Chitin hydrogel and method for preparing the same

Abstract

The present disclosure provides a chitin hydrogel and a preparation method thereof, wherein the preparation method comprises: heating a mixed solution containing chitosan and a thermoforming gel material, wherein the concentration of chitosan is 0.1-10%, and the concentration of the thermoforming gel material is 0.5-10%; freezing the heated mixed solution to obtain a chitosan-containing hydrogel, wherein the chitosan-containing hydrogel has an anisotropic orientation structure; placing the chitosan-containing hydrogel into an organic solvent to replace the aqueous solution, then placing it into an acetic anhydride methanol solution for acetylation crosslinking, and then placing it into an aqueous solution for solvent exchange to obtain the chitin hydrogel.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of hydrogel materials, in particular to a chitin hydrogel and a preparation method thereof, and more particularly to a chitin hydrogel prepared based on solvent exchange assisted acetylation cross-linking. BACKGROUND

[0002] Hydrogel materials have great application prospects in the biomedical field. However, the development of hydrogel materials has been challenged by many problems such as the self-toxicity of hydrogel materials, insufficient cell compatibility, immune rejection in vivo, lack of anti-fouling ability leading to inflammation or rejection reaction in vivo, and the like. Chitin is a natural biomass material with biocompatibility, biodegradability and sustainability. However, due to the stable hydrophobicity of chitin material, the preparation of chitin hydrogel material has always been a great challenge. The existing preparation strategies have problems such as insufficient mechanical properties, introduction of toxic reagents, harsh conditions, high cost, complex process and difficult large-scale preparation, which restrict the application of chitin hydrogel materials in biomedical hydrogel materials.

[0003] Therefore, it is of great significance to develop a green and efficient method for preparing chitin hydrogel material, to improve the mechanical properties and anti-fouling ability of the material, and to broaden the application of chitin hydrogel material in the biomedical field. SUMMARY

[0004] In view of the above technical problems, the present disclosure provides a chitin hydrogel and a preparation method thereof, so as to at least partially solve the above-mentioned technical problems.

[0005] In order to solve the above technical problems, the technical solutions provided by the present disclosure are as follows:

[0006] As one aspect of the present disclosure, a preparation method of a chitin hydrogel is provided, comprising:

[0007] heating a mixed solution containing chitosan and thermoforming gel material, wherein the concentration of chitosan is 0.1-10%, and the concentration of thermoforming gel material is 0.5-10%;

[0008] freezing the heated mixed solution to obtain a chitosan-containing hydrogel, wherein the chitosan-containing hydrogel has an anisotropic orientation structure;

[0009] After the chitosan-containing hydrogel is placed in an organic solvent for solvent replacement, it is placed in an acetic anhydride methanol solution for acetylation cross-linking, and then placed in an aqueous solution for solvent exchange to obtain a chitin hydrogel.

[0010] In one embodiment, the concentration of the acetic anhydride methanol solution is 0.1-90%;

[0011] The acetylation crosslinking temperature is 0-80℃;

[0012] The acetylation crosslinking time is 1-12h.

[0013] In one of the embodiments, the mixed solution is an acidic aqueous solution, including one or more of formic acid solution, acetic acid solution, propionic acid solution and hydrochloric acid solution.

[0014] The concentration of the acidic aqueous solution is 0.05-5%.

[0015] The mass ratio of chitosan to the acidic aqueous solution is 2:1.

[0016] In one of the embodiments, the freezing mode includes any one of disordered freezing, unidirectional freezing, bidirectional freezing and tridirectional freezing.

[0017] In one of the embodiments, the freezing mode has a temperature of-200-0℃ and a cooling rate of 0.1-200℃ / min.

[0018] In one of the embodiments, the anisotropic structure includes any one of lamellar structure, columnar structure and cell-like structure.

