High-strength cross-linked chitosan derivative as well as preparation method and application thereof

Abstract

The invention discloses a high-strength crosslinked chitosan derivative as well as a preparation method and application thereof, and relates to the technical field of medical polymer materials. The product provided by the invention is prepared by a two-step modification process of first crosslinking and then etherification. The product is prepared by taking recrystallized chitosan as a base material, selecting ethylene glycol diglycidyl ether, lactic acid or citric acid as a cross-linking agent for pre-crosslinking to construct a network skeleton, and introducing a hydrophobic chain segment through ring opening etherification of 1, 2-epoxybutane. By optimizing the raw material ratio and reaction conditions, the prepared chitosan derivative has excellent mechanical strength and temperature-sensitive responsiveness, has good fluidity at low temperature, is convenient to smear, and can be quickly gelatinized to form a stable adhesion layer after contacting with body temperature. The product is high in purity and good in biocompatibility, and can be widely applied to the fields of wound dressings, vascular embolism, skin filling and repairing, drug-loaded slow release and the like.

Description

Technical Field

[0001] This application relates to the technical field of pharmaceutical polymer materials, and in particular to a high-strength cross-linked chitosan derivative, its preparation method, and its application. Background Technology

[0002] Chitosan, a deacetylated product of chitin, is a naturally abundant cationic polysaccharide. Its excellent biocompatibility, biodegradability, and low toxicity have garnered significant attention in the biomedical field. However, the strong hydrogen bonds between native chitosan molecular chains result in poor water solubility, insufficient mechanical strength, and a tendency to swell or degrade under physiological conditions, severely limiting its application in high-end medical materials. Chemical modification of chitosan has led to the development of a series of functionalized products, with hydroxybutyl chitosan being a prime example. By introducing hydroxybutyl hydrophilic groups into the chitosan molecular chain, hydroxybutyl chitosan not only significantly improves its water solubility and thermal stability but also endows the material with dual sensitivity to temperature and acidity / alkalinity. It exists as a flowing liquid at low temperatures and rapidly transforms into a non-chemically cross-linked gel upon contact with human body surface temperatures. This thermosensitive phase transition characteristic gives it unique advantages in wound dressings, drug delivery, and other applications.

[0003] However, existing hydroxybutyl chitosan preparation processes still have problems. In actual production, the product purity is low, containing unreacted chitosan raw materials, small molecule byproducts, and residual reagents. When using this as a raw material to prepare solution dressings, irreversible solid-liquid separation easily occurs during high-temperature sterilization, requiring additional complex and cumbersome purification steps, which not only prolongs the production cycle but may also lead to product loss. These factors also result in insufficient material adhesion. After the prepared solution dressing forms a gel on the human body surface, it is prone to detachment or displacement due to activity or body fluid infiltration, failing to maintain a tight fit to the wound and affecting the treatment effect. Due to the low product purity in actual production, the solution yield is also low during the preparation process, thus restricting its large-scale production and industrial application. Summary of the Invention

[0004] The purpose of this application is to provide a high-strength cross-linked chitosan derivative with advantages such as reversible phase transition properties, low viscosity, high strength, high purity, sustained release performance, and good adhesion to the skin surface, making it suitable for applications such as wound dressings, vascular embolization, skin filling and repair, and drug delivery.

[0005] In the first aspect, the high-strength cross-linked chitosan derivative, its preparation method, and its application provided in this application adopt the following technical solution: A high-strength cross-linked chitosan derivative comprises the following raw materials: recrystallized chitosan, 1,2-epoxybutane, cross-linking agent, and alkaline solution; the mass ratio of the recrystallized chitosan, 1,2-epoxybutane, and cross-linking agent is 3000:(45000-69000):(0.5-2); the recrystallized chitosan is prepared by recrystallization of chitosan.

[0006] By employing the above technical solution, the high-strength cross-linked chitosan derivative prepared using this formulation exhibits high cross-linking degree and excellent mechanical strength, while retaining the biocompatibility of chitosan, combining stability and functionality. Recrystallizing chitosan improves product purity. Recrystallized chitosan, as the main component, contains numerous amino and hydroxyl groups in its molecular chains, and the lyophilized powder has a large specific surface area, facilitating thorough contact and reaction with subsequent reagents. 1,2-Epoxybutane, as an etherifying agent, allows the epoxy groups to undergo ring-opening reactions with the amino groups of chitosan, introducing hydrophobic butyl chains. This improves the dispersibility of chitosan in organic solvents and provides more reaction sites for cross-linking. Simultaneously, this mass ratio ensures complete etherification, avoiding incomplete reactions due to insufficient reagents. The addition of a cross-linking agent allows for pre-cross-linking with chitosan through its own functional groups, constructing a network structure that enhances chitosan stability and improves the adhesion of the prepared hydroxybutyl chitosan product. This mass ratio of the three components achieves an excellent combination of etherification modification and cross-linking reaction, ensuring that the chitosan molecular chain is fully modified and that a stable network is formed through appropriate cross-linking, ultimately resulting in a high-strength derivative with balanced performance.

