Embolic substance

Abstract

The present invention provides a novel embolic substance.　Specifically, the present invention provides an embolic substance containing a temperature-responsive polymer and nanofibers.

Description

Embolic material

[0001] The present invention relates to embolic materials.

[0002] Patent Document 1 discloses that an aqueous solution of poloxamer 407 can be used as a liquid embolic agent to form a temporary embolism in a vascular region of a mammal.

[0003] Japan Special Table No. 2006-521177

[0004] The present invention provides a novel embolic material.

[0005] Interventional radiology (IR) is a treatment method that uses medical instruments such as catheters while using diagnostic imaging equipment. In IR vascular embolization, embolic materials are used to block blood flow for pathological conditions such as hemorrhage, aneurysms, and vascular malformations. Among these, liquid embolic materials are most commonly used in IR.

[0006] N-butyl-2-cyanoacrylate (hereinafter referred to as NBCA), a cyanoacrylate drug, is used worldwide as a liquid embolic agent. NBCA forms a thrombus by hardening near the catheter tip and adhering to the vascular wall at the same time. However, because the hardening of NBCA progresses irreversibly and quickly, it is difficult to interrupt the injection of NBCA during surgery. As a result, embolization using NBCA is uncertain. Furthermore, because NBCA is an instant adhesive, there have been reported cases where the catheter adhered to the blood vessel remains in the body, or where the catheter is blocked by the hardened embolic material. For this reason, embolization using NBCA requires proficiency in the technique.

[0007] Absolute ethanol (100% ethanol) is also used as a permanent liquid embolic agent in vascular embolization procedures for various diseases. However, absolute ethanol has side effects such as pain and damage to surrounding organs, and its use often requires systemic management. For this reason, intravascular administration of ethanol is generally contraindicated. Furthermore, absolute ethanol requires the use of a contrast agent for visualization, and dilution by the contrast agent reduces its effectiveness as an embolic agent.

[0008] The embolization obtained by the method described in Patent Document 1 does not have sufficient strength. Patent Document 1 discloses that even if a blood vessel can be occluded using a poloxamer, the blood vessel reopens in a short period of time due to dissolution of the poloxamer. In other words, when the embolization composition described in Patent Document 1 is used, there is a risk that reopening of the embolized blood vessel may cause rebleeding or recurrence or relapse of the lesion.

[0009] Thus, while conventional liquid embolic materials exert a strong embolization effect, they may cause complications due to over-embolization, off-target embolization, etc. Therefore, there is a need for the development of new liquid embolic materials that are safe and easy to use.

[0010] The present inventors have conducted extensive research to achieve the above-mentioned object. As a result, they have found that an embolism having good strength can be easily formed by using an embolic material containing a temperature-responsive polymer and nanofibers. Based on this finding, the present inventors have conducted further research and have completed the present invention. That is, the present invention includes the following features.

[0011] Item 1. An embolic material containing a temperature-responsive polymer and a nanofiber.

[0012] Item 2. The embolic material according to Item 1, wherein the temperature-responsive polymer has a lower critical solution temperature (LCST) within the range of 10°C to 40°C.

[0013] Item 3. The embolic material according to Item 1 or 2, wherein the temperature-responsive polymer is at least one temperature-responsive polymer selected from the group consisting of poloxamer, poloxamine, poly(N-isopropylacrylamide), and cellulose derivatives.

[0014] Item 4. The embolic material according to any one of Items 1 to 3, wherein the content of the temperature-responsive polymer is 10% by mass to 50% by mass, with the total mass of the embolic material being 100% by mass.

[0015] Item 5. The embolic material according to any one of Items 1 to 4, wherein the nanofiber is at least one type of nanofiber selected from the group consisting of: at least one type of natural nanofiber selected from the group consisting of cellulose nanocrystals, cellulose nanofibers, bacterial nanocellulose, silk fibroin nanofibers, collagen nanofibers, and gelatin nanofibers; and at least one type of synthetic nanofiber selected from the group consisting of polylactic acid nanofibers, polycaprolactone nanofibers, polyurethane nanofibers, and polylactic acid-glycolic acid copolymer nanofibers.

[0016] Item 6. The embolic material according to any one of Items 1 to 5, wherein the temperature-responsive polymer is a poloxamer and the nanofiber is a cellulose nanofiber.

[0017] Item 7. The embolic material according to any one of Items 1 to 6, wherein the content of the nanofibers is 0.1% by mass to 10% by mass, with the total mass of the embolic material being 100% by mass.

[0018] Item 8. The embolic material according to any one of Items 1 to 7, wherein the content of the nanofibers is 0.2 parts by mass to 100 parts by mass per 100 parts by mass of the temperature-responsive polymer.

[0019] Item 9. The embolic material according to any one of Items 1 to 8, further comprising a contrast agent.

[0020] Item 10. The embolic material according to Item 9, wherein the content of the contrast agent is 10% by mass to 70% by mass, with the total mass of the embolic material being 100% by mass.

[0021] Item 11. The embolic material according to any one of Items 1 to 10, further comprising a physiologically active substance.

[0022] According to the method of the present invention, a new embolic material can be provided.

