Aromatic latex particles, target substance detection reagent, target substance detection kit, and method for detecting target substance

Abstract

To provide aromatic latex particles having excellent sensitivity.SOLUTION: The aromatic latex particles of the present invention satisfy an absorbance retention ratio of 91% or more in a dispersion medium, as determined by a predetermined dispersion test.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to aromatic latex particles, a target substance detection reagent, a target substance detection kit, and a target substance detection method. Regarding. [Background technology]

[0002] A latex immunoagglutination method is known as a method for measuring a target substance in a sample. The latex immunoagglutination method is a measurement method in which, for example, latex particles carrying antibodies against a target substance are used, and the degree of agglutination (turbidity) of the latex particles caused by binding of the target substance, an antigen, to the antibody-carrying latex particles is detected by optical means or the like. Known examples of this type of technology include the technology described in Patent Document 1. Patent Document 1 describes a reagent for measuring a target substance in a sample using a latex immunoagglutination method, which includes latex particles carrying an antibody that specifically recognizes the target substance in the sample (claim 7 of Patent Document 1). Furthermore, Patent Document 1 describes the use of polystyrene latex particles as latex particles (paragraph 0027 of Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-162593 Summary of the Invention [Problem to be solved by the invention]

[0004] It has been found that the polystyrene latex particles described in Patent Document 1 have room for improvement in terms of sensitivity. [Means for solving the problem]

[0005] After further investigation, the inventors found that the degree of particle sedimentation can be stably evaluated by using the change in absorbance before and after storage after ultrasonic treatment, i.e., the "absorbance maintenance rate," as an index, and that by setting such an index to a predetermined value or higher, the dispersion stability of aromatic latex particles in a dispersion medium can be increased, thereby improving the sensitivity of sensitized particles using such particles, thereby completing the present invention.

[0006] According to one aspect of the present invention, there are provided the following aromatic latex particles, target substance detection reagent, target substance detection kit, and target substance detection method. 1. Aromatic latex particles with an absorbance retention rate of 91% or more in a dispersion medium, calculated according to the dispersion test below. (Distributed Test) The aromatic latex particles are dispersed in water to a concentration of 0.2% by mass to obtain a dispersion medium. The dispersion medium is subjected to ultrasonic treatment using an ultrasonic homogenizer at a rated output of 450 W and amplitude control of 40%, with 10-second treatment repeated three times. Immediately after this, the absorbance at a wavelength of 700 nm is measured and the value is designated as A0. Next, the dispersion medium is stored in a sealed container for one week in an environment at a temperature of 4° C. After the storage is completed, the absorbance of the supernatant of the dispersion medium at a wavelength of 700 nm is measured without carrying out the ultrasonic treatment, and the value is designated as A1. Thereafter, the absorbance maintenance rate [%] is calculated from (A1 / A0)×100 using the measured A0 and A1. 2. Aromatic latex particles according to 1., The composition comprises a structural unit A having an aromatic group and a silane coupling agent having a carboxy group, Aromatic latex particles, wherein the ratio of the silane coupling agent having a carboxy group to the structural unit A is 0.1% by mass or more and 20% by mass or less, based on mass. 3. Aromatic latex particles according to 1. or 2., The compound has a structural unit A having an aromatic group and a structural unit C having a Si element, Aromatic latex particles, wherein the ratio of the structural unit C to the structural unit A is 0.01% by mass or more and 40% by mass or less on a weight basis. 4. Aromatic latex particles according to any one of 1. to 3., Aromatic latex particles having an average particle diameter of 80 nm or more and 700 nm or less. 5. Aromatic latex particles according to any one of 1. to 4., Aromatic latex particles, wherein the CV value of the average particle diameter of the aromatic latex particles is 15% or less. 6. Aromatic latex particles according to any one of 1. to 5., Aromatic latex particles, wherein the degree of sedimentation calculated from [[(A1 / A0)×100]-(A2 / A0)×100] / 7 is 5.5 or less, where A2 is the absorbance at a wavelength of 700 nm after two weeks of static storage measured in accordance with the dispersion test. 7. Aromatic latex particles according to any one of 1. to 6., Aromatic latex particles used for detecting target substances by agglutination methods. 8. A target substance detection reagent comprising the aromatic latex particles according to any one of 1. to 7. and a dispersion medium. 9. A target substance detection kit comprising a reagent container containing the target substance detection reagent described in 8. 10. A method for detecting a target substance, comprising the step of mixing a target substance with the target substance detection reagent described in 8. [Effects of the Invention]

[0007] According to the present invention, aromatic latex particles with excellent sensitivity, a target substance detection reagent, a target substance detection kit, and a target substance detection method are provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating an example of the configuration of a sensitized particle according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by similar reference numerals, and descriptions thereof will be omitted where appropriate. Furthermore, the drawings are schematic diagrams and do not correspond to actual dimensional proportions.

[0010] The aromatic latex particles of this embodiment will be outlined below.

[0011] The aromatic latex particles of the present embodiment satisfy an absorbance retention rate in a dispersion medium of 91% or more, calculated according to the following dispersion test. (Distributed Test) Aromatic latex particles are dispersed in water to a concentration of 0.2% by mass to obtain a dispersion medium. The dispersion medium is subjected to ultrasonic treatment using an ultrasonic homogenizer at a rated output of 450 W and amplitude control of 40%, with 10-second treatment repeated three times. Immediately after this, the absorbance at a wavelength of 700 nm is measured and the value is designated as A0. Next, the dispersion medium is stored in a sealed container at 4° C. for one week. After storage, the supernatant of the dispersion medium is measured for absorbance at a wavelength of 700 nm without ultrasonic treatment, and the value is designated as A1. Thereafter, the absorbance maintenance rate [%] is calculated from the measured values ​​A0 and A1 by (A1 / A0)×100.

[0012] According to the findings of the present inventors, it has been found that by appropriately adjusting the type and blending ratio of the dispersant used in the production of aromatic latex particles, it is possible to control the degree of sedimentation of particles in a dispersion medium and improve dispersion stability. Furthermore, as a result of intensive research based on this finding, it was found that the degree of particle settling can be stably evaluated by using the change in absorbance before and after storage after ultrasonic treatment, i.e., the above-mentioned "absorbance maintenance rate," as an index, and that by setting this index to be equal to or greater than the above-mentioned lower limit, the dispersion stability of aromatic latex particles in a dispersion medium can be increased, and the sensitivity of sensitized particles using such particles can be improved. Furthermore, when measurements are made at a wavelength close to the particle size of aromatic latex particles, the difference in absorbance before and after aggregation generally tends to be small. However, according to the present embodiment, even in such a case, the decrease in sensitivity can be suppressed.

