JPH0782302A - Magnetic particles coated with ferrite and protected with polymer coating, and preparation thereof - Google Patents

Abstract

PURPOSE:To produce a material highly suited for medical and other fields by protecting, by polymer coating, the surfaces of resin core particles coated with fine ferrite particles to improve the stability and, in particular the resistance to acid, of the magnetic particles. CONSTITUTION:The magnetic particles are resin core particles coated with fine ferrite particles, which are protected with a polymer of radical- polymerizable unsaturated monomers which may contain a glycidyl group, where the ferrite-coated resin particles are further coated with the polymer of the monomers polymerized over the particle surfaces with the aid of a double salt of a cationic surfactant and a polymerization initiator.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a medical diagnostic agent capable of controlling movement in a living body, a drug delivery system for moving a drug to a diseased part of a patient, separation / purification of a biological substance, an antigen-antibody reaction and the like. It relates to ferrite-coated magnetic particles protectively coated with the polymer used.

[0002]

2. Description of the Related Art Heretofore, various spherical resins have been proposed as carriers for pharmaceutical substances, biopolymers such as enzymes and catalysts. Since this type of resin is made of an organic polymer, it has problems in heat resistance, organic solvent resistance, mechanical strength, and the like. As a method for compensating for the above-mentioned drawbacks, JP-A-5-31080
Japanese Unexamined Patent Publication No. 8 discloses a method of coating the surface of inorganic fine particles such as silica, alumina and zirconia with an epoxy group-containing polymer. The particles not only have excellent heat resistance, organic solvent resistance, mechanical strength, etc., but also have a reactive epoxy group on the surface, so that, for example, a biopolymer such as an enzyme or an antigen or an antibody can be directly bonded. It has the feature that

However, the particle size of the above particles is 1 μm.
Since it is as large as ~ 1 cm, the floating property is poor, the reaction efficiency is low, and since the surface area of the particles is small, the binding amount of the antigen or antibody is limited and the measurement sensitivity is expected to be poor. Also,
Centrifugation must be used to separate the reaction product and unreacted product (B / F separation), or filtration with a filter must be performed, which is difficult to handle.

On the other hand, a method in which ferrite particles are coated on the surface of acrylic resin or styrene-acrylic resin particles as a core is described in JP-A-3-1155862. The particle size of this particle is 0.1-0.3 μm
Since it is fine, the amount of antigen or antibody bound can be increased. Further, since the amount of ferrite fine particles to be coated can be arbitrarily controlled, the specific gravity of the whole particles can be reduced, and the floating property is better than that of the ferrite particles alone,
High reaction efficiency with antigen or antibody. Further, since B / F separation can be performed by utilizing the magnetic characteristic, it contributes to shortening of measurement time and improvement of accuracy.

[0005]

However, the above-mentioned ferrite-coated particles have poor acid resistance, and the Fe-coated particles under acidic conditions cannot be used.
There are drawbacks such as the elution of ions and the easy release of ferrite fine particles from the polymer core particles. Therefore, there have been problems that the sensitivity as particles for medical diagnosis is lowered and that the antigens or antibodies that can be sensitized are limited. In addition, when binding an antigen or an antibody to the surface of a particle, it is necessary to treat with a silane coupling agent or the like to introduce a reactive group, which has a drawback of complicating the process.

[0006]

In the present invention, in order to protect the ferrite particles on the surface of the resin core particles, a radical polymerizable unsaturated is prepared by an initiator deposition polymerization method using a cationic surfactant and a polymerization initiator. It was possible to reduce Fe ion elution by polymerizing the monomers on the surface of the ferrite coated particles and protective coating with the polymer. Further, a polymer layer having a glycidyl group introduced therein can be directly bound to an antibody or an antigen.

That is, the ferrite-coated magnetic particles protectively coated with the polymer of the present invention are the ferrite-coated particles obtained by coating the resin core particles with the ferrite fine particles, and further via the double salt of the cationic surfactant and the polymerization initiator. And is coated with a polymer of a radically polymerizable unsaturated monomer.

