Single polymer particle, active molecule complex, method for producing single polymer particle, method for measuring tumor size, method for measuring microstructure in tumor, method for imaging biological tissue, drug delivery system, and contrast agent kit

Abstract

The present invention addresses the problem of providing: single polymer particles in which the hydrodynamic diameter is more accurately controlled; an active molecule complex; a method for producing single polymer particles; and a method for imaging a biological tissue. In order to solve the problem, provided are single polymer particles characterized in that each particle is formed from a single polymer and the molecular weight distribution (Mw / Mn) is 1.5 or less. As a result, particles having accurately controlled hydrodynamic diameters can be obtained. The single polymer is preferably a structure comprising a single hydrophilic polymer (A), or a structure in which one or more hydrophilic polymers (B) as side chains are bonded to a main chain comprising a single hydrophilic polymer (A).

Description

Technical Field

[0001] The present invention relates to particles whose hydrodynamic diameter is accurately controlled. More specifically, the present invention relates to: single polymer particles composed of a single polymer, active molecule complexes, methods for producing single polymer particles, methods for measuring tumor size, methods for measuring microstructures within tumors, methods for imaging biological tissues, drug delivery systems, and contrast agent kits. Background Art

[0002] For example, when low-molecular-weight drugs such as anticancer agents, contrast agents, and nucleic acid drugs are administered into the blood, they are rapidly excreted from the kidneys because their individual molecules are less than 5 nm in size, making them difficult to deliver to the target site. In addition, it is known that low-molecular-weight drugs can be filtered out of blood vessels due to their small molecular size, thereby affecting surrounding tissues.

[0003] In these cases, by combining low molecules with high molecules, aggregating them or aggregating them with lipids to increase the apparent molecular weight, it is possible to avoid excretion from the kidneys and filtration from blood vessels, thereby promoting the molecules to reach the target part. Such a technology that controls the dynamics of a drug in the body by controlling its molecular weight is called passive targeting technology, which is being actively studied as a field of DDS (drug delivery system) technology.

[0004] For example, Patent Document 1 describes a nuclear magnetic resonance contrast agent using polymer micelles containing a hydrophilic polymer segment. In this technology, the molecular weight of a hydrophilic low molecular weight contrast agent is controlled by using polymer micelles, thereby efficiently delivering the contrast agent to a target site.

[0005] In addition, Non-Patent Document 1 describes that micelles composed of block copolymers are likely to be used as a nanoscale medium to control the distribution and function of bioactive agents such as drugs, proteins, or nucleic acids, thereby effectively overcoming biological technical barriers.

[0006] (Prior art literature)

[0007] Patent Document 1: International Publication No. 2006 / 003731

[0008] Non-patent document 1: Horacio Cabral et al., Chem. Rev. 2018, 118, 6844-6892 Summary of the invention

[0009] (Problems to be solved by the invention)

[0010] However, in the technology of Patent Document 1, since the polymer micelle is an aggregate formed by a plurality of polymers, it is difficult to accurately control the molecular weight of the particles, so that the size of each particle is biased. Therefore, it is difficult to accurately control the dynamics of the particles in the body. In addition, the technology of Non-Patent Document 1 is also difficult to accurately control the size of each particle.

[0011] In addition, since each polymer micelle used in the above-mentioned technology is an aggregate formed by a plurality of polymers, its hydrodynamic diameter is generally large, about 30 nm to 80 nm, so it is difficult to reduce the hydrodynamic diameter of the particles from a technical perspective.

[0012] The object of the present invention is to provide: a single polymer particle whose fluid dynamics diameter can be more accurately controlled, an active molecule complex, a method for producing a single polymer particle, a method for measuring tumor size, a method for measuring microstructure within a tumor, a method for imaging biological tissue, a drug delivery system, and a contrast agent kit.

[0013] (Technical means to solve the problem)

[0014] The present inventors have conducted intensive research on the above-mentioned subject and found that particles with accurately controlled hydrodynamic diameter can be realized by using single polymer particles composed of a single polymer and having a molecular weight distribution of 1.5 or less. The present invention has been completed as a result.

[0015] That is, the present invention provides the following aspects [1] to

[16] .

[0016] [1] A single polymer particle, wherein each particle is formed of a single polymer, and the molecular weight distribution M of the single polymer is w / M n Below 1.5.

[0017] Thereby, particles whose hydrodynamic diameter is accurately controlled can be obtained.

[0018] [2] The single polymer particle according to [1], characterized in that the single polymer is a structure composed of a single hydrophilic polymer A, or a structure in which one or more hydrophilic polymers B as side chains are bonded to a main chain composed of a single hydrophilic polymer A.

[0019] Thereby, particles whose hydrodynamic diameter is more accurately controlled can be obtained.

[0020] [3] The single polymer particle according to [1] or [2], characterized in that the hydrophilic polymer A is a polypeptide, a polysaccharide, a vinyl polymer, a polyether polymer, a polyester polymer, or a polyoxazoline.

[0021] This makes it possible to easily control the molecular weight of a single polymer, and as a result, the hydrodynamic diameter of a single polymer particle can be controlled.

[0022] [4] The single polymer particle according to any one of [1] to [3], characterized in that the hydrophilic polymer B is polyalkylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, polyhydroxyethyl methacrylate, poly2-methoxyethyl acrylate, polyoxazoline, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, or carboxyvinyl polymer.

[0023] This makes it possible to easily control the molecular weight of a single polymer, and as a result, the hydrodynamic diameter of a single polymer particle can be controlled.

[0024] [5] The single polymer particle according to any one of [1] to [4], wherein the number of the hydrophilic polymers B as side chains bonded to the hydrophilic polymer A is 1 or more and 100 or less.

[0025] Thereby, particles whose hydrodynamic diameter is more accurately controlled can be obtained.

[0026] [6] The single polymer particle according to any one of [1] to [5], wherein the molecular weight of the single polymer is greater than or equal to 10 kDa and less than or equal to 1500 kDa.

[0027] Thereby, particles whose hydrodynamic diameter is more accurately controlled can be obtained.

[0028] [7] The single polymer particle according to any one of [1] to [6], wherein the hydrophilic polymer A is polyaspartic acid and the hydrophilic polymer B is polyethylene glycol.

[0029] Thereby, particles whose hydrodynamic diameter is more accurately controlled can be obtained.

[0030] [8] An active molecule complex characterized by being composed of an active molecule bonded to the single polymer particle described in any one of [1] to [6].

[0031] This makes it possible to realize an active molecular complex whose dynamics in vivo are controlled.