[0013] In this embodiment, the absorbance retention rate can be controlled by appropriately selecting, for example, the type and amount of each component contained in the aromatic latex particles, the method for preparing the aromatic latex particles, etc. Among these, factors for setting the absorbance retention rate within a desired range include appropriately selecting the type and blending ratio of the dispersant used in the production of the aromatic latex particles, and using a crosslinking agent if necessary.

[0014] Although the detailed mechanism is not clear, it is presumed that the aromatic latex particles become less likely to settle, that is, the sedimentation suppression ability can be improved, by making the average particle size and standard deviation relatively small and by appropriately controlling the surface condition of the particles.

[0015] The shape of the aromatic latex particles is not particularly limited, and examples thereof include spherical, elliptical, etc. Among these, the aromatic latex particles are preferably spherical, and more preferably true spherical.

[0016] In the present embodiment, the lower limit of the absorbance retention rate is 91% or more, preferably 92% or more, and more preferably 93% or more. By using such aromatic latex particles, a dispersion of sensitized particles with excellent sensitivity can be realized. On the other hand, the upper limit of the absorbance maintenance rate is not particularly limited, but may be 100% or less.

[0017] In the dispersion test, when the static storage conditions are changed from one week to two weeks, the absorbance at a wavelength of 700 nm after two weeks of static storage is defined as A2. In this case, the lower limit of (A2 / A0) × 100 is, for example, 60% or more, preferably 63% or more, and more preferably 65% ​​or more, which can relatively prolong the dispersion stability of the aromatic latex particles in the dispersion medium. On the other hand, the upper limit of (A2 / A0)×100 is not particularly limited, but may be 100% or less.

[0018] The lower limit of A2 is, for example, 0.5 or more, preferably 0.6 or more, and more preferably 0.7 or more, which can relatively prolong the dispersion stability of the aromatic latex particles in the dispersion medium. The upper limit of A2 is not particularly limited, but may be 3.0 or less.

[0019] The daily sedimentation rate is defined as [[(A1 / A0) × 100] - (A2 / A0) × 100] / 7. In this case, the upper limit of the sedimentation degree is, for example, 5.5 or less, preferably 5.3 or less, and more preferably 5.1 or less, which can relatively prolong the dispersion stability of the aromatic latex particles in the dispersion medium. The lower limit of the degree of sedimentation is not particularly limited, but may be set to 0.0001 or more.

[0020] The upper limit of the average particle size of the particle group of aromatic latex particles is, for example, 700 nm or less, preferably 650 nm or less, and more preferably 600 nm or less. On the other hand, the lower limit of the average particle size is, for example, 80 nm or more, preferably 90 nm or more, and more preferably 100 nm or more.

[0021] In this embodiment, a dispersion (aqueous dispersion) containing aromatic latex particles is dried, the resulting powder is fixed to a sample stage, and the surface of the powder (sample) is coated by metal vapor deposition to prepare a sample. The obtained sample is observed using a scanning electron microscope, and the diameters of 30 or more particles observed in the image are measured. The average value of the measured diameters is calculated as the average particle size.

[0022] The CV (Coefficient of Variation) value of the average particle size is calculated from [standard deviation / average particle size]×100, and the lower the value, the higher the monodispersity index. The upper limit of the CV value of the particle group of aromatic latex particles is, for example, 15% or less, preferably 10% or less, and more preferably 5% or less. On the other hand, the lower limit of the CV value is not particularly limited, but may be 0.01% or more.

[0023] The aromatic latex particles may also include a silane coupling agent having a carboxy group. In this case, the content of the silane coupling agent having a carboxy group relative to the structural unit A having an aromatic group is, in mass terms, for example, 0.1 mass% to 20 mass%, preferably 0.3 mass% to 17.5 mass%, and more preferably 0.5 mass% to 15 mass%. In this specification, unless otherwise specified, the symbol "to" indicates that the upper and lower limits are included.

[0024] The aromatic latex particles may comprise a structural unit A having an aromatic group and a structural unit B having an ionic group. In this case, the ratio of the structural unit B to the structural unit A is, for example, 0.01% to 15%, preferably 0.03% to 12.5%, and more preferably 0.05% to 10%, on a molar basis. The ionic group refers to a sulfonic acid group and / or a carboxy group.

[0025] The aromatic latex particles may have a structural unit A having an aromatic group and a structural unit C having a Si element. In this case, the ratio of the structural unit C to the structural unit A is, for example, 0.01% by mass to 40% by mass, preferably 0.03% by mass to 30% by mass, and more preferably 0.05% by mass to 20% by mass, based on mass.

[0026] The aromatic latex particles may include, in addition to the structural unit A having an aromatic group, a structural unit B having an ionic group, a structural unit C having an Si element, and a silane coupling agent having a polycarboxy group.

[0027] The method for producing aromatic latex particles is not particularly limited, but examples thereof include a method in which one or more raw material components are polymerized using a polymerization initiator (such as a radical polymerization initiator) to form a granular organic polymer in a solvent (such as water). When forming the granular organic polymer, a crosslinked structure may be formed by a coupling reaction, if necessary. The method for forming the granular organic polymer may be a radical polymerization method such as emulsion polymerization, soap-free emulsion polymerization, or suspension polymerization, but is not limited to radical polymerization.

[0028] Examples of raw material components include main skeleton monomers (monofunctional polymerizable compounds having aromatic groups, polyfunctional polymerizable compounds having aromatic groups), polymerizable silane coupling agents, dispersants, crosslinking agents, etc. These may be used alone or in combination of two or more. When the raw material components include a main skeleton monomer having an aromatic group, a polymerizable silane coupling agent, and a dispersant, each of these components preferably has a polymerizable functional group, more preferably has a functional group having an unsaturated double bond capable of radical polymerization.In addition, when the raw material components further include a crosslinking agent, the polymerizable silane coupling agent preferably has a hydrolyzable silyl group, and the crosslinking agent preferably has two or more functional groups in the molecule that react with the hydrolyzable silyl group. The main skeleton monomer, or the polymerizable compound, may be a monomer or a polymer such as an oligomer or a prepolymer.

[0029] Examples of monofunctional polymerizable compounds having an aromatic group include vinyl compounds such as styrene-based monomers, α-methylstyrene, and chlorostyrene; naphthalene compounds such as 1-vinylnaphthalene and 2-vinylnaphthalene; anthracenyl compounds such as 2-vinylanthracene and 9-vinylanthracene; phenanthrene compounds such as 3-vinylphenanthrene and 9-vinylphenanthrene; dinaphthothiophene compounds such as 6-vinyldinaphthothiophene and 6-vinyletherdinaphthothiophene; carbazole compounds such as 9-vinylcarbazole; and (meth)acrylic compounds such as aromatic (meth)acrylate compounds, such as benzyl (meth)acrylate; and polycyclic aromatic (meth)acrylate compounds, such as 2-(1-naphthyl)methyl (meth)acrylate, phenantyl (meth)acrylate, 6-(meth)acryloyloxymethyldinaphthothiophene, and 6-(meth)acryloyloxyethyldinaphthothiophene.

