JP2010051438A - Method of eliminating organic solvent in structure of chitosan and polymer of biological origin - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for eliminating residual organic solvents contained in a structure consisting of a mixture of chitosan and polymers of a biological origin. <P>SOLUTION: The method for eliminating the organic solvents contained in the structure consisting of the mixture of chitosan and the polymers of the biological origin includes placing the structure in the atmosphere of a solvent other than the organic solvent. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for removing an organic solvent contained in a structure of chitosan and a biological polymer.

  Chitosan is an amino polysaccharide obtained industrially mainly by deacetylating chitin obtained from the exoskeleton of crustaceans such as crabs and shrimps by boiling treatment in concentrated alkali. In general, it can be easily dissolved in acetic acid aqueous solution, and various molded products such as films, fibers and sponges can be made from the solution. Therefore, it is widely used in cosmetics, medical, food, etc. Is preferably used.

  Among these, in particular, when chitosan is used as a material used on the surface of a living body or in a living body, it is necessary to optimize biological, chemical, physical and structural elements. The biodegradability obtained as a sum of these is one of the most important factors for materials used in vivo, but it may be difficult to bring these factors into a preferred range with chitosan alone, Composite materials with other polymers are being considered. Among these, a composite material of collagen, which is a typical biological polymer, has been studied conventionally, and its use as an artificial skin, an artificial blood vessel or a wound dressing material, and an anti-adhesion agent has been studied. (Patent Document 1)

  However, when the prepared chitosan / biological polymer composite is used particularly in the medical field and the cosmetic field, there is a concern about inflammation due to residual acetic acid used during production. One of the special properties of chitosan is that it does not dissolve in water alone but dissolves in aqueous acetic acid. For this reason, it is very common to use acetic acid as a method for producing a chitosan structure, and most of the previously proposed methods for producing chitosan sponges use acetic acid. Usually, acetic acid is finally removed by vacuum drying, but there is a limit to the amount to be removed, and at least 0.1 to 0.5% by weight remains. In reality, the sheet itself may feel an acetic acid odor.

  As a method for removing acetic acid from chitosan sponge, a method of adding a weak acid other than acetic acid together with acetic acid is disclosed (Patent Document 2). However, this method is not directly applicable to a chitosan-collagen composite material. In recent years, materials used in the advanced medical field are also expected to be used by being implanted in the body, and thus higher purity is required than materials used in other applications. In other words, it is necessary to remove impurities such as solvents used in the process completely or reduce them to a safe amount, so that strict removal of acetic acid is required especially when these materials are used in advanced medical applications. Is required. For this reason, the method of removing an acid by heat drying is disclosed (patent document 3). However, in this method, the amount of acetic acid removed is insufficient, and an acetic acid odor may be observed from the chitosan sponge.

Japanese Examined Patent Publication No. 63-59706 JP 2007-2203 A JP 2003-292501 A

  An object of the present invention is to solve the above-described problems of the prior art. That is, an object of the present invention is to provide a method for removing a residual organic solvent contained in a structure composed of a mixture of chitosan and a bio-derived polymer (for example, gelatin).

  As a result of intensive studies to solve the above problems, the present inventors produced a structure comprising a mixture of chitosan and a bio-derived polymer by drying a mixture containing chitosan and a bio-derived polymer in an organic solvent. Then, it was found that the residual organic solvent contained in the structure can be removed by placing the structure in an atmosphere of a solvent different from the organic solvent, and the present invention was completed. .

  That is, according to the present invention, there is provided a method for removing an organic solvent contained in a structure comprising a mixture of chitosan and a bio-derived polymer, wherein the structure is placed in an atmosphere of a solvent different from the organic solvent. Including the above.

  Furthermore, according to the present invention, a step of producing a structure comprising a mixture of chitosan and a biological polymer by drying a mixture containing chitosan and a biological polymer in a solvent containing an organic solvent, and the structure Provided is a method for producing a structure containing chitosan and a bio-derived polymer, which comprises a step of placing in an atmosphere of a solvent different from the organic solvent.