[0019] In one of the embodiments, the preparation method provided by the present disclosure further includes:

[0020] The freezing is replaced by cooling at room temperature, and the chitosan-containing hydrogel obtained by cooling at room temperature has an isotropic structure.

[0021] In one of the embodiments, the thermoforming gel material includes one or more of agarose, agar powder, gelatin, polyvinyl alcohol, polyacrylic acid, protein and sodium alginate.

[0022] The organic solvent includes one or more of ethanol, methanol and isopropanol.

[0023] In another aspect of the present disclosure, a chitin hydrogel is provided, which is prepared by the above preparation method.

[0024] In one of the embodiments, the water content of the chitin hydrogel is higher than 90%.

[0025] Based on the above technical solutions, the chitin hydrogel and the preparation method thereof provided by the present disclosure have at least one of the following beneficial effects:

[0026] (1) By the preparation method in the embodiments of the present disclosure, the formation of the chitin hydrogel is based on the generation of amide bonds on chitosan, and the mechanical properties of the chitin hydrogel can be adjusted by adjusting the concentrations and adding proportions of the reactants.

[0027] (2) The present disclosure casts a chitosan-containing hydrogel with an anisotropic orientation structure by freezing technology, thereby endowing the chitin hydrogel with anisotropy, wherein the anisotropic orientation structure can fine-tune the freezing kinetics parameters to precisely control the internal structure of the hydrogel according to different requirements, endow the chitin hydrogel with anisotropic mechanical properties, improve the controllability of the internal structure of the chitin hydrogel, and enhance the mass transfer of the hydrogel.

[0028] (3) In the embodiments of the present disclosure, a chitin hydrogel with an anisotropic orientation structure can be obtained by constructing a chitosan-containing hydrogel framework, followed by organic solvent replacement, acetylation crosslinking, and water solvent replacement, which is green and environmentally friendly, and the process is relatively simple, and has the prospect of large-scale application. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is the infrared test graph of the chitin hydrogel in Example 1;

[0030] Figure 2 is the mechanical property test graph of the chitin hydrogel in Example 1 after soaking in different organic solvents;

[0031] Figure 3 is the mechanical property test graph of the chitin hydrogel in Example 1 after soaking in different acid and alkali solutions;

[0032] Figure 4 is the optical graph and scanning electron microscope graph of the chitin hydrogel in Example 1 after drying and reswelling;

[0033] Figure 5 is the mechanical test graph of the chitin hydrogel in Example 1 after reswelling;

[0034] Figure 6 is the scanning electron microscope graph of the chitin hydrogel in Example 1 after the anti-fouling ability test;

[0035] Figure 7 is the optical graph of the chitin hydrogel and the un-acetylated hydrogel after soaking in the embodiments of the present disclosure;

[0036] Figure 8 is the scanning electron microscope graph and laser confocal graph of the chitin hydrogel in the embodiments of the present disclosure;

[0037] Figure 9 is the thermogravimetric test graph of the chitin hydrogel in the embodiments of the present disclosure;

[0038] Figure 10 is the mechanical property test of the chitin hydrogel in the embodiments of the present disclosure;

[0039] Figure 11Figure 1 is a test diagram of the adsorption amount of chitin hydrogel to bovine serum albumin in embodiments of the present disclosure. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present disclosure clearer, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the drawings.

[0041] In the process of implementing the present disclosure, it is found that chitin, i.e. chitosan, is a fascinating biopolymer found in living organisms, which can meet the current demands for availability, sustainability, biocompatibility, biodegradability, functionality and renewability, and is an ideal material for preparing hydrogels in the field of regenerative medicine. However, due to the relatively large molecular weight and complex hydrogen bond structure and internal crystalline region of chitin, it is difficult to dissolve in ordinary aqueous and organic solvents. This makes the processing process complex, which limits the large-scale development and application of chitin materials, and chitin is still the least biomass resource. At present, the main difficulty in preparing chitin hydrogel is the difficulty of chitin in various solvents. The most commonly used strategy for preparing chitin hydrogel is to dissolve it through a mixed solution system of alkali and urea, and then prepare chitin hydrogel through physical or chemical cross-linking strategy. However, the existing preparation method of chitin hydrogel has the problems of poor mechanical properties of the obtained hydrogel material, uncontrollable degradation conditions, toxic products, difficult internal structure control, and complex preparation process, which restricts the application of chitin hydrogel.