[0030] Examples of polyfunctional polymerizable compounds having an aromatic group include vinyl compounds such as divinylbenzene, 2,12-divinyldinaphthothiophene, 3,11-divinyldinaphthothiophene, 5,9-divinyldinaphthothiophene, 2,12-divinyloxymethyldinaphthothiophene, 3,11-divinyloxydinaphthothiophene, 1,4-divinyloxybutane, and divinyl sulfone; and (meth)acrylic compounds such as 2,12-di(meth)acrylonitrile, ... Examples of the acryloyloxymethyl dinaphthothiophene include 3,11-di(meth)acryloyloxymethyl dinaphthothiophene, 9,9-bis(4-(meth)acryloyloxyphenyl)fluorene, 9,9-bis(4-(meth)acryloyloxymethoxyphenyl)fluorene, and 9,9-bis(4-(2-(meth)acryloyloxyethoxy)phenyl)fluorene; and examples of allyl compounds include 9,9'-bis(4-allyloxyphenyl)fluorene.

[0031] As the polymerizable silane coupling agent, a silane coupling agent having a polymerizable functional group and a hydrolyzable silyl group can be used, and examples thereof include 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltriethoxysilane, and 3-acryloxypropyltrimethoxysilane, which enables orientation control.

[0032] As the dispersant, a dispersant having a polymerizable group can be used, but an anionic dispersant is preferred. Examples of anionic dispersants having a polymerizable group include sodium methacrylate, sodium parastyrene, etc. These may be contained alone or in any combination of two or more.

[0033] As the crosslinking agent, a compound having two or more functional groups in the molecule that react with the hydrolyzable silyl group in the polymerizable silane coupling agent can be used, for example, a silane coupling agent having a carboxylic acid group. The functional group that reacts with the hydrolyzable silyl group is not limited to a carboxylic acid group (carboxyl group), but may include a hydroxyl group, an amino group, a thiol group, etc. These may be used alone or in combination of two or more. The crosslinking mechanism of the crosslinking agent is thought to be that a polymerizable silane coupling agent such as 3-methacryloxypropyltrimethoxysilane undergoes radical polymerization with a polymerizable group contained in a monofunctional polymerizable compound having an aromatic group such as styrene or a dispersant such as sodium methacrylate, is incorporated into the main skeleton, and the alkoxysilyl group in the side chain undergoes a coupling reaction with a crosslinking agent such as a silane coupling agent having a carboxylic acid group.

[0034] The aromatic latex particles of this embodiment can be used in various applications where latex particles are used, for example, for detecting a target substance by an agglutination method. The aromatic latex particles can be used as core particles (particles that serve as the core of sensitized particles) that constitute sensitized particles used in the agglutination method. The aromatic latex particles may also be used as, for example, a dispersant, a filler, or the like.

[0035] A specific example in which aromatic latex particles are used in the aggregation method will be described below. FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a sensitized particle 20. As shown in FIG. An example of the sensitized particle 20 has a core particle 1, and a ligand 3 and a blocking protein 5 immobilized on at least a portion of the surface of the core particle 1. As such a core particle 1, the aromatic latex particle of this embodiment is used.

[0036] The agglutination method is a method in which a sample containing a target substance (e.g., an antigen) is contacted in a dispersion medium with sensitized particles 20 carrying a ligand 3 (e.g., an antibody) that specifically recognizes (binds to) the target substance, and the ligand 3 binds to the target substance, forming a complex between the target substance, the ligand 3, and the sensitized particles 20, thereby selectively agglutinating the sensitized particles 20. The immunoagglutination method (also called immunoturbidimetry), which is one of the agglutination methods, utilizes an antigen-antibody reaction to cause an antigen to react with an antibody provided on the surface of the sensitized particles 20, thereby agglutinating the sensitized particles 20. In a method for detecting a target substance using the agglutination method, the degree of agglutination of the sensitized particles 20 can be characterized and quantified by optical measurement methods such as absorbance, scattered light intensity, and transmitted light intensity.

[0037] According to this embodiment, the dispersibility of the sensitized particles 20 in the dispersion medium can be increased, which prevents the sensitized particles 20 from aggregating with each other in the dispersion medium before reacting with the target substance, i.e., prevents a nonspecific reaction.

[0038] Furthermore, according to this embodiment, the dispersibility of the sensitized particles 20 can be improved, thereby increasing the change in the degree of aggregation of the sensitized particles 20 before and after reacting with the target substance. In other words, when comparing the presence and absence of the target substance, the difference in optical measurement values ​​such as absorbance in a dispersion medium containing the sensitized particles 20 increases, making it possible to improve the sensitivity of the sensitized particles 20, i.e., the detection sensitivity of the target substance.

[0039] An example of the target substance detection reagent of this embodiment includes the particle group of the sensitized particles 20 and a dispersion medium. The concentration (wt %) of the sensitized particles 20 in the dispersion medium can be set appropriately. As the dispersion medium, for example, the above-mentioned aqueous solvents are preferably used. The aqueous solvent may contain, within the scope that does not impair the effects of the invention, a third substance such as a buffering agent, a preservative (such as sodium azide), a blocking agent such as a protein (albumin), a sensitizer such as a water-soluble polymer (such as a sugar, polyethylene glycol, or dextran), a salt (such as sodium chloride or an amino acid), or a surfactant. These may be used alone or in combination of two or more.

[0040] Examples of the sensitizer include polyethylene glycol, dextran, and a sensitizer having a phosphorylcholine group. Preferably, the sensitizer may include a sensitizer having a phosphorylcholine group. This can further improve the dispersibility of the sensitized particles 20.

[0041] Examples of sensitizers having a phosphorylcholine group include polymers having a phosphorylcholine group. These may be used alone or in combination of two or more. The polymer having a phosphorylcholine group has at least one or two or more structural units M having a phosphorylcholine group in the side chain of the polymer. The phosphorylcholine group may be partially modified as long as it can be used as a polar group of phospholipids, which are components of biological membranes. The polymer having a phosphorylcholine group may be a homopolymer having only the structural unit M, or may be a copolymer having the structural unit M and another structural unit N. The structural unit N may be a structural unit having, for example, any one of a hydrophobic group, an anionic group, a cationic group, and a hydrogen-bonding group on the side chain of the polymer. The main chain of the polymer having a phosphorylcholine group may have a structure in which polymerizable groups in the raw material monomers such as 2-methacryloyloxyethyl phosphorylcholine (MPC) are linked to each other.

[0042] The target substance detection reagent of this embodiment can also be in the form of a kit from the viewpoint of storage, transportation, distribution, etc. The form of the kit is not particularly limited as long as it is a form that enables the measurement method of the present invention. An example of the target substance detection kit of this embodiment includes a reagent container containing the above-described target substance detection reagent.