Preferably, the biological polymer is biological gelatin or genetically modified gelatin.
Preferably, the organic solvent contained in the structure composed of a mixture of chitosan and a bio-derived polymer is acetic acid.

Preferably, the solvent other than the organic solvent is a solvent compatible with the organic solvent.
Preferably, the solvent compatible with the organic solvent is a solvent containing water, alcohol or ketone.
Preferably, the solvent compatible with the organic solvent is water.

Preferably, the biological polymer is cross-linked.
Preferably, the crosslinking is performed using heat, light, a condensing agent, or an enzyme.

  According to the present invention, a residual organic solvent contained in a structure composed of a mixture of chitosan and a biological polymer (for example, gelatin) can be strictly removed.

Hereinafter, the present invention will be described in more detail.
<Chitosan>
Chitosan used in the present invention is a deacetylated product of aminopolysaccharide chitin contained in the exoskeleton of crustaceans such as crabs and shrimps, and its chemical structure is a repeating unit of glucosamine or glucosamine and a small amount of N-acetylglucosamine It is a natural polymer. In general, chitosan refers to chitin obtained by deproteinizing a crustacean exoskeleton with an alkaline aqueous solution and decalcifying with a hydrochloric acid aqueous solution, and further deacetylating with a high concentration alkaline aqueous solution such as caustic soda. Generally, the degree of deacetylation of chitosan is 60% or more, and these have the property of not dissolving in water but dissolving in an aqueous solution containing an organic solvent such as acetic acid.

  The production method of chitosan is, for example, about 40 to 60% by weight of chitin obtained by deproteinizing fresh red snow crab shell by treatment with a dilute alkaline aqueous solution such as caustic soda and decalcification treatment using a dilute acid aqueous solution such as hydrochloric acid. The treatment is generally performed for about 5 to 20 hours while maintaining a temperature of about 90 ° C. or higher in a concentrated alkaline aqueous solution. What is obtained by this production is usually in the form of solid flakes, and is generally dried and used as a powder. The obtained chitosan is a polymer and has a high molecular weight after purification, but is generally about 100,000 to 3 million. Usually, the molecular weight can be controlled by dissolving in a certain aqueous acetic acid solution and measuring the solution viscosity. In standard viscosity measurement, 0.5% by weight of chitosan is usually dissolved in an acetic acid aqueous solution, and the viscosity is measured with a B-type viscometer at 20 ° C. The viscosity of ordinary chitosan is 3 to 500 mPa · s, and generally 10 to 250 mPa · s, as described above. For example, the solution viscosity of chitosan having a molecular weight of about 300,000 is about 10 mPa · s.

<Bio-derived polymers>
The biological polymer is not particularly defined, but is preferably a protein, polysaccharide, or a derivative or salt thereof. In the case of protein, it may be any of spherical and fibrous proteins. The biopolymer is preferably collagen, gelatin, albumin, laminin, casein, fibroin, fibrin, fibronectin, vitronectin, hyaluronic acid, and hyaluronic acid ester. More preferred are collagen, gelatin, albumin, casein, and fibroin. Most preferred is collagen or gelatin. The origin of the protein is not particularly limited, and any of humans, cows, pigs, fish, and gene recombinants may be used. Hereinafter, gelatin will be described.

  As used herein, “gelatin” means gelatin having a GXY portion characteristic of collagen. The GXY portion characteristic of collagen is a very specific partial structure in the amino acid composition and sequence of gelatin / collagen compared to other proteins. In this part, glycine accounts for about one third of the whole, and in the amino acid sequence, it is one in three repeats. Glycine is the simplest amino acid, has few constraints on the arrangement of molecular chains, and greatly contributes to the regeneration of the helix structure upon gelation. Amino acids represented by X and Y contain a large amount of imino acids (proline, oxyproline) and occupy 10% to 45% of the whole.

  As the genetically modified gelatin used in the present specification, for example, methods and products described in EP0926543B, WO02 / 052342, EP1063565B, WO2004085473, EP1014176A, US Pat. No. 6,992,172, and the like can be used depending on the purpose.

