Chromatographic carrier using microfibers and method for producing same

Abstract

The present invention addresses the problem of providing a material which has sufficient strength, voids and surface area to serve as a chromatographic carrier, can increase the speeds of processes for purifying antibody drugs and the like, and can provide optimal purification processes for large materials used in gene therapies and exosome therapies. Provided are: a chromatographic carrier using a fiber structure comprising microfibers composed of at least one polymer component; and others. The average fiber diameter of the microfibers is preferably 1 μm or more but less than 20 μm, and the thickness of the fiber structure is preferably 100 μm to 2 mm inclusive. In addition, the fiber structure is preferably in the form of a stacked film, the film preferably has pores, and the diameters of the pores are preferably in the range of 0.1 μm to 30 μm inclusive.

Description

Microfiber support for chromatography and method for producing the same

[0001] The present invention relates to a chromatography support using microfibers and a method for producing the same.

[0002] Beads are the primary chromatographic carrier used for the separation and purification of biopharmaceuticals. Antibody drugs account for more than half of biopharmaceutical sales, but while they are expected to be effective, they are extremely expensive. One solution to making antibody drugs more widely available is to reduce costs by speeding up the purification process. Furthermore, nucleic acid drugs, gene therapy, and even exosome therapy are attracting attention as technologies beyond antibody drugs. Gene therapy and exosome therapy are medical technologies of the near future, but compared to conventional proteins and antibody drugs, the size of the objects to be purified is large, and the optimal purification process has yet to be established.

[0003] To speed up the purification process, nanofibers with high porosity and surface area are being increasingly used as chromatography carriers (Patent Documents 1 and 2). Furthermore, to ensure a pore size sufficiently larger than the target capture substance for large-sized purification targets, studies are also underway to utilize existing fibers (average fiber diameter of several tens of micrometers) that have been used for purposes other than purification as chromatography carriers for virus purification (Patent Document 3).

[0004] JP 2016-534373 A JP 2016-507671 A JP 2018-059952 A

[0005] The application of nanofibers is considered useful for speeding up the purification process. However, nanofibers have low strength, and when used alone, they are difficult to handle and have low productivity issues. Furthermore, like small particle beads, nanofibers have higher pressure loss and are difficult to achieve thickness compared to existing fibers (fiber diameters of several tens of micrometers). On the other hand, when applying existing fibers (e.g., average fiber diameters of several tens of micrometers) to large purification targets, while the fiber diameter is large and provides low pressure loss, there are issues with the voids being too large, meaning there is a lot of space unused for purification.

[0006] In view of the above circumstances, an object of the present invention is to develop a chromatography carrier that has both sufficient strength and voids.

[0007] As a result of intensive research aimed at solving the above problems, the present inventors have found conditions for producing microfibers by electrospinning, which have a fiber diameter larger (higher strength) than nanofibers and a fiber diameter smaller than existing fibers (for example, with an average fiber diameter of several tens of micrometers), and have completed the present invention.

[0008] [1] A chromatography carrier using a fibrous structure composed of microfibers made of at least one polymer component. [2] The chromatography carrier according to item [1], wherein the microfibers have an average fiber diameter of 1 μm or more and less than 20 μm. [3] The chromatography carrier according to item [1], wherein the microfibers have an average fiber diameter of 1 μm or more and less than 10 μm. [4] The chromatography carrier according to any one of items [1] to [3], wherein the thickness of the fibrous structure is 100 μm or more and 2 mm or less. [5] The chromatography carrier according to any one of items [1] to [4], wherein the fibrous structure is in the form of a laminated membrane. [6] The chromatography carrier according to item [5], wherein the membrane has pores, and the pores have a diameter of 0.5 μm or more and 30 μm or less. [7] The chromatography carrier according to any one of items [1] to [6], wherein the microfibers comprise at least one selected from a cellulose derivative and a polyamide. [8] The chromatography carrier according to any one of items [1] to [6], wherein the microfibers comprise at least one selected from cellulose derivatives and polyamides, and at least one selected from polyethylene oxide and polyvinylpyrrolidone. [9] The chromatography carrier according to any one of items [1] to [8], wherein a ligand has been introduced into the microfibers.

[10] The chromatography carrier according to item [9], wherein the ligand is at least one selected from an ion exchange group and a functional polymer.

[11] The chromatography carrier according to item

[10] , wherein the ion exchange group and the functional polymer are at least one selected from quaternary ammonium, sulfonic acid, phosphate, and polylysine.

[12] The chromatography carrier according to item [9], wherein the ligand is at least one selected from protein A, protein G, and an antibody.

[13] A method for producing a microfiber, comprising: (a) a step of dissolving at least one polymer component in a mixed solvent of a solvent in which the polymer component is soluble and a solvent in which the polymer component is insoluble, to prepare a spinning solution containing the polymer component, and (b) a step of spinning the spinning solution by electrospinning to obtain microfibers, wherein in the step (b), the electrospinning is performed in a humidity environment of 30% or more and 60% or less.

[14] A method for producing a fiber structure, comprising: (a) a step of dissolving at least one polymer component in a mixed solvent of a solvent in which the polymer component is soluble and a solvent in which the polymer component is insoluble, to prepare a spinning solution containing the polymer component, (b) a step of spinning the spinning solution by electrospinning to obtain microfibers, and (c) a step of laminating the spun microfibers, wherein in the step (b), the electrospinning is performed in a humidity environment of 30% or more and 60% or less.

[15] The method for producing a microfiber according to item

[13] or the method for producing a fiber structure according to item

[14] , wherein the microfibers have an average fiber diameter of 1 μm or more and less than 20 μm.

[16] The method for producing a microfiber according to item

[13] or the method for producing a fiber structure according to item

[14] , wherein the microfibers have an average fiber diameter of 1 μm or more and less than 10 μm.

[17] The method for producing a microfiber according to any one of items

[13] to

[16] , wherein in step (a), a ratio of a solvent in which the polymer component is soluble to a solvent in which the polymer component is insoluble is adjusted to 85:15 to 20:80.

[0009] The present invention provides a chromatography carrier using microfibers that combines sufficient strength and porosity. The microfibers of the present invention have sufficient strength, porosity, and surface area for use as a chromatography carrier, making them a material that can speed up the purification process of antibody drugs and provide an optimal purification process for large purification targets used in gene therapy and exosome therapy. Furthermore, they do not require the know-how-required packing procedures required for bead-based packing materials, which also reduces the number of work steps.

