A polyelectrolyte sponge dressing and a method of making the same

Abstract

The application discloses a kind of polyelectrolyte sponge dressings and preparation method thereof, belong to medical material field, method steps include, adjust polycation electrolyte solution and polyanion electrolyte solution pH and mix two, to make mixed solution not produce electrostatic interaction, mixed solution freeze-drying, obtain uncrosslinked sponge, with acetic acid or ammonia water fumigation uncrosslinked sponge, obtain polyelectrolyte sponge dressing.The application does not need to carry out complex chemical modification, does not add any crosslinking agent, toxic covalent crosslinking monomer, prepared sponge dressing has higher liquid absorption rate, liquid retention rate while, still can keep pore structure after swelling, will not completely become gel, thus has better mechanical property, and can repeatedly drain liquid absorption, raw material used not only includes can form gel polyanion polycation electrolyte, for the polyanion polycation electrolyte that can not form gel is also applicable, good universality.

Description

Technical Field

[0001] This invention relates to a polyelectrolyte sponge dressing and its preparation method, belonging to the field of medical materials. Background Technology

[0002] Sponge dressings have numerous pores, which facilitates air permeability and water vapor evaporation; they also have a high specific surface area, which helps absorb wound exudate and stop bleeding; and they possess excellent elasticity, which helps protect skin wounds and makes them relatively durable. Due to these superior structural properties, sponges show great promise in accelerating wound healing.

[0003] Biomacromolecules refer to large molecules such as proteins, nucleic acids, and polysaccharides found within the cells of living organisms. Due to their excellent biocompatibility and biodegradability, they are commonly used in biomedical materials. Sponges made from collagen or gelatin have poor mechanical properties and are expensive, limiting their applications. Chitosan is the only positively charged biomacromolecule polysaccharide found in nature. It possesses cationic polyelectrolyte properties, multifunctional reactive groups, antibacterial properties, and hemostatic properties. It is easily extracted from crustaceans, chondrocytes, and fungi, and is inexpensive, thus it is frequently used in various biomedical materials.

[0004] The conventional preparation method for chitosan-based polyelectrolyte sponges is as follows: a solution of chitosan-based polycationic electrolyte and polyanionic electrolyte is prepared, the pH value of the mixed solution is adjusted, and the positively charged cationic groups and negatively charged anionic groups are combined through electrostatic interaction to form a gel with a certain network structure (i.e., Sol-gel process) by utilizing the ionic interaction between the chitosan-based polycationic electrolyte and polyanionic electrolyte. The gel is then freeze-dried to obtain a sponge with a certain pore structure.

[0005] However, during freezing, the water inside the gel expands in volume during crystallization, which to some extent disrupts the internal network structure. During use, the water absorption process of the chitosan-based polyelectrolyte sponge is uncontrolled; the pore walls formed during freeze-drying swell to fill the voids left by freeze-drying and revert to a gel state. These two effects result in poor mechanical properties of the chitosan-based polyelectrolyte sponge, making it difficult to form a robust physical barrier in large-area wounds, which greatly limits its application in hemostasis and wound healing. To improve the mechanical properties of chitosan-based polyelectrolyte sponges, some studies have introduced covalent cross-linking to form a double-network structure; however, introducing covalent cross-linking inevitably results in the presence of cytotoxic cross-linking agents and organic solvent residues.

[0006] In addition, chitosan-based polycationic electrolytes have strong electrostatic interactions with various polyanionic electrolytes, and when mixed, they are prone to liquid-liquid phase separation or the formation of solid polyelectrolyte precipitates, rather than gels with a uniform network structure. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention provides a polyelectrolyte sponge dressing and its preparation method, which can produce a polyelectrolyte sponge dressing with good mechanical properties without covalent crosslinking, and is also applicable to polyanionic and cationic electrolytes that cannot form gels.

[0008] The technical solution adopted by this invention to solve its technical problem is:

[0009] In a first aspect, this application provides a method for preparing a polyelectrolyte sponge dressing, comprising the following steps:

[0010] The pH of the polycationic electrolyte solution and the polyanionic electrolyte solution are adjusted and mixed to ensure that the mixed solution does not generate electrostatic interactions.