[0032] [9] The active molecule complex according to [8], characterized in that the active molecule is an antibody drug, a nucleic acid drug, a low molecular weight drug, a radiopharmaceutical, a contrast agent, or a chromophore.

[0033] Thus, a complex consisting of an antibody drug, a nucleic acid drug, a low-molecular drug, a radiopharmaceutical, a contrast agent or a chromophore and a single polymer particle can be obtained, the dynamics of which are controlled in the living body.

[0034]

[10] A method for producing single polymer particles, comprising the following steps: (i) synthesizing a linear hydrophilic polymer A by a ring-opening polymerization reaction using α-amino acid-N-carboxylic anhydride as a raw material; and (ii) combining a hydrophilic polymer B with a reaction site of the hydrophilic polymer A.

[0035] Thereby, particles whose hydrodynamic diameter is accurately controlled can be obtained.

[0036]

[11] A method for measuring tumor size, characterized in that the size of the tumor is measured using the single polymer particle described in any one of [1] to [7] or the active molecule complex described in [8] or [9].

[0037] Thereby, the size of the tumor can be measured.

[0038]

[12] A method for measuring microstructures within a tumor, characterized in that the microstructures within a tumor are measured using the single polymer particle described in any one of [1] to [7], or the active molecule complex described in [8] or [9].

[0039] This makes it possible to measure the microstructure within the tumor.

[0040]

[13] A method for imaging biological tissue, using the single polymer particle described in any one of [1] to [7] or the active molecule complex described in [8] or [9].

[0041] This makes it possible to more accurately image biological tissue.

[0042]

[14] The method for imaging living tissue according to

[13] , wherein the living tissue is a tumor.

[0043] This allows for more accurate imaging of tumors.

[0044]

[15] A drug delivery system that delivers the single polymer particle described in any one of [1] to [7], or the active molecule complex described in [8] or [9] to a target site in a living body.

[0045] This makes it possible to deliver single polymer particles and the like to a target location in a living body.

[0046]

[16] A contrast agent kit comprising active molecular complexes of different sizes among the active molecular complexes described in [8] or [9].

[0047] This makes it possible to more accurately understand the microstructure of biological tissues.

[0048] (Effects of the Invention)

[0049] According to the present invention, it is possible to provide: a single polymer particle whose fluid dynamics diameter is more accurately controlled, an active molecule complex, a method for producing a single polymer particle, a method for measuring tumor size, a method for measuring microstructure within a tumor, a method for imaging biological tissue, a drug delivery system, and a contrast agent kit. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 The results of analyzing the molecular weight distribution of the synthesized PBLA by the GPC method are shown.

[0051] Figure 2 The results of analyzing the synthesized PAsp-g-PEG2000, PAsp-g-PEG5000, PAsp-g-PEG12000, and PAsp-g-PEG20000 by the GPC method are shown.

[0052] Figure 3 The results of synthesizing single polymer particles with controlled hydrodynamic diameter are shown.

[0053] Figure 4 The results of a blood retention test of single polymer particles are shown.

[0054] Figure 5 Shown are the hydrodynamic diameter of a single polymer particle and its in vivo dynamics after intravenous administration.

[0055] Figure 6 The relaxometry results of the contrast agent bound to the single polymer particle of the present invention and the conventional contrast agent are shown.

[0056] Figure 7 An image obtained using the active molecular complex (contrast agent) of the present invention is shown.

[0057] Figure 8 An image obtained using a conventional contrast agent is shown.

[0058] Fig. 9 An image obtained using a contrast agent bound to a single polymer particle of the present invention is shown. DETAILED DESCRIPTION

[0059] Hereinafter, embodiments of the single polymer particle, active molecule complex, single polymer particle production method, and living tissue imaging method according to the present invention will be described in detail.

[0060] Here, the single polymer particle, active molecule complex, single polymer particle production method, and living tissue imaging method described in the embodiments are merely examples given to illustrate the present invention, and the present invention is not limited thereto.

[0061] [definition]

[0062] In this specification, "polymer" refers to a molecule with a relatively large molecular weight, which is a structure formed by multiple repetitions of substantial or conceptual units obtained from small molecular weight molecules, also known as a polymer molecule. Such polymers can be roughly classified into biological polymers and synthetic polymers. As specific biological polymers, for example, polypeptides formed from amino acid units, polysaccharides formed from monosaccharide units, and polynucleotides formed from nucleic acid units can be cited. As for specific synthetic polymers, polyester polymers formed from polycarboxylic acid units and polyol units, vinyl (CH 2 =CH-), namely, ethylene-based polymers, polymers having an ether bond (-COC-) in the main chain, namely, ether-based polymers, and polyamides composed of polycarboxylic acid units and polyamine units.

[0063] In this specification, "single polymer" refers to a single polymer bonded by covalent bonds, except for a complex formed by multiple molecules through hydrogen bonds, hydrophobic bonds or van der Waals forces. "Single polymer particles" refer to the following state: each single polymer does not associate secondarily into molecules in an aqueous solvent but is dispersed in the aqueous solvent, thereby exhibiting the properties of particles in the aqueous solvent. The single polymer particles of the present invention do not include complexes formed by multiple polymers such as micelles. In addition, the record of "single polymer particles" without special annotations refers to particles formed by a single polymer. It should be noted that the molecular weight distribution M of a single polymer is w / M n The description represents the molecular weight distribution of a collection of substantially identical single polymer particles obtained by the same production method, etc.

[0064] In this specification, "biocompatibility" refers to the property of having affinity with biological tissues or organs without causing foreign body reaction or rejection reaction, etc. The present invention is mainly intended for use in vivo, and therefore, as the above-mentioned polymer, a polymer having biocompatibility is preferably used.

[0065] In the present specification, the term "molecular weight" refers to a molecular weight measured by a TOF-MS method, a molecular weight calculated by an NMR method from terminal protons, or a molecular weight calculated by both methods.

[0066] In this specification, the term “number average molecular weight (M nThe "number average molecular weight" refers to the molecular weight calculated from the molecular weight per polymer (arithmetic mean) of the polymer contained in the collection of synthesized polymers. The number average molecular weight is determined by GPC (gel permeation chromatography).

[0067] In this specification, "weight average molecular weight (M w )" is an average molecular weight calculated based on weight fraction, and is an average value not based on the number of polymer radicals but based on "weight molecular weight x number of radicals". The weight average molecular weight is determined by GPC method.

