Cationized paramylon, nanofibers, and a dispersion of cationized paramylon

Abstract

To provide a cationized paramylon that can be dispersed not only in water but also in organic solvent, and to provide a nanofiber and a cationized paramylon fluid dispersion.SOLUTION: A cationized paramylon is a cationized paramylon that contains β-1,3-glucan having a structure in which the hydrogen atom of at least one hydroxy group of at least one glucose residue is substituted with a cationic functional group and in which the degree of substitution by cationic functional group is 0.80 or more for one glucose unit of β-1,3-glucan. The cationic functional group may be a 2-hydroxy-3-trimethylammoniopropyl group.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a cationized paramylon, nanofibers, and a dispersion of cationized paramylon.

Background Art

[0002] Nanofibers are fibrous substances with an average diameter of about 1 to 100 nm and a length of about 100 times or more the diameter. Depending on the raw material, they are classified into synthetic polymer-based nanofibers, natural polymer-based nanofibers, and carbon-based nanofibers. Natural polymer-based nanofibers are obtained using naturally occurring polysaccharides, which is advantageous in terms of the effective utilization of biomass and safety.

[0003] As natural polymer-based nanofibers, cellulose nanofibers mainly composed of cellulose, which is a type of β-1,4-glucan, are known. Cellulose nanofibers are hydrophilic by themselves and have the property of aggregating in water. Therefore, it is difficult to maintain the form of dispersed nanofibers in a hydrophobic environment such as a hydrophobic resin, and in most cases, they aggregate. Many attempts have been made to disperse them in a hydrophobic environment. Taking cellulose nanofibers as an example, for example, chemical modifications such as introducing long-chain alkyl groups or polycyclic functional groups on the nanofiber surface have been carried out. However, since these are heterogeneous reactions (reactions carried out in a state where the raw material solid is dispersed without being dissolved in the solvent), the introduction efficiency of functional groups is low, and the types of functional groups that can be introduced are also limited.

[0004] The present inventors have hitherto examined the usefulness as biomass by subjecting paramylon, a storage polysaccharide produced by Euglena, to various chemical modifications. Paramylon is a polysaccharide (β-1,3-glucan) formed by linking approximately 2,000 glucose molecules via β-1,3 bonds. Patent Document 1 proposes a paramylon derivative in which a hydrogen atom of a hydroxy group of a glucose residue of β-1,3-glucan is substituted with a cationic functional group as a paramylon derivative capable of constructing nanofibers that stably exist without aggregating in water.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The cationic functional group is known as a functional group for imparting water solubility to water-insoluble polysaccharides such as cellulose, as represented by the 2-hydroxy-3-trimethylammoniumpropyl group (HTA group), and the polysaccharide becomes water-soluble by adding only a very small amount of about 0.01 to 0.7 in terms of substitution degree.

[0007] An object of the present invention is to provide a cationized paramylon, nanofibers, and a dispersion of the cationized paramylon that can be dispersed not only in water but also in an organic solvent.

Means for Solving the Problems

[0008] The present inventors have surprisingly found that by introducing a cationic functional group such as an HTA group into paramylon with a large excess substitution degree of 0.80 or more, not only water solubility but also dispersibility in methanol or a multi-component organic solvent containing methanol can be obtained. a paramylon derivative having Further research has led to the finding that the thus obtained paramylon derivative can form a nanofiber aggregate in ethanol and can be dispersed and defibrated in water or an organic solvent containing methanol to obtain nanofibers, thus completing the present invention.

[0009] The present invention has the following aspects. [1] A cationized paramylon containing a β-1,3-glucan having a structure in which at least one hydrogen atom of at least one hydroxy group of at least one glucose residue is substituted with a cationic functional group, wherein the substitution degree of the cationic functional group is 0.80 or more per glucose unit of the β-1,3-glucan. [2] The β-1,3-glucan is represented by the following formula (I): TIFF0007701714000001.tif41170(In formula (I), n represents an integer of 60 to 3000, and R 1 represents a hydrogen atom or a cationic functional group, provided that at least one cationic functional group is included) The cationized paramylon according to [1], which has a structure represented by [3] The cationic functional group is represented by the following formula (II): TIFF0007701714000002.tif28170(In formula (II), R 2 independently represents a divalent chain hydrocarbon group having 1 to 3 carbon atoms having a hydroxy group at each occurrence, and R 3 independently represents an alkyl group having 1 to 3 carbon atoms at each occurrence, and R 4 independently represents an alkyl group having 1 to 3 carbon atoms at each occurrence, and R 5 independently represents an alkyl group having 1 to 3 carbon atoms at each occurrence) The cationized paramylon according to [1] or [2], which has a structure represented by [4] The cationized paramylon according to [1] or [2], wherein the cationic functional group is a 2-hydroxy-3-trimethylammoniopropyl group. [5] A nanofiber containing the cationized paramylon according to any one of [1] to [4]. [6] A dispersion liquid containing the cationized paramylon according to any one of [1] to [4] and a solvent. [7] The dispersion liquid according to [6], wherein the solvent contains methanol. [8] The dispersion liquid according to [6] or [7], wherein the solvent contains methanol and one or more selected from the group consisting of a halogen solvent, a protic solvent, and an aprotic solvent. [9] The dispersion liquid according to any one of [6] to [8], wherein the solvent contains water.

[10] An article containing the cationized paramylon according to any one of [1] to [4].

[11] The article according to

[10] , further containing a compound having a solubility of 1% by mass or more in a solvent containing water or methanol at 21°C.

[12] The article according to

[10] or

[11] , which is a film.

[13] A method for producing nanofibers, comprising: (i) reacting a raw material β-1,3-glucan with a compound having a cationic functional group to prepare a cationic functional group-containing β-1,3-glucan having a degree of substitution of the cationic functional group of 0.80 or more per glucose unit of β-1,3-glucan; and (ii) placing a reaction solution containing the cationic functional group-containing β-1,3-glucan in a poor solvent to obtain a nanofiber aggregate. A method comprising the above.

Advantages of the Invention

[0010] According to the present invention, it is possible to provide a cationized paramylon, a nanofiber, and a dispersion liquid of the cationized paramylon that can be dispersed not only in water but also in an organic solvent.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0012] Hereinafter, an embodiment of the present invention will be described in detail. The present invention is not limited to the following embodiments and can be implemented with appropriate modifications within the range that does not inhibit the effects of the present invention.