[0011] The mixed solution was freeze-dried to obtain an uncrosslinked sponge;

[0012] The uncrosslinked sponge is fumigated with acetic acid or ammonia to obtain the polyelectrolyte sponge dressing.

[0013] The preparation method of the polyelectrolyte sponge dressing provided in this application first adjusts the pH to simultaneously protonate or deprotonate the polycationic electrolyte solution and the polyanionic electrolyte solution. After mixing, no electrostatic interaction occurs, forming a homogeneous and stable mixed solution. The solute is a polyelectrolyte complex. During freezing, the polyelectrolyte does not form electrostatic complexes, and the polyelectrolyte complex solution without a network structure does not restrict the growth of ice crystals. During drying, large and interconnected primary pores formed by the sublimation of ice crystals are left. During fumigation, the anion and cation groups in the polyelectrolyte complex are charged by the gas-solid interface reaction. Through hydrogen bonding and electrostatic interaction, small and dense secondary pore structures are formed at the pore walls of the primary pores. The secondary pore structure has a certain constraint effect on the pore walls of the primary pores, preventing the sponge dressing from completely filling the primary pores during swelling. This helps to fix the morphology of the primary pores and prevents the sponge dressing from completely swelling into a gel. This multi-level pore structure can greatly improve the mechanical properties of the polyelectrolyte sponge while maintaining high liquid absorption and retention capacity. Moreover, this application involves cryogenic casting of a homogeneous mixed solution, which has very low requirements for the interaction between polyanionic electrolytes and polycationic electrolytes in the solution. This eliminates the limitation of conventional methods (Sol-gel Process) which require the formation of a uniform gel in solution, and has good versatility.

[0014] Furthermore, the polycationic electrolyte solution is an aqueous solution with a mass fraction of 1%-10%, and the polyanionic electrolyte solution is an aqueous solution with a mass fraction of 1%-10%. This application utilizes secondary pores to constrain the swelling degree of the sponge, allowing the sponge to retain strong mechanical properties after absorbing water. Controlling the solid content is one means of adjusting this constraining ability. However, if the solid content is too high, the constraint on the swelling degree will be too great, reducing porosity and water absorption ratio. Therefore, the mass fraction of both the polycationic electrolyte solution and the polyanionic electrolyte solution should preferably be below 10%.

[0015] Furthermore, the volume ratio of the polycationic electrolyte solution to the polyanionic electrolyte solution is 5:1 to 1:3.

[0016] Furthermore, the solute in the polycationic electrolyte solution is selected from chitosan, carboxymethyl chitosan, or quaternary ammonium salt chitosan.

[0017] Furthermore, the solute in the polyanionic electrolyte solution is selected from polyacrylic acid, sodium hyaluronate, sodium carboxymethyl cellulose, sodium alginate, fucoidan, chondroitin sulfate, pectin, or carrageenan.

[0018] For example, carboxymethyl chitosan solution and sodium alginate can be mixed using conventional methods to prepare a gel and then freeze-dried into a sponge. However, since carboxymethyl chitosan solution and sodium hyaluronate solution have strong electrostatic interactions, liquid-liquid phase separation will occur after mixing at a certain pH, forming flocculent precipitates instead of a gel. Therefore, it is difficult to make a sponge using conventional methods. However, the present invention does not require the formation of a gel in the solution, but achieves electrostatic complexation through gas-solid interface reaction. Therefore, carboxymethyl chitosan and sodium hyaluronate can be made into a polyelectrolyte sponge, which has better versatility.

[0019] Furthermore, in the freeze-drying step, the freezing temperature is -20℃ to -80℃. Adjusting the freezing temperature is an important means of regulating the freezing rate. A certain freezing rate can cause the ice solidification front to repel the solute, allowing polycationic electrolytes and polyanionic electrolytes to accumulate at the grain boundaries, which is beneficial for forming dense pore walls. During fumigation, high-concentration electrostatic complexing can occur in the microphase formed by the trace amount of moisture remaining after freeze-drying in the pore walls, making the mechanical properties of the sponge stronger. If the freezing rate is too fast, the pore walls will not be dense enough, affecting the morphology and strength of the primary pores.

