Fiber sheet structure including a doubling bundle of gelatin fiber bundles and thermoplastic resin fiber bundles

Abstract

[Problem] A purpose of the present invention is to provide a fiber sheet structure that includes a multiple wound yarn bundle formed of a thermoplastic resin fiber bundle and a gelatin fiber bundle, and that has a preferable texture, a high tensile strength, and a great rupture elongation as compared to conventional gelatin fibers.　Another purpose of the present invention is to provide a fiber sheet structure that includes a multiple wound yarn bundle formed of a thermoplastic resin fiber bundle and a gelatin fiber bundle, and that has excellent cell adhesiveness for fixing cells thereto and has slipperiness for making inflammation unlikely to occur when a biological tissue is rubbed against the same. [Solution] This fiber sheet structure includes a knit structure and has a cell placement surface and a back surface. The average pore size of the back surface is less than the average pore size of the cell placement surface. The knit structure includes a multiple wound yarn bundle formed of a gelatin fiber bundle and a thermoplastic resin fiber bundle. The thickness of the fiber sheet structure is 30-5000 μm. The number of gelatin fibers forming the gelatin fiber bundle is 5-60. The fineness of the gelatin fibers is 0.5-10 dtex. The total number of the thermoplastic resin fiber bundle and the gelatin fiber bundle in the multiple wound yarn bundle is 2-20. The ratio of the numbers of the gelatin fiber bundle and the thermoplastic resin fiber bundle in the multiple wound yarn bundle is 5:1 to 1:5.

Description

[Technical Field]

[0001] The present invention relates to a fiber sheet structure including a doubling bundle made of gelatin fiber bundles and thermoplastic resin fiber bundles. [Background technology]

[0002] Gelatin is a denatured collagen obtained by treating triple helical collagen molecules from bovine bone, bovine hide, pigskin, etc. with acid or alkali followed by extraction with boiling water. Its low antigenicity and rapid bioabsorption compared to conventional bioabsorbable materials are advantageously utilized as a bioabsorbable material. Traditionally, gelatin has been available in powder, sheet, or sponge form and has been primarily used in food ingredients, photographic emulsions, and pharmaceutical capsules. Recently, gelatin's excellent biocompatibility (low antigenicity and high bioabsorbability) has attracted attention, leading to promising applications in medical materials such as wound and burn treatments and artificial skin matrices. In vivo, cells function through three-dimensional interactions. Furthermore, when considering scaffolds for in vitro 3D cell culture, 3D cell culture is one method for mimicking the living body in vitro, and highly structured structures are desirable. From the above perspectives, it is desirable to fabricate higher-order structures such as woven fabrics, knitted fabrics, and braided cords using long fibers (filament yarns) that have high strength and elongation at break for use in medical applications and as scaffolds for cell culture.

[0003] For example, Patent Document 1 proposes extruding an aqueous solution containing gelatin and a water-soluble linear polymer such as polyethylene glycol into air and spinning it. Patent Document 2 proposes a method for producing gelatin fibers in which a gelatin solution is discharged into a coagulation bath to form gel-like fibers, which are then removed and stretched, and the remaining solution is removed. Patent Document 3 proposes heating an aqueous gelatin solution to form a sol, spinning it in air, and then immersing it in a crosslinking agent solution to crosslink it. Patent Document 4 proposes a method for producing gelatin fibers in which a gelatin solution containing a solution containing an amide compound and a halogen salt of an alkali metal or alkaline earth metal is extruded into an alcohol solution by wet spinning to coagulate gelatin fibers, and then washing out added components such as the crosslinking agent.

[0004] When higher-order structures such as woven fabrics, knitted fabrics, and braided cords that have high strength and elongation at break are used as medical materials, it is necessary to allow cells to settle and proliferate on these higher-order structures. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-167397 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-120527 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-163204 [Patent Document 4] Japanese Patent Application Laid-Open No. 2001-89929 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the long fibers (filament yarns) made of gelatin fibers obtained by the above-mentioned conventional techniques were difficult to unwind after winding, making it impossible to obtain filament yarns. Also, gelatin fibers produced through a process to reduce the toxicity of additives such as crosslinking agents by washing them out had low tensile strength and breaking elongation, making it difficult to obtain higher-order structures such as knitted fabrics, woven fabrics, and braided cords.

[0007] Furthermore, gelatin generally has low cell adhesion, making it difficult to attach cells and culture them in a short period of time. On the other hand, collagen has high cell adhesion, but is degraded only by specific enzymes, resulting in a long degradation time in the body. Furthermore, when used as a wound or burn treatment material or as a matrix material for artificial skin, it is necessary for it to have slipperiness and moderate strength to prevent inflammation when rubbed against biological tissue. While gelatin sponges and gelatin sheets have excellent slipperiness, they have the problem of low strength. Higher-order structures made of thermoplastic fibers have sufficient strength to withstand sliding, but they have issues such as poor slipperiness, which can cause inflammation when rubbed against biological tissue, or inflammation caused by the acid produced by the decomposition of thermoplastic fibers.

[0008] Therefore, an object of the present invention is to provide a fiber sheet structure including a doubled yarn bundle made of gelatin fiber bundles and thermoplastic resin fiber bundles, which has a better texture, higher tensile strength, and greater breaking elongation than conventional gelatin fibers.

[0009] Furthermore, the present invention aims to provide a fiber sheet structure including a double-yarn bundle made of gelatin fiber bundles and thermoplastic resin fiber bundles, which have excellent cell adhesive properties for fixing cells and slip properties that make it less likely to cause inflammation when rubbed against biological tissue. [Means for solving the problem]

[0010] Specific means for achieving the above object include the following aspects. (First mode) <<Aspect 1>> A higher-order structure containing gelatin fiber bundles. <<Aspect 2>> The high-order structure according to aspect 1, wherein the gelatin fiber bundles have a tensile strength of 0.5 to 3.0 cN / dtex and a breaking elongation of 30 to 300%. Aspect 3 3. The higher-order structure according to aspect 1 or 2, wherein the swelling ratio of the gelatin fiber bundle when immersed in phosphate buffered saline at 50° C. for 4 hours is 110 to 350%. Aspect 4 The higher-order structural body according to any one of Aspects 1 to 3, wherein the higher-order structural body further comprises thermoplastic resin fiber bundles, and the gelatin fiber bundles and the thermoplastic resin fiber bundles are combined into a ply bundle. Aspect 5 A higher-order structure according to aspect 4, wherein the doubling yarn bundle has a tensile strength of 1.0 to 10.0 cN / dtex and a breaking elongation of 20 to 250%. Aspect 6 6. The higher-order structure according to aspect 4 or 5, wherein the swelling ratio of the doubly-woven yarn bundle when immersed in phosphate buffered saline at 50° C. for 4 hours is 110 to 350%. Aspect 7 7. The higher-order structure according to any one of aspects 1 to 6, wherein the higher-order structure has a weight loss of 3 to 30% when immersed in phosphate buffered saline at 50° C. for 4 hours. Aspect 8 The higher-order structural body according to any one of aspects 1 to 7, wherein the higher-order structural body has a thickness of 30 to 5000 μm. Aspect 9 A higher-order structure according to any one of aspects 1 to 8, wherein the higher-order structure has a porosity of 60 to 97%. Aspect 10 6. The higher-order structure according to embodiment 4 or 5, wherein the thermoplastic resin is coated with a biodegradable resin. Aspect 11 11. The higher-order structural body according to any one of embodiments 1 to 10, wherein the higher-order structural body is in the form of a knitted fabric. Aspect 12 A laminated higher-order structure comprising the higher-order structure according to any one of aspects 1 to 11 and a structure made of a biodegradable resin. Aspect 13 Aspect 13. The laminated high-order structure according to aspect 12, wherein the structure made of biodegradable resin is a nonwoven fabric. Aspect 14 14. The multilayer high-order structure according to aspect 12 or 13, wherein the weight loss rate of the multilayer high-order structure when immersed in phosphate buffered saline at 50° C. for 4 hours is 3 to 30%. Aspect 15 15. The multilayer high-order structure according to any one of aspects 12 to 14, wherein the thickness of the multilayer high-order structure is 30 to 5000 μm. Aspect 16 16. The multilayer high-order structure according to any one of aspects 12 to 15, wherein the multilayer high-order structure has a porosity of 10 to 90%. Aspect 17 12. The higher-order structure according to any one of aspects 1 to 11, having an average coefficient of friction of 0.15 to 0.60. Aspect 18 17. The laminated high-order structure according to any one of aspects 12 to 16, having an average coefficient of friction of 0.15 to 0.60. Aspect 19 12. The higher-order structure according to any one of embodiments 1 to 11, wherein the average deviation of the friction coefficient is 0.40 to 1.80. Aspect 20 17. The laminated high-order structure according to any one of aspects 12 to 16, wherein the average deviation of the friction coefficient is 0.40 to 1.80. (Second mode) Aspect 21 A fibrous sheet structure, the fiber sheet structure includes a knitted structure and has a cell-mounting surface and a back surface; the average pore size of the back surface is smaller than the average pore size of the cell-mounting surface, the knitted structure includes a doubling bundle made of a gelatin fiber bundle and a thermoplastic resin fiber bundle, The thickness of the fiber sheet structure is 30 to 5000 μm, the number of gelatin fibers constituting the gelatin fiber bundle is 5 to 60, and the fineness of the gelatin fibers is 0.5 to 10 dtex, A fiber sheet structure in which the total number of gelatin fiber bundles and thermoplastic resin fiber bundles in the doubled yarn bundle is 2 to 20, and the ratio of the number of gelatin fiber bundles to the number of thermoplastic resin fiber bundles in the doubled yarn bundle is 5:1 to 1:5. Aspect 22 A fibrous sheet structure according to aspect 21, which is any one of the following (1) to (4): (1) A structure in which two layers are laminated, the surface layer and the back layer are knitted, and the knitted structure is plain knit or plain knit; (2) A structure in which three layers are laminated, the surface layer is a knitted structure, the back layer is a nonwoven fabric, an intermediate layer between the surface layer and the back layer is a knitted structure, the knitted structure is a plain knit or plain knit, and the nonwoven fabric contains gelatin fibers; (3) A structure in which two layers are laminated, the surface layer being a knitted structure and the back layer being a nonwoven fabric, the knitted structure being a rib knit, and the nonwoven fabric containing gelatin fibers; (4) A knitted structure consisting of rib knitting. Aspect 23 The average pore size of the cell-mounting surface is 5 to 123 μm, and the number of pores of 150 μm or larger on the cell-mounting surface is 35% or less, and the number of pores in the knitted structure is 600 / mm 3 23. The fiber sheet structure according to claim 21 or 22. Aspect 24 A fiber sheet structure according to any one of aspects 21 to 23, wherein the swelling ratio of the doubly-wound bundle when immersed in phosphate buffered saline at 50° C. for 4 hours is 110 to 350%. Aspect 25 25. The fiber sheet structure according to any one of embodiments 21 to 24, wherein the doubling bundle has a tensile strength of 1.0 to 20.0 cN / dtex and a breaking elongation of 20 to 250%. Aspect 26 A fiber sheet structure according to any one of aspects 21 to 25, wherein the fiber sheet structure has a weight loss of 3 to 30% when immersed in phosphate buffered saline at 50° C. for 4 hours. [Effects of the Invention]

[0011] The fiber sheet structure of the present invention contains gelatin fiber bundles that have a good texture and high tensile strength and large elongation at break. Therefore, it is possible to form a fiber sheet structure using gelatin fiber bundles, and the fiber sheet structure of the present invention, which contains such gelatin in the form of fiber bundles as a component, becomes a medical material that has excellent mechanical strength and biocompatibility (low antigenicity and high bioabsorbability), and can be suitably used as a material for wound and burn treatment, a matrix material for artificial skin, etc.

[0012] The fiber sheet structure of the present invention has excellent cell adhesiveness and cell culture properties for cell fixation. Gelatin is a biocompatible material (low antigenicity and high bioabsorbability), so it can be suitably used as a scaffold for 3D cell culture, which is excellent for promoting cell differentiation, enhancing cell function, and post-transplant fixation. Furthermore, the fiber sheet structure of the present invention has softness and slipperiness similar to that of living tissue in a wet state. Therefore, it can be suitably used as a material for wound and burn treatment, a matrix material for artificial skin, etc., and is less likely to cause inflammation when rubbed against living tissue. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments. In the following embodiments, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present invention. First Embodiment <Higher-order structure> The higher-order structural body of the first embodiment includes gelatin fiber bundles.

[0014] The higher-order structure of the first embodiment may be any structure containing gelatin fiber bundles, but knitted fabrics, woven fabrics, and braided cords are preferred, and knitted fabrics are more preferred from the viewpoints of shrinkage (handling properties), dimensional stability, mechanical properties, and having an appropriate amount of space for cell proliferation.

[0015] Knitted fabrics can curl when trimmed and immersed in culture medium. To prevent curling, knitting can be done using techniques such as rib knitting or garter stitching, or by sewing two pieces of knitted fabric that curl symmetrically together to form a double knit. Double knitting not only prevents curling, but also has the advantage of improving cell culture when used as a scaffold, as the highly hydrophilic nature of gelatin makes it easier for cell culture medium to be retained in the mesh of the knit.

[0016] When the higher-order structure of the first embodiment is immersed in phosphate buffered saline at 50°C for 4 hours, the weight loss rate is preferably 3 to 30%, more preferably 5 to 28%, even more preferably 7 to 26%, particularly preferably 7 to 24%, and most preferably 7 to 22%. 2 The weight of the product was measured, wrapped in a 10 μm membrane filter, and immersed in phosphate-buffered saline at 50°C for 4 hours. The membrane filter containing the higher-order structures was then removed from the phosphate-buffered saline and immersed in room temperature water for 30 minutes. The water was then absorbed with a Kimtowel, and the membrane filter containing the higher-order structures was dried at 80°C for 24 hours. The higher-order structures were then removed from the membrane filter and their weight was measured. The value was calculated using the following formula.

[0017] Weight loss rate [%] = 100 - [100 × (weight after immersion)] / (weight before immersion) When the weight loss rate of the higher-order structures of the first embodiment when immersed in phosphate-buffered saline at 50°C for 4 hours is within the above range, the structure exhibits excellent cell adhesiveness and can suppress the proliferated cells from becoming cancerous. When cells strongly adhere to the higher-order structures, the cells tend to grow in a two-dimensional form, making the structure suitable for use primarily as an implantable medical material. When cells weakly adhere to the higher-order structures, the cells tend to grow in a three-dimensional form such as a spheroid, making the structure suitable for use as a scaffold for ex vivo three-dimensional cell culture. Furthermore, the structure can prevent gelatin from easily dissolving in vivo, and furthermore, the structure exhibits excellent handleability when used as a medical material or a scaffold for three-dimensional cell culture.

[0018] The weight loss rate can be controlled by subjecting the gelatin fiber bundle precursor to any of the following treatments (water-resistant treatments): thermal crosslinking, chemical crosslinking using a crosslinking agent, and physical crosslinking using ultraviolet rays, radiation, or electron beams.

[0019] The thickness of the higher-order structures of the first embodiment is preferably 30 to 5,000 μm, more preferably 50 to 3,000 μm, even more preferably 100 to 2,000 μm, and particularly preferably 150 to 1,000 μm. A thickness of less than 30 μm is undesirable because the higher-order structures have low strength and are prone to tearing. A thickness of more than 5,000 μm may result in sufficient strength for handling, but when used as a scaffold for cell culture, problems may arise, such as cells dying near the center of the higher-order structures due to lack of oxygen. The thickness can be measured by attaching adhesive tape to the edges of a 3 cm square cut-out of the higher-order structures to fix the higher-order structures, and then using a contact thickness gauge.

[0020] The porosity of the high-order structures of the first embodiment is preferably in the range of 60 to 97%, more preferably 65 to 95%, even more preferably 70 to 93%, and particularly preferably 75 to 92%. If the porosity is less than 60%, the stretchability of the high-order structures will be significantly reduced, making it difficult, for example, to attach the high-order structures along the affected area. On the other hand, if the porosity exceeds 97%, the pores will be too large, making it difficult to fix cells to the high-order structures. The porosity is calculated using the following formula, measuring the thickness and weight of a high-order structure cut into a 5 cm square. Porosity (%)=100×[1-a÷{(b+c)÷(b÷d+c÷e)}÷(f×25)] a: Weight (g) of the high-order structure cut into 5 cm squares b: Fineness of gelatin fiber bundle (dtex) c: thermoplastic fiber bundle fineness (dtex) d: Gelatin fiber bundle density (g / cm 3 ) e: Thermoplastic fiber bundle density (g / cm 3 ) f: Thickness of the higher-order structure (cm) The gelatin fiber bundle density is 1.27 g / cm 3 , thermoplastic fiber bundle density of polyglycolic acid fiber bundle density of 1.53 g / cm 3 , polylactic acid fiber bundle density 1.25g / cm 3 In addition, when the higher-order structure is produced using only gelatin fiber bundles without using thermoplastic fiber bundles, the above c and e are not included in the calculation.

[0021] The higher-order structural body of the first embodiment can be produced by a known method used for producing knitted fabrics, woven fabrics, braided cords, and the like.

[0022] The high-order structure of the first embodiment contains gelatin fiber bundles, which gives it a texture similar to that of biological tissue in a wet state, making it more slippery than a high-order structure made only of thermoplastic resin fiber bundles. In order to make the texture of the thermoplastic resin fiber bundles similar to that of biological tissue, the surfaces of the thermoplastic resin fiber bundles may be coated with collagen, gelatin, or the like.

[0023] Generally, higher-order structures made of thermoplastic resin fiber bundles are hydrophobic, which makes it extremely difficult to impregnate the higher-order structures with cell culture medium. However, the higher-order structures of the first embodiment contain gelatin fiber bundles, which are highly hydrophilic, so they can be easily impregnated with cell culture medium, allowing cells to easily settle and proliferate inside the higher-order structures. The higher-order structural body of the first embodiment will be described in detail below. (gelatin fiber bundles) The number of gelatin fibers constituting the gelatin fiber bundle of the first embodiment is preferably 2 to 90, more preferably 3 to 60, and even more preferably 4 to 50.

[0024] The fineness of the gelatin fiber bundle is preferably 10 to 600 dtex, more preferably 30 to 500 dtex, and even more preferably 50 to 400 dtex. The fineness of the gelatin fiber bundle is a value measured in grams per 10,000 m.

[0025] When the number of fibers constituting the gelatin fiber bundle and the fineness of the gelatin fiber bundle are within the above ranges, the quality of the higher-order structural body, such as texture, stretchability, and dimensional stability, can be improved.

[0026] The fineness of the gelatin fiber bundle can be controlled by the number of fibers constituting the gelatin fiber bundle and the fineness of the gelatin fiber, which will be described later.

[0027] The tensile strength of the gelatin fiber bundle of the first embodiment is preferably 0.5 to 3.0 cN / dtex, more preferably 0.7 to 2.8 cN / dtex, and even more preferably 1.0 to 2.5 cN / dtex. The tensile strength of the gelatin fiber bundle is measured using, for example, Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.).

[0028] The breaking elongation of the gelatin fiber bundle is preferably 30 to 300%, more preferably 30 to 250%, further preferably 40 to 200%, and particularly preferably 50 to 150%. The breaking elongation of the gelatin fiber bundle is measured using Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.).

[0029] When the tensile strength and breaking elongation of the gelatin fiber bundle are within the above ranges, it is possible to prevent the fiber bundle from breaking during winding, unwinding, and production of higher-order structures, and it is possible to easily produce higher-order structures.

