Chitosan / cellulose acetate nanofiber membrane and preparation method thereof
By preparing chitosan/cellulose acetate nanofiber membranes, using electrospinning technology and specific ternary solvent systems, the problems of insufficient biocompatibility and adsorption capacity of existing endotoxin adsorbents are solved, and efficient and safe endotoxin removal effect is achieved.
Patent Information
- Application Number
- CN202510626482.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-15
- Publication Date
- 2025-08-15
AI Technical Summary
The existing endotoxin adsorbents have poor biocompatibility or limited adsorption capacity, making it difficult to effectively remove endotoxins in the blood.
Chitosan/cellulose acetate nanofiber membranes are prepared by electrospinning technology and using a ternary solvent system with a specific composition ratio, and combined with the cationic groups of CS and the three-dimensional pore structure of CA to form a dual mechanism of electrostatic adsorption and physical interception.
It realizes high biocompatibility and efficient endotoxin adsorption function, significantly improves the clearance rate of endotoxins, and reduces the hemolysis rate and thromboplastin time, ensuring the safety of the material.
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Abstract
Description
Technical Field
[0001] The present invention relates to the field of biofilms, and in particular to a chitosan / cellulose acetate nanofiber membrane and a preparation method thereof. Background Art
[0002] Endotoxins, components of the cell wall of Gram-negative bacteria, possess potent immunostimulatory and inflammatory properties, inducing a range of pathophysiological responses. For example, endotoxins are a key pathogenic factor in the development of sepsis, activating cytokines in the liver and triggering a robust immune response, potentially leading to renal failure, liver damage, or death. Therefore, removing endotoxins from the blood is a key technology for improving patient survival. Hemoperfusion (HP) has the ability to efficiently adsorb large molecular weight solutes. Compared to hemodialysis (HD), hemofiltration (HF), and hemodiafiltration (HDF), HP is one of the most effective methods for removing endotoxins from the blood. Hemoperfusion separates and removes toxins by binding to an adsorbent material. The choice of adsorbent material is crucial for hemoperfusion technology. A good hemoperfusion adsorbent should possess high specific surface area, good adsorption capacity, good biocompatibility, and minimal impact on the blood. Currently, various adsorbents have been used for the separation and removal of endotoxins, such as polymyxin B-immobilized fiber columns, activated carbon adsorbents, anion exchange resins, and affinity adsorbents. However, these adsorbents either have poor biocompatibility or have certain limitations in their adsorption and separation capabilities.
[0003] Chitosan (CS) is a natural cationic linear polysaccharide derived from chitin, found in the shells of crustaceans and in the cell walls of insects and fungi. Its unique structure endows it with a range of excellent properties, including excellent biocompatibility, nontoxicity, and biodegradability. This has attracted considerable attention in numerous fields, particularly medicine, where it is widely used in drug delivery, wound dressings, and tissue engineering. CS molecules contain abundant amino groups, which can specifically adsorb to the negatively charged phosphate groups in endotoxin molecules through electrostatic interactions, thus also being used as an adsorbent for endotoxin removal. However, CS is only soluble in specific acidic solutions and has poor processing properties, which limits its application. Cellulose acetate (CA), a modified natural polymer, is biodegradable, chemically stable, has good biocompatibility, is low cost, and exhibits excellent processability. It plays an important role in drug controlled-release systems, medical dressings, and hemodialysis membranes.
[0004] The present invention aims to provide a chitosan / cellulose acetate nanofiber membrane for endotoxin adsorption. By co-dissolving CA and CS and applying an electrospinning process to prepare the nanofiber membrane, CA serves as a matrix to improve the electrospinning performance of CS. Furthermore, CS enhances the specific adsorption of endotoxins by the CA nanofiber membrane, achieving complementary and optimized performance. This results in a chitosan / cellulose acetate nanofiber membrane with high biocompatibility and efficient endotoxin adsorption. Summary of the Invention
[0005] To solve the above problems, the present invention aims to provide a chitosan / cellulose acetate nanofiber membrane and a preparation method thereof. The preparation method selects a ternary solvent system with specific components and composition ratios, and strikes a balance between the viscosity, conductivity and solvent volatilization rate of the chitosan / cellulose acetate mixed solution, thereby realizing the controllable processing of chitosan / cellulose acetate electrospun nanofibers, and solving the difficult problem of electrospinning membrane formation of chitosan and cellulose acetate.