[0020] Furthermore, in the freeze-drying step, the freezing time is 4h to 24h to achieve Ostwald ripening of the ice crystals.

[0021] Furthermore, after the step of fumigating the uncrosslinked sponge with acetic acid or ammonia, the method further includes the step of displacing residual gas in the polyelectrolyte sponge dressing in an environment of 35°C-42°C.

[0022] The purpose of this step is to replace (e.g., with air) any residual ammonia or acetic acid vapor in the sponge, making the sponge as close to neutral as possible when applied to the wound. A temperature of around 40°C is beneficial for improving replacement efficiency and avoids excessively high temperatures that could cause the polysaccharides in the natural polyelectrolytes to brown.

[0023] Furthermore, the step of fumigating the uncrosslinked sponge with acetic acid or ammonia water includes: fumigating the uncrosslinked sponge with acetic acid or ammonia water at room temperature for 1 hour to 20 hours.

[0024] Secondly, this application provides a polyelectrolyte sponge dressing, made by the preparation method of the polyelectrolyte sponge dressing described in the first aspect, having primary pores left by ice crystals and small and dense secondary pores that constrain the pore walls of the primary pores, so that the polyelectrolyte sponge dressing still has strong mechanical strength after absorbing water, and there is no need to introduce covalent cross-linking components.

[0025] The beneficial effects of this invention are: this invention does not require complex chemical modification, does not add any crosslinking agents or toxic covalent crosslinking monomers, and the resulting sponge dressing has a high liquid absorption rate and liquid retention rate. After swelling, it can still maintain the pore structure and will not completely turn into a gel. Therefore, it has better mechanical properties and can be repeatedly drained and absorbed. The raw materials used include not only polyanionic and cationic electrolytes that can form gels, but also polyanionic and cationic electrolytes that cannot form gels, which has good versatility.

[0026] Other features and advantages of this application will be set forth in the following description and will be apparent in part from the description or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0027] Figure 1 This is a comparison of the morphology of the sponge dressings prepared in Example 1 and Comparative Example 1 under different conditions.

[0028] Figure 2 This is a comparison of the morphology of Comparative Example 2 and Example 9 after fumigation at room temperature.

[0029] Figure 3 This is a comparison of the compressibility of the sponge dressings prepared in Example 1 and Comparative Example 1 after absorbing water.

[0030] Figure 4 This is an electron microscope image of the sponge dressing prepared in Example 5.

[0031] Figure 5 These are the infrared spectra of carboxymethyl chitosan, sodium alginate, Comparative Example 1, and Example 1. Detailed Implementation

[0032] The conventional method for preparing sponge dressings involves first mixing polycationic electrolytes and polyanionic electrolytes, adjusting the pH to form a gel, and then freeze-drying the gel to obtain the sponge dressing. This method has the following problems:

[0033] (1) During the freezing process, the growth of ice crystals will destroy part of the electrostatic cross-linking network, making it difficult for the hydrogel to maintain the network structure before freezing;

[0034] (2) The network structure formed by electrostatic interactions in the gel will hinder the growth of ice crystals, resulting in the inability to form large and interconnected pore structures;

[0035] (3) After the sponge dressing is saturated with water, it will fill the freeze-dried pores, causing the pores to close and return to a fragile gel. It is essentially a concentrated solution system with poor fluidity and cannot be air-dried to drain and form pores again.

[0036] (4) If a covalent cross-linked network is introduced to improve strength, it will have disadvantages such as high cytotoxicity, poor biocompatibility and slow degradation in vivo.

[0037] Therefore, the present invention provides a method for preparing a polyelectrolyte sponge dressing, comprising the following steps:

[0038] S1: Adjust the pH of the polycationic electrolyte solution and the polyanionic electrolyte solution and mix them to ensure that the mixed solution does not generate electrostatic interactions. Prior to this step, the preparation of the polycationic electrolyte solution and the polyanionic electrolyte solution may include operations such as dissolution and dilution. The purpose of adjusting the pH is to simultaneously protonate or deprotonate the polycationic electrolyte solution and the polyanionic electrolyte solution, so that no electrostatic interactions occur after mixing, forming a stable mixed solution with the polyelectrolyte complex as the solute.