[0007] Optionally, the crosslinking agent is any one or more of ethylene glycol diglycidyl ether, lactic acid, and citric acid.

[0008] By adopting the above technical solution, ethylene glycol diglycidyl ether, lactic acid, and citric acid were selected as crosslinking agents, all of which can efficiently crosslink with chitosan derivatives. Ethylene glycol diglycidyl ether contains two epoxy groups, lactic acid contains one carboxyl group, and citric acid contains three carboxyl groups; all are multifunctional or active functional group compounds. The epoxy groups of ethylene glycol diglycidyl ether can undergo ring-opening reactions with the amino and hydroxyl groups of chitosan, resulting in high crosslinking efficiency and stable ether bonds, significantly improving the mechanical strength and water resistance of the material. The carboxyl groups of lactic acid react with the amino groups of chitosan, resulting in a mild crosslinking process, and lactic acid has excellent biocompatibility, not affecting the biosafety of the product. The three carboxyl groups of citric acid can form multi-point crosslinks with the chitosan molecular chains, constructing a dense network structure that enhances the structural stability of the material. Simultaneously, the introduction of carboxyl groups improves the hydrophilicity of the product. All three are compatible with the system reaction; single or combined use can be selected according to requirements, ensuring crosslinking effectiveness while considering different performance requirements such as product biocompatibility and stability.

[0009] Optionally, the chitosan has a degree of deacetylation of 85-95% and a viscosity of 200-800 mPa·s.

[0010] By employing the above technical solution, the degree of deacetylation of chitosan determines the amino content in the molecular chain. This range of deacetylation ensures sufficient reaction between the amino groups and the epoxy groups of 1,2-epoxybutane and the active functional groups of the crosslinking agent. It avoids both excessively low deacetylation leading to insufficient reaction sites and inadequate crosslinking, and excessively high deacetylation causing excessively strong hydrogen bonds between molecular chains, which easily lead to aggregation. The viscosity range reflects the molecular chain length; low viscosity results in short chains and insufficient network strength after crosslinking, while high viscosity leads to poor system flowability. This range of deacetylation and viscosity allows the product to possess both good crosslinking structure and processability, maintaining reliable mechanical properties in biomedical materials and other fields, while also being easily processed into films, gels, and other forms, adapting to different application scenarios. This range of deacetylation and viscosity of chitosan facilitates swelling and crosslinking in ethanol, playing a crucial role in subsequent activation. The degree of activation determines the degree of substitution of the final product. The higher the degree of deacetylation, the smaller the molecular weight, and the higher the requirements for activation. The higher the viscosity of chitosan, the higher the viscosity and strength of the prepared hydroxybutyl chitosan, resulting in a more brittle film. However, the degree of deacetylation in this range has moderate strength, which is more in line with actual needs.

[0011] Optionally, the alkaline solution includes sodium hydroxide or potassium hydroxide; the mass fraction of the alkaline solution is 45-55 wt%.

[0012] By employing the above technical solution, both sodium hydroxide and potassium hydroxide are strong electrolytes that, upon dissolving in water, efficiently dissociate into hydroxide ions, providing a sufficient alkaline environment for the reaction to activate the chitosan amino groups. This mass fraction range of alkaline solution provides the optimal alkaline environment for the reaction. This concentration range ensures sufficient hydroxide ions to activate the amino groups while avoiding insufficient activation at excessively low concentrations, which could lead to slow reaction rates and incomplete substitution. Simultaneously, appropriate hydroxide ions act as a catalyst, ensuring the degree of substitution of hydroxybutyl groups and promoting effective bonding between functional groups. Excessively high concentrations or prolonged reaction times may trigger chitosan gelation or molecular chain degradation. This range of alkaline solution precisely balances amino activity and reaction stability, ensuring the successful formation of the substituted structure.

[0013] Optionally, a method for preparing a high-strength cross-linked chitosan derivative includes the following steps: S1. Mix recrystallized chitosan and ethanol, stir to disperse, heat, add crosslinking agent, stir at constant temperature, filter, wash, filter again to obtain filter cake for later use. S2. Add the filter cake prepared in step S1 to the alkaline solution, stir and disperse, heat, seal and stand at constant temperature, filter to obtain activated chitosan. S3. The activated chitosan prepared in step S2 is mixed with isopropanol, water, and 1,2-epoxybutane, heated and stirred to obtain modified chitosan. S4. Add water to the modified chitosan prepared in step S3, wash, stir, let stand, filter to obtain filter cake, wash repeatedly, dissolve the filter cake, filter to obtain filtrate, add acid solution to filtrate, stir, and obtain purified chitosan derivative solution. S5. The purified chitosan derivative solution prepared in step S4 is dried under vacuum to obtain the high-strength cross-linked chitosan derivative.

