hydrophobic monomer liquid.

  By using a highly hydrophobic styrene monomer solution, it is possible to obtain a strong affinity between the hydrophobized ferrite nanoparticles and the monomer, and due to the moderate hardness of polystyrene obtained by curing this, The strength of the obtained beads can be ensured. Further, by utilizing the fact that the glycidyl group of GMA reacts well with an amino group or the like, a bead having specific adsorption can be obtained by binding a protein or the like which is a specific biological receptor through this group.

  In addition, by adding additional GMA monomer in the polymerization process, beads with a significantly increased adsorption amount can be obtained by making the bead surface a GMA polymer layer or increasing the GMA ratio of the bead surface. be able to.

  The polymer-coated magnetic beads of the present invention are coated with good affinity to a hydrophobic polymer because the surface of the ferrite particles is strongly hydrophobized, and this hydrophobic polymer prevents nonspecific adsorption and is specific. It is a polymer that can be adsorbed. Further, since there is no emulsifier on the polymer surface of the polymer-coated magnetic beads of the present invention, the polymer-coated magnetic beads have an excellent property of having a small deactivation effect on proteins. In addition, since the saturation magnetization is strong but the residual magnetization is small, the magnetic attraction force is strong and the redispersibility is good. Therefore, in the treatment using the polymer-coated magnetic beads, the magnetic separation ability is excellent. As described above, by using the polymer-coated magnetic beads of the present invention, various treatments utilizing specific adsorption and magnetic separation can be remarkably improved.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a simplified flow chart of steps in an embodiment of a method for producing polymer-coated magnetic beads of the present invention.

  In FIG. 1, first, in the step of ferrite nanoparticle production 101, ferrite nanoparticles 102 having a predetermined average particle diameter are formed by, for example, a method of pouring an aqueous solution containing divalent iron ions and trivalent iron ions into an alkaline aqueous solution and precipitating. Make it. Next, in the step of saturated fatty acid modification 103, an alkaline aqueous solution of saturated fatty acid is allowed to act on the ferrite nanoparticles, and then the acid is made acidic by adding acid to thereby modify the surface of the ferrite nanoparticles with saturated fatty acids. Subsequently, in the washing / drying 104 step, the ferrite nanoparticles finely surface-modified with saturated fatty acids are washed with pure water and then dried to obtain hydrophobized ferrite nanoparticles 105.

  Next, in the step of dispersion 106 in a monomer solution having a vinyl group, the ferrite nanoparticle 105 surface-modified with a saturated fatty acid and hydrophobized is dispersed in a monomer solution such as styrene or GMA. 107 is obtained. Next, the ferrite nanoparticle-dispersed monomer liquid 107 is poured into water containing a polymerization initiator, and the ferrite nanoparticle-dispersed monomer liquid 107 is used as a polymerization initiator in the process of dispersion 106 in a monomer solution having a vinyl group. It is added dropwise to the deionized water contained and emulsified by stirring and ultrasonic irradiation to obtain an emulsion 109. Subsequently, in the process of polymerization 110, this emulsion 109 is stirred and heated to perform soap press emulsion polymerization, and magnetic recovery 111 is performed in the liquid, and those having weak magnetism are left in the liquid and have sufficient magnetism. The polymer-coated magnetic beads 112 can be obtained by collecting only those.

  Further, when a biological receptor is bound to the polymer-coated magnetic beads 112 in the step of biological receptor binding 113, biological receptor-bound magnetic beads 114 having specific adsorptivity can be obtained. These beads have magnetism and can be recovered by magnetic separation using a magnet. In addition, in the step of dispersion 106 in the monomer solution having a vinyl group, a monomer solution in which GMA is added to styrene is used, and in the polymerization step 110, a GMA monomer is additionally added when polymerization proceeds and further polymerization is performed. By performing the above, it is possible to obtain polymer-coated magnetic beads 112 having GMA formed on the surface layer.

  In this way, for example, the polymer-coated magnetic beads 112 and the biological receptor-bound magnetic beads 114 having the schematic cross-sectional view shown in FIG. 2 can be obtained. In FIG. 2A, the surface of the magnetite nanoparticles 201 is modified with stearic acid 202, and a plurality of magnetite nanoparticles 201 are held in a styrene / GMA copolymer 203. FIG. 2B shows the GMA polymer 204 coated on the surface of the polymer-coated magnetic beads shown in FIG. Further, in FIGS. 2C and 2D, a specific biological receptor 205 is bound to the surface of FIGS. 2A and 2B to have adsorption specificity. Is.