[0039] S2: Freeze-dry the mixed solution to obtain an uncrosslinked sponge. During freezing, the polyelectrolytes do not undergo electrostatic complexation, and the polyelectrolyte complex solution without a network structure does not restrict ice crystal growth. Upon drying, large, interconnected primary pores formed by ice crystal sublimation remain. This step involves freeze-drying the solution, not the gel, therefore requiring minimal interaction between the polyanionic and polycationic electrolytes in the solution of step S1, resulting in good versatility.

[0040] S3: Uncrosslinked sponge is fumigated with acetic acid or ammonia to obtain a polyelectrolyte sponge dressing. During fumigation, the gas-solid interface reaction causes the anionic and cationic groups in the polyelectrolyte complex to become charged, forming hydrogen bonds and electrostatic interactions. This creates small and dense secondary pore structures at the walls of the primary pores. The secondary pore structures constrain the walls of the primary pores, preventing the sponge dressing from completely filling the primary pores during swelling. This helps to fix the morphology of the primary pores. Therefore, the sponge dressing prepared by this invention can repeatedly absorb and drain liquid, continuously retaining its porous morphology without completely turning into a gel. Thus, it can have higher mechanical strength without covalent crosslinking.

[0041] This invention pre-fixes the morphology of the macropores (primary pores) using large ice crystals, and introduces strong hydrogen bonds and electrostatic interactions within the dense pore walls of the primary macropores. Therefore, although the pore walls tend to swell after absorbing liquid, these two interactions limit the degree of swelling, keeping it controlled. As a result, the pore walls retain a network structure after swelling and do not completely transform into a gel, thus exhibiting strong mechanical strength and allowing for repeated liquid absorption and drainage. During fumigation, acetic acid (or ammonia) vapor is adsorbed into the pore walls of the sponge. A portion of the vapor reacts with trace amounts of moisture in the pore walls, dissociating into H+. + (or OH) - The presence of ions creates an acidic (or alkaline) environment on the pore walls of the sponge, causing the cations and anions to become charged and generate electrostatic interactions. Another portion of the vapor interacts with the polyelectrolyte at the pore walls through hydrogen bonding, further enhancing the sponge's mechanical properties. In use, the unabsorbed sponge is cut into a specific shape and applied to the wound; it quickly absorbs blood, forming a strong protective layer.

[0042] Example 1

[0043] Carboxymethyl chitosan was dissolved in deionized water to prepare a 1% (w / w) solution. Sodium alginate was dissolved in deionized water to prepare a 1% (w / w) solution with a pH > 7. The two solutions were then mixed at a 1:1 volume ratio to form a homogeneous solution with a pH > 7. The solution was poured into a mold and frozen at -20°C for 24 hours, followed by vacuum drying. The dried sponge was placed in a desiccator containing acetic acid and fumigated at room temperature for 4 hours. After removal, it was treated in a 37°C oven for 1 hour to obtain the polyelectrolyte sponge dressing.

[0044] Example 2

[0045] Carboxymethyl chitosan was dissolved in deionized water to prepare a 1% (w / w) solution. Sodium alginate was dissolved in deionized water to prepare a 1% (w / w) solution with a pH > 7. The two solutions were then mixed at a 1:2 volume ratio to form a homogeneous solution with a pH > 7. The solution was poured into a mold and frozen at -80°C for 24 hours, followed by vacuum drying. The dried sponge was placed in a desiccator containing acetic acid and fumigated at room temperature for 12 hours. After removal, it was treated in a 37°C oven for 1 hour to obtain the polyelectrolyte sponge dressing.

[0046] Example 3

[0047] Carboxymethyl chitosan was dissolved in deionized water to prepare a 1% (w / w) solution with a pH > 7. Sodium alginate was dissolved in deionized water to prepare a 1% (w / w) solution. The two solutions were then mixed at a volume ratio of 3:1 to form a homogeneous solution with a pH > 7. The solution was poured into a mold and frozen at -80°C for 12 hours, followed by vacuum drying. The dried sponge was placed in a desiccator containing acetic acid and fumigated at room temperature for 12 hours. After removal, it was treated in a 37°C oven for 0.5 hours to obtain the polyelectrolyte sponge dressing.