[0023] A shows the relationship between viscosity η and temperature T for Example 1 (PL-CNF). B shows the relationship between storage modulus G′, loss modulus G″, and complex viscosity η for Example 1 (PL-CNF). ＊ and temperature. C shows the relationship between viscosity η and temperature T of Example 2 (PL-Silk). D shows the relationship between storage modulus G', loss modulus G'', and complex viscosity η of Example 2 (PL-Silk). ＊1 shows the relationship between each of these and temperature. For Comparative Example 1 (PL alone) and Example 1 (PL-CNF), A shows the viscosity η at 20°C and 37°C. B shows the storage modulus G' and loss modulus G'' at 37°C. For Comparative Example 1 (PL alone) and Example 2 (PL-Silk), C shows the viscosity η at 20°C and 37°C. D shows the storage modulus G' and loss modulus G'' at 37°C. An image of the embolic material of the present invention observed with an X-ray fluoroscopy device is shown. From left to right, the embolic materials of Example 1 (PL-CNF (53% by mass contrast agent)), Example 3 (PL-CNF (pure water)), and Example 2 (PL-Silk (53% by mass contrast agent)) are shown. A shows the device used in the embolization experiment of the blood flow circuit using a pulsatile flow pump. The left photograph in A is a photograph of the entire apparatus used in the embolization experiment, and the right photograph in A is a photograph demonstrating that the embolic material of the present invention can be injected through a catheter. (B) shows the results of tube embolization. From top to bottom, the figures show tubes embolized with the embolic materials of Reference Example 1 (10% NBCA), Comparative Example 2 (20% PL), Example 1 (16% PL by mass + 1% CNF by mass), and Reference Example 2 (33% NBCA), as well as the distance required for embolization. (a) shows the tail artery exposed by incision in the rat's tail. (b) shows the insertion of a catheter into the rat's tail artery. (c) is an angiogram showing the right kidney before embolization. The white arrow in (c) indicates the tip of the catheter. (d) is an angiogram showing the right kidney after embolization. The white arrow in (d) indicates contrast agent that has partially refluxed into the abdominal aorta. (e) is a photograph of the kidney in the embolization group (scale bar: 10 mm). The white arrow in (e) indicates neovascularization. f shows a photograph of the kidney in the non-embolization group (scale bar: 10 mm). a shows the results of HE staining. b and c show the results of immunohistochemical staining (CD-31 and F4 / 80). In each of a to c, from left to right, the non-embolization group and the embolization group (infarction area, acute tubular necrosis area) are shown (scale bar: 250 μm). d and e show the positive rates of CD-31 and F4 / 80, respectively (ns: not significant, *: P<0.05). The white dashed lines in c indicate the boundaries of the infarction area and acute tubular necrosis area. f shows the staining results of the cross-sections of embolization and blood vessels (HE staining, CD-31, from top to bottom) (scale bar: 100 μm). The white lines in f indicate embolic material.

[0024] In this specification, the expressions "contain" and "comprise" include any of "contain," "comprise," "consist only of," "consist essentially only of," and "consist only of."

[0025] In this specification, the expression "A to B" indicating a range of values ​​means "greater than or equal to A and less than or equal to B."

[0026] As used herein, "embolization" refers to the temporary or permanent occlusion of a blood vessel. Furthermore, as used herein, "embolization" can also refer to the plug itself used to temporarily or permanently occlude a blood vessel. Clinically, embolization may be required to block blood flow in response to pathological conditions such as hemorrhage, aneurysm, and vascular malformation. For clarity, as used herein, "embolic substance" refers to a substance (composition) used for embolization or to form an embolism.

[0027] The embolic material of the present invention will now be described.

[0028] 1. Embolic Material The embolic material of the present invention contains a temperature-responsive polymer and nanofibers. The embolic material of the present invention, having the above-described configuration, can enhance the mechanical properties and stability of the embolism formed by gelling the temperature-responsive polymer by incorporating nanofibers into the embolism. Furthermore, the embolic material of the present invention is an innovative embolic material that is liquid before injection into a living body and gels after injection into a living body. Thus, the present invention can provide an embolic material that can easily form an embolism with good strength. Furthermore, the embolic material of the present invention contains components that are easy to handle. Furthermore, the embolic material of the present invention can be manufactured using less expensive materials than conventional embolic materials, thereby significantly contributing to medical economics. Based on the above, the present invention can provide a novel embolic material that can replace the embolic materials used in conventional vascular embolization.

[0029] 1-1. Temperature-responsive polymer The temperature-responsive polymer used in the present invention is not particularly limited as long as it can gel after being injected into a living body. In this specification, the term "temperature-responsive polymer" refers to a polymer that can gel in response to the ambient temperature.

[0030] The temperature-responsive polymer may be any of a block copolymer, a random copolymer, a graft polymer, and a branched polymer. Among these, from the viewpoint of embolization, a block copolymer is preferable as the temperature-responsive polymer.

[0031] From the viewpoint of forming an embolism, the temperature-responsive polymer is preferably a polymer that exhibits a lower critical solution temperature (LCST)-type phase transition. An LCST-type phase transition refers to a polymer that dissolves in water at a low temperature and becomes insoluble and becomes cloudy or precipitates when heated to the LCST. In this case, the LCST is preferably in the range of 10°C to 40°C, more preferably in the range of 20°C to 40°C, and even more preferably in the range of 30°C to 40°C. The temperature-responsive polymer used in the present invention is liquid at room temperature, and therefore can be injected into or near a target lesion using a catheter or needle, even when combined with nanofibers. On the other hand, the temperature-responsive polymer used in the present invention gels after injection into a living body, thereby enabling temporary or permanent occlusion of blood vessels, even when combined with nanofibers.