  The genetically modified gelatin used in the present invention is naturally excellent in biocompatibility and non-infectivity. In addition, since the genetically modified gelatin used in the present invention is more uniform than natural ones and the sequence is determined, the strength and degradability can be precisely designed with less blur due to cross-linking described later. It is.

The genetically modified gelatin used in the present specification is particularly preferably gelatin having the following characteristic (1) and gelatin having the following characteristic (2).
(1) A genetically modified gelatin in which the proportion of polar amino acids is 30 to 60% of the total amino acids and the proportion of uncharged amino acids in the polar amino acids is 70% or more.
The present inventors have found that the biodegradability of a gelatin composition can be suppressed by using a genetically modified gelatin having the above amino acid sequence. In general gelatin, polar amino acids have a charged amino acid and an uncharged one in a ratio of 1: 1. Here, the polar amino acid specifically means cysteine, aspartic acid, glutamic acid, histidine, lysine, asparagine, glutamine, serine, threonine, tyrosine, and polar uncharged amino acids are cysteine, asparagine, glutamine, serine, threonine. Refers to tyrosine. The polar amino acids are preferably serine, glutamine, and asparagine, and the total of these is more preferably 30 to 60% of all amino acids.

  Also preferred is gelatin having a glutamine composition of polar uncharged amino acids of 30% to 80%, more preferably 40% to 60%. Moreover, it is preferable that the ratio of the hydroxyl group with respect to the primary amide of the side chain in a polar uncharged amino acid is 50% or less, and 30% or less is more preferable. More specifically, the ratio of the sum of serine and threonine to glutamine is 60% or less. More preferably, it is 40% or more and 60% or less. More preferably, the ratio of the serine number to the glutamine number is 40% or more and 60% or less. More preferably, it is 50%.

(2) Gelatin characterized in that the amino acid sequence contains 3 to 50 RGD sequences in one molecule.
The present inventors have found that biodegradability of a gelatin composition can be promoted by using a genetically modified gelatin having the above amino acid sequence.

  In general, in a polypeptide, the RGD sequence is known as the minimum amino acid sequence that serves as a cell adhesion signal. (For example, “Pathophysiology” published by Nagai Publishing Co., Ltd., Vol. 9, No. 7 (1990), page 527). The genetically modified gelatin used in the present invention preferably has 3 to 50 RGD sequences in one molecule, more preferably 4 to 30, and particularly preferably 5 to 20. The purpose of the genetically modified gelatin of the present invention was achieved by controlling and expressing these sequences.

  The genetically modified gelatin used in the present invention including the genetically modified gelatin described in the above (1) or (2) is a substantially pure collagen material prepared by a nucleic acid encoding natural collagen. The genetically modified gelatin may be partially hydrolyzed. The gelatin has only to have 40% amino acid identity with the biological collagen sequence, and more preferably 50% or more. More preferably, it is 80% or more, and most preferably 90% or more. Any collagen may be used as long as it exists in nature. In general, the type of sequence required will vary greatly depending on the therapeutic application. That is, it is desirable to have a structure close to the collagen sequence required for each tissue. For example, in the case of a material surface for treating cartilage, an array of type II collagen is desirable. In the case of blood vessels, it is desirable that the outer membrane is type I and the inner membrane is type IV. Preferred are type I, type II, type III, type IV, and type V. More preferred are type I, type II and type III. According to another form, the collagen origin is preferably human, cow, pig, mouse, rat. More preferred is human, and most preferred is a homology with the amino acid sequence of human collagen α1 of 80% or more. The isoelectric point of the genetically modified gelatin is 4 to 10, preferably 6 to 10, and more preferably 7 to 9. Genetically modified gelatin has a GXY part characteristic of collagen and has a molecular weight of 2 KDa or more and 100 KDa or less. More preferably, it is 2.5 KDa or more and 95 KDa or less. More preferably, it is 5 KDa or more and 90 KDa or more. Most preferably, it is 10 KDa or more and 90 KDa or less.

