JP6778099B2 - Inorganic fiber sheet and its manufacturing method - Google Patents

Description

The present invention relates to an inorganic fiber sheet and a method for producing the same. More specifically, the present invention relates to an inorganic fiber sheet that can be suitably used as a culture medium, a filler for a therapeutic site, and a method for producing the same.

The human body consists of about 60% water, about 36% organic matter and about 4% inorganic matter. Apatite accounts for the majority of this inorganic substance. Hydroxyapatite, which is a type of apatite, is the main component of teeth and bones. In the human body, it is the second largest after organic substances such as water and collagen, about 60% of bones, 97% of tooth enamel, and dentin. It accounts for 70% of the quality.

Due to its high biocompatibility, apatite is used as a medical material for artificial bones and artificial teeth, as a filling material for bones and tooth roots, and as a research material for bone models, osteoclast separation, culture and differentiation. It is applied as a base material for the purpose of polishing test of toothbrush or toothpaste.

For example, Japanese Patent Application Laid-Open No. 2014-57841 (Patent Document 1) states that "a non-woven fabric containing a bone filling material, the bone filling material is contained between the fibers constituting the non-woven fabric, and the fibers constituting the non-woven fabric are living organisms. It is a compatible fiber, and the biocompatible fiber is a fiber containing a biocompatible polymer, and is a non-woven fabric containing a water-soluble polymer. " However, when used in the medical field, it is necessary to perform heat treatment or γ-ray treatment at a high temperature in order to remove endotoxin, but in the above-mentioned Patent Document 1, since a biocompatible polymer such as polylactic acid is contained. There is a problem that the biocompatible polymer is decomposed or modified by heat treatment at high temperature or γ-ray treatment.

The applicant of the present application also found in Japanese Patent Application Laid-Open No. 2012-16323 (Patent Document 2) and Controlling apatite microparticles formation by calcining electrospun sol-gel derived ultrafine silica fibers (Non-Patent Document 1) that artificially containing phosphate ions and calcium ions. By immersing the silica fiber non-woven fabric in the body fluid, apatite particles can be precipitated on the silica fibers, and apatite particles can be precipitated on the surface of the silica fibers heat-treated at a temperature of 500 ° C. or lower. It is disclosed that apatite particles cannot be precipitated on the surface of silica fibers heat-treated at a temperature of 800 ° C. As described above, if the silica fiber non-woven fabric heat-treated at a temperature of 500 ° C. or lower is used, the apatite particles can be precipitated, but the non-woven fabric has low strength and is difficult to handle.

Japanese Unexamined Patent Publication No. 2014-57841 Japanese Unexamined Patent Publication No. 2012-16323

Kawakami, Controlling apatite microparticles formation by calcining electrospun sol-gel derived ultrafine silica fibers, J Sol-Gel Sci Technol (2012) 61: 374-380

The present invention has been made under such circumstances, and is an inorganic fiber sheet containing an inorganic fiber containing an apatite component, which is easy to handle without being decomposed or denatured by heat treatment at a high temperature or γ-ray treatment, and an inorganic fiber sheet. It is an object of the present invention to provide the manufacturing method.

The inorganic fiber sheet of the present invention is an inorganic fiber sheet containing an inorganic fiber containing an inorganic component and an apatite component, and the tensile strength of the inorganic fiber sheet is 0.2 MPa or more.

Further, it is preferable that the apatite component is contained in an amount of 10 mass% or more, the inorganic component is amorphous silica, and / or the porosity of the inorganic fiber sheet is 80% or more.

Further, the inorganic fiber sheet of the present invention is preferably used as a culture medium or a filler in a therapeutic site.

The inorganic fiber sheet of the present invention is formed by spinning a spinning solution containing a precursor inorganic component and an apatite component to form a precursor inorganic fiber, forming a precursor inorganic fiber sheet containing the precursor inorganic fiber, and then firing. It can be produced by making the precursor inorganic fiber into an inorganic fiber and making an inorganic fiber sheet having a tensile strength of 0.2 MPa or more.

It is preferable that the precursor inorganic fibers are formed by an electrostatic spinning method and the formed precursor inorganic fibers are directly integrated to form a precursor inorganic fiber sheet.

Since the inorganic fiber constituting the inorganic fiber sheet of the present invention contains an inorganic component and an apatite component, it is not decomposed or modified by heat treatment at high temperature or γ-ray treatment, and is chemically stable. Further, the tensile strength of the inorganic fiber sheet is 0.2 MPa or more, and the handleability is excellent.

When the inorganic fiber constituting the inorganic fiber sheet of the present invention contains an apatite component of 10 mass% or more, the biocompatibility is excellent. In addition, the infiltrated cells can sufficiently exert high physiological activity.

When the inorganic component of the inorganic fiber constituting the inorganic fiber sheet of the present invention is amorphous silica, it is an inorganic fiber having high flexibility, so that the inorganic fiber sheet is excellent in flexibility, handleability and workability. Is.

When the porosity of the inorganic fiber sheet of the present invention is 80% or more, the inside of the inorganic fiber sheet can also be effectively utilized. For example, when an inorganic fiber sheet is used as a culture substrate, cells can grow into the inside of the inorganic fiber sheet, so that three-dimensional culture is possible. In addition, when used as a filler at the treatment site, osteoblasts easily infiltrate into the inside, and the filler itself contains apatite, which is a component of bone having a high affinity with osteoblasts, so that the infiltrated bone It is easy to exert the bone formation function of osteoblasts, and bone regeneration at the treatment site can be promoted at an early stage.