The ferrite-coated magnetic particles protectively coated with such a polymer are manufactured by sequentially performing the following steps (1) to (4). (1) A step of coating resin core particles with ferrite fine particles (2) A step of mixing the ferrite coated particles with a cationic surfactant in a medium to form an adsorption layer (3) A radically polymerizable unsaturated monomer and / Alternatively, a radically polymerizable unsaturated monomer having a glycidyl group and a polymerization initiator are added in any order, and a double salt of a cationic surfactant and a polymerization initiator is formed on the surface of the ferrite-coated particles in the adsorption layer to form a radical. Step of solubilizing the polymerizable unsaturated monomer (4) Step of polymerizing the monomer to protect and coat the ferrite-coated particles.

The resin core particles used in the first step are polystyrene, poly (meth) acrylate, n-butyl poly (meth) acrylate, etc., and have a particle size of 30 to 800.
Particles with a particle size of nm are used, and the shape may be spherical or modified. The core particles may be used as they are, for example, plasma treatment, alkali treatment, resin core particles,
Acid treatment or physical treatment may be performed. By performing these treatments, the wettability with respect to the aqueous solution is improved, and more uniform coating with the ferrite fine particles can be performed.

To coat the core particles with ferrite fine particles, Japanese Patent Laid-Open No. 237019/1993 and 11586/1993.
No. 2 method, the core particles are dispersed in water or an aqueous solution, the pH of this solution is set to 6 to 11, and an aqueous ferrous ion solution and an aqueous oxidizer solution such as nitrite or hydrogen peroxide are used. In the pH-redox potential diagram shown in FIG. 1, the relationship between pH and redox potential is A (6, -440 mV), B (6, -1).
30 mV), C (11, -430 mV) and D (11, -7)
40 mV), and the feed rate ratio of the oxidant aqueous solution and the ferrous ion aqueous solution is 0.1.
~ 15 x 10 ^-3 . As a result, ferrite-coated particles in which the particle size of the ferrite particles is 4 to 50 nm and the particle size ratio of the core particles to the ferrite particles is 8/1 to 80/1 are obtained.

As the ferrous ion, ferric chloride,
Sulfate, acetate, etc. are used. In the case of containing only ferrous ions, magnetite (Fe ₃ O ₄ ) particles are formed and other metal ions such as Mn, Ni, Zn, Co,
In the case of containing a metal oxide of Cu, Mg, Sn, Ca and / or Cd, mixed crystal ferrite particles are formed.

The ferrite-coated particle suspension obtained as described above can be freeze-dried and stored as dry particles.

The cationic surfactant used in the second step is a compound in which a long-chain alkyl group is substituted with a quaternary ammonium group, for example, an aliphatic quaternary ammonium salt of the formula (I) below, (II) benzalkonium salt,
Mention may be made of pyridinium salts of formula (III), imidazolinium salts of formula (IV), ammonium salts of formula (V).

[0014]

[Chemical 1]

(Wherein R represents a C _{8 to} C ₁₈ straight-chain alkyl group, R ¹ represents a C _{1 to} C ₄ lower alkyl group, and X represents
Represents a chlorine or bromine atom) Preferred are aliphatic quaternary ammonium salts, such as octyl-, decyl-, lauryl-, myristyl-, cetyl-, or stearyl-trimethylammonium bromide.

As the medium, water, methanol, acetone, N, N-dimethylformamide, tetrahydrofuran, ethyl acetate, chloroform, benzene and the like can be used, but ion-exchanged water is preferable. The amount of the medium added is 10 to 2,000 relative to the volume of the ferrite-coated particles.
Times, preferably 50 to 1,000 times.

Various methods can be used to add the ferrite-coated particles and the cationic surfactant to the medium and mix them to form an adsorption layer. Preferably, ultrasonic waves are applied and then a shaker is used. It is advisable to adopt the method of shaking at.

The function of the cationic surfactant is not only to uniformly disperse the ferrite-coated particles in the medium but also to form an adsorption layer of the cationic surfactant on the negatively charged surface of the ferrite-coated particles, In the third step, a sparingly soluble double salt with a polymerization initiator is formed in the adsorption layer on the surface of the ferrite-coated particles to solubilize the radically polymerizable unsaturated monomer.

The polymerization initiator used in the third step is a compound having a polymerization initiation ability to form a double salt with the above-mentioned cationic surfactant, such as an alkali metal or ammonium persulfate or bisulfite, Examples include sulfite. Persulfate is preferred. Such a polymerization initiator reacts with a cationic surfactant to give, for example, di (cetyltrimethylammonium persulfate) [C ₁₆ H ₃₃ N ⁺
A double salt such as (CH ₃ ) ₃ ] ₂ S ₂ O ₈ is formed in the adsorption layer on the surface of the ferrite-coated particles, and plays a role of a polymerization initiator of the radically polymerizable unsaturated monomer.