[0010] Figure 1 is an SEM image of the microfiber obtained in Example 2 (photograph substitute for drawing, scale 1 is 5 μm). Figure 2 is an SEM image of the microfiber obtained in Example 3 (photograph substitute for drawing, scale 1 is 5 μm). Figure 3 is an SEM image of the microfiber obtained in Example 4 (photograph substitute for drawing, scale 1 is 5 μm). Figure 4 is a graph showing the influenza virus evaluation results of the fiber laminate membrane obtained in Example 5, and the chromatogram and the HA (hemagglutinin) titer of the flow-through fraction (Abs.: absorbance, Cond.: conductivity). Figure 5 is a graph showing the influenza virus evaluation results of the fiber laminate membrane obtained in Example 5, and the chromatogram and the HA titer of the flow-through fraction (Abs.: absorbance, Cond.: conductivity). Figure 6 shows the influenza virus evaluation results of the fiber laminate membrane obtained in Example 5, and is a graph showing the chromatogram and the HA titer of the permeate fraction (Abs.: absorbance, Cond.: conductivity). Figure 7 shows an SEM image of the microfiber obtained in Example 7 (photograph substitute for drawing, scale 1 is 5 μm). Figure 8 shows an SEM image of the microfiber obtained in Example 8 (photograph substitute for drawing, scale 1 is 5 μm). Figure 9 shows an SEM image of the microfiber obtained in Example 9 (photograph substitute for drawing, scale 1 is 5 μm). Figure 10 shows the influenza virus evaluation results of the fiber laminate membrane obtained in Example 10, and is a graph showing the chromatogram and the HA titer of the permeate fraction (Abs.: absorbance, Cond.: conductivity). Figure 11 shows the results of influenza virus evaluation of the fiber laminate membrane obtained in Example 10, and is a graph showing the chromatogram and the HA titer of the flow-through fraction (Abs.: absorbance, Cond.: conductivity). Figure 12 shows the results of influenza virus evaluation of the fiber laminate membrane obtained in Example 10, and is a graph showing the chromatogram and the HA titer of the flow-through fraction (Abs.: absorbance, Cond.: conductivity). Figure 13 is an SEM image of the nanofiber obtained in Comparative Example 1 (photograph substitute for drawing, scale 1 is 5 μm). Figure 14 is an SEM image of the nanofiber obtained in Comparative Example 2 (photograph substitute for drawing, scale 1 is 5 μm).

[0011] The present invention will be described below. As mentioned above, bead-shaped carriers are the mainstream for chromatography. Meanwhile, therapeutic technologies are shifting from small molecule / protein drugs to more effective antibody and nucleic acid drugs, and technological development is also progressing in gene therapy and exosome therapy. Antibody and nucleic acid drugs are highly effective, but their production costs are high, and cost-reduction technologies are required. In addition, viral vectors and exosomes used in gene therapy are large in size, making it difficult to say that conventional carriers (beads) are optimal.

[0012] To solve these problems, the present invention considers the application of fibers to chromatography carriers. Prior art has used nanofibers, but nanofibers have low strength and may not have sufficient porosity for large purification targets such as exosomes. Therefore, it was thought that using microfibers would provide sufficient strength and porosity, enabling high throughput (low cost).

[0013] In this specification, the term "microfiber" refers to a fiber having an average fiber diameter of 1 μm or more, and an average fiber diameter on the order of micrometers.

[0014] <Chromatography Carrier> One aspect of the present invention relates to a chromatography carrier using a fibrous structure composed of microfibers made of at least one polymer component (hereinafter, sometimes referred to as the "chromatography carrier of the present invention").

[0015] The microfibers obtained by the present invention are microfibers made of at least one polymer component. The polymer component is not limited as long as it can form microfibers, but specifically includes, for example, at least one selected from cellulose derivatives and polyamides.

[0016] As the cellulose derivative, conventionally known cellulose derivatives can be used, and specific examples include methyl cellulose, ethyl cellulose, butyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxybutyl methyl cellulose, carboxymethyl cellulose, cellulose acetate (cellulose acetate), cellulose acetate butyrate, cellulose acetate propionate, triacetyl cellulose, nitrocellulose, and cationized cellulose. In particular, cellulose acetate (cellulose acetate) is included. The cellulose derivative may include at least one selected from the cellulose derivatives.

[0017] As the polyamide, conventionally known polyamides can be used, and specific examples include nylon 4, nylon 6, nylon 7, nylon 11, nylon 12, nylon 66, and nylon 610. In particular, nylon 6 can be used. The polyamide may include at least one selected from polyamides.

[0018] The content of at least one selected from cellulose derivatives and polyamides in the polymer component may be 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 99% or more, or 100%.

[0019] The microfibers may contain, but are not limited to, at least one selected from cellulose derivatives and polyamides, as well as a fiber-forming polymer for the purpose of improving spinnability. The fiber-forming polymer may be selected from those that are soluble in the spinning solvent, as long as it promotes fiber formation from the spinning solution. Examples of the fiber-forming polymer include polyvinyl alcohol, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, polylactic acid, polyglycolic acid, polycaprolactone, chitin, chitosan, collagen, and copolymers or mixtures thereof. These fiber-forming polymers may be used alone or in combination of two or more. From the viewpoint of solubility in the solvent, the fiber-forming polymer is preferably polyvinyl alcohol, polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, or polyacrylic acid, and more preferably polyethylene oxide or polyvinylpyrrolidone.

[0020] The content of fiber-forming polymer in the polymer component may be 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 1% or less, or 0%.

[0021] The microfiber of the present invention may contain a bead structure, and the bead contained in the microfiber may be formed from a single bead or may be a roughly spherical mass with an uneven surface formed by the aggregation of many smaller particles.

[0022] The microfibers and beads may exist independently, or may be held together by the beads entering voids in the matrix formed by the microfibers, or may be formed by the beads being formed by the swelling of parts of the microfibers, i.e., the fibers and beads may be strung together (like beads). Both forms may also be mixed. Typically, the form in which beads are mixed in the microfiber matrix and the form in which they are strung together like beads are mixed.

[0023] The beads contained in the microfibers increase the entanglement area of ​​the fibers in the membrane formed by stacking the fiber structure, strengthening the structure and supporting the membrane to prevent it from collapsing. Furthermore, the size and distribution of voids in the fiber structure can be adjusted, improving the liquid permeability.

[0024] The microfibers and beads may be made of the same or different components, but from the viewpoints of uniformity of the composite structure and stability during production, it is preferable that they are made of the same component. Specifically, it is preferable that they are made of resins of the same component.

[0025] The microfibers obtained by the present invention have an average fiber diameter of 1 μm or more. The average fiber diameter is not limited, but may be, for example, 1 μm or more, 2 μm or more, or 10 μm or more, or less than 30 μm, less than 20 μm, or less than 10 μm, or any combination thereof that is compatible. The average fiber diameter of the microfibers obtained by the present invention may be, for example, 1 μm or more but less than 20 μm, 1 μm or more but less than 10 μm, or 1 μm or more but less than 3 μm. The fiber form may be long fibers, short fibers, fibrils, straight or curved rods, or the like. A smaller average fiber diameter is preferable because it increases the specific surface area. An average fiber diameter of less than 20 μm is preferable because, when a sufficient fiber structure is formed, a sufficient specific surface area and large voids are obtained as a chromatography carrier, thereby achieving high purification efficiency for large purification targets. An average fiber diameter of less than 10 μm or less than 5 μm is even more preferable. Furthermore, although the mechanical strength per fiber increases as the average fiber diameter increases, an average fiber diameter of 1 μm or more is preferred because it provides satisfactory material strength and handleability. The average fiber diameter can be measured by a known method, for example, by calculation based on an SEM image.