When the inorganic fiber sheet of the present invention is used as a culture base material, three-dimensional culture may be possible, which is a useful culture base material.

When the inorganic fiber sheet of the present invention is used as a filler at a treatment site, the filler itself contains apatite, which is a bone component having a high affinity with osteoblasts, and therefore, the bone-forming function of osteoblasts is enhanced. It is easy to exert and can promote bone regeneration at the treatment site at an early stage.

According to the production method of the present invention, the above-mentioned inorganic fiber sheet which is chemically stable and has excellent handleability without being decomposed or denatured by heat treatment at high temperature or γ-ray treatment can be produced.

When the precursor inorganic fiber is formed by the electrostatic spinning method and the formed precursor inorganic fiber is directly integrated to form the precursor inorganic fiber sheet, the fiber diameter and the pore diameter are uniform and the void ratio is 80. A precursor inorganic fiber sheet having a large amount of voids of% or more can be formed, and as a result, an inorganic fiber sheet having the above physical properties can be produced.

A graph showing the relationship between the number of culture days and the ALP relative activity value in the inorganic fiber sheet of the example.

The inorganic fiber sheet of the present invention contains an inorganic fiber containing an inorganic component and an apatite component so as not to be decomposed or denatured by heat treatment at high temperature or γ-ray treatment.

The inorganic component constituting the inorganic fiber of the present invention may be any inorganic component that is not decomposed or modified by heat treatment at high temperature or γ-ray treatment, and is not particularly limited. For example, lithium, beryllium, boron, carbon. , Sodium, magnesium, aluminum, silicon, phosphorus, sulfur, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, germanium, arsenic, selenium, rubidium, strontium, ittrium , Zirconium, niobium, molybdenum, cadmium, indium, tin, antimony, terbium, cesium, barium, lantern, hafnium, tantalum, tungsten, mercury, tarium, lead, bismus, cerium, placeodium, neodymium, promethium, samarium, europium, gadolinium. , Terbium, dysprosium, formium, erbium, turium, itterbium, or lutetium oxides, specifically SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , TIO ₂ , ZrO ₂ , CeO. ₂ , FeO, Fe ₃ O ₄ , Fe ₂ O ₃ , VO ₂ , V ₂ O ₅ , SnO ₂ , CdO, LiO ₂ , WO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , In ₂ O ₃ , GeO ₂ , and the like _{PbTi 4 O 9, LiNbO 3,} BaTiO 3, PbZrO 3, KTaO 3, Li 2 B 4 O 7, NiFe 2 O 4, SrTiO 3.

Among these, silica (SiO ₂ ) is suitable because it is bioinert, and in particular, since the inorganic fiber containing amorphous silica is a highly flexible fiber, the inorganic fiber sheet containing this inorganic fiber is suitable. It is suitable because it has excellent flexibility and is excellent in handleability and workability. Since amorphous is isotropic and does not have a long-period structure like a crystal, it can be confirmed by showing a halo pattern when measured by an X-ray diffractometer.

When magnesium metal and / or calcium metal is contained as the inorganic component, the inorganic fiber can be a biosoluble fiber.

Further, the inorganic component may be composed of an oxide of one element or may be composed of an oxide containing two or more elements. For example, it may be composed of an oxide containing two or more kinds of elements such as SiO _2- TiO ₂ which is particularly easy to adsorb a protein of a bone component.

Further, when observing the inorganic fiber sheet of the present invention after encapsulating it with an encapsulant (for example, when using it for research / evaluation purposes such as observing or analyzing cells infiltrated inside), the inorganic fiber is composed. It is preferable to match the refractive index of the inorganic component to the refractive index of the encapsulant. This is because the inorganic fiber sheet can be made transparent to some extent by matching the refractive indexes in this way, and the observability is excellent. The refractive index of this inorganic component can be adjusted to the refractive index of the mounting medium by the method described in JP-A-2014-173214.

On the other hand, inorganic fibers have excellent biocompatibility, and also contain an apatite component so that the infiltrated cells can exert high physiological activity by reproducing the bone environment. This apatite component is, that is, calcium phosphate, for example, hydroxyapatite, carbonate apatite, fluoride apatite, apatite chloride, calcium diphosphate dihydrate, calcium dibasic phosphate, calcium α-triphosphate, calcium β-calcium phosphate, calcium deficiency. Examples thereof include hydroxylapatite, carbon-added apatite, chlorapatite, whitrokit, calcium tetraphosphate, oxyapatite, calcium β-pyrophosphate, calcium α-calcium phosphate, calcium γ-calcium phosphate, and calcium phosphate VIII. Among these, hydroxyapatite is the main component of bone and is suitable because it easily reproduces the bone environment.

The apatite component may have any shape, but may have a particle shape. For example, the apatite component can be spherical. When having such a particle shape, the average particle size of the apatite component is preferably smaller than the average fiber diameter of the inorganic fiber so that the apatite component can be uniformly dispersed in the inorganic fiber. .. For example, when the average fiber diameter of the inorganic fiber is 1.5 μm or more, the average particle size of the apatite component is preferably less than 1.5 μm, more preferably less than 1.0 μm, and 0.8 μm or less. It is more preferable to have it. When observing the inorganic fiber sheet after encapsulating it with an encapsulant, the average particle size of the apatite component is preferably 0.8 μm or less, and 0.5 μm or less so as not to hinder the observability. Is more preferable. This "average particle size" is measured using a laser diffraction / scattering type particle size distribution measuring device (LMS-300: manufactured by Seishin Co., Ltd.), and is 50% in the number-based integral curve with respect to the obtained particle size. It means the particle size corresponding to the standard integrated value.