[0030] The tensile strength and breaking elongation of the gelatin fiber bundle can be controlled by the type of gelatin and spinning conditions, which will be described later.

[0031] The weight loss rate when the gelatin fiber bundle of the first embodiment is immersed in phosphate buffered saline at 50° C. for 4 hours is preferably 3 to 30%, more preferably 5 to 28%, even more preferably 7 to 26%, particularly preferably 7 to 24%, and most preferably 7 to 22%. The weight loss rate is a value calculated using the following formula after measuring the weight of a 100 mm gelatin fiber bundle, wrapping it in a 10 μm membrane filter, and immersing it in phosphate buffered saline at 50° C. for 4 hours, removing the membrane filter containing the gelatin fiber bundle from the phosphate buffered saline and immersing it in room temperature water for 30 minutes, then absorbing the water with a Kimtowel, and drying the membrane filter containing the gelatin fiber bundle at 80° C. for 24 hours, removing the fiber bundle from the membrane filter and measuring its weight.

[0032] Weight loss rate [%] = 100 - [100 × (weight after immersion)] / (weight before immersion) If the weight loss rate of the gelatin fiber bundle of the first embodiment when immersed in phosphate-buffered saline at 50°C for 4 hours is within the above range, the bundle will have excellent cell adhesiveness and will be able to suppress the canceration of proliferated cells. When cells strongly adhere to the higher-order structures, the cells tend to grow in a two-dimensional form, making the bundle suitable for use primarily as an implantable medical material. When cells weakly adhere to the higher-order structures, the cells tend to grow in a three-dimensional form such as a spheroid, making the bundle suitable for use as a scaffold for ex vivo three-dimensional cell culture. Furthermore, the bundle will be able to prevent gelatin from easily dissolving in vivo, and will have excellent handleability when used as a medical material or a scaffold for three-dimensional cell culture.

[0033] The weight loss rate when a gelatin fiber bundle is immersed in phosphate buffered saline at 50°C for 4 hours can be controlled by the degree of insolubilization treatment described below.

[0034] The swelling ratio of the gelatin fiber bundle of the first embodiment when immersed in phosphate buffered saline at 50° C. for 4 hours is preferably 110 to 350%, more preferably 120 to 300%, and even more preferably 130 to 300%. The swelling ratio is a value calculated by measuring the fiber diameter of the gelatin fibers constituting the gelatin fiber bundle with a HIROX RH2000 optical microscope, immersing the gelatin fiber bundle in phosphate buffered saline at 50° C. for 4 hours, then pulling the gelatin fiber bundle out of the phosphate buffered saline, measuring the fiber diameter of the gelatin fibers in a wet state, and calculating the swelling ratio using the following formula:

[0035] Swelling ratio [%] = 100 × (fiber diameter after immersion) / (fiber diameter before immersion) If the swelling ratio of the gelatin fiber bundle of the first embodiment when immersed in phosphate-buffered saline at 50°C for 4 hours is within the above range, the bundle will have excellent cell adhesiveness and will be able to suppress the canceration of proliferated cells. When cells strongly adhere to the higher-order structures, the cells tend to grow in a two-dimensional form, making the bundle suitable for use primarily as an implantable medical material. When cells weakly adhere to the higher-order structures, the cells tend to grow in a three-dimensional form such as a spheroid, making the bundle suitable for use as a scaffold for ex vivo three-dimensional cell culture. Furthermore, the bundle will be able to prevent gelatin from easily dissolving in vivo, and will have excellent handleability when used as a medical material or a scaffold for three-dimensional cell culture. The cross-sectional shapes of the gelatin fibers that make up the gelatin fiber bundles include solid circle, hollow, flat, star, triangular, solid circle + fin, hollow + fin, etc. When used as a scaffold for 3D cell culture, irregular cross-section threads such as flat, star, and triangular may be preferable to solid circle.

[0036] When measuring the tensile strength, breaking elongation, weight loss rate and swelling rate of the above-mentioned gelatin fiber bundle from the higher-order structure, the higher-order structure was cut with scissors, and the thread end was pinched and pulled out for 5 cm or more to prepare a sample for measurement. (Method of manufacturing a high-order structure) A method for producing the high-order structure of the first embodiment will be described below, but is not particularly limited.

[0037] The method for producing a high-order structure preferably includes the following steps 1 and 2 and step 3-1 or step 3-2.

[0038] (Step 1) A step of extruding a dope made of a gelatin solution containing 30 to 70% by weight of a gelatin raw material from a multi-hole spinneret into a fiber form at a temperature 1 to 15°C higher than the sol-gel transition temperature of the gelatin dope; (Step 2) A step of winding the extruded gelatin fibers onto a bobbin to prepare a gelatin fiber bundle precursor; (Step 3-1) a step of insolubilizing the gelatin fiber bundle precursor and then organizing it to prepare a higher-order structure; (Step 3-2) A step of organizing the gelatin fiber bundle precursor and then insolubilizing it to prepare a higher-order structure.

[0039] It is preferable that the step 2 includes a conveying step of conveying the extruded gelatin fibers along the circumferential surface of a conveying roller before being wound onto a bobbin, and that the moisture content of the gelatin fibers when they reach the first conveying roller that the extruded gelatin fibers reach first is 5 to 25% by weight.

[0040] The moisture content of the gelatin fiber bundle precursor is preferably 5 to 20% by weight.

[0041] The step 2 includes a step of adhering a mixed solution of at least one selected from ethylene glycol, polyethylene glycol, and glycerin with a lower alcohol to the extruded gelatin fibers before winding them onto a bobbin.

[0042] In the step 1, it is preferable that the gelatin has a jelly strength of 100 to 350 g and the gelatin dope has a sol-gel transition temperature of 15 to 60°C.

[0043] The high-order structures of the first embodiment can be produced by extruding a dope made of a gelatin solution into fibers from a multi-hole spinneret, winding the extruded gelatin fibers around a bobbin to produce gelatin fiber bundle precursors, insolubilizing the gelatin fiber bundle precursors to produce gelatin fiber bundles, and then organizing the gelatin fiber bundles. Alternatively, as described above, fiber bundle precursors may be produced, organized, and then insolubilized to produce high-order structures made of gelatin fiber bundles.

[0044] Texturing refers to the production of a woven fabric, knitted fabric, or braided cord from fiber bundles or fiber bundle precursors.

[0045] The gelatin raw material constituting the gelatin solution is obtained by unraveling the triple helix of collagen derived from bovine bone, bovine hide, pigskin, bird, or fish, resulting in a single molecular chain. Methods for producing such gelatin raw materials include acid treatment and lime treatment. The gelatin raw material used in the first embodiment may be gelatin raw material produced by either method, or may be commercially available gelatin raw material. Commercially available gelatin raw materials undergo various purification steps before extraction during their production process, resulting in low levels of components other than protein. Typically, they have a composition of 85% or more protein, 8-14% water, 2% or less ash, and 1% or less other components (lipids, polysaccharides, etc.). The first embodiment can also use such a common gelatin raw material. Because gelatin raw material is a thermally denatured form of collagen, its amino acid composition is nearly identical to that of collagen, but is highly unique compared to other proteins, with glycine accounting for approximately one-third of the total and repeating every third amino acid in the amino acid sequence. Collagen and gelatin can be distinguished, for example, by observing the 31.5-degree signal obtained by wide-angle X-ray measurement. This 31.5-degree signal is derived from the triple helix structure of collagen, and when the triple helix structure that characterizes collagen is unraveled and becomes gelatin, this signal disappears.

[0046] Furthermore, although there are no particular limitations on the molecular weight of the gelatin raw material, the jelly strength, which is highly correlated with the molecular weight, is preferably 100 to 350 g, more preferably 150 to 320 g, and even more preferably 220 to 310 g, from the viewpoint of spinnability. The jelly strength is determined by cooling a 6.67% gelatin aqueous solution at 10°C for 17 hours, and measuring the load (g) required to press down 4 mm on the surface of the prepared gelatin solution with a half-inch (12.7 mm) diameter plunger using a small benchtop tester EZ-SX manufactured by Shimadzu Corporation.

[0047] When the jelly strength of the gelatin raw material is within the above range, a significant decrease in the spinnability of the gelatin fiber can be prevented, and further, by suppressing the moisture retention rate in the fiber, thread breakage during winding can be prevented.

[0048] The content of the gelatin raw material in the gelatin solution is preferably 30 to 70% by weight, more preferably 40 to 60% by weight. When the content of the gelatin raw material in the gelatin solution is within the above range, a significant decrease in the spinnability of the gelatin fiber can be prevented, and further, bubbles generated in the process of producing the gelatin solution can be easily degassed, preventing thread breakage during spinning.

[0049] The solvent for dissolving the gelatin raw material is water, but (polyhydric) alcohols, dimethyl sulfoxide, etc. may be added to adjust the viscosity as needed.

[0050] The sol-gel transition temperature of the gelatin solution is preferably 15 to 60° C., more preferably 20 to 60° C., even more preferably 20 to 55° C., and particularly preferably 20 to 50° C. The sol-gel transition temperature is measured using, for example, an ARES rheometer manufactured by TA Instruments.

[0051] When the sol-gel transition temperature is within the above range, the gelatin fiber is prevented from becoming too sticky, the handling property during production is improved, and furthermore, adhesion of wound gelatin fibers can be prevented. Also, thermal decomposition of gelatin at the spinning temperature, which causes breakage of fibers, can be prevented.

[0052] Gelatin fiber bundle precursors are produced by extruding a dope consisting of gelatin raw material and a solvent such as water into the air through a multi-hole spinneret in the form of fibers, and by stretching the dope just below the spinneret to appropriately orient the molecular chains of the unwound collagen triple helix molecules and by appropriately controlling the water content within the fibers. By controlling the degree of orientation of the molecular chains of the unwound collagen triple helix molecules and the water content within the fibers, it is possible to increase the tensile strength and breaking elongation of the yarn while suppressing adhesion between the fibers.

[0053] The spinning method in which the dope is extruded into the air in the form of fibers from a multi-hole spinneret may be any of a dry method, a semi-dry method, and a wet method, but dry production is preferred because it can prevent the formation of voids on the surface or inside of the fiber during the process of drying and removing the solvent, and can suppress a decrease in the tensile strength and breaking elongation of the gelatin fiber. The dry spinning temperature is preferably 1 to 25°C higher, and more preferably 5 to 20°C higher, than the sol-gel transition temperature of the dope. Within the above range, a significant decrease in spinnability can be prevented.

[0054] In the production of the gelatin fiber bundle precursor used in the first embodiment, it is preferable to rapidly reduce the moisture content in the fiber to a range of 5 to 25% by weight immediately after spinning. If the moisture content in the fiber is within the above range, adhesion can be suppressed, and it is possible to prevent the gelatin fibers discharged from the multi-hole spinneret from adhering to each other and the gelatin fibers from sticking to rollers during the production process, and it is also possible to easily unwind the wound gelatin fiber precursor from the bobbin. Furthermore, it is possible to suppress a significant decrease in the elongation of the thread, and it is possible to prevent thread breakage during the process of producing the gelatin fiber bundle and the process of producing higher-order structures by rewinding them from the bobbin.

[0055] The method may include a conveying step of conveying the gelatin fibers extruded from the spinneret along the circumferential surface of a conveying roller before winding the gelatin fibers onto a bobbin.

[0056] The moisture content of the gelatin fiber when it first reaches the first conveying roller is preferably 5 to 25% by weight, more preferably 5 to 20% by weight. The moisture content is measured by winding the gelatin thread around the first conveying roller, measuring 0.5 g of the wound fiber, and using a Karl Fischer moisture content meter (EV-2010 manufactured by Hiranuma Co., Ltd.) at 150°C in a N2 atmosphere.

[0057] When the moisture content is within the above range, it is possible to prevent the gelatin fibers from sticking to the transport roller, and also possible to suppress a significant decrease in the elongation of the yarn, thereby preventing yarn breakage.

[0058] The moisture content can be controlled by drying with dry air or dry hot air.

[0059] In addition, in order to prevent adhesion due to contact between the fibers, it is preferable to use a grooved guide roller as the transport roller.

[0060] The moisture content of a gelatin fiber bundle precursor obtained by winding gelatin fibers on a bobbin is preferably 5 to 20% by weight, more preferably 5 to 15% by weight. The moisture content is measured by measuring 0.5 g of the fiber bundle precursor wound on a bobbin using a Karl Fischer moisture content meter (EV-2010 manufactured by Hiranuma Corporation) at 150°C in a N2 atmosphere.

[0061] When the moisture content is within the above range, the gelatin fiber precursor can be easily unwound from the bobbin, and a significant decrease in the elongation of the thread can be suppressed, and thread breakage can be prevented during the process of rewinding the thread from the bobbin to produce a higher-order structure.

[0062] The moisture content can be controlled by drying with dry hot air, etc. After passing through the first transport roller, the fiber bundle can be dried as needed with a winder.

[0063] The gelatin fiber bundle used in the first embodiment is preferably produced with a spinning draft (extrusion linear velocity / winding speed) in the range of 0.01 to 2, more preferably in the range of 0.05 to 1.5. Within the above range, the molecular chains of the unwound collagen triple helix molecules are sufficiently oriented, preventing a decrease in tensile strength, and preventing the fiber diameter from becoming too thick. The moisture content of the gelatin fibers can be sufficiently reduced before they reach the first conveying roller, and as a result, the gelatin fibers can be prevented from sticking to the roller. Furthermore, a significant decrease in breaking elongation can be prevented, preventing thread breakage during the process of producing the gelatin fiber bundle and the process of producing higher-order structures by rewinding them from the bobbin.

[0064] The method may include a step of applying an oil to the gelatin fibers extruded from the spinneret before winding them onto a bobbin. It is preferable to apply an oil to the fiber surface after the moisture content within the fiber reaches a range of 5 to 20% by weight. Applying an oil to the fiber surface allows multiple gelatin fibers to be bundled together and handled as a gelatin fiber bundle. The application of an oil significantly improves the handleability of the yarn during the gelatin fiber bundle production process and the process of rewinding the fiber from the bobbin to produce a higher-order structural body. Since the higher-order structural body of the first embodiment is used as a medical material, it is preferable to use a biocompatible oil, such as ethylene glycol, polyethylene glycol, or glycerin. It is preferable to dilute these compounds with a lower alcohol, such as ethanol, and apply the resulting mixed solution to the fiber surface, followed by drying to remove the lower alcohol. The oil may be removed by washing after the higher-order structural body is produced, or it may be left in the applied state. There is no restriction on the amount of oil to be applied as long as it is an amount that can bundle a plurality of gelatin fibers into a fiber bundle, but for example, 0.5 to 5% by weight is preferred.

[0065] The cross-sectional shape of gelatin fibers can be any shape. Examples of cross-sectional shapes include solid circle, hollow, flat, star, triangular, solid circle + fin, hollow + fin, etc. When used as a 3D cell culture scaffold, irregular cross-section threads such as flat, star, or triangular cross-sections may be preferable to solid circle cross-sections.

[0066] The tensile strength of the gelatin fiber is preferably 0.5 to 3 cN / dtex, more preferably 0.7 to 2.8 cN / dtex, and even more preferably 1.0 to 2.5 cN / dtex. The tensile strength of the gelatin fiber is measured by taking out a single yarn from the gelatin fiber bundle precursor and using, for example, Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.).

[0067] The breaking elongation of the gelatin fiber is preferably 30 to 250%, more preferably 40 to 200%, and even more preferably 50 to 150%. The breaking elongation of the gelatin fiber is measured by taking a single yarn from a gelatin fiber bundle and using, for example, Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.).

[0068] When the tensile strength and breaking elongation of the gelatin fiber are within the above ranges, the gelatin fiber can withstand the production of gelatin fiber bundles and the production of higher-order structures.

[0069] The process of insolubilizing the gelatin fiber bundle precursor may involve insolubilizing the gelatin fiber bundle precursor to produce gelatin fiber bundles, or may involve organizing the fiber bundle precursor and then insolubilizing it to produce a higher-order structure composed of gelatin fiber bundles. The insolubilization (treatment to make the fiber bundle precursor insoluble in water) may be performed by any of thermal crosslinking, chemical crosslinking using a crosslinking agent, or physical crosslinking using ultraviolet light, radiation, or an electron beam, or a combination of these methods as appropriate. Thermal crosslinking may be performed in the atmosphere or in a vacuum. The temperature during thermal crosslinking is preferably in the range of 110 to 200°C, more preferably 120 to 190°C, and even more preferably 130 to 180°C. Temperatures below 100°C result in insufficient crosslinking, and the gelatin will dissolve in water in a wet state, making it unusable as a scaffold. Temperatures above 200°C are undesirable because the gelatin will thermally decompose, significantly reducing fiber strength. The degree of crosslinking can be changed as needed by adjusting the combination of the heat treatment temperature and the heat treatment time, but the heat treatment time is preferably 3 to 48 hours, and more preferably 4 to 24 hours from the viewpoint of productivity. In the case of chemical crosslinking using a crosslinking agent, voids may form in the fiber during the washing process to remove the crosslinking agent from the fiber, which may result in a decrease in the tensile strength and breaking elongation of the gelatin fiber. In this case, thread breakage may occur during the process of producing higher-order structures from insolubilized gelatin fiber bundles. For this reason, when performing insolubilization treatment by chemical crosslinking, it is preferable to perform the chemical crosslinking treatment after organizing the fiber bundle precursor. Examples of crosslinking agents used in chemical crosslinking include glutaraldehyde and hexamethylene diisocyanate.

[0070] The higher-order structural body produced in the first embodiment may be immersed in, for example, a 20 to 80% glycerin aqueous solution. By immersing the higher-order structural body in a glycerin aqueous solution, it is possible to produce a medical material with a moist texture and better conformability to the affected area.

[0071] The higher-order structure of the first embodiment may contain an additive. Examples of additives include polyvalent acids such as (anhydrous) citric acid and (anhydrous) maleic acid, magnetic particles such as γ-iron oxide, inorganic substances such as hydroxyapatite, endogenous proteins that promote cell proliferation and differentiation, collagen, etc. These additives may be coated onto the higher-order structure, onto the gelatin fiber bundles, gelatin fiber bundle precursors, or gelatin fibers, or may be added to the gelatin raw material. (paired yarn bundle) The higher-order structural body of the first embodiment may further contain thermoplastic resin fiber bundles, or may be a doubling bundle of gelatin fiber bundles and thermoplastic resin fiber bundles.

[0072] The thermoplastic resin in the thermoplastic resin fiber bundle is not limited as long as it is a resin used as a medical material, and examples include polyethylene terephthalate (PET), polylactic acid (PLLA, PLLDA), poly-ε-caprolactone (PCL) and their (LA-CL) copolymers, polyglycolic acid (PGA), glycolic acid and lactic acid copolymer (PLGA), polyglutamic acid, etc. Among these, polylactic acid (PLLA, PLLDA), glycolic acid and lactic acid copolymer (PLGA), polyglycolic acid (PGA), and polyglutamic acid are preferred because the acid generated during decomposition of the thermoplastic resin fiber bundle is relatively mild and is less likely to cause inflammation.

[0073] The number of thermoplastic resin fibers constituting the thermoplastic resin fiber bundle is preferably 5 to 70, more preferably 7 to 50, and even more preferably 10 to 30.

[0074] Within the above range, the strength of the gelatin-containing higher-order structure can be significantly improved, which is preferable.

[0075] The total number of gelatin fibers and thermoplastic resin fibers constituting the doubled yarn bundle is preferably 10 to 300, more preferably 20 to 280, and even more preferably 25 to 250.

