Medical material and method for producing same

Abstract

The present invention relates to: a medical material that is mainly composed of cellulose, has a pore structure having through-holes penetrating in one direction, and has a specific compressive elastic modulus; and a method for producing the medical material.

Description

Medical materials and their manufacturing methods

[0001] The present invention relates to a medical material containing cellulose as a main component and having a porous structure with through-holes that penetrate in one direction, and to a method for producing the same.

[0002] Traditionally, artificial materials such as metals, ceramics, and plastics have been widely used as medical materials. In the field of regenerative medicine, there is a demand for safe medical materials that are compatible with the human body and have properties equivalent to or better than those of components in the body, and the development of medical materials that meet these requirements is desired.

[0003] Here, cartilage is an important tissue that constitutes joints and enables smooth joint movement. However, because cartilage does not regenerate, when cartilage wears down with age, the joint deforms, leading to conditions such as knee osteoarthritis. Treatments for knee osteoarthritis include high tibial osteotomy, which corrects the condition using artificial bone, and total knee arthroplasty, which replaces the joint with a metallic artificial joint, but these do not regenerate cartilage and are not fundamental treatments. Meanwhile, cartilage regeneration treatments typically require the use of stem cells (see, for example, Patent Document 1).

[0004] JP 2013-208211 A

[0005] An object of the present invention is to provide a novel medical material useful as a biocompatible material, and a method for producing the same.

[0006] As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that a medical material containing cellulose as a main component, having a pore structure with through-holes that penetrate in one direction, and having a specific compressive elastic modulus will serve as an excellent medical material, and have thus completed the present invention.

[0007] That is, the present invention is as follows. [1] A medical material containing cellulose as a main component and having a pore structure with through-holes penetrating in one direction, wherein the compressive modulus in a direction perpendicular to the through-holes is 0.0001 to 100 MPa, and the compressive modulus in the direction perpendicular to the through-holes is at least twice the compressive modulus in the direction perpendicular to the through-holes. [2] The medical material according to [1] above, which is a material derived from a woody member of a plant. [3] The medical material according to [1] or [2] above, which contains citric acid. [4] The medical material according to any of [1] to [3] above, which contains N-acetylglucosamine. [5] The medical material according to any of [1] to [4] above, which contains glycosaminoglycan. [6] The medical material according to [5] above, which is characterized in that the glycosaminoglycan is chondroitin sulfate. [7] The medical material according to any of [1] to [6] above, which contains calcium phosphate. [8] The medical material according to any one of [1] to [7] above, which is used for cartilage regeneration.

[0008] [9] A method for producing an elastic material, comprising: a delignification treatment step of delignifying a material derived from a woody member of a plant; and a citric acid treatment step of treating the delignified material with citric acid.

[10] A method for producing an elastic material as described in [9] above, comprising an acetylglucosamine treatment step of treating the citric acid-treated material with N-acetylglucosamine.

[11] A method for producing an elastic material as described in

[10] above, comprising a calcium phosphate treatment step of treating the N-acetylglucosamine-treated material with calcium phosphate.

[12] A method for producing an elastic material as described in

[10] above, comprising a glycosaminoglycan treatment step of treating the N-acetylglucosamine-treated material with glycosaminoglycan.

[13] A method for producing an elastic material as described in

[12] above, wherein the glycosaminoglycan is chondroitin sulfate.

[14] The method for producing an elastic material according to the above

[12] or

[13] , characterized in that it comprises a calcium phosphate treatment step of treating the material treated with glycosaminoglycan with calcium phosphate.

[15] The method for producing an elastic material according to any one of the above [9] to

[14] , characterized in that the produced elastic material is a medical material.

[0009] The present invention can provide a novel medical material that is useful as a biocompatible material.