[0026] The microfibers can be produced, for example, by the method described below in <Production method of microfibers and fiber structures>.

[0027] <<Fiber Structure>> The microfibers obtained by the present invention can be accumulated (e.g., laminated) to form a fiber structure. The form of the fiber structure is not particularly limited, but is typically a nonwoven fabric, and can be any form of nonwoven fabric, such as a membrane, film, sheet, block, or sphere. The fiber structure may be composed of only microfibers, or may be composited with other materials. The fiber structure may also contain residual components, such as solvents and catalysts, used in the manufacturing process.

[0028] The thickness of the fiber structure (also referred to as a fiber assembly in the case where spun microfibers are stacked on a collector and collected as described below) is, for example, 100 μm to 3000 μm, or 200 μm to 2000 μm. Within these ranges, sufficient strength and voids as a chromatography carrier are likely to be obtained. Generally, in electrospinning of nanofibers with small fiber diameters, it is difficult to uniformly stack the fibers due to electric field repulsion, and it is not possible to increase the thickness of the fiber structure. The microfibers of the present invention, for reasons that are unclear, have low repulsion between fibers and are easy to stack, making it possible to form a thick fiber structure. Furthermore, the fiber structure obtained by the present invention has pores (voids), and the void size is, for example, 0.5 μm to 30 μm, or 1 μm to 20 μm in average diameter. Within these ranges, sufficient strength and voids as a chromatography carrier applicable to larger purification targets are likely to be obtained. The thickness and void size of the fiber structure can be measured by known methods. The thickness of the fiber structure can be measured using an SEM image or a laser thickness meter, and the void size can be measured and calculated using a Capillary Flow Porometer manufactured by POROUSMATERIAL.

[0029] The fiber structure can be produced, for example, by the method described later in <Production method of microfibers and fiber structures>.

[0030] The fibrous structure obtained by the present invention has both sufficient strength and voids as a chromatography carrier. Utilizing this characteristic, the fibrous structure can be used as a chromatography carrier in the separation and purification of various substances. The fibrous structure may be used as a chromatography carrier as is, or may be further subjected to a saponification reaction, a crosslinking reaction, or modified with a substituent.

[0031] By saponifying and crosslinking the fiber structure, it is possible to impart mechanical strength and flow rate resistance sufficient for use as a chromatography packing. The crosslinking treatment of the fiber structure can be carried out with reference to JP 2009-242770 A. By appropriately changing the design of the experimental conditions, it is possible to impart the desired mechanical strength and flow rate resistance.

[0032] Furthermore, by adding a ligand to at least a portion of the reactive functional groups of the fiber structure obtained by the present invention, an adsorbent capable of adsorbing various substances can be easily obtained. For example, the fiber structure can be used as a virus adsorbent for influenza virus, hepatitis virus, rabies virus, human papillomavirus, adeno-associated virus, etc., an adsorbent for purifying antibody drugs, an exosome adsorbent, a nucleic acid adsorbent, etc. Specifically, by saponifying and crosslinking the fiber structure obtained by the present invention and then introducing a sulfated polysaccharide, a chromatography packing suitable for separating or purifying virus particles can be provided. The introduction of sulfated polysaccharides can be carried out with reference to, for example, JP 2011-220992 A. Examples of other ligands include, but are not limited to, ion exchange groups such as 2-diethylaminoethyl (DEAE), carboxymethyl (CM), sulfonic acid, phosphate, and quaternary ammonium (Q); hydrophobic groups such as phenyl and butyl; ligands having both ion exchange and hydrophobic groups and usable for so-called mixed-mode separation; ligands for protein adsorption such as protein A, protein G, and antibodies; polycations such as polylysine; and functional polymers such as polyanions such as heparin and polyglutamic acid. These can be selected as desired depending on the intended use of the fiber structure, and can be introduced as desired according to known methods.

[0033] The adsorption performance of the chromatography carrier of the present invention against influenza viruses can be evaluated, for example, by the method described in JP 2011-220992 A. Influenza viruses that can be used for evaluation include type A and type B influenza viruses derived from embryonated chicken eggs and influenza viruses derived from cultured cells such as MDCK cells.

[0034] <Method for producing microfibers and fiber structures> One aspect of the present invention relates to a method for producing microfibers, comprising: (a) a step of dissolving at least one polymer component in a mixed solvent of a solvent in which the polymer component is soluble and a solvent in which the polymer component is insoluble, to prepare a spinning solution containing the polymer component; and (b) a step of spinning the spinning solution by electrospinning to obtain microfibers, wherein in step (b), the electrospinning is performed in a humidity environment of 30% or more and 60% or less (hereinafter, this method may be referred to as the "method for producing the microfibers of the present invention").

[0035] A further aspect of the present invention relates to a method for producing a fiber structure, the method including: (a) a step of dissolving at least one polymer component in a mixed solvent of a solvent in which the polymer component is soluble and a solvent in which the polymer component is insoluble, to prepare a spinning solution containing the polymer component; (b) a step of spinning the spinning solution by electrospinning to obtain microfibers; and (c) a step of stacking the spun microfibers, wherein in step (b), the electrospinning is performed in a humidity environment of 30% or more and 60% or less (hereinafter, this may be referred to as the "method for producing a fiber structure of the present invention").

[0036] [Step (a)] In step (a), a polymer component is dissolved in a mixed solvent of a solvent in which the polymer component is soluble (hereinafter referred to as a good solvent) and a solvent in which the polymer component is insoluble (hereinafter referred to as a poor solvent) at a temperature below the boiling point of the mixed solvent to obtain a spinning solution containing the polymer component.

[0037] Here, a good solvent refers to a solvent in which a solute dissolves and a clear solution containing no solids is obtained. Here, it refers to a solvent that can produce a solution with a concentration of 1% by weight or more, or even 10% by weight or more, at room temperature. On the other hand, a poor solvent refers to a solvent that has low affinity for the polymer and solute, and very weak interaction with the polymer molecules, resulting in extremely low dissolving ability. While it may swell the polymer, it refers to a solvent that cannot dissolve more than 0.01% by weight of the polymer by itself.