[0032] Specific examples of the temperature-responsive polymer include poloxamer, poloxamine, poly(N-isopropylacrylamide), poly(N-alkylacrylamide), poly(N-vinylalkylamide), polyvinyl alkyl ether, and cellulose derivatives (methylcellulose, hydroxypropyl cellulose, etc.). From the viewpoints of easy embolization and safety, the temperature-responsive polymer is preferably at least one temperature-responsive polymer selected from the group consisting of poloxamer (PL), poloxamine, poly(N-isopropylacrylamide), methylcellulose, and hydroxypropylcellulose, more preferably at least one temperature-responsive polymer selected from the group consisting of poloxamer, poloxamine, and poly(N-isopropylacrylamide), and even more preferably poloxamer.

[0033] As used herein, poloxamer refers to a (tri)block copolymer having a polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide (PEO) structure, and is also known as Pluronic®. Specific examples of poloxamers include poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol), such as poloxamer 407, poloxamer 338, and poloxamer 188.

[0034] As used herein, poloxamine refers to a block copolymer having a polyethylene oxide (PEO)-polypropylene oxide (PPO) structure with ethylenediamine added thereto. Specific examples of poloxamine include poloxamine 1107, poloxamine 1307, and poloxamine 908.

[0035] Among the above specific examples of poloxamers and poloxamines, poloxamer 407, poloxamer 188, and poloxamine 908 are preferred, with poloxamer 407 being more preferred, from the viewpoints of ease of embolization and safety.

[0036] The temperature-responsive polymers used in the present invention may be used alone or in combination of two or more kinds. Furthermore, the temperature-responsive polymers used in the present invention may be synthesized or commercially available.

[0037] The molecular weight of the temperature-responsive polymer is not particularly limited. From the viewpoint of embolization ability, the weight-average molecular weight Mw of the temperature-responsive polymer is preferably 1,000 to 1,000,000, more preferably 2,000 to 200,000, and even more preferably 5,000 to 50,000. In this specification, the weight-average molecular weight (Mw) of the temperature-responsive polymer can be a standard polystyrene-equivalent value determined based on measurements by gel permeation chromatography (GPC).

[0038] The polydispersity index (molecular weight distribution; Mw / Mn) of the temperature-responsive polymer is preferably 2.0 to 1.0, more preferably 1.5 to 1.0, and even more preferably 1.2 to 1.0, from the viewpoint of embolization ability.

[0039] The content of the temperature-responsive polymer in the embolic material of the present invention is not particularly limited. From the viewpoint of easily forming an embolism having good strength, the content of the temperature-responsive polymer is preferably 10% by mass to 50% by mass, more preferably 10% by mass to 40% by mass, and even more preferably 10% by mass to 30% by mass, based on 100% by mass of the total mass of the embolic material (composition).

[0040] The temperature-responsive polymer used in the present invention is preferably biocompatible. Alternatively, the temperature-responsive polymer used in the present invention is preferably one that can be slowly decomposed or absorbed in vivo. This is advantageous in that complications due to over-embolization and off-target embolization can be easily avoided. If the temperature-responsive polymer is very slowly decomposed or absorbed in vivo, this means that the embolic material of the present invention will substantially permanently occlude the blood vessel.

[0041] 1-2. Nanofibers The nanofibers used in the present invention are not particularly limited as long as they are nanoscale fibers. In this specification, the term "nanofibers" refers to fibrous materials in which at least one of the fiber diameter (minor diameter and major diameter) and fiber length is nanoscale (less than 1 μm). Preferably, nanofibers refer to fibrous materials in which the fiber diameter (particularly the major diameter) is 1 nm to 100 nm and the fiber length is 100 times or more the fiber diameter (particularly the major diameter).

[0042] The fiber diameter of the nanofiber is not particularly limited, but is preferably 1 nm to 100 nm, more preferably 2 nm to 50 nm, and even more preferably 3 nm to 30 nm. By setting the fiber diameter within this range, the embolic material of the present invention can easily form an embolism with good strength.

[0043] The fiber length of the nanofiber is not particularly limited, but is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 500 nm or more. By setting the fiber length within this range, the embolic material of the present invention can easily form an embolism with good strength.

[0044] The nanofibers may be either natural nanofibers or synthetic nanofibers. From the viewpoint of easily forming an embolism with good strength, the natural nanofibers are preferably at least one type of nanofiber selected from the group consisting of cellulose nanocrystals, cellulose nanofibers (CNF), bacterial nanocellulose, silk fibroin nanofibers, collagen nanofibers, and gelatin nanofibers. The synthetic nanofibers are preferably at least one type of nanofiber selected from the group consisting of polylactic acid nanofibers, polycaprolactone nanofibers, polyurethane nanofibers, and polylactic acid-glycolic acid copolymer nanofibers. The nanofibers are more preferably at least one type of nanofiber selected from the group consisting of cellulose nanofibers, silk fibroin nanofibers, and polylactic acid-glycolic acid copolymer nanofibers, and even more preferably at least one type of nanofiber selected from the group consisting of cellulose nanofibers and silk fibroin nanofibers. It is particularly preferable that the temperature-responsive polymer is a poloxamer and the nanofiber is a cellulose nanofiber.

[0045] In this specification, cellulose nanocrystal means a fibrous material consisting of cellulose microfibrils or bundles thereof, with a fiber diameter of 3 nm to 100 nm, a fiber length of 100 nm to 1 μm, and an aspect ratio of about 5 to 50.

[0046] In this specification, cellulose nanofiber refers to a fibrous material consisting of cellulose microfibrils or bundles thereof, with a fiber diameter of 1 nm to 100 nm, a fiber length of 100 nm to several μm, and an aspect ratio of about 100 or more.