Radical-polymerizable unsaturated monomers for forming the protective coating include aromatic vinyl compounds such as styrene, α-methylstyrene, chloromethylstyrene and divinylbenzene; vinyl acetate, vinyl chloride, divinyl ether, N. Vinyl compounds such as vinylpyrrolidone; acrylonitrile; (meth) acrylic acid, (meth)
(Meth) acrylic acid ester such as methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hydroxyethyl (meth) acrylate, ethylene glycol dimethacrylate; (meth) acrylamide, N, N-dimethyl (Meth) acrylamide compounds such as acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, n-butyl (meth) acrylamide, n-octyl (meth) acrylamide; like butadiene, isoprene, chloroprene Examples thereof include diene compounds having a conjugated double bond, and homopolymers or copolymers can be formed using these homopolymers or two or more thereof. A hydrophobic monomer such as styrene is preferable, and it becomes inferior as the hydrophilicity increases.

As the radically polymerizable unsaturated monomer having a glycidyl group, a vinyl compound having a glycidyl group such as glycidyl (meth) acrylate may be mentioned. When the vinyl-based compound having a glycidyl group is included, the glycidyl group is exposed on the surface of the polymer protective coating, so that, for example, an antigen or an antibody can be easily bound to the glycidyl group. A polymerization inhibitor such as cuperone (ammonium N-nitrosophenylhydroxylamine) may be added in order to prevent the latex from being produced during the formation of the polymer protective coating. The above-mentioned polymerization inhibitor is preferably added in an amount of 0.05 to 50% by weight, preferably 0.1 to 10% by weight, based on the radically polymerizable unsaturated monomer having a glycidyl group.

The molar ratio of the polymerization initiator to the cationic surfactant is 1: 0.5 or more, preferably 1: 2-10.
When the amount of the polymerization initiator is less than 0.5 mol, the formation of double salts of both of them on the surface of the ferrite-coated particles is reduced.

The amount of radically polymerizable unsaturated monomer added to the ferrite-coated particles is 0.05 to 1,000 wt.
%, Preferably 0.1 to 500 wt%. If the amount of the monomer is less than 0.05 wt%, a portion of the ferrite-coated particle surface where the monomer cannot be solubilized in the adsorption layer is generated, and if the amount exceeds 1,000 wt%, the particles are likely to aggregate during the polymerization.

The amount of the polymerization initiator added to the radically polymerizable unsaturated monomer is 0.01 to 20% by weight, preferably 1 to 10% by weight. If the amount of the polymerization initiator is less than 0.01 wt%, unreacted monomers that do not polymerize are generated, and
When it exceeds, the polymer is less likely to be deposited, so that the polymer coating amount is reduced.

In the third step, in order to solubilize the monomer in the adsorption layer and form the double salt of the cationic surfactant and the polymerization initiator on the surface of the ferrite-coated particles, JP-A-61-247763 is disclosed. JP-A-2-48038
It is possible to apply the initiator deposition polymerization method as described in Japanese Patent Publication No. JP-A No. 1993-331, to a suspension of a cationic surfactant on the ferrite-coated particles in the medium through the second step,
(1) First, the radical polymerizable unsaturated monomer is added, and then the polymerization initiator is added, or (2) the polymerization initiator is added, and then the radical polymerizable unsaturated monomer is added, whereby the ferrite coated particle surface A layer in which the monomer is solubilized is formed in the adsorption layer of.

Then, in the fourth step, the solubilized monomer is polymerized to uniformly coat the surface of the ferrite-coated particles with the polymer thus formed.
The polymerization reaction temperature can be appropriately selected, but is preferably 30 to 9
It is preferably carried out at 0 ° C., more preferably 50 to 70 ° C. under a nitrogen atmosphere with stirring.

After the completion of the polymerization reaction, the particles in the medium are separated by a method such as centrifugation, the precipitate is separated by filtration, washed with methanol or the like, and vacuum dried to obtain ferrite-coated particles protected by the target polymer. To get

[0028]

EFFECTS OF THE INVENTION According to the present invention, the surface of ferrite-coated particles is uniformly protectively coated with a polymer, so that elution of ferrite can be suppressed under acidic conditions. In addition, when the polymer having a glycidyl group is protectively coated, the antigen or the antibody can be directly bound to the glycidyl group, which facilitates the formation of magnetic particles as a medical diagnostic agent.