  In order for these polymer-coated magnetic beads to exhibit a certain degree of strong magnetism and to exhibit superparamagnetism in which residual magnetization does not remain when the magnetic field is removed, the particle size of the ferrite nanoparticles is preferably 5 nm or more, and 20 nm or less. It is preferable that it is 15 nm or less.

  In addition to magnetite, the ferrite nanoparticles can use various ferrites such as maghemite, nickel ferrite, nickel zinc ferrite, manganese ferrite, manganese zinc ferrite, cobalt ferrite, cobalt zinc ferrite, and solid solution between them. . Moreover, these ferrite nanoparticles can use various nanometer-sized ferrite particle manufacturing methods such as coprecipitation method and ferrite plating method.

Hydrophobization of the ferrite nanoparticles is preferable because modification with stearic acid (C ₁₇ H ₃₅ COOH) can be strongly hydrophobized. In addition, palmitic acid (C ₁₅ H ₃₅ COOH), myristic acid (C ₁₃ H ₃₅ COOH) ), Lauric acid (C ₁₁ H ₃₅ COOH) and the like, and fatty acids having 11 to 19 carbon atoms in the alkyl group can be used. Conventionally, oleic acid is often used for hydrophobizing surface treatment of ferrite fine particles. However, oleic acid has a double bond and is hydrophilic, and is not sufficient for hydrophobization of the present invention. In contrast, when saturated fatty acids such as stearic acid are used, strong hydrophobicity can be imparted, and by adding this to a hydrophobic monomer liquid such as styrene monomer, a ferrite nanoparticle-dispersed monomer having good dispersion can be obtained. it can.

  Ferrite nanoparticles whose surface is modified with saturated fatty acids such as stearic acid, which are very hydrophobic in this way, have a high affinity for hydrophobic monomers such as styrene monomers, so there are many inside the polymer beads thus obtained. Of ferrite nanoparticles. The polymer-coated magnetic beads thus obtained can have a higher saturation magnetization than conventional beads. On the other hand, in this polymer-coated magnetic bead, the ferrite nanoparticles inside the polymer bead are each coated with stearic acid and the particles are isolated from each other and are superparamagnetic, so that the residual magnetization when the magnetic field is zero is almost zero. can do. For this reason, it is possible to speed up magnetic operations such as magnetic separation.

  The monomer has a vinyl group and can be polymerized by polymerization. For example, it is preferable to polymerize using styrene as a monomer because a moderate strength can be obtained in the polymer-coated magnetic beads. Further, by polymerizing using a monomer having a glycidyl group in addition to a vinyl group, such as GMA, and having a glycidyl group on the surface, a protein of a biological receptor having, for example, an amino group can be bound through the glycidyl group. In this way, the adsorption to the beads is specific adsorption through a biological receptor, and adsorption to particles due to nonspecific adsorption of a substance other than the target can be prevented.

  The monomer that can be used in the present invention is a monomer having a functional group capable of radical polymerization, and examples of such a monomer include styrene, α-methylstyrene, o-vinyltoluene, m-vinyltoluene, and p-vinyltoluene. Aromatic vinyl compounds such as divinylbenzene; unsaturated carboxylic acids such as (meth) acrylic acid and crotonic acid; methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) ) Acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene Glycol di (meth) acrylate, tri (Meth) acrylates such as tyrolpropane tri (meth) acrylate and glycidyl (meth) acrylate; vinyl cyanide compounds such as (meth) acrylonitrile and vinylidene cyanide; vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, And halogenated vinyl compounds such as tetrafluoroethylene. Of these monomers, aromatic vinyl compounds and (meth) acrylates are particularly preferable. Moreover, these monomers can be used individually or in mixture of 2 or more types. At least one of these monomers preferably has a functional group capable of binding another substance such as a protein to the surface of the polymer coating after the formation of the polymer.

  For this reason, after emulsifying the monomer liquid containing styrene as a main component and dispersing the ferrite nanoparticles and proceeding polymerization to some extent, GMA is further added to this emulsion liquid to proceed further polymerization, so that polystyrene having an internal strength is obtained. By covering the surface with poly-GMA having a large amount of glycidyl groups, polymer-coated magnetic beads capable of further enhancing the specific adsorption ability can be obtained.

  As the polymerization initiator, various water-soluble peroxides such as ammonium persulfate (ammonium peroxonisulfate) and potassium persulfate (potassium peroxonisulfate) can be used.