[0010] Electron microscope (SEM) photographs of the medical materials of Examples 1 to 3. The top row shows a front view of the pores (through-holes), and the bottom row shows a side cross-sectional view of the pores (through-holes). From left to right, they show a CA-treated (citric acid-treated) material, a CA-NAG-treated (citric acid-N-acetylglucosamine-treated) material, and a CA-NAG-CS-treated (citric acid-N-acetylglucosamine-chondroitin sulfate-treated) material. Electron microscope (SEM) photographs of untreated balsa wood and a medical material of Comparative Example 1. The top row shows a front view of the pores (through-holes), and the bottom row shows a side cross-sectional view of the pores (through-holes). From left to right, they show the balsa wood and the delignified material. An electron microscope (SEM) photograph of the medical material of Example 4 (CA-NAG-CaP-treated material) is shown. 7 shows an electron microscope photograph (SEM photograph) of the medical material (CA-NAG-CS-CaP-treated material) of Example 5. It also shows an EDX image (element mapping) of the medical material (CA-NAG-CS-CaP-treated material) of Example 5. It also shows an electron microscope photograph (SEM photograph) of the medical material (Aspen-CA-NAG-treated material) of Example 9. The top row shows a front view of the pores, and the bottom row shows a side cross-sectional view of the pores. It also shows the results of an evaluation of the flexibility of the medical material of Example 2. Fig. 7(A) shows the twisted state, Fig. 7(B) shows the state bent perpendicular to the pore direction, and Fig. 7(C) shows the state bent parallel to the pore direction. It also shows the results of an evaluation of the flexibility of the medical material of Comparative Example 2. Fig. 8(A) shows the twisted state, and Fig. 8(B) shows the state bent parallel to the pore direction. FIG. 1 is a diagram showing the results of a compression test on the medical materials of Examples 1 to 3, showing the compressive modulus when compressed in a direction perpendicular to the through-holes. FIG. 2 is a diagram showing the results of a compression test on the medical materials of Examples 1 to 3, showing the compressive modulus when compressed in the direction of the through-holes. FIG. 3 is a diagram showing the results of a compression test on the medical materials of Examples 1 to 3, showing the stress when the strain (ε) when compressed in a direction perpendicular to the through-holes is 0.9 (when the material is compressed and deformed by 90%). FIG. 4 is a diagram showing the results of a compression test on the medical materials of Examples 1 to 3, showing the compressive strength (strength at break) when compressed in the direction of the through-holes. FIG. 5 is a diagram (photograph) showing the results of a water absorption, expansion, and recovery test on the medical material of Example 2, showing, from the left, the state before compression (A), after compression (B), and after immersion in water (C).1 is a diagram (photograph) showing the results of a water absorption expansion and recovery test for medical materials according to Examples 4 and 5, with the upper row showing the medical material according to Example 4 and the lower row showing the medical material according to Example 5, with (A) the state before compression, (B) the state after compression, and (C) the state after immersion in water, from the left. It is a photograph of the state in which the medical materials according to Examples 2 and 3 were implanted into a cartilage defect, with the upper row showing the state after 4 weeks and the lower row showing the state after 12 weeks, from the left, without implantation, with the medical material according to Example 2 (treated with CA-NAG) implanted, and with the medical material according to Example 3 (treated with CA-NAG-CS) implanted. These are μCT images taken 4 weeks after implantation of the medical materials according to Examples 2 and 3, with the top row being a planar image of the center of the defect and the bottom row being a cross-sectional image of the center of the defect, showing, from left, a state without implantation, a state with the medical material according to Example 2 (treated with CA-NAG) implanted, and a state with the medical material according to Example 3 (treated with CA-NAG-CS). These are μCT images taken 12 weeks after implantation of the medical materials according to Examples 2 and 3, with the top row being a planar image of the center of the defect and the bottom row being a cross-sectional image of the center of the defect, showing, from left, a state without implantation, a state with the medical material according to Example 2 (treated with CA-NAG) implanted, and a state with the medical material according to Example 3 (treated with CA-NAG-CS). 1 shows enlarged images of pathological tissue stained with Safranin O and type II collagen 4 weeks after implantation of the medical materials according to Examples 2 and 3, with the top row being a low-power image, the middle row being a medium-power image, and the bottom row being a high-power image, showing, from left to right, no implantation, implantation of the medical material according to Example 2 (treated with CA-NAG), and implantation of the medical material according to Example 3 (treated with CA-NAG-CS). 1 shows enlarged images of pathological tissue stained with Safranin O and type II collagen 12 weeks after implantation of the medical materials according to Examples 2 and 3, with the top row being a low-power image, the middle row being a medium-power image, and the bottom row being a high-power image, showing, from left to right, no implantation, implantation of the medical material according to Example 2 (treated with CA-NAG), and implantation of the medical material according to Example 3 (treated with CA-NAG-CS). 1 shows enlarged images of pathological tissue stained with Safranin O and stained with type II collagen 4 weeks after implantation of the medical material according to Example 10, from left to right: without implantation (stained with Safranin O), stained with Safranin O, and stained with type II collagen. 1 shows enlarged images of pathological tissue stained with Safranin O 12 weeks after implantation of the medical material according to Example 10, from left to right: without implantation (stained with Safranin O) and stained with Safranin O.FIG. 11 is an enlarged view of the inside of a defect 12 weeks after implantation of the medical material according to Example 10, showing, from the left, an enlarged view of the surface layer of the defect (stained with Safranin O), an enlarged view of the surface layer of the defect (stained with type II collagen), and an enlarged view of the inside of the defect (stained with Safranin O).

[0011] The medical material of the present invention is a medical material containing cellulose as a main component and having a pore structure with through holes that penetrate in one direction, characterized in that the compressive modulus in the direction perpendicular to the through holes is 0.0001 to 100 MPa, and the compressive modulus in the direction of the through holes is at least twice the compressive modulus in the direction perpendicular to the through holes.

[0012] The medical material of the present invention is highly safe for the human body because it is primarily composed of cellulose. It also ensures a high water content. Furthermore, because it has a porous structure with unidirectional through-holes derived from the cellulose, biological cells and tissues can easily penetrate into the pores, promoting the regeneration of damaged tissue and tissue growth. Furthermore, it has a predetermined compressive elastic modulus, is resistant to twisting and bending, and has high elasticity (flexibility), especially in the direction perpendicular to the through-holes.

[0013] The medical material of the present invention can be used, for example, in the medical field or fields related to medical care, as a scaffold for tissue reconstruction or regenerative medicine. Specifically, the medical material of the present invention can be used for cartilage regeneration, muscle regeneration, nerve regeneration, bone regeneration, gingival regeneration, or skin regeneration, and is particularly useful for cartilage regeneration.

[0014] In the medical material of the present invention, the "pore structure having through holes penetrating in one direction" refers to a structure having at least a large number of through holes penetrating in one direction (a structure in which a large number of through holes are present oriented in one direction); for example, wood has through holes penetrating in one direction that originate from vessels. Furthermore, the "pore structure having through holes penetrating in one direction" preferably has, in addition to the through holes, cavities extending in one direction (the same direction as the through holes) that originate from, for example, plant cells, and it is preferable that at least some of these cavities are interconnected. Openings of these through holes and cavities appear on the opposing surfaces of the material in the through hole direction.