[0048] Example 4

[0049] Carboxymethyl chitosan was dissolved in deionized water to prepare a 1% (w / w) solution with a pH > 7. Sodium alginate was dissolved in deionized water to prepare a 1% (w / w) solution. The two solutions were then mixed at a 2:1 volume ratio to form a homogeneous solution with a pH > 7. The solution was poured into a mold and frozen at -20°C for 24 hours, followed by vacuum drying. The dried sponge was placed in a desiccator containing acetic acid and fumigated at room temperature for 8 hours. After removal, it was treated in a 37°C oven for 0.5 hours to obtain the polyelectrolyte sponge dressing.

[0050] Example 5

[0051] Carboxymethyl chitosan was dissolved in deionized water to prepare a 2% (w / w) solution with a pH > 7. Sodium alginate was dissolved in deionized water to prepare a 2% (w / w) solution. The two solutions were then mixed at a 1:1 volume ratio to form a homogeneous solution with a pH > 7. The solution was poured into a mold and frozen at -20°C for 24 hours, followed by vacuum drying. The dried sponge was placed in a desiccator containing acetic acid and fumigated at room temperature for 8 hours. After removal, it was treated in a 37°C oven for 2 hours to obtain the polyelectrolyte sponge dressing.

[0052] Example 6

[0053] Chitosan was dissolved in 0.5 mol / L hydrochloric acid to prepare a 10% (w / w) solution with a pH < 7. A 25% polyacrylic acid solution was diluted to 10% with deionized water, and then the two solutions were mixed at a 1:1 volume ratio to form a homogeneous solution with a pH < 7. The solution was poured into a mold and frozen at -80°C for 24 hours, followed by vacuum drying. The dried sponge was placed in a desiccator containing ammonia and fumigated at room temperature for 8 hours. After removal, it was treated in a 37°C oven for 1 hour to obtain the polyelectrolyte sponge dressing.

[0054] Example 7

[0055] Chitosan was dissolved in 0.5 mol / L hydrochloric acid to prepare a 10% (w / w) solution with a pH < 7. A 25% polyacrylic acid solution was diluted to 10% with deionized water, and then the two solutions were blended at a volume ratio of 3:5 to form a homogeneous solution with a pH < 7. The solution was poured into a mold and frozen at -20°C for 24 hours, followed by vacuum drying. The dried sponge was placed in a desiccator containing ammonia and fumigated at room temperature for 16 hours. After removal, it was treated in a 37°C oven for 2 hours to obtain the polyelectrolyte sponge dressing.

[0056] Example 8

[0057] Chitosan was dissolved in 0.5 mol / L hydrochloric acid to prepare a 5% (w / w) solution with a pH < 7. A 25% polyacrylic acid solution was diluted with deionized water to 5%, and then the two solutions were mixed at a volume ratio of 5:3 to form a homogeneous solution with a pH < 7. The solution was poured into a mold and frozen at -20°C for 24 hours, followed by vacuum drying. The dried sponge was placed in a desiccator containing ammonia and fumigated at room temperature for 16 hours. After removal, it was treated in a 37°C oven for 3 hours to obtain the polyelectrolyte sponge dressing.

[0058] Example 9

[0059] Carboxymethyl chitosan was dissolved in deionized water to prepare a 2% (w / w) solution with a pH < 7. Sodium hyaluronate was dissolved in deionized water to prepare a 2% (w / w) solution. The two solutions were then mixed at a 1:1 volume ratio to form a homogeneous solution with a pH > 7. The solution was poured into a mold and frozen at -20°C for 4 hours, followed by vacuum drying. The dried sponge was placed in a desiccator containing acetic acid and fumigated at room temperature for 4 hours. After removal, it was treated in a 37°C oven for 0.5 hours to obtain the polyelectrolyte sponge dressing.