The inorganic fiber constituting the inorganic fiber sheet of the present invention contains the above-mentioned inorganic component and apatite component, but the apatite component has excellent biocompatibility and the infiltrated cells can exhibit high physiological activity. As described above, the amount of the apatite component in the inorganic fiber is preferably 10 mass% or more, more preferably 15 mass% or more, and further preferably 20 mass% or more. On the other hand, if the ratio of the apatite component is too high, the strength of the inorganic fiber is lowered, and as a result, the inorganic fiber sheet tends to be poorly handled. Therefore, it is preferably 70 mass% or less.

The inorganic component and the apatite component may exist in any way, but the apatite component has excellent biocompatibility due to the apatite component and the infiltrated cells can exert high physiological activity. Is present on the surface of the inorganic fiber and is preferably exposed.

As described above, the inorganic fiber of the present invention contains an inorganic component and an apatite component, but it is not decomposed or denatured by heat treatment at high temperature or γ-ray treatment, and is not impaired in biocompatibility. , May contain organic components. However, in the inorganic fiber of the present invention, the inorganic component and the apatite component preferably occupy 90 mass% or more, more preferably 95 mass% or more, and consist of only the inorganic component and the apatite component (100 mass%). Is the most preferable.

The average fiber diameter of the inorganic fiber of the present invention is not particularly limited, but the surface area is large, the biocompatibility is excellent, and the infiltrated cells and the apatite component have a certain contact area and have high physiological activity. It is preferably 0.6 μm or more, more preferably 0.8 μm or more, and further preferably 1.0 μm or more so that it can be exhibited and that it is excellent in strength. On the other hand, the average fiber diameter is preferably 20 μm or less so as not to impair the biocompatibility and to prevent the interaction between infiltrated cells from being hindered by the fibers. The "average fiber diameter" in the present invention means the arithmetic mean value of the fiber diameter at 50 points, and the "fiber diameter" means the length orthogonal to the extending direction of the fiber measured based on the micrograph. ..

The inorganic fiber of the present invention can form a uniform pore diameter when it has a fiber sheet structure, so that a uniform cell infiltration path can be formed, and the infiltrated cells and the apatite component on the fiber surface come into uniform contact. It is preferable that the fiber diameters are uniform so as to be possible. More specifically, the coefficient of variation (CV value) of the fiber diameter is preferably 0.7 or less, and more preferably 0.5 or less. The coefficient of variation of the fiber diameter is a value obtained by dividing the standard deviation (σ) of the fiber diameter by the average fiber diameter (md).

The fiber length of the inorganic fiber of the present invention is not particularly limited, but is preferably 0.5 mm or more, and more preferably 1.0 mm or more. In particular, it is most preferable that the fibers are substantially continuous fibers so that the fibers are less likely to fall off and the mechanical strength is excellent. This "substantially continuous fiber" means that the end portion of the inorganic fiber cannot be confirmed when an electron micrograph of 1000 times is taken.

Since the inorganic fiber sheet of the present invention contains the above-mentioned inorganic fibers and has an excellent tensile strength of 0.2 MPa or more, it is excellent in handleability. The stronger the tensile strength, the better the handleability. Therefore, it is preferably 0.25 MPa or more, more preferably 0.3 MPa or more, further preferably 0.35 MPa or more, and 0. It is more preferably .40 MPa or more, and further preferably 0.45 MPa or more. The stronger the strength, the better the handleability. Therefore, the upper limit is not particularly limited.

For this tensile strength, the maximum load of the inorganic fiber sheet (test piece) until it breaks is measured for five test pieces, and the arithmetic mean value is divided by the cross-sectional area of the inorganic fiber sheet (test piece). It is a quotient. The maximum load until fracture is a value measured under the following conditions, and the cross-sectional area is a value calculated from the product of the width and thickness of the inorganic fiber sheet (test piece) at the time of measurement.
Measuring device: Constant speed extension type tensile tester (manufactured by Orientec, UCT-100)
Specimen size: 5 mm width x 70 mm length Chuck spacing: 50 mm
Tensile speed: 50 mm / min.

The higher the content of the inorganic fiber in the inorganic fiber sheet of the present invention, the better the biocompatibility, and the higher the physiological activity of the infiltrated cells can be exhibited. Therefore, the inorganic fiber is 90 mass% in the inorganic fiber sheet. It preferably occupies the above, more preferably 95 mass% or more, and is composed of only inorganic fibers (100 mass%) so that it is not easily decomposed or modified by heat treatment at high temperature or γ-ray treatment. Is the most preferable.

The fibers other than the above-mentioned inorganic fibers that can form an inorganic fiber sheet are not particularly limited, but for example, an inorganic fiber that is composed of an inorganic component that can form an inorganic fiber and does not contain an apatite component is used. Can be mentioned.

The inorganic fiber sheet of the present invention contains the above-mentioned inorganic fibers, but the form thereof is not particularly limited. For example, it can be a non-woven fabric form, a woven fabric form, or a knitted form. Among these, the non-woven fabric form is preferable because the inorganic fibers can be uniformly dispersed and the pore diameters can be uniform.