[0015] The pore structure having through-holes passing through in one direction according to the present invention may be present in the material as long as the effects of the present invention are achieved. When the medical material of the present invention is a material derived from a woody member of a plant produced using the woody member of a plant, the pore structure having through-holes passing through in one direction is present throughout almost the entire material.

[0016] The woody members of plants of the present invention include wood, bamboo, and woody herbaceous members. Examples include the trunks, branches, roots, and stems of plants. The woody members of plants may be used as they are, or may be used after the cellulose fibers have been partially decomposed, or may be used after the decomposed cellulose fibers have been reattached.

[0017] The diameter of the through-holes is, for example, preferably about 1 to 500 μm, more preferably 10 to 400 μm, and even more preferably 20 to 300 μm. In particular, when used for cartilage regeneration, the diameter is preferably 10 to 500 μm, and more preferably 20 to 300 μm.

[0018] The medical material of the present invention has a pore structure with through holes that penetrate in one direction, and as a result, the compressive modulus varies depending on the compression direction, and the compressive modulus in the direction perpendicular to the through holes is smaller than the compressive modulus in the direction of the through holes.

[0019] The compressive elastic modulus in the direction perpendicular to the through-holes of the medical material of the present invention is 0.0001 to 100 MPa, preferably 0.001 to 30 MPa, more preferably 0.001 to 15 MPa, even more preferably 0.001 to 10 MPa, and particularly preferably 0.1 to 15 MPa.

[0020] For example, when used for regenerating cartilage or muscle, the compressive modulus in the direction perpendicular to the through-holes is preferably 0.001 to 100 MPa, more preferably 0.01 to 10 MPa. In particular, when used as a cartilage regeneration material, since the compressive modulus of cartilage is about 0.2 to 10 MPa, the modulus is preferably 0.1 to 20 MPa, more preferably 0.2 to 10 MPa.

[0021] When used for nerve regeneration, the compressive elastic modulus in the direction perpendicular to the through-hole is preferably 0.0001 to 1 MPa, more preferably 0.0005 to 0.1 MPa.

[0022] When used for bone regeneration, the compressive elastic modulus in the direction perpendicular to the through-holes is preferably 0.01 to 10,000 MPa, more preferably 0.1 to 1,000 MPa.

[0023] The compressive elastic modulus in the through-hole direction is at least 2 times, preferably at least 3 times, more preferably at least 5 times, even more preferably at least 8 times, and particularly preferably at least 10 times, the compressive elastic modulus in the direction perpendicular to the through-holes. Specifically, the compressive elastic modulus in the through-hole direction is, for example, 0.001 to 100,000 MPa, preferably 0.01 to 10,000 MPa, and more preferably 0.1 to 1,000 MPa.

[0024] Furthermore, the medical material of the present invention preferably has a maximum strain (ε) of 0.5 or more, more preferably 0.6 or more, and even more preferably 0.7 or more when compressed in a direction perpendicular to the through-holes. Furthermore, the medical material of the present invention, after such deformation, is preferably restored to a strain (ε) of 0.1 or less, more preferably 0.05 or less, and even more preferably 0.01 or less by immersion in water.

[0025] The medical material of the present invention is a hydroid gel that has absorbed a solvent such as water and swollen inside. The water content of the medical material of the present invention is preferably 50% or more, more preferably 55 to 95%, and even more preferably 60 to 92%. In particular, when used for cartilage regeneration, the water content is preferably 60 to 95%, more preferably 65 to 92%. The water content is calculated from the weight of the medical material of the present invention containing a solvent such as water and the weight of the medical material after being thoroughly dried by freeze-drying or the like.

[0026] The shape of the medical material of the present invention is not particularly limited, and examples thereof include a prism, a cylinder, a sphere, etc. The size (volume) can be appropriately set depending on the application site and application method of the living body, and is, for example, 0.0007 to 500 cm ３ is preferred, and 0.005 to 400 cm３ More preferably, 0.02 to 300 cm ３ is more preferable.

[0027] The medical material of the present invention preferably contains citric acid. Citric acid is a molecule that easily penetrates into the pore structure and easily retains water (having many hydroxyl groups), so it forms hydrogen bonds with the cellulose base material, imparting flexibility to the material. Furthermore, since citric acid is an essential component for living organisms, it can further enhance biocompatibility. Note that taurine, statins, etc. may be used together with or instead of citric acid.

[0028] Furthermore, the medical material of the present invention preferably contains N-acetylglucosamine. N-acetylglucosamine is a polysaccharide similar in structure to cellulose, and it imparts flexibility to the material. It also promotes the production of hyaluronic acid in the body and can retain moisture. Furthermore, when used for cartilage regeneration, it can suppress cartilage degradation and wear, promoting cartilage regeneration.

[0029] The medical material of the present invention preferably contains biological tissue components, such as glycosaminoglycans, collagen, proteins, and amino acids.

[0030] For example, when used for cartilage regeneration, it is preferable to contain a cartilage matrix component or a cartilage regeneration-promoting component, such as chondroitin sulfate (chondroitin sulfate A, chondroitin sulfate C), hyaluronic acid, keratan sulfate, collagen, statin, etc.