[0076] Within the above range, the gelatin-containing higher-order structure not only has high strength but also has appropriate slip properties in wet conditions, making it possible to embed or wrap it around a sliding portion around cartilage, for example.

[0077] The fineness of the thermoplastic resin fiber bundle is preferably 10 to 100 dtex, more preferably 15 to 60 dtex, and even more preferably 20 to 50 dtex.

[0078] Within the above range, it is preferable from the viewpoint of improving the quality of the higher-order structural body, such as texture, stretchability, and dimensional stability.

[0079] The fineness of the doubled yarn bundle is preferably 20 to 800 dtex, more preferably 40 to 700 dtex, and even more preferably 50 to 600 dtex.

[0080] Within the above range, the gelatin-containing higher-order structure has high strength, and in addition to improving qualities such as texture, stretchability, and dimensional stability, it is preferable that the gelatin-containing higher-order structure has appropriate slip properties under wet conditions that can be applied to sliding parts such as the area around cartilage.

[0081] The tensile strength of the doubled yarn bundle is preferably 1.0 to 20.0 cN / dtex, more preferably 2.0 to 18.0 cN / dtex, even more preferably 3.0 to 15.0 cN / dtex, and particularly preferably 4.0 to 12.0 cN / dtex. The tensile strength of the doubled yarn bundle is measured, for example, using a Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.).

[0082] The breaking elongation of the doubled yarn bundle is preferably 20 to 250%, more preferably 20 to 200%, further preferably 20 to 150%, and particularly preferably 25 to 150%. The breaking elongation of the doubled yarn bundle is measured using a Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.).

[0083] When the tensile strength and breaking elongation of the yarn bundle are within the above ranges, yarn breakage can be prevented during winding and unwinding of the yarn bundle and production of a higher-order structure, making it possible to easily produce a higher-order structure.

[0084] The weight loss rate when the yarn bundle of the first embodiment is immersed in phosphate buffered saline at 50° C. for 4 hours is preferably 3 to 30%, more preferably 5 to 28%, even more preferably 7 to 26%, particularly preferably 7 to 24%, and most preferably 7 to 22%. The weight loss rate is calculated by measuring the weight of a 100 mm yarn bundle, wrapping it in a 10 μm membrane filter, immersing it in phosphate buffered saline at 50° C. for 4 hours, removing the membrane filter with the yarn bundle from the phosphate buffered saline, immersing it in room temperature water for 30 minutes, absorbing the water with a Kimtowel, drying the membrane filter with the yarn bundle at 80° C. for 24 hours, removing the yarn bundle from the membrane filter, measuring its weight, and calculating the weight using the following formula:

[0085] Weight loss rate [%] = 100 - [100 × (weight after immersion)] / (weight before immersion) When the weight loss rate of the doped yarn bundle of the first embodiment when immersed in phosphate-buffered saline at 50°C for 4 hours is within the above range, the yarn bundle exhibits excellent cell adhesiveness and can suppress the proliferated cells from becoming cancerous. When cells strongly adhere to the higher-order structures, the cells tend to grow in a two-dimensional form, making the yarn bundle suitable for use primarily as an implantable medical material. When cells weakly adhere to the higher-order structures, the cells tend to grow in a three-dimensional form such as a spheroid, making the yarn bundle suitable for use as a scaffold for ex vivo three-dimensional cell culture. Furthermore, the yarn bundle can prevent gelatin from easily dissolving in vivo, and furthermore, the yarn bundle exhibits excellent handleability when used as a medical material or a scaffold for three-dimensional cell culture.

[0086] The weight loss rate when the doubled yarn bundle is immersed in phosphate buffered saline at 50°C for 4 hours can be controlled by the degree of insolubilization treatment described below.

[0087] The swelling ratio of the yarn bundle of the first embodiment when immersed in phosphate buffered saline at 50° C. for 4 hours is preferably 110 to 350%, more preferably 120 to 300%, and even more preferably 130 to 300%. The swelling ratio is a value calculated using the following formula, by measuring the bundle diameter of the yarn bundle constituting the yarn bundle using an optical microscope RH2000 manufactured by HIROX, immersing the yarn bundle in phosphate buffered saline at 50° C. for 4 hours, removing the yarn bundle from the phosphate buffered saline, and measuring the bundle diameter of the yarn bundle in a wet state.

[0088] Swelling rate [%] = 100 × (diameter of the doubled yarn bundle after immersion) / (diameter of the doubled yarn bundle before immersion) If the swelling ratio of the yarn bundle of the first embodiment when immersed in phosphate-buffered saline at 50°C for 4 hours is within the above range, it is possible to suppress the canceration of proliferating cells, prevent gelatin from easily dissolving in the body, and further provide excellent handling properties when used as a medical material or a scaffolding material for three-dimensional cell culture.

[0089] When measuring the tensile strength, breaking elongation, weight loss rate, and swelling rate of the above-mentioned yarn bundle from the high-order structure, the high-order structure was cut with scissors, the end of the yarn was pinched, and the yarn was pulled out for 5 cm or more to prepare a sample for measurement.

[0090] The cross-sectional shape of the thermoplastic resin fibers that make up the thermoplastic resin fiber bundle may be any shape, including solid circle, hollow, flat, star, triangle, solid circle + fin, hollow + fin, etc. When used as a scaffold for 3D cell culture, irregular cross-sections may be preferable to solid circle cross-sections.

[0091] The thermoplastic resin fibers used in the high-order structure of the first embodiment may contain additives. Examples of additives include polyvalent acids such as (anhydrous) citric acid and (anhydrous) maleic acid, magnetic particles such as γ-iron oxide, inorganic substances such as hydroxyapatite, endogenous proteins that promote cell proliferation and differentiation, collagen, anticancer drugs, and the like. These additives may be coated onto the thermoplastic resin fibers.

[0092] Examples of methods for coating a thermoplastic resin fiber bundle with a biodegradable resin such as collagen include rewinding the thermoplastic fiber bundle in a washing bath to remove the oil and drying, then immersing the thermoplastic fiber bundle in a collagen solution to coat the thermoplastic fiber bundle with collagen, drying, and winding it up. Because collagen is susceptible to thermal denaturation, it is preferable to coat and dry the thermoplastic fiber bundle at temperatures below 40°C, preferably below 30°C, and more preferably below 25°C. If the coating or drying temperature is too low, the collagen solution will freeze, preventing coating or insufficient drying. Therefore, treatment at temperatures above 0°C, preferably above 5°C, and more preferably above 10°C, is preferred. The collagen solution concentration is preferably an acid solution with a concentration of 0.005 to 3 wt%. If the collagen solution concentration is less than 0.005 wt%, the thermoplastic resin fiber bundle cannot be converged with collagen, making the fiber bundle difficult to handle. On the other hand, if the collagen concentration exceeds 3 wt%, the thermoplastic resin fiber bundle will become hard and significantly less manageable. A more preferred range of collagen solution concentration is 0.01 to 2% by weight. The collagen-coated thermoplastic fiber bundle can be heat-treated at 100 to 150°C or chemically treated to make the coated collagen insoluble in water.

[0093] Because collagen has excellent cell adhesive properties, for example, higher-order structures composed of collagen-coated thermoplastic resin fiber bundles and gelatin fiber bundles have the characteristic of excellent cell culture properties, as cells do not fall out through the gaps between the fibers and the structures are able to adhere to the fibers. Furthermore, the collagen coating gives the structure a texture similar to that of living tissue, which means that the structure has excellent slipperiness in a wet state.

[0094] In addition to collagen, biodegradable resins include bio-derived resins such as gelatin, and synthetic polymers such as polyglycolic acid (PGA), polylactic acid (PLA), lactic acid-glycolic acid copolymer (PLGA), and polyglutamic acid. The ratio of the gelatin fiber bundles to the thermoplastic resin fiber bundles in the doubled yarn bundle (fineness of the gelatin fiber bundles: fineness of the thermoplastic resin fiber bundles) is 1:5 to 5:1. (Manufacturing method of doubled yarn bundle) The thermoplastic resin fiber of the first embodiment can be produced by melt spinning, and a commercially available thermoplastic resin fiber bundle can also be purchased and used.

[0095] The high-order structure including the doubled yarn bundle of the first embodiment is manufactured using a doubled yarn bundle precursor made of a gelatin fiber bundle precursor and a thermoplastic resin fiber bundle as a starting material. The doubled yarn bundle precursor made of a gelatin fiber bundle precursor and a thermoplastic resin fiber bundle can be manufactured by putting a plurality of fiber bundle precursors into a doubling machine.

[0096] The gelatin fiber bundle precursor may be twisted while spirally winding a thermoplastic resin fiber bundle around the gelatin fiber bundle precursor, or the gelatin fiber bundle precursor may be twisted while spirally winding a gelatin fiber bundle precursor around the thermoplastic resin fiber bundle.

[0097] The gelatin fiber bundle precursor having the oil agent attached thereto and the thermoplastic resin fiber bundle may be combined by twisting or the like, or the fiber bundles may be entangled by interlacing or the like.

[0098] The multi-filament bundle precursor can be prepared by preparing a multi-filament bundle from the multi-filament bundle precursor in the same manner as in the above-mentioned process of insolubilizing the gelatin fiber bundle precursor, and then organizing the multi-filament bundle to prepare a higher-order structure. Alternatively, the multi-filament bundle precursor may be organized and then insolubilized to prepare a higher-order structure made of the multi-filament bundle.

[0099] The higher-order structure containing the yarn bundle of the first embodiment may be laminated with a sheet such as a nonwoven fabric, knitted fabric, or woven fabric. For example, when laminating a gelatin or collagen nonwoven fabric, an example method is to organize a yarn bundle precursor and then laminate a nonwoven fabric on the yarn bundle precursor by electrospinning or the like. The laminated gelatin or collagen nonwoven fabric can be made insoluble in water by a crosslinking treatment. (Laminated high-order structures) The higher-order structures of the first embodiment may be laminated higher-order structures containing structures made of biodegradable resins. Examples of biodegradable resins include bio-derived resins such as gelatin and collagen, and synthetic polymers such as polyglycolic acid (PGA), polylactic acid (PLA), lactic acid-glycolic acid copolymer (PLGA), and polyglutamic acid. The structures to be laminated may be in the form of nonwoven fabrics, knitted fabrics, or woven fabrics, with nonwoven fabrics being preferred. The gaps in the higher-order structures (the meshes of the knitted fabric) are significantly larger than the size of the cells. Therefore, when the higher-order structures are used as scaffolds for cell culture, cells fall out of the gaps in the higher-order structures and are unable to settle, resulting in a long cell culture time. In contrast, when a laminated higher-order structure containing a higher-order structure and a structure made of a biodegradable resin is used as a scaffold for cell culture, the structure made of the biodegradable resin captures the cells and allows them to settle on the laminated higher-order structures, thereby shortening the cell culture time. Examples of methods for producing a laminated high-order structure comprising a high-order structure and a structure made of biodegradable resin include a method in which a roll of high-order structures is rewound while a nonwoven fabric is sprayed onto the high-order structure by electrospinning or meltblowing, and the structure is then transported and heat-pressed using a calendar roll or the like, and then wound up; and a method in which a structure made of biodegradable resin is laminated onto a cut-out high-order structure, and then heat-pressed in batches. The heat-pressing temperature is preferably 40 to 90°C, and the pressure is preferably in the range of 5 kPa to 3 MPa. Heat-pressing temperatures below 40°C tend to cause interlayer delamination between the high-order structure and the structure made of biodegradable resin that constitute the laminated high-order structure. Heat-pressing temperatures above 90°C are undesirable because the gelatin fibers constituting the high-order structure fuse together, impairing the stretchability that is a characteristic of the high-order structure of the first embodiment. The heat-pressing temperature is preferably in the range of 40 to 80°C. If the heat press pressure is less than 5 kPa, the high-order structures constituting the laminated high-order structure and the structure made of biodegradable resin are likely to delaminate, and if it exceeds 3 MPa, the stretchability that is a feature of the high-order structure of the first embodiment is lost, which is undesirable. A more preferable range of the heat press pressure is 400 kPa to 2 MPa.

[0100] The weight loss rate of the laminated high-order structure of the first embodiment when immersed in phosphate buffered saline at 50°C for 4 hours is preferably 3 to 30%, more preferably 5 to 28%, and even more preferably 7 to 26%.

[0101] Within the above range, the cell adhesiveness is excellent and the canceration of proliferated cells can be suppressed. When cells strongly adhere to the higher-order structures, the cells tend to grow in a two-dimensional form, making the material suitable for use primarily as an implantable medical material. When cells weakly adhere to the higher-order structures, the cells tend to grow in a three-dimensional form such as a spheroid, making the material suitable for use as a scaffold for ex vivo three-dimensional cell culture. Furthermore, the material can prevent gelatin from easily dissolving in vivo, and furthermore, the material has excellent handleability when used as a medical material or a scaffold for three-dimensional cell culture.

[0102] The thickness of the laminated high-order structure of the first embodiment is preferably 30 to 5000 μm, more preferably 50 to 3000 μm, even more preferably 100 to 2000 μm, and particularly preferably 150 to 1000 μm. A thickness of less than 30 μm is undesirable because the laminated high-order structure has low strength and is prone to tearing. A thickness of more than 5000 μm may result in sufficient strength for handling, but when used as a scaffold for cell culture, problems may arise, such as cells dying near the center of the thickness of the laminated high-order structure due to lack of oxygen. The thickness can be measured by attaching adhesive tape to the edges of a 3 cm square cut piece of the laminated high-order structure to fix the laminated high-order structure, and then using a contact thickness gauge.

[0103] The porosity of the laminated high-order structure of the first embodiment is preferably in the range of 60 to 97%, more preferably 65 to 95%, even more preferably 70 to 93%, and particularly preferably 75 to 92%. If the porosity is less than 60%, the stretchability of the laminated high-order structure will be significantly reduced, making it difficult, for example, to attach the laminated high-order structure along the affected area. On the other hand, if the porosity exceeds 97%, the pores will be too large, making it difficult to fix cells to the laminated high-order structure. The porosity is calculated using the following formula, measuring the thickness and weight of a 5 cm square cut out of the laminated high-order structure. Porosity (%)=100×[1-a÷{(b+c)÷(b÷d+c÷e)}÷(f×25)] a: Weight (g) of the laminated high-order structural body cut into a 5 cm square b: Fineness of gelatin fiber bundle (dtex) c: thermoplastic fiber bundle fineness (dtex) d: Gelatin fiber bundle density (g / cm 3 ) e: Thermoplastic fiber bundle density (g / cm 3 ) f: Thickness of the laminated high-order structure (cm) The gelatin fiber bundle density is 1.27 g / cm 3 , thermoplastic fiber bundle density of polyglycolic acid fiber bundle density of 1.53 g / cm 3 , polylactic acid fiber bundle density 1.25g / cm 3 In addition, when the higher-order structure is produced using only gelatin fiber bundles without using thermoplastic fiber bundles, the above c and e are not included in the calculation. <Characteristics of high-order structures and laminated high-order structures> The high-order structure and the laminated high-order structure of the first embodiment are excellent in texture, slipperiness and cell adhesiveness.

[0104] Texture can be evaluated by the feel of the high-order structures and laminated high-order structures when touched with dry hands. Texture was evaluated by pinching both ends of a 5cm square cut-out of a high-order structure with both hands and pulling it, or by pulling one pinched end upwards and the other downwards three times. A moderate degree of elasticity is necessary because without elasticity, the texture tends to become stiff, making it difficult to conform to biological tissue.

[0105] The slipperiness can be evaluated using a Kato Tech friction tester (model number: KES-SE). After immersing 5cm square pieces of the high-order structure and laminated high-order structure in distilled water for 1 hour, the sample was fixed on a measuring table with a metal frame, and a 10mm square silicon sensor was moved over the sample at 1.0mm / sec with a load of 50g to measure the average coefficient of friction and the average deviation of the coefficient of friction.

[0106] The average coefficient of friction of the high-order structure and the laminated high-order structure of the first embodiment is preferably 0.05 to 0.60, more preferably 0.10 to 0.50, even more preferably 0.15 to 0.45, and most preferably 0.20 to 0.40. Within the above ranges, the structure has slip properties similar to those of living tissue, and is less likely to cause inflammation when rubbed against living tissue.

[0107] The mean deviation of the coefficient of friction of the high-order structural body and the laminated high-order structural body of the first embodiment is preferably 0.40 to 1.60, more preferably 0.45 to 1.45, even more preferably 0.50 to 1.40, and most preferably 0.60 to 1.30. Within the above range, the high-order structural body of the first embodiment has softness and slipperiness similar to that of living tissue in a wet state. This makes it suitable for use as a material for wound and burn treatment, a matrix material for artificial skin, and the like, and is preferred because it is less likely to cause inflammation when rubbed against living tissue.

[0108] The higher-order structures and laminated higher-order structures containing gelatin fiber bundles of the first embodiment have excellent cell adhesiveness for cell fixation. Cell adhesiveness and cell culturability are strongly correlated, and strong cell adhesiveness allows cells to efficiently fix to the higher-order structures, resulting in excellent cell culturability. On the other hand, weak cell adhesiveness tends to prevent cells from successfully fixing to the higher-order structures, resulting in poor cell culturability.

[0109] Gelatin is a biocompatible material (low antigenicity and high bioabsorbability), and therefore can be suitably used as a scaffold for 3D cell culture, which is excellent in promoting cell differentiation, enhancing cell function, and providing excellent adhesion after transplantation. Furthermore, the high-order structure and laminated high-order structure of the first embodiment have softness and slipperiness similar to that of living tissue in a wet state. Therefore, they can be suitably used as materials for wound and burn treatment, matrix materials for artificial skin, and the like, and are preferred because they are less likely to cause inflammation when rubbed against living tissue.

[0110] The cell adhesion and cell culture properties of the higher-order structures and laminated structures can be evaluated by statically culturing HeLa cells on the structures for three days and observing the fluorescently labeled cells under a fluorescence microscope. Second Embodiment <Configuration of fiber sheet structure> The fiber sheet structure of the present invention includes a knitted structure and has a cell-mounting surface and a back surface, the average pore size of the back surface is smaller than the average pore size of the cell-mounting surface, the knitted structure includes a doubled yarn bundle made of gelatin fiber bundles and thermoplastic resin fiber bundles, the thickness of the fiber sheet structure is 30 to 5000 μm, the number of gelatin fibers constituting the gelatin fiber bundle is 5 to 30, the fineness of the gelatin fibers is 0.5 to 10 dtex, the total number of gelatin fiber bundles and thermoplastic resin fiber bundles in the doubled yarn bundle is 2 to 20, and the ratio of the number of gelatin fiber bundles to the thermoplastic resin fiber bundles in the doubled yarn bundle is 5:1 to 1:5.

[0111] The fiber sheet structure of the present invention includes a knitted structure. A knitted structure is a fabric structure in which a surface is formed by continuously creating loops (rings) and hooking the next loop onto the loop. Knitted structures include weft knitting and warp knitting, with weft knitting being a knitting structure in which the mesh is continuous in the weft direction and warp knitting being a knitting structure in which the mesh is continuous in the warp direction. Weft knitting includes plain knitting (jersey knitting), rib knitting, and purl knitting, while warp knitting includes tricot and raschel knitting.

[0112] The knitted structure in the fiber sheet structure of the present invention includes a ply bundle made of gelatin fiber bundles and thermoplastic resin fiber bundles.

[0113] The number of gelatin fibers constituting the gelatin fiber bundle in the fiber sheet structure of the present invention is preferably 5 to 60, and more preferably 10 to 40.