[0013] [Cationized paramylon] The cationized paramylon according to this embodiment contains a β-1,3-glucan having a structure in which a hydrogen atom of at least one hydroxy group of at least one glucose residue is substituted with a cationic functional group, and the substitution degree of the cationic functional group is 0.80 or more with respect to one glucose unit of the β-1,3-glucan.

[0014] Since the cationized paramylon according to this embodiment contains a β-1,3-glucan having a structure in which a hydrogen atom of a hydroxy group of a glucose residue is substituted with a cationic functional group, it can be made into a cationized paramylon that can be dispersed in water. Since the substitution degree of the cationic functional group is 0.80 or more with respect to one glucose unit of the β-1,3-glucan, it can be dispersed not only in water but also in methanol or a multi-component organic solvent containing methanol. "Disperse" means that no precipitate is formed when the cationized paramylon is put in a solvent in an amount of 1% by mass and stirred. Since this cationized paramylon can be dispersed (hydrophilic and hydrophobic) in both water and an organic solvent containing methanol, it can be utilized as a filler for resins or the like by taking advantage of its hydrophobicity, or a film can be produced by the solvent casting method. Also, by taking advantage of its hydrophilicity and hydrophobicity, a sustained-release film as described later can be produced and utilized. In addition, since the β-1,3-glucan having a cationic functional group is easy to synthesize as described later, a complicated preparation process such as the synthesis of hydrophobic group-introduced cellulose nanofibers is unnecessary, which is also advantageous from the viewpoints of cost and reduction of environmental load.

[0015] (β-1,3-glucan) Cationized paramylon contains β-1,3-glucan. "β-1,3-glucan" means a polysaccharide having a structure in which glucose is linked by β-1,3 bonds. That is, β-1,3-glucan has a structure in which the 1-position of glucose and the 3-position of another glucose form a β-1,3-glucoside bond. The term "β-1,3-glucan" includes β-1,3-glucan and its derivatives. β-1,3-glucan is mainly produced by algae, fungi, etc.

[0016] Due to the structure in which glucose is linked by β-1,3 bonds, three molecules associate in water to construct a triple helix structure in β-1,3-glucan. Thereby, nanofibers having a triple helix structure are obtained. Since β-1,3-glucan can spontaneously form nanofibers in water, nanofibers can be produced by a bottom-up method from raw materials. Therefore, it is also advantageous in that it can be produced by a method with less energy consumption than nanofibers produced by a top-down method in which natural materials such as pulp are pulverized to the nano unit by a mechanical method like cellulose nanofibers.

[0017] Nanofibers that have constructed a triple helix structure in water, like natural paramylon, usually exist as an aggregate in which a plurality of them are aggregated, and it is considered difficult to eliminate and disperse the aggregated state. However, since the cationized paramylon according to this embodiment has a cationic functional group, it can be easily dispersed in water due to the electrostatic repulsion between the fibers.

[0018] β-1,3-glucan preferably has the structure represented by the following formula (I): TIFF0007701714000003.tif41170.

[0019] In formula (I), n represents an integer of 60 to 3000, and R 1represents a hydrogen atom or a cationic functional group. However, at least one cationic functional group is included. n is preferably from 500 to 2800, more preferably from 700 to 2500, even more preferably from 800 to 2200, and most preferably from 1000 to 2000. Note that paramylon synthesized and accumulated by Euglena is usually a β-1,3-glucan in which 1500 to 2000 glucose molecules are β-1,3-bonded.

[0020] (Cationic functional group) The β-1,3-glucan has a structure in which a hydrogen atom of at least one hydroxy group of at least one glucose residue is substituted with a cationic functional group. The "cationic functional group" means a functional group that forms a cation or can easily form a cation near neutrality (about pH 6 to 8).

[0021] The cationic functional group is represented by the following formula (II): It preferably has a structure represented by TIFF0007701714000004.tif28170.

[0022] In formula (II), R 2 independently represents a divalent chain hydrocarbon group having 1 to 3 carbon atoms with a hydroxy group at each occurrence, and R 3 independently represents an alkyl group having 1 to 3 carbon atoms at each occurrence, and R 4 independently represents an alkyl group having 1 to 3 carbon atoms at each occurrence, and R 5 independently represents an alkyl group having 1 to 3 carbon atoms at each occurrence.

[0023] R 2The divalent chain hydrocarbon group represented by is not particularly limited as long as it is a divalent chain hydrocarbon group in which at least one hydrogen atom is substituted with a hydroxy group, and includes both linear and branched (preferably linear) ones. The number of carbon atoms of the divalent chain hydrocarbon group is preferably 1 to 3, more preferably 3. The divalent chain hydrocarbon group includes both saturated hydrocarbon groups and unsaturated hydrocarbon groups, but is preferably a saturated hydrocarbon group. The number of hydroxy groups in the divalent chain hydrocarbon group is, for example, 1 to 3, preferably 1 to 2, more preferably 1. Specific examples of the divalent chain hydrocarbon group include groups in which a hydroxy group is substituted on a methylene group, an ethylene group, a normal propylene group, an isopropylene group, etc.

[0024] R 3 、R 4 、or R 5 The alkyl group represented by is not particularly limited and includes both linear and branched (preferably linear) ones. The number of carbon atoms of the alkyl group is preferably 1 to 3, more preferably 1. Specific examples of the alkyl group include a methyl group, an ethyl group, a normal propyl group, an isopropyl group, etc.

[0025] As the cationic functional group, a trialkylammoniohydroxyalkyl group is preferred. As the trialkylammoniohydroxyalkyl group, a 2-hydroxy-3-trimethylammoniopropyl group is preferred.

[0026] The substitution degree of the cationic functional group is 0.80 or more per glucose unit of β-1,3-glucan, and from the viewpoint of being more easily dispersed (defibrated) in an organic solvent, it is preferably 1.00 or more, more preferably 1.02 or more, still more preferably 1.04 or more, even more preferably 1.10 or more, and particularly preferably 1.20 or more. The upper limit of the substitution degree of the cationic functional group is 3.00. From the perspective of being more easily dispersed (defibrated) in an organic solvent, it is preferable that the substitution degree is larger within the range where the cationic functional group can be introduced. From the perspective of incorporating other substances into an article containing cationized paramylon and releasing the substance more slowly in water (sustained release), the substitution degree of the cationic functional group is preferably 1.50 or less, more preferably 1.30 or less. On the other hand, from the perspective of releasing small molecules more quickly in water, it is preferable that the substitution degree of the cationic functional group is larger. Conventionally, HTAP with a substitution degree (DS hta ) of 0.07 to 0.16 can form nanofibers with a diameter of 100 nm or less in water, but it has been reported that HTAP with DS hta of 0.31 and 0.64 hardly forms nanofibers. However, surprisingly, it has been found that when the substitution degree of the cationic functional group reaches an excessive amount of 0.80 or more, single-chain polymers can self-assemble to form nanofibers in water and ethanol. Furthermore, these nanofibers can be dispersed in water and also in organic solvents containing methanol. Such findings have not been known so far.