[0042] Based on the above problems existing in the prior art, the present disclosure provides a chitin hydrogel and a preparation method thereof. The chitin hydrogel with excellent mechanical properties, no cytotoxicity and good antifouling property is obtained by constructing a chitosan-containing hydrogel framework with internal anisotropic structure through freezing technology, replacing organic solvent, then acetylating and cross-linking, and then replacing water to obtain the chitin hydrogel. The preparation method is simple, easy to operate and low in cost, and the obtained chitin hydrogel can be widely used in the field of biomedical materials.

[0043] Specifically, according to the embodiments of the present disclosure, the present disclosure provides a preparation method of chitin hydrogel, comprising:

[0044] heating a mixed solution containing chitosan and thermoforming gel material, wherein the concentration of chitosan is 0.1-10%, and the concentration of thermoforming gel material is 0.5-10%;

[0045] freezing the heated mixed solution to obtain a chitosan-containing hydrogel, wherein the chitosan-containing hydrogel has an anisotropic orientation structure;

[0046] The chitosan-containing hydrogel is placed into an organic solvent for solvent replacement, then into an acetic anhydride methanol solution for acetylation crosslinking, and then into an aqueous solution for solvent replacement to obtain the chitin hydrogel.

[0047] According to an embodiment of the present disclosure, the thermoforming gel material comprises one or more of agarose, agar powder, gelatin, polyvinyl alcohol, polyacrylic acid, protein, and sodium alginate; and the organic solvent comprises one or more of ethanol, methanol, and isopropyl alcohol.

[0048] In an embodiment of the present disclosure, the entire process of preparing the chitin hydrogel is carried out in a wet state environment without freeze-drying. Specifically, a mixed solution of chitosan and agarose is configured, wherein the concentration of chitosan is 0.1-10%, preferably 3%; the thermoforming gel material can be agarose with a concentration of 0.5-10%, preferably 3%; and the uniformly mixed solution is heated to 80-90℃ in a microwave oven or oven until the agarose is completely dissolved. After heating and uniform mixing, the solution is poured into a mold for directional freezing, and the chitosan-containing agarose hydrogel with anisotropic orientation structure is obtained by adjusting the freezing parameters. The frozen chitosan-containing agarose hydrogel is placed into an ethanol solution for thawing and preliminary solvent replacement, and the water in the hydrogel framework is replaced. Then, the chitosan-containing agarose hydrogel is placed into a methanol solution for sufficient solvent replacement, and then into an acetic anhydride methanol solution for acetylation crosslinking. Finally, the chitin hydrogel is obtained by immersing the chitosan-containing agarose hydrogel in water for 12-72 hours, and the water solution is replaced multiple times during the immersion to remove the residual solvent and acetic anhydride solution in the gel.

[0049] According to an embodiment of the present disclosure, the mixed solution is an acidic aqueous solution comprising one or more of formic acid solution, acetic acid solution, propionic acid solution, and hydrochloric acid solution, and the chitosan is completely dissolved by adjusting the pH of the solution with the acidic solution; the concentration of the acidic aqueous solution is 0.05-5%; and the mass ratio of chitosan to the acidic aqueous solution is 2:1.

[0050] According to an embodiment of the present disclosure, the concentration of the acetic anhydride methanol solution is 0.1-90%;

[0051] The acetylation crosslinking temperature is 0-80℃;

[0052] The acetylation crosslinking time is 1-12h.