[0031] Furthermore, the medical material of the present invention preferably contains calcium phosphate. By containing calcium phosphate, binding to bone can be improved. The calcium phosphate is not particularly limited as long as it contains phosphoric acid and calcium, and examples thereof include carbonate apatite, hydroxyapatite, β-tricalcium phosphate, α-tricalcium phosphate, octacalcium phosphate, calcium hydrogen phosphate, apatites in which a part of the apatite is substituted with a halogen, such as chlorapatite, tricalcium phosphate in which a part of the tricalcium phosphate is substituted with magnesium, such as whitlockite, and amorphous calcium phosphate.

[0032] Furthermore, the medical material of the present invention preferably does not contain lignin, which ensures the excellent elasticity of the medical material of the present invention.

[0033] The medical material of the present invention is particularly suitable for use in cartilage regeneration. By implanting the medical material of the present invention into a damaged area of ​​cartilage so that the pore structure with unidirectional through-holes is aligned with the orientation direction of the cartilage, chondrocytes and cartilage tissue can easily infiltrate into the pores, promoting the regeneration and growth of cartilage tissue. Furthermore, the medical material of the present invention can ensure elasticity equivalent to or greater than that of cartilage. In other words, the medical material of the present invention is capable of cartilage regeneration using the material alone, enabling cartilage regeneration to be achieved in a minimally invasive and low-cost manner.

[0034] Next, a method for producing an elastic material of the present invention will be described. Here, an elastic material is a material that has the property of returning to its original shape when deformation caused by an external force is removed, and it is sufficient that the deformation returns to its original shape only partially, or not completely. The elastic material produced by the production method of the present invention has excellent elasticity, particularly in the direction perpendicular to the through-holes.

[0035] The method for producing an elastic material of the present invention is characterized by comprising a delignification step of delignifying a material derived from a woody member of a plant, and a citric acid treatment step of treating the delignified material with citric acid. Note that the material derived from a woody member of a plant used in the production method of the present invention may hereinafter be referred to as a wood-derived material.

[0036] The manufacturing method of the present invention can be used to manufacture elastic materials, such as the above-mentioned medical material of the present invention. Note that the plant wood-derived materials, citric acid, N-acetylglucosamine, glycosaminoglycans, calcium phosphate, and the like used in the manufacturing method of the present invention are the same as those described in the above-mentioned present invention, and therefore detailed description thereof will be omitted.

[0037] Each step will be described below. (Delignification step) The delignification step is a step of removing lignin from materials derived from woody members of plants. The delignification step is not particularly limited, and conventionally known methods can be used. Examples include a method using sodium chlorite and acetic acid (the Wise method), a peracetic acid method, a hydrogen peroxide method, and a hydrogen fluoride method. Specifically, for example, lignin can be removed by immersing the wood-derived material in a solution of sodium chlorite and acetic acid and then washing it. When using wood-derived materials with a large volume, a vacuum treatment (vacuum degassing treatment) may be performed as needed to allow the solution to penetrate into the material.

[0038] (Citric Acid Treatment Step) The citric acid treatment step is a step in which the material delignified in the delignification treatment step is treated with citric acid. This step can impart flexibility to the material. The citric acid treatment is not particularly limited, and an example thereof can be a method in which the delignified material is immersed in a citric acid solution and subjected to a vacuum treatment to allow the citric acid to penetrate the material. If necessary, freezing and thawing may be performed after immersion in the citric acid solution. The concentration of the citric acid solution is preferably about 0.01 g / ml to 10.0 g / ml, and more preferably 0.1 g / ml to 5.0 g / ml.

[0039] (Acetylglucosamine Treatment Step) The acetylglucosamine treatment step is a step in which the material treated with citric acid is treated with N-acetylglucosamine. This step can impart greater flexibility to the material. The N-acetylglucosamine treatment is not particularly limited, and an example is a method in which the citric acid-treated material is immersed in an N-acetylglucosamine solution and subjected to vacuum treatment to allow the N-acetylglucosamine to penetrate into the material. If necessary, freezing and thawing may be performed after immersion in the N-acetylglucosamine solution. The concentration of the N-acetylglucosamine solution is preferably about 0.001 g / ml to 1.0 g / ml, and more preferably 0.01 g / ml to 0.5 g / ml.

[0040] (Glycosaminoglycan Treatment Step) The glycosaminoglycan treatment step is preferably a step of treating a material treated with N-acetylglucosamine with glycosaminoglycan. This step introduces glycosaminoglycans, such as chondroitin sulfate (chondroitin sulfate A, chondroitin sulfate C), hyaluronic acid, and keratan sulfate, which are components of biological tissue, thereby improving affinity with biological tissue. Examples of glycosaminoglycan treatment include immersing an acetylglucosamine-treated material in a glycosaminoglycan solution and subjecting it to vacuum treatment to allow the glycosaminoglycan to penetrate the material. If necessary, freezing and thawing may be performed after immersion in the glycosaminoglycan solution. This step can also be performed on a citric acid-treated material. The concentration of the glycosaminoglycan solution is preferably about 0.00001 g / ml to 1.0 g / ml, more preferably about 0.00001 g / ml to 0.8 g / ml, and even more preferably about 0.00005 g / ml to 0.5 g / ml.

[0041] (Calcium phosphate treatment step) The calcium phosphate treatment step is preferably a step of treating an N-acetylglucosamine-treated material or a glycosaminoglycan-treated material with calcium phosphate. This step allows calcium phosphate to precipitate on the surface of the material, thereby improving bone bonding. There are no particular limitations on the calcium phosphate treatment, and a conventionally known method can be used. For example, a glycosaminoglycan-treated material can be treated with PO ４ ３－ After immersion in a solution containing Ca ２＋ This step can be carried out by repeatedly immersing the material in a solution containing citric acid.