  Furthermore, it is coated with a GMA polymer that can significantly reduce non-specific adsorption, and adsorption of a substance other than the target to the particles can be reduced, which is suitable for high-speed bioscreening. Another advantage of this particle is that its remanent magnetization is as small as about 0.1 emu / g. This is because the magnetite particles inside the polymer beads are each coated with stearic acid, so that the particles are isolated from each other and are superparamagnetic. Therefore, the particles easily redisperse after magnetic separation. In the present invention, since “soap-free polymerization” in which polymer particles are formed without using a surfactant is used, the surfactant does not deactivate the physiologically active substance, and the type of raw material used for particle formation There is an advantage that there are few.

  Such a polymer-coated magnetic bead is useful as a magnetic carrier used for bio-screening for analysis of selective adsorption between proteins or chemical substances, DNA isolation, base sequence identification, and the like.

All pure water used in this example was previously substituted with nitrogen by nitrogen bubbling. In 32 ml of this treated pure water, 0.332 g of FeCl ₂ .4H ₂ O and 0.902 g of FeCl ₃ .6H ₂ O were dissolved, and this was poured into 100 ml of 0.2 mol / l sodium hydroxide solution. In a water bath at 0 ° C., the mixture was stirred for 3 minutes at 300 rpm using a propeller to form magnetite fine particles.

  As a result of TEM observation of the obtained magnetite particles, the average particle size was about 7 nm, and the magnetic measurement showed that the saturation magnetization was 74 emu / g. Next, pure water in which 100 mg of sodium stearate was dissolved was poured into this magnetite fine particle suspension, and the mixture was stirred for 10 minutes, whereby stearic acid was introduced into the magnetite surface to make it hydrophobic. Thereafter, 2 mol / l hydrochloric acid was added to this suspension, the pH was lowered to 3 to 5, the particles were aggregated and magnetically collected.

  The recovered magnetite particles are washed with pure water and dispersed in 3 ml of styrene monomer, and then 0.9 ml is mixed with 0.1 ml of GMA in a four-necked flask, which contains 0.0138 g of potassium persulfate. 40 ml of pure water was poured, and ultrasonic waves were irradiated for 5 minutes while stirring with a stirring rod. Thereafter, the mixture was stirred for 15 minutes at 200 rpm using a stirring rod, and then the monomer was polymerized at 70 ° C. for 16 hours at 200 rpm in a nitrogen atmosphere to obtain polymer-coated magnetic beads.

  The particle size distribution obtained by TEM observation of the polymer-coated magnetic beads thus obtained is shown as (Example 1) in FIG. As can be seen in FIG. 3 (Example 1), the median value of the particle size distribution was 92.8 nm. Further, the results of magnetic measurement of the polymer-coated magnetic beads using a sample vibration type magnetization measuring apparatus are shown in FIG. 4 as (Example 1). Indicated. As shown in FIG. 4, the saturation magnetization was 10.6 emu / g.

  Further, among the polymer-coated magnetic beads thus obtained, the particle size distribution obtained by conducting transmission electron microscope (TEM) observation on those obtained by magnetic recovery in a solution is shown as FIG. 5 (Example 1). It was. As seen in FIG. 5 (Example 1), the median particle size was 165 nm. The results of the magnetic measurement are shown as (Example 1) in FIG. As seen in (Example 1) of FIG. 6, the saturation magnetization was 31 emu / g.

  When the saturation magnetization value of the polymer-coated magnetic beads obtained by magnetic recovery in the solution and the saturation magnetization value of the magnetite are calculated, about 41% by weight of the beads are occupied by magnetite. Compared with magnetic beads, it contains much more magnetic particles and shows a high saturation magnetization value.

  In addition, this particle is nano-sized with a median particle size of 165 nm, has a large specific surface area, has a glycidyl group on the surface, and can bind a specific biological receptor or the like to prevent nonspecific adsorption. It was found that screening operations can be performed efficiently by using these beads.

  Magnetite particles were synthesized by the same method as described in Example 1, and surface modification with stearic acid was performed. The magnetite modified with stearic acid was redispersed in a smaller amount of styrene monomer solution than in Example 1, that is, 2 ml of styrene monomer solution, and polymerization was performed in the same procedure as in Example 1.

  The particle size distribution of the beads thus obtained is shown as (Example 2) in FIG. As seen in (Example 2) of FIG. 3, the median value of the particle size distribution was 185 nm. Further, the magnetization characteristics of the obtained beads are shown as (Example 2) in FIG. As shown in FIG. 4 as (Example 2), the saturation magnetization was 18.8 emu / g.

  As a result of TEM observation of the polymer-coated magnetic beads thus obtained by magnetic recovery in solution, as shown in FIG. 5 (Example 2), the median particle diameter was 165 nm. As a result of the magnetic measurement, the saturation magnetization was 27.8 emu / g as shown in FIG. 6 as (Example 2).