[0043] The kit can take various forms, such as the following: The kit of the first type comprises a first reagent container containing a particle group of sensitized particles 20 and a dispersion medium. The kit of the second embodiment includes a second reagent container A containing a particle group of sensitized particles 20, and a second reagent container B containing a dispersion medium. The first reagent container of the kit of the first form and the second reagent containers A and B of the kit of the second form may each contain at least one or more of the third substances exemplified above. Furthermore, each of the kits of the first and second forms may further include a third reagent container containing at least one of the third substances. Furthermore, each of the kits of the first and second forms may include, in addition to the above-mentioned reagent container, a fourth reagent container containing one or more of a positive control, a negative control, a diluent, a washing solution, instructions for use, etc. As the media for the positive and negative controls, serum, physiological saline, solvents, etc. that do not contain the target substance to be measured are used.

[0044] An example of the method for detecting a target substance according to this embodiment includes a contact step of mixing a target substance with a target substance detection reagent. In the contact step, a sample containing a target substance and sensitized particles 20 having ligands 3 are added to the same reaction vessel and allowed to coexist, allowing the ligands 3 bound to the sensitized particles 20 to come into contact with the target substance. The sample containing the standard substance and the target substance reagent containing the sensitized particles 20 may be added in any order. Furthermore, the target substance and the sensitized particles 20 may be mixed at a pH of about 3.0 or more and about 11.0 or less, and the temperature of the mixture may be about 20°C or more and about 50°C or less.

[0045] The target substance is brought into contact with the ligand 3 and reacted with each other, and the substance to be measured in the sample reacts with the antibody carried by the core particle, forming a complex between the target substance, the ligand 3, and the sensitized particle 20, causing the sensitized particle 20 to aggregate as a result of the complex formation.

[0046] The method for detecting a target substance may include, after the contact step, a detection step of optically measuring the agglutination of the sensitized particles 20. Examples of the method for optically measuring agglutination include a method of measuring absorbance, scattered light intensity, or transmitted light intensity with an optical device. The wavelength for measuring absorbance is usually 340 nm to 1000 nm, preferably 500 nm to 900 nm. The time for measuring an agglutination reaction can be measured by measuring the rate of change per unit time or the amount of change per unit time. For example, when measuring absorbance, the rate of change per unit time from 30 seconds to 5 minutes after the start of the agglutination reaction can be measured by measuring the amount of change in absorbance per unit time or the amount of change in absorbance per unit time.

[0047] The sample is not particularly limited as long as it has the potential to contain the target substance, and examples thereof include one or more biological samples selected from the group consisting of whole blood, plasma, serum, urine, cerebrospinal fluid, saliva, amniotic fluid, urine, sweat, and pancreatic juice. The sample is preferably whole blood, plasma, serum, or urine. The sample may be an aqueous solvent containing the target substance, for example, the target substance diluted with phosphate buffered saline or the like.

[0048] The aqueous solvent is not particularly limited as long as it allows the aggregation method, and examples thereof include deionized water, distilled water, buffer solutions, etc., with buffer solutions being preferred. Examples of buffering agents contained in buffer solutions include phosphate-based, acetate-based, Tris-based, borate-based, carbonate-based, glycine-based, and Gut-based buffer solutions. Suitable Good's buffers include, for example, HEPES, PIPES, and MOPS. The buffering agent may be used alone or in combination of two or more kinds. Acids that can be used to adjust the pH of a buffer solution containing a buffer component include ordinary hydrochloric acid, sulfuric acid, nitric acid, and organic acids such as acetic acid. Alkalis that can be used include sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonium hydroxide.

[0049] The target substance is not particularly limited as long as it is a target substance that allows for the agglutination method, and examples thereof include CRP (C-reactive protein); prostate-specific antigen (PSA); ferritin; α2-macroglobulin; β2-microglobulin; myoglobin; fibrin; fibrinogen degradation products; D-dimer; thrombin-antithrombin III complex (TAT); soluble fibrin (SF); soluble interleukin-2 receptor (sIL-2R); and sodium-reducing peptides such as atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). Examples include urinary peptides; N-terminal pro-brain natriuretic peptide (NT-proBNP); antistreptolysin O; rheumatoid factor; transferrin; haptoglobin; α1-antitrypsin; α1-acidoglycoprotein; hemopexin; antithrombin-III; α-fetoprotein; CEA (carcinoembrionic antigen); HBs-Ag (hepatitis B envelope antigen); Anti-HBs (anti-hepatitis B envelope antibody); HBe-Ag (hepatitis B e antigen); Anti-HBe (anti-hepatitis B e antibody); Anti-HBc (anti-hepatitis B core antibody); IgG; IgA; IgM, etc. The target substance is not particularly limited as long as it is in a form that allows it to bind to an antibody, and may be, for example, in a free form as a simple substance, or in a complex form with another substance (for example, a protein, etc.).

[0050] Here, a specific example of the sensitized particles 20 of this embodiment will be described.

[0051] An example of the sensitized particle 20 of this embodiment may have a core particle 1 having a plurality of reactive functional groups (A1) on its surface, a ligand 3 chemically bonded to a portion of the reactive functional groups (A1), and a blocking protein 5 chemically bonded to another portion of the reactive functional groups (A1).

[0052] When the core particle 1 has a reactive functional group (A1) on its surface, the ligand 3 can be chemically bound to the surface of the core particle 1 via the reactive functional group (A1). Furthermore, when the core particle 1 has a reactive functional group (A1) on its surface, the blocking protein 5 can be chemically bound to the surface of the core particle 1 via the reactive functional group (A1).

[0053] The reactive functional group (A1) may contain one or more groups selected from the group consisting of nucleophilic groups such as carboxyl groups, amino groups, and thiol groups, and electrophilic groups such as epoxy groups, maleimide groups, acrylic groups, methacrylic groups, and acid anhydride groups. Examples of acid anhydride groups include maleic anhydride groups and succinic anhydride groups. Among these, the reactive functional group (A1) may contain a carboxyl group.

[0054] (ligand) Ligand 3 is a compound that specifically binds to a receptor possessed by the target substance described above. The site at which the ligand 3 binds to the target substance is fixed, and the ligand 3 has high affinity selectively or specifically. Examples of the ligand 3 include, but are not limited to, antigens and antibodies, enzyme proteins and their substrates, signal substances such as hormones and neurotransmitters and their receptors, and nucleic acids. Examples of the ligand 3 include antibodies such as full-length antibodies and antigen-binding fragments (e.g., antibody fragments such as Fab, F(ab')2, F(ab'), Fv, and scFv); antigens; nucleic acids such as naturally occurring nucleic acids and artificial nucleic acids; proteins such as aptamers, peptide aptamers, oligopeptides, enzymes, and coenzymes; etc. Commercially available antibodies can be used as the antibodies that specifically recognize the target substance.