[0042] P.O. ４ ３－ Examples of the solution containing Ca include solutions of phosphoric acid, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, tripotassium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, triammonium phosphate, diammonium hydrogen phosphate, and ammonium dihydrogen phosphate. ２＋ Examples of the solution containing calcium chloride, calcium nitrate, calcium acetate, calcium lactate, calcium hydroxide, calcium bicarbonate, etc. can be mentioned.

[0043] The present invention will be described in detail below with reference to examples, but the technical scope of the present invention is not limited to these examples. Medical materials according to the examples and comparative examples of the present invention were produced as follows.

[0044] [Example 1] (Delignification treatment) NaClO ２ A 30 x 30 x 5 mm piece of balsa wood was added to a solution of 19.2 g of chlorine and 6.4 g of acetic acid dissolved in 960 mL of distilled water, and the mixture was left to stand at 60°C for three days. During this time, the solution was replaced (approximately twice a day) when the color of the solution turned yellow. After three days, the wood was removed, washed with running distilled water, and then immersed in distilled water. The distilled water was replaced every three hours, for a total of five times. After washing, white wood was obtained.

[0045] (Citric Acid Treatment) The delignified white wood was immersed in a 2 mol / L citric acid solution prepared by dissolving 120 g of citric acid in 300 mL of water. After immersion, the wood was vacuum degassed three times for 15 minutes each, and then frozen overnight at -20°C. After freezing, the wood was thawed at 4°C for 24 hours to produce the medical material (CA-treated material) according to Example 1.

[0046] Example 2 (Acetylglucosamine Treatment) The CA-treated material obtained in the same manner as in Example 1 was immersed in an acetylglucosamine solution prepared by dissolving 8.84 g of N-acetylglucosamine in 200 mL of water. After immersion, the material was vacuum degassed three times for 15 minutes each, and then frozen overnight at -20°C. After freezing, the material was thawed at 4°C over 24 hours to produce the medical material of Example 2 (CA-NAG-treated material).

[0047] [Example 3] (Glycosaminoglycan Treatment) The CA-NAG-treated material obtained in the same manner as in Example 2 was immersed in a 0.05 g / L chondroitin sulfate solution prepared by dissolving 5 g of chondroitin sulfate in 100 mL of water. After immersion, vacuum degassing was performed three times for 15 minutes to produce the hydrogel of Example 3 (CA-NAG-CS-treated material).

[0048] [Example 4] (Calcium phosphate treatment) The CA-NAG-treated material obtained in the same manner as in Example 2 was subjected to the following treatment: (1) K ２ HPO ４ 15.7 g of 300 mmol / L of K was dissolved in 300 mL of water. ２ HPO ４ (2) immersion in distilled water for 10 seconds; (3) immersion in CaCl ２ 500 mmol / L CaCl was prepared by dissolving 16.7 g of CaCl in 300 mL of water. ２ (4) immersing in distilled water for 10 seconds; (5) repeating steps (1) to (4) five times to produce the hydrogel of Example 4 (CA-NAG-CaP-treated material).

[0049] [Example 5] The hydrogel of Example 5 (CA-NAG-CS-CaP-treated material) was produced in the same manner as in Example 4, except that the CA-NAG-treated material obtained in the same manner as in Example 2 was changed to a CA-NAG-CS-treated material obtained in the same manner as in Example 3.

[0050] Example 6 A hydrogel (CA-NAG-0CS-treated material) according to Example 6 was produced in the same manner as in Example 3, except that the 0.05 g / L chondroitin sulfate solution was replaced with distilled water (0 g / mL chondroitin sulfate solution). Note that a different balsa wood from that used in Example 3 was used.

[0051] Example 7 A hydrogel according to Example 6 (CA-NAG-0.05CS-treated material) was produced in the same manner as in Example 6, except that distilled water was replaced with a 0.05 g / mL chondroitin sulfate solution.

[0052] Example 8 A hydrogel (CA-NAG-0.25CS-treated material) according to Example 8 was produced in the same manner as in Example 6, except that distilled water was replaced with a 0.25 g / mL chondroitin sulfate solution.

[0053] Example 9 A medical material according to Example 9 (aspen-CA-NAG treated material) was produced in the same manner as in Example 2, except that the balsa wood was changed to aspen wood.

[0054] Example 10 A hydrogel according to Example 10 (aspen-CA-NAG-0.05CS-treated material) was produced in the same manner as in Example 3, except that the balsa wood was changed to aspen wood.

[0055] Example 11 A hydrogel (aspen-CA-NAG-0.1CS-treated material) according to Example 11 was produced in the same manner as in Example 3, except that the balsa wood was changed to aspen wood and the 0.05 g / L chondroitin sulfate solution was changed to a 0.1 g / L chondroitin sulfate solution.

[0056] Comparative Example 1 A medical material (delignified material) according to Comparative Example 1 was produced in the same manner as in Example 1, except that the citric acid treatment was not carried out.

[0057] Comparative Example 2 A medical material according to Comparative Example 2 (delignified-NAG treated material) was produced in the same manner as in Example 2, except that the CA treated material obtained in the same manner as in Example 1 was replaced with a delignified material obtained in the same manner as in Comparative Example 1 (the citric acid treatment was omitted).