[0006] The present invention is achieved through the following technical solutions:
[0007] A method for preparing a chitosan / cellulose acetate nanofiber membrane comprises electrostatic spinning of a chitosan / cellulose acetate mixed solution in a ternary solvent system, specifically comprising: first dissolving chitosan / cellulose acetate in a trifluoroacetic acid solvent, then adding a lactic acid solvent and a dichloromethane solvent to prepare a chitosan / cellulose acetate electrostatic spinning solution, and then electrostatic spinning the chitosan / cellulose acetate electrostatic spinning solution to obtain the membrane, wherein the volume ratio of the trifluoroacetic acid solvent, the lactic acid solvent, and the dichloromethane solvent is 3-4:1-2:5-6.
[0008] The volume ratio of trifluoroacetic acid solvent, lactic acid solvent and dichloromethane solvent is 3:1:6.
[0009] During electrospinning, the flow rate of the spinning solution was set to 1.0-1.2 mL / h and the applied voltage was 20-24 kV.
[0010] During electrospinning, the distance from the needle tip to the receiver was 7-8 cm, and the spinning time lasted 6-7 h.
[0011] The amount of chitosan added to cellulose acetate is 1% to 4% by mass.
[0012] The chitosan / cellulose acetate nanofiber membrane is prepared by the aforementioned chitosan / cellulose acetate nanofiber membrane preparation method.
[0013] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0014] This study screened a ternary solvent system with specific components and proportions, and achieved controllable processing of biocompatible chitosan / cellulose acetate nanofibers through co-dissolution and electrospinning. The resulting three-dimensional reticulated chitosan / cellulose acetate nanofiber membrane was used for hemoperfusion, specifically adsorbing and removing endotoxins. The cationic groups of CS and the three-dimensional pore structure of the CA matrix synergize to form a dual mechanism of "electrostatic adsorption + physical entrapment," enhancing endotoxin clearance and ultimately achieving high biocompatibility and efficient endotoxin adsorption for the chitosan / cellulose acetate nanofiber membrane. DETAILED DESCRIPTION
[0015] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples. The illustrative embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.
[0016] Endotoxin concentrations were measured using an endotoxin detection kit and a multifunctional microplate reader. Endotoxin adsorption and clearance rates were calculated based on the change in endotoxin concentration before and after adsorption, the solution volume, and the membrane mass to characterize the endotoxin adsorption properties of the CS / CA nanofiber membrane. Greater endotoxin adsorption and clearance rates within a specific timeframe (3 hours) indicate superior membrane adsorption. During hemoperfusion, red blood cell rupture (hemolysis) can cause adverse effects such as thrombosis, inflammation, and organ damage. Therefore, materials used in hemoperfusion must exhibit excellent biocompatibility to ensure they do not cause adverse reactions in patients during blood contact. According to ASTM F-756-08, materials with a hemolysis rate of less than 5% are considered non-toxic. The activated partial thromboplastin time (APTT) measures the time required for fibrin clot formation after the addition of the partial thromboplastin reagent and CaCl2 to initiate coagulation. APTT is often used to evaluate intrinsic and common coagulation pathways. Here, hemolysis rate and APTT are used to evaluate the biocompatibility and blood compatibility of CS / CA nanofiber membranes. The smaller the hemolysis rate and the larger the APTT, the better the blood compatibility and biocompatibility of the membrane.
[0017] Example 1
[0018] (1) 5 g of CA and 0.05 g of CS were placed in 12 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 8 mL of lactic acid (LA) and 20 mL of dichloromethane (DCM) solvent were added respectively and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0019] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 20 kV, a needle tip-to-receiver distance of 8 cm, and a spinning time of 7 h. After spinning, the membrane sample was removed and dried at room temperature to remove any remaining solvent, resulting in a CS / CA nanofiber membrane 1.
[0020] The endotoxin adsorption capacity of membrane 1 was 309 EU / g, the endotoxin clearance rate was 39%, the hemolysis rate was 0.7%, and the activated partial thromboplastin time (APTT) was 26 s.
[0021] CS / CA nanofiber membrane 1 has a larger endotoxin adsorption capacity and clearance rate, a lower hemolysis rate, and a prolonged activated partial thromboplastin time.