In the case of a non-woven fabric form suitable as described above, it is preferable that the inorganic fibers are entangled and / or adhered to each other to maintain the non-woven fabric form. For example, it is preferable that the inorganic fibers are bonded to each other by sintering the inorganic components constituting the inorganic fibers. The entanglement of the inorganic fibers does not have to be a forced entanglement due to an external force such as a water flow. For example, the entanglement of the precursor inorganic fibers that occurs when the spun precursor inorganic fibers are directly accumulated. It may be.

The inorganic fiber sheet of the present invention preferably has a porosity of 80% or more so that the inside of the sheet can be effectively utilized. For example, when an inorganic fiber sheet is used as a culture substrate, cells can grow into the inside of the inorganic fiber sheet, so that three-dimensional culture is possible. In addition, when used as a filler at the treatment site, osteoblasts easily infiltrate into the inside, and the filler itself contains apatite, which is a component of bone having a high affinity with osteoblasts, so that the infiltrated bone It is easy to exert the bone formation function of osteoblasts, and bone regeneration at the treatment site can be promoted at an early stage. The higher the porosity, the more effectively the inside of the sheet can be utilized. Therefore, the porosity is more preferably 85% or more, and further preferably 90% or more. On the other hand, if the porosity is too high, the strength tends to be weak and it tends to be difficult to handle. Therefore, it is preferably 99% or less. This porosity P (unit:%) refers to a value obtained from the following equation.
P = 100- (Fr1 + Fr2 + ... + Frn)
Here, Frn indicates the filling rate (unit:%) of the component n constituting the inorganic fiber sheet, and refers to a value obtained from the following formula.
Frn = [(M × Prn) / (T × SGn)] × 100
Here, M is the texture of the inorganic fiber sheet (unit: g / cm ² ), T is the thickness of the inorganic fiber sheet (unit: cm), and Prn is the component n in the inorganic fiber sheet (for example, the inorganic component, The abundant mass ratio of the apatite component, etc.) and SGn mean the specific gravity of the component n (unit: g / cm ³ ).

The basis weight of the inorganic fiber sheet of the present invention is not particularly limited, but it is preferably 6 g / m ² or more, more preferably 8 g / m ² or more so as to be excellent in handleability. It is more preferably 10 g / m ² or more. The higher the basis weight, the stronger the strength of the inorganic fiber sheet and the better the handleability. Therefore, the upper limit of the basis weight is not particularly limited. The "Metsuke" in the present invention refers to a value obtained by measuring the mass of an inorganic fiber sheet cut into 10 cm squares and converting it into a mass having a size of 1 m ² .

Further, the thickness of the inorganic fiber sheet of the present invention is not particularly limited, but it is preferably 60 μm or more, more preferably 70 μm or more, and 80 μm or more so as to be excellent in handleability. Is more preferable. The thicker the thickness, the stronger the strength of the inorganic fiber sheet and the better the handleability. Therefore, the upper limit of the thickness is not particularly limited. The "thickness" in the present invention refers to a value measured using a thickness gauge (manufactured by Mitutoyo Co., Ltd .: Code No. 547-401: measuring force 3.5 N or less).

In the inorganic fiber sheet of the present invention, the inorganic fibers are uniformly dispersed, and it is preferable that the inside of the inorganic fiber sheet has an average flow pore diameter that can be effectively used. For example, when an inorganic fiber sheet is used as a culture medium or a filler for a treatment site, the average flow pore size of the inorganic fiber sheet is the cell nucleus of a general cell so that cells can easily infiltrate into the inside of the inorganic fiber sheet. It is preferably 3 μm to 10 μm that can pass through.

Further, in the inorganic fiber sheet of the present invention, the inorganic fibers are uniformly distributed, the biocompatibility is uniformly excellent, and the average of the total pore diameters of the inorganic fiber sheets is such that the physiological activity can be uniformly exhibited. It is preferable that the pore diameters are uniform, such that the "pore diameter distribution", which means the ratio of the flow rate pore diameters, is 30% or more. More preferably, the pore size distribution is 35% or more, and even more preferably 40% or more.

The average flow rate pore size and pore size distribution mean values measured under the following conditions using a palm porometer (manufactured by Seika Sangyo Co., Ltd.) capable of measuring the pore size by the bubble point method.
Specimen size: 25 mm in diameter
Test solution: GALWICK (surface tension: 15.7 days / cm)

The inorganic fiber sheet of the present invention is not decomposed or modified by heat treatment at high temperature or γ-ray treatment, is chemically stable, and has a tensile strength of 0.2 MPa or more for handling. Since it has excellent properties, it can be suitably used in fields and applications that require biocompatibility. The inorganic fiber sheet can be used as it is in the sheet form, can be used after being molded into a three-dimensional form, or can be used after being pulverized into powder. When the inorganic fiber sheet is molded and used, if the inorganic component constituting the inorganic fiber is an amorphous silica component, it has an advantage of excellent flexibility and excellent workability.

For example, when used as a culture medium in drug discovery development or medical research fields, three-dimensional culture may be possible, which is useful. In particular, an inorganic fiber sheet having a high porosity of 80% or more is suitable because cells grow to the inside of the sheet and three-dimensional culture is possible.