[0053] In an embodiment of the present disclosure, the concentration of the acetic anhydride methanol solution is 0.1-90%, preferably 10%; the acetylation temperature is 0-80℃, preferably 4℃; and the acetylation crosslinking time is 1-12h, preferably 3h. By adjusting the concentration of the acetic anhydride methanol solution, the acetylation crosslinking temperature, and the acetylation crosslinking time, the mechanical strength of the chitin hydrogel can be controlled.

[0054] According to an embodiment of the present disclosure, the freezing mode includes any one of disordered freezing, unidirectional freezing, bidirectional freezing, and tridirectional freezing.

[0055] According to an embodiment of the present disclosure, the freezing mode has a temperature of -200 to 0℃ and a cooling rate of 0.1 to 200℃ / min.

[0056] According to an embodiment of the present disclosure, the anisotropic orientation structure includes any one of a lamellar structure, a columnar structure, and a cell-like structure.

[0057] In an embodiment of the present disclosure, by adjusting the freezing mode, the cooling rate, the concentration of chitosan in the solution, and the like, the type of the anisotropic orientation structure, the interlayer gap, and the pore size in the hydrogel can be controlled.

[0058] According to an embodiment of the present disclosure, the preparation method provided by the present disclosure further includes:

[0059] The freezing is replaced by cooling at room temperature, and the chitosan-containing hydrogel obtained by cooling at room temperature has an isotropic orientation structure.

[0060] In an embodiment of the present disclosure, the mixed solution of the heated chitosan and the gel material is not subjected to a freezing step, and is cooled into a chitosan-containing hydrogel at room temperature, and the chitin hydrogel obtained by acetylation and cross-linking of the chitosan-containing hydrogel does not have an anisotropic orientation structure.

[0061] According to an embodiment of the present disclosure, a chitin hydrogel is provided, which is prepared by the above preparation method.

[0062] According to an embodiment of the present disclosure, the water content of the chitin hydrogel is higher than 90%.

[0063] In an embodiment of the present disclosure, the chitin hydrogel obtained by the above preparation method has a water content higher than 90%, is non-cytotoxic, has strong anti-fouling ability and excellent robustness, and after drying at 60℃ or below, can be swelled into a chitin hydrogel with a water content of about 70% in an aqueous solution again, and the mechanical strength of the swelled hydrogel is enhanced.

[0064] In order to make the purpose, technical scheme and advantages of the present disclosure clearer and more definite, the technical scheme and principles of the present disclosure are further described and explained below by specific embodiments in combination with the drawings. It should be noted that the following specific embodiments are only used as examples, and the protection scope of the present disclosure is not limited thereto.

[0065] In the following examples, the test materials and reagents used, unless otherwise specified, can be obtained from commercial channels. If the specific techniques or conditions are not specified in the examples, they are conventional methods, which can be performed according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0066] Example 1

[0067] A method for preparing a chitin hydrogel, comprising:

[0068] A mixed solution of chitosan and agarose is prepared, wherein the concentration of chitosan is 3%, the concentration of agarose is 1%, and 1.5% of an aqueous acetic acid solution is added to control the pH of the solution to be acidic so that the chitosan is completely dissolved. After that, the mixed solution is placed in a microwave oven and heated to boiling. The heated mixed solution is cooled at room temperature to obtain an isotropic chitosan-containing agarose hydrogel with an isotropic structure.

[0069] The isotropic chitosan-containing agarose hydrogel is placed in an ethanol solution for solvent replacement, and then placed in a methanol solution for solvent replacement. Then, the chitosan-containing agarose hydrogel is placed in a 10% acetic anhydride methanol solution for acetylation crosslinking, wherein the temperature of acetylation crosslinking is 4°C. The sample obtained after acetylation crosslinking is soaked in deionized water for 24 hours, and the water solution is replaced 5 times during the soaking period to remove the residual methanol and acetic anhydride solution on the hydrogel, thereby obtaining an isotropic chitin hydrogel.