[0114] Furthermore, the fineness of the gelatin fibers constituting the gelatin fiber bundles in the fiber sheet structure of the present invention is preferably 0.5 to 10 dtex, more preferably 1 to 8 dtex, and even more preferably 2 to 5 dtex. The fineness of the gelatin fibers is a value measured in grams per 10,000 m. When the fineness of the gelatin fibers is within the above range, the gelatin fibers themselves become thin and flexible fibers, which not only can suppress the generation of fluff in the gelatin fiber bundles due to thread breakage, but also can prevent the gelatin fiber bundles from becoming hard.

[0115] When the number of gelatin fibers constituting the gelatin fiber bundles in the fiber sheet structure of the present invention and the fineness of the gelatin fibers are within the above ranges, the qualities of the fiber sheet structure such as texture, stretchability, and dimensional stability can be improved.

[0116] The preferred ranges and measurement methods for the tensile strength and breaking elongation of the gelatin fiber bundles in the fiber sheet structure of the present invention are the same as the preferred ranges and measurement methods for the tensile strength and breaking elongation of the gelatin fiber bundles in the high-order structure of the first embodiment described above.

[0117] The cross-sectional shapes of the gelatin fibers constituting the gelatin fiber bundles in the fiber sheet structure of the present invention include solid circle, hollow, flat, star, triangle, solid circle + fin, hollow + fin, etc. When used as a scaffold for three-dimensional cell culture, irregular cross-section yarns such as flat, star, and triangle may be preferable to solid circle.

[0118] When measuring the tensile strength and breaking elongation of a gelatin fiber bundle in a fiber sheet structure, a measurement sample can be prepared by treating a gelatin fiber bundle under the same conditions as those used for insolubilization in the fiber sheet structure production process, or by cutting the bundle with scissors, pinching the end of the fiber and pulling out 5 cm or more of the fiber.

[0119] The thermoplastic resin for the thermoplastic resin fiber bundles in the fiber sheet structure of the present invention is not limited as long as it is a resin used as a medical material, and examples thereof include polyethylene terephthalate (PET), polylactic acid (PLLA, PLLDA), poly-ε-caprolactone (PCL) and their (LA-CL) copolymers, polyglycolic acid (PGA), glycolic acid and lactic acid copolymer (PLGA), polyglutamic acid, etc. Among these, polylactic acid (PLLA, PLLDA), glycolic acid and lactic acid copolymer (PLGA), polyglycolic acid (PGA), and polyglutamic acid are preferred, from the viewpoint that acid generation accompanying decomposition of the thermoplastic resin fiber bundles is relatively mild and they are less likely to cause inflammation.

[0120] The number of thermoplastic resin fibers constituting the thermoplastic resin fiber bundle in the fiber sheet structure of the present invention is preferably 5 to 70, more preferably 7 to 50, and even more preferably 10 to 30. If the number is within the above range, the strength of the fiber sheet structure can be significantly improved, which is preferable.

[0121] The total number of gelatin fiber bundles and thermoplastic resin fiber bundles constituting the doubling bundle in the fiber sheet structure of the present invention is preferably 2 to 20, and more preferably 2 to 10. Within the above range, the number of times the gelatin fiber bundles and thermoplastic resin fiber bundles are doubling can be reduced, and production efficiency can be improved.

[0122] In the fiber sheet structure of the present invention, the ratio of the number of gelatin fiber bundles to the number of thermoplastic resin fiber bundles in the doubled yarn bundle is preferably 5:1 to 1:5. Within this range, the doubled yarn bundle not only has sufficient strength to withstand the production of a fiber sheet structure, but also has slip properties similar to those of living tissue, making it less likely to cause inflammation when rubbed against living tissue. A more preferred range for the number of gelatin fiber bundles to the number of thermoplastic resin fiber bundles in the doubled yarn bundle is 3:1 to 1:3.

[0123] The preferred ranges, measurement methods, and control methods for the tensile strength, breaking elongation, weight loss rate when immersed in phosphate buffered saline at 50°C for 4 hours, and swelling rate when immersed in phosphate buffered saline at 50°C for 4 hours of the doubled yarn bundle in the fiber sheet structure of the present invention are the same as the preferred ranges, measurement methods, and control methods for the tensile strength, breaking elongation, weight loss rate when immersed in phosphate buffered saline at 50°C for 4 hours, and swelling rate when immersed in phosphate buffered saline at 50°C for 4 hours of the doubled yarn bundle in the high-order structure of the first embodiment described above.

[0124] When measuring the tensile strength, breaking elongation, weight loss rate when immersed in phosphate buffered saline at 50°C for 4 hours, and swelling rate when immersed in phosphate buffered saline at 50°C for 4 hours of the doubled yarn bundle in the above-mentioned fiber sheet structure, the fiber sheet structure was cut with scissors, and the yarn end was pinched and pulled out to a length of 5 cm or more to prepare a measurement sample.

[0125] The cross-sectional shape of the thermoplastic resin fibers constituting the thermoplastic resin fiber bundle in the fiber sheet structure of the present invention may be any shape, including a solid circle, hollow, flat, star, triangle, solid circle + fin, hollow + fin, etc. When used as a scaffold for three-dimensional cell culture, a modified cross section may be preferable to a solid circle.

[0126] The thermoplastic resin fibers used in the fiber sheet structure of the present invention may contain additives, which are the same as the additives that may be contained in the thermoplastic resin fibers used in the high-order structure of the first embodiment described above.

[0127] The fiber sheet structure of the present invention has a cell-mounting surface and a back surface. The cell-mounting surface is the surface on which cells are placed for cell culture and into which the cells invade, and refers to the surface that becomes the upper surface when placed in a cell culture vessel.

[0128] In the fiber sheet structure of the present invention, the average pore size of the cell-mounting back surface is smaller than the average pore size of the cell-mounting front surface, which has the effect of allowing cells to invade and settle inside the fiber sheet structure through the cell-mounting front surface, which does not impede cell penetration, and preventing cells from slipping off through the mesh of the cell-mounting back surface, which has a smaller average pore size than the cell-mounting front surface.

[0129] The fiber sheet structure of the present invention preferably has an average pore diameter of 5 to 123 μm, and more preferably 10 to 115 μm, on the cell-mounting surface. When the average pore diameter of the cell-mounting surface is within this range, cells can easily penetrate from the surface of the fiber sheet structure into the interior of the structure, and cells can be prevented from slipping through the mesh (pores), allowing cells to settle on the fiber sheet structure. The average pore diameter of the cell-mounting surface of the fiber sheet structure of the present invention can be measured by taking a 35x image (pixel count: 1920 × 1200) of a fiber sheet structure cut into a 5 cm square using a digital microscope (Hirox Corporation, RH-2000), then binarizing the image into pores and non-pores using the microscope's attached 2D measurement software "HRS-2D." The software then creates a histogram of pore diameters at 10 μm intervals from 60 to 300 μm. Using this histogram, the average pore diameter can be calculated using the following formula, using the class value and frequency: Average pore size (μm) = {(class value x frequency) total} ÷ (frequency total) In the fiber sheet structure of the present invention, the average pore size of the back surface on which cells are placed is preferably 5 to 115 μm, and more preferably 7 to 110 μm.

[0130] In the fiber sheet structure of the present invention, the proportion of pores of 150 μm or larger on the cell-mounting surface is preferably 35% or less, more preferably 25% or less, even more preferably 20% or less, and particularly preferably 15% or less. In this case, cells can be prevented from slipping through the mesh (pores), and the cells can be fixed on the fiber sheet structure. The proportion of pores of 150 μm or larger on the cell-mounting surface of the fiber sheet structure of the present invention can be calculated by dividing the total frequency of pores of 150 μm or larger in diameter by the total frequency of pores of 60 to 300 μm using the histogram used to calculate the average pore diameter described above.

[0131] The porosity of the fibrous sheet structure of the present invention is preferably 60 to 97%, more preferably 65 to 95%, even more preferably 70 to 93%, and particularly preferably 75 to 92%. If the porosity is less than 60%, the stretchability of the fibrous sheet structure will be significantly reduced, making it difficult to, for example, apply the fibrous sheet structure along the affected area. On the other hand, if the porosity is more than 97%, the pores will be too large, making it difficult to fix cells to the fibrous sheet structure. The method for measuring the porosity of the fibrous sheet structure of the present invention is the same as the method for measuring the porosity of the higher-order structure of the first embodiment described above.

[0132] The fiber sheet structure of the present invention has a knitted structure with 600 holes / mm 3 It is preferable that the value is 1.5×10 or more. 3 pieces / mm 3 It is preferable that the value is equal to or greater than 1.8×10 3 pieces / mm 3 It is preferable that the value is 2.1×10 or more. 3 pieces / mm 3 or more. In the above case, a large number of cells can be transported into the fiber sheet structure, and the cells can be efficiently fixed in the fiber sheet structure. The number of pores in the knitted structure of the fiber sheet structure of the present invention was calculated by the following formula using the average pore diameter and porosity determined above. Number of holes / mm3 = a × 0.01 ÷ (4 / 3 × 3.14 × (0.001 × b / 2) 3 ) a: Porosity (%) b: Pore diameter (μm) The fiber sheet structure of the present invention is a structure comprising two laminated layers, with the layer on the cell-mounting surface and the layer on the backside being knitted, preferably in a plain knit or jersey knit. Plain knit or plain knit fabrics have minimal irregularities on the fabric surface, resulting in high flatness and a smooth surface. Furthermore, a single-layer plain knit or jersey knit typically curls, resulting in a cylindrical sheet structure. In such cases, not only is it difficult to uniformly colonize cells on the fiber sheet structure, but handling is also poor. However, by laminating two layers, one with a convex upward curl and the other with a convex downward curl, the stress acting on each layer is similar, thereby suppressing curling. Suppressing curling not only enables uniform cell colonization on the fiber sheet structure, but also improves handling. Furthermore, laminating two layers increases the area for cell colonization and significantly reduces the frequency of cells slipping through the mesh, resulting in a fiber sheet structure with excellent cell culture properties.

[0133] The fiber sheet structure of the present invention is preferably a structure comprising three laminated layers, wherein the layer on the cell-mounting surface side is a knitted structure, the layer on the back side is a nonwoven fabric, and the intermediate layer between the surface and back side layers is a knitted structure, the knitted structure being a plain knit or plain knit, and the nonwoven fabric contains gelatin fibers. Nonwoven fabrics have no residual stress and do not curl, so by forming an intermediate layer between the surface and back side layers in a knitted structure, the stress acting on each layer is similar, thereby suppressing curling. Suppressing curling not only enables cells to be uniformly attached to the fiber sheet structure, but also improves handling. Furthermore, because nonwoven fabrics have an average pore size significantly smaller than knitted structures, cells that invade from the cell-mounting surface side can be retained within the fiber sheet structure, resulting in a fiber sheet structure with excellent cell culture properties.

[0134] The fiber sheet structure of the present invention is preferably a structure in which two layers are laminated, the layer on the cell-mounting surface side being a knitted structure and the layer on the back side being a nonwoven fabric, the knitted structure being a ribbed structure, and the nonwoven fabric containing gelatin fibers. Ribbed knitting does not curl because the front and back sides have the same structure. Nonwoven fabrics also do not curl, so structures with laminated nonwoven fabrics do not curl. This not only enables cells to be uniformly attached to the fiber sheet structure, but also improves handling. Because nonwoven fabrics have an average pore size significantly smaller than knitted structures, cells that invade from the cell-mounting surface side can be retained within the fiber sheet structure, resulting in a fiber sheet structure with excellent cell culture properties. Furthermore, compared to fiber sheet structures with two overlapping knitted layers, the single knitted structure allows for a thinner thickness.

[0135] The fiber sheet structure of the present invention is preferably a knitted structure made of rib knitting. In this case, since the rib knitting does not curl, it is possible to uniformly fix cells to the fiber sheet structure and also improves handling. Furthermore, compared to a fiber sheet structure made of two overlapping layers of knitted structures, the single layer of knitted structure has the advantage of being thinner.

[0136] The thickness of the fiber sheet structure of the present invention is preferably 30 to 5000 μm, more preferably 50 to 3000 μm, even more preferably 100 to 2000 μm, and particularly preferably 150 to 1000 μm. When the thickness is within the above range, the fiber sheet structure has high strength and is resistant to tearing. Furthermore, when used as a scaffold for cell culture, problems such as cell death due to oxygen deficiency near the center of the fiber sheet structure can be prevented. The thickness of the fiber sheet structure of the present invention can be measured by cutting a 3 cm square fiber sheet structure, attaching adhesive tape to the edges of the fiber sheet structure to fix it, and using a contact thickness meter.

[0137] The preferred range, measurement method, and control method for the weight loss rate when the fibrous sheet structure of the present invention is immersed in phosphate-buffered saline at 50°C for 4 hours are the same as the preferred range, measurement method, and control method for the weight loss rate when the high-order structure of the first embodiment described above is immersed in phosphate-buffered saline at 50°C for 4 hours.

[0138] The fiber sheet structure of the present invention contains gelatin fiber bundles, which gives it a texture similar to that of biological tissue in a wet state, making it more slippery than a fiber sheet structure made only of thermoplastic resin fiber bundles. Generally, fiber sheet structures made of thermoplastic resin fiber bundles are hydrophobic, which makes it extremely difficult to impregnate the fiber sheet structure with a cell culture medium. However, the fiber sheet structure of the present invention contains gelatin fiber bundles, which have excellent hydrophilicity, and therefore can easily impregnate and retain a cell culture medium, as well as diffuse body fluids containing oxygen and nutrients within the body, making it easy for cells to settle and proliferate within the fiber sheet structure.

[0139] The method for producing the fiber sheet structure of the present invention will be described below, but is not particularly limited.

[0140] The method for producing the fiber sheet structure of the present invention preferably includes the following steps 1 and 2, and steps 3-1 and 3-2, or step 3-3 and step 4-1 or 4-2.

[0141] (Step 1) A step of extruding a dope made of a gelatin solution containing 30 to 70% by weight of a gelatin raw material from a multi-hole spinneret into a fiber form at a temperature 1 to 15°C higher than the sol-gel transition temperature of the gelatin dope; (Step 2) A step of winding the extruded gelatin fibers onto a bobbin to prepare a gelatin fiber bundle precursor; (Step 3-1) a step of doubling the gelatin fiber bundle precursor with thermoplastic resin fibers and then texturing the doubling to prepare a second higher-order structure; (Step 3-2) a step of doubling the gelatin fiber bundle precursor with thermoplastic resin fibers, then texturing the resulting structure, and then laminating a gelatin nonwoven fabric thereon to produce a second laminated high-order structure; (Step 3-3) a step of insolubilizing the gelatin fiber bundle precursor, doubling it with thermoplastic resin fibers, and further organizing the resulting mixture to produce a second higher-order structure; (Step 4-1) a step of insolubilizing the gelatin contained in the second high-order structural body and the second laminated high-order structural body obtained in Steps 3-1 and 3-2, and then pressing the insolubilized gelatin to prepare a fibrous sheet structure; (Step 4-2) A step of pressing the second high-order structure obtained in Step 3-3 to produce a fiber sheet structure; It is preferable that the step 2 includes a conveying step of conveying the extruded gelatin fibers along the circumferential surface of a conveying roller before being wound onto a bobbin, and that the moisture content of the gelatin fibers when they reach the first conveying roller that the extruded gelatin fibers reach first is 5 to 25% by weight.

[0142] The moisture content of the gelatin fiber bundle precursor is preferably 5 to 20% by weight.

[0143] The step 2 includes a step of adhering a mixed solution of at least one selected from ethylene glycol, polyethylene glycol, and glycerin with a lower alcohol to the extruded gelatin fibers before winding them onto a bobbin.

[0144] In the step 1, it is preferable that the gelatin has a jelly strength of 100 to 350 g and the gelatin dope has a sol-gel transition temperature of 15 to 60°C.

[0145] The fiber sheet structure of the present invention can be produced by extruding a dope made of a gelatin solution into fibers through a multi-hole spinneret, winding the extruded gelatin fibers onto a bobbin to produce gelatin fiber bundle precursors, doubling the gelatin fiber bundle precursors with thermoplastic resin fibers and then texturing the resulting second high-order structure, or by laminating a nonwoven fabric on the second high-order structure to produce a second laminated high-order structure, and then pressing the resulting second high-order structure to produce a fiber sheet structure. Alternatively, as described above, the fiber sheet structure may be produced by pressing a second high-order structure obtained by doubling pre-insolubilized gelatin fiber bundle precursors with thermoplastic resin fibers and then texturing the resulting second high-order structure.

[0146] Texturing refers to the process of producing a woven fabric, knitted fabric, or braided cord from a bundle of yarns.

[0147] The gelatin raw material constituting the gelatin solution in the fiber sheet structure of the present invention is obtained by unwinding the triple helix of collagen derived from bovine bone, bovine hide, pigskin, bird, or fish, resulting in a single molecular chain. Methods for producing such gelatin raw materials include acid treatment and lime treatment. The gelatin raw material in the fiber sheet structure of the present invention may be gelatin raw material produced by either method, or may be commercially available gelatin raw material. Commercially available gelatin raw materials undergo various purification steps before extraction during their production process, resulting in low levels of components other than protein. Typically, they have a composition of 85% or more protein, 8-14% water, 2% or less ash, and 1% or less other components (e.g., lipids, polysaccharides). The present invention can also use such common gelatin raw materials. Because gelatin raw material is a thermally denatured form of collagen, its amino acid composition is nearly identical to that of collagen, but it is highly unique compared to other proteins, with glycine accounting for approximately one-third of the total and one-third of the amino acid repeats. Collagen and gelatin can be distinguished, for example, by observing the signal at around 31.5 degrees obtained by wide-angle X-ray measurement. This 31.5-degree signal is derived from the triple helix structure of collagen, and when the triple helix structure that characterizes collagen is unraveled and becomes gelatin, this signal disappears.

[0148] Furthermore, although there are no particular limitations on the molecular weight of the gelatin raw material, the jelly strength, which is highly correlated with the molecular weight, is preferably 100 to 350 g, more preferably 150 to 320 g, and even more preferably 220 to 310 g, from the viewpoint of spinnability. The jelly strength is determined by cooling a 6.67% gelatin aqueous solution at 10°C for 17 hours, and measuring the load (g) required to press down 4 mm on the surface of the prepared gelatin solution with a half-inch (12.7 mm) diameter plunger using a small benchtop tester EZ-SX manufactured by Shimadzu Corporation.

[0149] When the jelly strength of the gelatin raw material is within the above range, a significant decrease in the spinnability of the gelatin fiber can be prevented, and further, by suppressing the moisture retention rate in the fiber, thread breakage during winding can be prevented.

[0150] The content of the gelatin raw material in the gelatin solution is preferably 30 to 70% by weight, more preferably 40 to 60% by weight. When the content of the gelatin raw material in the gelatin solution is within the above range, a significant decrease in the spinnability of the gelatin fiber can be prevented, and further, bubbles generated in the process of producing the gelatin solution can be easily degassed, preventing thread breakage during spinning.

[0151] The solvent for dissolving the gelatin raw material is water, but (polyhydric) alcohols, dimethyl sulfoxide, etc. may be added to adjust the viscosity as needed.

[0152] The sol-gel transition temperature of the gelatin solution is preferably 15 to 60° C., more preferably 20 to 60° C., even more preferably 20 to 55° C., and particularly preferably 20 to 50° C. The sol-gel transition temperature is measured using, for example, an ARES rheometer manufactured by TA Instruments.

[0153] When the sol-gel transition temperature is within the above range, the gelatin fiber is prevented from becoming too sticky, the handling property during production is improved, and furthermore, adhesion of wound gelatin fibers can be prevented. Also, thermal decomposition of gelatin at the spinning temperature, which causes breakage of fibers, can be prevented.