[0058] <Evaluation> Various evaluations were performed on the medical materials according to the Examples and Comparative Examples. (SEM Observation) Figure 1 shows electron microscope photographs (SEM photographs) of the medical materials according to Examples 1 to 3, with the top row showing a front view of the pores and the bottom row showing a side cross-sectional view of the pores, from left to right showing the CA-treated material, the CA-NAG-treated material, and the CA-NAG-CS-treated material. Figure 2 shows electron microscope photographs (SEM photographs) of untreated balsa wood and the medical material according to Comparative Example 1, with the top row showing a front view of the pores and the bottom row showing a side cross-sectional view of the pores, from left to right showing the balsa wood and the delignified material.

[0059] 1 and 2, it can be seen that the pore structure of untreated balsa wood is maintained in the medical materials of Examples 1 to 3. Furthermore, it was confirmed that the pore inner walls of the CA-NAG-CS-treated material were modified with chondroitin sulfate (upper arrowhead in Figure 1).

[0060] Fig. 3 shows an electron microscope photograph (SEM photograph) of the medical material (CA-NAG-CaP-treated material) according to Example 4, and Fig. 4 shows an electron microscope photograph (SEM photograph) of the medical material (CA-NAG-CS-CaP-treated material) according to Example 5. Also, Fig. 5 shows an EDX image (element mapping) of the medical material (CA-NAG-CS-CaP-treated material) according to Example 5.

[0061] As shown in FIGS. 3 to 5, it was confirmed that the inner walls of the pores of the medical materials according to Examples 4 and 5 were modified with calcium phosphate.

[0062] FIG. 6 is an electron microscope (SEM) photograph of the medical material (aspen-CA-NAG treated material) according to Example 9, in which the upper photograph shows a front view of the pores and the lower photograph shows a side cross-sectional view of the pores.

[0063] As shown in FIG. 6, it can be seen that the medical material according to Example 9 retains the pore structure of aspen.

[0064] (Confirmation of Flexibility) The flexibility of the medical materials according to Examples 1 to 5 was confirmed. Specifically, the flexibility of the medical materials according to Examples 1 to 5 was confirmed by twisting and bending them by hand. FIG. 7 shows the results of the evaluation of the flexibility of the medical material according to Example 2. FIG. 7(A) shows the twisted state, FIG. 7(B) shows the state bent perpendicular to the pore direction, and FIG. 7(C) shows the state bent parallel to the pore direction. FIG. 8 also shows the results of the evaluation of the flexibility of the medical material according to Comparative Example 2. FIG. 8(A) shows the twisted state, and FIG. 8(B) shows the state bent parallel to the pore direction.

[0065] As shown in Figure 7, the medical material of Example 2 could be flexibly twisted and bent perpendicularly or parallel to the pore direction. No cracks or breaks were observed. The medical material of Example 1 was slightly stiff, but could be twisted and bent perpendicularly to the pore direction. The medical materials of Examples 3 to 5 were similar to the medical material of Example 2. On the other hand, as shown in Figure 8, the medical material of Comparative Example 2 cracked when twisted and broke when bent perpendicularly to the pore direction.

[0066] (Compression Test) Compression tests were conducted on the medical materials according to Examples 1 to 3. The results of the compression tests are shown in Figures 9 to 12. Figure 9 shows the compressive modulus when compressed in a direction perpendicular to the through-holes. Figure 10 shows the compressive modulus when compressed in the direction of the through-holes. Figure 11 shows the stress when the strain (ε) when compressed in a direction perpendicular to the through-holes is 0.9 (when the material is compressed and deformed by 90%). Figure 12 shows the compressive strength (strength at break) when compressed in the direction of the through-holes.

[0067] As shown in Figure 9, when compressed in a direction perpendicular to the through holes, the medical materials of Examples 1 to 3 exhibited a compressive modulus of elasticity equivalent to the elastic modulus of cartilage, which is 0.2 to 0.9 MPa. Furthermore, as shown in Figure 10, the compressive modulus when compressed in the direction of the through holes was greater than the compressive modulus in the direction perpendicular to the through holes. Furthermore, as shown in Figures 11 and 12, it was confirmed that the medical materials of Examples 1 to 3 have sufficient strength to withstand a load of 0.5 to 0.7 MPa applied to human cartilage.

[0068] ((Effect of Chondroitin Sulfate Amount)) In order to investigate the effect of chondroitin sulfate amount on physical properties, a compression test was conducted on the medical materials of Examples 6 to 8. The compressive moduli were measured when the medical materials of Examples 6 to 8, which had different chondroitin sulfate amounts, were compressed in the direction of the through-holes. The compressive moduli of the medical material of Example 6 (0 g / mL chondroitin sulfate) was 7.2±4.0 MPa, the compressive moduli of the medical material of Example 7 (0.05 g / mL chondroitin sulfate) was 8.2±3.0 MPa, and the compressive moduli of the medical material of Example 8 (0.25 g / mL chondroitin sulfate) was 12.1±3.2 MPa, confirming that the compressive moduli increased as the chondroitin sulfate amount increased.

[0069] Next, the stress was measured when the strain (ε) was 0.9 (when the material was compressed 90% deformed) when the medical materials of Examples 6 to 8 were compressed in the direction of the through-holes. The stress of the medical material of Example 6 (chondroitin sulfate 0 g / mL) was 0.60±0.19 MPa, the stress of the medical material of Example 7 (chondroitin sulfate 0.05 g / mL) was 1.47±0.47 MPa, and the stress of the medical material of Example 8 (chondroitin sulfate 0.25 g / mL) was 2.60±0.60 MPa, confirming that the compressive strength increased as the amount of chondroitin sulfate increased.