[0055] (Blocking protein) Examples of blocking proteins 5 include animal-derived albumins such as bovine serum albumin, casein, gelatin, ovalbumin, and gamma-globulin. Among these, naturally occurring blocking proteins are preferred from the viewpoint of dispersibility, and naturally occurring blocking proteins are preferred over synthetic polymers from the viewpoint of sensitivity. These may be used alone or in combination of two or more.

[0056] Here, one example of the method for producing sensitized particles of this embodiment includes a step of obtaining sensitized particles 20 in which ligands 3 and blocking proteins 5 are fixed to at least a portion of the surface of core particles 1 by chemical bonds. Specifically, the process of obtaining such sensitized particles 20 includes a reaction treatment in which some of the reactive functional groups (A1) present on the surface of the core particle 1 are chemically bonded to the blocking protein 5. An example of this reaction treatment is to add a condensing agent that chemically bonds the other part of the reactive functional group (A1) with the blocking protein 5 and the blocking protein 5. The addition of the blocking protein 5 and the condensing agent (reaction treatment) is not particularly limited, as long as it is performed during a series of treatments including the sensitization treatment, washing treatment, and blocking treatment described below, or before or after each treatment in the series of treatments, which are carried out during the process of obtaining the sensitized particles 20. Specifically, the addition of the blocking protein 5 and the condensing agent may be performed, for example, simultaneously with the blocking treatment, before the blocking treatment, simultaneously with any of a series of treatments other than the blocking treatment, or before or after any of the series of treatments. It is preferable that the addition of the blocking protein 5 and the condensing agent includes at least one of the following: adding the condensing agent after the blocking protein 5; adding the condensing agent and then adding the blocking protein 5; or adding a mixture of the blocking protein 5 and the condensing agent. Furthermore, the number of times that the blocking protein 5 and the condensing agent may each be added may be one or more than one. When adding them multiple times, one or more of the above-mentioned treatments may be performed between additions.

[0057] As the condensing agent, those used in the immobilization method utilizing a carboxy group or an amino group, which are known as methods for immobilizing antibodies, can be used. As the condensation agent, for example, a carbodiimide-based crosslinking agent or an amine-reactive crosslinking agent is used. Carboxy groups and amino groups can be reacted using a carbodiimide crosslinking agent such as EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, also known as EDAC or WSC). Amine-reactive crosslinkers can also be used to react primary or secondary amino groups with synthetic chemical groups such as isothiocyanates, isocyanates, acyl azides, NHS esters, sulfonyl chlorides, aldehydes, glyoxals, epoxides, oxiranes, carbonates, aryl halides, imidoesters, carbodiimides, anhydrides, and fluoroesters.

[0058] In the above-mentioned sensitization treatment, the ligand 3 can be chemically reacted with at least a part of the surface of the core particle 1 . Sensitization treatment for binding (carrying) ligand 3 to core particle 1 can be performed, for example, by suspending ligand 3 (antibody) and core particle 1 in a solvent such as a buffer solution and reacting them at approximately 20 to 37°C for a predetermined period of time.

[0059] The buffer solution may have a pH of, for example, 5.0 to 10.0. The buffer solution may contain, for example, an aqueous solvent, a buffering agent, a preservative (such as sodium azide), a blocking agent such as a protein (albumin), a sensitizer such as a water-soluble polymer (such as a sugar, polyethylene glycol, or dextran), a salt (such as sodium chloride or an amino acid), a surfactant, etc. These may be used alone or in combination of two or more.

[0060] In the sensitization treatment, a conventionally known method can be used as a chemical reaction method for chemically immobilizing the reactive functional group (A1) present on the surface of the core particle 1 and the ligand 3. Examples of chemical reaction methods that can be used include, but are not limited to, a carbodiimide-mediated reaction and an NHS ester activation reaction. If necessary, the above-mentioned condensing agent may also be used.

[0061] The process for obtaining the sensitized particles 20 may include, in addition to the above-mentioned sensitization treatment, one or more treatments commonly used in the technical field of sensitized particles, such as a washing treatment and a blocking treatment. If necessary, other treatments such as centrifugation, ultrasonic treatment, heating (aging) treatment, etc. may be carried out at appropriate times. In the washing treatment, for example, the sensitized product obtained in the sensitization treatment can be washed by a known method. A washing solution or the like can be used for washing. The washing treatment may be carried out once or twice or more times. In the blocking treatment, another blocking protein that physically binds to the sensitized product obtained by the sensitization treatment, for example, by physical adsorption, can be added. At this time, a blocking solution containing the other blocking protein may be added.

[0062] In another embodiment, other blocking proteins may be present on at least a portion of the surface of the sensitized particle 20 and / or the surface of the blocking protein 5, by physical adsorption or the like. At least one or more of the washing solution that can be used in the washing process, the blocking solution that can be used in the blocking process, and the dispersion medium may contain other blocking proteins that physically bind by physical adsorption or the like, such as those exemplified for the above-mentioned blocking protein 5.

[0063] Furthermore, one example of the method for producing the sensitized particle dispersion of this embodiment includes a dispersing step of dispersing the obtained sensitized particles 20 in a dispersion medium. In this dispersing step, the sensitized particles 20 produced in the step of obtaining the sensitized particles 20 are dispersed in the above-mentioned dispersion medium, thereby producing a target substance detection reagent.

[0064] In another embodiment, the method may include an introduction step of introducing a surface-modifying polymer having the above-mentioned reactive functional group (A1) or a coupling agent having the above-mentioned reactive functional group (A1) onto at least a portion of the surface of the core particle. The introduction step can be performed at any timing during the process of obtaining the sensitized particles 20, but is preferably performed before the sensitization treatment or the binding treatment. As a result, the reactive functional group (A1) is formed on the surface of the core particle 1 via the surface-modifying polymer and / or the coupling agent. Sensitized particles 20 of this type may include a ligand 3 and / or a blocking protein 5 bound to at least some of the reactive functional groups (A1) of the surface-modifying polymer and / or coupling agent.

[0065] The surface-modifying polymer may be formed on at least a part of the surface of the core particle 1, and may form a polymer coating layer that covers a part or the entire surface of the core particle 1. The surface-modified polymer is physically bonded to the surface of the core particle 1, and / or a specific functional group contained in the surface-modified polymer is chemically bonded to a specific functional group present on the surface of the core particle 1.

[0066] The surface-modifying polymer may be composed of a (meth)acrylic polymer, a maleic acid polymer, a methylene malonate polymer, a phenolic resin, an epoxy resin, or the like. These may be used alone or in combination of two or more. However, the surface-modifying polymer may not include a copolymer having a unit derived from a styrene-based monomer and a unit derived from a glycidyl group-containing monomer. According to this embodiment, by using a surface-modified polymer in addition to the core particle 1, a wide variety of molecular designs become possible for the surface-modified polymer, and the degree of freedom in molecular design increases.