[0038] In the production method of the present invention, examples of the good solvent include ketones such as acetone and methyl ethyl ketone; chain esters and cyclic esters such as acetic acid, methyl acetate, ethyl acetate and γ-butyrolactone; nitrogen-containing compounds such as dimethylformamide, N,N-dimethylacetamide and N-methylpyrrolidone; glycols such as methyl glycol and methyl glycol acetate; ethers such as tetrahydrofuran, 1,3-dioxolane and dioxane; halogenated hydrocarbons such as chloroform and dichloromethane; dimethyl sulfoxide; and combinations of these.

[0039] In the production method of the present invention, examples of the poor solvent include glycol ethers such as ethylene glycol monomethyl ether and propylene glycol monomethyl ether, alcohols such as methanol and ethanol, water, and combinations thereof.

[0040] The mixing ratio of the good solvent to the poor solvent is not particularly limited, but may be, for example, a weight ratio of the good solvent to the poor solvent of 85:15 to 20:80, or 50:50 to 20:80.

[0041] The proportion (content) of the polymer component in the spinning solution is not particularly limited, and may be, for example, more than 0% by weight, 1% by weight or more, or 10% by weight or more, or 17.5% by weight or less, 17% by weight or less, or 15% by weight or less, or any combination thereof that is not contradictory, relative to the spinning solution. Specifically, the content of the polymer component in the spinning solution may be, for example, more than 0% by weight and 17.5% by weight or less, or 1% by weight or more and 17% by weight or less.

[0042] In step (a), the ratio of the solvent in which the polymer component is soluble to the solvent in which the polymer component is insoluble is preferably adjusted to 85:15 to 20:80. In step (a), the concentration of the polymer component contained in the spinning solution is preferably adjusted to more than 0 wt % and not more than 17.5 wt %. By adjusting the concentration within this range, stable microfibers having a uniform fiber diameter of 1 μm or more can be efficiently obtained.

[0043] [Step (b)] In step (b), the prepared spinning solution is spun by electrospinning to obtain microfibers.

[0044] The microfibers obtained in the present invention are produced by electrospinning, which is characterized by having a relatively high surface area and porosity, since fibers of uniform diameter are easily formed and high-quality fiber structures can be obtained.

[0045] Electrospinning is a fiber spinning method known as electrospinning, electrospinning, or electrospray. The electrospinning method is not particularly limited, and examples thereof include commonly known methods such as a needle method using one or more needles, an air blow method in which an airflow is sprayed onto the tip of a needle to improve productivity per needle, a multi-hole spinneret method in which a single spinneret is provided with multiple solution discharge holes, a free surface method in which a cylindrical or spiral wire-shaped rotating electrode is semi-immersed in a solution bath, a wire electrode method in which electrospinning is performed while applying a spinning solution to a wire electrode, and an electrobubble method in which electrospinning is performed starting from bubbles generated on the surface of a polymer solution by supplying air. The method can be appropriately selected in consideration of the desired quality, productivity, or operability of the microfiber.

[0046] The electrospinning method can be carried out by known means, including those described above. Specifically, a voltage is applied between a nozzle filled with the spinning solution and a collector (substrate), and the spinning solution is discharged from the nozzle, and fibers are collected on the collector. The conditions for electrospinning are not particularly limited and may be appropriately adjusted depending on the type of spinning solution and the application of the resulting microfibers.

[0047] The discharge rate of the spinning solution is not particularly limited, but is preferably 0.1 to 20 mL / hr. A discharge rate of 0.1 mL / hr or more is preferable because sufficient productivity can be obtained, and a discharge rate of 20 mL / hr or less is preferable because uniform and thin fibers can be easily obtained. The polarity of the applied voltage may be positive or negative. The magnitude of the voltage is not particularly limited as long as fibers are formed, and in the case of a positive voltage, a range of 5 to 100 kV can be exemplified. The distance between the nozzle and the collector is not particularly limited as long as fibers are formed, and a range of 5 to 20 cm can be exemplified. The inner diameter of the nozzle is not particularly limited as long as fibers are formed, and a range of 0.22 to 0.51 mm can be exemplified. The temperature and humidity of the spinning atmosphere are preferably controlled. The temperature range for electrospinning can be 0 to 50°C, and 20 to 40°C is more preferable. Humidity control is particularly important in electrospinning of microfibers, and it is preferable to set the humidity of the spinning atmosphere to 30% or more and 60% or less. By setting the humidity within this range, stable microfibers having a uniform fiber diameter of 1 μm or more can be efficiently obtained.

[0048] The fiber collection method in the electrospinning method is not particularly limited, and any known collection method can be used. For example, if a roll-to-roll collector is used as the fiber collection method, a long fiber sheet can be collected, and if a drum collector or disk collector that can rotate at high speed is used, an aligned fiber sheet in which fibers are aligned in one direction can be collected. As a method for collecting an aligned fiber sheet in which fibers are aligned, a method using parallel divided electrodes has also been reported, and this can also be used as a collector. Collection in a solution is also possible.

[0049] The collector in the electrospinning method is not particularly limited, and may be collected directly on a collector, collected in a solution, or collected on a substrate placed on a collector. Any substrate can be used as long as it is not a complete insulator, and examples thereof include nonwoven fabric, woven fabric, net, and microporous film, and are not particularly limited. When collected on a substrate, the structure of the substrate is not particularly limited, and may be a single-layer product or a multi-layer product consisting of two or more layers, which can be selected appropriately depending on the function and effect. When collected in a solution, the solution is not particularly limited as long as it is a solution in which the obtained microfibers are insoluble.

[0050] In the step (b), it is preferable to adjust the inner diameter of the spinning nozzle to 0.22 to 0.51 mm. By adjusting the inner diameter to this range, stable microfibers having a uniform fiber diameter of 1 μm or more can be efficiently obtained.

[0051] [Step (c)] In step (c), the microfibers produced in step (b) are laminated to obtain a fiber structure.

[0052] In addition, when step (b) involves spinning microfibers to obtain a fiber assembly in which the fibers are laminated, the lamination may be performed simultaneously with the spinning. That is, step (b) may also serve as step (c). Alternatively, the fiber assembly obtained by spinning may be further laminated, and adjacent microfibers may be fused together by compression and heating. The number of layers is not particularly limited, but may be, for example, 2 to 30 layers, or 3 to 10 layers. If the number of layers is 30 or more, the microfibers may not be fused together sufficiently, resulting in a laminate with insufficient strength.

[0053] Each step in the production method of the present invention can be appropriately carried out according to a known method, except that the specific conditions in the production method of the present invention are used.

[0054] The present invention will be specifically described below with reference to examples, but these are merely examples of the present invention and the scope of the present invention is not limited to these examples.

[0055] <Analysis Method> Analysis was performed based on the following method. (N Content Measurement) The ion-exchange group-introduced membrane was vacuum-dried overnight at 60°C, and 2 mg of the dried exchange group-introduced membrane was used as a sample. The N content was measured using an elemental analyzer Vario EL Cube (manufactured by Elementor). The measurement was performed three times, and the average value was used as the analysis result.