[0022] Example 2
[0023] (1) 5 g of CA and 0.1 g of CS were placed in 16 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 4 mL of lactic acid (LA) and 20 mL of dichloromethane (DCM) solvent were added respectively and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0024] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 22 kV, a needle tip-to-receiver distance of 8 cm, and a spinning time of 7 h. After spinning, the membrane sample was removed and dried at room temperature to remove any remaining solvent, resulting in CS / CA nanofiber membrane 2.
[0025] The endotoxin adsorption capacity of membrane 2 was 401 EU / g, the endotoxin clearance rate was 42%, the hemolysis rate was 0.6%, and the activated partial thromboplastin time (APTT) was 27 s.
[0026] As the CS content increased, the proportion of TFA solvent in the ternary solvent system increased, and the proportion of LA solvent decreased, the endotoxin adsorption capacity and clearance rate of CS / CA nanofiber membrane 2 were significantly improved, the hemolysis rate was further reduced, and the activated partial thromboplastin time was prolonged.
[0027] Example 3
[0028] (1) 5 g of CA and 0.1 g of CS were placed in 12 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 4 mL of lactic acid (LA) and 24 mL of dichloromethane (DCM) solvent were added respectively and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0029] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 22 kV, a needle tip-to-receiver distance of 8 cm, and a spinning time of 7 h. After spinning, the membrane sample was removed and dried at room temperature to remove any remaining solvent, resulting in a CS / CA nanofiber membrane 3.
[0030] The endotoxin adsorption capacity of membrane 3 was 427 EU / g, the endotoxin clearance rate was 47%, the hemolysis rate was 0.6%, and the activated partial thromboplastin time (APTT) was 28 s.
[0031] As the CS content increased, the proportion of DCM solvent in the ternary solvent system increased, and the proportion of LA solvent decreased, the endotoxin adsorption capacity and clearance rate of CS / CA nanofiber membrane 3 were further improved, the hemolysis rate was further reduced, and the activated partial thromboplastin time was further prolonged.
[0032] Example 4
[0033] (1) 5 g of CA and 0.2 g of CS were placed in 12 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 4 mL of lactic acid (LA) and 24 mL of dichloromethane (DCM) solvent were added respectively and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0034] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 24 kV, a needle tip-to-receiver distance of 8 cm, and a spinning time of 7 h. After spinning, the membrane sample was removed and dried at room temperature to remove any remaining solvent, resulting in a CS / CA nanofiber membrane 4.
[0035] The endotoxin adsorption capacity of membrane 4 was 618 EU / g, the endotoxin clearance rate was 66%, the hemolysis rate was 0.5%, and the activated partial thromboplastin time (APTT) was 30 s.
[0036] As the CS content further increased and the composition ratio of the ternary solvent system remained unchanged, when the volume ratio of TFA, LA and DCM was 3:1:6, the endotoxin adsorption capacity and clearance rate of CS / CA nanofiber membrane 4 continued to increase, the hemolysis rate further decreased, and the activated partial thromboplastin time was further prolonged.
[0037] Example 5
[0038] (1) 5 g of CA and 0.25 g of CS were placed in 12 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 4 mL of lactic acid (LA) and 24 mL of dichloromethane (DCM) solvent were added respectively and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0039] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 24 kV, and an 8 cm distance between the needle tip and the receiver. The fibers began to bead, and a complete nanofiber membrane could not be formed.
[0040] Electrospinning of CS / CA blends requires a balance between solution viscosity, conductivity, and solvent evaporation rate. While maintaining the same composition ratio in the ternary solvent system, when the CS content reaches 5%, the balance is disrupted, and spinnability deteriorates. Therefore, the upper limit of the CS relative to CA content is set at 4%.
[0041] Comparative Example 1
[0042] (1) 5 g of CA was placed in 12 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 4 mL of lactic acid (LA) and 24 mL of dichloromethane (DCM) solvent were added respectively and stirred at room temperature for 24 h to obtain a CA electrospinning solution.
[0043] (2) The CA solution was placed in an electrospinning apparatus with a flow rate of 1.0 mL / h, an applied voltage of 20 kV, a distance from the needle tip to the receiver of 8 cm, and a spinning time of 7 h. After spinning, the membrane sample was removed and dried at room temperature to remove the remaining solvent, resulting in a pure CA nanofiber membrane 6.