[0067] Examples of the (meth)acrylic polymer include methacrylic polymers and acrylic polymers. Examples of maleic acid-based polymers include maleic anhydride-norbornene copolymers, styrene-maleic anhydride copolymers, maleic anhydride homopolymers, methyl vinyl ether-maleic anhydride copolymers, and olefin-maleic anhydride copolymers.

[0068] The surface-modifying polymer may be any of a homopolymer, a random copolymer, an alternating copolymer, a block copolymer, a periodic copolymer, and the like.

[0069] The weight average molecular weight of the surface modifying polymer is, for example, 1,000 or more and 10,000,000 or less, preferably 2,000 or more and 5,000,000 or less, and more preferably 3,000 or more and 1,000,000 or less. The weight average molecular weight can be determined from a polystyrene equivalent value obtained from a calibration curve of standard polystyrene (PS) obtained by gel permeation chromatography measurement.

[0070] The surface modifying polymer may comprise a structural unit A1 that comprises a reactive functional group (A1) capable of binding to a ligand 3.

[0071] The method for forming the surface-modifying polymer on the surface of the core particle 1 uses, for example, a polymer introduction step in which a surface-modifying polymer is introduced onto the surface of the core particle 1 by a chemical reaction. For the chemical reaction, an immobilization method using a carboxy group or an immobilization method using an amino group, which are known as methods for immobilizing antibodies, can be used. These chemical reactions may involve the use of condensing agents, such as carbodiimide-based crosslinkers and amine-reactive crosslinkers, if desired. Carboxy groups and amino groups can be reacted using a carbodiimide crosslinking agent such as EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, also known as EDAC or WSC). Amine-reactive crosslinkers can also be used to react primary or secondary amino groups with synthetic chemical groups such as isothiocyanates, isocyanates, acyl azides, NHS esters, sulfonyl chlorides, aldehydes, glyoxals, epoxides, oxiranes, carbonates, aryl halides, imidoesters, carbodiimides, anhydrides, and fluoroesters.

[0072] When the core particle 1 is an organic particle (resin particle), a method is used in which a polymer reactive group (such as a carboxy group or an amino group) contained in the raw material monomer of the organic particle reacts with a predetermined reactive group contained in the surface-modifying polymer. For example, in the manufacturing process of the organic particle, it is possible to incorporate a polymer reactive group into the organic polymer during the polymerization of the raw material monomer. Commercially available polystyrene particles containing a carboxy group may also be used as the core particle 1. As a specific example, when a surface-modifying polymer containing a carboxy group is immobilized on a core particle 1 containing a carboxy group, primary amino groups (-NH2) may be introduced by amino treatment to some of the carboxy groups in the core particle 1 (amino treatment). Then, the primary amino groups (polymer reactive groups) in the core particle 1 after the amino treatment and the predetermined reactive groups in the surface-modifying polymer are chemically reacted, if necessary, by adding the above-mentioned condensing agent. When the surface-modifying polymer contains an acrylic group / methacrylic group, it is possible to react the primary amino group (polymer reactive group) with the carboxy group (predetermined reactive group) contained in the acrylic group / methacrylic group via the above-mentioned condensing agent. In another embodiment, when the surface-modifying polymer contains an anhydride group, it is possible to react a primary amino group (polymer reactive group) with an anhydride group (predetermined reactive group) such as a maleic anhydride group without using the above-mentioned condensing agent.

[0073] Here, an example of a method for synthesizing a surface-modifying polymer will be described. The raw material monomers used in the polymer precursor production process can be one or more of raw material monomer A containing a diene compound and a diene parent compound, and raw material monomer B containing a functional group and an unsaturated group such as a double bond.

[0074] For the polymer of a diene compound and a diene parent compound, (i) if an anhydride group is contained, the reactive functional group (A1), the acidic functional group (A2), or other functional groups (functional functional groups) may be introduced into the side chain by ring-opening the anhydride group; (ii) if a carboxyl group is contained, various functional groups may be introduced into the side chain by a condensation reaction or the like; and (iii) if an unsaturated group such as a double bond is contained, the various functional groups described above may be introduced into the side chain by an addition reaction or the like. Examples of the other functional groups mentioned above include known functional groups such as various reactive groups, hydrophobic groups, hydrophilic groups (water-soluble groups), and acidic groups. Furthermore, (i) when an anhydride group is contained, the anhydride group may be ring-opened with water, alcohol, etc., or may be ring-opened with an organic base. Furthermore, the functional group described above may be introduced into the side chain of the polymer precursor by a condensation reaction or the like with respect to a functional group such as a carboxyl group formed by ring-opening of the anhydride group, as in (ii) above.

[0075] For the synthesis of a polymer precursor of a maleic anhydride-based polymer, for example, a norbornene-based monomer such as norbornene can be used as the diene compound, and an unsaturated carboxylic acid anhydride having a cyclic structure in the molecule such as maleic anhydride can be used as the new diene compound.

[0076] On the other hand, the raw material monomer B may be a raw material monomer B1 having a reactive functional group (A1) and an acidic functional group (A2), or a combination of a raw material monomer B2 having a reactive functional group (A1) and a raw material monomer B2 having an acidic functional group (A2). If necessary, in addition to these, a raw material monomer B3 having a functional group other than the reactive functional group (A1) and the acidic functional group (A2) may be used.

[0077] To synthesize a polymer precursor of a (meth)acrylic polymer, for example, (meth)acrylic acid such as acrylic acid, methacrylic acid, (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, hexyl (meth)acrylate, and ethylhexyl (meth)acrylate can be used. One or more of these (meth)acrylic monomers can be used.

[0078] The polymerization may be, but is not limited to, addition polymerization and / or condensation polymerization. For example, addition polymerization may be carried out by radical polymerization. Alternatively, the reactive functional group (A1), the acidic functional group (A2), or other functional groups (functional functional groups) may be introduced into the side chains of the resulting polymer precursor by ring-opening reaction, condensation reaction, addition reaction, or the like. A specific example will be described. First, one or more raw material monomers and a polymerization initiator are dissolved in a solvent, and then the solution is heated for a predetermined period of time to carry out solution polymerization. The heating temperature can be, for example, 50°C to 80°C. The heating time can be, for example, 1 hour to 20 hours. It is more preferable to carry out solution polymerization after removing dissolved oxygen in the solvent by nitrogen bubbling.

[0079] As the polymerization initiator, for example, an azo compound, an organic peroxide, or the like can be used. Specific examples of the azo compound include azobisisobutyronitrile (AIBN), dimethyl 2,2'-azobis(2-methylpropionate), and 1,1'-azobis(cyclohexanecarbonitrile) (ABCN). Examples of organic peroxides include hydrogen peroxide, ditertiary butyl peroxide (DTBP), benzoyl peroxide (benzoyl peroxide, BPO), and methyl ethyl ketone peroxide (MEKP). As for the polymerization initiator, one type may be used alone, or two or more types may be used in combination.