[0056] (HA Titer Measurement) 50 μL of 0.15 M NaCl aqueous solution was added to all wells of a round-bottom 96-well plate (8 rows x 12 columns). Subsequently, 50 μL of sample was added to wells in rows 1-7 of the first column, and 0.15 M NaCl aqueous solution was added as a control to wells in row 8 of the first column, mixed, and diluted 2-fold. 50 μL of the diluted solution was transferred to adjacent wells and mixed well. This procedure was repeated to create a 2- to 4096-fold dilution series up to the wells in row 12. Next, 50 μL of 0.5% chicken red blood cell suspension was added to all wells, mixed, and then allowed to stand at room temperature for approximately 60 minutes. The presence or absence of red blood cell agglutination was then confirmed. Specifically, when the plate was tilted, red blood cells in non-agglutinated wells flowed out, which was considered agglutination-negative, and if they did not flow out, which was considered agglutination-positive. The maximum dilution factor of the virus that showed agglutination-positive results was taken as the HA titer per 50 μL of sample.

[0057] Example 1: Preparation of microfibers and fiber laminates <1> Preparation of spinning solution for microfibers Cellulose acetate with a relative molecular weight of 29,000 g / mol was used. A mixed solvent was prepared by mixing N,N-dimethylacetamide (good solvent), 1,3-dioxolane (good solvent), and propylene glycol monomethyl ether (poor solvent) in a weight ratio of 12.5:22.5:65.0. 16.3 g of cellulose acetate and 0.006 g of sodium dodecyl sulfate were dissolved in 100 g of the mixed solvent at room temperature.

[0058] <2> Preparation of microfiber spinning solution Cellulose acetate with a relative molecular weight of 29,000 g / mol was used. The mixed solvent was prepared by mixing N,N-dimethylacetamide (good solvent), diacetone alcohol (good solvent), 1,3-dioxolane (good solvent), and propylene glycol monomethyl ether (poor solvent) in a weight ratio of 9.0:6.0:20.0:65.0. 16.3 g of cellulose acetate and 0.006 g of tetrabutylammonium bromide were dissolved in 100 g of the mixed solvent at room temperature.

[0059] <3> Preparation of microfiber spinning solution Cellulose acetate with a relative molecular weight of 29,000 g / mol was used. A mixed solvent was prepared by mixing diacetone alcohol (good solvent), 1,3-dioxolane (good solvent), and propylene glycol monomethyl ether (poor solvent) in a weight ratio of 12.5:22.5:65.0. 16.3 g of cellulose acetate and 0.006 g of tetrabutylammonium bromide were dissolved in 100 g of the mixed solvent at room temperature.

[0060] [Example 2] Preparation of microfibers The spinning solution prepared in Example 1<1> was supplied to a nozzle with an inner diameter of 0.41 mm by a gear pump at a rate of 7.5 mL / h under the conditions of a temperature of 26.5°C, a humidity of 40%, and a distance between the nozzle and the collector of 26 cm. A voltage of 20 kV was applied to the nozzle, and the microfiber was collected in a collector. The average fiber diameter was 1.27 μm (Figure 1).

[0061] [Example 3] Preparation of microfibers The spinning solution prepared in Example 1<2> was supplied to a nozzle with an inner diameter of 0.41 mm by a gear pump at a rate of 10.0 mL / h under the conditions of a temperature of 26.5°C, a humidity of 45%, and a distance between the nozzle and the collector of 26 cm. A voltage of 19 kV was applied to the nozzle, and the solution was collected in a collector. The average fiber diameter was 1.72 μm (Figure 2).

[0062] [Example 4] Preparation of microfibers The spinning solution prepared in Example 1<3> was supplied to a nozzle with an inner diameter of 0.41 mm by a gear pump at a rate of 10.0 mL / h under the conditions of a temperature of 26.5°C, a humidity of 45%, and a distance between the nozzle and the collector of 26 cm. A voltage of 19 kV was applied to the nozzle, and the solution was collected in a collector. The average fiber diameter was 2.73 μm (Figure 3).

[0063] <2> Fabrication of Fiber Laminate The fabricated microfibers were laminated by heating at 205°C under a pressure of 20 kPa for 30 minutes. The laminated membrane was hydrolyzed / deacetylated by immersing in a 0.025 M NaOH aqueous solution overnight. It was then dried at room temperature to fabricate a fiber laminate membrane.

[0064] The microfibers were observed using an SEM (Scanning Electron Microscope S3400N manufactured by Hitachi High-Technologies Corporation). A laminate of fibers having an average fiber diameter of single microns was obtained.

[0065] [Example 5] Evaluation of Fiber Laminate Membrane <1> Preparation of Ion-Exchange Group-Introduced Membrane <1-1> The microfiber laminate membrane of Example 2, measuring 5 cm in length and 5 cm in width, was placed in a PP container with a lid. Next, 39.5 g of ultrapure water was added and allowed to spread throughout the membrane. Then, 51.9 g of a 0.5 mol / L aqueous sodium hydroxide solution was added, followed by 11.6 g of a 71.6 wt % aqueous glycigyltrimethylammonium chloride solution. The container was then capped and shaken in a 40°C thermostatic chamber for 16 hours. After completion, the liquid inside the container was removed, and a sufficient amount of ultrapure water was added, followed by multiple washes until the wash solution became neutral. Next, the membrane was washed once with approximately 100 mL of a 1 M NaCl aqueous solution, followed by multiple washes with sufficient amounts of ultrapure water to obtain an exchange group-introduced membrane. The membrane thickness in the wet state was 2.6 mm. After the reaction, the membrane was stored in a wet state. The N content measured by an elemental analyzer was 1.1% by weight.

[0066] <1-2> The microfiber laminate membrane of Example 3, measuring 5 cm in length and 5 cm in width, was placed in a PP container with a lid. Next, 40.2 g of ultrapure water was added and allowed to soak throughout the membrane. Then, 53.3 g of 0.5 mol / L aqueous sodium hydroxide solution was added, followed by 11.9 g of 71.6 wt % aqueous glycigyltrimethylammonium chloride solution. The container was then capped and shaken in a 40°C thermostatic chamber for 16 hours. After completion, the liquid inside the container was removed, and a sufficient amount of ultrapure water was added, followed by multiple washes until the wash solution became neutral. The membrane was then washed once with approximately 100 mL of 1 M NaCl aqueous solution, followed by multiple washes with sufficient amounts of ultrapure water to obtain an exchange-group-introduced membrane. The membrane thickness in the wet state was 2.2 mm. After the reaction, the membrane was stored in a wet state. The N content measured using an elemental analyzer was 1.0 wt %.