[0047] In this specification, bacterial nanocellulose refers to a fibrous substance that is a bundle of cellulose microfibrils synthesized by bacteria such as acetic acid bacteria, and has a fiber diameter of 3 nm to 100 nm, a fiber length of 100 nm to several tens of μm, and an aspect ratio of 2 to 50.

[0048] As used herein, silk fibroin nanofiber refers to a fibrous material consisting of individual silk fibroin microfibrils or bundles thereof, with a fiber diameter of 10 nm to several hundred nm, a fiber length of several hundred nm to several tens of μm, and an aspect ratio of 5 to 50.

[0049] The nanofibers used in the present invention may be used alone or in combination of two or more types. Furthermore, the nanofibers used in the present invention may be synthesized or commercially available.

[0050] The content of nanofibers in the embolic material of the present invention is not particularly limited. From the viewpoint of easily forming an embolism having good strength, the content of nanofibers is preferably 0.1% by mass to 10% by mass, more preferably 0.2% by mass to 5% by mass, and even more preferably 0.5% by mass to 3% by mass, based on 100% by mass of the total mass of the embolic material (composition).

[0051] Furthermore, from the viewpoint of easily forming an embolism having good strength, the content of the nanofibers is preferably 0.2 parts by mass to 100 parts by mass, more preferably 1 part by mass to 50 parts by mass, and even more preferably 5 parts by mass to 20 parts by mass, relative to 100 parts by mass of the temperature-responsive polymer.

[0052] The embolic material of the present invention, which contains a temperature-responsive polymer and nanofibers, is believed to form a strong embolism in vivo through interactions between the embolic material and red blood cells, platelets, and coagulation factors. The time (embolization time) during which the embolic material embolizes a blood vessel after forming an embolism can be adjusted by appropriately selecting the nanofiber content relative to the temperature-responsive polymer. In other words, by increasing the nanofiber content, the embolization time can be further extended compared to when the temperature-responsive polymer alone is used as an embolic material. For example, the nanofiber content relative to the temperature-responsive polymer can be determined so as to achieve an embolization time that exceeds the time required for tissue repair in the treatment of hemorrhage, the time required for tumor ischemic necrosis in the treatment of blocking tumor blood flow, and the time required for lesion shrinkage in the treatment of aneurysms and arteriovenous malformations.

[0053] The nanofibers used in the present invention are preferably biocompatible. Alternatively, the nanofibers used in the present invention are preferably degradable or absorbable in vivo. This is advantageous in that complications due to over-embolization, off-target embolization, and the like can be easily avoided.

[0054] 1-3. Other ingredients

[0055] In addition to the above-mentioned components, the embolic material of the present invention preferably further contains a contrast agent, which allows the position of the embolic material to be visualized and tracked during radiotherapy (IR).

[0056] The contrast agent that can be used in the present invention is not particularly limited, and a wide range of known contrast agents used in radiotherapy (IR) can be employed. The contrast agent can be any material that can enhance contrast using, for example, magnetic resonance, X-ray, ultrasound, magnetic tomography, electrical impedance imaging, optical (fluorescence) imaging, and nuclear imaging. Among these, iodine contrast agents are most preferred for use in IR, since X-rays are primarily used. Other preferred contrast agents include radiopaque materials containing metals or their oxides. Examples of such metals include, but are not limited to, Gd, Dy, Fe, Mn, Ho, Ni, Co, Eu, Pb, Ba, Ag, Au, W, Cu, and Bi. Other examples include ultrasound contrast agents such as galactose-palmitic acid mixtures and perfluorobutane, and magnetic resonance imaging (MRI) contrast agents containing metals or their oxides. Examples of such metals include, but are not limited to, Gd, Fe, Mn, Ni, Co, Eu, Pb, Au, Cu, and Bi.

[0057] Examples of contrast agents include water-soluble contrast agents and water-insoluble contrast agents. Examples of water-soluble contrast agents include water-soluble iodine contrast agents (iohexol, iopamidol, sodium amidotrizoate meglumine, etc.), water-soluble Gd contrast agents (gadobutrol, gadoterate meglumine, etc.), and manganese(II) chloride tetrahydrate. Examples of water-insoluble contrast agents include oil-based iodine contrast agents (iodized poppy seed oil fatty acid ethyl esters), tantalum, tantalum oxide, and barium sulfate.

[0058] The contrast agent used in the present invention may be used alone or in combination of two or more kinds. In addition, the contrast agent used in the present invention may be a synthesized product or a commercially available product.

[0059] The content of the contrast agent in the embolic material of the present invention is not particularly limited. From the viewpoint of easily forming an embolism having good strength, the content of the contrast agent is preferably 5% by mass to 80% by mass, more preferably 10% by mass to 70% by mass, and even more preferably 15% by mass to 60% by mass, based on 100% by mass of the total mass of the embolic material (composition).

[0060] The embolization time also varies depending on the content of the contrast agent in the embolic material of the present invention. Therefore, the content of the contrast agent in the embolic material can be determined to an appropriate amount depending on the purpose of treatment, etc., in the same way as the content of the nanofiber relative to the temperature-responsive polymer.

[0061] Alternatively, in the embolic material of the present invention, the temperature-responsive polymer itself or the nanofiber itself may serve as a contrast agent. Specifically, for example, by combining the temperature-responsive polymer or nanofiber with the above-mentioned radiopaque material, the embolic material can be tracked without further adding a known contrast agent. This is advantageous in that dilution of the embolic material due to the addition of a contrast agent can be avoided.

[0062] Physiologically Active Substance The embolic material of the present invention preferably further contains a physiologically active substance in addition to the above-mentioned components, which can enhance the effect of the embolic material of the present invention or the therapeutic or preventive effect of radiotherapy (IR).