[0070] ((Effect of Wood Type)) In order to examine the effect of wood type on physical properties, compression tests were carried out on the medical materials of Examples 9 to 11 using aspen wood.

[0071] The compressive moduli were measured when compressed in a direction perpendicular to the through-holes of the medical materials of Examples 9 to 11. The compressive moduli of the medical material of Example 9 (Aspen-CA-NAG-treated material) was 12.1 MPa, the compressive moduli of the medical material of Example 10 (Aspen-CA-NAG-0.05CS-treated material) was 6.7 MPa, and the compressive moduli of the medical material of Example 11 (Aspen-CA-NAG-0.1CS-treated material) was 8.1 MPa.

[0072] It was confirmed that the compressive modulus increased by changing the type of wood from balsa to aspen. It was also confirmed that the compressive modulus increased as the amount of chondroitin sulfate increased in the case of aspen. The compressive modulus of the medical material of Example 10, when compressed in the direction of the through-holes, was 194.8 MPa, which was larger than the compressive modulus in the direction perpendicular to the through-holes.

[0073] Next, the stress was measured when the strain (ε) was 0.9 (when the material was compressed to 90% deformation) when the medical materials of Examples 9 to 11 were compressed in a direction perpendicular to the through-holes. The stress of the medical material of Example 9 (Aspen-CA-NAG-treated material) was 23.8 MPa, the stress of the medical material of Example 10 (Aspen-CA-NAG-0.05CS-treated material) was 71.4 MPa, and the stress of the medical material of Example 11 (Aspen-CA-NAG-0.1CS-treated material) was 148.0 MPa.

[0074] It was confirmed that the compressive strength increased when the wood type was changed from balsa to aspen. In addition, it was confirmed that the compressive strength of aspen also increased as the amount of chondroitin sulfate increased.

[0075] The compressive strength (strength at break) of the medical material of Example 10 when compressed in the direction of the through-hole was 31.9±13.3 MPa.

[0076] (Moisture Content Measurement Test) A moisture content measurement test was conducted on the medical materials of Examples 1 to 5. The moisture content was calculated from the weight change of the hydrated gel-like material of each Example and the gel-like material when freeze-dried. Fig. 13 shows the results of the moisture content measurement test on the medical materials of Examples 1 to 5.

[0077] 13, the water content of the medical materials according to Examples 1 to 5 was 75 to 90%, which was equal to or higher than the water content of cartilage, which has a water content of about 60 to 85%.

[0078] (Water absorption expansion and recovery test) A water absorption expansion and recovery test was carried out on the medical materials according to Examples 2, 4 and 5. The measurement was carried out by compressing the material at 5 MPa and then immersing it in water for 10 minutes, and measuring the thickness of the material.

[0079] Fig. 14 is a diagram (photograph) showing the results of a water absorption expansion and recovery test of the medical material of Example 2, showing, from the left, (A) the state before compression, (B) the state after compression, and (C) the state after immersion in water. As shown in Fig. 14, the thickness before compression was 5.23 mm, the thickness when the load was removed after compression was 1.58 mm (the thickness immediately after compression was 0.26 mm), and the thickness after immersion in water for 10 minutes was 5.23 mm, indicating that the material recovered to the size before compression.

[0080] Figure 15 is a diagram (photograph) showing the results of the water absorption expansion and recovery test for the medical materials of Examples 4 and 5. The top row shows the medical material of Example 4, and the bottom row shows the medical material of Example 5. From left to right, the states are shown as follows: (A) before compression, (B) after compression, and (C) after immersion in water. As shown in Figure 15, the medical material of Example 4 had a thickness of 5.21 mm before compression, a thickness of 2.30 mm after compression and removal of the load, and a thickness of 5.21 mm after removal of the load and immersion in water for 10 minutes. The medical material of Example 5 had a thickness of 5.23 mm before compression, a thickness of 1.49 mm after compression and removal of the load, and a thickness of 5.23 mm after removal of the load and immersion in water for 10 minutes. This demonstrates that the medical materials of Examples 4 and 5 recovered to their pre-compression sizes.

[0081] (Animal Test) ((Example using balsa wood)) A recessed defect measuring 1.5 mm in diameter and 3 mm deep was created in the cartilage of a rabbit, and the medical materials of Examples 2 and 3 were embedded in this recessed defect so that the direction of the through-holes was the same as the orientation of the cartilage. After 4 and 12 weeks of embedding, the material was excised en bloc with the surrounding tissue, and pathological tissue sections were prepared and stained with Safranin O and type II collagen.

[0082] Figure 16 shows photographs of the state of implantation of the medical materials of Examples 2 and 3 into cartilage defects. The upper row in Figure 16 is a photograph taken 4 weeks later, and the lower row is a photograph taken 12 weeks later, showing, from left to right, no implantation, a state where the medical material of Example 2 (treated with CA-NAG) was implanted, and a state where the medical material of Example 3 (treated with CA-NAG-CS) was implanted.

[0083] As shown in Figure 16, it was confirmed that cartilage-like white tissue had regenerated in the medical material of Example 3 (treated with CA-NAG-CS) four weeks after implantation. Furthermore, it was confirmed that cartilage-like white tissue had regenerated in both the medical material of Example 2 (treated with CA-NAG) and the medical material of Example 3 (treated with CA-NAG-CS) 12 weeks after implantation. On the other hand, without implantation, cartilage damage was confirmed after four weeks, and cartilage deformation was confirmed after 12 weeks. It was found that the medical material of the present invention can suppress cartilage damage when implanted in a cartilage defect site.