[0029]

【Example】

Example 1 50 ml of water was added with cetyl trimethyl ammonium bromide.
12 mmol and 0.1 g of the ferrite-coated magnetic particles A produced in Reference Example 1 described below were added, and the mixture was irradiated with ultrasonic waves for 1 hour and stirred, then 0.20 g of styrene was added, and the mixture was added at 25 ° C. for 2 hours.
Shake for 0 hours. Then, potassium persulfate 0.04 mmol
Was added and polymerized under a nitrogen atmosphere while shaking at 60 ° C. for 24 hours. After completion of the polymerization, the mixture was centrifuged and the precipitate was filtered off, washed with methanol, filtered and dried under vacuum. When the precipitate was dried and weighed, it was 0.174 g, and the amount of coating polymer was 0.074 g (yield 37%).

In order to confirm whether or not the ferrite fine particles were completely protective-coated with a polymer, the protective-coated particles were placed in a 0.01 M oxalic acid solution, and the resistance was examined by the change in color of the particles. The results are as shown in Table 1.
It was confirmed that the resistance index of the coated particles, which was produced by the method of JP-A-3-1155862 and was not coated with the polymer, was 1 and the resistance index of the coated particles was 30. .

Examples 2 to 16 As shown in Table 1, cetyl trimethyl ammonium bromide (CTAB) or octyl trimethyl ammonium bromide (OTAB) as a cationic surfactant,
Potassium persulfate (KPS) as a polymerization initiator and styrene (ST) as a monomer, methyl methacrylate (MM
A) and / or hydroxyethyl acrylate (HEM
A) was used to change the addition amount thereof, and the ferrite-coated particles A, B or C of Reference Examples 1, 2 or 3 described later were used, and the surface of the ferrite-coated particles was changed in the same manner as in Example 1. Coated with polymer. The resistance of the obtained ferrite particles coated with the polymer and coated with ferrite to oxalic acid was examined in the same manner as in Example 1, and the results are shown in Table 1.

Comparative Examples 1 to 3 In Comparative Example 1, the ferrite-coated particles A of Reference Example 1 were used as CTAB.
It is an example of coating with styrene resin in the absence of
The oil resistance of ST was low even if the oil droplets of ST were floating and covered. Comparative Example 2 is an example in which ferrite-coated particles A were treated with CTAB without using a polymerization initiator and coated with a styrene resin, but could not be coated. Comparative Example 3 is an example in which ferrite-coated particles A are treated with anionic surfactant sodium dodecyl sulfate (SDS) and KPS and coated with a styrene resin, but the adsorption is insufficient with the anionic surfactant. It was Resistance to these oxalic acids is also the first
Shown in the table.

[0033]

[Table 1]

[0034]

[Table 2]

As is apparent from Table 1, the ferrite-coated particles protectively coated with the polymer of the present invention are the same as Comparative Examples 1 to 1.
It can be seen that the resistance to oxalic acid is significantly higher than that of the particles of No. 3.

Example 17 Cetyltrimethylammonium bromide 0.
06 mmol and 0.1 g of the ferrite-coated magnetic particles prepared in Reference Example 2 described below were added, and after ultrasonic irradiation for 1 hour and stirring, 0.10 g of glycidyl methacrylate, 0.10 g of styrene and 0.004 g of cuperone were added. , 25
Shake at 20 ° C. for 20 hours. Then potassium persulfate 0.0
27 mmol was added, and the mixture was polymerized under a nitrogen atmosphere while shaking at 60 ° C. for 24 hours. After completion of the polymerization, the mixture was centrifuged to separate the precipitate by filtration, which was washed with water and dried under vacuum. When the precipitate was dried and weighed, it was 0.110 g, and the amount of coating polymer was 0.010 g (yield 5.2%).

The resistance to oxalic acid was investigated in order to confirm whether the fine ferrite particles were completely protectively coated with the polymer. As a result, it was confirmed that the resistance index of the coated particles was 47, which was extremely high when the resistance of the ferrite-coated particles not coated with the polymer was set to 1.