Further, when the inorganic fiber sheet of the present invention is used as a filler in a treatment site in a prosthetic dentistry field or an artificial bone-related field, the filler itself contains apatite, which is a bone component having a high affinity with osteoblasts. , It is easy to exert the bone formation function of osteoblasts, and bone regeneration at the treatment site can be promoted at an early stage. In particular, when an inorganic fiber sheet having a void ratio of 80% or more is used as a filler in the treatment site, osteoblasts easily infiltrate into the inside, and the filler itself has a high affinity with osteoblasts. Since it contains apatite, which is a component of the above, it is easy to exert the bone-forming function of infiltrated osteoblasts, and bone regeneration at the treatment site can be promoted at an early stage.

When the inorganic fiber sheet of the present invention is used as a filler in the treatment site, the inorganic fiber sheet can be used in the form of a sheet, or can be molded and used according to the form of the treatment site. Inorganic fiber sheets can also be crushed and used in powder form. When the inorganic fiber sheet is molded and used, if the inorganic component constituting the inorganic fiber is an amorphous silica component, it has an advantage of excellent flexibility and excellent workability.

The inorganic fiber sheet of the present invention is, for example, spun a spinning solution containing a precursor inorganic component and an apatite component to form a precursor inorganic fiber, forms a precursor inorganic fiber sheet containing the precursor inorganic fiber, and then fires. By doing so, the precursor inorganic fiber can be made into an inorganic fiber, and an inorganic fiber sheet having a tensile strength of 0.2 MPa or more can be produced.

More specifically, first, a spinning solution containing a precursor inorganic component and an apatite component is prepared. This precursor inorganic component means a component that is a source of the inorganic component, and a precursor inorganic component that is a source of the above-mentioned inorganic component is prepared. For example, it is preferable to contain a silica component as an inorganic component, but in this case, it is preferable to prepare tetraethoxysilane as a precursor inorganic component.

On the other hand, although an apatite component is prepared, as described above, it is preferable to prepare hydroxyapatite as the apatite component, and apatite having a particle shape (particularly spherical shape) can be prepared. When the apatite component has a particle shape, the average particle size of the apatite component is preferably smaller than the desired average fiber diameter of the inorganic fiber. For example, in the case of producing an inorganic fiber sheet containing an inorganic fiber having an average fiber diameter of 1.5 μm or more, the average particle size of the apatite component is preferably less than 1.5 μm, preferably less than 1.0 μm. More preferably, it is 0.8 μm or less.

This spinning solution contains a precursor inorganic component and an apatite component, and the apatite component occupies 10 mass% or more of the inorganic fiber so that the apatite component can exhibit biocompatibility and high physiological activity of the infiltrated cells. The amount of the apatite component after firing is 10 mass% or more (more preferably 15 mass% or more, further preferably 20 mass% or more, preferably 70 mass% or less) so that the amount of the apatite component after firing is 10 mass% or more (more preferably 15 mass% or more, preferably 70 mass% or less). It is preferable to mix with the ingredients to prepare a spinning solution.

The solvent constituting the spinning solution may be any solvent that can dissolve or disperse the precursor inorganic component and the apatite component, and is not particularly limited, but for example, water; alcohol (for example, methanol, ethanol, etc.). , N, N-dimethylformamide, N, N-dimethylacetamide, or organic solvents such as N-methyl-2-pyrrolidone can be used alone or in admixture.

The spinning solution of the present invention may contain the precursor inorganic component and the apatite component as described above, but if it further contains an organic component, the precursor inorganic fiber described later is fired to obtain an inorganic fiber. At that time, the inorganic fiber is baked down with the decomposition of the organic component, and the apatite component is easily exposed on the fiber surface. Therefore, it is preferable to add the organic component to the spinning solution. This organic component may be decomposed during firing and is not particularly limited, and examples thereof include polyvinylpyrrolidone, maleic anhydride copolymer, and polyacrylonitrile. When an organic component is blended, 50 mass% or less (more preferably 40 mass% or less, still more preferably 30 mass) of the precursor inorganic fiber so that the inorganic fiber after firing does not become porous and the strength does not decrease. % Or less) is preferable.

Such a spinning solution is spun to form precursor inorganic fibers. The precursor inorganic fiber means a fiber that is a source of the inorganic fiber as well as the precursor inorganic component. The spinning method of the spinning solution is not particularly limited, but for example, a method of applying an electric field to the spinning solution to form fibers (electrostatic spinning method), or a method of applying gas to the spinning solution to form fibers. (For example, the method disclosed in Japanese Patent Application Laid-Open No. 2009-287138), a method of applying a gas and an electric field to the spinning liquid to form fibers, and the like can be mentioned. In particular, the electrostatic spinning method is suitable because the fiber diameter is small (average fiber diameter: 3 μm or less), the fiber diameters are uniform, and substantially continuous precursor inorganic fibers can be spun.

Next, a precursor inorganic fiber sheet containing the precursor inorganic fiber is formed by a conventional method. For example, when the precursor inorganic fiber sheet is in the woven form, it can be formed by weaving the precursor inorganic fibers in the continuous fiber form, and when it is in the knitted form, it is formed by knitting the precursor inorganic fibers in the continuous fiber form. In the case of a non-woven fabric form, the inorganic fibers in the continuous fiber form or the short fiber form can be assembled and combined to form. When the precursor inorganic fibers are formed by applying an electric field and / or gas to the spinning liquid as described above (particularly in the case of the electrostatic spinning method), the formed precursor inorganic fibers are directly accumulated to form a precursor. Inorganic fiber sheets can be formed. In particular, when the precursor inorganic fibers are directly integrated by the electrostatic spinning method to form the precursor inorganic fiber sheet, not only the fiber diameters are small and the fiber diameters are uniform, but also the pore diameters are uniform and the void ratio. However, there are many voids of 80% or more, and a precursor-inorganic fiber sheet in which precursor-inorganic fibers are entwined with each other can be formed to some extent. Moreover, it is suitable because it is easy to manufacture an inorganic fiber sheet having many voids having a void ratio of 80% or more.