[0154] Gelatin fiber bundle precursors are produced by extruding a dope consisting of gelatin raw material and a solvent such as water into the air through a multi-hole spinneret in the form of fibers, and by stretching the dope just below the spinneret to appropriately orient the molecular chains of the unwound collagen triple helix molecules and by appropriately controlling the water content within the fibers. By controlling the degree of orientation of the molecular chains of the unwound collagen triple helix molecules and the water content within the fibers, it is possible to increase the tensile strength and breaking elongation of the yarn while suppressing adhesion between the fibers.

[0155] The spinning method in which the dope is extruded into the air in the form of fibers from a multi-hole spinneret may be any of a dry method, a semi-dry method, and a wet method, but dry production is preferred because it can prevent the formation of voids on the surface or inside of the fiber during the process of drying and removing the solvent, and can suppress a decrease in the tensile strength and breaking elongation of the gelatin fiber. The dry spinning temperature is preferably 1 to 25°C higher, and more preferably 5 to 20°C higher, than the sol-gel transition temperature of the dope. Within the above range, a significant decrease in spinnability can be prevented.

[0156] In the production of the gelatin fiber bundle precursor used in the present invention, it is preferable to rapidly reduce the moisture content in the fiber to the range of 5 to 25% by weight immediately after spinning. If the moisture content in the fiber is within the above range, adhesion can be suppressed, and adhesion between gelatin fibers discharged from a multi-hole spinneret and sticking of gelatin fibers to rollers during the production process can be prevented, and the gelatin fiber precursor wound around a bobbin can be easily unwound from the bobbin. Furthermore, a significant decrease in the elongation of the yarn can be suppressed, and yarn breakage can be prevented during the process of producing a gelatin fiber bundle and the process of producing a fiber sheet structure by rewinding it from the bobbin.

[0157] The method may include a conveying step of conveying the gelatin fibers extruded from the spinneret along the circumferential surface of a conveying roller before winding the gelatin fibers onto a bobbin.

[0158] The moisture content of the gelatin fiber when it first reaches the first conveying roller is preferably 5 to 25% by weight, more preferably 5 to 20% by weight. The moisture content is measured by winding the gelatin thread around the first conveying roller, measuring 0.5 g of the wound fiber, and using a Karl Fischer moisture content meter (EV-2010 manufactured by Hiranuma Co., Ltd.) at 150°C in a N2 atmosphere.

[0159] When the moisture content is within the above range, it is possible to prevent the gelatin fibers from sticking to the transport roller, and also possible to suppress a significant decrease in the elongation of the yarn, thereby preventing yarn breakage.

[0160] The moisture content can be controlled by drying with dry air or dry hot air.

[0161] In addition, in order to prevent adhesion due to contact between the fibers, it is preferable to use a grooved guide roller as the transport roller.

[0162] The moisture content of a gelatin fiber bundle precursor obtained by winding gelatin fibers on a bobbin is preferably 5 to 20% by weight, more preferably 5 to 15% by weight. The moisture content is measured by measuring 0.5 g of the fiber bundle precursor wound on a bobbin using a Karl Fischer moisture content meter (EV-2010 manufactured by Hiranuma Corporation) at 150°C in a N2 atmosphere.

[0163] When the moisture content is within the above range, the gelatin fiber precursor can be easily unwound from the bobbin, and a significant decrease in the elongation of the thread can be suppressed, thereby preventing thread breakage during the process of rewinding the thread from the bobbin to produce a fiber sheet structure.

[0164] The moisture content can be controlled by drying with dry hot air, etc. After passing through the first transport roller, the fiber bundle can be dried as needed with a winder.

[0165] The gelatin fiber bundle used in the present invention is preferably produced at a spinning draft (discharge linear velocity / winding speed) in the range of 0.01 to 2, more preferably in the range of 0.05 to 1.5. Within the above range, the orientation of the triple helix molecules of the unwound collagen is sufficient, preventing a decrease in tensile strength, and preventing the fiber diameter from becoming too thick. The moisture content of the gelatin fibers can be sufficiently reduced before they reach the first conveying roller, and as a result, the gelatin fibers can be prevented from sticking to the roller. Furthermore, a significant decrease in breaking elongation can be prevented, preventing thread breakage during the process of producing the gelatin fiber bundle and the process of producing a fiber sheet structure by rewinding the fibers from the bobbin.

[0166] The method may include a step of applying an oil to the gelatin fibers extruded from the spinneret before winding them onto a bobbin. It is preferable to apply an oil to the fiber surface after the moisture content within the fiber reaches a range of 5 to 20% by weight. Applying an oil to the fiber surface allows multiple gelatin fibers to be bundled together and handled as a gelatin fiber bundle. The application of an oil significantly improves the handleability of the yarn during the gelatin fiber bundle production process and the process of rewinding the fiber from the bobbin to produce a fiber sheet structure. Since the fiber sheet structure of the present invention is used as a medical material, it is preferable to use a biocompatible oil, such as ethylene glycol, polyethylene glycol, or glycerin. These compounds are preferably diluted with a lower alcohol, such as ethanol, and applied to the fiber surface as a mixed solution, followed by drying to remove the lower alcohol. The oil may be removed by washing after the fiber sheet structure is produced, or it may be left in the applied state. There is no restriction on the amount of oil to be applied as long as it is an amount that can bundle a plurality of gelatin fibers into a fiber bundle, but for example, 0.5 to 5% by weight is preferred.

[0167] The cross-sectional shape of gelatin fibers can be any shape. Examples of cross-sectional shapes include solid circle, hollow, flat, star, triangular, solid circle + fin, hollow + fin, etc. When used as a 3D cell culture scaffold, irregular cross-section threads such as flat, star, or triangular cross-sections may be preferable to solid circle cross-sections.

[0168] The tensile strength of the gelatin fiber is preferably 0.5 to 3 cN / dtex, more preferably 0.7 to 2.8 cN / dtex, and even more preferably 1.0 to 2.5 cN / dtex. The tensile strength of the gelatin fiber is measured by taking out a single yarn from the gelatin fiber bundle precursor and using, for example, Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.).

[0169] The breaking elongation of the gelatin fiber is preferably 30 to 250%, more preferably 40 to 200%, and even more preferably 50 to 150%. The breaking elongation of the gelatin fiber is measured by taking a single yarn from a gelatin fiber bundle and using, for example, Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.).

[0170] When the tensile strength and breaking elongation of the gelatin fiber are within the above ranges, the fiber can withstand the production of gelatin fiber bundles and the production of fiber sheet structures.

[0171] The process of insolubilizing the gelatin fiber bundle precursor may involve insolubilizing the gelatin fiber bundle precursor to produce a gelatin fiber bundle, or it may involve doubling and assembling the fiber bundle precursor and thermoplastic resin fiber, followed by insolubilization to produce a fiber sheet structure made of gelatin fiber bundles. The insolubilization (treatment to make the fiber bundle insoluble in water) may be performed by any of thermal crosslinking, chemical crosslinking using a crosslinking agent, or physical crosslinking using ultraviolet light, radiation, or electron beams, or a combination of these methods. Thermal crosslinking may be performed in the atmosphere or in a vacuum. The temperature during thermal crosslinking is preferably in the range of 110 to 200°C, more preferably 120 to 190°C, and even more preferably 130 to 180°C. Temperatures below 100°C result in insufficient crosslinking, causing gelatin to dissolve in water in a wet state and making it unusable as a scaffold. Temperatures above 200°C are undesirable because the gelatin thermally decomposes, significantly reducing fiber strength. The degree of crosslinking can be changed as needed by adjusting the heat treatment temperature and time. The heat treatment time is preferably 3 to 72 hours, with a range of 12 to 50 hours being preferable from the viewpoint of productivity. In the case of chemical crosslinking using a crosslinking agent, voids may form in the fibers during the washing process to remove the crosslinking agent from the fibers, resulting in a decrease in the tensile strength and elongation at break of the gelatin fibers. In this case, breakage of the fibers may occur during the process of preparing a fiber sheet structure from the insolubilized gelatin fiber bundles. Therefore, when performing insolubilization treatment by chemical crosslinking, it is preferable to perform the chemical crosslinking treatment after organizing the fiber bundle precursor. Examples of crosslinking agents used in chemical crosslinking include glutaraldehyde and hexamethylene diisocyanate.

[0172] The tensile strength and breaking elongation of insolubilized gelatin fibers are measured by pulling out a single yarn from a gelatin fiber bundle obtained by insolubilizing a gelatin fiber bundle precursor, and measuring this single yarn using, for example, Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.). The breaking elongation of the insolubilized single yarn is preferably 30 to 250%, more preferably 40 to 200%, and even more preferably 50 to 150%. When the tensile strength and breaking elongation of the insolubilized single yarn are within the above ranges, it can withstand the production of a fiber sheet structure.

[0173] The thermoplastic resin fibers in the fiber sheet structure of the present invention can be produced by melt spinning, and commercially available thermoplastic resin fiber bundles can also be purchased and used.

[0174] The doubling bundle in the fiber sheet structure of the present invention can be produced from a doubling bundle precursor comprising a gelatin fiber bundle precursor and a thermoplastic resin fiber bundle as a starting material. The doubling bundle precursor comprising a gelatin fiber bundle precursor and a thermoplastic resin fiber bundle can be produced by putting a plurality of fiber bundle precursors into a doubling machine.

[0175] The gelatin fiber bundle precursor may be twisted while spirally winding a thermoplastic resin fiber bundle around the gelatin fiber bundle precursor, or the gelatin fiber bundle precursor may be twisted while spirally winding a gelatin fiber bundle precursor around the thermoplastic resin fiber bundle.

[0176] The gelatin fiber bundle precursor having the oil agent attached thereto and the thermoplastic resin fiber bundle may be combined by twisting or the like, or the fiber bundles may be entangled by interlacing or the like.

[0177] Alternatively, a plurality of bobbins of gelatin fiber bundle precursors and a plurality of bobbins of thermoplastic resin fiber bundles may be set in a knitting machine, and these gelatin fiber bundle precursors and thermoplastic resin fiber bundles may be combined in the process of conveying them to the needles of the knitting machine.

[0178] A doubling yarn composed of a gelatin fiber bundle precursor and a thermoplastic resin fiber bundle may be composed of pre-insolubilized gelatin fiber bundles and thermoplastic resin fiber bundles. After producing the doubling yarn bundle, a second high-order structure can be produced by organizing it. A second laminated high-order structure may be produced by laminating a nonwoven fabric on this second high-order structure. For example, when laminating a gelatin or collagen nonwoven fabric, an example method is to organize the second high-order structure and then laminate the nonwoven fabric on the second high-order structure by electrospinning or the like. The laminated gelatin or collagen nonwoven fabric can be made insoluble in water by crosslinking.

[0179] The second higher-order structures can be produced, for example, using Shimadzu Corporation's WHOLEGARMENT (registered trademark). The gauge is preferably in the range of 5 to 20 gauge. If the gauge is less than 5, the fineness of the doubling yarn bundle must be high, which clogs the mesh of the second higher-order structures and inhibits cell penetration into the fiber sheet structure from the cell-mounting surface. On the other hand, if the gauge is more than 20, the fineness of the doubling yarn bundle must be low, which weakens the strength of the doubling yarn bundle and can lead to thread breakage during production of the second higher-order structures. For this reason, a range of 10 to 20 gauge, and even more preferably 13 to 18 gauge, is most preferred.

[0180] The second higher-order structure may be a single-knit fabric consisting of one layer (sheet), or a double-knit fabric consisting of two laminated layers. A double-knit fabric consisting of two laminated layers can be produced, for example, by knitting the two layers separately using Shimadzu Corporation's WHOLEGARMENT (registered trademark) and then knitting them together at the same time.

[0181] The knitted fabric for the second higher-order structure is preferably plain knit, flat knit, or rib knit. Plain knit or flat knit fabrics have minimal irregularities on the fabric surface, resulting in high flatness and a smooth surface, similar to that of biological tissue. However, curling can cause the sheet structure to become cylindrical, making it difficult to uniformly colonize cells on the fiber sheet structure and also making it difficult to handle. For this reason, it is preferable to knit two layers: a plain knit or flat knit sheet that curls upward and a plain knit or flat knit sheet that curls downward, thereby creating a laminated structure of two layers that exert similar stresses on each other and suppress curling. Furthermore, stacking the two layers increases the surface area for cell colonization and significantly reduces the frequency of cells slipping through the mesh, resulting in a fiber sheet structure with excellent cell culture properties. Furthermore, by layering nonwoven fabric, which has an average pore size significantly smaller than that of knitted fabric, it becomes possible to retain more cells that invade from the cell-mounting surface side within the fiber sheet structure, resulting in a fiber sheet structure with excellent cell culture properties.

[0182] Rib knitting does not curl because the front and back are the same weave, but it has more unevenness on the fabric surface than plain knitting or jersey knitting. However, the pressing process used in the fabric sheet structure production process can eliminate the unevenness on the fabric surface, giving it a smooth surface and a slipperiness similar to that of biological tissue. Because rib knitting does not curl, cells can be uniformly attached to the fabric sheet structure. For this reason, it is not necessary to have two layers, but by layering a nonwoven fabric, which has an average pore size significantly smaller than that of knitted fabric, it is possible to retain more cells that invade from the cell-mounting surface side within the fabric sheet structure. Furthermore, compared to a fabric sheet structure with two layers of knitted fabric, the thickness of the fabric sheet structure can be made thinner because it is a single layer of knitted fabric, resulting in a softer texture.

[0183] The average pore size of the second higher-order structures used to prepare the fibrous sheet structure is preferably in the range of 20 to 200 μm. The fibrous sheet structure is produced by pressing one side of the second higher-order structures or the second laminated higher-order structures (nonwoven fabric side) while applying a temperature of 40 to 100°C. The press treatment crushes the mesh on both the front and back sides of the second higher-order structures, but the mesh is crushed more on the side heated to 40 to 100°C than on the side not heated, resulting in an asymmetric fibrous sheet structure with a back side having a smaller average pore size than the cell-mounting surface. When the average pore size of the second higher-order structures is in the range of 20 to 200 μm, a fibrous sheet structure with excellent cell culture properties can be obtained by press treatment, with an average pore size of 5 to 123 μm on the cell-mounting surface and 35% or less of the cell-mounting surface having pores of 150 μm or larger. If the average pore size of the second higher-order structures is less than 20 μm, the mesh of the fibrous sheet structure will be blocked by the press treatment, inhibiting cell penetration from the cell-mounting surface into the interior of the fibrous sheet structure, while if it exceeds 200 μm, the mesh will not be sufficiently crushed by the press treatment, causing cells to slip through the mesh of the fibrous sheet structure. The average pore size of the second higher-order structures is preferably in the range of 25 to 150 μm, and more preferably 30 to 130 μm.

[0184] The fibrous sheet structure of the present invention has a cell-supporting surface and a back surface, and the average pore size of the back surface is smaller than that of the cell-supporting surface, making it an asymmetrical fibrous sheet structure on both sides. Such a bilaterally asymmetrical fibrous sheet structure can be produced, for example, by washing off any oil or knitting machine oil adhering to the second high-order structure or the second laminated high-order structure, and then pressing one side of the second high-order structure or the nonwoven fabric side of the second laminated high-order structure while applying a temperature of 40 to 100°C. While the reason for this is unclear, it is presumed that the removal of the oil or knitting machine oil reduces the convergence of the fiber bundles, and the difference in thermal linear expansion between the gelatin fiber and the thermoplastic resin fiber further unravels the fiber bundles, causing them to widen during pressing. This method can be used to produce a bilaterally asymmetrical fibrous sheet structure having a cell-supporting surface and a back surface, in which the average pore size of the back surface is smaller than that of the cell-supporting surface. Examples of a device for pressing a fiber sheet structure by applying heat to only one side include a temperature-modulatable hydraulic press and a calender roll.

[0185] The fiber sheet structure produced by the present invention may be immersed in, for example, a 20 to 80% aqueous glycerin solution, which can produce a medical material with a moist texture and better conformability to the affected area.

[0186] The fiber sheet structure of the present invention may contain an additive. Examples of additives include polyacids such as (anhydrous) citric acid and (anhydrous) maleic acid, magnetic particles such as γ-iron oxide, inorganic substances such as hydroxyapatite, endogenous proteins that promote cell proliferation and differentiation, collagen, etc. These additives may be coated onto the fiber sheet structure, onto the gelatin fiber bundles, gelatin fiber bundle precursors, or gelatin fibers, or may be added to the gelatin raw material. <Characteristics of fiber sheet structure> The fiber sheet structure of the present invention is excellent in texture, slipperiness, cell adhesiveness, and cell culturing properties.

[0187] The texture of the fiber sheet structure of the present invention can be evaluated by the feel when touching the fiber sheet structure with dry hands. The texture was evaluated by pinching both ends of a fiber sheet structure cut into a 5 cm square with both hands and pulling it, or by pulling one pinched end upward and the other downward three times. Moderate elasticity is necessary because a lack of elasticity tends to result in a stiff texture, making it difficult to conform to biological tissue.

[0188] The slipperiness of the fiber sheet structure of the present invention can be evaluated using a friction tester (model: KES-SE) manufactured by Kato Tech Co., Ltd. After immersing a fiber sheet structure cut into a 5 cm square in distilled water for 1 hour, the sample was fixed on a measuring table with a metal frame, and a 10 mm square silicon sensor was moved at 1.0 mm / s under a load of 50 g to measure the average coefficient of friction and the average deviation of the coefficient of friction.

[0189] The average coefficient of friction of the fiber sheet structure of the present invention is preferably 0.05 to 0.60, more preferably 0.10 to 0.50, even more preferably 0.15 to 0.45, and most preferably 0.20 to 0.40. Within the above range, the fiber sheet structure has slip properties similar to those of living tissue, and is less likely to cause inflammation when rubbed against living tissue.

[0190] The mean deviation of the coefficient of friction of the fiber sheet structure of the present invention is preferably 0.40 to 1.60, more preferably 0.45 to 1.45, even more preferably 0.50 to 1.40, and most preferably 0.55 to 1.35. Within the above ranges, the fiber sheet structure of the present invention has softness and slipperiness similar to that of living tissue in a wet state. Therefore, it can be suitably used as a material for wound and burn treatment, a matrix material for artificial skin, etc., and is preferred because it is less likely to cause inflammation when rubbed against living tissue.

[0191] The fiber sheet structure of the present invention has excellent cell adhesion for cell fixation. Cell adhesion and cell culturing ability are strongly correlated; strong cell adhesion allows cells to efficiently fixate on the fiber sheet structure, resulting in excellent cell culturing ability. On the other hand, weak cell adhesion tends to prevent cells from successfully fixing to the fiber sheet structure, resulting in poor cell culturing ability. Cell culturing ability can be evaluated by statically culturing NIH3T3 cells on a 24-well plate for 7 days, adding 100 μL of WST-1, leaving the cells in a CO2 incubator (37°C, CO2 concentration 5%) for 3 hours, transferring 300 μL to a 96-well plate, and measuring absorbance (450 nm, reference wavelength 630 nm) using a plate reader (VERSA Max) to obtain the number of cells cultured. The number of cells cultured is 10 × 10 4 cells / mL or more is preferred, and 20 x 10 4 cells / mL or more, and even 25×10 4 More preferably, it is more than cells / mL.