[0068] In this specification, "molecular weight distribution" refers to the distribution of molecular weight and degree of polymerization of polymers, that is, the degree of deviation, which is obtained by GPC method. Molecular weight distribution is expressed as weight average molecular weight M w and number average molecular weight M n The ratio (M w / M n ) value. When the molecular weight distribution is 1.0 to 1.5, it is judged to be substantially monodisperse. The molecular weight distribution is obtained by the GPC method.

[0069] In this specification, "hydrodynamic diameter" refers to the particle size estimated from the particle movement speed. The hydrodynamic diameter d can be calculated by measuring the diffusion time using fluorescence correlation spectroscopy and using the Einstein-Stokes relationship (the following mathematical formula (1)). In this specification, "hydrodynamic diameter" and "particle size" are used with the same meaning.

[0070] d=kT / 3πη 0 D mathematical formula (1)

[0071] (k: Boltzmann constant, T: absolute temperature, η: solvent viscosity, D: translational diffusion coefficient)

[0072] [Single polymer particle]

[0073] The single polymer particles of the present invention are characterized in that each particle is formed of a single polymer and the molecular weight distribution M w / M n The hydrodynamic diameter of the particles can be precisely controlled.

[0074] Depending on the size of the particles taken into the organism, there is a mechanism in the organism that controls the dynamics of the particles in the organism, for example, there is a mechanism that allows particles below a certain size to pass through but prevents particles exceeding a certain size from passing through. By using the single polymer particle of the present invention, the dynamics of the particles in the body can be accurately controlled according to the purpose. By using the single polymer particle of the present invention, it can be used for the following purposes, for example: use as a contrast agent; use of adjusting the size of the single polymer particle of the present invention to prevent the single polymer from leaking from the blood vessels; use of promoting renal excretion to excrete from the organism as soon as possible; use of avoiding renal excretion to achieve retention in the organism; use as a single polymer particle that can be delivered to deep tissues; use for imaging biological tissues; use for measuring the size of biological tissues or depicting fine structures; use of single polymer particles or active molecule complexes with suitable fluid dynamics diameter or size combined with drugs in treatment; use of delivering active molecule complexes to target locations in the organism.

[0075] The following specific examples are given as examples of the above-mentioned utilization.

[0076] Gd ions used in contrast agents can be bound to particles and effectively delivered only to the target site, thereby avoiding the effects of filtration from blood vessels and toxicity to other tissues such as the brain.

[0077] Particles of a specific size (several to several tens of nm) that can be excreted through the kidneys can be prepared. Due to the specific size, the particles can be delivered to the inflammatory site or deep in the cancer tissue that cannot be delivered by conventional micelles of a size (tens to hundreds of nm).

[0078] The microstructure of tissues can be mapped using particles of precisely controlled size, and based on the results, particles of the appropriate size combined with drugs (active molecule complexes) can be used for treatment, thereby achieving effective treatment.

[0079] The molecular weight distribution of the single polymer particle of the present invention is 1.5 or less. The upper limit is preferably 1.4 or less, more preferably 1.3 or less, and further preferably 1.2 or less. By making the molecular weight distribution of the single polymer particle within the above range, particles with a more accurately controlled hydrodynamic diameter can be obtained.

[0080] The hydrodynamic diameter of the single polymer particle of the present invention varies depending on the purpose of the single polymer particle, but can be, for example, 1 to 100 nm. The hydrodynamic diameter of the single polymer particle can be controlled by controlling the molecular weight of the single polymer. As described later, the molecular weight of the single polymer can be controlled by controlling the molecular weight of the hydrophilic polymer A and the hydrophilic polymer B, and / or the number of hydrophilic polymers B combined.

[0081] In the above-mentioned examples of use of the single polymer particle, if the single polymer particle of the present invention is used as a contrast agent, for example, the hydrodynamic diameter thereof is preferably 0.5 nm or more, and more preferably 1 nm or more.

[0082] When used for preventing leakage from blood vessels, the hydrodynamic diameter is preferably 2 nm or more, more preferably 3 nm or more.

[0083] Furthermore, if the drug is to be excreted from the body as soon as possible by the kidney, its hydrodynamic diameter is preferably less than 5 nm.

[0084] Furthermore, if the polymer is to be used for purposes of avoiding renal excretion so that a single polymer particle is retained in the body, the hydrodynamic diameter is preferably 5 nm or more, and more preferably 6 nm or more.

[0085] Furthermore, when used as a single polymer particle that can be delivered deep into tissues, a smaller diameter is preferred, preferably 100 nm or less, and more preferably 30 nm or less.

[0086] The single polymer particle can be prepared as a single polymer particle composition comprising a plurality of single polymer particles. The single polymer particle composition generally includes a collection of single polymer particles obtained by the same production method, etc., preferably a collection of substantially identical single polymer particles. The molecular weight distribution M of the single polymer particle composition is w / M n The molecular weight distribution of the single polymer particle in the single polymer particle composition is represented by . The preferred ranges of the components in the single polymer particle composition are the same as those of the single polymer particle.

[0087] Hereinafter, each component constituting a single polymer particle will first be described in detail.

[0088] (Single polymer)

[0089] The single polymer particle of the present invention is formed by a single polymer. The single polymer is preferably a polymer mainly formed by hydrophilic units, and more preferably a polymer formed only by hydrophilic units. The single polymer preferably does not have a hydrophobic unit. In addition, the single polymer preferably has the following properties: the molecules do not associate with each other secondary, so that they exist in the form of a single polymer chain in an aqueous solvent.

[0090] The single polymer is not particularly limited, and may be a structure consisting of only a single hydrophilic polymer A, or a structure in which one or more hydrophilic polymers B are bonded as side chains to a single hydrophilic polymer A. From the viewpoint of accurately setting the molecular size in a wider range, a structure in which one or more hydrophilic polymers B are bonded as side chains to a single hydrophilic polymer A is preferred.

[0091] If the single polymer is a structure in which one or more hydrophilic polymers B are bonded as side chains to a main chain composed of a single hydrophilic polymer A, the hydrophilic polymer B preferably has a specific molecular weight. The structure of the single polymer may be, for example, a graft copolymer structure in which one polymer is used as a backbone and other types of polymers are grafted onto the backbone.

[0092] The molecular weight of the single polymer is appropriately set according to the purpose of use of the single polymer particle, preferably 1 to 2000 kDa. As a lower limit, it is more preferably 2 kDa or more, and more preferably 5 kDa or more. As an upper limit, it is preferably 1750 kDa or less, and more preferably 1500 kDa or less. By controlling the molecular weight of the single polymer, the hydrodynamic diameter of the single polymer particle can be controlled.