[0027] The "substitution degree" is the number of cationic functional groups per glucose unit of β-1,3-glucan, and 1 it is defined as the value determined from the ratio of the integral value derived from the methyl group of the cationic functional group to the total integral value of the hydrogen atoms derived from glucose in 1H-NMR.

[0028] The weight-average molecular weight of β-1,3-glucan is not particularly limited, and it is preferably 1.0×10 4 to 5.0×10 6 , more preferably 1.0×10 5 to 1.0×10 6 , even more preferably 1.0×10 5 to 8.0×10 5 , most preferably 1.0×10 5 to 5.0×10 5 , and particularly preferably 4.1×10 5 to 4.6×105 It is. The weight average molecular weight can be determined by an absolute molecular weight measurement method using SEC-MALS (Size Exclusion Chromatography - Multi Angle Light Scattering).

[0029] [Nanofiber] The nanofiber according to this embodiment contains the above-mentioned cationized paramylon. The above-mentioned cationized paramylon spontaneously forms nanofibers by putting the cationization reaction solution into water or a poor solvent such as ethanol. Details of the production method will be described later. Since the nanofiber according to this embodiment can be dispersed in water or an organic solvent containing methanol, a film can be easily produced by a solvent casting method using water or a solvent containing methanol.

[0030] Since the nanofiber according to this embodiment can be dispersed in water or an organic solvent containing methanol, it can be made into an aqueous dispersion of nanofibers, and can also be made into an organic solvent dispersion of nanofibers. Furthermore, it can also be made into a dispersion containing nanofibers and a solvent containing water and an organic solvent.

[0031] (Use) Since the above-mentioned cationized paramylon and nanofiber can be dispersed in methanol or a multi-component organic solvent containing methanol, they can be used, for example, as a filler for a hydrophobic resin. Also, since the dispersibility in methanol is excellent, the production of a film by the solvent casting method is easy, and the obtained film is excellent in smoothness. The film using this cationized paramylon or nanofiber is characterized by having reversible hygroscopicity / dehumidification as shown in the examples described later, and accordingly, the appearance of the film changes from opaque to transparent.

[0032] [Dispersion] The dispersion according to this embodiment contains the above-described cationized paramylon and a solvent. In one embodiment, the dispersion contains nanofibers formed from the above-described cationized paramylon and a solvent. The "dispersion" means a liquid in which cationized paramylon (or nanofibers) is dispersed in a solvent. Details of the cationized paramylon and nanofibers are as described above, so the description is omitted here. The content of the cationized paramylon is preferably 1 to 40 mg / mL, more preferably 10 to 40 mg / mL, and even more preferably 30 to 40 mg / mL in the dispersion.

[0033] (Solvent) Since the above-described cationized paramylon can be dispersed in water or an organic solvent containing methanol, the solvent preferably contains water and / or methanol. As the water, secondary distilled water, tertiary distilled deionized water, or ultrapure water can also be used.

[0034] When the solvent contains methanol, it can further contain one or more selected from the group consisting of a halogen solvent, a protic solvent, and an aprotic solvent. By further containing one or more selected from the group consisting of a halogen solvent, a protic solvent, and an aprotic solvent, a dispersion of a multi-component organic solvent containing methanol can be obtained, the variation of the organic solvent to be used is widened, and it can be applied to various uses such as a filler for a resin.

[0035] Examples of the halogen solvent include chloroform, dichloromethane, 1,2-dichloroethane, and the like. Examples of the protic solvent include alcohols such as ethanol. Examples of the aprotic polar solvent include acetone, N,N-dimethylacetamide, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethyl acetate, acetonitrile, tetrahydrofuran, N,N-dimethylacetamide, pyridine, and the like. Ionic liquids such as 1-allyl-3-methylimidazolium chloride can also be used.

[0036] In one embodiment, the solvent includes methanol and at least one selected from the group consisting of chloroform, dichloromethane, 1,2-dichloroethane, acetone, N,N-dimethylacetamide, N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO).

[0037] The mixing ratio of methanol and other organic solvents in the organic solvent, as the value of the methanol / other organic solvent ratio, is preferably 1 / 10 to 10 / 1, more preferably 1 / 2 to 2 / 1.

[0038] The dispersion can also include water and an organic solvent containing methanol. In this case, the mixing ratio of water and the organic solvent containing methanol, as the value of the water / organic solvent containing methanol ratio, is preferably 1 / 10 to 10 / 1, more preferably 1 / 2 to 2 / 1.

[0039] The dispersion is a dispersion containing 1% by mass of cationized paramylon in methanol. Using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, "UV-2500"), the dispersion is put into a quartz cell with an optical path length of 10 mm and measured at room temperature (21°C). The transmittance at wavelengths of 400 to 800 nm in the visible absorption spectrum is preferably 3% or more, more preferably 10% or more, even more preferably exceeding 50%, still more preferably 80% or more, and particularly preferably 90% or more or 95% or more. When the transmittance at wavelengths of 400 to 800 nm in the visible absorption spectrum exceeds 50%, it can be a dispersion with less turbidity and excellent dispersibility.

[0040] The dispersion can be produced by dispersing cationized paramylon in a solvent by a known method. For example, solid or gel-like cationized paramylon is placed in a solvent and stirred at 10 to 60 °C, preferably 20 to 30 °C, for 1 to 72 hours, preferably 10 to 24 hours, using a magnetic stirrer or the like as necessary to obtain a dispersion.

[0041] [Article] The article according to this embodiment contains the above-described cationized paramylon. Since the above-described cationized paramylon can be dispersed in an organic solvent, it can be used, for example, as a filler for a hydrophobic resin.

[0042] In one embodiment, the article is a filler. In one embodiment, the article is a fibrous filler. The average particle size of the filler is not limited. The average fiber length in the case of being fibrous is also not limited and can be, for example, 1 to 50 mm.