  If the performance of the genetically modified gelatin alone is insufficient, it may be mixed or combined with other materials. For example, natural and different types of genetically modified gelatin, other biopolymers or synthetic polymers may be mixed. Examples of the biopolymer include polysaccharides, polypeptides, proteins, nucleic acids, antibodies and the like. Preferred are polysaccharides, polypeptides, and proteins. Examples of the polysaccharide, polypeptide, and protein include glycosaminoglycan represented by hyaluronic acid and heparin, chitin, chitosan, poly-γ-glutamic acid, collagen, gelatin, albumin, fibroin, and casein. Furthermore, these may be partially chemically modified as necessary. For example, hyaluronic acid ethyl ester may be used.

  The genetically modified gelatin used in the present invention can be chemically modified depending on the application. Chemical modifications include the introduction of low molecular weight compounds or various polymers (biopolymers (sugars, proteins), synthetic polymers, polyamides) into the carboxyl group or amino group of the side chain of genetically modified gelatin, Examples include cross-linking between gelatins. Examples of the introduction of the low molecular weight compound into the genetically modified gelatin include a carbodiimide-based condensing agent.

  In the present invention, the biological polymer may be cross-linked. Crosslinking can preferably be performed using heat, light, a condensing agent, or an enzyme. The crosslinking agent used in the present invention is not particularly limited as long as the present invention can be carried out, and may be a chemical crosslinking agent or an enzyme. Examples of the chemical cross-linking agent include formaldehyde, glutaraldehyde, carbodiimide, cyanamide and the like. Preferred are formaldehyde and glutaraldehyde, and most preferred is glutaraldehyde.

  When performing cross-linking by an enzyme, the enzyme is not particularly limited as long as it has a cross-linking action between genetically modified gelatin chains. Preferably, trans-glutaminase and laccase, most preferably trans-glutaminase is used for cross-linking. it can. A specific example of a protein that is enzymatically cross-linked with transglutaminase is not particularly limited as long as it has a lysine residue and a glutamine residue. The transglutaminase may be derived from a mammal or may be derived from a microorganism. Specifically, transglutaminase derived from a mammal that has been marketed as an activator series manufactured by Ajinomoto Co., Inc., for example, Human-derived blood coagulation factors (Factor XIIIa, Haematologic Technologies, Inc.) such as guinea pig liver-derived transglutaminase, goat-derived transglutaminase, and rabbit-derived transglutaminase manufactured by Oriental Yeast Co., Ltd., Upstate USA Inc. Etc.). When the recombinant gelatin is crosslinked with transglutaminase, the crosslinking efficiency can be improved due to the high glutamine composition. Therefore, the primary amide group in the side chain of the amino acid is preferably twice or more than the carboxylic acid group. Preferably it is 3 times or more. More specifically, as the primary amide, it is desirable that the amount of glutamine is larger than that of glutamic acid. Preferably, the glutamine number is twice or more that of glutamic acid. More preferably, it is 3 times or more.

  The cross-linking of genetically modified gelatin has two processes: a process of mixing a gelatin solution and a cross-linking agent and a process of reacting these uniform solutions.

  In the present invention, the mixing temperature when the gelatin is treated with the crosslinking agent is not particularly limited as long as the solution can be uniformly stirred, but is preferably 0 ° C to 40 ° C, more preferably 0 ° C to 30 ° C, and more Preferably it is 3 degreeC-25 degreeC, More preferably, it is 3 degreeC-15 degreeC, More preferably, it is 3 degreeC-10 degreeC, Most preferably, it is 3 degreeC-7 degreeC.

  After stirring the gelatin and the cross-linking agent, the temperature can be raised. The reaction temperature is not particularly limited as long as the crosslinking proceeds, but is substantially 0 ° C. to 60 ° C., more preferably 0 ° C. to 40 ° C. in view of denaturation and decomposition of the biopolymer. Preferably it is 3 to 25 degreeC, More preferably, it is 3 to 15 degreeC, More preferably, it is 3 to 10 degreeC, Most preferably, it is 3 to 7 degreeC.