[0014] By employing the above technical solution, this preparation method optimizes the performance of chitosan through the synergistic effect of crosslinking and modification. In step S1, the combination of chitosan and the crosslinking agent first constructs a preliminary crosslinking network, improving the structural stability of chitosan. Alkaline solution activation treatment exposes more active groups of chitosan molecules, laying the foundation for subsequent modification. 1,2-Epoxybutane enhances intermolecular interactions through ring-opening modification, further densifying the crosslinked structure and endowing the material with thermosensitive properties, high strength, and excellent rheological mechanical properties. The purification step removes impurities and unreacted components, ensuring product purity, and vacuum drying preserves the integrity of the crosslinking network. This method crosslinks recrystallized chitosan before the ring-opening reaction of 1,2-epoxybutane, and does not require nitrogen gas during the alkaline solution activation process, making experimental operation more convenient. The chitosan derivatives prepared by this method have both good swelling stability and degradation resistance, making them suitable for biomedical materials, adsorption separation, and other fields. They can withstand the mechanical loads in practical applications and exert highly efficient functional effects.

[0015] Optionally, the mass ratio of recrystallized chitosan in step S1, isopropanol in step S3, and water in step S3 is 1:(7-10):(8-10).

[0016] By employing the above technical solution, this mass ratio ensures that chitosan swells appropriately in isopropanol. This avoids both excessive solvent leading to too low a chitosan concentration and insufficient cross-linking points, and insufficient solvent preventing chitosan from fully expanding and its active sites from being exposed. This balanced state promotes uniform contact between the cross-linking agent and chitosan molecules, allowing for a more complete cross-linking reaction and the formation of a dense, high-strength cross-linked network, thus improving the mechanical properties and stability of the product. Appropriate moisture content helps maintain good dispersion of the filter cake, which is beneficial for subsequent steps.

[0017] Optionally, in step S2, the constant temperature is 35-45℃ and the standing time is 20-30h.

[0018] By adopting the above technical solution, the mild constant temperature conditions in step S2 can prevent the degradation of cross-linked chitosan molecular chains. At the same time, the alkaline solution can swell and activate the filter cake, helping to expose more active groups. Sufficient standing time can prevent the cross-linked chitosan from gelling and allow the activation effect to penetrate deep into the molecular chain, ensuring uniform and thorough activation, creating good conditions for subsequent reactions and improving the binding stability.

[0019] Optionally, the heating temperature in step S1 is 40-50℃, the heating temperature in step S2 is 35-45℃, and the heating temperature in step S3 is 57-59℃.

[0020] By adopting the above technical solution, the selected temperature range in step S1 promotes the full dispersion of chitosan in the mixed system, creating conditions for the contact between the crosslinking agent and the molecular active sites, and driving the crosslinking reaction to proceed gently and uniformly. The temperature range in step S2 effectively promotes the development of active groups in the crosslinked chitosan, while the temperature range in step S3 prevents the volatilization of 1,2-epoxybutane and provides sufficient reaction sites for subsequent modification reactions, ensuring the stability of the product's structure and properties.

[0021] Optionally, the acid solution in step S4 is hydrochloric acid, and the pH value of the purified chitosan derivative solution is 6.0-8.0.

[0022] By adopting the above technical solution, the pH is adjusted to 6.0-8.0 using hydrochloric acid solution in step S4, which has both precise control and structural protection functions. Hydrochloric acid, as a strong acid, can precisely control the pH of the system without introducing impurities. At the same time, this pH environment can inhibit the hydrolysis of chitosan derivatives, reduce molecular chain degradation, and prevent excessive acid or alkalinity from damaging the cross-linked structure formed in step S3, maintaining network integrity and laying the structural foundation for the subsequent vacuum drying preparation of high-strength products.

[0023] Secondly, the high-strength cross-linked chitosan derivative, its preparation method, and its application provided in this application adopt the following technical solution: Application of a high-strength cross-linked chitosan derivative in the fields of biomedicine, drug delivery, and sustained drug release.

[0024] In this formula, some of the ingredients and their functions are as follows: Recrystallized chitosan: As a core raw material, recrystallized chitosan provides a large number of amino and hydroxyl active sites for the preparation of chitosan derivatives. Its lyophilized powder form has a large specific surface area, which is conducive to full contact and reaction with crosslinking agents and 1,2-epoxybutane. It reacts with crosslinking agents to build a stable network structure, improving material strength; and undergoes a ring-opening reaction with 1,2-epoxybutane to introduce hydrophobic segments, preserving biocompatibility. These properties enable chitosan derivatives in thermosensitive dressings to maintain structural stability through the crosslinking network, achieve thermosensitive response through amino groups, and promote wound healing through biocompatibility, providing multiple guarantees for the dressing in terms of structural support, functional regulation, and biocompatibility.

[0025] 1,2-Epoxybutane: In its preparation, 1,2-epoxybutane acts as an etherifying agent. It is produced by ring-opening 1,2-epoxybutane, where the epoxy groups react with the hydroxyl and amino groups on the chitosan molecular chain, introducing hydrophobic butyl segments. This modification optimizes the dispersibility of chitosan in organic solvents and enhances intermolecular forces through hydrophobic interactions, thereby improving the mechanical strength of the product. In thermosensitive dressings, the hydrophobic chains synergize with the original hydrophilic groups of chitosan, imparting thermoresponsiveness to the material, regulating its swelling and drug release behavior at different temperatures, while maintaining biocompatibility and adapting to the wound healing environment.