[0063] The physiologically active substance that can be used in the present invention is not particularly limited, and a wide range of known physiologically active substances used in radiotherapy (IR) can be used. Examples of physiologically active substances include, but are not limited to, proteins, nucleic acids, drugs, and cells.

[0064] The protein is not particularly limited and a wide variety of known proteins can be used, including enzymes, receptors, antibodies, antigens, vaccines, cytokines such as interferons and interleukins, chemokines, transport proteins, etc. Furthermore, the protein may be complexed by binding to or encapsulating lipids, sugars, nucleic acids, metals, etc.

[0065] The nucleic acid is not particularly limited and a wide variety of known nucleic acids can be used, including, for example, DNA, RNA, chimeric nucleic acids of DNA and RNA, and DNA / RNA hybrids. The nucleic acid may be complexed by binding to or encapsulating lipids, sugars, polymers, metals, etc.

[0066] The drug (medicine) is not particularly limited, and a wide variety of known drugs can be used, for example, antitumor agents, antihypertensive agents, antihypotensive agents, antipsychotic agents, analgesics, antidepressants, antimanic agents, antianxiety agents, sedatives, hypnotics, antiepileptic agents, opioid agonists, asthma treatment agents, anesthetics, antiarrhythmic agents, arthritis treatment agents, antispasmodics, ACE inhibitors, decongestants, antibiotics, antianginal agents, diuretics, antiparkinsonian agents, bronchodilators, antidiuretics, diuretics, antihyperlipidemic agents, immunosuppressants, immunomodulators, antiemetics, These include those that can act as anti-infective agents, antineoplastic agents, antifungal agents, antiviral agents, antidiabetic agents, antiallergic agents, antipyretics, antigout agents, antihistamines, antipruritics, bone regulating agents, cardiovascular agents, cholesterol-lowering agents, antimalarials, antitussives, expectorants, mucolytics, nasal decongestant agents, dopaminergic agents, gastrointestinal agents, muscle relaxants, neuromuscular blocking agents, parasympathomimetics, prostaglandins, stimulants, appetite suppressants, thyroid or antithyroid agents, hormones, antimigraine agents, anti-obesity agents, and anti-inflammatory agents. The drug may be bound to or encapsulated in a lipid, sugar, polymer, metal, or the like to form a complex.

[0067] The cells are not particularly limited and a wide variety of known cells can be used, including, for example, chondrocytes, osteoblasts, fibroblasts, myoblasts, ligament cells, adipocytes, nerve cells, vascular endothelial cells, smooth muscle cells, cardiac muscle cells, epithelial cells, hepatocytes, pancreatic β cells, kidney cells, bone marrow-derived mesenchymal stem cells, adipose-derived mesenchymal stem cells, neural stem cells, embryonic stem cells, and induced pluripotent stem cells. The cells may be complexed by binding to or encapsulating lipids, sugars, polymers, metals, etc.

[0068] The physiologically active substances used in the present invention may be used alone or in combination of two or more. Furthermore, the physiologically active substances used in the present invention may be synthesized or commercially available products.

[0069] The content of the physiologically active substance in the embolic material of the present invention is not particularly limited, and is, for example, 0.001% by mass to 80% by mass, with the total mass of the embolic material (composition) being 100% by mass.

[0070] Solvent The solvent for the embolic material is preferably an aqueous solution containing mainly water (e.g., pure water, physiological saline). The content of the solvent in the embolic material of the present invention is not particularly limited. From the viewpoint of easily forming an embolism having good strength, the content of the solvent is preferably 30% by mass to 99% by mass, more preferably 70% by mass to 95% by mass, and even more preferably 75% by mass to 90% by mass, where the total mass of the embolic material (composition) is 100% by mass.

[0071] The embolic material may also contain a solvent other than water. The solvent other than water that can be contained in the embolic material of the present invention is not particularly limited as long as it does not impair the effects of the present invention, and examples thereof include oily iodine contrast agents as well as organic solvents such as ethanol, acetone, dimethyl sulfoxide, ethyl lactate, and formamide. When a solvent other than water is contained, its content is not particularly limited, but from the viewpoints of safety and embolization ability, it is preferably 5% by mass or less, and more preferably 0.5% by mass or less, of the total mass of the solvents taken as 100% by mass.

[0072] The solvents that can be used in the present invention can be used alone or in combination of two or more kinds.

[0073] pH The pH of the embolic substance is not particularly limited. From the viewpoint of safety, it is preferably near neutral.

[0074] The embolic material may contain various additives as needed, such as acids, bases, oxidizing agents, reducing agents, stabilizers, pH buffers, preservatives, and surfactants.

[0075] The embolic substance can be preferably used in vascular embolization performed using a medical device such as a catheter, more preferably in vascular embolization in radiological intervention (IR), and even more preferably in vascular embolization for preventing or treating endoleak in radiological intervention (IR) after aortic stent placement, for example.

[0076] As used herein, "embolization" refers to an embolization method, and in particular to a preventive or therapeutic method in which an embolic substance is injected into a blood vessel to block or alter blood flow to a target lesion such as a bleeding point or tumor.

[0077] As used herein, "endoleak" refers to the phenomenon of blood flowing into the space outside a stent placed in an artery (e.g., the aorta). In this case, the aneurysm does not shrink but rather expands, posing a risk of rupture if left untreated. Therefore, endoleak treatment is necessary, but traditionally, embolization of the inflow vessel and endoleak cavity has required the use of large amounts of expensive embolic materials such as NBCA. Furthermore, only a limited number of cases in which embolization has been performed to treat endoleak have shown improvement. On the other hand, the embolic material of the present invention is non-adhesive and can form a flexible and strong gel. Therefore, when the embolic material of the present invention is used in percutaneous embolization to prevent or treat endoleak, it is expected to reduce medical costs and improve long-term outcomes. Furthermore, by filling the embolic material of the present invention during stent insertion, endoleak can be prevented and long-term outcomes can be improved.