[0192] Gelatin is a biocompatible material (low antigenicity and high bioabsorbability), making it suitable for use as a scaffold for 3D cell culture, which is excellent for promoting cell differentiation, enhancing cell function, and providing excellent adhesion after transplantation. Furthermore, the fiber sheet structure of the present invention has softness and slipperiness similar to that of living tissue in a wet state. Therefore, it can be used favorably as a material for wound and burn treatment, a matrix material for artificial skin, and other applications, and is preferred because it is less likely to cause inflammation when rubbed against living tissue.

[0193] The cell adhesion of the fiber sheet structure can be evaluated by statically culturing NIH3T3 cells on the structure for 7 days, observing the fluorescently labeled cells under a fluorescence microscope, and observing the degree of cell adhesion.

[0194] The fiber sheet structure of the present invention does not curl, allowing cells to be uniformly fixed therein and also providing excellent handling properties. The presence or absence of curling was measured by punching a hole in the fiber sheet structure with a hole punch to prepare a circular sheet with a diameter of 14 mm, immersing the sheet in a beaker containing phosphate-buffered saline at 50°C for 4 hours, and visually inspecting the sheet for curling. [Example]

[0195] The fiber sheet structure of the present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the fiber sheet structure of the present invention should not be construed as being limited by the specific examples shown below. <Measurement and evaluation methods> The measurement and evaluation methods used in the examples and comparative examples are as follows. [Fiber fineness] The fineness of the thermoplastic resin fiber bundle was measured in an atmosphere of 20±2°C and 65±2% relative humidity using an auto-blow type fineness measuring instrument, Denier Computer DC-77A (manufactured by Search Co., Ltd.), with N=3, and the average value was used as the fineness. The fineness of the thermoplastic resin fiber was calculated by dividing the fineness of the thermoplastic resin fiber bundle by the number of thermoplastic resin fibers constituting the fiber bundle.

[0196] The gelatin fiber bundle precursor or gelatin fiber bundle was cut to 100 mm, and the weight was measured with an electronic balance (Mettler Toledo XP6V) with N = 3, and the average value was converted to dtex to obtain the fineness. The fineness of the gelatin fiber was calculated by dividing the fineness of the gelatin fiber bundle precursor or the fineness of the gelatin fiber bundle by the number of gelatin fibers that make up the fiber bundle. [Mechanical strength of fiber] The mechanical strength of gelatin fibers and insolubilized gelatin fibers was measured using a Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.) with N = 5. The tensile speed was 20 mm / min, and the distance between chucks was 50 mm, and the tensile strength and breaking elongation of the gelatin fibers were measured. [Mechanical strength of fiber bundles and doubling bundles] The mechanical strength of the gelatin fiber bundle or doubled yarn bundle was measured using a Tensilon (RTC-1210A manufactured by Orientec Co., Ltd.) with N = 5. The pulling speed was 20 mm / min, and the distance between chucks was 50 mm, and the tensile strength and breaking elongation of the gelatin fiber bundle or doubled yarn bundle, as well as the upper yield stress and lower yield stress of the gelatin fiber bundle were measured. [Weight loss rate of gelatin fiber bundle and doubling bundle] The weight of a 100 mm gelatin fiber bundle or ply bundle was measured, wrapped in a 10 μm membrane filter, and immersed in phosphate-buffered saline at 50°C for 4 hours. Next, the membrane filter containing the gelatin fiber bundle or ply bundle was removed from the phosphate-buffered saline and immersed in room temperature water for 30 minutes. The water was then absorbed with a Kimtowel, and the membrane filter containing the gelatin fiber bundle or ply bundle was dried at 80°C for 24 hours, after which the fiber bundle was removed from the membrane filter and its weight was measured. The weight loss rate was calculated using the following formula. This procedure was performed with N=3, and the average value was taken as the weight loss rate.

[0197] Weight loss rate [%] = 100 - [100 × (weight after immersion)] / (weight before immersion) [Weight loss rate of high-order structure, laminated high-order structure, and fiber sheet structure] High-order structure, laminated high-order structure or fiber sheet structure 25cm 2 The weight of each sample was measured, wrapped in a 10 μm membrane filter, and immersed in phosphate-buffered saline at 50°C for 4 hours. The membrane filter containing the high-order structure, laminated high-order structure, or fiber sheet structure was removed from the phosphate-buffered saline and immersed in room temperature water for 30 minutes. The water was then absorbed with a Kimtowel, and the membrane filter containing the high-order structure, laminated high-order structure, and fiber sheet structure was dried at 80°C for 24 hours. The high-order structure, laminated high-order structure, or fiber sheet structure was removed from the membrane filter and its weight was measured. The weight loss rate was calculated using the following formula. This procedure was performed three times, and the average value was taken as the weight loss rate.

[0198] Weight loss rate [%] = 100 - [100 × (weight after immersion)] / (weight before immersion) [Thickness of high-order structure, laminated high-order structure, and fiber sheet structure] Adhesive tape was applied to the edges of a 3 cm square cut out piece of a high-order structure, laminated high-order structure, or fiber sheet structure to fix the high-order structure, laminated high-order structure, or fiber sheet structure, and the thickness was measured using a contact-type thickness meter (LITEMATIC V L-50, manufactured by Mitutoyo Corporation). A cylindrical terminal with a diameter of 5 mm was used as the measurement terminal, and the terminal was adjusted so that a load of 7 g was applied during measurement. The thickness of the high-order structure, laminated high-order structure, or fiber sheet structure was measured at any five points, and the average value was taken as the thickness of the high-order structure, laminated high-order structure, or fiber sheet structure. [Average pore diameter of high-order structures, laminated high-order structures, and fiber sheet structures] The average pore diameter on the cell-mounting surface was measured by obtaining a 35x image (pixel count: 1920 x 1200) of a 5cm square cut-out of a high-order structure, laminated high-order structure, or fiber sheet structure using a digital microscope (Hirox Corporation, RH-2000). The image was then binarized using the microscope's attached 2D measurement software "HRS-2D" to separate the image into pores and non-pores. The software then created a histogram of pore diameters at 10μm intervals from 60 to 300μm. Using this histogram and the class value and frequency, the average pore diameter was calculated using the following formula.

[0199] Average pore size (μm) = {(class value x frequency) total} ÷ (frequency total) [Proportion of pores of 150 μm or larger on the cell-mounting surface of high-order structures, laminated high-order structures, and fiber-sheet structures] The percentage of pores 150 μm or larger on the cell-mounting surface of a high-order structure, a laminated high-order structure, or a fiber sheet structure was calculated by dividing the total frequency of pores 150 μm or larger in diameter by the total frequency of pores 60 to 300 μm using the histogram used to calculate the average pore diameter described above. [Porosity of High-Order Structure, Laminated High-Order Structure, and Fiber Sheet Structure] The porosity was calculated using the following formula by measuring the thickness and weight of a high-order structure, a laminated high-order structure, or a fiber sheet structure cut into a 5 cm square.

[0200] Porosity (%)=100×[1-a÷{(b+c)÷(b÷d+c÷e)}÷(f×25)] a: Weight (g) of the high-order structure, laminated high-order structure, or fiber sheet structure cut into a 5 cm square b: Fineness of gelatin fiber bundle (dtex) c: thermoplastic fiber bundle fineness (dtex) d: Gelatin fiber bundle density (g / cm 3 ) e: Thermoplastic fiber bundle density (g / cm 3 ) f: Thickness of the high-order structure, laminated high-order structure, or fiber sheet structure (cm) The gelatin fiber bundle density is 1.27 g / cm 3 , thermoplastic fiber bundle density of polyglycolic acid fiber bundle density of 1.53 g / cm 3 , polylactic acid fiber bundle density 1.25g / cm 3 In addition, when the higher-order structure is produced using only gelatin fiber bundles without using thermoplastic fiber bundles, the above c and e are not included in the calculation. [Number of pores in high-order structures, laminated high-order structures, and fiber sheet structures] The number of pores in the high-order structural body, the laminated high-order structural body, or the fiber sheet structure was calculated by the following formula using the average pore diameter and porosity determined above. Number of holes / mm3 = a × 0.01 ÷ (4 / 3 × 3.14 × (0.001 × b / 2) 3 ) a: Porosity (%) b: Pore diameter (μm) [Swelling ratio of gelatin fiber bundles] The fiber diameter of the gelatin fibers constituting the gelatin fiber bundle was measured using a HIROX RH2000 optical microscope. Next, 10 to 30 mm of the gelatin fiber bundle was immersed in phosphate buffered saline at 50°C for 4 hours, and then the gelatin fiber bundle was pulled out of the phosphate buffered saline, and the fiber diameter of the gelatin fibers constituting the gelatin fiber bundle in a wet state was measured. The swelling ratio was calculated using the following formula. This operation was performed with N=3, and the average value was taken as the swelling ratio.

[0201] Swelling ratio [%] = 100 × (fiber diameter after immersion) / (fiber diameter before immersion) [Swelling rate of doubled yarn bundle] The bundle diameter of the doubled yarn bundle was measured using a HIROX RH2000 optical microscope. Next, 10 to 30 mm of the doubled yarn bundle was immersed in phosphate buffered saline at 50°C for 4 hours, and then the doubled yarn bundle was removed from the phosphate buffered saline and the fiber diameter of the doubled yarn in a wet state was measured. The swelling ratio was calculated using the following formula. This procedure was performed three times, and the average value was taken as the swelling ratio.

[0202] Swelling rate [%] = 100 × (diameter of the doubled yarn bundle after immersion) / (diameter of the doubled yarn bundle before immersion) [Moisture content of fiber bundle precursor] 0.5 g of fiber bundle precursor wound on a bobbin is weighed and measured using a Karl Fischer moisture content meter (HIRANUMA EV-2010) at 150°C in a N2 atmosphere. [Moisture content of gelatin fiber when it reaches the transport roller] The gelatin thread is wound around the first transport roller, and 0.5 g of the wound fiber is measured using a Karl Fischer moisture content meter (HIRANUMA EV-2010) at 150°C in a N2 atmosphere. [Jelly Strength] A 6.67% gelatin solution was cooled at 10°C for 17 hours. Next, using a small benchtop tester EZ-SX manufactured by Shimadzu Corporation, the load (g) required to press down the surface of the prepared jelly by 4 mm with a plunger having a diameter of 1 / 2 inch (12.7 mm) was determined as the jelly strength. [Sol-gel transition temperature] The temperature dependence of viscoelasticity of the gelatin dope was measured using a TA Instruments ARES rheometer when the temperature was raised at 1 K / min in the temperature range of 20-70°C, and the temperature at which the relationship between the storage modulus and loss modulus reversed was determined as the sol-gel transition temperature. [Texture of high-order structures, laminated high-order structures, and fiber sheet structures] The texture was evaluated by sensory evaluation of the feel of the high-order structure, the laminated high-order structure, or the fiber sheet structure with a dry hand. ◎:Stretchy and soft texture ◯: The obtained structure had lost its elasticity, but by immersing it in a 60% glycerin aqueous solution, it regained its elasticity and moist texture. △: Elastic but rough texture ×: Structure could not be produced and texture was hard [Average friction coefficient and average deviation of friction coefficient for high-order structures, laminated high-order structures, and fiber sheet structures] The average coefficient of friction and the average deviation of the coefficient of friction of the high-order structure, laminated high-order structure, or fiber sheet structure were evaluated using a Kato Tech friction tester (model number: KES-SE). After immersing 5 cm square pieces of the high-order structure, laminated high-order structure, or fiber sheet structure in distilled water for 1 hour, the sample was fixed to a metal frame on a measuring table and a 10 mm square silicon sensor was run over it at 1.0 mm / s with a 50 g load to measure the average coefficient of friction and the average deviation of the coefficient of friction. This procedure was repeated N=3, after which the sample was rotated 90° and the same procedure was repeated. The range of the surface friction coefficient (minimum and maximum values) and the range of the average deviation of the coefficient of friction (minimum and maximum values) were measured. [Curl measurement of high-order structures, laminated high-order structures, and fiber sheet structures] The high-order structure, laminated high-order structure, or fiber sheet structure was punched out with a hole punch to produce a circular sheet with a diameter of 14 mm. The sheet was then immersed in a beaker containing phosphate-buffered saline at 50°C for 4 hours, and the presence or absence of curling was visually inspected and evaluated. [Evaluation of cell culture numbers on fiber sheet structures] Cell culture of the higher-order structures, laminated higher-order structures, and fiber-sheet structures was carried out using NIH3T3 cells according to the procedure below, and the cell count after 7 days of cell culture was evaluated by WST-1 measurement. First, the fiber-sheet structures were punched out with a 14 mm diameter punch, wrapped in an aluminum pack, and sterilized with electron beam. The sterilized fiber-sheet structures were placed on an MPC-coated 24-well plate with the cell-mounted surface facing up, and 1 mL of phosphate-buffered saline was added and left to stand for 10 minutes to allow the fiber-sheet structures to swell. After swelling, the phosphate-buffered saline was removed using a 1000 mL pipette, and 1.5 x 10 4 1 mL of a cell suspension at 1.5 x 10 cells / mL was seeded. The cell suspension was prepared using the following procedure. The medium was removed from a T225 flask in which cells had previously been cultured in a CO2 incubator (37°C, CO2 concentration 5%), and the flask was washed twice with 22.5 mL of phosphate-buffered saline. 22.5 mL of 0.25% trypsin was then added and the flask was left to stand in the CO2 incubator for 5 minutes. After confirming detachment under a microscope, the cells were collected in a centrifuge tube. After washing with 22.5 mL of medium, the flask was centrifuged (220 g for 3 minutes) and the supernatant was removed. The obtained cell pellet was loosened with medium, and the cell count was measured using a Muse cell analyzer (0500-3115). The cell concentration was found to be 1.5 x 10 4 The cell suspension was adjusted to 1000 cells / mL. The medium was prepared by adding 53 mL of FBS, 1 / 1000 volume of kanamycin, and 1 / 100 volume of a penicillin-spretomycin-amphotericin B suspension to 1000 mL of DMEM medium. After seeding, the cells were placed in a CO2 incubator (MCO-170AICUVH-PJ) (37°C, 5% CO2) to initiate culture. After 3 and 6 days, the medium was replaced by removing the medium with a 1000 mL pipette and replacing it with 1 mL. On day 7, 100 μL of WST-1 was added and the cells were placed in a CO2 incubator (37°C, 5% CO2) for 3 hours. 300 μL was then transferred to a 96-well plate and cell number was assessed by measuring absorbance (450 nm, reference wavelength 630 nm) using a plate reader (VERSA Max). The standard curve for evaluating cell number was prepared using the same method as for preparing the cell suspension described above, with 0.5 × 10 4 , 1.0×10 4 , 2.0×104 , 3.0×10 4 , 4.0×10 4 , 6.0×10 4 , 8.0×10 4 100 μL of WST-1 was added to the suspension adjusted to cells / mL, and the mixture was left to stand in a CO2 incubator (37°C, CO2 concentration 5%) for 3 hours. 300 μL of the mixture was then transferred to a 96-well plate, and the absorbance was measured using a plate reader (450 nm, reference wavelength 630 nm). [Cell adhesion of fibrous sheet structures] Cell adhesion was evaluated by statically culturing NIH3T3 cells on the structure for 7 days, observing the fluorescently labeled cells under a fluorescence microscope, and determining the degree of cell adhesion. ◎: Two-dimensional cell growth was observed, with cells adhering to the structure, and cells were immobilized on the surface of the structure. ○: Mainly two-dimensional cell growth that adheres to the structure, but some cell masses that have grown three-dimensionally are loosely attached to the surface of the structure. △: Mainly composed of cell masses that have grown three-dimensionally and are loosely attached to the surface of the structure. ×: No adhesion between the structure and cells was observed. [Cell adhesion and cell culturing properties of high-order structures and laminated high-order structures] The cell adhesion and cell culturing properties of the higher-order structures and multilayer structures were evaluated by statically culturing HeLa cells on the structures for 3 days and observing the fluorescently labeled cells under a fluorescence microscope. The higher-order structures and multilayer structures were placed on an MPC-coated 12-well plate, and medium was added to allow the structures to swell. The medium used was D-MEM / 10% FBS, penicillin and streptomycin. After swelling, excess medium was discarded, and 2 x 10 HeLa cell suspensions were added. 6 40 μl / well of 1 ml of ATP was seeded. 1 ml / well of the construct was added, and the cells were left to stand for 3 days in a 37°C, 5% CO2 environment. After culturing, the supernatant was discarded, and the cells were washed with 1 ml / well of phosphate-buffered saline. After washing, 1 ml / well of OPTI-MEM medium containing 2 μM Calcein AM, a fluorescent reagent, was added. The cells were left to stand for 2 hours in a 37°C, 5% CO2 environment, and cell adhesion and cell culturing properties were evaluated by qualitative observation under a fluorescent microscope. Cell adhesiveness was evaluated based on the degree of adhesion of cells adhered to the higher-order structures and the layered higher-order structures. ◎: Two-dimensional cell growth was observed, with cells adhering to the structure, and cells were immobilized on the surface of the structure. ○: Mainly two-dimensional cell growth that adheres to the structure, but some cell masses that have grown three-dimensionally are loosely attached to the surface of the structure. △: Mainly composed of cell masses that have grown three-dimensionally and are loosely attached to the surface of the structure. ×: No adhesion between the structure and cells was observed. Cell culturing ability was evaluated by qualitative observation of luminescence from cells stained with a fluorescent reagent under a fluorescence microscope. ◎: Strong fluorescence is observed over the entire surface of the structure. ◯: Strong fluorescence is observed from the parts of the structure excluding the gaps (mesh of the knitted fabric). △: Weak fluorescence is observed from the parts of the structure excluding the gaps (mesh of the knitted fabric). ×: No fluorescence is observed. <Production Example 1> 50% by weight of gelatin (Pigskin Gelatin Type A, manufactured by Nitta Gelatin) with a jelly strength of 293 g was added to 50% by weight of water, and the mixture was left for 30 minutes, after which it was kneaded and degassed in a vacuum-type foaming mixer (Thinky ARV-310P) to prepare a gelatin dope for spinning. The sol-gel transition temperature of the gelatin dope was 37°C.

[0203] The prepared gelatin dope was heated to 50°C and extruded into a fiber form at 50°C through a six-hole spinneret with a hole diameter of 150 μm (perfect circle). The extruded gelatin fiber was conveyed at 30 m / min along the circumferential surface of a conveying roller installed 1.8 m from the extrusion port and wound onto a bobbin by a winding roller to obtain a gelatin fiber bundle precursor consisting of six gelatin fibers. The extruded gelatin fiber was air-dried during the conveying process and coated with an oil agent (a mixed solution of 10% ethylene glycol and 90% ethanol) before being wound onto a bobbin. The moisture content of the gelatin fiber when it reached the conveying roller was 15% by weight. The moisture content of the gelatin fiber bundle precursor was 13% by weight, and no fusion between the fiber bundles was observed, and it also had good unwinding properties from the bobbin. The fineness of the wound gelatin fiber bundle precursor was 48 dtex, and the tensile strength and tensile elongation of the gelatin fiber taken out from the gelatin fiber bundle precursor were 1.1 cN / dtex and 74%, respectively.

[0204] The wound bobbin of gelatin fiber bundle precursor was heat-treated in air at 140°C for 24 hours to obtain a gelatin fiber bundle insolubilized in water. The gelatin fiber bundle had a fineness of 48 dtex, a tensile strength of 1.2 cN / dtex, and a tensile elongation of 84%, respectively, and the fineness of a single gelatin fiber was 8 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from its lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 84%, at which point it broke (1.2 cN / dtex). Furthermore, the weight loss rate of a gelatin fiber bundle immersed in phosphate buffered saline at 50°C for 4 hours was 18%, and the swelling rate was 240%.