[0044] The endotoxin adsorption capacity of membrane 6 was 89 EU / g, the endotoxin clearance rate was 12%, the hemolysis rate was 1.1%, and the activated partial thromboplastin time (APTT) was 25 s.
[0045] Pure CA nanofiber membrane 6 has lower endotoxin adsorption and clearance rate, higher hemolysis rate, and shorter activated partial thromboplastin time.
[0046] Comparative Example 2
[0047] (1) 5 g of CS was placed in 12 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 4 mL of lactic acid (LA) and 24 mL of dichloromethane (DCM) solvent were added respectively and stirred at room temperature for 24 h to obtain the CS electrospinning solution.
[0048] (2) The CS solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 24 kV, and a distance from the needle tip to the receiver of 8 cm. No CS nanofibers were produced.
[0049] Pure CS solution cannot form nanofibrous membranes due to its high surface tension and poor spinnability.
[0050] Comparative Example 3
[0051] (1) 5 g of CA and 0.05 g of CS were placed in 12 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 12 mL of lactic acid (LA) and 12 mL of dichloromethane (DCM) solvent were added respectively and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0052] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 20 kV, and a distance from the needle tip to the receiver of 8 cm. Continuous nanofibers could not be formed, and a complete CS / CA nanofiber membrane could not be obtained.
[0053] Electrospinning of CS / CA mixed solutions requires a balance between solution viscosity, conductivity, and solvent evaporation rate. When the volume ratio of TFA, LA, and DCM in the ternary solvent system is 1:1:1, an effective spinning solution system cannot be formed.
[0054] Comparative Example 4
[0055] (1) 5 g of CA and 0.05 g of CS were placed in 24 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 4 mL of lactic acid (LA) and 12 mL of dichloromethane (DCM) solvent were added respectively and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0056] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 20 kV, and a distance from the needle tip to the receiver of 8 cm. Continuous nanofibers could not be formed, and a complete CS / CA nanofiber membrane could not be obtained.
[0057] Electrospinning of CS / CA mixed solutions requires a balance between solution viscosity, conductivity, and solvent evaporation rate. When the volume ratio of TFA, LA, and DCM in the ternary solvent system is 6:1:3, an effective spinning solution system cannot be formed.
[0058] Comparative Example 5
[0059] (1) 5 g of CA and 0.05 g of CS were placed in 12 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 12 mL of dichloromethane (DCM) solvent was added and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0060] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 20 kV, and a distance from the needle tip to the receiver of 8 cm. Continuous nanofibers could not be formed, and a complete CS / CA nanofiber membrane could not be obtained.
[0061] Electrospinning of CS / CA mixed solutions requires a balance between solution viscosity, conductivity, and solvent evaporation rate. Using only the solvents TFA and DCM does not result in an effective spinning solution system.
[0062] Comparative Example 6
[0063] (1) 5 g of CA and 0.05 g of CS were placed in 12 mL of trifluoroacetic acid (TFA) and stirred at 40 °C until dissolved. After cooling to room temperature, 12 mL of lactic acid (LA) solvent was added and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0064] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 20 kV, and a distance from the needle tip to the receiver of 8 cm. Continuous nanofibers could not be formed, and a complete CS / CA nanofiber membrane could not be obtained.
[0065] Electrospinning of CS / CA mixed solutions requires a balance between solution viscosity, conductivity, and solvent evaporation rate. Using only the solvents TFA and LA does not result in an effective spinning solution system.
[0066] Comparative Example 7
[0067] (1) 5 g of CA and 0.05 g of CS were placed in 12 mL of dichloromethane (DCM) and stirred at 40 °C until dissolved. After cooling to room temperature, 12 mL of lactic acid (LA) was added and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0068] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 20 kV, and a distance from the needle tip to the receiver of 8 cm. Continuous nanofibers could not be formed, and a complete CS / CA nanofiber membrane could not be obtained.
[0069] Electrospinning of CS / CA mixed solutions requires a balance between solution viscosity, conductivity, and solvent evaporation rate. When only LA and DCM are present, an effective spinning solution system cannot be formed.