[0093] Specific examples of methods for controlling the molecular weight of a single polymer include the following methods: obtaining a polymer with a narrow molecular weight distribution by graft copolymerization, living polymerization or ring-opening polymerization, or obtaining a fraction having an appropriate molecular weight by fractionation after the preparation.

[0094] <Hydrophilic polymer A>

[0095] The hydrophilic polymer A forms the main chain of a single polymer. The hydrophilic polymer A, for example, has a straight-chain or branched structure. Preferably, it has a straight-chain structure. The hydrophilic polymer A is not particularly limited, but is preferably a polymer mainly composed of a straight-chain structure, and more preferably a polymer composed only of a straight-chain structure. As a specific hydrophilic polymer A, as long as it is a hydrophilic polymer, it is not particularly limited, and preferably a biocompatible polymer. As such a biocompatible polymer, for example, polypeptides, polysaccharides, ethylene polymers, polyether polymers, polyester polymers, polyoxazolines, polynucleotides, etc. can be cited. Among them, from the viewpoint of the ease of control of molecular weight, it is preferably a polypeptide or a polyamino acid, more preferably polyaspartic acid, polyglutamic acid, polylysine.

[0096] The molecular weight distribution of the hydrophilic polymer A is not particularly limited, but is preferably below 1.5. As an upper limit, it is more preferably below 1.4, further preferably below 1.3, and further preferably below 1.2. By making the molecular weight distribution of the hydrophilic polymer A within the above range, the molecular weight distribution of the single polymer particle can be better controlled. Since the molecular weight distribution of the single polymer particle is greatly affected by the molecular weight distribution of the single polymer main chain, i.e., the hydrophilic polymer A, the control of the molecular weight distribution of the hydrophilic polymer A is very important.

[0097] The molecular weight of the hydrophilic polymer A is not particularly limited, and is, for example, 1 to 100 kDa. The lower limit is preferably 1 kDa or more, more preferably 2 kDa or more, and the upper limit is preferably 80 kDa or less, and 50 kDa or less.

[0098] From the viewpoint of ease of controlling the molecular weight, the hydrophilic polymer A is particularly preferably a polypeptide synthesized by a ring-opening polymerization reaction using an α-amino acid-N-carboxylic anhydride as a raw material.

[0099] <Hydrophilic polymer B>

[0100] The hydrophilic polymer B is bonded as a side chain to the main chain composed of the hydrophilic polymer A. The molecular weight distribution of the hydrophilic polymer B is preferably 1.5 or less, more preferably 1.4 or less, further preferably 1.3 or less, further preferably 1.2 or less, and particularly preferably 1.1 or less. The hydrophilic polymer B is bonded to a certain reaction site present in the hydrophilic polymer A.

[0101] As a specific hydrophilic polymer B, as long as it is a hydrophilic polymer, there is no particular limitation, and it is preferably a hydrophilic biocompatible polymer. For example, polyalkylene glycol (e.g., carbon number 2 to 4), polyvinyl alcohol (PVA), polyvinyl pyrrolidone, polyhydroxyethyl methacrylate (PHEMA), poly 2-methoxyethyl acrylate (PMEA), polyoxazoline, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, carboxyvinyl polymer, etc. can be cited. Among them, from the viewpoint of the ease of control of molecular weight, polyethylene glycol (PEG) is preferred. As a specific polyethylene glycol, for example, PEG500, PEG2000, PEG5000, PEG10000, PEG20000, PEG40000, PEG80000, etc. can be cited.

[0102] The molecular weight of the hydrophilic polymer B is not particularly limited, and is, for example, 0.01 to 1000 kDa. As a lower limit, it is preferably 0.02 kDa or more, more preferably 0.05 kDa or more, and further preferably 0.1 kDa or more. As an upper limit, it is preferably 500 kDa or less, more preferably 200 kDa or less, and further preferably 100 kDa or less.

[0103] The number of hydrophilic polymers B bonded to a single hydrophilic polymer A is not particularly limited, and is, for example, 0 to 200. As a lower limit, it is preferably 0 or more, more preferably 1 or more, and further preferably 3 or more. As an upper limit, it is preferably 150 or less, more preferably 100 or less, and further preferably 50 or less.

[0104] [Active Molecular Complex]

[0105] The active molecule complex of the present invention is a product formed by combining an active molecule with the above-mentioned single polymer particle. Thus, an active molecule complex whose dynamics in the body can be controlled can be realized. As the binding mode of the active molecule, covalent bonds or ionic bonds can be cited. This binding mode also includes the coordination of metal ions used in contrast agents, etc. relative to chelate-forming functional groups in single polymers. Chelate-forming functional groups refer to functional groups that have elements with lone electron pairs (N, O, P, S, etc.) so that the electrons of the lone electron pair are supplied to metal ions to form strong coordination bonds.

[0106] (Active molecule)

[0107] The active molecule is not particularly limited, and any active molecule commonly used in the fields of pharmaceuticals and diagnostic drugs can be used, preferably an antibody drug, a low molecular weight drug, a nucleic acid drug, a radiopharmaceutical, a contrast agent, or a chromophore.

[0108] The antibody drug is not particularly limited, and examples thereof include drugs obtained by binding drugs such as low-molecular-weight drugs to antibodies that specifically bind to disease-related molecules, and examples thereof include drugs targeting cancer or autoimmune diseases.

[0109] As the antibody used for the antibody drug, there is no particular limitation, and any of polyclonal antibodies, monoclonal antibodies, and their fragments (e.g., Fab, F(ab)2, etc.) can be used. In addition, the class and subclass of immunoglobulin are not particularly limited. In addition, antibodies selected from an antibody library by phage display methods, etc., can also be used, and conventionally known antibodies can also be used.

[0110] The low-molecular-weight drugs are not particularly limited, but are mainly synthetic chemical substances having a molecular weight of 500 or less, and examples thereof include anticancer agents.

[0111] There are no particular limitations on nucleic acid drugs, and examples include polynucleotides or oligonucleotides formed from DNA, RNA, or derivatives thereof. The polynucleotide may be single-stranded or double-stranded. The polynucleotide may be a sequence that encodes or does not encode a protein.

[0112] As radiopharmaceuticals, technetium ( 99m Tc), thallium ( 201 Tl), gallium ( 67 Ga) and Indium ( 111 In、Fluorine 18 F) etc. In the case where a radiopharmaceutical is used as the active molecule, the active molecule complex can be imaged by PET (positron emission tomography) or SPECT (single photon emission tomography).

[0113] Examples of contrast agents include gadolinium, manganese, iron, iodine, etc. When the contrast agent is used as an active molecule, the active molecule complex can be used for MRI (magnetic resonance imaging) imaging.