[0067] <1-3> The microfiber laminate membrane of Example 4, measuring 5 cm in length and 5 cm in width, was placed in a PP container with a lid. Next, 39.2 g of ultrapure water was added and allowed to soak throughout the membrane. Subsequently, 51.9 g of a 0.5 mol / L aqueous sodium hydroxide solution was added, followed by 11.6 g of a 71.6 wt % aqueous glycigyltrimethylammonium chloride solution. The container was then capped and shaken in a 40°C thermostatic chamber for 16 hours. After completion, the liquid inside the container was removed, and a sufficient amount of ultrapure water was added thereto. The membrane was washed multiple times until the washing solution became neutral. Next, the membrane was washed once with approximately 100 mL of a 1 M NaCl aqueous solution, followed by multiple washes with sufficient amounts of ultrapure water to obtain an exchange-group-introduced membrane. The membrane thickness in the wet state was 2.3 mm. After the reaction, the membrane was stored in a wet state. The N content measured using an elemental analyzer was 1.1 wt %.

[0068] <2> Influenza virus evaluation <2-1> Purification of virus culture medium using affinity column Conditions: Virus culture medium: inactivated H1N1 influenza virus chicken egg culture medium Resin: Cellufine Sulfate (JNC Corporation) Column: Super Edge 5 mL Empty Mini Column (JNC Corporation) Buffer A: 10 mM Na phosphate buffer, pH 7.4 Buffer B: 10 mM Na phosphate buffer + 2 M NaCl, pH 7.4 System: AKTA avant25 (Cytiva)

[0069] Procedure (all performed at a flow rate of 1.25 mL / min): The resin was packed into a column and connected to the system. Using the system, 25 mL of equilibration solution (92.5% by volume of buffer A, 7.5% by volume of buffer B) was passed through the column, followed by 32 mL of virus culture solution previously filtered through a 0.45 μm syringe filter. After the virus solution was passed through, 25 mL of equilibration solution was passed through to wash out the unadsorbed fraction. Next, 20 mL of elution solution 1 (75% by volume of buffer A, 25% by volume of buffer B), followed by 20 mL of elution solution 2 (50% by volume of buffer A, 50% by volume of buffer B), and finally elution solution 3 (25% by volume of buffer A, 75% by volume of buffer B) were passed through to elute the adsorbed virus. The virus titer measured by HA titer was highest in the fraction of the elution solution 1 flow-through, at 512 HA titer / 50 μL. A 10 mL fraction of this effluent was obtained, and this fraction was used for the next evaluation of the ion-exchange group-introduced membrane.

[0070] <2-2> Purification of virus solution using ion-exchange group-introduced membrane Conditions: Virus solution: A solution obtained by diluting the affinity column eluate prepared in Example 5<2-1> 10 times with buffer C Membrane: Ion-exchange group-introduced membrane prepared in Example 5<1> Membrane holder: Omnifit® PTFE in-line filter holder (large) Packing: OD 2.0 cm, ID 1.6 cm (made of silicone rubber) Buffer C: 20 mM Tris-HCl + 100 mM NaCl, pH 7.5 Buffer D: 20 mM Tris-HCl + 1.5 M NaCl, pH 7.5 System: AKTA avant25 (Cytiva)

[0071] <2-2-1> Purification 1 Procedure (all procedures were performed at a flow rate of 1.0 mL / min): The membrane of Example 5 <1-1> was cut into a circle with a diameter of 2 cm and immobilized on a membrane holder by pressing the edges of the membrane with a gasket (effective membrane volume: 0.2 mL). The membrane holder was connected to the system, and 2 mL of equilibration buffer (buffer C) was passed through. Next, 16 mL of virus solution previously filtered through a 0.45 μm syringe filter was passed through. After washing with 6 mL of equilibration buffer, 8 mL of elution solution 1 (buffer C 70% by volume, D 30% by volume) was passed through, followed by 8 mL of elution solution 2 (buffer C 35% by volume, D 65% by volume), and finally elution solution 3 (buffer D) for elution. The results are shown in Figure 4 and Table 1. Despite the condition of a residence time of 0.2 minutes, 100% of the HA titer of the loaded virus was recovered in the fractions of elution solution 1.

[0072] <2-2-2> Purification 2 Procedure (all procedures were performed at a flow rate of 1.0 mL / min): The membrane of Example 5 <1-2> was cut into a circle with a diameter of 2 cm and immobilized on a membrane holder by pressing the edges of the membrane with a gasket (effective membrane volume: 0.2 mL). The membrane holder was connected to the system, and 2 mL of equilibration buffer (Buffer C) was passed through. Next, 16 mL of virus solution previously filtered through a 0.45 μm syringe filter was passed through. After washing with 6 mL of equilibration buffer, 8 mL of elution solution 1 (Buffer C 70% by volume, D 30% by volume) was passed through, followed by 8 mL of elution solution 2 (Buffer C 35% by volume, D 65% by volume), and finally elution solution 3 (Buffer D) for elution. The results are shown in Figure 5 and Table 1. Despite the condition of a residence time of 0.2 minutes, 100% of the HA titer of the loaded virus was recovered in the fractions of elution solution 1.

[0073] <2-2-3> Purification 3 Procedure (all procedures were performed at a flow rate of 1.0 mL / min): The membrane of Example 5 <1-3> was cut into a circle with a diameter of 2 cm and immobilized on a membrane holder by pressing the edges of the membrane with a gasket (effective membrane volume: 0.2 mL). The membrane holder was connected to the system, and 2 mL of equilibration buffer (Buffer C) was passed through. Next, 16 mL of virus solution previously filtered through a 0.45 μm syringe filter was passed through. After passing 6 mL of equilibration buffer to wash, 8 mL of elution solution 1 (Buffer C 70% by volume, D 30% by volume) was passed through, followed by 8 mL of elution solution 2 (Buffer C 35% by volume, D 65% by volume), and finally elution solution 3 (Buffer D) for elution. The results are shown in Figure 6 and Table 1. Despite the condition of a residence time of 0.2 minutes, 100% of the HA titer of the loaded virus was recovered in the fractions of elution solution 1.

[0074]

[0075] Example 6: Preparation of Polyvinylpyrrolidone-Containing Microfibers and Fiber Laminates <1> Preparation of Spinning Solution for Polyvinylpyrrolidone-Containing Microfibers Cellulose acetate with a relative molecular weight of 29,000 g / mol and polyvinylpyrrolidone with a weight-average molecular weight of 1,300,000 were used. Tetrabutylammonium bromide was used as the salt. A mixed solvent was prepared by mixing N,N-dimethylacetamide (good solvent), 1,3-dioxolane (good solvent), and propylene glycol monomethyl ether (poor solvent) in a weight ratio of 20:15:65. 15.7 g of cellulose acetate and 0.6 g of polyvinylpyrrolidone were dissolved in 100 g of the mixed solvent at room temperature.