[0084] Here, Figure 17 shows μCT images taken 4 weeks after implantation of the medical materials according to Examples 2 and 3. In Figure 17, the upper row shows a planar image of the center of the defect, and the lower row shows a cross-sectional image of the center of the defect. From the left, the images show no implantation, implantation of the medical material according to Example 2 (treated with CA-NAG), and implantation of the medical material according to Example 3 (treated with CA-NAG-CS). The scale bar in each figure in Figure 17 is 3.5 mm. Figure 18 shows μCT images taken 12 weeks later.

[0085] 19 shows magnified images of pathological tissue stained with Safranin O and type II collagen four weeks after implantation of the medical materials according to Examples 2 and 3. In Fig. 19, the upper row is a low-power image, the middle row is a medium-power image, and the lower row is a high-power image, showing, from left to right, no implantation, implantation of the medical material according to Example 2 (treated with CA-NAG), and implantation of the medical material according to Example 3 (treated with CA-NAG-CS). Fig. 20 shows magnified images of the stained pathological tissue after 12 weeks.

[0086] 17 and 18, it was confirmed that cartilage was maintained (the material prevented damage) in the medical materials of Examples 2 and 3 4 and 12 weeks after implantation. On the other hand, it was confirmed that cartilage was damaged and lost in the case without implantation.

[0087] 19 and 20 , when no material was implanted, fibrous tissue filled the defect at 4 weeks, and adipose tissue filled the defect at 12 weeks. When the medical material of Example 2 was implanted, cartilage was confirmed to have formed at the edge of the material. When the medical material of Example 3 was implanted, cartilage was confirmed to have formed at the edge of the material at 4 weeks, and cartilage was confirmed to have formed throughout the material at 12 weeks.

[0088] ((Example using aspen material)) A recessed defect measuring 1.5 mm in diameter and 3 mm deep was formed in rabbit cartilage, and the medical material of Example 10 was embedded in this recessed defect so that the direction of the through-holes was the same as the orientation of the cartilage. After 4 and 12 weeks of embedding, the material was excised en bloc with the surrounding tissue, and pathological tissue sections were prepared and stained with Safranin O and type II collagen.

[0089] FIG. 21 shows enlarged images of pathological tissue stained with Safranin O and stained with type II collagen four weeks after implantation of the medical material according to Example 10 (Aspen-CA-NAG-0.05CS-treated material). From the left, FIG. 21 shows, without implantation, Safranin O staining, and type II collagen staining. FIG. 22 shows enlarged images of pathological tissue stained with Safranin O 12 weeks after implantation of the medical material according to Example 10, from the left, without implantation and Safranin O staining. FIG. 23 shows an enlarged view of the interior of the defect 12 weeks after implantation of the medical material according to Example 10. From the left, FIG. 23 shows an enlarged view of the surface layer of the defect (stained with Safranin O), an enlarged view of the surface layer of the defect (stained with type II collagen), and an enlarged view of the interior of the defect.

[0090] As shown in Figure 21, cartilage was confirmed to have formed at the edge of the material at 4 weeks. Furthermore, as shown in Figures 22 and 23, cartilage had formed throughout the material at 12 weeks, and repair of the cartilage and subchondral bone was observed at the surface of the defect, confirming that the medical material had been absorbed and was in contact with the bone.

[0091] The medical material of the present invention is industrially useful because it can be used in the medical field or fields related to medical care, such as in tissue reconstruction procedures for cartilage and the like, and as scaffolds in regenerative medicine.

Claims

1. A medical material whose main component is cellulose and has a porous structure with through-holes that penetrate in one direction, characterized in that the compressive modulus in the direction perpendicular to the through-holes is 0.0001 to 100 MPa, and the compressive modulus in the direction of the through-holes is at least twice the compressive modulus in the direction perpendicular to the through-holes.

2. The medical material according to claim 1, characterized in that it is a material derived from a woody member of a plant.

3. The medical material according to claim 1, which contains citric acid.

4. The medical material according to claim 1, characterized in that it contains N-acetylglucosamine.

5. The medical material according to claim 1, characterized in that it contains glycosaminoglycan.

6. The medical material according to claim 5, wherein the glycosaminoglycan is chondroitin sulfate.

7. The medical material according to claim 3, which contains N-acetylglucosamine.

8. The medical material according to claim 7, which contains glycosaminoglycan.

9. The medical material according to claim 1, which contains calcium phosphate.

10. The medical material according to any one of claims 1 to 9, which is used for cartilage regeneration.

11. A method for producing an elastic material, comprising: a delignification step of delignifying a material derived from a woody member of a plant; and a citric acid treatment step of treating the delignified material with citric acid.

12. The method for producing an elastic material according to claim 11, further comprising an acetylglucosamine treatment step of treating the citric acid-treated material with N-acetylglucosamine.

13. The method for producing an elastic material according to claim 12, further comprising a calcium phosphate treatment step of treating the material treated with N-acetylglucosamine with calcium phosphate.

14. The method for producing an elastic material according to claim 12, further comprising a glycosaminoglycan treatment step of treating the material treated with N-acetylglucosamine with glycosaminoglycan.

15. The method for producing an elastic material according to claim 14, wherein said glycosaminoglycan is chondroitin sulfate.

16. The method for producing an elastic material according to claim 14, further comprising a calcium phosphate treatment step of treating the material treated with glycosaminoglycan with calcium phosphate.

17. The method for producing an elastic material according to any one of claims 11 to 16, wherein the elastic material produced is a medical material.

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