[0114] As a chromophore, fluorescein isothiocyanate (FITC) is mentioned, for example.

[0115] [Method for producing single polymer particles]

[0116] The method for producing the single polymer particles of the present invention is not particularly limited, and examples thereof include synthesis by polycondensation between amino acids and carboxylic acids, peptide solid phase synthesis, etc. Among the synthesis by polycondensation between amino acids and carboxylic acids, a ring-opening polymerization reaction using α-amino acid-N-carboxylic anhydride as a raw material is preferred.

[0117] The ring-opening polymerization reaction using α-amino acid-N-carboxylic anhydride as a raw material is characterized by comprising the following steps.

[0118] (i) A step of synthesizing a linear hydrophilic polymer A by a ring-opening polymerization reaction using α-amino acid-N-carboxylic anhydride as a raw material.

[0119] (ii) A step of bonding the hydrophilic polymer B to the reaction site of the hydrophilic polymer A.

[0120] The method for producing single polymer particles of the present invention can easily produce particles whose hydrodynamic diameter is more accurately controlled and whose molecular weight distribution is low. In addition, by more strictly controlling each stage of the production method, the hydrodynamic diameter of the particles to be produced can be adjusted in units of 1 nm, thereby producing single polymer particles with a wide molecular weight range.

[0121] Step (i) is a step of synthesizing a linear hydrophilic polymer A by a ring-opening polymerization reaction using α-amino acid-N-carboxylic anhydride (also referred to as "α-amino acid-NCA") as a raw material. As a raw material, α-amino acid-N-carboxylic anhydride or a derivative thereof can be used. In the case where the side chain of the amino acid has a highly reactive functional group, from the viewpoint of suppressing side reactions, the functional group is preferably modified with a protective group. As specific highly reactive functional groups, carboxyl and the like can be cited. As such a raw material having a protective group, benzyl ester of α-amino acid-N-carboxylic anhydride and the like can be cited.

[0122] Step (ii) is a step of bonding the hydrophilic polymer B as a side chain to the reactive site of the main chain formed by the hydrophilic polymer A. Such reactive site is not particularly limited, but is preferably a highly reactive functional group, and specific examples thereof include a carboxyl group and the like.

[0123] [Imaging methods for biological tissues]

[0124] The method for imaging living tissue of the present invention is characterized by using the above-mentioned single polymer particle or active molecule complex of the present invention, thereby obtaining more detailed tissue structure information by imaging the living tissue.

[0125] In addition, by using single polymer particles whose size, i.e., hydrodynamic diameter, is accurately controlled to image biological tissues, it is possible to depict the microstructure of the tissues. At the same time, it is also possible to obtain information on what hydrodynamic diameter or size can achieve deep penetration into tissues. By using drugs with appropriate hydrodynamic diameters or sizes based on these results, or by using single polymer particles or active molecule complexes combined with drugs for treatment, more effective treatment can be achieved.

[0126] [Method for measuring tumor size]

[0127] In the tumor size measurement method of the present invention, a single polymer particle or active molecule complex of multiple different sizes, i.e., hydrodynamic diameters, is used. By using multiple single polymer particles controlled to have two or more different hydrodynamic diameters to image the tumor, the microstructure of the tumor tissue can be depicted, and information about which hydrodynamic diameter or size can achieve deep penetration into the tissue can be obtained. In addition, by using drugs with appropriate hydrodynamic diameters or sizes according to these results, or by applying single polymer particles or active molecule complexes combined with drugs to treatment, more effective tumor treatment can be achieved.

[0128] [Methods for measuring microstructures within tumors]

[0129] The method for measuring the microstructure in a tumor of the present invention is characterized in that the microstructure in a tumor is measured using a single polymer particle or an active molecule complex. In the method for measuring the microstructure, not only the size of the entire tumor can be measured, but also the microstructure in the tumor can be measured based on information on whether a single polymer can pass through. In addition, by selecting a drug with an appropriate hydrodynamic diameter or size based on these results, effective treatment can be performed.

[0130] [Drug delivery system]

[0131] The drug delivery system of the present invention is characterized in that single polymer particles or active molecule complexes are transported to the target position in the organism. As mentioned above, depending on the size of the particles taken in the organism, there is a dynamic mechanism of controlling the particles in the organism, such as there is a mechanism that allows particles below a certain size to pass through but prevents particles exceeding a certain size from passing through. By controlling the size of single polymer particles of the present invention, the drug delivery system of the present invention can accurately control the dynamics of particles in vivo according to purpose.

[0132] [Contrast agent kit]

[0133] The contrast agent kit of the present invention is characterized in that it contains a plurality of active molecular complexes of different sizes, i.e., hydrodynamic diameters. By using a plurality of single polymer particles controlled to have two or more different hydrodynamic diameters, information about which hydrodynamic diameter or size can achieve deep penetration into tissues can be obtained. In addition, according to these results, drugs with appropriate hydrodynamic diameters or sizes can be used to achieve effective treatment.

[0134] [Example]

[0135] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments, and various modifications can be made within the scope of the technical concept of the present invention.

[0136] (raw materials)

[0137] The raw materials used in the following examples are shown in Table 1. Here, n-butylamine, N,N-dimethylformamide, and dichloromethane among the raw materials were distilled from calcium hydride and used.

[0138] [Table 1]

[0139] Compound Name (Product Name) Manufacturer and seller n-Butylamine Fujifilm Wako Pure Chemical Industries, Ltd. N,N-Dimethylformamide Fujifilm Wako Pure Chemical Industries, Ltd. Dichloromethane Fujifilm Wako Pure Chemical Industries, Ltd. β-Benzyl-L-aspartic acid N-carboxylic anhydride Chuo Chemicals Co., Ltd. Methoxy PEG2000 (MEPA-20H) NOF Corporation Methoxy PEG5000 (MEPA-50H) NOF Corporation Methoxy PEG12000(MEPA-12T) NOF Corporation Methoxy PEG 20000 (MEPA-20T) NOF Corporation 1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride Fujifilm Wako Pure Chemical Industries, Ltd. N-Hydroxysuccinimide Fujifilm Wako Pure Chemical Industries, Ltd. Diethyl ether Fujifilm Wako Pure Chemical Industries, Ltd. Acetonitrile Fujifilm Wako Pure Chemical Industries, Ltd. Sodium hydroxide Fujifilm Wako Pure Chemical Industries, Ltd. Azido-PEG4-amine Tokyo Chemical Industry Co., Ltd. Sodium bicarbonate Fujifilm Wako Pure Chemical Industries, Ltd. Sulfo-Cy5-DBCO Lumiprobe D-PBS(-) Fujifilm Wako Pure Chemical Industries, Ltd.