[0205] Next, a high-order structure was obtained using the gelatin fiber bundles in a circular knitting machine (Model MR-1, manufactured by Maruzen Sangyo Co., Ltd.). The weight loss of the high-order structure after immersion in phosphate-buffered saline at 50°C for 4 hours was 18%, with 1.2% of the 18% weight loss being due to the oil. The thickness of the high-order structure was 83 μm, and the porosity was 91%. <Production Example 2> A gelatin fiber bundle precursor (fineness 48 dtex) consisting of six gelatin fibers before heat treatment was produced using the same method as in Production Example 1. This gelatin fiber bundle precursor was used to produce a knitted fabric using a circular knitting machine. Next, it was heat-treated in air at 140°C for 24 hours to insolubilize it in water, thereby obtaining a high-order structure consisting of gelatin fiber bundles. The tensile strength and tensile elongation of the gelatin fiber bundle obtained by decomposing this high-order structure were 1.2 cN / dtex and 84%, respectively, and the fineness of each gelatin fiber was 8 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from the lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 84%, at which point it broke (1.2 cN / dtex). Furthermore, the weight loss rate of the gelatin fiber bundle immersed in phosphate buffered saline at 50°C for 4 hours was 18%, and the swelling rate was 240%. The weight loss rate of the higher-order structural body immersed in phosphate buffered saline at 50°C for 4 hours was 18%. The thickness of the higher-order structural body was 83 μm, and the porosity was 91%. <Production Example 3> A gelatin fiber bundle precursor consisting of six gelatin fibers before heat treatment was produced using the same method as in Production Example 1. This gelatin fiber bundle precursor was used to produce a knitted fabric using a circular knitting machine. Next, the knitted fabric was immersed in a 12.5% ​​aqueous glutaraldehyde solution for 5 minutes, washed with water, dried, and insolubilized in water to obtain a high-order structure consisting of gelatin fiber bundles. The tensile strength and tensile elongation of the gelatin fibers obtained by decomposing this high-order structure were 0.8 cN / dtex and 65%, respectively, and the fineness of each gelatin fiber was 8 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.8 cN / dtex) at an elongation of 4%, and stretched from the lower yield point (lower yield stress: 0.70 cN / dtex) at an elongation of 15% to an elongation of 65%, at which point it broke (0.78 cN / dtex). Furthermore, the weight loss rate of the gelatin fiber bundle immersed in phosphate buffered saline at 50°C for 4 hours was 9%, and the swelling rate was 138%. The weight loss rate of the higher-order structural body immersed in phosphate buffered saline at 50°C for 4 hours was 9%. The thickness of the higher-order structural body was 83 μm, and the porosity was 91%. <Production Example 4> A gelatin fiber bundle precursor consisting of 24 gelatin fibers before heat treatment was produced in the same manner as in Example 1, except that the yarn extruded from a 24-hole spinneret with a hole diameter of 150 μm (perfect circle) was transported at 90 m / min. The moisture content of the gelatin fiber when it reached the transport roller was 13% by weight. The moisture content of the gelatin fiber bundle precursor was 10% by weight, no fusion between the fiber bundles was observed, and the unwinding property from the bobbin was also good. The fineness of the wound gelatin fiber bundle precursor was 133.6 dtex, and the tensile strength and tensile elongation of the gelatin fiber were 1.6 cN / dtex and 50%, respectively. This gelatin fiber bundle precursor was used to produce a knitted fabric on a circular knitting machine. Next, it was heat-treated in air at 140°C for 24 hours to insolubilize it in water, thereby obtaining a high-order structure consisting of gelatin fiber bundles. The tensile strength and tensile elongation of the gelatin fiber bundle obtained by decomposing this higher-order structure were 1.6 cN / dtex and 50%, respectively, and the fineness of a single gelatin fiber was 5.6 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 1.2 cN / dtex) at an elongation of 5%, and stretched from its lower yield point (lower yield stress: 1.15 cN / dtex) at an elongation of 15% to an elongation of 50% before breaking (1.6 cN / dtex). Furthermore, the weight loss of the gelatin fiber bundle immersed in phosphate-buffered saline at 50°C for 4 hours was 17%, and the swelling ratio was 230%. The weight loss rate of the high-order structure was 19% after immersion for 4 hours in phosphate buffered saline at 50° C. The thickness of the high-order structure was 132 μm, and the porosity was 84%. <Production Example 5> A high-order structure consisting of a gelatin fiber bundle was produced in the same manner as in Production Example 1, except that the bobbin of the wound gelatin fiber bundle precursor was heat-treated in air at 140°C for 24 hours instead of under vacuum at 180°C for 6 hours. The fineness of the gelatin fiber bundle was 46 dtex, and the tensile strength and tensile elongation were 1.5 cN / dtex and 62%, respectively, and the fineness of a single gelatin fiber was 8 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 1.15 cN / dtex) at an elongation of 5%, and stretched from its lower yield point (lower yield stress: 1.05 cN / dtex) at an elongation of 15% to an elongation of 62% before breaking (1.5 cN / dtex). The weight loss rate of the gelatin fiber bundle immersed in phosphate-buffered saline at 50°C for 4 hours was 9%, and the swelling rate was 138%. The weight loss of the high-order structure after immersion in phosphate buffered saline at 50°C for 4 hours was 9%, with 1.2% of the 9% weight loss being due to the oil. The thickness of the high-order structure was 83 μm and the porosity was 91%. <Production Example 6> A gelatin fiber bundle precursor consisting of 15 gelatin fibers before heat treatment was produced in the same manner as in Example 1, except that the yarn extruded from a 15-hole spinneret with a hole diameter of 150 μm (perfect circle) was transported at 60 m / min. The wound gelatin fiber bundle precursor had a fineness of 58.6 dtex, and the tensile strength and tensile elongation of the gelatin fiber were 1.1 cN / dtex and 77%, respectively. A thermoplastic resin fiber bundle consisting of 15 filaments and a fineness of 35.0 dtex made of polyglycolic acid was spirally wound around this gelatin fiber bundle precursor and twisted to produce a doubled yarn bundle precursor having 30 filaments and a fineness of 93.6 dtex. This doubled yarn bundle precursor was used to produce a knitted fabric on a circular knitting machine. Next, it was heat-treated in air at 140°C for 24 hours to insolubilize it in water, thereby obtaining a high-order structure consisting of a doubled yarn bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles. The tensile strength and tensile elongation of the gelatin fiber bundle obtained by decomposing this higher-order structure and the doubling bundle containing the thermoplastic resin fiber bundle were 7.2 cN / dtex and 35%, respectively. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor in air at 140°C for 24 hours had a fineness of 58.6 dtex, a tensile strength and tensile elongation of 1.2 cN / dtex and 79%, respectively, and the fineness of a single gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from the lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 79%, at which point it broke (1.2 cN / dtex). Furthermore, the weight loss rate of a doubly woven bundle of gelatin fiber bundles and thermoplastic resin fiber bundles immersed in phosphate buffered saline at 50°C for 4 hours was 12%, and the swelling rate was 145%. The weight loss rate of the high-order structural body immersed in phosphate buffered saline at 50°C for 4 hours was 12%. The thickness of the high-order structural body was 125 μm, and the porosity was 87%. <Production Example 7> A high-order structure consisting of a doubled yarn bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles was produced in the same manner as in Production Example 6, except that the twisting method was changed from winding a thermoplastic resin fiber bundle made of polyglycolic acid having 15 filaments and a fineness of 35.0 dtex spirally around a gelatin fiber bundle precursor to winding a gelatin fiber bundle precursor spirally around a thermoplastic resin fiber bundle made of polyglycolic acid having 15 filaments and a fineness of 35.0 dtex. The doubled yarn bundle precursor had 30 filaments and a fineness of 93.6 dtex. The tensile strength and tensile elongation of the doubled yarn bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles obtained by decomposing this high-order structure were 7.2 cN / dtex and 35%, respectively. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor in air at 140°C for 24 hours had a fineness of 58.6 dtex, a tensile strength of 1.2 cN / dtex, and a tensile elongation of 79%, respectively. The fineness of a single gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from its lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 79% before breaking (1.2 cN / dtex). Furthermore, the weight loss rate of a doubling bundle of gelatin fiber bundles and thermoplastic resin fiber bundles immersed in phosphate-buffered saline at 50°C for 4 hours was 12%, and the swelling rate was 145%. The weight loss rate of the higher-order structure immersed in phosphate-buffered saline at 50°C for 4 hours was 12%. The thickness of the high-order structure was 125 μm, and the porosity was 87%. <Production Example 8> A high-order structure consisting of a doubly-wrapped bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles was produced in the same manner as in Production Example 7, except that the heat treatment in air at 140°C for 24 hours was changed to a heat treatment in a vacuum at 160°C for 12 hours. The tensile strength and tensile elongation of the doubly-wrapped bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles obtained by decomposing this high-order structure were 6.8 cN / dtex and 32%, respectively. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor in a vacuum at 160°C for 12 hours had a fineness of 58.6 dtex, a tensile strength and tensile elongation of 1.3 cN / dtex and 65%, respectively, and the fineness of a single gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 1.0 cN / dtex) at an elongation of 5%, and stretched from its lower yield point (lower yield stress: 0.95 cN / dtex) at an elongation of 15% to an elongation of 65% before breaking (1.3 cN / dtex). The weight loss rate of a doubling bundle of gelatin fiber bundles and thermoplastic resin fiber bundles after immersion in phosphate buffered saline at 50°C for 4 hours was 9%, and the swelling rate was 135%. The weight loss rate of the high-order structure after immersion in phosphate buffered saline at 50°C for 4 hours was 9%. The thickness of the high-order structure was 125 μm, and the porosity was 87%. <Production Example 9> A gelatin fiber bundle precursor consisting of 15 gelatin fibers before heat treatment was produced in the same manner as in Production Example 1, except that the 6-hole spinneret with a hole diameter of 150 μm (perfect circle) was changed to a 15-hole spinneret with a hole diameter of 150 μm (perfect circle), and the transport speed of the extruded gelatin fibers was changed from 30 m / min to 60 m / min. The fineness of the wound gelatin fiber bundle precursor was 58.6 dtex, and the tensile strength and tensile elongation of the gelatin fibers taken out of the gelatin fiber bundle precursor were 1.1 cN / dtex and 77%, respectively. The moisture content of the gelatin fibers when they reached the transport roller was 12 wt%. The moisture content of the gelatin fiber bundle precursor was 10 wt%, and no fusion between the fiber bundles was observed, and the unwinding property from the bobbin was also good. Next, a thermoplastic resin fiber bundle consisting of polyglycolic acid (15 filaments, 35.0 dtex) was unwound at 30 m / min and washed in a bath containing 40 wt% ethanol to remove the oil. It was then dried by contact with a heated roller at 70 °C. It was then immersed in a collagen aqueous solution of Nitta Gelatin's Cell Matrix (Type IC) and dried to obtain a collagen-coated thermoplastic resin fiber bundle. A 30-filament, 93.6 dtex, doubling bundle precursor was produced by twisting a 15-filament, 35-dtex collagen-coated thermoplastic resin fiber bundle around a gelatin fiber bundle precursor. This doubling bundle precursor was then used to produce a knitted fabric on a circular knitting machine. It was then heat-treated in air at 140 °C for 24 hours to insolubilize it in water, yielding a high-order structure consisting of a doubling bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles. The tensile strength and tensile elongation of the gelatin fiber bundle obtained by decomposing this higher-order structure and the doubling bundle containing the thermoplastic resin fiber bundle were 7.2 cN / dtex and 35%, respectively. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor in air at 140°C for 24 hours had a fineness of 58.6 dtex, a tensile strength and tensile elongation of 1.2 cN / dtex and 79%, respectively, and the fineness of a single gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from the lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 79%, at which point it broke (1.2 cN / dtex). Furthermore, the weight loss rate of a doubly woven bundle of gelatin fiber bundles and thermoplastic resin fiber bundles immersed in phosphate buffered saline at 50°C for 4 hours was 12%, and the swelling rate was 145%. The weight loss rate of the high-order structural body immersed in phosphate buffered saline at 50°C for 4 hours was 12%. The thickness of the high-order structural body was 125 μm, and the porosity was 87%. <Production Example 10> A high-order structure consisting of a doubling bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles was obtained in the same manner as in Production Example 9, except that polyglycolic acid having 15 filaments and a fineness of 35.0 dtex was used instead of polylactic acid having 15 filaments and a fineness of 33.0 dtex. The doubling bundle precursor had 30 filaments and a fineness of 91.6 dtex. The doubling bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles obtained by decomposing this high-order structure had a tensile strength and a tensile elongation of 5.5 cN / dtex and 36%, respectively. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor in air at 140°C for 24 hours had a fineness of 58.6 dtex, a tensile strength and a tensile elongation of 1.2 cN / dtex and 79%, respectively, and the fineness of each gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from its lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 79% before breaking (1.2 cN / dtex). The weight loss rate of a doubling bundle of gelatin fiber bundles and thermoplastic resin fiber bundles after immersion in phosphate buffered saline at 50°C for 4 hours was 12%, and the swelling rate was 145%. The weight loss rate of the high-order structure after immersion in phosphate buffered saline at 50°C for 4 hours was 12%. The thickness of the high-order structure was 125 μm, and the porosity was 89%. <Production Example 11> The high-order structures obtained in Production Example 6 were attached to the base of an electrospinning apparatus (NANON-04, manufactured by MEC). A gelatin dope (20 wt.% gelatin dissolved in an aqueous acetic acid solution containing 30 wt.% acetic acid) was electrospun at room temperature for 1 minute at 20 kV, a discharge rate of 0.3 cc / min, and a nozzle distance of 10 cm from the nozzle tip to the high-order structures. A laminated high-order structure precursor consisting of a gelatin nonwoven fabric and the high-order structures was produced. This laminated high-order structure precursor was dried under vacuum at room temperature for 24 hours, and then pressed against the gelatin nonwoven fabric side at 70 °C and 800 KPa for 60 seconds, followed by heat treatment under vacuum at 160 °C for 12 hours to obtain a laminated high-order structure in which the gelatin nonwoven fabric was laminated on the high-order structures. The tensile strength and tensile elongation of a doped yarn bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles obtained by decomposing this laminated high-order structure were 6.8 cN / dtex and 32%, respectively. Furthermore, a combined yarn bundle of gelatin fiber bundles and thermoplastic resin fiber bundles immersed in phosphate buffered saline at 50°C for 4 hours had a weight loss of 9% and a swelling rate of 135%. A laminated high-order structure immersed in phosphate buffered saline at 50°C for 4 hours had a weight loss of 9%, with 1.0% of the 9% weight loss being due to the oil. The thickness of the laminated high-order structure was 125 μm and the porosity was 87%. <Production Example 12> A laminated high-order structure in which a gelatin nonwoven fabric was laminated on a high-order structure was obtained in the same manner as in Production Example 11, except that the heat treatment was changed from 12 hours in a vacuum at 160°C to 24 hours in air at 140°C. The laminated high-order structure was decomposed to obtain a doubled yarn bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles. The tensile strength and tensile elongation of the doubled yarn bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles were 7.2 cN / dtex and 35%, respectively. Furthermore, the weight loss rate of the doubled yarn bundle of gelatin fiber bundles and thermoplastic resin fiber bundles after immersion in phosphate-buffered saline at 50°C for 4 hours was 12%, and the swelling rate was 145%. The weight loss of the laminated high-order structure after immersion in phosphate buffered saline at 50°C for 4 hours was 12%, with 1.0% of the weight loss being due to the oil. The thickness of the laminated high-order structure was 125 μm and the porosity was 87%. <Production Example 13> The high-order structures obtained in Production Example 6 were attached to the base of an electrospinning apparatus (NANON-04, manufactured by MEC). A collagen dope (10 wt. % of the total dope weight of collagen dissolved in an acetic acid solution containing 84 wt. % acetic acid) was electrospun at room temperature for 1 minute at 20 kV, a discharge rate of 0.3 cc / min, and a nozzle distance of 10 cm from the tip of the high-order structure to produce a laminated high-order structure precursor consisting of a collagen nonwoven fabric and the high-order structure. This laminated high-order structure precursor was dried under vacuum at room temperature for 24 hours, pressed at 80°C and 800 KPa for 60 seconds, and then heat-treated under vacuum at 140°C for 24 hours to obtain a laminated high-order structure consisting of a collagen nonwoven fabric laminated on the high-order structure. The tensile strength and tensile elongation of a doped yarn bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles obtained by decomposing this laminated high-order structure were 7.2 cN / dtex and 35%, respectively. In addition, the weight loss rate of a doubly-woven bundle of gelatin fiber bundles and thermoplastic resin fiber bundles immersed in phosphate buffered saline at 50°C for 4 hours was 12%, and the swelling rate was 145%. The weight loss of the laminated high-order structure after immersion in phosphate buffered saline at 50°C for 4 hours was 13%, of which 1.0% was due to the oil. The thickness of the laminated high-order structure was 125 μm and the porosity was 87%. <Production Example 14> A gelatin monohole yarn precursor before heat treatment was produced in the same manner as in Example 1, except that the yarn extruded from a monohole spinneret with a hole diameter of 150 μm (perfect circle) was wound at 10 m / min. The moisture content of the wound gelatin monohole yarn precursor was 17% by weight, no fusion of the fibers was observed, and the unwinding property from the bobbin was good. The fineness of the wound gelatin monohole yarn precursor was 128 dtex, and the tensile strength and tensile elongation of the gelatin fiber (gelatin monohole yarn precursor) were 0.6 cN / dtex and 63%, respectively.

[0206] The wound bobbin of gelatin monohole yarn precursor was heat-treated in air at 140°C for 24 hours to obtain water-insolubilized gelatin monohole yarn. The gelatin monohole yarn after insolubilization had a fineness of 128 dtex, a tensile strength of 0.7 cN / dtex, and a tensile elongation of 122%, respectively. Furthermore, the gelatin monohole yarn immersed in phosphate-buffered saline at 50°C for 4 hours showed a weight loss of 19% and a swelling ratio of 280%.

[0207] Next, an attempt was made to knit a fabric using a circular knitting machine using gelatin monohole yarn, but many knitted pieces were missing and no knitted fabric could be obtained. <Production Example 15> We attempted to knit fabrics using a commercially available PET monohole yarn with a fineness of 110 dtex on a circular knitting machine, but we were unable to obtain any knitted fabrics due to the large number of knitted pieces. <Production Example 16> A gelatin monohole yarn precursor before heat treatment was produced in the same manner as in Example 1, except that the yarn extruded from a monohole spinneret with a hole diameter of 150 μm (perfect circle) was wound at 30 m / min. The moisture content of the gelatin monohole yarn precursor was 15 wt %, no fusion between fibers was observed, and the unwinding property from the bobbin was good. The fineness of the wound gelatin monohole yarn precursor was 8 dtex, and the tensile strength and tensile elongation of the gelatin fiber (gelatin monohole yarn precursor) were 1.0 N / cm and 72%, respectively.