[0080] Furthermore, a molecular weight modifier or a chain transfer agent can be used as needed. Examples of the chain transfer agent include thiol compounds such as dodecyl mercaptan, mercaptoethanol, and 4,4-bis(trifluoromethyl)-4-hydroxy-1-mercaptobutane. These chain transfer agents can be used alone or in combination of two or more.

[0081] Examples of solvents used in the polymerization reaction include one or more esters such as methyl ethyl ketone (MEK), propylene glycol monomethyl ether, diethyl ether, tetrahydrofuran (THF), toluene, ethyl acetate, and butyl acetate. Examples of the polymerization initiator include one or more azo compounds and organic peroxides. Examples of azo compounds include azobisisobutyronitrile (AIBN), dimethyl 2,2'-azobis(2-methylpropionate), and 1,1'-azobis(cyclohexanecarbonitrile) (ABCN). Examples of organic peroxides include hydrogen peroxide, ditertiarybutyl peroxide (DTBP), benzoyl peroxide (benzoyl peroxide (BPO)), and methyl ethyl ketone peroxide (MEKP).

[0082] The reaction solution containing the (co)polymer thus obtained is added to an alcohol or ether, such as hexane or methanol, to precipitate the polymer. The polymer is then filtered, washed with an alcohol, such as hexane or methanol, and then dried. In this manner, the polymer can be synthesized. This allows the removal of low-molecular-weight components, such as residual monomers, oligomers, and polymerization initiators.

[0083] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations may be adopted. Furthermore, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Example]

[0084] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the descriptions of these examples.

[0085] <Production of Sensitized Particle Dispersion> (Production of aromatic latex particles) [Examples 1 to 3, Comparative Examples 1 to 4] The latex particles were synthesized according to the following procedure. 30 mL of ion-exchanged water and the ingredients listed in Table 1 were added to a reaction vessel according to the molar ratios listed in Table 1 and stirred. The atmosphere inside the reaction vessel was then replaced with nitrogen. After the temperature inside the reaction vessel reached 70°C, 0.75 mL of a 1.0 mass% aqueous potassium persulfate solution was added dropwise as a polymerization initiator. 24 hours after the addition of the aqueous potassium persulfate solution, the reaction was stopped. The particle suspension was recovered by filtration. The suspension was centrifuged and washed using methanol and ion-exchanged water to obtain a dispersion of aromatic latex particles (polystyrene-based latex particles).

[0086] Comparative Example 5 Synthesis was carried out under the same conditions as in Comparative Example 1, except that the blending ratio of Dispersant 1 (sodium methacrylate) was changed to 0.12 in terms of molar ratio, but it was confirmed that particles could not be produced. Comparative Example 6 Synthesis was carried out under the same conditions as in Comparative Example 1, except that the blending ratio of Dispersant 1 (sodium methacrylate) was changed to 0, but it was confirmed that particles could not be produced.

[0087] [Table 1]

[0088] In Table 1, the blending ratios of main backbone monomer 1, main backbone monomer 2, polymerizable silane coupling agent, dispersant 1, dispersant 2, and crosslinking agent are shown in molar ratios. However, * in Table 1 indicates that 2.2 wt% of crosslinking agent is blended with 100 wt% of main backbone monomer 1 (styrene).

[0089] Dispersant 1 shown in Table 1 was a compound represented by the following chemical formula A (sodium parastyrene). [ka]

[0090] Dispersant 2 shown in Table 1 was a compound represented by the following chemical formula B (carboxylic acid-containing oligomer-type silane coupling agent, manufactured by Shin-Etsu Chemical Co., Ltd., X-12-1135). [ka] (In the above general formula (B), X1 and X2 each represent a carboxylic acid (—COOH).)

[0091] The obtained styrene-based latex particles of each Example and Comparative Example were evaluated for the following items.

[0092] [Table 2]

[0093] <Particle size measurement> The dispersion (aqueous dispersion) containing the styrene-based latex particles obtained above was dried, and the resulting powder was fixed to a sample stage. The surface of the powder (sample) was coated by metal vapor deposition to prepare a sample. The obtained sample was observed using a JEOL scanning electron microscope, and the diameters of 30 or more particles observed in the image were measured. The average of the measured diameters was calculated as the average particle size. The CV value was also calculated from [standard deviation of average particle size / average particle size] x 100.

[0094] <Measurement of absorbance before and after dispersion test> The styrene-based latex particles (aromatic latex particles) obtained above were dispersed in water to a concentration of 0.2% by mass to obtain a dispersion medium. The dispersion medium was subjected to ultrasonic treatment using an ultrasonic homogenizer (manufactured by Branson) at a rated output of 450 W and amplitude control of 40%, with 10-second treatment repeated three times. Immediately after this, the absorbance at a wavelength of 700 nm was measured using an automatic analyzer TBA-120FR (manufactured by Canon Medical Systems Inc.), and the value was designated as A0. Subsequently, the ultrasonically treated dispersion medium was stored for one week in a sealed container in an environment at a temperature of 4° C. After storage, the supernatant of the dispersion medium was measured for absorbance at a wavelength of 700 nm without undergoing the ultrasonic treatment described above, and the value was designated as A1. Thereafter, the absorbance maintenance rate [%] was calculated from the measured A0 and A1 values ​​according to (A1 / A0)×100. In addition, the ultrasonically treated dispersion was stored under the same conditions for two weeks, and then the absorbance at a wavelength of 700 nm of the supernatant of the dispersion medium was measured as A2 after being left to stand for two weeks without undergoing the ultrasonic treatment described above. Using the measured values ​​of A0, A1, and A2, the "degree of sedimentation" per day was calculated from [[(A1 / A0) × 100] - (A2 / A0) × 100] / 7. The results in Table 2 above show that the dispersions containing aromatic latex particles of each Example had a higher absorbance retention rate after 2 weeks than the dispersions of each Comparative Example, and therefore exhibited excellent dispersion stability.