[0026] Crosslinking agents: During preparation, crosslinking agents react with the hydroxyl groups on the chitosan molecular chain through their own multifunctional groups to construct a three-dimensional crosslinked network. For example, the epoxy groups of ethylene glycol diglycidyl ether undergo ring-opening crosslinking with the active groups of chitosan to form stable ether bonds, significantly improving the mechanical strength and water resistance of the material. The carboxyl groups of lactic acid or citric acid react with the hydroxyl groups, resulting in a mild crosslinking process that introduces hydrophilic groups, balancing biocompatibility and structural stability. This crosslinking effect allows chitosan derivatives in thermosensitive dressings to maintain structural integrity to withstand mechanical loads while also regulating swelling and drug release rates through the network, adapting to the dynamic environment of wound healing.

[0027] Alkaline solution: In this application, the alkaline solution is sodium hydroxide. Sodium hydroxide, as an alkaline solution, releases hydroxide ions that promote the deprotonation of chitosan amino groups to form highly active amino anions, activating key active sites for subsequent reactions. Simultaneously, the hydroxide ions act as a catalyst, lowering the activation energy of the reaction and facilitating reactions such as epoxy ring-opening.

[0028] Anhydrous ethanol: Anhydrous ethanol primarily acts as a bipolar solvent and dispersion medium, enabling the recrystallized chitosan to disperse uniformly. After swelling, the crosslinking agent, in an acidic environment, creates a uniform environment for the initial crosslinking reaction. This ensures effective binding between the crosslinking agent and the active sites of chitosan molecules, contributing to the stable construction of the initial crosslinked network.

[0029] Acid solution: The acid solution can regulate the reaction rate, avoid excessively rapid cross-linking leading to uneven network structure, and ensure the effective exposure of active groups in the subsequent alkaline activation step. Adding an acid solution to the preparation of purified chitosan solution can effectively control the stability of chitosan derivatives, further ensuring the quality of the products obtained in subsequent preparations and the quality of dressings made from chitosan derivatives.

[0030] Isopropanol: Isopropanol serves as a dispersion medium and a bipolar solvent, being soluble in both water and 1,2-epoxybutane. Its polar environment can regulate the reactivity of 1,2-epoxybutane, promoting the uniform ring-opening etherification reaction between the epoxy groups and the hydroxyl and amino groups of chitosan.

[0031] Water plays a crucial role in multiple stages of the preparation process. In step S1, adding water and sealing the filter cake for settling removes residual solvents and water-soluble impurities. In step S3, water acts as a co-mediator with isopropanol, dispersing the activated chitosan in water and 1,2-epoxybutane in isopropanol. As the reaction time increases, the two reaction systems gradually form a homogeneous system, promoting uniform etherification modification. In step S4, water washing removes unreacted small molecules and residual reagents, purifying the product. When dissolving the filter residue, water acts as a solvent to fully dissolve the chitosan derivatives, filtering out unreacted substances and other impurities.

[0032] In summary, this application includes at least one of the following beneficial technical effects: 1. Compared with existing technologies, the pre-construction of the chitosan network framework using a crosslinking agent significantly improves the stability of the molecular structure. This crosslinking pretreatment provides a more regular reaction platform for the subsequent etherification reaction of 1,2-epoxybutane. The prepared hydroxybutyl chitosan achieves simultaneous optimization in terms of strength and viscosity, and the intermolecular forces are more balanced. When used as a substrate for temperature-sensitive functional dressings, it exhibits excellent adhesion properties after gelation, adhering tightly to the wound surface without easily falling off, providing a continuous and stable physical barrier and moist healing environment for wound repair, making it particularly suitable as a raw material for high-performance medical materials. 2. Compared with existing technologies, the product prepared by this method has higher purity, effectively reducing production cycle and cost. The chitosan derivative prepared by this method has more thorough control over solvent residue, significantly improving process safety and product biocompatibility, resulting in a significantly improved yield and higher raw material utilization, which is conducive to large-scale stable production. Attached Figure Description

[0033] Figure 1 This is the hydrogen spectrum of chitosan from Example 8 of this application; Figure 2 This is the hydrogen spectrum of the chitosan derivative (hydroxybutyl chitosan) of Example 8 of this application; Figure 3 This is the infrared spectrum of the chitosan derivative (hydroxybutyl chitosan) of Example 8 of this application; Figure 4 This is the residual solvent gas chromatogram of Example 8 of this application; Figure 5 This is a gas chromatogram of 1,2-epoxybutane and isopropanol from this application; Figure 6 This is a viscosity test chart of Example 8 of this application; Figure 7 This is a viscosity full scan test graph from Example 8 of this application; Figure 8 This is the viscosity test graph of Comparative Example 4 of this application; Figure 9This is a temperature test diagram from Embodiment 8 of this application; Figure 10 This is the temperature test diagram of Comparative Example 4 of this application; Figure 11 This is the elastic modulus test diagram of Embodiment 8 of this application; Figure 12 This is the elastic modulus test diagram of Comparative Example 4 of this application; Figure 13 This is an adhesion test diagram of Embodiment 8 of this application. Detailed Implementation

[0034] Unless otherwise specified, all raw materials used in the embodiments and comparative examples of this application are commercially available products: Chitosan, degree of deacetylation 90.6%, viscosity 650 mPa·s, Qingdao Hehai Biotechnology Co., Ltd.