[0078] The embolization method (embolization) can be performed by applying a known embolization method for forming a temporary embolization to the embolic substance of the present invention. The embolization method (embolization) can be performed with reference to the embolization method described in Patent Document 1 (Japanese Patent Publication No. 2006-521177).

[0079] The embolization method (embolization) is not particularly limited, but for example, a catheter or needle known in radiotherapy (IR) can be used.

[0080] The embolization method (embolization) using the embolic substance of the present invention can be performed on the blood vessels of mammals, although it is not particularly limited thereto. The mammal may be a human or a non-human mammal. Examples of non-human mammals include dogs, cats, mice, and rats.

[0081] The embolic material of the present invention can easily achieve occlusion immediately after responding to the body temperature of the living body. The time until occlusion is not particularly limited, but can be, for example, more than 0 seconds and less than 1 minute.

[0082] The embolic material of the present invention has good strength, and therefore can maintain the occlusion for a longer period after occluding a blood vessel. The period for which the occlusion is maintained is not particularly limited, but can be, for example, 1 hour to 24 hours. Alternatively, by appropriately selecting the composition, a semi-permanent embolism can be formed.

[0083] The viscosity of the embolic material of the present invention at 20°C is preferably 1,000 mPa·s or less, more preferably 500 mPa·s or less, and even more preferably 300 mPa·s or less, from the viewpoint of being able to pass through a catheter or needle in radiotherapy (IR). On the other hand, the viscosity of the embolic material of the present invention at 37°C is preferably 10,000 mPa·s or more, more preferably 15,000 mPa·s or more, and even more preferably 20,000 mPa·s or more, from the viewpoint of forming an embolism with good strength.

[0084] The storage modulus G' of the embolic material of the present invention at 37°C is preferably 1,000 Pa or more, more preferably 5,000 Pa or more, and even more preferably 10,000 Pa or more, from the viewpoint of forming an embolism with good strength.

[0085] The loss modulus G'' of the embolic material of the present invention at 37°C is preferably 10,000 Pa or less, more preferably 5,000 Pa or less, and even more preferably 1,000 Pa or less, from the viewpoint of forming an embolism with good strength.

[0086] The method for producing the embolic material of the present invention will now be described.

[0087] 2. Method for Producing Embolic Material The method for producing the embolic material of the present invention (hereinafter sometimes simply referred to as the "production method") comprises the step of mixing the temperature-responsive polymer and the nanofibers.

[0088] The mixing ratio of the temperature-responsive polymer and the nanofibers may be set so that the contents of the temperature-responsive polymer and the nanofibers in the embolic material are the amounts described above for the embolic material.

[0089] When mixing the temperature-responsive polymer and nanofibers, they are mixed at a temperature ranging from ice-cold to room temperature depending on their solubility.

[0090] After mixing the temperature-responsive polymer and the nanofibers, it is preferable to stir them by a known stirring method such as stirring with a stirrer, etc. Preferably, the mixing and stirring are carried out in the above-mentioned solvent.

[0091] EXAMPLES The following examples, comparative examples and reference examples will be given to further clarify the features of the present invention, but the present invention is not limited to the following examples.

[0092] The reagents used in the Examples, Comparative Examples and Reference Examples are as follows:

[0093] Temperature-responsive polymers Poloxamer 407 (PL): manufactured by Sigma-Aldrich Nanofibers Cellulose nanofibers (CNF): fiber diameter 30-80 nm, fiber length several hundred μm, manufactured by Cellulose Lab Silk fibroin nanofibers (Silk): fiber diameter 100 nm, fiber length 4-7 μm, manufactured by Nagasuna Mayu Contrast agents Iohexol: manufactured by GE Healthcare Pharma Permanent embolic material (NBCA / Lipiodol solution) n-Butyl cyanoacrylate (NBCA): manufactured by B. Braun Iodized poppy seed oil fatty acid ethyl ester: manufactured by Guerbet Japan Rats Sprague-Dawley (SD) rat, male, 10 weeks old

[0094] Test Example 1: Viscosity and viscoelasticity measurements The temperature dependence of viscosity and viscoelasticity of the embolic material of the present invention was evaluated.

[0095] Figure 1 Example 1: 16 wt% PL + 1 wt% CNF + 53 wt% contrast agent aqueous solution (A and B in Figure 1) Example 2: 16 wt% PL + 2 wt% Silk + 53 wt% contrast agent aqueous solution (C and D in Figure 1)

[0096] The embolic materials of Examples 1 and 2 were obtained by adding PL, CNF, or Silk to a solution prepared by mixing a contrast agent (final concentration 53% by mass; iohexol) with physiological saline, followed by stirring. The contents of PL, CNF, and Silk were adjusted to 16%, 1%, and 2% by mass, respectively, with the total mass of the embolic material (composition) being 100% by mass. Each embolic material was heated using the temperature control module of the rheometer, and the viscosity η, storage modulus G', loss modulus G'', and complex viscosity η were measured. ＊ The measurement was started from 20°C and ended when the temperature reached 40°C. Viscosity η, storage modulus G', loss modulus G'', complex viscosity η ＊ The measurement was carried out using a rheometer (HAAKE Viscotester iQ Air, manufactured by Thermo Fisher Scientific).