<Method for producing a structure comprising a mixture of chitosan and a bio-derived polymer>
Next, the manufacturing method of the structure which consists of a mixture of the chitosan and bio-derived polymer in this invention is demonstrated. Although the manufacturing method of the structure of this invention is not specifically limited as long as the method of this invention is used, For example, it can produce based on the method described in Japanese Patent Publication No.63-59706.

  For example, a structure composed of a mixture of chitosan and a biological polymer can be prepared by drying a mixture containing chitosan and a biological polymer in a solvent containing an organic solvent. Examples of the organic solvent used here (that is, an organic solvent contained in a structure composed of a mixture of chitosan and a bio-derived polymer) include acetic acid. The contents of chitosan and the bio-derived polymer in a solvent containing an organic solvent such as acetic acid are not particularly limited. From the viewpoint of the solubility of chitosan and the bio-derived polymer, generally, the chitosan is 0.05 to 5 The biopolymer is 0.02 to 10% by weight.

  In the present invention, a structure comprising a mixture of chitosan and a biological polymer is produced by drying a mixture containing chitosan and a biological polymer in a solvent containing an organic solvent, and then the structure is combined with the organic solvent. Removes the organic solvent contained in the structure by placing it in an atmosphere of another solvent.

  Residual organic solvents are a problem when used in medical applications. The residual amount of the organic solvent in the structure is preferably 1% by weight or less. More preferably, it is 0.1% by weight or less. Most preferably, it is 0.01 weight% or less.

  There are many criteria for selecting a solvent other than the organic solvent (solvent used in the gas), boiling point, affinity with structures containing residual solvent, safety, compounds contained in the structures (drugs and dyes) Etc. There is no particular restriction on the boiling point of the solvent used in the gas and the residual solvent, but it is more preferably higher than the boiling point of the residual solvent. In another standard, when a structure to be used in a living body is prepared, the solvent used in the gas is preferably water, alcohol or ketone, and more preferably water or alcohol. More preferred is water, ethanol, or isopropanol. More preferred is water or ethanol. Most preferred is water. Moreover, as a solvent used in gas, one type of solvent may be sufficient, or it can also be used as a mixed gas of two or more types of solvents. Further, as another criterion for selection of the solvent used in the gas, it is preferable that the structure can be dissolved or swelled.

  The total ratio of the solvent to the saturated vapor pressure at the temperature in the gas is not particularly specified, but is preferably 55% or more. More preferably, it is 70% or more. Most preferably, it is 80% or more. For example, when the solvent in the gas is water, the ratio of the vapor pressure of the solvent to the saturated vapor pressure is humidity. That is, when the solvent other than the organic solvent is water, the humidity is preferably 55% or more, more preferably 70% or more, and most preferably 80% or more. Further, since the saturated water vapor amount greatly varies depending on the temperature, the required humidity at the temperature at which the solvent is removed may vary. The temperature of the gas is not particularly specified, but is preferably 25 ° C or higher and 200 ° C or lower. More preferably, it is 30 degreeC or more and 100 degrees C or less. Most preferably, it is 35 degreeC or more and 80 degrees C or less. The temperature of the system varies greatly depending on the type of the remaining solvent and the mixture, but is preferably a temperature slightly lower than the boiling point of the remaining solvent (specifically **).

<Structure composed of a mixture of chitosan and biopolymer>
The form of the structure composed of a mixture of chitosan and a bio-derived polymer is not particularly limited, and examples thereof include gels, sponges, films, nonwoven fabrics, fibers (tubes), particles, and the like, and films or sponges are preferable. The sponge has a homogeneous porous structure, and the average pore size is generally 10 to 200 μm in diameter and the density is generally 0.05 or less.