[0035] Example 1 A high-strength cross-linked chitosan derivative and its preparation method, comprising the following steps: The first step is to prepare recrystallized chitosan.

[0036] 50g of chitosan was mixed with 5L of 1wt% hydrochloric acid and stirred at 500rpm for 3h at 30℃ to obtain the first mixture. 1wt% sodium hydroxide solution was added to the first mixture, causing flocculent matter to precipitate. The flocculent matter was filtered through a 30-mesh sieve to obtain the precipitate. The precipitate was washed with water until neutral, then washed with 75wt% ethanol solution to remove salts. After squeezing out excess solution, the precipitate was freeze-dried at -40℃ for 48h. After freeze-drying, it was pulverized to obtain recrystallized chitosan.

[0037] The second step is to prepare chitosan derivatives.

[0038] 15g of recrystallized chitosan was added to 150mL of anhydrous ethanol and stirred at 500rpm for 1h to obtain a second mixture. The mixture was heated to 45℃, and 0.005g of ethylene glycol diglycidyl ether was added. The mixture was stirred at 500rpm for 2h at a constant temperature of 45℃ to obtain a third mixture. The third mixture was filtered to obtain a first filter cake, which was then washed with anhydrous ethanol to obtain a precipitate. The precipitate was filtered to obtain a second filter cake, which was then washed twice with water and set aside.

[0039] 150g of sodium hydroxide was mixed with 150g of water at 500rpm for 30min to obtain a 50wt% sodium hydroxide solution. The second filter cake was added to the sodium hydroxide solution and stirred at 500rpm for 1h. The mixture was then sealed and allowed to stand at 40℃ for 24h. After filtration, activated chitosan was obtained.

[0040] Activated chitosan was added to 135g of water and stirred at 500rpm for 30min. Then, 118g of isopropanol and 225g of 1,2-epoxybutane were mixed and stirred at 500rpm for 1h at 20℃ to obtain a fourth mixture. The fourth mixture was heated to 58℃ and stirred at 500rpm for 30h to obtain modified chitosan.

[0041] Modified chitosan was added to 1200 mL of water and stirred at 500 rpm for 8 min. The mixture was allowed to stand until it separated into layers. The upper layer was taken and added to 1500 mL of water, then stirred at 500 rpm for 8 min to obtain the fifth mixture. The fifth mixture was filtered through a 300-mesh filter to obtain the third filter cake. The third filter cake was repeatedly filtered and washed until the pH of the washing liquid and the filtrate were the same, then filtered to obtain the fourth filter cake. The fourth filter cake was soaked in 80℃ water for 20 h, washed and filtered three times with 80℃ water to obtain the fifth filter cake. The fifth filter cake was added to 1 L of water and stirred at 500 rpm for 4 h at 5℃ to obtain the sixth mixture. The sixth mixture was filtered through a 300-mesh filter, and the filtrate was retained. The filtrate was stirred at 5℃ for 4 h, and the pH was measured to be 7.3. The mixture was then dried under vacuum at 60℃ and 0.08 MPa for 24 h to obtain the high-strength cross-linked chitosan derivative.

[0042] Example 2 The difference between Example 2 and Example 1 is that 225g of 1,2-epoxybutane in Example 1 is replaced with 255g of 1,2-epoxybutane.

[0043] Example 3 The difference between Example 3 and Example 1 is that 225g of 1,2-epoxybutane in Example 1 is replaced with 300g of 1,2-epoxybutane.

[0044] Example 4 The difference between Example 4 and Example 1 is that 225g of 1,2-epoxybutane in Example 1 is replaced with 315g of 1,2-epoxybutane.

[0045] Example 5 The difference between Example 5 and Example 1 is that 225g of 1,2-epoxybutane in Example 1 is replaced with 330g of 1,2-epoxybutane.

[0046] Example 6 The difference between Example 6 and Example 1 is that 225g of 1,2-epoxybutane in Example 1 is replaced with 345g of 1,2-epoxybutane.

[0047] Example 7 The difference between Example 7 and Example 4 is that the 0.005g ethylene glycol diglycidyl ether in Example 1 is replaced with a mixture of 0.005g ethylene glycol diglycidyl ether and 0.005g lactic acid.