[0097] The measurement results of viscosity η are shown in Figures 1A and 2C. It was confirmed that the embolic material (PL-CNF) of Example 1 rapidly gelled at around 26°C, resulting in a sharp increase in viscosity η. It was also confirmed that the embolic material (PL-Silk) of Example 2 rapidly gelled at around 32°C, resulting in a sharp increase in viscosity η. As such, the embolic material of the present invention is a temperature-responsive embolic material; specifically, it is an innovative embolic material that is liquid before injection into a living body and gels after injection into a living body.

[0098] Storage modulus G', loss modulus G'', complex viscosity η ＊ The measurement results are shown in Figures 1B and 1D. The storage modulus G' of the embolic material (PL-CNF) of Example 1 rose sharply from around 26°C and stabilized at 37°C. At that point, G' was sufficiently larger than G'', indicating that the embolic material of the present invention can exist as a gel-like elastic body in vivo. The complex viscosity η, which is a quantity that reflects not only the viscous effect but also the elastic effect, ＊ Similarly, the storage modulus G' of the embolic material (PL-Silk) of Example 2 also rose sharply from around 26°C upon heating, and stabilized at 37°C. In the stable region, G' was significantly larger than G''. Furthermore, the complex viscosity η ＊ increased from around 32°C with heating.

[0099] Example 1: 16% by mass PL + 1% by mass CNF + 53% by mass aqueous solution of contrast agent (A and B in FIG. 2; PL-CNF) Example 2: 16% by mass PL + 2% by mass Silk + 53% by mass aqueous solution of contrast agent (C and D in FIG. 2; PL-Silk) Comparative Example 1: 16% by mass PL + 53% by mass aqueous solution of contrast agent (A to D in FIG. 2; PL)

[0100] The viscosity and viscoelasticity of the embolic material of the present invention were compared with those of the prior art (PL alone). The embolic materials of the present invention were used in Examples 1 and 2 described above. Comparative Example 1 was prepared in the same manner as Examples 1 and 2, except that no nanofibers were added. For each embolic material, the viscosity η at 20°C and 37°C, the storage modulus G', and the loss modulus G'' at 37°C were measured. Each parameter was measured using the same method as in the evaluation of temperature dependency described above.

[0101] The measurement results of viscosity η are shown in Figures 2A and 2C. The viscosity η of the embolic material of the present invention was higher than the viscosity η of the conventional technology at 20°C. At 37°C, the viscosity η of all embolic materials increased, making it impossible to inject them through a catheter. The embolic materials of Examples 1 and 2 exhibited higher viscosities than the conventional technology at both temperatures. These results demonstrate that the embolic material of the present invention has better strength than the conventional embolic material.

[0102] The measurement results of the storage modulus G' and loss modulus G'' are shown in Figures 2B and 2D. The storage modulus G' of the embolic material of the present invention was higher than that of the prior art, indicating that the addition of nanofibers improves the mechanical properties of an embolus made from the embolic material of the present invention as an elastic body. On the other hand, the loss modulus G'' of the embolic material of the present invention was lower than that of the prior art, indicating that the addition of nanofibers significantly changes the elastic properties of an embolus made from the embolic material of the present invention. This tendency was not affected by the type of nanofiber.

[0103] Test Example 2: X-ray fluoroscopy The visibility of the embolic material of the present invention was evaluated.

[0104] Figure 3 Example 1: 16 mass% PL + 1 mass% CNF + 53 mass% contrast agent aqueous solution (left side of Figure 3; PL-CNF (53% contrast agent)) Example 2: 16 mass% PL + 2 mass% Silk + 53 mass% contrast agent aqueous solution (right side of Figure 3; PL-Silk (53% contrast agent)) Example 3: 16 mass% PL + 1 mass% CNF aqueous solution (center of Figure 3; PL-CNF (pure water))

[0105] The visibility of the embolic materials of the present invention under X-ray fluoroscopy was evaluated. The embolic materials of the present invention were the above-mentioned Examples 1, 2, and 3. Example 3 was prepared in the same manner as Example 1, except that it did not contain a contrast agent. Each embolic material was filled into a syringe and observed using an X-ray fluoroscopy device (Siemens Healthineers).

[0106] The observation results of the embolic materials are shown in Figure 3. The embolic material of Example 3 was slightly visible, while the embolic materials of Examples 1 and 2 were clearly visible under X-ray fluoroscopy.

[0107] Test Example 3: Embolization experiment of blood flow circuit using pulsatile flow pump The embolic substance of the present invention was evaluated for its embolization ability in vitro.

[0108] Figure 4 Example 1: 16 mass% PL + 1 mass% CNF + 53 mass% contrast agent aqueous solution (third from the top in Figure 4B) Comparative Example 2: 20 mass% PL + 53 mass% contrast agent aqueous solution (second from the top in Figure 4B) Reference Example 1: 10% NBCA.Lipiodol solution (first from the top in Figure 4B) Reference Example 2: 33% NBCA.Lipiodol solution (fourth from the top in Figure 4B)

[0109] The embolic material of the present invention was the same as that of Example 1. Comparative Example 2 was prepared in the same manner as Comparative Example 1, except that the PL content was 20% by mass. NBCA-Lipiodol solutions containing 10% (Reference Example 1) and 33% (Reference Example 2) NBCA were prepared and used as the conventional technology. An in vitro blood flow circuit was created as shown in the left photograph of Figure 4A. Specifically, a catheter was inserted from a Y connector into an extension tube (lumen: 1 mm) connected to a pulsatile flow pump (manufactured by Fine Biomedical Co., Ltd.). Embolization experiments were performed in the in vitro blood flow circuit by injecting each embolic material through the catheter while flowing serum under conditions similar to those in vivo (120 / 80 mmHg, pulse rate 80 beats / min). Embolization ability was evaluated by the distance (cm) required for embolization of the tube. If embolization was not possible, the distance was infinity. As mentioned above, it was confirmed that the embolic material of the present invention can be injected from a catheter (right photograph in FIG. 4A).