[0070] The composition of the chitin hydrogel obtained above is analyzed by Fourier infrared spectroscopy, Figure 1 is the infrared test graph of the chitin hydrogel in Example 1. As can be seen from the graph, the peak intensity of the chitin hydrogel generated by acetylation crosslinking is reduced compared with chitosan and agarose, and there is a new peak at 1500-1750 cm -1 There is an amide bond generated by acetylation of chitosan, and the presence of the amide bond is the key to the formation of the chitin hydrogel.

[0071] The obtained chitin hydrogel samples are respectively soaked in n-hexane, ethanol, acetone, dichloromethane, trichloromethane, dimethyl sulfoxide, N,N-dimethylformamide, a hydrochloric acid solution with a pH of 1, a sodium hydroxide solution with a pH of 12, a 1M sodium hydroxide solution, and a 2% acetic acid solution for one day. The chitin hydrogel samples are taken out, the solution on the surface of the samples is wiped off, and the mechanical properties of the samples are tested using a pressure testing machine.

[0072] Figure 2 is the mechanical property test graph of the chitin hydrogel in Example 1 after soaking in different organic solvents; Figure 3 is the mechanical property test graph of the chitin hydrogel in Example 1 after soaking in different acid and base solutions. As shown in Figure 2 , the chitin hydrogel can still exhibit good mechanical properties after soaking in various organic solvents and can resist erosion by organic solvents; as shown in Figure 3 , the chitin hydrogel can still exist stably under extreme acid and base conditions and exhibits significant robustness.

[0073] In addition, the isotropic chitin hydrogel obtained in Example 1 was placed in an oven at 50°C for drying, and the drying time was 3-24h according to the sample size. After drying completely, the chitin hydrogel was taken out and soaked in water for at least 12h. The mechanical properties of the chitin hydrogel were tested using a pressure testing machine.

[0074] Figure 4 is the optical and scanning electron microscope images of the chitin hydrogel after drying and reswelling in Example 1; Figure 5 is the mechanical test image of the chitin hydrogel after reswelling in Example 1.

[0075] In the prior art, the method of freeze-drying is used in the preparation of hydrogel, which removes the bound water in the hydrogel. After drying, the hydrogel cannot be reswelled into a hydrogel. The hydrogel obtained by the preparation method of the present disclosure is dried in an oven, which does not remove the bound water inside the chitin hydrogel. As shown in Figure 5 , the chitin hydrogel after drying can be reswelled into a hydrogel after soaking in water. The mechanical properties of the hydrogel after drying and reswelling are significantly improved, and the water content is high, about 75%.

[0076] Further, the anti-fouling ability of the chitin hydrogel was tested, and the anti-fouling ability of the chitin hydrogel to Escherichia coli, Staphylococcus aureus, blood and platelets was tested respectively.

[0077] (1) The hydrogel sample prepared in Example 1 was placed in the wells of a 24-well tissue culture plate, and 1mL of fresh broth was added to each well; 20μL of activated suspension of Escherichia coli or Staphylococcus aureus was added to the wells of the culture plate, and incubated at 37°C for 36h; then the chitin hydrogel was taken out and rinsed with phosphate buffered saline (PBS) solution, and then soaked in 2% glutaraldehyde solution for 24h;

[0078] (2) The chitin hydrogel prepared in Example 1 was placed in the wells of a 24-well tissue culture plate, and 1mL of platelet-rich plasma or 1mL of fresh rabbit blood was added, and incubated at 37°C for 3h; then the chitin hydrogel was taken out and rinsed with PBS, and then soaked in 2.5% glutaraldehyde solution for 24h.

[0079] The chitin hydrogels in (1) and (2) were dehydrated by gradient alcohol-water solution (25%, 50%, 75%, 99%, 100%) and supercritical drying, and the morphology of the adhered bacteria, platelets and blood cells was observed by scanning electron microscope (SEM).