[0043] Since the above-described cationized paramylon has excellent dispersibility in water and in a solvent containing methanol, it is easy to produce a film by the solvent casting method, and the obtained film has excellent smoothness.

[0044] In one embodiment, the article is a film. The thickness of the film is not limited. The thickness can be, for example, 50 to 400 μm, 100 to 300 μm. The article containing the above-described cationized paramylon is characterized by having reversible hygroscopicity / dehygroscopicity as shown in the examples described later, and accordingly, the appearance of the article changes from opaque to transparent. Therefore, for example, the article can be preferably used as a base material for a wound treatment material in which the state of wounds can be easily visually recognized.

[0045] The method for producing a film by the solvent casting method is not limited and can be a known method. For example, a film can be obtained by adding about 1 to 40 mg / mL of cationized paramylon to a solvent containing methanol, stirring at 10 to 60°C for 1 to 72 hours, and then removing the solvent. Methanol evaporates easily at room temperature, so a film can be produced more easily. Water can also be used instead of a solvent containing methanol.

[0046] In one embodiment, the article may be a powder obtained by pulverizing a film. In one embodiment, the article may be a powder obtained by pulverizing an amorphous lump solid.

[0047] In one embodiment, the article further includes a compound (hereinafter referred to as "compound (A)") having a solubility of 1% by mass or more in a solvent containing water or methanol at 21°C. Compound (A) having a solubility of 1% by mass or more in a solvent containing water or methanol at 21°C is easily soluble in a solvent containing water or methanol. Therefore, when forming a film by a solvent casting method, compound (A) is dissolved in a solvent containing water or methanol, so that compound (A) is incorporated into the film, and a film containing compound (A) can be easily produced.

[0048] Since the above-mentioned cationized paramylon is dispersible in both water and organic solvents, for example, when forming a film by the above-mentioned solvent casting method, it is possible to incorporate compound (A) soluble in water or a solvent containing methanol into the film by making it coexistent. Since this film has dispersibility in water and a solvent containing methanol, the film disintegrates when immersed in water or a solvent containing methanol, and the incorporated compound (A) is gradually released into the water.

[0049] For example, when forming a film by a solvent casting method using a solvent containing methanol, a compound (A) that is insoluble in water but soluble in a solvent containing methanol is allowed to coexist with cationized paramylon in the solvent, whereby a cationized paramylon film containing the compound can be obtained. When the obtained film is immersed in water, the film disintegrates and the incorporated compound is gradually released into the water. Thereby, the compound (A) that is insoluble in water but soluble in methanol can be sustainedly released (gradually released over time) into water.

[0050] Therefore, an article containing cationized paramylon can also be used as a base for a sustained-release preparation. In one embodiment, the article is a base for a sustained-release preparation. In one embodiment, the article is a base for a wet wound dressing.

[0051] Even when the compound (A) is insoluble in an organic solvent and soluble only in water, since cationized paramylon is water-soluble, a film can also be produced using water as a solvent.

[0052] Also, not limited to films, bulk solids and powders obtained by pulverizing films or bulk solids also exhibit sustained release of the compound (A) in water or a solvent containing methanol.

[0053] The compound (A) is not limited, and examples include dyes, antibacterial agents, etc. Examples of dyes include phenolphthalein, Nile blue, etc. Examples of antibacterial agents include tetracycline, etc.

[0054] [Method for producing nanofibers] The method for producing nanofibers according to this embodiment is (i) reacting a raw material β-1,3-glucan with a compound having a cationic functional group to prepare a cationic functional group-containing β-1,3-glucan in which the substitution degree of the cationic functional group is 0.80 or more per glucose unit of β-1,3-glucan, and (ii) placing a reaction solution containing a cationic functional group-containing β-1,3-glucan into a poor solvent to obtain a nanofiber aggregate,

[0055] (Step (i)) From the viewpoint of reducing environmental impact, the raw material β-1,3-glucan is preferably of biological origin, more preferably of plant origin. Among them, it is preferable to use β-1,3-glucan separated from microalgae that synthesize β-1,3-glucan intracellularly as a raw material. As the microalgae, Euglena (microalgae belonging to the phylum Euglenophyta) is preferable. This is because Euglena is easy to culture, has a short growth cycle, and accumulates a large amount of paramylon particles as photosynthetic products intracellularly. Paramylon synthesized and accumulated by Euglena is a β-1,3-glucan formed by β-1,3-linkage of usually 2000 glucose molecules. Separation of β-1,3-glucan such as paramylon from microalgae can be carried out by conventional methods.

[0056] In one embodiment, as the compound having a cationic functional group, the following formula (III): The compound represented by TIFF0007701714000005.tif28170 can be used. In formula (III), R 2 , R 3 , R 4 , and R 5 are the same as R 2 , R 3 , R 4 , and R 5 in the above formula (II), respectively. A cationic functional group-containing β-1,3-glucan can be obtained by subjecting the hydroxy group of the compound represented by formula (III) and the hydroxy group of the raw material β-1,3-glucan to a condensation reaction. The counter anion is not limited, and examples include anions containing a halogen atom.

[0057] In one embodiment, as the compound having a cationic functional group, the following formula (IV): Compounds represented by TIFF0007701714000006.tif27170 can also be used. In formula (IV), R 2 , R 3 , R 4 , and R 5 are the same as R 2 , R 3 , R 4 , and R 5 in the above formula (II), respectively. The counter anion is not limited, and examples include anions containing a halogen atom.

[0058] In one embodiment, as the compound having a cationic functional group, the following formula (IV'): Compounds represented by TIFF0007701714000007.tif25170 are used.

[0059] By reacting the compound represented by formula (IV) or formula (IV') with the raw material β-1,3-glucan in an aqueous solvent (alkaline aqueous solution) in the presence of a base such as sodium hydroxide, a cationic functional group-containing β-1,3-glucan can be obtained. From the viewpoint of improving the degree of substitution, the amount of the compound represented by formula (IV) or formula (IV') (or a salt thereof) used is preferably 20 to 30 parts by mass, preferably 25 to 30 parts by mass, based on 1 part by mass of β-1,3-glucan. The reaction atmosphere is not particularly limited, but is usually a nitrogen atmosphere. The reaction temperature can be carried out either under heating or at room temperature, and is usually preferably carried out at 20 to 70 °C (especially 55 to 70 °C). The reaction time is not particularly limited and can usually be 1 hour to 10 hours, preferably 2 hours to 6 hours.