[0140] 1. Experiment 1 Synthesis of a backbone composed of polyaspartic acid

[0141] (1) Synthesis of polyaspartic acid (PAsp)

[0142] The main chain composed of polyaspartic acid (PAsp) was synthesized by the following steps.

[0143] 1000 mg of β-benzyl-L-aspartic acid N-carboxylic anhydride (NCA-BLA) was weighed into a round-bottom flask and dissolved in 10 mL of N, N-dimethylformamide (DMF). In another round-bottom flask, 360 μL of a diluted solution obtained by diluting n-butylamine 100 times with dichloromethane and 10 mL of DMF were added and mixed. The NCA-BLA solution was added to the n-butylamine solution and stirred at 35 ° C for 5 days. Here, all the above reactions were carried out under an argon atmosphere, and the organic solvents used were used after distillation. After the reaction, the reaction solution was added dropwise to 400 mL of diethyl ether to precipitate polyaspartic acid-β-benzyl ester (PBLA). Then, the precipitate was recovered by suction filtration and dried under reduced pressure. For the obtained PBLA, the molecular weight distribution was analyzed by GPC method, and the molecular weight and degree of polymerization were determined by NMR method. The measurement results are shown in Table 2.

[0144] [Table 2]

[0145] Molecular weight (kDa) <![CDATA[Molecular weight distribution (M w / M n )]]> Degree of Polymerization PBLA 13.5 1.170 117

[0146] Next, 100 mg of PBLA was suspended in 4 mL of acetonitrile, and 4.9 mL of 0.5 M sodium hydroxide aqueous solution was added, and the reaction was allowed to react overnight at room temperature to deprotect the benzyl group from PBLA. The reaction solution was then added to a dialysis membrane (molecular weight cutoff: 6000-8000), and dialyzed twice with pure water as an external solution, twice with 0.01 M hydrochloric acid, and twice with pure water (each time for more than 2 hours), and then freeze-dried to obtain polyaspartic acid (PAsp).

[0147] (2) Introducing an azide group into the side chain carboxylic acid group of polyaspartic acid

[0148] In order to measure the hydrodynamic diameter by fluorescence correlation spectroscopy, an azide group was introduced into the side chain carboxylic acid group of PAsp according to the following procedure.

[0149] 10 mg of polyaspartic acid was weighed and added to 2.5 mL of 50 mM sodium bicarbonate to dissolve. Next, 289.6 μL of azido-PEG4-amine adjusted to a concentration of 30 μM with DMF was added, and 27 mg of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) was added, and stirred at room temperature for 3 hours. Then, the reaction solution was added to a dialysis membrane (molecular weight cutoff: 6000-8000), and dialyzed twice with pure water as an external liquid, and then dialyzed twice with 0.01 M hydrochloric acid, and then dialyzed twice with pure water (each time for more than 2 hours). By freeze-drying, polyaspartic acid (PAsp(N- 3 )). The obtained PAsp(N 3 The introduction rate of the azido group of ) was calculated by NMR method. The experimental results are shown in Table 3.

[0150] [Table 3]

[0151] Azide group introduction rate (%) Number of azide groups introduced <![CDATA[Pasp(N 3 )]]> 11％ 13

[0152] 2. Experiment 2 Synthesis of a single polymer

[0153] (1) To PAsp(N 3 )Introduced side chain (side chain: PEG2000, PEG5000, PEG12000)

[0154] Follow the steps below to send a 3 ) was introduced into a main chain consisting of PEG2000, PEG5000 and PEG12000 as a side chain to produce a single polymer.

[0155] Weigh 2 mg of PAsp (N 3 ) and dissolved it in 1 mL of DMF. In other sample bottles, methoxy PEG 2000, methoxy PEG 5000, and methoxy PEG 12000 were dissolved in DMF to a concentration of 50 mg / mL, and the solution was diluted with water relative to PAsp (N 3 ) was added to PAsp(N 3 ) solution. Then, relative to PAsp (N 3 ) was added with EDC in such a manner that the carboxyl group of the mixture was 5 equivalents, and the mixture was stirred for 3 hours. The decrease in the peak area of ​​each PEG compared to the initial value was measured by GPC, and the amount of the peak area of ​​each PEG compared to the initial value was calculated. 3 )The number of PEG roots introduced.

[0156] The results of GPC are shown in Table 4. Herein, PAsp grafted with a PEG side chain is hereinafter referred to as PAsp-g-PEGXX ("XX" represents the molecular weight of the PEG side chain).

[0157] (2) To PAsp(N 3 )Introduced side chain (side chain: PEG20000)

[0158] Follow the steps below to send a 3 ) were introduced into the main chain consisting of PEG20000 and PEG20000 as side chains, thereby producing a single polymer.

[0159] Weigh 2 mg of PAsp(N 3 ) and dissolved it in 1 mL of DMF. In another sample bottle, PEG20000 was dissolved in DMF to a concentration of 50 mg / mL, and the solution was diluted with water relative to PAsp (N 3 ) was added to PAsp(N 3 ) solution. Then, relative to PAsp (N 3 ) was added to the carboxyl group of PAsp (N 3 ) was added with EDC in such a manner that the carboxyl group of the mixture was 0.95 equivalent, and the mixture was stirred for 3 hours. The decrease in the peak area of ​​each PEG compared to the initial value was measured by GPC, and the amount of the peak area of ​​each PEG compared to the initial value was calculated. 3 The results are shown in Table 4.

[0160] [Table 4]

[0161] Number of side chain imports PAsp-g-PEG2000 80 PAsp-g-PEG5000 74 PAsp-g-PEG12000 60 PAsp-g-PEG20000 66

[0162] After synthesizing each PAsp-g-PEG, in order to remove unreacted PEG, it was separated by GPC, and then the reaction solution was added to a dialysis membrane (molecular weight cutoff: 6000-8000). As the external solution, it was dialyzed 3 times with 10mM phosphate buffer and then dialyzed 3 times with pure water. PAsp-g-PEG powder was obtained by freeze-drying.

[0163] (3) A fluorescent dye is introduced into each PAsp-g-PEG (this operation is used for size measurement (and measurement of in vivo dynamics) by fluorescence correlation spectroscopy described later and is not essential).

[0164] In order to perform size measurement by fluorescence correlation spectroscopy, a fluorescent dye (sulfo-Cy5-DBCO) was introduced into each PAsp-g-PEG according to the following procedure.