Examples 18 to 25 As shown in Table 2, as a cationic surfactant, cetyltrimethylammonium bromide (CTAB) or octyltrimethylammonium bromide (OTAB),
Using potassium persulfate (KPS) as the polymerization initiator and glycidyl methacrylate (GMA) and styrene (ST) or methyl acrylate (MMA) as the monomers, the addition amounts thereof were changed, and in Reference Example 1 or 2 below. The surface of the ferrite-coated particles was coated with a polymer in the same manner as in Example 17 except that the ferrite-coated particles A or B were used. The resistance of the obtained polymer-coated ferrite-coated particles to oxalic acid was examined in the same manner as in Example 17, and the results are shown in Table 2.

[0039]

[Table 3]

Reference Example 1 (Production of Ferrite Coated Particles A) 0.9 L of ion-exchanged water was charged into a reaction vessel, and the particle size was 30.
10 g of 0 nm polystyrene particles (Nippe Microgel E-3101 manufactured by Nippon Paint Co., Ltd.) was previously dispersed in ion-exchanged water, and 100 g was placed in the reaction vessel. The dispersion was adjusted to pH 8.0 with 0.1N NaOH and kept at 70 ° C. by heating. In this, FeCl
30wt the preparation of the ₂ · 4H ₂ O were dissolved in ion-exchanged water
% Ferrous ion aqueous solution was supplied at a supply rate of 60 ml / min, and at the same time, a 15 wt% sodium nitrite aqueous solution dissolved in ion-exchanged water was supplied at a supply rate of 0.3 ml / min.
During this time, the pH was kept constant at 8.0. Further, the feed rate ratio of the aqueous solution of sodium nitrite and the aqueous solution of ferrous ion was adjusted to 5 × 10 ⁻³ so that the redox potential of this solution was kept constant at −550 mV. The obtained ferrite-coated particles were separated by filtration and repeatedly washed with water to obtain ferrite-coated polystyrene particles. The particle size of the ferrite fine particles was 20-10 nm.

Reference Example 2 (Production of Ferrite Coated Particles B) Instead of the ferrous ion aqueous solution in Reference Example 1, F was previously prepared.
eCl ₂ · 4H ₂ O26.1g and MnCl ₂ · 4H ₂ O
13.0 g was dissolved in 60.9 g of deionized water 30
The same procedure as in Reference Example 1 was performed except that a 20 wt% aqueous solution was used and a 20 wt% hydrogen peroxide aqueous solution was used as the oxidant aqueous solution.
Mn ferrite-coated polystyrene particles were obtained. The particle size of the Mn ferrite particles was 20-10 nm.

Reference Example 3 (Production of Ferrite-Coated Particles C) Ferrite-coated polystyrene fine particles were obtained in the same manner as in Reference Example 1 except that the supply rate of the sodium nitrite aqueous solution in Reference Example 1 was 1 ml / min. It was The particle size of the ferrite fine particles was 80-70 nm.

[Brief description of drawings]

FIG. 1 is a graph showing a range of pH and redox potential at which ferrite-coated particles are suitably obtained in the first step of the present invention.

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Claims (4)

[Claims] 1. Ferrite-coated particles obtained by coating resin core particles with ferrite fine particles are coated with a polymer of a radical-polymerizable unsaturated monomer via a double salt of a cationic surfactant and a polymerization initiator. Polymer-protected ferrite-coated magnetic particles comprising: 2. The ferrite-coated magnetic particles according to claim 1, wherein the radically polymerizable unsaturated monomer contains a radically polymerizable unsaturated monomer having a glycidyl group. 3. A process for producing ferrite-coated magnetic particles protected by a polymer, which comprises sequentially performing the following steps (1) to (4). (1) Step of coating resin core particles with ferrite fine particles (2) Step of mixing the ferrite coated particles with a cationic surfactant in a medium to form an adsorption layer (3) Polymerization with radically polymerizable unsaturated monomer A step of adding an initiator in an arbitrary order to form a double salt of a cationic surfactant and a polymerization initiator in the adsorption layer on the surface of the ferrite-coated particles to solubilize the radically polymerizable unsaturated monomer (4) The step of polymerizing the monomer to protectively coat the ferrite-coated particles 4. The method for producing ferrite-coated magnetic particles according to claim 3, wherein the radical-polymerizable unsaturated monomer contains a radical-polymerizable unsaturated monomer having a glycidyl group.