[0060] After completion of the reaction, usually, purification treatment is carried out according to a conventional method as necessary. The structure of the product can be determined by elemental analysis, FT-IR, 1 H-NMR, 13 C-NMR, etc.

[0061] (Step (ii)) In step (ii), a reaction solution of a β-1,3-glucan containing a cationic functional group (for example, an alkaline aqueous solution) is placed in a poor solvent to obtain a nanofiber aggregate. Examples of the poor solvent include water and / or ethanol. Due to the structure in which glucose is linked by β-1,3 bonds, three molecules of β-1,3-glucan associate with each other in water to spontaneously form nanofibers. Nanofibers can also be formed in the same way for a β-1,3-glucan containing a cationic functional group. That is, when the reaction solution containing the single-stranded cationized paramylon obtained in the above step (i) is poured into an excessive amount of water or ethanol, which is a poor solvent, nanofibers are formed and precipitate as a nanofiber aggregate. The formation of the nanofiber aggregate is carried out by pouring the reaction solution containing the β-1,3-glucan containing a cationic functional group into an excessive amount of ethanol (or water). The nanofiber preparation conditions can be 20 to 30 °C. Usually, when the reaction solution is poured into ethanol, a gel-like white precipitate immediately appears. It may be immersed with stirring as needed. Then, the nanofibers can be aggregated by centrifugation, decantation, etc. to recover from ethanol to obtain a gel-like nanofiber aggregate. By pouring the obtained aggregate into methanol and stirring, a methanol solution containing dispersed nanofibers can be obtained. The nanofiber aggregate can also be dried to form a solid. To prepare a methanol solution of nanofibers from the dried solid, the dried solid can be dissolved in an alkaline aqueous solution, neutralized with an acid, and then the gel-like nanofiber aggregate obtained by pouring the resulting aqueous solution into ethanol can be poured into methanol and stirred.

[0062] The method for producing the hydrophobic nanofibers according to this embodiment may optionally include a step of washing and / or drying the obtained nanofiber aggregate. Washing and / or drying can be carried out by known methods. For example, washing can be carried out by stirring in a lower alcohol such as methanol or ethanol, or a solvent such as acetone, at 20 to 40 °C for 5 to 30 minutes. After washing, the solvent is removed by a known method. Drying can be carried out, for example, by air-drying at 50 to 80 °C for 1 to 24 hours, and / or by heat-drying at 30 to 60 °C for 1 to 6 hours under vacuum, etc.

[0063] (Step (iii)) The method for producing nanofibers according to this embodiment further includes (iii) putting the nanofiber aggregate into an organic solvent containing water and / or methanol and stirring it. By putting the nanofiber aggregate into an organic solvent containing water and / or methanol and stirring it, the nanofiber aggregate is loosened and dispersed, and a dispersion of nanofibers can be obtained. The nanofiber aggregate obtained in step (ii) is dried for the purpose of long-term storage, etc., and can be stored as the "essence of nanofibers". If the nanofiber aggregate is in a wet state without being dried, when it is directly put into an organic solvent containing methanol and stirred for a while, the nanofibers are dispersed in methanol to form a transparent dispersion solution. The same is true when it is put into water. When the nanofiber aggregate is once dried, to prepare a nanofiber dispersion from this, (1) dissolve it in an alkaline aqueous solution, then (2) neutralize it with an acid, and (3) put the obtained transparent aqueous solution into ethanol, which is a poor solvent, so that (4) the nanofiber aggregate precipitates as a solid. This wet solid is put into methanol and stirred for a while to form a transparent homogeneous solution (dispersion) containing nanofibers.

Examples

[0064] Examples are shown below to explain the present invention more specifically, but the interpretation of the present invention is not limited by these examples.

[0065] Hereinafter, using Euglena polysaccharide (paramylon) and glycidyltrimethylammonium chloride, 2-hydroxy-3-trimethylammonio-propyl paramylon (HTAP) with different degrees of substitution (DS hta ) was prepared. The synthesis scheme is as follows: TIFF0007701714000008.tif41170

[0066] [Example 1] Synthesis of HTAP-1 (DS hta : 0.85, DP: 1691) Glycidyltrimethylammonio chloride (GTAC) (aqueous solution of about 80% by weight, 117.54 g, 620.14 mmol) was added dropwise to a homogeneous solution consisting of paramylon (5.003 g, 30.85 mmol) and 1.0 N aqueous NaOH solution (250 mL) at 23 °C. After stirring this mixed solution at 56 °C for 3 hours, it was allowed to cool to room temperature. After adjusting the obtained solution to pH 3 with concentrated hydrochloric acid, it was poured into ethanol (1.5 L) to obtain a white precipitate. The white precipitate was separated by decantation, dispersed in ethanol (200 mL), and washed by stirring (twice overnight). After air drying (overnight) and then vacuum heating drying (60 °C, 7 hours), HTAP-1 was obtained (7.455 g, 25.50 mmol, yield 82.7%). That it is the target compound was 1 confirmed by 1H NMR and FT-IR. The degree of substitution (DS hta ) was determined by comparing the integral value of the protons derived from glucose with the integral value of the methyl groups of the HTA group. 1 1H NMR (D2O) δ4.45(brs), 3.92?3.48(m), 3.20(m); FT-IR (cm -1 ) 3301, 2883, 1637, 1476, 1057, 912; DS hta = 0.85

[0067] [Example 2] Synthesis of HTAP-2 (DS hta : 1.04, DP: 1531) HTAP-2 was obtained from paramylon (5.011 g, 30.91 mmol) in a 74.6% yield (7.401 g, 23.07 mmol) in the same manner as in Example 1, except for the amount of GTAC used (80 wt%, 146.10 g, 770.82 mmol). 1 H NMR (D2O) δ4.45(brs),3.92?3.48(m),3.24(m); FT-IR (cm -1 ) 3301,2884,1635,1476,1038,911; DS hta =1.04

[0068] [Example 3] Synthesis of HTAP-3 (DS hta :1.22, DP:1296) HTAP-2 was obtained from paramylon (5.005 g, 30.87 mmol) in a 92.5% yield (9.953 g, 28.55 mmol) in the same manner as in Example 1, except for the amount of GTAC used (80 wt%, 174.73 g, 921.88 mmol). 1 H NMR (D2O) δ4.46 (brs),3.92?3.50(m),3.24(m); FT-IR (cm -1 ) 3328,2880,1641,1478,1059,911; DS hta =1.22

[0069] (Measurement of degree of substitution, etc.) The degree of substitution (DS hta ) of HTAP-1 to HTAP-3 was determined by measuring the 1 H-NMR of the compound. Specifically, it was determined from the ratio of the integral value derived from the 2-hydroxy-3-trimethylammonio-propyl group to the total integral value of the hydrogen atoms derived from glucose. The degree of polymerization (DP) was determined by the following formula. DP = weight average molecular weight (M w ) / (160.1 + 129.2 × DS hta + 1.0 × (3 - DS hta )) The weight-average molecular weight (M w ) was determined by an absolute molecular weight measurement method using SEC-MALS (Size Exclusion Chromatography - Multi Angle Light Scattering).