[0095] <Production of dispersion containing sensitized particles> (sensitization treatment) 940 μL of the dispersion containing the styrene-based latex particles obtained above (0.4% w / vol) to which the condensation agent described below had been further added was mixed with 940 μL of the antibody A solution described below (0.07 mg / mL), and the mixture was shaken and stirred at 20°C for 180 minutes to obtain a mixed solution. Condensing agent: Carbodiimide crosslinking agent (EDC, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, also known as WSC)

[0096] (Cleaning process) The resulting mixture was centrifuged at 10,000 rpm for 15 minutes at 10° C. using a centrifuge (rotor: R15A (HITACHI)). The supernatant was decanted, and 5 mL of the following HEPES buffer solution was added to the resulting sediment, which was then dispersed by sonication. Subsequently, the mixture was centrifuged at 10,000 rpm for 15 minutes at 10° C. using the above centrifuge. The supernatant was decanted, and 5 mL of the following HEPES buffer solution was added to the resulting sediment, which was then dispersed by sonication to obtain a suspension. HEPES buffer: 0.1% BSA, 10 mM HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, pH 7.2), 0.1% Tween 20, 0.05% NaN

[0097] (Blocking process) To the resulting suspension, 5 mL of the following blocking solution A was added, followed by 30 μL of additional blocking solution B and 19 μL of the above condensing agent (5 mg / mL WSC solution), and after thorough dispersion, the mixture was stirred at 37°C for 1 hour (reaction treatment).Then, using the above centrifuge, the mixture was centrifuged at 10,000 rpm for 15 minutes at 10°C to obtain ligand-sensitized particles. Blocking solution A: Bovine serum albumin (BSA) solution (1% BSA, 20 mM MES buffer (pH 6.0), 0.05% NaN3) Blocking solution B: Bovine serum albumin (BSA) solution (the molecular weight M of BSA is approximately 66,500, the Stokes radius r of BSA is 3.5 nm, 0.2% BSA, 20 mM MES buffer (pH 6.0), 0.05% NaN3)

[0098] (reagent processing) The following components were mixed in a predetermined mixing ratio and uniformly dispersed by ultrasonic treatment (dispersion treatment) to prepare a reagent (sensitized particle dispersion) with a solid content of 0.2%. The ligand-sensitized particles obtained above HEPES buffer containing 0.5% bovine serum albumin (BSA) 100mM NaCl ·0.09%NaN3 ·100mM HEPES buffer (pH7.0)

[0099] <Sensitivity evaluation> Using an automatic analyzer TBA-120FR (manufactured by Canon Medical Systems Inc.), the absorbance at a wavelength of 572 nm was measured for each of the reagents of each example and comparative example, the measurement reagents listed below, and the target substance (ferritin antigen solution), all kept at 10°C. (measurement reagents) The following components were mixed in a predetermined ratio to prepare a measuring reagent. 0.1% Tween 20 Polyethylene glycol (PEG) (5000-50000) 1% bovine serum albumin (BSA) in HEPES buffer 150mM NaCl ·0.09%NaN3 ·100mM HEPES buffer (pH7.6) Next, 20 μL of each reagent from each Example and Comparative Example was mixed with 80 μL of the above-mentioned measurement reagent and 4 μL of the target substance (antigen amount 0 ng / mL or 300 ng / mL), and the mixture was stirred uniformly and maintained at 37°C. The absorbance at a wavelength of 572 nm was measured immediately after adding the measurement reagent and after 5 minutes had elapsed. The absorbance for each reagent when the antigen amount was 0 ng / mL and 300 ng / mL was calculated by subtracting the absorbance immediately after adding the measurement reagent from the absorbance after 5 minutes. As an index of sensitivity, the difference in absorbance (ΔAbs) between the presence and absence of the target substance was calculated by subtracting the absorbance at a wavelength of 572 nm when the antigen amount was 0 ng / mL from the absorbance at a wavelength of 572 nm when the antigen amount was 300 ng / mL.

[0100] As a result of the above <Sensitivity Evaluation>, it was found that sensitivity evaluation could not be performed in any of Comparative Examples 1 to 4. Specifically, in Comparative Example 2, agglutination precipitation occurred after the sensitization treatment, making it impossible to measure sensitivity. In Comparative Examples 1 and 4, the agglutination reaction did not proceed even in the presence of antigen (antigen concentration 300 ng / mL) during sensitivity measurement, making it impossible to measure sensitivity. In Comparative Example 3, an agglutination reaction was observed in the presence of antigen (antigen concentration 300 ng / mL), but the difference in absorbance between the presence and absence of antigen (presence of antigen: antigen concentration 300 ng / mL, absence of antigen: antigen concentration 0 ng / mL) was small (less than 0.1), so sensitivity was insufficient. In contrast to this, in Examples 1 to 3, the difference in absorbance between the presence and absence of the antigen was 0.2 or more, demonstrating sufficient sensitivity.

[0101] The dispersions containing aromatic latex particles obtained in these examples can be used for various purposes, but it has been found that they can be suitably used as sensitized particle dispersions (reagents) for immunoagglutination methods. [Explanation of symbols]

[0102] 1. Core particle 3. Ligand 5. Blocking Proteins 20 Sensitizing particles

Claims

1. Aromatic latex particles having an absorbance retention rate of 91% or more in a dispersion medium, as calculated in accordance with the following dispersion test. (Dispersion Test) The aromatic latex particles are dispersed in water to a concentration of 0.2% by mass to obtain a dispersion medium. The dispersion medium thus obtained is subjected to ultrasonic treatment using an ultrasonic homogenizer under conditions of a rated output of 450 W and an amplitude control of 40%, with the treatment being repeated three times for 10 seconds. Immediately after this, the absorbance at a wavelength of 700 nm is measured and the value is designated as A0. Subsequently, the dispersion medium is stored in a sealed container at 4° C. for one week. After the storage is completed, the absorbance of the supernatant of the dispersion medium at a wavelength of 700 nm is measured without carrying out the ultrasonic treatment, and the value is designated as A1. Thereafter, the measured A0 and A1 are used to calculate the absorbance maintenance rate [%] from (A1 / A0)×100.

2. The aromatic latex particles according to claim 1, The composition comprises a structural unit A having an aromatic group and a silane coupling agent having a carboxy group, Aromatic latex particles, wherein the ratio of the silane coupling agent having a carboxy group to the structural unit A is 0.1% by mass or more and 20% by mass or less, based on mass.

3. 3. The aromatic latex particles according to claim 1 or 2, The compound has a structural unit A having an aromatic group and a structural unit C having a Si element, Aromatic latex particles, wherein the ratio of the structural unit C to the structural unit A is 0.01% by mass or more and 40% by mass or less on a weight basis.

4. 3. The aromatic latex particles according to claim 1 or 2, Aromatic latex particles having an average particle diameter of 80 nm or more and 700 nm or less.

5. 3. The aromatic latex particles according to claim 1 or 2, Aromatic latex particles, wherein the CV value of the average particle diameter of the aromatic latex particles is 15% or less.

6. 3. The aromatic latex particles according to claim 1 or 2, Aromatic latex particles, wherein a sedimentation degree calculated from [[(A1 / A0)×100]−(A2 / A0)×100] / 7 is 5.5 or less, where A2 is absorbance at a wavelength of 700 nm after two weeks of static storage measured in accordance with the dispersion test.

7. 3. The aromatic latex particles according to claim 1 or 2, Aromatic latex particles used for detecting target substances by agglutination methods.

8. A target substance detection reagent comprising the aromatic latex particles according to claim 1 or 2 and a dispersion medium.

9. A target substance detection kit comprising a reagent container containing the target substance detection reagent according to claim 8.

10. A method for detecting a target substance, comprising the step of mixing a target substance with the target substance detection reagent according to claim 8.

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