  Any shape can be applied, and examples thereof include a pyramid, a cone, a prism, a cylinder, a sphere, a spindle-shaped structure, and a structure created by an arbitrary mold. Preferred are a prism, a cylinder, a spindle-shaped structure, and a structure made of an arbitrary mold. More preferable are a pyramid, a cone, a prism, and a cylinder. Most preferred are prisms and cylinders. The size of the structure is not particularly limited, but is preferably 500 cm square or less for gels, sponges, and nonwoven fabrics. Preferably it is 100 cm or less. Especially preferably, it is 50 cm or less. Most preferably, it is 10 cm or less. In the case of a fiber (tube), the diameter (or one side) of the fiber or tube is 1 nm or more and 10 cm or less. Preferably they are 1 nm or more and 1 cm or less. More preferably, it is 1 nm or more and 100 μm. Particularly preferably, the thickness is 1 nm or more and 1 μm or less. Most preferably, it is 1 nm or more and 10 nm or less. The length is not particularly limited, but is preferably 10 μm or more and 100 m or less. More preferably, it is 100 μm or more and 10 m or less. More preferably, it is 1 mm or more and 1 m or less. Most preferably, it is 1 cm or more and 30 cm or less. In the case of particles, the diameter is preferably 1 nm to 1 mm, more preferably 10 nm to 200 μm, still more preferably 50 nm to 100 μm, and particularly preferably 100 nm to 10 μm.

  The thickness of the structure is not particularly limited, but is preferably 1 nm or more. More preferably, it is 10 nm or more. More preferably, it is 100 nm or more. More preferably, it is 1 μm or more. More preferably, it is 10 μm or more. Most preferably, it is 100 μm or more.

  An additive may be added to the composition as necessary. Examples of additives include drugs, pigments, softeners, transdermal absorption promoters, humectants, surfactants, preservatives, fragrances, and pH adjusters.

  Specific examples of the drug include, for example, anticancer agents (for example, paclitaxel, topotecin, taxotere, 5-fluorouracil), immunosuppressants (for example, rapamycin, tacrolimus, cyclosporine), anti-inflammatory agents, antithrombotic agents, antipsychotic agents, antidepressants Agents, antioxidants, antiallergic agents, growth factors, hormones, supplement ingredients, cosmetic ingredients.

  The use of the structure is not particularly limited, but is a wound dressing, a transdermal absorption agent, a topical treatment, an oral treatment, a cosmetic, a supplement, a food, and a color material. Preferred are wound dressings, transdermal absorbents, topical therapeutic agents, oral therapeutic agents, and cosmetics. More preferred are a transdermal absorbent, a topical therapeutic agent, an oral therapeutic agent, and a wound dressing, and most preferred are a transdermal absorbent, a topical therapeutic agent, and a wound dressing.

  The following examples further illustrate the present invention, but the present invention is not limited to the examples.

Example 1: Removal of acetic acid from chitosan-gelatin mixture 1 g of chitosan LL-40 and 1 g of acid-treated gelatin (20%, PSP gelatin, manufactured by Nippi) were gradually added to 100 g of a 1% by weight aqueous acetic acid solution at 40 ° C. The mixture was stirred for 2 hours to dissolve and left to degas. This solution was poured into a plastic tray (length 10 cm × 10 cm, depth 1 cm) and vacuum-dried at room temperature for 20 hours.
The sheet was placed in an atmosphere of 50 ° C. and 80% humidity for 2 hours, and then vacuum-dried again for 3 hours. The sheet was immersed in an aqueous solution overnight to extract residual acetic acid. The amount of acetic acid was quantified by GCMS (GCMS-QP2010, manufactured by Shimadzu Corporation, column: DB-624, 60 m, = 0.25 mm).

  When not humidified, the residual acetic acid content was 0.40%. On the other hand, when water was added to the air, that is, the solvent was removed at a humidity of 80%, the amount of residual acetic acid was greatly reduced to 0.008% in 3 hours. When acetic acid was removed, the amount of acetic acid could be efficiently reduced by adding a large amount of water vapor to the gas.