Table 1

[0070] (Confirmation of nanofibers by scanning electron microscope (SEM)) Each of the obtained HTAPs was placed in a cellulose dialysis membrane ((18 / 32″), MWCO 12,000 - 14,000) manufactured by Viskase Companies Inc. and dialyzed against water for 3 days, and then the lyophilized HTAP solid (about 10 mg) was placed in a flask containing Milli-Q water (about 10 mL). This solution was mechanically stirred for 20 hours, rapidly frozen using liquid nitrogen, and then dried under reduced pressure to obtain a cotton-like solid. This solid was fixed to the metal stage of the microscope using carbon conductive double-sided tape. Under high vacuum, SEM observation was performed using a scanning electron microscope (JSM-6060, JEOL) at an acceleration voltage of 2.5 kV. SEM photographs of HTAP-1, HTAP-2, and HTAP-3 are shown in FIGS. 1(a) to (c), respectively. As shown in FIGS. 1(a) to (c), it was confirmed that the lyophilized products prepared from each aqueous solution contained nanofibers with a diameter of about 200 nm. Therefore, HTAP forms nanofibers in an aqueous solution.

[0071] [Preparation of methanol dispersion] A sample of HTAP-1 solid (about 700 mg) was dispersed in 1.0 N aqueous NaOH solution (25 mL) and mechanically stirred at room temperature for 2 hours. Concentrated aqueous HCl solution was added to the resulting homogeneous solution to acidify it to pH 3. This mixture was poured into ethanol (150 mL) to precipitate a white solid, which was decanted and separated from the solution, and mechanically stirred for 2 hours and washed with ethanol (150 mL). Subsequently, the solid was dispersed in methanol (60 mL) and mechanically stirred overnight to obtain a turbid solution (11.7 mg / mL: 1 wt%). The same procedure was carried out for HTAP-2 to obtain a slightly turbid dispersion (23.6 mg / ml). The same procedure was carried out for HTAP-3 solid to obtain a transparent dispersion (31.2 mg / ml). No precipitate was observed (dispersed) in any of the dispersions.

[0072] (Measurement of transmittance) To quantitatively evaluate the dispersion state of the nanofibers in each of the dispersions obtained above, for the dispersions of the same concentration (11.7 mg / mL: 1 wt%), the transmittance at wavelengths of 400 to 800 nm in the visible absorption spectrum was measured using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, "UV-2500"). The transmittance of the methanol dispersion of HTAP-1 (DS hta : 0.85) was about 4%. The transmittance of HTAP-2 (DS hta : 1.04) exceeded 88%, and the transmittance of HTAP-3 (DS hta : 1.22) exceeded 93%. HTAP-2 and HTAP-3 can achieve a transmittance of 80% or more for the dispersion, and have better dispersibility in methanol. From these results, it was clarified that (i) higher DS hta results in higher methanol dispersibility, and (ii) if DS hta is 0.80 or more, it can be dispersed in methanol. The reason for the high dispersibility of HTAP-3 nanofibers in methanol is considered to be that (i) numerous hydroxyl groups derived from paramylon and HTA groups contribute to the formation of nanofibers in aqueous solution through intermolecular hydrogen bonding, and (ii) numerous hydrophobic methyl groups derived from HTA groups exposed on the surface of the obtained nanofibers contribute to the affinity for non-aqueous solvents.

[0073] (Confirmation of Nanofibers by Scanning Probe Microscope (SPM)) To examine the structure of HTAP dispersed in methanol, 5 μL of a 1 / 1000 diluted solution (about 12 - 31 μg / mL) of the above methanol dispersion was placed on freshly cleaved mica, and the solvent was removed by air flow at ambient temperature to obtain a solid sample. This was analyzed using a scanning probe microscope (SPI4000, manufactured by Seiko Instruments Inc.; tapping mode, scanning speed 1.0 Hz). SPM observations were performed in air using a 20 μm scanner (SPA-400, manufactured by Seiko Instruments) and a cantilever DF-20 (length 225 μm; spring constant 12 N / m; frequency 124 kHz) manufactured by Seiko Instruments. SPM photographs of HTAP-1, HTAP-2, and HTAP-3 are shown in Figs. 2(a) - (c), respectively.

[0074] As shown in Fig. 2(a), HTAP-1 (DS hta : 0.85) showed a structure in which nanofibers seemed to be aggregated. As shown in Fig. 2(b), HTAP-2 (DS hta : 1.04) showed nanofibers in the process of fibrillation with a diameter of about 250 nm. As shown in Fig. 2(c), HTAP-3 (DS hta : 1.22) confirmed nanofibers with a diameter of about 30 nm.

[0075] From these observation results, it was confirmed that (1) all HTAPs construct nanofibers in methanol, and (2) the higher the degree of substitution, the easier the nanofibers are dispersed and fibrillated.

[0076] (Confirmation of nanofibers by transmission electron microscope (TEM)) The methanol dispersion of HTAP-3 (31.2 μg / mL) was diluted 1 / 1000, and 2 μL was placed on a hydrophilized TEM grid for observation. After 2 minutes, 2 μL of a 0.3% aqueous solution of 12-phosphotungstic acid was placed on it. After 30 seconds, the excess solution was removed with filter paper. For this sample, TEM observation was carried out at an acceleration voltage of 100 kV using a transmission electron microscope (1010T, manufactured by JEOL Ltd.). Figure 3 shows the TEM photograph of HTAP-3. When the average diameter of the nanofibers was calculated by measuring 50 different places, it was 32.6 ± 3.7 nm.