[0048] Example 8 The difference between Example 8 and Example 4 is that the 0.005g ethylene glycol diglycidyl ether in Example 1 is replaced with a mixture of 0.005g ethylene glycol diglycidyl ether, 0.0025g lactic acid, and 0.0025g citric acid.

[0049] Comparative Example 1 The difference between Comparative Example 1 and Example 4 is that 0.005g of ethylene glycol diglycidyl ether was replaced with 0.005g of glutaraldehyde.

[0050] Comparative Example 2 The difference between Comparative Example 2 and Example 4 is that 0.005g of ethylene glycol diglycidyl ether was replaced with 0.005g of gallic acid.

[0051] Comparative Example 3 The difference between Comparative Example 3 and Example 4 is that ethylene glycol diglycidyl ether was not added in Comparative Example 3.

[0052] Comparative Example 4 Comparative Example 4 uses commercially available hydroxybutyl chitosan.

[0053] Application examples 2.0 g of the high-strength cross-linked chitosan derivatives prepared in Examples 1-8 and Comparative Examples 1-4, 100 g of water, and 3 g of glycerol were mixed and stirred at 500 rpm for 2 h at 5°C to obtain a mixture. The mixture was filtered to obtain filter residue, which was then packaged and sterilized by moist heat to obtain a dressing. The mass fraction of the dressing was 2 wt%.

[0054] Test case Gas chromatography: The gas chromatograph was a GC-2010PLUS1; the sample was hydroxybutyl chitosan; the reference standards were isopropanol and 1,2-epoxybutane. The test method was as follows: 1. Take 1.0 g of the chitosan derivative solution prepared in Example 8 and dilute it to the mark in a 10 mL volumetric flask. 2. Use N,N-dimethylacetamide aqueous solution as the test solution and place it in the gas chromatograph headspace sampler. 3. Perform the test. The test results are shown in the sample group. Figure 4 and reference standard Figure 5 .

[0055] Acute systemic toxicity test: According to GB / T 16886.11-2021 Biological evaluation of medical devices - Part 11: Systemic toxicity testing; According to GB / T 16886.12-2023 Biological Evaluation of Medical Devices Part 12: Sample Preparation and Reference Materials Test results: In Example 8, no symptoms of animal death or systemic toxicity were observed during the experimental observation period, and the animals' weight showed no obvious abnormalities.

[0056] Skin sensitization test: Skin sensitization tests were conducted in accordance with GB / T 16886.10-2024 "Biological evaluation of medical devices - Part 10: Skin sensitization tests"; GB / T 16886.12-2023 Biological evaluation of medical devices – Part 12: Sample preparation and reference materials Test results: The dressing sample prepared in Example 8 did not cause any skin sensitization reaction.

[0057] Intradermal reaction test: According to GB / T 16886.23-2023 Biological Evaluation of Medical Devices Part 23: Stimulation Testing According to GB / T 16886.12-2023 Biological Evaluation of Medical Devices Part 12: Sample Preparation and Reference Materials Test results: The intradermal irritation reaction of the dressing sample prepared in Example 8 met the test requirements.

[0058] Heat source experiment: GB / T 16886.11-2021 Biological evaluation of medical devices - Part 11: Systemic toxicity testing; GB / T 16886.12-2023 Biological evaluation of medical devices - Part 12: Sample preparation and reference materials Test results: The pyrogen test of the dressing sample prepared in Example 8 met the requirements.

[0059] In vitro cytotoxicity assay: According to GB / T 16886.5-2017 Biological Evaluation of Medical Devices Part 5: In Vitro Cytotoxicity Tests According to GB / T 16886.12-2023 Biological Evaluation of Medical Devices Part 12: Sample Preparation and Reference Materials Test results: The dressing sample prepared in Example 8 showed no potential cytotoxicity.

[0060] Shear viscosity testing of dressings: The 2% hydroxybutyl chitosan solutions prepared in Examples 1-8 and Comparative Examples 1-3 were tested using a rheometer (model DHR-2) on a 40 mm diameter plate at 7°C, a shear rate of 50 l / s, and a time of 60 s. The test results are shown in Table 1. The test results for the product prepared in Example 8 are shown in Table 1. Figure 6 The viscosity full scan test results are shown below. Figure 7 The viscosity test results of the product prepared in Comparative Example 4 are shown below. Figure 8 The elastic modulus test diagram of Embodiment 8 of this application is shown below. Figure 11 ; Figure 12 The elastic modulus test diagram of Comparative Example 4 of this application is shown below. Figure 12 .

[0061]

[0062] The high-strength crosslinking agent chitosan derivative prepared by this method, at 7°C, exhibits a 2% concentration solution that is almost a Newtonian fluid, as water is a Newtonian fluid. Therefore, the solution has very low and stable shear viscosity, resulting in better fluidity and easier skin adhesion. Consequently, dressings made from chitosan derivatives prepared by this method can be easily applied to the skin.