[0070] Comparative Example 8
[0071] (1) 5 g of CA and 0.05 g of CS were placed in 12 mL of ionic liquid (1-ethyl-3-methylimidazolium acetate, EMIMAc) and stirred at 40 °C until dissolved. After cooling to room temperature, 4 mL of N,N-dimethylformamide (DMF) and 24 mL of acetic acid (HAc) were added and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0072] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 20 kV, and a distance from the needle tip to the receiver of 8 cm. Continuous nanofibers could not be formed, and a complete CS / CA nanofiber membrane could not be obtained.
[0073] Electrospinning of CS / CA mixed solutions requires a balance between solution viscosity, conductivity, and solvent evaporation rate. When the ternary solvent system composition is EMIMAc:DMF:HAc=3:1:6, an effective spinning solution system cannot be formed.
[0074] Comparative Example 9
[0075] (1) 5 g of CA and 0.05 g of CS were placed in 12 mL of acetone (DMK) and stirred at 40 °C until dissolved. After cooling to room temperature, 4 mL of formic acid (FA) and 24 mL of N,N-dimethylacetamide (DMAc) were added and stirred at room temperature for 24 h to obtain the CS / CA electrospinning solution.
[0076] (2) The CS / CA mixed solution was placed in an electrospinning apparatus with a dope flow rate of 1.0 mL / h, an applied voltage of 20 kV, and a distance from the needle tip to the receiver of 8 cm. Continuous nanofibers could not be formed, and a complete CS / CA nanofiber membrane could not be obtained.
[0077] Electrospinning of CS / CA mixed solutions requires a balance between solution viscosity, conductivity, and solvent evaporation rate. When the ternary solvent system composition is DMK:FA:DMAc = 3:1:6, an effective spinning solution system cannot be formed.
[0078] Table 1 Comparison of chitosan / cellulose acetate nanofiber membrane composition, solvent ratio and adsorption performance
[0079]
[0080]
[0081] Comparative Example 1 shows that pure CA nanofiber membranes exhibit low endotoxin adsorption and clearance rates, a high hemolysis rate, and a short APTT. Comparative Example 2 demonstrates that pure CS solution exhibits poor spinnability and cannot form fiber membranes on its own. Examples 1-4 and Comparative Examples 3-9 demonstrate that only ternary solvent systems with specific components and composition ratios can achieve electrospinning of chitosan / cellulose acetate mixed solutions and form nanofiber membranes, while binary solvents, other ternary solvent systems, and ternary solvent compositions outside the aforementioned volume ratios cannot electrospin into membranes. The addition of an appropriate amount of CS to CA allows the cationic groups of CS to synergize with the three-dimensional pore structure of the CA matrix, forming a dual mechanism of "electrostatic adsorption + physical entrapment," significantly enhancing the endotoxin adsorption performance of the nanofiber membrane and improving its biocompatibility and hemocompatibility. Only ternary solvent systems with specific compositions can achieve a balance between the viscosity, conductivity, and solvent evaporation rate of the CS / CA mixed solution, thereby enabling the controllable processing of chitosan / cellulose acetate electrospun nanofibers.
[0082] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.
Claims
1. A method for preparing a chitosan / cellulose acetate nanofiber membrane, characterized in that: In a ternary solvent system, a chitosan / cellulose acetate mixed solution is electrospun, specifically: chitosan / cellulose acetate is first dissolved in a trifluoroacetic acid solvent, and then a lactic acid solvent and a dichloromethane solvent are added to prepare a chitosan / cellulose acetate electrospinning solution, and the chitosan / cellulose acetate electrospinning solution is electrospun to obtain the obtained product, wherein the volume ratio of the trifluoroacetic acid solvent, the lactic acid solvent and the dichloromethane solvent is 3-4:1-2:5-6.
2. The preparation method according to claim 1, characterized in that The volume ratio of trifluoroacetic acid solvent, lactic acid solvent and dichloromethane solvent is 3:1:
6.
3. The preparation method according to claim 1, characterized in that During electrospinning, the flow rate of the spinning solution was set to 1.0-1.2 mL / h and the applied voltage was 20-24 kV.
4. The preparation method according to claim 1, characterized in that During electrospinning, the distance from the needle tip to the receiver was 7-8 cm, and the spinning time lasted 6-7 h.
5. The preparation method according to claim 1, characterized in that The amount of chitosan added to cellulose acetate is 1% to 4% by mass.
6. A chitosan / cellulose acetate nanofiber membrane prepared by the method for preparing a chitosan / cellulose acetate nanofiber membrane according to any one of claims 1 to 5.