[0076] <2> Preparation of spinning solution for polyvinylpyrrolidone-containing microfibers Cellulose acetate with a relative molecular weight of 29,000 g / mol and polyvinylpyrrolidone with a weight-average molecular weight of 1,300,000 were used. A mixed solvent was prepared by mixing N,N-dimethylacetamide (a good solvent), 1,3-dioxolane (a good solvent), and propylene glycol monomethyl ether (a poor solvent) in a weight ratio of 10:20:70. 15.7 g of cellulose acetate and 0.6 g of polyvinylpyrrolidone were dissolved in 100 g of the mixed solvent at room temperature.

[0077] [Example 7] Preparation of microfibers The spinning solution prepared in Example 6<1> was supplied to a nozzle with an inner diameter of 0.33 mm by a gear pump at a rate of 9.5 mL / h under the conditions of a temperature of 26.5°C, a humidity of 45%, and a distance between the nozzle and the collector of 20 cm. A voltage of 19 kV was applied to the nozzle, and the solution was collected in a collector. The average fiber diameter was 1.23 μm (Figure 7).

[0078] [Example 8] Preparation of microfibers The spinning solution prepared in Example 6<1> was supplied to a nozzle with an inner diameter of 0.33 mm by a gear pump at a rate of 10 mL / h under the conditions of a temperature of 26.5°C, a humidity of 45%, and a distance between the nozzle and the collector of 20 cm. A voltage of 19 kV was applied to the nozzle, and the microfiber was collected in a collector. The average fiber diameter was 1.33 μm (Figure 8).

[0079] [Example 9] Preparation of microfibers and fiber laminates <1> Preparation of microfibers The spinning solution prepared in Example 6<2> was supplied to a nozzle with an inner diameter of 0.41 mm at a rate of 8 mL / h using a gear pump under the conditions of a temperature of 26.5°C, a humidity of 45%, and a distance between the nozzle and the collector of 20 cm. A voltage of 19 kV was applied to the nozzle, and the microfiber was collected in a collector. The average fiber diameter was 2.82 μm (Figure 9).

[0080] <2> Fabrication of Fiber Laminate The microfibers fabricated in <1> were laminated by heating at 205°C under a pressure of 20 kPa for 30 minutes. The laminated membrane was hydrolyzed / deacetylated by immersing in a 0.025 M NaOH aqueous solution for 24 hours. The membrane was then dried at room temperature to fabricate a fiber laminate.

[0081] The microfibers were observed using an SEM (Scanning Electron Microscope S3400N manufactured by Hitachi High-Technologies Corporation). A laminate of fibers having an average fiber diameter of single microns was obtained.

[0082] [Example 10] Evaluation of Fiber Laminate Membrane <1> Preparation of Ion-Exchange Group-Introduced Membrane <1-1> The microfiber laminate membrane of Example 4, measuring 5 cm in length, 5 cm in width, and 1.51 mm in thickness, was placed in a PP container with a lid. Next, 41.85 g of ultrapure water was added and allowed to spread throughout the membrane. Then, 53.9 g of a 0.5 mol / L aqueous sodium hydroxide solution was added, followed by 12.05 g of a 71.6 wt% aqueous glycigyltrimethylammonium chloride solution. The container was then capped and shaken in a 40°C thermostatic chamber for 16 hours. After completion, the liquid inside the container was removed, and a sufficient amount of ultrapure water was added, followed by multiple washes until the wash solution became neutral. Next, the membrane was washed once with approximately 100 mL of 1 M NaCl aqueous solution, and then washed multiple times with sufficient amounts of ultrapure water to obtain an exchange group-introduced membrane. The membrane thickness in the wet state was 2.9 mm. After the reaction, the mixture was stored in a wet state. The N content measured by an elemental analyzer was 1.67% by weight.

[0083] <1-2> The microfiber laminate membrane of Example 5, measuring 5 cm in length, 5 cm in width, and 1.57 mm in thickness, was placed in a PP container with a lid. Next, 43.57 g of ultrapure water was added and allowed to blend throughout the membrane. Then, 56.12 g of a 0.5 mol / L aqueous sodium hydroxide solution was added, followed by 12.55 g of a 71.6 wt % aqueous glycigyltrimethylammonium chloride solution. The container was then capped and shaken for 16 hours in a 40°C thermostatic chamber. After completion, the liquid inside the container was removed, and a sufficient amount of ultrapure water was added thereto, followed by multiple washings until the washing solution became neutral. Next, the membrane was washed once with approximately 100 mL of 1 M NaCl aqueous solution, and then washed multiple times with sufficient amounts of ultrapure water to obtain an exchange-group-introduced membrane. The membrane thickness in the wet state was 2.4 mm. After the reaction, the membrane was stored in a wet state. The N content measured by an elemental analyzer was 1.57% by weight.

[0084] <1-3> The microfiber laminated membrane of Example 6, measuring 5 cm in length, 5 cm in width, and 1.50 mm in thickness, was placed in a PP container with a lid. Next, 43.50 g of ultrapure water was added and allowed to blend throughout the membrane. Then, 56.00 g of a 0.5 mol / L aqueous sodium hydroxide solution was added, followed by 12.52 g of a 71.6 wt% aqueous glycigyltrimethylammonium chloride solution. The container was then capped and shaken for 16 hours in a 40°C thermostatic chamber. After completion, the liquid inside the container was removed, and a sufficient amount of ultrapure water was added thereto, followed by multiple washings until the washing solution became neutral. Next, the membrane was washed once with approximately 100 mL of a 1 M NaCl aqueous solution, and then washed multiple times with sufficient amounts of ultrapure water to obtain an exchange-group-introduced membrane. The membrane thickness in the wet state was 2.8 mm. After the reaction, the membrane was stored in a wet state. The N content measured by an elemental analyzer was 1.65% by weight.

[0085] <2> Influenza virus evaluation The evaluation procedure was the same as in Example 2<2>.

[0086] <2-1> Purification of virus solution 1 The membrane prepared in Example 10 <1-1> was cut into a circle with a diameter of 2 cm and fixed to a membrane holder by pressing the edges of the membrane with a packing. The membrane holder was connected to the system, and 2 mL of equilibration buffer (buffer C) was passed through. Next, 16 mL of virus solution previously filtered through a 0.45 μm syringe filter was passed through. After passing 6 mL of equilibration buffer to wash, 8 mL of elution solution 1 (buffer C 70 vol%, D 30 vol%) was passed through, followed by 8 mL of elution solution 2 (buffer C 35 vol%, D 65 vol%) and finally 8 mL of elution solution 3 (buffer D) for elution. The results are shown in Figure 10 and Table 2. Despite the condition of a residence time of 0.2 minutes, 100% of the HA titer of the loaded virus was recovered in the fractions collected from elution solution 1.