[0077] [Preparation of binary organic solvent dispersion] 0.5 mL of the methanol dispersion (31.2 mg / mL) of HTAP-3 (DS hta : 1.22) used also in the sample preparation of SPM and 0.5 mL of a mixed solvent selected from chloroform, 1,2-dichloroethane, dichloromethane, acetone, DMSO, DMF, and DMAc were stirred at room temperature (21 °C) for about 1 minute. Since no precipitation was observed, it was considered that the HTAP nanofibers maintained a dispersed state in these mixed solvents.

[0078] (Measurement of transmittance) To quantitatively confirm the dispersed state of the nanofibers in the above mixed solvents, these mixed solvents were transferred to a cuvette (path length 10 mm), and the transmittance at wavelengths of 400 to 800 nm in the visible absorption spectrum was measured using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, "UV-2500"). The results are shown in Figure 3. Since the transmittance was almost 100% in all cases, the dispersion of the nanofibers in these binary organic solvents was confirmed.

[0079] [Preparation of HTAP cast film] HTAP-1 (DS hta: 0.85) methanol dispersion (60 mL, 11.7 mg / mL) was placed in a PTFE dish with a width of 75 × a depth of 100 × a height of 20 mm. After removing methanol overnight at room temperature, an opaque HTAP-1 film (approx. 75 × 100 × 0.1 mm) was prepared. Similarly, from the methanol dispersion of HTAP-2 (DS hta : 1.04) (23.6 mg / ml) and the methanol dispersion of HTAP-3 (DS hta : 1.22) (31.2 mg / ml), opaque HTAP-2 and HTAP-3 films were obtained respectively.

[0080] (Measurement of Film Transmittance) The methanol cast films of HTAP-1 to HTAP-3 obtained above were opaque in a low humidity environment but became transparent in a high humidity environment. Furthermore, they became opaque again when the environment became low humidity. These results suggest that the HTAP film has reversible hygroscopicity.

[0081] To quantitatively investigate the dependence of its transparency and hygroscopicity on environmental humidity, as follows, the light transmittance and weight of the HTAP film were measured after being continuously placed (incubated) for 24 hours at 21°C in environments of humidity (~14%), high humidity (~96%), and low humidity (~14%). These two humidities correspond to the use environments of wet wound dressings where the HTAP film may be applicable.

[0082] The methanol cast film (approx. 10×20×0.2 mm) obtained from HTAP was left in an automatic dry desiccator (OH-3S, manufactured by AS ONE Corporation) controlled at 21.0 ± 1.0 °C and 14.0 ± 0.5% humidity for approximately 24 hours. The light transmittance spectrum in the visible light range (400 - 800 nm) of the left film was measured with a spectrophotometer (UV-2500, Shimadzu Corporation), and the weight of the film was measured with an electronic balance. Subsequently, the film was placed in a desiccator (LH, manufactured by AS ONE Corporation) together with an Erlenmeyer flask containing 500 mL of water and left at 21.0 ± 1.0 °C and 96 ± 0.5% humidity. After approximately 24 hours, the light transmittance and weight of the film were measured. The film was transferred back to the dry desiccator (21.0 ± 1.0 °C; 14.0 ± 0.5% humidity). After leaving it for 24 hours, the light transmittance and weight of the film were measured. The film thickness was measured 10 times each using a high-precision digital micrometer MDH-25M (manufactured by Mitutoyo Corporation). The results are shown in Table 2.

[0083]

Table 2

[0084] The opaque and distorted film left in the low humidity environment became transparent and smooth after high humidity incubation. The transmittance increased with the increase in humidity (Table 2). The weight of the film was approximately 1.6 - 2.0 times the initial weight, which is considered to be due to the absorbed water molecules. The film weight returned to the initial value after the second incubation in the low humidity environment. In the naked eye observation, the transparency was maintained high during high humidity incubation. The absorption / desorption profile of the HTAP film may include the possibility of being used as a base material for a wet wound dressing, absorbing moisture in contact with wound exudate, and promoting wound healing by maintaining the wet state of the wound. Furthermore, the transparency of the film in the wet state is considered useful for the examination of the affected area.

[0085] [Evaluation of the sustained release property of the film] When HTAP forms nanofibers or nanofiber-like aggregates (Figure 2) and considering the change from a methanol dispersion to a cast film, it is possible that the film can accommodate substances other than water inside the gaps of the nanofiber network. If so, when HTAP is immersed in an aqueous solution, small molecules are gradually released into the aqueous environment. Considering this, the sustained-release ability of the HTAP film was investigated using phenolphthalein, a pH indicator, as a model of small molecules (Compound (A)).

[0086] A methanol solution of phenolphthalein (10.0 mg / mL, 2.0 mL) was added to a methanol solution containing about 700 mg of HTAP-1 to HTAP-3 each. After mechanical stirring for about 1 hour, the mixture was placed in a PTFE dish (100×25×10 mm) and left at room temperature overnight to prepare a methanol cast film containing phenolphthalein as a model of Compound (A). The obtained film pieces (about 20×20×0.08 mm, about 40 mg) were placed in a 10 mL beaker containing ethanol (1.0 mL) for 1 minute to remove the phenolphthalein remaining on the film surface, and then transferred to a 100 mL beaker containing a borate pH standard solution (50 mL, pH 9.22, 20 °C). Using a spectrophotometer (UV-2500, Shimadzu Corporation), a portion of the solution (about 1.3 mL) was withdrawn at regular intervals, and the visible absorbance at a wavelength of 554 nm (the maximum absorption wavelength of phenolphthalein) was measured. The measured solution (about 1.3 mL) was returned to the solution after each measurement. The results are shown in Figure 4.

[0087] Figure 5 shows the light transmittance of the aqueous solution at 554 nm with respect to the immersion time of the HTAP film in an alkaline solution (pH 9.22, 20 °C). The times until the light transmittance became almost constant were about 25 minutes, 15 minutes, and 3 minutes for the films of HTAP-1, HTAP-2, and HTAP-3, respectively. The higher the degree of substitution (DS hta ), the shorter the time until the light transmittance became constant. In the naked-eye observation, the HTAP film gradually disintegrated over time in the aqueous solution, and DS htaSince the higher the film, the faster the disintegration rate, the time until the light transmittance becomes almost constant is considered to depend on the affinity of the cationic group for water molecules.