[0080] Figure 6 is the scanning electron microscope image of the chitin hydrogel after anti-fouling ability test in Example 1, and Figure 6It can be observed that only a small amount of bacteria adheres to the surface of the chitin hydrogel, and the chitin hydrogel has obvious anti-adhesion ability to bacteria, blood and platelets.

[0081] Example 2

[0082] A preparation method of a chitin hydrogel comprises:

[0083] A mixed solution of chitosan and agarose is prepared, wherein the concentration of chitosan is 3%, the concentration of agarose is 1%, 1.5% of an aqueous acetic acid solution is added to control the pH of the solution to be acidic so that the chitosan is completely dissolved, and then the mixed solution is placed in an oven and heated to boiling. The heated mixed solution is poured into a mold for directional freezing, and a chitosan-containing agarose hydrogel with a columnar structure is obtained by one-way directional freezing.

[0084] The chitosan-containing agarose hydrogel with a columnar structure after freezing is placed in an ethanol solution for thawing and solvent replacement, and the water in the structural framework is replaced. Then, the chitosan-containing agarose hydrogel with a columnar structure after replacement is placed in a 10% acetic anhydride methanol solution for acetylation crosslinking, wherein the temperature of acetylation crosslinking is 4°C. The sample obtained after acetylation crosslinking is soaked in deionized water for 24 hours, and the water solution is replaced 5 times during the soaking period to remove the residual methanol and acetic anhydride solution on the hydrogel, thereby obtaining a chitin hydrogel with a columnar structure and an anisotropic orientation structure.

[0085] The isotropic chitin hydrogel obtained in Example 1, the anisotropic chitin hydrogel obtained in Example 2, and the chitosan hydrogel without acetylation are soaked in a deionized water solution for 2 hours, and the state of the hydrogels is compared. Figure 7 is an optical diagram of the chitin hydrogel and the unacetylated hydrogel after soaking in the present embodiment of the disclosure. It can be observed from the diagram that the state of the isotropic chitin hydrogel and the anisotropic chitin hydrogel has almost no change, and cracks appear on the surface of the unacetylated hydrogel. The chitosan in the unacetylated hydrogel will gradually be lost after soaking.

[0086] Example 3

[0087] The same preparation method as in Example 2 is used, except that the freezing method is two-way directional freezing, thereby obtaining a chitosan-containing agarose hydrogel with a layered structure, and finally obtaining a chitin hydrogel with a layered structure and an anisotropic orientation structure.

[0088] The chitin hydrogels obtained in Examples 1-3 are tested and analyzed.

[0089] The internal morphology of the hydrogels is observed using a scanning electron microscope and a laser confocal microscope, Figure 8are scanning electron microscope images and laser confocal microscope images of the chitin hydrogel in the embodiments of the present disclosure.

[0090] By Figure 8 It can be seen that the internal structure of the chitin hydrogel can be regulated by adjusting the freezing method using the preparation method provided in the present disclosure, and the chitin hydrogel prepared by bidirectional orientation freezing and unidirectional orientation freezing has obvious lamellar orientation structure and columnar orientation structure.

[0091] The water content of the chitin hydrogel was tested using a thermogravimetric analyzer, Figure 9 is a thermogravimetric test image of the chitin hydrogel in the embodiments of the present disclosure. As shown in Figure 9 The water content of the chitin hydrogel with different internal structures prepared by the method provided in the present disclosure can reach more than 95%.

[0092] The mechanical properties of the chitin hydrogel were characterized using a pressure testing machine, Figure 10 is a mechanical property test of the chitin hydrogel in the embodiments of the present disclosure. As shown in Figure 10 The stress change trend of the chitin hydrogel with columnar structure and lamellar structure in the horizontal direction and the vertical direction is different, the elastic modulus is lower in the horizontal direction and higher in the vertical direction, indicating that the chitin hydrogel with columnar structure and lamellar structure has anisotropic mechanical properties.