[0060] Example 10

[0061] Carboxymethyl chitosan was dissolved in deionized water to prepare a 1% (w / w) solution with a pH < 7. Sodium hyaluronate was dissolved in deionized water to prepare a 1% (w / w) solution. The two solutions were then mixed at a volume ratio of 3:1 to form a homogeneous solution with a pH > 7. The solution was poured into a mold and frozen at -20°C for 18 hours, followed by vacuum drying. The dried sponge was placed in a desiccator containing acetic acid and fumigated at room temperature for 12 hours. After removal, it was treated in a 37°C oven for 1 hour to obtain the polyelectrolyte sponge dressing.

[0062] Comparative Example 1

[0063] Carboxymethyl chitosan was dissolved in deionized water to prepare a 1% (w / w) solution with a pH > 7. Sodium alginate was dissolved in deionized water to prepare a 1% (w / w) solution. The two solutions were then mixed at a 1:1 volume ratio to form a homogeneous solution with a pH > 7. The solution was poured into a mold and steamed at room temperature for 4 hours. After removal, it was treated in a 37°C oven for 1 hour, then frozen at -20°C for 24 hours, and finally vacuum dried. This yielded a chitosan-based polyelectrolyte sponge dressing prepared using conventional methods.

[0064] Comparative Example 2

[0065] Carboxymethyl chitosan was dissolved in deionized water to prepare a 2% (w / w) solution with a pH > 7. Sodium hyaluronate was dissolved in deionized water to prepare a 2% (w / w) solution. The two solutions were then mixed at a 1:1 volume ratio to form a homogeneous solution with a pH > 7. The solution was poured into a mold and fumigated at room temperature for 4 hours.

[0066] Figure 1 Point A in the diagram represents the polyelectrolyte sponge dressing prepared in Example 1. Figure 1 Point a in the diagram represents the polyelectrolyte sponge dressing prepared in Comparative Example 1. Comparing A and a, it can be seen that there is no significant difference between the two polyelectrolyte sponge dressings when they are not absorbent. The polyelectrolyte sponge dressing prepared in Example 1, after absorbing water, shows... Figure 1 As shown at point B, the polyelectrolyte sponge dressing prepared in Comparative Example 1 absorbs water as shown in Figure B. Figure 1 As shown at point b, both examples changed from white to translucent. Example 1 swelled with a clear boundary, while Comparative Example 1 swelled more strongly, had higher transparency, and its boundary with the water became less clear. The polyelectrolyte sponge dressing prepared in Example 1 stretched after absorbing water as shown... Figure 1 As shown at point C, the internal water can be squeezed out, restoring the opaque state. The polyelectrolyte sponge dressing prepared in Comparative Example 1 stretches after absorbing water as shown... Figure 1 As shown at point c, the gel breaks into fragmented blocks with high transparency. This confirms that the embodiments of this application can control the degree of swelling, preventing the sponge dressing from completely swelling into a gel, and exhibiting high mechanical strength, allowing for repeated absorption and drainage of liquid.

[0067] The compressibility of Example 1 (Freeze Casting) and Comparative Example 1 (Sol-gel Process) after water absorption was compared. The results are as follows: Figure 3 As shown, the sponge prepared by the method of the present invention has better compressive toughness. At a strain of about 60%, the sponge prepared by conventional methods, such as Comparative Example 1 (Sol-gel Process), exhibits obvious fracture behavior, while the sponge prepared by the method of the present invention (Freeze Casting) does not fracture even when the strain reaches 80%.

[0068] Infrared spectroscopy was performed on carboxymethyl chitosan (CMCS), sodium alginate (SA), Comparative Example 1 (Sol-gel Process), and Example 1 (Freeze Casting). The results are as follows: Figure 5 As shown, the carboxymethyl chitosan-sodium alginate polyelectrolyte sponge dressing exhibits the characteristic absorption peaks of both, at 1670 cm⁻¹. －1 ~1725cm －1 A strong absorption peak appears in the region, which is generated by the stretching vibration of acetic acid C=O associated with hydrogen bonds. No other new peaks appear, proving that the two are physically cross-linked gels. Furthermore, the intensities of the main peaks of the sponge dressing prepared using the method of this invention are significantly higher than those of the sponge dressing prepared by the conventional method in Comparative Example 1, demonstrating stronger intermolecular forces and thus better mechanical properties.