[0063] The optimized elastic modulus of modified chitosan derivatives allows them to better meet the needs of vascular embolization. They possess sufficient structural support to stably occlude the target vessel, preventing displacement or occlusion failure due to excessively low modulus; at the same time, they have appropriate elasticity to accommodate the physiological contraction and relaxation of blood vessels, reducing mechanical damage to the vessel wall and lowering the risk of postoperative recanalization. This provides a material support for vascular embolization that combines safety and effectiveness.

[0064] Dressing temperature detection method: A TA rheometer (model DHR-2) was used on a 40 mm diameter plate with a starting temperature of 7°C and an ending temperature of 30°C, a rate of 5°C / min, a strain of 1%, and a frequency of 1 Hz to test 2% concentration chitosan derivative solutions prepared in Examples 1-8 and Comparative Examples 1-3.

[0065] Test results: The product completely transformed from liquid to solid at 17.04℃, with a solidification time of less than 60 seconds. Commercially available hydroxybutyl chitosan raw materials, when prepared into an aqueous gel state, have a gelation temperature of 25℃ and high viscosity, indicating that the hydroxybutyl chitosan prepared in this method can be used in dressings for a wider range of human skin temperatures. The test results for the product prepared in Example 8 are shown below. Figure 9 The results of the comparative test 4 are shown in Figure 10 .

[0066] Adhesion: The product prepared in Example 8 was mixed with 3g of glycerin to prepare an aqueous solution (dressing). This solution was applied to the back of the hand and finger joints. The aqueous solution solidified 5 seconds after contact with the skin. During normal walking and arm movement, the dressing did not peel off or shift. After 90 minutes, a transparent film formed, adhering tightly to the skin. The test results for Example 8 are shown below. Figure 13 .

[0067] Comparative analysis of Examples 1-6 and Comparative Example 3 revealed that the shear viscosity of Example 4 was similar to that of Examples 5 and 6, but the shear viscosity of Example 4 was slightly better than that of Examples 5 and 6. This performance difference is mainly due to the amount of 1,2-epoxybutane used. When the amount of 1,2-epoxybutane in the crosslinked chitosan reaches a certain level in this substitution reaction, the substitution value will not increase further with increasing 1,2-epoxybutane after reaching its peak. Chitosan molecules are rich in amino and hydroxyl groups, and their crosslinking modification effect is closely related to the reactivity between functional groups and the crosslinking network structure. As an etherification modifier, 1,2-epoxybutane's epoxy groups can undergo ring-opening reactions with the amino and hydroxyl groups of chitosan, introducing hydrophobic butyl ether segments onto the molecular chain and providing active sites for crosslinking. When the 1,2-epoxybutane content is within the range of Example 4, the introduced butyl ether segments are neither too low, resulting in insufficient intermolecular forces, nor too high, causing excessive steric hindrance that hinders the contact between the crosslinking agent and the active groups. Appropriate etherification modification balances the flexibility and reactivity of the chitosan molecular chains, allowing ethylene glycol diglycidyl ether to efficiently connect adjacent molecular chains, forming a moderately dense and uniform crosslinked network. In contrast, Comparative Example 3, lacking a crosslinking agent, cannot form a stable three-dimensional structure solely through weak intermolecular interactions. The lower 1,2-epoxybutane content in Examples 1-3 resulted in insufficient introduced active sites and a lower crosslinked network density, ultimately leading to Example 4 exhibiting superior shear strength properties.

[0068] Comparative analysis of Example 4 with Comparative Examples 1 and 2 revealed that Example 4 exhibited superior performance. This is likely because the ethylene glycol diglycidyl ether used in Example 4 demonstrated better compatibility in crosslinking modification compared to glutaraldehyde in Comparative Example 1 and gallic acid in Comparative Example 2. While glutaraldehyde exhibits strong crosslinking activity, its high toxicity limits its application in biological fields. Gallic acid requires strict pH control to maintain amino activity; otherwise, improper acid-base conditions can lead to decreased crosslinking efficiency. Furthermore, the reaction rate between its polyphenolic hydroxyl groups and amino groups is slow, requiring longer reaction times, which hinders process optimization. In contrast, ethylene glycol diglycidyl ether, as an epoxy resin crosslinking agent, not only has low viscosity and is easily mixed uniformly with the system, but also exhibits mild ring-opening reaction conditions with the chitosan amino and hydroxyl groups at both ends, requiring no complex pH control. Its high reaction efficiency allows for the rapid construction of a stable three-dimensional crosslinked network, combining safety and process convenience, thus demonstrating superior performance.

[0069] A comparative analysis of Examples 4 and 7 revealed that the chitosan derivative prepared in Example 7 exhibited better shear strength. This difference in performance is likely due to the use of lactic acid, which, along with ethylene glycol diglycidyl ether, exerts a synergistic effect. In Example 7, the synergistic effect of lactic acid and ethylene glycol diglycidyl ether stems from the acidic catalytic and group activation effects of lactic acid. The weakly acidic environment provided by lactic acid protonates the amino groups on the chitosan molecular chain, enhancing its nucleophilicity, while simultaneously activating the epoxy groups of ethylene glycol diglycidyl ether. This synergistic effect makes it easier for the epoxy groups at both ends of the ethylene glycol diglycidyl ether to undergo efficient ring-opening crosslinking reactions with the hydroxyl groups of chitosan, reducing side reaction losses during the reaction process. Compared to Example 4, which used only ethylene glycol diglycidyl ether, the synergistic system exhibits higher crosslinking point formation efficiency, a more uniform density of the formed three-dimensional crosslinked network, and enhanced inter-chain bonding strength, thus demonstrating superior shear strength performance in Example 7.