[0087] <2-2> Purification of virus solution 2 The membrane prepared in Example 10 <1-2> was cut into a circle with a diameter of 2 cm and fixed to a membrane holder by pressing the edges of the membrane with a packing. The membrane holder was connected to the system, and 2 mL of equilibration buffer (buffer C) was passed through. Next, 16 mL of virus solution previously filtered through a 0.45 μm syringe filter was passed through. After passing 6 mL of equilibration buffer to wash, 8 mL of elution solution 1 (buffer C 70% by volume, D 30% by volume) was passed through, followed by 8 mL of elution solution 2 (buffer C 35% by volume, D 65% by volume), and finally 8 mL of elution solution 3 (buffer D) to elute. The results are shown in Figure 11 and Table 2. Despite the condition of a residence time of 0.2 minutes, 100% of the HA titer of the loaded virus was recovered in the fractions collected from elution solution 1.

[0088] <2-3> Purification of Virus Solution 3 The membrane prepared in Example 7 <1-3> was cut into a circle with a diameter of 2 cm and fixed to a membrane holder by pressing the edges of the membrane with a packing. The membrane holder was connected to the system, and 2 mL of equilibration buffer (buffer C) was passed through. Next, 16 mL of virus solution previously filtered through a 0.45 μm syringe filter was passed through. After passing 6 mL of equilibration buffer to wash, 8 mL of elution solution 1 (buffer C 70% by volume, D 30% by volume) was passed through, followed by 8 mL of elution solution 2 (buffer C 35% by volume, D 65% by volume), and finally 8 mL of elution solution 3 (buffer D) to elute. The results are shown in Figure 12 and Table 2. Despite the condition of a residence time of 0.2 minutes, 100% of the HA titer of the loaded virus was recovered in the fractions collected from elution solution 1.

[0089]

[0090] Comparative Example 1: Preparation of Nanofibers <1> Preparation of Nanofiber Spinning Solution Cellulose acetate with a relative molecular weight of 29,000 g / mol was used. A mixed solvent was prepared by mixing N,N-dimethylacetamide (a good solvent) and tetrahydrofuran (a good solvent) in a weight ratio of 3.75:6.25. 2.25 g of cellulose acetate was dissolved in 10 g of the mixed solvent at room temperature.

[0091] <2> Preparation of nanofibers The prepared spinning solution was supplied to a nozzle with an inner diameter of 0.22 mm at a rate of 0.5 mL / h using a syringe pump at a temperature of 26.5°C, a humidity of 32%, and a distance between the nozzle and collector of 20 cm. A voltage of 27.5 kV was applied to the nozzle, and the nanofibers were collected in a collector. The average fiber diameter was 460 nm (Figure 13).

[0092] Comparative Example 2 The spinning solution prepared in Comparative Example 1<1> was supplied to a nozzle with an inner diameter of 0.22 mm at 1.5 mL / h using a syringe pump under conditions of 26.5°C temperature, 32% humidity, and a nozzle-to-collector distance of 20 cm. A voltage of 27.5 kV was applied to the nozzle, and the solution was collected in a collector. In Comparative Example 2, the discharge rate was increased from 0.5 mL / h in Comparative Example 1 to 1.5 mL / h, resulting in an increase in fibers with an amorphous structure (Figure 14). Because the mixed solvent used to produce nanofibers is primarily composed of good solvents, increasing the discharge rate prevented sufficient solvent evaporation, resulting in an inhomogeneous fiber structure. This suggests that increasing the discharge rate is more difficult for nanofibers than for microfibers.

[0093] The chromatography carrier using the microfiber obtained by the present invention is extremely useful industrially because it can achieve high throughput and high processing speed in the separation and purification process of pharmaceuticals and the like, and can provide a purification process for large purification targets.

Claims

1. A chromatography support using a fibrous structure composed of microfibers made of at least one polymer component.

2. The chromatography carrier according to claim 1, wherein the microfibers have an average fiber diameter of 1 μm or more and less than 20 μm.

3. The chromatography carrier according to claim 1, wherein the microfibers have an average fiber diameter of 1 μm or more and less than 10 μm.

4. The chromatography carrier according to any one of claims 1 to 3, wherein the thickness of the fibrous structure is 100 µm or more and 2 mm or less.

5. A chromatography carrier according to any one of claims 1 to 5, wherein the fibrous structure is in the form of a laminated membrane.

6. The chromatography carrier according to claim 5, wherein the membrane has pores with a diameter of 0.5 μm or more and 30 μm or less.

7. The chromatography carrier according to any one of claims 1 to 6, wherein the microfibers comprise at least one selected from cellulose derivatives and polyamides.

8. A chromatography carrier according to any one of claims 1 to 6, wherein the microfibers comprise at least one selected from cellulose derivatives and polyamides, and at least one selected from polyethylene oxide and polyvinylpyrrolidone.

9. A chromatography carrier according to any one of claims 1 to 9, wherein a ligand is introduced into the microfiber.

10. The chromatography support according to claim 9, wherein the ligand is at least one selected from an ion exchange group and a functional polymer.

11. The chromatography support according to claim 10, wherein the ion exchange group and the functional polymer are at least one selected from the group consisting of quaternary ammonium, sulfonic acid, phosphoric acid, and polylysine.

12. The chromatography support according to claim 9, wherein the ligand is at least one selected from protein A, protein G, and an antibody.

13. A method for producing a microfiber, comprising: (a) a step of dissolving at least one polymer component in a mixed solvent of a solvent in which the polymer component is soluble and a solvent in which the polymer component is insoluble, to prepare a spinning solution containing the polymer component; and (b) a step of spinning the spinning solution by an electrospinning method to obtain a microfiber, wherein in step (b), the electrospinning method is carried out in an environment with a humidity of 30% or more and 60% or less.

14. A method for producing a fiber structure, comprising: (a) a step of dissolving at least one polymer component in a mixed solvent of a solvent in which the polymer component is soluble and a solvent in which the polymer component is insoluble to prepare a spinning solution containing the polymer component; (b) a step of spinning the spinning solution by electrospinning to obtain microfibers; and (c) a step of laminating the spun microfibers, wherein in step (b), the electrospinning is carried out in an environment with a humidity of 30% or more and 60% or less.

15. The method for producing microfibers according to claim 13 or the method for producing a fiber structure according to claim 14, wherein the microfibers have an average fiber diameter of 1 μm or more and less than 20 μm.

16. The method for producing microfibers according to claim 13 or the method for producing a fiber structure according to claim 14, wherein the microfibers have an average fiber diameter of 1 μm or more and less than 10 μm.

17. The method of any one of claims 13 to 16, wherein in step (a), the ratio of the solvent in which the polymer component is soluble to the solvent in which the polymer component is insoluble is adjusted to 85:15 to 20:80.

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