[0165] PAsp-g-PEG was dissolved in pure water at a concentration of 25 mg / mL. Sulfo-Cy5-DBCO was dissolved in DMSO at a concentration of 25 mg / mL, and 1 equivalent of sulfo-Cy5-DBCO was added to the azide group on the side chain of PAsp-g-PEG. The mixed solution was frozen at -20°C and then thawed in a refrigerator at +4°C, and this operation was repeated three times. Then, in order to remove unreacted sulfo-Cy5-DBCO, it was purified using a PD-10 column, and the product was recovered by freeze drying.

[0166] 3. Experiment 3 Determination of the physical properties of PAsp-g-PEG

[0167] (1) Evaluation of the hydrodynamic diameter of each PAsp-g-PEG

[0168] Each PAsp-g-PEG labeled with Sulfo-Cy5 was diluted to 2 nM with D-PBS (-), and the diffusion time was measured by fluorescence correlation spectroscopy, and the hydrodynamic diameter was calculated using the Einstein-Stokes relationship. Among them, Cy5 was used as a standard substance for the calculation of the diffusion coefficient. The measurement results of fluorescence correlation spectroscopy are shown in Table 5.

[0169] (2) Molecular weight of each PAsp-g-PEG

[0170] The molecular weight of the PEG measured by TOF-MS was added to the main chain molecular weight measured by NMR according to the number of introduced side chains, and the calculated value was used as the molecular weight of the entire single polymer.

[0171] (3) Determination of molecular weight distribution of each PAsp-g-PEG

[0172] The molecular weight distribution (Mw / Mn) of each PAsp-g-PEG was determined by GPC (gel permeation chromatography). The test results are shown in Table 5 and Figure 2 shown.

[0173] [Table 5]

[0174] Molecular weight (kDa) <![CDATA[Molecular weight distribution (M w / M n )]]> Mean hydrodynamic diameter (nm) <![CDATA[PAsp-g-PEG 2,000 ]]> 176.9 1.181 11.0±0.3 <![CDATA[PAsp-g-PEG 5,000 ]]> 384.2 1.190 15.0±0.3 <![CDATA[PAsp-g-PEG 12,000 ]]> 735.4 1.268 21.8±0.9 <![CDATA[PAsp-g-PEG 20,000 ]]> 1339.7 1.270 31.7±1.9

[0175] As shown in the above experimental results, a single polymer with a narrow molecular weight distribution and controlled hydrodynamic diameter was synthesized. Figure 2 A single peak was also obtained in the GPC results shown, indicating that the molecular weight distribution of each PAsp-g-PEG was narrow.

[0176] 4. Experiment 4 Evaluation of blood retention

[0177] A single polymer having a molecular weight controlled in the range of 10 kDa to 750 kDa was synthesized, and the blood retention was evaluated using single polymer particles composed of the synthesized single polymer.

[0178] Poly-L-aspartic acid was synthesized, and a single polymer having an arbitrary number of PEGs with a molecular weight of 2000 bound to poly-L-aspartic acid was synthesized by the same procedure as in Experiments 1 to 3 above. The molecular weight was controlled by the number of PEGs bound. The hydrodynamic diameter was evaluated, and the blood retention was evaluated using the fluorescently labeled polymer.

[0179] like Figure 3 As shown, by adjusting the molecular weight, a series of polymers can be obtained whose hydrodynamic diameters are precisely controlled in the range of 4 to 25 nm in units of 1 nm.

[0180] like Figure 4 As shown, according to the results of the blood retention test, polymers with a hydrodynamic diameter of 6 nm disappear from the blood very quickly, while polymers with a hydrodynamic diameter of 19 nm or more exhibit long-term blood retention with a half-life of 4 days.

[0181] 5. Experiment 5: Using muscular dystrophy model mice to evaluate the dynamics of single polymer particles in vivo

[0182] Single polymer particles labeled with fluorescence were intravenously administered to muscular dystrophy model mice, and the in vivo distribution was evaluated 48 hours later. For single polymer particles, particles with hydrodynamic diameters of 4nm, 10nm, 13nm, 15nm, and 22nm synthesized in Experiment 4 were used, and fluorescently labeled in the same manner as Experiments 1 and 2. In particular, single polymer particles with a hydrodynamic diameter of 4nm were evaluated as a nucleic acid drug model because they have the same hydrodynamic diameter as siRNA. The experimental results are as follows: Figure 5 and as shown in Table 6.

[0183] [Table 6]

[0184] Unit: Dose% / g

[0185] spleen kidney liver heart Diaphragm Skeletal muscle blood 4nm 0.504±0.434 33.947±7.698 8.384±0.987 0.387±0.128 0.468±0.105 0.290±0.152 (-0.711)±0.027 10nm 6.331±1.428 2.062±0.314 6.023±0.841 1.724±0.103 0.788±0.127 3.249±1.202 6.022±0.841 13nm 8.576±0.922 1.432±0.424 4.423±0.186 1.675±0.286 0.932±0.119 3.447±1.097 14.540±2.954 15nm 9.776±4.879 1.253±0.470 5.504±0.927 2.316±0.176 1.035±0.189 2.699±0.303 19.463±0.388 22nm 11.966±1.954 1.075±0.093 4.206±1.148 0.912±0.187 0.663±0.219 1.979±0.144 17.073±2.949

[0186] ※Mean ± SD

[0187] like Figure 5As shown in Table 6, when the size (hydrodynamic diameter) is the same as that of nucleic acid drugs, the amount of accumulation in the kidney is greater at the upstream of renal excretion, while in comparison, the accumulation of polymers larger than 10 nm in the kidney is greatly reduced. In addition, the amount of accumulation of polymers larger than 10 nm in the target muscle tissue is increased, which shows that the polymer conjugate has a good effect.

[0188] 6. Experiment 6 Evaluation of the cancer imaging effect in subcutaneous intestinal cancer transplantation model mice

[0189] The single polymer with a hydrodynamic diameter of 12 nm synthesized in Experiment 4 was combined with the DOTA complex and loaded with Gd. Its relaxation at 0.47T was evaluated and compared with the relaxation of the Gd contrast agent Magnescope (Gd-DOTA) commonly used in clinical practice. The drug was intravenously administered to subcutaneous intestinal cancer transplanted mice, and the cancer imaging effect was evaluated by 1T-MRI. The experimental results are shown in Table 7 and Figure 7 , 8 In addition, for each contrast agent, the ratio between its contrast effect on cancer and its contrast effect on muscle (Tumor / muscle ratio) was analyzed, and the results are shown in Table 6.