[0069] Comparative Example 2: After mixing carboxymethyl chitosan solution and sodium hyaluronate solution, as shown... Figure 2 As shown at point A, the solution is completely homogeneous. After fumigation at room temperature, as... Figure 2 As shown at point B, a polyelectrolyte precipitate formed, preventing further freeze-drying to form a sponge dressing. In contrast, Example 9 involved directly freeze-drying a mixture of carboxymethyl chitosan and sodium hyaluronate solutions before room temperature fumigation, eliminating the need for carboxymethyl chitosan and sodium hyaluronate to form a gel. The resulting sponge dressing was as shown... Figure 2 As shown at point C, a sponge dressing can be formed, and its appearance is not significantly different from the sponge dressings prepared in Example 1 and Comparative Example 1. This demonstrates that even a pair of polycationic electrolytes and polyanionic electrolytes that cannot form a stable gel can still be made into a sponge dressing using the method of the present invention.

[0070] Figure 4 The image shows a scanning electron microscope (SEM) image of the polyelectrolyte sponge dressing prepared in Example 5 after it has absorbed water. Figure 4 As can be seen, the sponge dressing has large pores, and the walls of the large pores are composed of many small pores, indicating that the surface of the sponge dressing prepared in the embodiments of this application has a multi-level pore structure, which has both a connected large pore structure and a fine small pore structure.

[0071] The method described in this application is simple, operates under mild conditions, and does not require covalent cross-linking. It overcomes the negative impact of water crystallization in the conventional preparation process of polyelectrolyte sponges, thus improving the mechanical properties of chitosan-based polyelectrolyte sponges. Specific mechanical properties and liquid absorption / retention properties can be controlled by adjusting the fumigation time and the polyelectrolyte ratio to meet the needs of wounds in different situations. Furthermore, the method of this invention can produce sponges from polyanionic and cationic electrolytes that cannot form gels, making it universally applicable.

[0072] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0073] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a polyelectrolyte sponge dressing, characterized in that, Includes the following steps: The pH is adjusted to simultaneously protonate or deprotonate the polycationic electrolyte solution and the polyanionic electrolyte solution, which are then mixed to obtain a mixed solution that does not generate electrostatic interactions. The mixed solution was freeze-dried to obtain an uncrosslinked sponge; The uncrosslinked sponge is fumigated with acetic acid or ammonia to obtain the polyelectrolyte sponge dressing; The polycationic electrolyte solution is an aqueous solution with a mass fraction of 1%-10%, and the polyanionic electrolyte solution is an aqueous solution with a mass fraction of 1%-10%. The solute in the polycationic electrolyte solution is selected from chitosan, carboxymethyl chitosan, or quaternary ammonium salt chitosan; The solute in the polyanionic electrolyte solution is selected from polyacrylic acid, sodium hyaluronate, sodium carboxymethyl cellulose, sodium alginate, fucoidan, chondroitin sulfate, pectin or carrageenan. In the freeze-drying step, the freezing temperature is -20℃ to -80℃, and the freezing time is 4h to 24h.

2. The method for preparing the polyelectrolyte sponge dressing according to claim 1, characterized in that, The volume ratio of the polycationic electrolyte solution to the polyanionic electrolyte solution is 5:1 to 1:

3.

3. The method for preparing the polyelectrolyte sponge dressing according to claim 1, characterized in that, Following the step of fumigating the uncrosslinked sponge with acetic acid or ammonia, the procedure further includes the step of displacing residual gas in the polyelectrolyte sponge dressing in an environment of 35°C-42°C to make the polyelectrolyte sponge dressing neutral when applied to the wound.

4. The method for preparing the polyelectrolyte sponge dressing according to claim 1, characterized in that, The step of fumigating the uncrosslinked sponge with acetic acid or ammonia water includes: fumigating the uncrosslinked sponge with acetic acid or ammonia water at room temperature for 1 hour to 20 hours.

5. A polyelectrolyte sponge dressing, characterized in that, It is made by the method for preparing polyelectrolyte sponge dressing according to any one of claims 1 to 4.

Images