When the strength of the precursor inorganic fiber sheet is insufficient and the handleability is poor, the precursor inorganic fibers can be bonded to each other by entanglement by a fluid flow or the like, adhesion by an adhesive, or the like.

The precursor inorganic fiber is wound as a continuous fiber, the precursor inorganic fiber is cut to a desired fiber length to obtain a short fiber, and then a fiber web is formed by a known dry method or wet method, and entangled by a fluid flow or the like. In that case, it can be bonded by adhesion with an adhesive or the like to form a precursor inorganic fiber sheet. However, since the inorganic fiber is preferably a continuous fiber, it is preferable to directly collect and accumulate the continuous precursor inorganic fiber to form a precursor inorganic fiber sheet.

Then, by firing the precursor inorganic fiber sheet, the precursor inorganic fiber can be made into an inorganic fiber, and an inorganic fiber sheet having a tensile strength of 0.2 MPa or more can be produced. By carrying out this firing treatment, in addition to converting the precursor inorganic component of the precursor inorganic fiber into an inorganic component as an inorganic component, the intersections of the precursor inorganic fibers are sintered and the strength of the inorganic fiber sheet is increased. Is improved. This firing process can be carried out using, for example, a sintering furnace, and the temperature thereof is appropriately set depending on the precursor inorganic component. In general, the firing temperature is preferably 600 ° C. or higher, more preferably 700 ° C. or higher, and even more preferably 800 ° C. or higher.

If necessary, various post-processing can be carried out. For example, the thickness can be adjusted by passing between a pair of rolls, and the inorganic fiber sheet can be cut into a desired shape by using a punching die or a laser. Further, a silane coupling agent such as 3-aminopropyltriethoxysilane is applied to an inorganic fiber sheet, laminated on a base material, and then heat-treated (for example, at a temperature of about 50 ° C.) to be subjected to a coupling reaction. It is also possible to bond the inorganic fiber sheet and the base material.

As described above, the inorganic fiber sheet of the present invention can be produced, but when the apatite component is in the particle form, it is present not only inside the inorganic fiber but also on the fiber surface during spinning and is easily exposed. .. If the degree of exposure of the apatite component is insufficient, or if it is desired to increase the degree of exposure, a part of the inorganic component can be dissolved and removed. For example, when the inorganic component is composed of a silica component, the degree of exposure of the apatite component can be increased by immersing it in an alkaline solution. From another point of view, the degree of exposure of the apatite component can be adjusted by adjusting the dissolution and removal conditions with the alkaline solution.

The above is an example of the method for producing an inorganic fiber sheet of the present invention. When the inorganic fiber sheet is encapsulated with an encapsulant, the refractive index of the inorganic component constituting the inorganic fiber is the refractive index of the encapsulant. It is preferable to produce the fiber by the method described in JP-A-2014-173214 so as to have the same level as the above. That is, (1) the first spinnable sol solution (first precursor inorganic component solution) which is a raw material of the first inorganic oxide having a refractive index higher or lower than the refractive index of the encapsulant, and the refractive index of the encapsulant. A second spinnable sol solution or a metal salt solution (second precursor inorganic component solution), which is a raw material of a second inorganic oxide having a lower or higher refractive index, is mixed and spinnable without gelation. A step of preparing a mixed sol solution (precursor inorganic component solution), (2) a step of mixing an apatite component with the spinnable mixed sol solution (precursor inorganic component solution) to prepare a spinning solution, and (3) blending the spinning solution. A step of forming a precursor inorganic fiber by spinning by a spinning method such as an electrostatic spinning method to form a precursor inorganic fiber sheet containing the precursor inorganic fiber. (4) The precursor inorganic fiber sheet is fired to be inorganic. It is preferably produced by the process of producing a fiber sheet.

In addition, the inorganic fiber sheet containing fibers other than the inorganic fibers containing the inorganic component and the apatite component is different from the precursor inorganic fibers before and after accumulating the formed precursor inorganic fibers. It can be produced by supplying the fibers of the above, or by mixing with the precursor inorganic fibers of short fibers to form a fiber web.

Examples of the present invention will be described below, but the present invention is not limited to the following examples.

(Example 1)
Tetraethyl orthosilicate, water, hydrochloric acid and alcohol were mixed at a molar ratio of 1: 2: 0.0025: 5 and heated and stirred at a temperature of 80 ° C. for 15 hours. Then, it was concentrated to a silica concentration of 44 mass% by an evaporator and then thickened to a viscosity of 200 to 300 mPa · s to obtain a silica sol solution.

Then, hydroxyapatite was added to the silica sol solution so that the mass ratio of the calcined silica to hydroxyapatite (average particle size: 150 nm) was calculated to be 5: 3, and a sol solution A was obtained.

Further, polyvinylpyrrolidone was dissolved in N, N-dimethylformamide to prepare a solution B having a solid content of 30 mass%.

Next, the solution B was blended with the sol solution A (solid content: 45 mass%, solvent: ethanol) so that the mass ratio of the solid content was 3: 1 to obtain a spinning solution A.