[0070] A comparative analysis of Examples 7 and 8 revealed that the chitosan derivative prepared in Example 8 exhibited better elastic modulus properties. This difference is likely due to the addition of citric acid in Example 8. In Example 8, ethylene glycol diglycidyl ether, lactic acid, and citric acid exhibited a synergistic effect. This synergistic effect may stem from the complementary catalytic action of the polybasic acids and the synergistic activation of functional groups. As a tricarboxylic acid, citric acid's carboxyl group can co-construct a weakly acidic system with lactic acid, more efficiently tetrocking the amino groups of chitosan. Simultaneously, the carboxyl group forms hydrogen bonds with the hydroxyl groups of chitosan, assisting the epoxy groups of ethylene glycol diglycidyl ether in locating near the active site, reducing steric hindrance. Compared to Example 7, which only contained lactic acid, the introduction of citric acid not only enhanced the acidic catalytic efficiency but also guided the epoxy groups to undergo directional ring-opening crosslinking with the amino and hydroxyl groups, reducing network defects caused by random crosslinking. In addition, the carboxyl group of citric acid can form an ester bond with the hydroxyl group generated after the ring opening of ethylene glycol diglycidyl ether, further increasing the number of crosslinking points, making the three-dimensional crosslinking network denser and more uniform, significantly improving the efficiency and selectivity of the crosslinking reaction in Example 8, and making the formed crosslinking structure more stable and having stronger inter-chain forces, thus exhibiting a performance with an elastic modulus superior to that of Example 7.

[0071] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A high-strength cross-linked chitosan derivative, characterized in that, The raw materials include: recrystallized chitosan, 1,2-epoxybutane, crosslinking agent, and alkaline solution; the mass ratio of recrystallized chitosan, 1,2-epoxybutane, and crosslinking agent is 3000:(45000-69000):(0.5-2); the recrystallized chitosan is prepared by recrystallization of chitosan.

2. The high-strength cross-linked chitosan derivative according to claim 1, characterized in that, The crosslinking agent is any one or more of ethylene glycol diglycidyl ether, lactic acid, and citric acid.

3. The high-strength cross-linked chitosan derivative according to claim 1, characterized in that, The chitosan has a degree of deacetylation of 85-95% and a viscosity of 200-800 mPa·s.

4. The high-strength cross-linked chitosan derivative according to claim 1, characterized in that, The alkaline solution comprises sodium hydroxide or potassium hydroxide; the mass fraction of the alkaline solution is 45-55 wt%.

5. A method for preparing a high-strength cross-linked chitosan derivative, characterized in that, Includes the following steps: S1. Mix recrystallized chitosan and ethanol, stir to disperse, heat, add crosslinking agent, stir at constant temperature, filter, wash, filter again to obtain filter cake for later use. S2. Add the filter cake prepared in step S1 to the alkaline solution, stir and disperse, heat, seal and stand at constant temperature, filter to obtain activated chitosan. S3. The activated chitosan prepared in step S2 is mixed with isopropanol, water, and 1,2-epoxybutane, heated and stirred to obtain modified chitosan. S4. Add water to the modified chitosan prepared in step S3, wash, stir, let stand, filter to obtain filter cake, wash repeatedly, dissolve the filter cake, filter to obtain filtrate, add acid solution to filtrate, stir, and obtain purified chitosan derivative solution. S5. The purified chitosan derivative solution prepared in step S4 is dried under vacuum to obtain the high-strength cross-linked chitosan derivative.

6. The method for preparing the high-strength cross-linked chitosan derivative according to claim 5, characterized in that, The mass ratio of recrystallized chitosan in step S1, isopropanol in step S3, and water in step S3 is 1:(7-10):(8-10).

7. The method for preparing the high-strength cross-linked chitosan derivative according to claim 5, characterized in that, In step S2, the constant temperature is 35-45℃, and the standing time is 20-30h.

8. The method for preparing the high-strength cross-linked chitosan derivative according to claim 5, characterized in that, The heating temperature in step S1 is 40-50℃, the heating temperature in step S2 is 35-45℃, and the heating temperature in step S3 is 57-59℃.

9. The method for preparing the high-strength cross-linked chitosan derivative according to claim 5, characterized in that, In step S4, the acid solution is hydrochloric acid, and the pH value of the purified chitosan derivative solution is 6.0-8.

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10. The application of the high-strength cross-linked chitosan derivative as described in any one of claims 1-4 in the fields of biomedicine, drug delivery, and sustained release.

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