[0190] [Table 7]

[0191] <![CDATA[r 1 (mM -1 ·sec -1 )]]> <![CDATA[r 2 (mM -1 ·sec -1 )]]> <![CDATA[r 1 / r 2 ]]> Magnescope 3.72 4.68 0.795 Single polymer contrast agent 9.56 10.5 0.903

[0192] The results of the relaxation measurements shown in Table 7 show that a higher relaxation rate (r 1 ), and a higher positive effect (r 1 / r 2 ). Regarding the effect of cancer imaging, Figure 7 , 8 As shown, the contrast effect of the existing Magnescope is very limited, while the single polymer contrast agent achieves enhanced contrast intensity of cancer and contrast of the entire cancer. In addition, after 24 hours of contrast imaging with a single polymer contrast agent, a higher contrast effect (Tumor / muscle ratio of about 1.5) was observed.

[0193] 7. Experiment 7 Evaluation of the number of side chain introductions, molecular weight of polymer particles and imaging effect

[0194] Following Experiment 2, PEG2000 was reacted with the PAsp main chain at different concentrations to synthesize five polymers with PEG side chains, the number of side chain introduction being 2 to 18. Following Experiment 3, the molecular weight was measured.

[0195] Next, DOTA complexes were added to these polymers and Gd was loaded. Their relaxation at 0.47 T was evaluated in the same manner as in Experiment 6 and compared with the relaxation of the clinically commonly used Gd contrast agent Magnescope (Gd-DOTA). The results are shown in Table 8.

[0196] [Table 8]

[0197]

[0198] The results of the relaxation measurements shown in Table 8 show that by appropriately selecting the side chains, the number of introduced side chains, and the molecular weight, a relaxation significantly increased by 5.9 to 8.5 times compared to the currently clinically used Magnescope and an extremely high positive effect (r ) of 0.97, which has never been found before, was achieved. 1 / r 2 ). Through appropriate molecular design, it is possible to obtain higher contrast during imaging and to obtain the same degree of contrast with a smaller dosage.

[0199] 8. Experiment 8: Acquisition of accurate MRI images of cancer microstructure

[0200] The single polymer particles with a hydrodynamic diameter of 12 nm and loaded with Gd complex used in Experiment 6 were used to evaluate their cancer imaging effect on a patient-derived tumor (PDX) model (colon cancer subcutaneous transplantation model mouse model).

[0201] In the experiment, the drug was intravenously administered to PDX colorectal cancer subcutaneous transplanted mice, and the cancer imaging effect was evaluated 24 hours later.

[0202] like Fig. 9 As shown in the figure, when a contrast agent bound to a single polymer particle with a hydrodynamic diameter of 12 nm is used for MRI imaging, the area where the contrast agent is present in large quantities and the area where the contrast agent is not present are shown. This indicates that there are areas where the single polymer particle with a hydrodynamic diameter of 12 nm can penetrate and areas where it cannot penetrate, which can be considered to reflect the microstructure of the cancer. The arrows in the figure indicate high signal areas (white areas) where the contrast agent is particularly present.

[0203] The above results show that the size of the polymer contrast agent can be changed to use it as a ruler to measure the fine structure (the space in the cancer tissue). This means that nanomedicines with sizes corresponding to the measured fine structure can be used selectively.

[0204] This indicates that the single polymer particle technology of the present invention makes it possible to select nanomedicines of the most appropriate size for various cancers.

[0205] (Industrial Applicability)

[0206] The composition of the present invention can be used to provide: single polymer particles with more accurately controlled hydrodynamic diameter, active molecular complexes, methods for producing single polymer particles, and methods for imaging biological tissues.

Claims

1. A single polymer particle, characterized in that: Each particle is formed by a single polymer. The molecular weight distribution M of the single polymer w / M n Below 1.

5.

2. The single polymer particle according to claim 1, characterized in that: The single polymer is a structure composed of a single hydrophilic polymer A, or a structure in which a main chain composed of a single hydrophilic polymer A is bonded to one or more hydrophilic polymers B as side chains.

3. The single polymer particle according to claim 1 or 2, characterized in that: The hydrophilic polymer A is a polypeptide, a polysaccharide, a vinyl polymer, a polyether polymer, a polyester polymer, or a polyoxazoline.

4. The single polymer particle according to any one of claims 1 to 3, characterized in that The hydrophilic polymer B is polyalkylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone, polyhydroxyethyl methacrylate, poly-2-methoxyethyl acrylate, polyoxazoline, carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, or carboxyvinyl polymer.

5. The single polymer particle according to any one of claims 1 to 4, characterized in that The number of the hydrophilic polymer B as the side chain bonded to the hydrophilic polymer A is 1 or more and 100 or less.

6. The single polymer particle according to any one of claims 1 to 5, characterized in that The molecular weight of the single polymer is greater than or equal to 10 kDa and less than or equal to 1500 kDa.

7. The single polymer particle according to any one of claims 1 to 6, characterized in that The hydrophilic polymer A is polyaspartic acid, The hydrophilic polymer B is polyethylene glycol.

8. An active molecule complex, characterized in that The active molecule is combined with the single polymer particle according to any one of claims 1 to 7.

9. The active molecule complex according to claim 8, characterized in that The active molecule is an antibody drug, a nucleic acid drug, a low molecular weight drug, a radiopharmaceutical, a contrast agent, or a chromophore.

10. A method for producing single polymer particles, comprising the following steps: (i) a step of synthesizing a linear hydrophilic polymer A by a ring-opening polymerization reaction using α-amino acid-N-carboxylic anhydride as a raw material; (ii) A step of bonding the hydrophilic polymer B to the reaction site of the hydrophilic polymer A.

11. A method for measuring tumor size, characterized in that: The size of a tumor is measured using the single polymer particle according to any one of claims 1 to 7 or the active molecule complex according to claim 8 or 9.

12. A method for measuring microstructure in a tumor, characterized in that: The microstructure in a tumor is measured using the single polymer particle according to any one of claims 1 to 7 or the active molecule complex according to claim 8 or 9.

13. A method for imaging biological tissue, characterized in that: The single polymer particle according to any one of claims 1 to 7 or the active molecule complex according to claim 8 or 9 is used.

14. The method for imaging living tissue according to claim 13, characterized in that: The biological tissue is a tumor.

15. A drug delivery system, characterized in that: The single polymer particle according to any one of claims 1 to 7 or the active molecule complex according to claim 8 or 9 is delivered to a target site in a living body.

16. A contrast agent kit, characterized in that: The active molecular complex according to claim 8 or 9 comprises a plurality of different sizes.

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