Using the obtained spinning solution A, the precursor silica-based fibers were electrostatically spun under the following spinning conditions, and then directly accumulated on the drum collector to form the precursor silica-based fiber sheet.

(Electrostatic spinning conditions)
・ Discharge amount from nozzle: 1 g / hour ・ Distance between nozzle tip and drum collector: 10 cm
-Temperature and humidity in the spinning container: 25 ° C / 30% RH
・ Voltage applied to nozzle: + 10kV

Then, the precursor silica-based fiber sheet is calcined at a temperature of 800 ° C. for 2 hours using a calcining furnace to carry out a silica-based fiber (average particle diameter: 150 nm) and a silica-based fiber composed of only an amorphous silica component. Average fiber diameter: 1.5 μm, substantially continuous fiber, fiber diameter CV value: 0.15, hydroxyapatite ratio: 20 mass%) 100 mass%, silica-based fibers in the form of non-woven fabric A fiber sheet was obtained. The physical properties of this silica-based fiber sheet are as shown in Table 1.

(Comparative Examples 1 to 3)
Tetraethyl orthosilicate, water, and hydrochloric acid were mixed at a molar ratio of 1: 2: 0.0025 and heated and stirred at a temperature of 80 ° C. for 15 hours. Then, it was concentrated to a silica concentration of 44 mass% by an evaporator and then thickened to a viscosity of 200 to 300 mPa · s to obtain a silica sol solution.

Next, using the silica sol solution, the precursor silica-based fibers were electrostatically spun under the following spinning conditions, and then directly accumulated on the drum collector to form the precursor silica-based fiber sheet.

(Spinning conditions)
・ Discharge amount from nozzle: 1 g / hour ・ Distance between nozzle tip and drum collector: 10 cm
-Temperature and humidity in the spinning container: 25 ° C / 30% RH
・ Voltage applied to nozzle: + 10kV

Then, the precursor silica fiber sheet was fired at temperatures of 250 ° C. (Comparative Example 1), 500 ° C. (Comparative Example 2), and 800 ° C. (Comparative Example 3) for 2 hours using a firing furnace. Silica-based fiber composed of only an amorphous silica component (average fiber diameter: 0.8 μm, substantially continuous fiber, CV value of fiber diameter: 0.24) 100 mass%, and a non-woven fabric form in which silica-based fibers are sintered. Silica-based fiber sheet was obtained.

Then, each silica-based fiber sheet was immersed in a simulated body fluid at a temperature of 40 ° C. for one week and then dried at a temperature of 105 ° C. to obtain a silica-based fiber sheet treated with the simulated body fluid. The physical properties of these treated silica-based fiber sheets are as shown in Table 1.

(Measurement of hydroxyapatite ratio)
Crystallinity of silica-based fiber sheets of Examples 1 and Comparative Examples 1 to 3 under the following conditions using an X-ray diffractometer [desktop X-ray diffractometer: MiniFlex (registered trademark) 600, manufactured by Rigaku Co., Ltd.] Was obtained, and the ratio of crystallinity was defined as the hydroxyapatite ratio. These results are as shown in Table 1.

(Measurement condition)
2θ measurement range: + 3 to 90 °
Tube voltage: 30kV
Tube current: 15mA

(Measurement of average flow pore diameter and pore diameter distribution)
The average flow rate pore diameter and pore diameter distribution of the silica fiber sheets of Examples 1 and Comparative Examples 1 to 3 were measured using a palm poromometer (manufactured by Seika Sangyo Co., Ltd.) under the following conditions. These results are as shown in Table 1.
Specimen size: 25 mm in diameter
Test solution: GALWICK (surface tension: 15.7 days / cm)

(Drop test)
The silica-based fiber sheets of Examples 1 and Comparative Examples 1 to 3 were punched into a circle (diameter: 15 mm) to prepare test pieces. After that, the test piece was dropped from a height of 1 m, and the damaged state of the test piece was observed, and the case where the test piece was not damaged was evaluated as "◯" and the case where it was damaged was evaluated as "x". These results are as shown in Table 1.

(Observability test)
The silica-based fiber sheets of Examples 1 and Comparative Examples 1 to 3 were punched to a diameter of 15 mm to prepare test pieces. Next, after placing the test piece on a slide glass, a commercially available encapsulant [Neo-Mount® (Merck # 109016, refractive index: 1.46)] used for preparing a cell observation specimen is applied to the test piece. The test piece was further covered with a cover glass and sealed. Then, the enclosed test piece was observed with an optical microscope, and its transparency was evaluated according to the following criteria. These results are as shown in Table 1.

(Evaluation criteria)
◯: The inorganic fiber sheet becomes completely transparent and does not affect the observed image.
Δ: The inorganic fiber sheet is not completely transparent, but does not affect the information that the observer can obtain from the observation image.
X: The inorganic fiber sheet interferes with the observation and may have a significant influence on the information obtained from the observed image by the observer.

＃１：シリカ系繊維シートが脆く、測定不可能

# 1: Silica fiber sheet is brittle and cannot be measured

As is clear from Table 1, since the silica-based fiber sheet of the present invention is composed of a silica component and a hydroxyapatite component, it is not decomposed or modified by heat treatment at high temperature or γ-ray treatment, and is chemically stable. Moreover, although it contained 20 mass% of hydroxyapatite, it had a tensile strength of 0.2 MPa or more, was not damaged even when dropped, and was excellent in handleability.