[0208] The wound bobbin of gelatin monohole yarn precursor was heat-treated in air at 140°C for 24 hours to obtain a water-insoluble gelatin monohole yarn. The gelatin monohole yarn had a fineness of 8 dtex, a tensile strength of 1.2 cN / dtex, and a tensile elongation of 84%. The weight loss of the gelatin monohole yarn after immersion in phosphate-buffered saline at 50°C for 4 hours was 18%. Next, we attempted to knit fabrics using the gelatin monohole yarn on a circular knitting machine, but the yarn strength was so low that frequent yarn breakage occurred and we were unable to obtain any knitted fabrics. <Production Example 17> A high-order structure was produced using a circular knitting machine using a thermoplastic resin fiber bundle made of polylactic acid with 15 filaments and a fineness of 33.0 dtex. The tensile strength and tensile elongation of the thermoplastic resin fiber bundle obtained by disassembling this high-order structure were 4.5 cN / dtex and 33%, respectively. Furthermore, the weight loss rate of the thermoplastic resin fiber bundle after immersion in phosphate buffered saline at 50°C for 4 hours was 0%, and the swelling rate was 100%. The weight loss rate of the high-order structure after immersion in phosphate buffered saline at 50°C for 4 hours was 0%. The thickness of the high-order structure was 78 μm, and the porosity was 85%. <Production Example 18> Using the doubling bundle precursor of Production Example 6, a double knit (second high-order structure) was produced by stacking two plain knit layers of WHOLEGARMENT® (SWG® 041N2) fabric. The double knit was heat-treated under vacuum at 140°C for 24 hours to insolubilize it, and then one side of the double knit was heated to 70°C and pressed at 800 KPa for 60 seconds to obtain a fiber sheet structure. The doubling bundle, containing gelatin fiber bundles and thermoplastic resin fiber bundles obtained by decomposing this fiber sheet structure, had a tensile strength and a tensile elongation of 7.2 cN / dtex and 35%, respectively. Furthermore, the weight loss and swelling ratio of the doubling bundle after immersion in phosphate-buffered saline at 50°C for 4 hours were 12% and 145%, respectively. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor under vacuum at 140°C for 24 hours had a fineness of 58.6 dtex, a tensile strength of 1.2 cN / dtex, and a tensile elongation of 79%, respectively, and the fineness of a single gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from the lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 79%, at which point it broke (1.2 cN / dtex). <Production Example 19> Using the doubling bundle precursor of Production Example 6, a double knit (second high-order structure) was produced by stacking two layers of plain knit fabric using WHOLEGARMENT (registered trademark) (SWG (registered trademark) 041N2) with a thickness of 1670 μm, an average pore size of 127 μm, and a porosity of 93%. This double knit was heat-treated in a vacuum at 140°C for 24 hours to insolubilize it, and then one side was heated to 60°C and pressed at 700 KPa for 60 seconds to obtain a fiber sheet structure. The doubling bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles obtained by decomposing this fiber sheet structure had a tensile strength and a tensile elongation of 7.2 cN / dtex and 35%, respectively. Furthermore, the doubling bundle, when immersed in phosphate-buffered saline at 50°C for 4 hours, showed a weight loss of 12% and a swelling ratio of 145%. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor under vacuum at 140°C for 24 hours had a fineness of 58.6 dtex, a tensile strength of 1.2 cN / dtex, and a tensile elongation of 79%, respectively, and the fineness of a single gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from the lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 79%, at which point it broke (1.2 cN / dtex). <Production Example 20> Using the doubling bundle precursor of Production Example 6, a double knit (second high-order structure) was produced by stacking two plain knit layers of WHOLEGARMENT (registered trademark) (SWG (registered trademark) 041N2) with a thickness of 1940 μm, an average pore size of 150 μm, and a porosity of 95%. This double knit was heat-treated in a vacuum at 140°C for 24 hours to insolubilize it, and then one side was heated to 70°C and pressed at 800 KPa for 60 seconds to obtain a fiber sheet structure. The doubling bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles obtained by decomposing this second high-order structure had a tensile strength and a tensile elongation of 7.2 cN / dtex and 35%, respectively. Furthermore, the doubling bundle, when immersed in phosphate-buffered saline at 50°C for 4 hours, showed a weight loss of 12% and a swelling ratio of 145%. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor under vacuum for 24 hours had a fineness of 58.6 dtex, a tensile strength of 1.2 cN / dtex, and a tensile elongation of 79%, respectively, and the fineness of a single gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from the lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 79% before breaking (1.2 cN / dtex). <Production Example 21> Using the doubling bundle precursor of Production Example 7, a double knit (second high-order structure) was produced by stacking two layers of plain knit fabric using WHOLEGARMENT® (SWG® 041N2) with a thickness of 2040 μm, an average pore size of 95 μm, and a porosity of 94%. This double knit was heat-treated in a vacuum at 140°C for 24 hours to insolubilize it, and then heated to 70°C on one side and pressed at 800 KPa for 60 seconds to obtain a fiber sheet structure. The doubling bundle, containing gelatin fiber bundles and thermoplastic resin fiber bundles obtained by decomposing this fiber sheet structure, had a tensile strength and a tensile elongation of 7.2 cN / dtex and 35%, respectively. Furthermore, the doubling bundle, after immersion in phosphate-buffered saline at 50°C for 4 hours, showed a weight loss of 12% and a swelling ratio of 145%. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor under vacuum at 140°C for 24 hours had a fineness of 58.6 dtex, a tensile strength of 1.2 cN / dtex, and a tensile elongation of 79%, respectively, and the fineness of a single gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from the lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 79%, at which point it broke (1.2 cN / dtex). <Production Example 22> A doubling bundle precursor containing four gelatin fiber bundle precursors and four thermoplastic resin fiber bundles was produced using four doubling bundle precursors from Production Example 6 and four thermoplastic resin fiber bundles. This was then ribbed using Wholegarment® (SWG® 041N2) to produce a single knit (second high-order structure) with a thickness of 940 μm, an average pore size of 125 μm, and a porosity of 94%. This single knit was insolubilized under vacuum at 140°C for 24 hours, and then heated to 70°C on one side and pressed at 800 KPa for 60 seconds to obtain a fiber sheet structure. The tensile strength and tensile elongation of the doubling bundle containing the gelatin fiber bundles and thermoplastic resin fiber bundles obtained by disassembling this fiber sheet structure were 7.2 cN / dtex and 35%, respectively. Furthermore, the weight loss and swelling ratio of the doubling bundle after immersion in phosphate-buffered saline at 50°C for 4 hours were 12% and 145%, respectively. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor in air at 140°C for 24 hours had a fineness of 58.6 dtex, a tensile strength of 1.2 cN / dtex, and a tensile elongation of 79%, respectively, and the fineness of a single gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from the lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 79% before breaking (1.2 cN / dtex). <Production Example 23> The double knit (second high-order structure) of Production Example 19 was attached to the base of an electrospinning apparatus (NANON-04, manufactured by MEC). A gelatin dope (20 wt.% gelatin dissolved in an aqueous acetic acid solution containing 30 wt.% acetic acid) was electrospun at room temperature for 1 minute at 20 kV, a discharge rate of 0.3 cc / min, and a distance of 10 cm from the nozzle tip to the second high-order structure. This produced a second laminated high-order structure consisting of a gelatin nonwoven fabric and the second high-order structure. The second laminated high-order structure was heat-treated in a vacuum at 140°C for 24 hours to insolubilize it, and then heated to 60°C on one side and pressed at 700 KPa for 60 seconds to obtain a fiber sheet structure. The fiber sheet structure was disassembled to produce a doped yarn bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles. The tensile strength and tensile elongation were 7.2 cN / dtex and 35%, respectively. The weight loss rate of the doubling yarn bundle immersed in phosphate-buffered saline at 50°C for 4 hours was 12%, and the swelling rate was 145%. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor in air at 140°C for 24 hours had a fineness of 58.6 dtex, a tensile strength of 1.2 cN / dtex, and a tensile elongation of 79%, respectively, and the fineness of a single gelatin fiber was 3.9 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.85 cN / dtex) at an elongation of 5%, and stretched from the lower yield point (lower yield stress: 0.80 cN / dtex) at an elongation of 15% to an elongation of 79% before breaking (1.2 cN / dtex). <Production Example 24> The single knit (second high-order structure) from Production Example 22 was attached to the base of an electrospinning apparatus (NANON-04, manufactured by MEC). A gelatin dope (20 wt.% gelatin dissolved in an aqueous acetic acid solution containing 30 wt.% acetic acid) was electrospun at room temperature for 1 minute at 20 kV, a discharge rate of 0.3 cc / min, and a nozzle distance of 10 cm from the tip of the nozzle to the second high-order structure. This produced a second laminated high-order structure consisting of a gelatin nonwoven fabric and the second high-order structure. The second laminated high-order structure was heat-treated in a vacuum at 160°C for 12 hours to insolubilize it, and then the surface facing the gelatin nonwoven fabric was heated to 70°C and pressed at 800 KPa for 60 seconds to produce a fiber sheet structure. The fiber sheet structure was disassembled to produce a doped yarn bundle containing gelatin fiber bundles and thermoplastic resin fiber bundles. The tensile strength and tensile elongation of the doped yarn bundle were 6.8 cN / dtex and 32%, respectively. The weight loss rate of the doubling bundle after immersion in phosphate-buffered saline at 50°C for 4 hours was 9%, and the swelling rate was 135%. The gelatin fiber bundle obtained by heat-treating the gelatin fiber bundle precursor under vacuum at 160°C for 24 hours had a fineness of 52.5 dtex, a tensile strength of 1.1 cN / dtex, and a tensile elongation of 70%, respectively, and the fineness of a single gelatin fiber was 3.5 dtex. The gelatin fiber bundle reached its upper yield point (upper yield stress: 0.82 cN / dtex) at an elongation of 5%, and stretched from the lower yield point (lower yield stress: 0.75 cN / dtex) at an elongation of 14% to an elongation of 56% before breaking (0.9 cN / dtex). <Reference example 1> The high-order structures obtained in Production Example 1 were evaluated for texture, average friction coefficient, average deviation of friction coefficient, average pore size, percentage (%) of pores 150 μm or larger, number of pores, presence or absence of curling, and cell adhesion and cell culturing properties using HeLa cells. <Reference example 2> The high-order structural body obtained in Production Example 2 was evaluated for texture. <Reference example 3> The high-order structures obtained in Production Example 3 were evaluated for texture, average friction coefficient, average deviation of friction coefficient, average pore size, percentage (%) of pores 150 μm or larger, number of pores, presence or absence of curling, and cell adhesion and cell culturing properties using HeLa cells. <Reference example 4> The high-order structural body obtained in Production Example 4 was evaluated for texture. <Reference example 5> The high-order structure obtained in Production Example 5 was evaluated for texture, average friction coefficient, average deviation of friction coefficient, average pore size, percentage (%) of pores 150 μm or larger, number of pores, presence or absence of curling, and cell adhesion and cell culturing properties using HeLa cells. <Reference example 6> The high-order structure obtained in Production Example 6 was evaluated for texture, average friction coefficient, average deviation of friction coefficient, average pore size, percentage (%) of pores 150 μm or larger, number of pores, presence or absence of curling, and cell adhesion and cell culturing properties using HeLa cells. <Reference example 7> The high-order structure obtained in Production Example 7 was evaluated for texture, average friction coefficient, average deviation of friction coefficient, average pore size, percentage (%) of pores 150 μm or larger, number of pores, presence or absence of curling, and cell adhesion and cell culturing properties using HeLa cells. <Reference example 8> The texture, average friction coefficient, average deviation of the friction coefficient, and cell adhesion and cell culturing properties using HeLa cells were evaluated for the higher-order structures obtained in Production Example 8, the average pore size, the percentage (%) of pores of 150 μm or larger, the number of pores, and the presence or absence of curling. <Reference example 9> The texture, average friction coefficient, average deviation of the friction coefficient, and cell adhesion and cell culturing properties using HeLa cells were evaluated for the higher-order structures obtained in Production Example 9, including the average pore size, percentage (%) of pores of 150 μm or larger, number of pores, and presence or absence of curling. <Reference example 10> The high-order structure obtained in Production Example 10 was evaluated for texture, average friction coefficient, average deviation of friction coefficient, average pore size, percentage (%) of pores 150 μm or larger, number of pores, presence or absence of curling, and cell adhesion and cell culturing properties using HeLa cells. <Reference example 11> The laminated high-order structure obtained in Production Example 11 was evaluated for the average friction coefficient, average deviation of the friction coefficient, average pore size, percentage (%) of pores 150 μm or larger, number of pores, presence or absence of curling, and cell adhesion and cell culturing properties using HeLa cells. <Reference example 12> The laminated high-order structure obtained in Production Example 12 was evaluated for texture, average friction coefficient, average deviation of friction coefficient, average pore size, percentage (%) of pores 150 μm or larger, number of pores, presence or absence of curling, and cell adhesion and cell culturing properties using HeLa cells. <Reference example 13> The laminated high-order structure obtained in Production Example 13 was evaluated for texture, average friction coefficient, average deviation of friction coefficient, average pore size, percentage (%) of pores 150 μm or larger, number of pores, presence or absence of curling, and cell adhesion and cell culturing properties using HeLa cells.

[0209] The evaluation results of Reference Examples 1 to 13 are shown in Tables 1 and 2. Example 1 The fiber sheet structure obtained in Production Example 18 was immersed in phosphate-buffered saline at 50°C for 4 hours, and the weight loss rate, thickness, porosity, average pore size, percentage of pores 150 μm or larger, number of pores, texture, average friction coefficient, average deviation of friction coefficient, presence or absence of curling, and cell adhesiveness using NIH3T3 cells and number of cells cultured were evaluated. <Example 2> The fiber sheet structure obtained in Production Example 19 was immersed in phosphate-buffered saline at 50°C for 4 hours, and the weight loss rate, thickness, porosity, average pore size, percentage of pores 150 μm or larger, number of pores, texture, average friction coefficient, average deviation of friction coefficient, presence or absence of curling, and cell adhesiveness using NIH3T3 cells and the number of cells cultured were evaluated. Example 3 The fiber sheet structure obtained in Production Example 20 was immersed in phosphate-buffered saline at 50°C for 4 hours, and the weight loss rate, thickness, porosity, average pore size, percentage of pores 150 μm or larger, number of pores, texture, average friction coefficient, average deviation of friction coefficient, presence or absence of curling, and cell adhesiveness using NIH3T3 cells and number of cells cultured were evaluated. Example 4 The fiber sheet structure obtained in Production Example 21 was immersed in phosphate-buffered saline at 50°C for 4 hours, and the weight loss rate, thickness, porosity, average pore size, percentage of pores 150 μm or larger, number of pores, texture, average friction coefficient, average deviation of friction coefficient, presence or absence of curling, and cell adhesiveness using NIH3T3 cells and the number of cells cultured were evaluated. <Example 5> The fiber sheet structure obtained in Production Example 22 was immersed in phosphate-buffered saline at 50°C for 4 hours, and the weight loss rate, thickness, porosity, average pore size, percentage of pores 150 μm or larger, number of pores, texture, average friction coefficient, average deviation of friction coefficient, presence or absence of curling, and cell adhesiveness using NIH3T3 cells and the number of cells cultured were evaluated. Example 6 The fiber sheet structure obtained in Production Example 23 was immersed in phosphate-buffered saline at 50°C for 4 hours, and the weight loss rate, thickness, porosity, average pore size, percentage of pores 150 μm or larger, number of pores, texture, average friction coefficient, average deviation of friction coefficient, presence or absence of curling, cell adhesion using NIH3T3 cells, and number of cells cultured were evaluated. Example 7 The fiber sheet structure obtained in Production Example 24 was immersed in phosphate-buffered saline at 50°C for 4 hours, and the weight loss rate, thickness, porosity, average pore size, percentage of pores 150 μm or larger, number of pores, texture, average friction coefficient, average deviation of friction coefficient, presence or absence of curling, and cell adhesiveness using NIH3T3 cells and number of cells cultured were evaluated. <Comparative Example 1> The feel of the fiber in Production Example 14 was evaluated. <Comparative Example 2> The feel of the fiber in Production Example 15 was evaluated. <Comparative Example 3> The feel of the fiber in Production Example 16 was evaluated. <Comparative Example 4> The high-order structure obtained in Production Example 17 was evaluated for texture, average friction coefficient, average deviation of friction coefficient, average pore size, percentage (%) of pores 150 μm or larger, number of pores, presence or absence of curling, and cell adhesion and cell culturing properties using NIH3T3 cells. <Comparative Example 5> Using the collagen sheet surface of Geistlich Bioguide (a two-layer structure of collagen sheet and collagen nonwoven fabric), the average friction coefficient, the average deviation of the friction coefficient, the presence or absence of curling, and the cell adhesion and cell culture number using NIH3T3 cells were evaluated. The evaluation results for the examples and comparative examples are shown in Tables 3 and 4.

[0210] [Table 1]

[0211] [Table 2]

[0212] [Table 3]

[0213] [Table 4]

[0214] The results shown in Table 4 indicate that the fiber sheet structures obtained in the examples have a good texture, adequate slipperiness, and excellent cell adhesion and culturing properties after cell settlement. SEM images confirm that cells penetrate the inner layer of the fiber sheet structure and grow from the settled areas, crawling onto the fibers and filling the joints between the fibers. [Industrial Applicability]

[0215] The fiber sheet structure of the present invention can be used as a medical material with excellent mechanical strength and biocompatibility (low antigenicity and high bioabsorbability), and can be suitably used as a material for wound and burn treatment, a matrix material for artificial skin, etc. It can also be suitably used as a scaffold for three-dimensional cell culture, which is excellent in promoting cell differentiation, enhancing cell function, and providing excellent adhesion after transplantation.

Claims

1. A fibrous sheet structure, the fiber sheet structure includes a knitted structure and has a cell-mounting surface and a back surface; the average pore size of the back surface is smaller than the average pore size of the cell-mounting surface, the knitted structure includes a doubling bundle made of a gelatin fiber bundle and a thermoplastic resin fiber bundle, The thickness of the fiber sheet structure is 30 to 5000 μm, the number of gelatin fibers constituting the gelatin fiber bundle is 5 to 60, and the fineness of the gelatin fibers is 0.5 to 10 dtex, The fiber sheet structure has a total number of gelatin fiber bundles and thermoplastic resin fiber bundles in the doubled yarn bundle of 2 to 20, and a ratio of the number of gelatin fiber bundles to the number of thermoplastic resin fiber bundles in the doubled yarn bundle of 5:1 to 1:

5.

2. 2. The fiber sheet structure according to claim 1, wherein the fiber sheet structure is any one of the following (1) to (4): (1) A structure in which two layers are laminated, the surface layer and the back layer are knitted, and the knitted structure is plain knit or plain knit; (2) A structure in which three layers are laminated, the surface layer is a knitted structure, the back layer is a nonwoven fabric, an intermediate layer between the surface layer and the back layer is a knitted structure, the knitted structure is a plain knit or plain knit, and the nonwoven fabric contains gelatin fibers. (3) A structure in which two layers are laminated, the surface layer being a knitted structure and the back layer being a nonwoven fabric, the knitted structure being a rib knit, and the nonwoven fabric containing gelatin fibers. (4) A knitted structure consisting of rib knitting.

3. The average pore size of the cell-mounting surface is 5 to 123 μm, and the number of pores of 150 μm or larger on the cell-mounting surface is 35% or less, and the number of pores in the knitted structure is 600 / mm ３ The fiber sheet structure according to claim 1 or 2, wherein the fiber sheet structure is formed of the above-mentioned material.

4. 4. The fiber sheet structure according to claim 3, wherein the swelling ratio of the doubling bundle when immersed in phosphate buffered saline at 50° C. for 4 hours is 110 to 350%.

5. 4. The fiber sheet structure according to claim 3, wherein the tensile strength of the doubling yarn bundle is 1.0 to 20.0 cN / dtex and the breaking elongation is 20 to 250%.

6. 4. The fiber sheet structure according to claim 3, wherein the weight loss rate of the fiber sheet structure when immersed in phosphate buffered saline at 50° C. for 4 hours is 3 to 30%.

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