  The polymer-coated magnetic beads thus obtained were found to be beads having a uniform particle size without exposure of the magnetite particles to the surface of the polymer particles as seen in the TEM image shown in FIG. The residual magnetization was about 1.0 emu / g.

  When the result of Example 2 is compared with the result of Example 1, the size of the synthesized particles is large and the saturation magnetization becomes stronger even though the size and saturation magnetization of the magnetically recovered particles are not much changed. I understand that. From this result, it was found that increasing the amount of magnetite relative to the monomer under the conditions of Example 2 contained a large amount of beads or magnetite, and as a result, the ratio of magnetite in the whole beads could be increased. .

  Nanometer-sized polymer-coated magnetic beads according to the present invention can increase the amount of specific adsorption, prevent deactivation and non-specific adsorption of proteins by different surface active agent groups, have high saturation magnetization and low residual magnetization. Therefore, it will be widely used as a magnetic bead for bioscreening.

The flow chart of the process in one embodiment of the manufacturing method of the polymer covering magnetic bead of the present invention is simply shown. It is the figure which showed typically one Embodiment of the polymer covering magnetic bead with sectional drawing. It is the figure which showed the particle size distribution obtained by performing TEM observation about the polymer covering magnetic bead manufactured in Example 1 and Example 2. FIG. It is the figure which showed the magnetization characteristic obtained by performing a magnetic measurement about the polymer covering magnetic bead manufactured in Example 1 and Example 2. FIG. It is the figure which showed the particle size distribution obtained by performing TEM observation about what was obtained by carrying out magnetic recovery in the solution among the polymer covering magnetic beads manufactured in Example 1 and Example 2. FIG. It is the figure which showed the magnetic characteristic by performing a magnetic measurement about what was obtained by carrying out magnetic recovery in the solution among the polymer covering magnetic beads manufactured in Example 1 and Example 2. FIG. 4 is a TEM image of polymer-coated magnetic beads produced in Example 2. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 101 ... Ferrite nanoparticle preparation, 102 ... Ferrite nanoparticle, 103 ... Saturated fatty acid modification, 104 ... Washing and drying, 105 ... Hydrophobized ferrite nanoparticle, 106 ... Dispersing in the monomer liquid which has a vinyl group, 107 ... Ferrite nanoparticle dispersion Monomer solution, 108 ... injected and emulsified in water (containing polymerization initiator), 109 ... emulsion solution, 110 ... polymerization, 111 ... magnetic recovery, 112 ... polymer-coated magnetic beads, 113 ... binding biological receptors, 114 ... binding biological receptors Magnetic beads, 201 ... magnetite nanoparticles, 202 ... stearic acid, 203 ... styrene-GMA copolymer, 204 ... GMA polymer, 205 ... biological receptor.

Claims (6)

A polymer-coated magnetic bead,
Ferrite nanoparticles having an average particle size of 4 nm to 20 nm,
A saturated fatty acid that modifies the surface of the ferrite nanoparticles, and
A hydrophobic polymer that fixes the ferrite nanoparticles modified with the saturated fatty acid and is a main constituent of the polymer-coated magnetic beads, and the polymer-coated magnetic beads have an average particle size of 200 nm or less, and the ferrite A polymer-coated magnetic bead, wherein the content of nanoparticles is 30% by weight or more, and the surface of the polymer-coated magnetic bead is composed of the polymer.   The polymer-coated magnetic beads according to claim 1, wherein the hydrophobic polymer is a polymer formed by soap-free polymerization of a styrene monomer and a glycidyl methacrylate monomer.   3. The polymer-coated magnetic beads according to claim 1, wherein the saturated fatty acid is stearic acid. Modifying the surface of the ferrite nanoparticles with saturated fatty acid to obtain hydrophobized ferrite nanoparticles;
Adding the hydrophobized ferrite nanoparticles to a hydrophobic monomer liquid and dispersing to obtain a ferrite nanoparticle dispersed monomer liquid;
Adding the ferrite nanoparticle-dispersed monomer liquid to water containing a hydrophilic initiator to obtain an emulsion; and
A method for producing polymer-coated magnetic beads, comprising: a polymerization step of polymerizing monomers of the emulsion to form a polymer.   The method for producing polymer-coated magnetic beads according to claim 4, wherein the hydrophobic monomer liquid is a monomer liquid obtained by adding a glycidyl methacrylate monomer liquid to a styrene monomer liquid.   6. The method for producing polymer-coated magnetic beads according to claim 4, wherein the saturated fatty acid is stearic acid.