On the other hand, the treated silica-based fiber sheet of Comparative Example 1 had a large amount of hydroxyapatite of 30 mass%, but the strength was so low that the tensile strength could not be measured and could not be handled. It was.

Further, the silica-based fiber sheets treated in Comparative Examples 2 and 3 in this order, which were fired at temperatures of 500 ° C. and 800 ° C., were able to measure the tensile strength and could be handled without being damaged in the drop test. However, the amount of hydroxyapatite was so small that it could not be detected, and the infiltrated cells could not exert high physiological activity.

Since the silica-based fibers constituting the silica-based fiber sheet of the present invention contained a silica component having a refractive index close to that of a commercially available encapsulant and an apatite component having a refractive index different from that of a commercially available encapsulant, they were completely absorbed by the encapsulant. However, since the average particle size of the apatite particles was small, the observability did not deteriorate significantly. On the other hand, in Comparative Example 1 fired at a temperature of 250 ° C., the sheet shape collapsed before the evaluation, and the evaluation could not be performed.

(Method and result of 3D culture)
In order to evaluate the imitation of the bone environment of the silica-based fiber sheet of the present invention, a culture evaluation using the human osteoblast cell line MG-63 was performed according to the following procedure.

First, as a culture vessel, a general 24-well plate for cell culture (hereinafter referred to as Reference Example 1) was prepared.

Further, the silica-based fiber sheet of Example 1 was punched into a circle having a diameter of 15 mm and then laid on the well bottom surface of a 24-well plate having a non-cell adhesive bottom surface.

Further, the silica-based fiber sheet before treatment was punched into a circle having a diameter of 15 mm with the simulated body fluid of Comparative Example 3, and then laid on the well bottom surface of a 24-well plate having a non-cell adhesive bottom surface.

Then, each well of 24-well plates were seeded with MG-63 cells at a density of 2.0 × ¹⁰ 5 cells / well. For culturing, EMEM medium (Eagle's minimum essential medium) containing fetal bovine serum and penicillin / streptomycin solution, which is an antibiotic, in a volume ratio of 10% and 1%, respectively, was used, and the amount of medium in each well was It was set to 1 mL / well.

After cell seeding, the cells were cultured in a humidified incubator at a temperature of 37 ° C. filled with 5% CO ₂ . The medium was changed daily, and the cells were cultured for a total of 18 days.

After culturing, the activity of alkaline phosphatase (ALP), which is known as a marker for differentiation of osteoblasts into mature osteoocytes, was measured.

That is, cells cultured for 1 day, 4 days, 7 days, 10 days, 14 days, and 18 days were lysed with 0.05% Triton X-100 aqueous solution, respectively, for the preparation of the measurement sample.

Then, freeze-thaw three times and ultrasonic crushing were performed to release ALP distributed on the cell membrane. Further, these were centrifuged (1000 × g, 5 minutes), and the supernatant was used as a measurement sample.

From this measurement sample, ALP activity and total protein amount were used from commercially available measurement kits, Lab Assay ^TM ALP (Wako Junyaku Co., Ltd., # 291-58601) and Pierce ^TM BCA Protein Assay Kit (Thermo Co., Ltd., # 23227). Was measured, and the ratio of ALP activity value (units / μL) / total protein amount (μg / μL) was calculated, respectively. These results were as shown in FIG. The results in FIG. 1 are shown as relative values when the ALP activity 1 day after culturing in Reference Example 1, which is a general culturing method, is set to 1.

As can be seen from FIG. 1, in Reference Example 1, which is a general culture method, there was almost no change in ALP activity during the culture period. On the other hand, when the silica-based fiber sheet before treatment was used in the simulated body fluid of Comparative Example 3, the ALP activity was improved according to the culture period. It is considered that this is because the three-dimensional nature of the silica-based fiber sheet causes three-dimensional contact between cells, and the in-vivo environment is imitated.

Furthermore, when the silica-based fiber sheet of Example 1 was used, the ALP activity was higher than that when the silica-based fiber sheet before treatment was used in the simulated body fluid of Comparative Example 3. It is considered that this is because the culture environment closer to the bone environment in the living body was reproduced by having the bone component (hydroxyapatite component) in addition to the three-dimensional culture environment.

The inorganic fiber sheet of the present invention is not decomposed or modified by heat treatment at high temperature or γ-ray treatment, is chemically stable, and has a tensile strength of 0.2 MPa or more for handling. Since it has excellent properties, it can be suitably used in fields and applications that require biocompatibility. For example, it can be used as a culture medium in drug discovery development and medical research fields, and as a filler in therapeutic sites in prosthetic dentistry fields and artificial bone-related fields. The inorganic fiber sheet can be used as it is in the sheet form, can be used after being molded into a three-dimensional form, or can be used after being pulverized into powder.

Claims (2)

A spinning liquid containing a precursor inorganic component and an apatite component is spun to form a precursor inorganic fiber, a precursor inorganic fiber sheet containing the precursor inorganic fiber is formed, and then the precursor inorganic fiber is formed into an inorganic fiber by firing. A method for producing an inorganic fiber sheet, which comprises using an inorganic fiber sheet having a tensile strength of 0.2 MPa or more. The precursor inorganic fibers is formed by an electrostatic spinning method, the formed by the precursor inorganic fibers integrated directly, and forming a precursor inorganic fiber sheet, the production of inorganic fiber sheet according to claim 1, wherein Method.

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