Example 2: Removal of acetic acid from chitosan-gelatin mixture 1 g of chitosan LL-40 and 1 g of acid-treated gelatin (20%, PSP gelatin, manufactured by Nippi) were gradually added to 100 g of a 1 wt% aqueous acetic acid solution at 40 ° C. And stirred for 2 hours to dissolve. 0.5 g of glutaraldehyde was added to this solution and stirred at 5 ° C. for 30 minutes. This solution was left to degas, then poured into a plastic tray (length 10 cm x 10 cm, depth 1 cm), freeze-dried at -40 ° C for 6 hours, and then vacuum-dried for 24 hours to obtain a sponge-like sheet. It was.
The sheet was placed in an atmosphere of 50 ° C. and 90% humidity for 3 hours, and then vacuum-dried again for 3 hours. When the residual acid was quantified in the same manner as in Example 1, the amount of acetic acid was 0.009%.

Comparative Example 1:
1 g of chitosan LL-40 and 1 g of acid-treated gelatin (20%, PSP gelatin, manufactured by Nippi Co., Ltd.) were gradually added to 100 g of a 1% by weight acetic acid aqueous solution and dissolved by stirring at 40 ° C. for 2 hours. . This solution was poured into a plastic tray (length 10 cm × 10 cm, depth 1 cm), freeze-dried at −40 ° C. for 6 hours, and then vacuum-dried at room temperature for 24 hours to obtain a sponge-like sheet.
When this was further vacuum dried at 60 ° C. for 12 hours, the amount of residual acetic acid was 0.34%.

Comparative Example 2:
An aqueous solution in which 1% by weight of acetic acid and 0.15% by weight of citric acid were dissolved was prepared. To 100 g of this aqueous solution, 1 g of chitosan LL-40 and 1 g of acid-treated gelatin (20%, PSP gelatin, manufactured by Nippi Co., Ltd.) were gradually added and dissolved by stirring at 40 ° C. for 2 hours. This solution was poured into a plastic tray (length 10 cm × 10 cm, depth 1 cm), freeze-dried at −40 ° C. for 6 hours, and then vacuum-dried at room temperature for 24 hours to obtain a sponge-like sheet. When the residual acid was quantified in the same manner as in Example 1, the acetic acid content was 0.16%.

Claims (16)

A method for removing an organic solvent contained in a structure comprising a mixture of chitosan and a bio-derived polymer, the method comprising placing the structure in an atmosphere of a solvent different from the organic solvent. The method according to claim 1, wherein the biological polymer is biological gelatin or genetically modified gelatin. The method according to claim 1 or 2, wherein the organic solvent contained in the structure composed of a mixture of chitosan and a bio-derived polymer is acetic acid. The method according to claim 1, wherein the solvent other than the organic solvent is a solvent compatible with the organic solvent. The method according to claim 4, wherein the solvent compatible with the organic solvent is a solvent containing water, alcohol or ketone. The method according to claim 4 or 5, wherein the solvent compatible with the organic solvent is water. The method according to any one of claims 1 to 6, wherein the biological polymer is crosslinked. The method according to claim 7, wherein the crosslinking is performed using heat, light, a condensing agent, or an enzyme. A step of producing a structure comprising a mixture of chitosan and a bio-derived polymer by drying a mixture containing chitosan and the bio-derived polymer in a solvent containing an organic solvent, and the structure separately from the organic solvent A method for producing a structure containing chitosan and a bio-derived polymer, comprising a step of placing in a solvent atmosphere. The method according to claim 9, wherein the biological polymer is biological gelatin or genetically modified gelatin. The method according to claim 9 or 10, wherein the organic solvent contained in the structure composed of a mixture of chitosan and a bio-derived polymer is acetic acid. The method according to claim 9, wherein the solvent other than the organic solvent is a solvent compatible with the organic solvent. The method according to claim 12, wherein the solvent compatible with the organic solvent is a solvent containing water, alcohol or ketone. 14. The method according to claim 12 or 13, wherein the solvent compatible with the organic solvent is water. The method according to any one of claims 9 to 14, wherein the biological polymer is crosslinked. The method according to claim 15, wherein the crosslinking is performed using heat, light, a condensing agent, or an enzyme.