[0093] Further, the protein absorption detection of the chitin hydrogel prepared in Examples 1-3 to the protein resistance was tested by micro-BCA protein detection kit, the chitin hydrogel sample was placed in the hole of a 24-hole tissue culture plate, immersed in 1 mL of bovine serum albumin (BSA) solution with a concentration of 2.5 mg / mL at 37°C for 150 minutes; then the hydrogel was taken out and washed with 0.9% sodium chloride solution to remove the loosely absorbed protein; the washed hydrogel sample was placed in 20 μL of 0.9% sodium chloride solution, 200 μL of BCA working solution was added, and after ultrasonic treatment, it was placed at room temperature for 2 hours. The protein concentration was determined by micro-BCA protein detection kit (Beyotime Biotechnology Co, Ltd), and the absorption amount of bovine serum albumin was calculated from the concentration of the standard protein solution.

[0094] Figure 11 is a test image of the absorption amount of bovine serum albumin by the chitin hydrogel in the embodiments of the present disclosure; as shown in Figure 11 The absorption amount of bovine serum albumin on the surface of the chitin hydrogel provided in the present disclosure reaches the level of 1 μg / cm 2 , and the absorption amount of protein is less, which can reduce the possibility of rejection reaction of the hydrogel as a medical material.

[0095] The chitin hydrogel prepared by the method provided by the present disclosure has excellent robustness and can stably exist in various polar solvents or acid-base conditions, and has good anti-adhesion performance to bacteria, blood and proteins, and the mechanical properties can be controlled by adjusting the concentration of reactants or swelling after drying, the internal structure of the chitin hydrogel can be realized by adjusting the freezing parameters, and the chitin hydrogel obtained by acetylation and crosslinking has no cytotoxicity, which has great significance in the biomedical field.

[0096] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present disclosure, and it should be understood that the above description is only a specific embodiment of the present disclosure and is not used to limit the present disclosure, and any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A method for preparing a chitin hydrogel, comprising: heating a mixed aqueous solution containing chitosan and a thermoforming gel material, wherein the concentration of the chitosan is 0.1-10% and the concentration of the thermoforming gel material is 0.5-10%; freezing the heated mixed aqueous solution to obtain a chitosan-containing hydrogel, wherein the freezing mode comprises any one of unidirectional freezing, bidirectional freezing, and tridirectional freezing, and the chitosan-containing hydrogel has an anisotropic orientation structure; placing the chitosan-containing hydrogel into an organic solvent for solvent replacement, then into a methanol solution of acetic anhydride for acetylation crosslinking, and then into deionized water for solvent exchange to obtain a chitin hydrogel, wherein the water content of the chitin hydrogel is higher than 90%. 2.The method of claim 1, wherein: the concentration of the methanol solution of acetic anhydride is 0.1-90%; the temperature of the acetylation crosslinking is 0-80 ℃; the time of the acetylation crosslinking is 1-12 h. 3.The method of claim 1, wherein: the mixed aqueous solution is an acidic aqueous solution comprising one or more of formic acid solution, acetic acid solution, propionic acid solution, and hydrochloric acid solution; the concentration of the acidic aqueous solution is 0.05-5%; the mass ratio of the chitosan to the acidic aqueous solution is 2:

1. 4.The method of claim 1, wherein: the temperature of the freezing mode is -200-0 ℃, and the cooling rate is 0.1-200 ℃ / min. 5.The method of claim 1, wherein: the anisotropic orientation structure comprises any one of a lamellar structure, a columnar structure, and a cell-like structure. 6.The method of claim 1, further comprising: replacing the freezing with cooling at room temperature, and the chitosan-containing hydrogel obtained by cooling at room temperature has an isotropic orientation structure. 7.The method of claim 1, wherein: the thermoforming gel material comprises one or more of agarose, agar powder, and gelatin; the organic solvent comprises one or more of ethanol, methanol, and isopropanol. 8.A chitin hydrogel prepared by the method of any one of claims 1-7.

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