[0110] The results of the tube embolization experiment are shown in Figure 4B. The distance required for embolization (amount of embolic material) was shortest in Reference Example 2, which used high-concentration NBCA, followed by Example 1. Comparative Example 2 and low-concentration NBCA achieved greater distances (amount of embolic material) than Example 1. The embolic material of the present invention was shown to have an embolization effect comparable to that of NBCA, which has been used as a permanent embolic material until now. Furthermore, Example 1 required a smaller amount of embolization than Comparative Example 2, which used a higher amount of PL. This confirmed that the embolization ability improved with increasing content of the temperature-responsive polymer, and further demonstrated that the embolization ability of the embolic material of the present invention was improved by adding nanofibers. Although not shown in Figure 4, Example 2 also demonstrated the same embolization effect as Example 1.

[0111] Test Example 4: Embolization experiment using rats The embolic substance of the present invention was evaluated for its in vivo embolization ability.

[0112] Example 2: 16% by mass PL + 2% by mass Silk + 53% by mass contrast agent aqueous solution

[0113] In vivo embolization experiments were performed on rats. Under general anesthesia, a catheter (1.6 Fr) was inserted into the tail artery (Fig. 5a and b). The right renal artery was embolized, while the left renal artery was left unembolized.

[0114] Representative angiograms of the right renal artery before and after embolization are shown in Figures 5c and 5d. Occlusion of the blood vessel by the embolic material of the present invention was confirmed in vivo in rats under X-ray. Specifically, reflux of contrast medium into the abdominal aorta was observed after embolization. Meanwhile, the right renal artery, which was visible before embolization (Figure 5c), was no longer visible after embolization (Figure 5d). No recanalization was observed at the embolized site after embolization.

[0115] Photographs of the rat kidneys are shown in Figure 5e (embolization group) and Figure 5f (non-embolization group). Discoloration of the renal capsular arteries and neovascularization were confirmed in the kidneys of the embolization group. This suggests that the embolic material of the present invention successfully formed embolism in vivo.

[0116] Test Example 5: Histopathological analysis The kidneys of the rats in Test Example 4 were subjected to histopathological analysis.

[0117] Three days after embolization, the rats were euthanized and histopathological analysis was performed using hematoxylin and eosin (HE) staining and immunohistochemical staining (CD31, F4 / 80). The results of HE staining are shown in Figure 6a. The results of immunostaining are shown in Figure 6b (CD31) and Figure 6c (F4 / 80). The percentages of CD31-positive cells and F4 / 80-positive cells quantified using QuPath are shown in Figure 6d and Figure 6e, respectively. The results of HE staining and immunostaining of the embolization cross-section are shown in Figure 6f.

[0118] The results in Figure 6 show that renal infarction and ischemic acute tubular necrosis (ATN) were observed in the embolization group. It was also found that neovascularization and macrophages were increased in the ATN area. Furthermore, the results in Figure 6f show that emboli were present in CD31-positive blood vessels. These results demonstrate that the embolic material of the present invention is suitable for in vivo embolization, successfully occluded rat renal arteries, and successfully induced infarction and ischemic ATN.

Claims

1. An embolic material containing a temperature-responsive polymer and nanofibers.

2. The embolic material according to claim 1, wherein the temperature-responsive polymer has a lower critical solution temperature (LCST) in the range of 10°C to 40°C.

3. The embolic material described in claim 1 or 2, wherein the temperature-responsive polymer is at least one temperature-responsive polymer selected from the group consisting of poloxamer, poloxamine, poly(N-isopropylacrylamide) and cellulose derivatives.

4. An embolic material according to claim 1 or 2, wherein the content of the temperature-responsive polymer is 10% by mass to 50% by mass, with the total mass of the embolic material being 100% by mass.

5. The embolic material according to claim 1 or 2, wherein the nanofiber is at least one type of nanofiber selected from the group consisting of: at least one type of natural nanofiber selected from the group consisting of cellulose nanocrystals, cellulose nanofibers, bacterial nanocellulose, silk fibroin nanofibers, collagen nanofibers, and gelatin nanofibers; and at least one type of synthetic nanofiber selected from the group consisting of polylactic acid nanofibers, polycaprolactone nanofibers, polyurethane nanofibers, and polylactic acid-glycolic acid copolymer nanofibers.

6. The embolic material described in claim 1 or 2, wherein the temperature-responsive polymer is a poloxamer and the nanofiber is a cellulose nanofiber.

7. The embolic material according to claim 1 or 2, wherein the content of the nanofibers is 0.1% by mass to 10% by mass, with the total mass of the embolic material being 100% by mass.

8. An embolic material according to claim 1 or 2, wherein the content of the nanofibers is 0.2 to 100 parts by mass per 100 parts by mass of the temperature-responsive polymer.

9. The embolic material according to claim 1 or 2, further comprising a contrast agent.

10. The embolic material according to claim 9, wherein the content of the contrast agent is 5% to 70% by mass, with the total mass of the embolic material being 100% by mass.

11. The embolic material according to claim 1 or 2, further comprising a physiologically active substance.

Images