[0088] As described above, HTAP is dispersed in methanol when the degree of substitution is 0.80 or higher, and better dispersibility is achieved when the degree of substitution is greater than 1.0. SEM, SPM, and TEM analyses suggested that HTAP is dispersed in water and methanol in the form of nanofibers. For HTAP with a degree of substitution exceeding 1.20, it was confirmed that it is well-dispersed not only in methanol but also in other binary organic solvents. Also, even after HTAP is dried once, it can be redispersed in water, methanol, and other binary organic solvents by dissolving it in an aqueous sodium hydroxide solution, neutralizing it with hydrochloric acid, and then adding it to ethanol to obtain a wet HTAP solid. This proves that, unlike cellulose nanofibers, which are difficult or impossible to redisperse once dried, HTAP nanofibers have high redispersibility. Since methanol has high volatility, a cast film could be easily prepared from a methanol dispersion of HTAP.

[0089] Two characteristics of HTAP films due to the nanofiber structure: - Reversible hygroscopicity of the HTAP film (absorption / desorption of moisture in the air and change in transparency due to environmental humidity); and - The ability to prepare a film while incorporating methanol-soluble dye molecules and to slowly release them by immersion in an aqueous solution were revealed. The latter characteristic was made possible by the water solubility and dispersibility of HTAP in methanol. Although the detailed mechanism of the dispersibility of HTAP in methanol due to the cationic HTA group has not been elucidated, it is considered that by introducing it in excess at a degree of substitution much higher than the degree of substitution required for water dispersibility (0.01), the alkyl groups such as methyl groups of the cationic group exhibit hydrophobicity.

[0090] [Comparative Example 1] Synthesis of HTAC Cubical dissolved pulp pieces (NSPP-HR, α-cellulose 95.2% or more, manufactured by Nippon Paper Industries) with an approximate size of 1 mm square were immersed in 2-propanol (5.14 g) and water (1.43 g) for 3 hours, and then 50 wt% sodium hydroxide aqueous solution (1.13 g) was added. After leaving it at room temperature for 24 hours, the same amounts of 2-propanol, water, and 50 wt% sodium hydroxide aqueous solution were added. After 17 hours, the swollen dissolved pulp was separated by suction filtration and washed three times with methanol (200 mL) on a funnel. The swollen pulp was placed in a 100 mL eggplant flask, 1.0 N sodium hydroxide aqueous solution (50 mL) and GTAC (80 wt%, 35.425 g, 186.90 mmol) were added, and the mixture was heated and stirred at 73 °C for 6 hours. The resulting heterogeneous solution was adjusted to pH 3 with concentrated hydrochloric acid and then poured into 120 mL of ethanol. The white solid was separated by centrifugation (1460 ×g) and washed by stirring in methanol (300 mL) (twice, overnight). By air drying (overnight) and vacuum heating drying (60 °C, 6 hours), a cellulose derivative (HTAC) with an HTA group introduced was obtained (yield 91.9%, 1.1414 g, 5.626 mol). The degree of substitution was determined to be 0.31 based on the elemental analysis value and the following formula. DS hta =(162×N) / (1400-151.6×N) N is the weight percentage of nitrogen atoms in the elemental analysis value of HTAC, 162 is the molecular weight of the glucose unit, and 151.6 is the molecular weight of GTAC. It was confirmed by FT-IR that it is the target compound. FT-IR(cm -1 ) 3296,2887,1017,898

[0091] Despite the same synthesis conditions as in Examples 1 to 3, the degree of substitution of HTAC was very low at 0.31. This is thought to be because, unlike paramylon, cellulose does not dissolve in the reaction solvent and has to react in a heterogeneous state.

[0092] (Confirmation of nanofibers by scanning electron microscope (SEM)) For the obtained HTAC, SEM observation was performed in the same manner as for HTAP. Fig. 6(a) shows the SEM photograph of the dissolving pulp used in the synthesis of HTAC. Fig. 6(b) shows the SEM photograph of the obtained HTAC. As shown in Fig. 6, both the dissolving pulp and HTAC are fibers with a diameter of about several tens of micrometers, and no difference is observed in appearance. HTAC did not form nanofibers.

[0093] (Preparation of methanol dispersion) A sample of HTAC solid (52.2 mg) was placed in 20 mL of methanol and mechanically stirred for 72 hours. Fig. 7 shows a photograph after stirring for 72 hours. As shown in Fig. 7, white precipitates were observed, indicating that HTAC does not disperse in methanol. The dispersibility in water was confirmed in the same manner as above except that water was used instead of methanol, and white precipitates were observed. From this, it was found that HTAC does not disperse in water either.

Claims

1. Comprising a β-1,3-glucan having a structure in which at least one hydrogen atom of at least one hydroxy group of at least one glucose residue is substituted with a cationic functional group, wherein the degree of substitution of the cationic functional group is 0.80 or more per glucose unit of the β-1,3-glucan, and the cationic functional group is a trialkylammoniohydroxyalkyl group, a cationized paramylon.

2. The cationized paramylon according to claim 1, wherein the β-1,3-glucan has a structure represented by the following formula (I): (In formula (I), n represents an integer from 60 to 3000, and R １ represents a hydrogen atom or a cationic functional group, provided that at least one cationic functional group is included.)

3. The cationized paramylon according to claim 1 or 2, wherein the cationic functional group is a 2-hydroxy-3-trimethylammoniopropyl group.

4. A nanofiber comprising the cationized paramylon according to any one of claims 1 to 3.

5. A dispersion comprising the cationized paramylon according to any one of claims 1 to 3 and a solvent.

6. The dispersion according to claim 5, wherein the solvent contains methanol.

7. The dispersion according to claim 5 or 6, wherein the solvent contains methanol and one or more selected from the group consisting of a halogen solvent, a protic solvent, and an aprotic solvent.

8. The dispersion according to any one of claims 5 to 7, wherein the solvent contains water.

9. An article comprising the cationized paramylon according to any one of claims 1 to 3.

10. The article according to claim 9, further comprising a compound having a solubility of 1% by mass or more in a solvent containing water or methanol at 21°C.

11. The article according to claim 9 or 10, which is a film.

12. A method for producing nanofibers, comprising: (i) reacting a raw material β-1,3-glucan with a compound having a cationic functional group to prepare a cationic functional group-containing β-1,3-glucan having a degree of substitution of the cationic functional group of 0.80 or more per glucose unit of the β-1,3-glucan; and (ii) placing a reaction solution containing the cationic functional group-containing β-1,3-glucan in a poor solvent to obtain a nanofiber aggregate, wherein the cationic functional group is a trialkylammoniohydroxyalkyl group. ​ ​

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