Antibacterial and antioxidant lignin composite hydrogel as well as preparation method and application thereof

Abstract

The invention provides antibacterial and antioxidant lignin composite hydrogel as well as a preparation method and application thereof.The antibacterial and antioxidant lignin composite hydrogel is prepared by the steps that acrylamide and acrylic acid are subjected to a cross-linking reaction under the action of N, N-methylene bisacrylamide and an initiator, and a hydrogel matrix is formed; after sodium lignin sulfonate is introduced, hydrogel with an interpenetrating network structure is formed; after tannic acid and zinc chloride are introduced, the antibacterial and antioxidant lignin composite hydrogel which is complex and compact in structure is formed. The hydrogel has relatively strong oxidation resistance, antibacterial property and self-repairing property, can be used as a medical dressing, assists in repairing wounds and avoids inflammation of the wounds; meanwhile, the hydrogel can also be used as a cartilage tissue material, and self-repairing of the cartilage tissue can be achieved through the dynamic reversible coordination effect among zinc chloride, tannic acid and a hydrogel matrix.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and relates to an antibacterial and antioxidant lignin composite hydrogel, its preparation method, and its application. Background Technology

[0002] Lignin is a complex aromatic polymer found in plant cell walls and is the second largest biomass resource in nature after cellulose. Lignin possesses abundant hydroxyl and phenolic hydroxyl structures, which endow it with excellent chemical activity and biological functions.

[0003] In recent years, the development of medical materials, especially hydrogels, using lignin has become a research hotspot in the field of biomedical materials. Lignin-based hydrogels not only combine the biocompatibility and biodegradability of natural materials, but also have good hygroscopicity, breathability, antioxidant and antibacterial properties, which can promote wound healing and reduce the risk of infection. Therefore, they are widely used in wound dressings, controlled drug release, tissue engineering and other fields.

[0004] Currently, the main methods for preparing lignin hydrogels include physical crosslinking, chemical crosslinking, and polymer blending. Physical crosslinking primarily utilizes physical forces such as hydrogen bonds and hydrophobic interactions to construct a network structure. For example, by controlling conditions such as lignin concentration, pH, and temperature, lignin self-assembly can be induced to form a hydrogel. Physical crosslinking is simple to operate and avoids the use of chemical crosslinking agents, but the resulting gel has weaker mechanical properties and poorer stability. Chemical crosslinking involves introducing a crosslinking agent to react with the active functional groups of lignin, forming a covalently crosslinked network. Commonly used crosslinking agents include glutaraldehyde, polyethylene glycol diglycidyl ether, and polycarbonate glycol. However, although chemical crosslinking can significantly improve the mechanical properties and stability of hydrogels, crosslinking agents often have a certain degree of toxicity. Polymer blending involves blending lignin with other natural or synthetic polymers such as chitosan, sodium alginate, and polyvinyl alcohol, utilizing the interactions between them to form a composite hydrogel. This method can improve the properties of lignin hydrogels and endow them with new functions. However, due to the incompatibility between many polymers, phase separation can easily occur after mixing, leading to a decline in material properties and even phenomena such as delamination and cracking. Summary of the Invention

[0005] The purpose of this invention is to provide an antibacterial and antioxidant lignin composite hydrogel, its preparation method, and its application, in order to solve the problem of poor performance of lignin hydrogels in the prior art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, this application provides an antibacterial and antioxidant lignin composite hydrogel, the raw materials for which include acrylamide, acrylic acid, N,N-methylenebisacrylamide, initiator, sodium lignin sulfonate, tannic acid and zinc chloride.

[0007] Secondly, this application provides a method for preparing an antibacterial and antioxidant lignin composite hydrogel, comprising: Under a nitrogen atmosphere, acrylamide, acrylic acid, and N,N-methylenebisacrylamide undergo a polymerization reaction in the presence of an initiator to form a hydrogel matrix; A sodium lignosulfonate solution is slowly added to the hydrogel matrix to react and form a hydrogel with an interpenetrating network structure. After slowly adding tannic acid solution to the hydrogel, zinc chloride is added for cross-linking reaction to obtain lignin composite hydrogel.

[0008] Thirdly, this application provides an application of antibacterial and antioxidant lignin composite hydrogel in the preparation of medical dressings.

[0009] Fourthly, this application provides another application, namely the application of antibacterial and antioxidant lignin composite hydrogel in the preparation of cartilage tissue materials.

[0010] The present invention has the following beneficial effects: (1) In this application, acrylamide and acrylic acid undergo a cross-linking reaction under the action of N,N-methylenebisacrylamide and initiator to form a hydrogel matrix; after adding sodium lignosulfonate, while retaining its antibacterial and antioxidant properties, the hydroxyl and sulfonic acid groups in sodium lignosulfonate will undergo hydrogen bonding and electrostatic interaction with the hydroxyl and amine groups in the hydrogel matrix, and will also interpenetrate and entangle with the polymer molecular chains in the hydrogel matrix to form a hydrogel with an interpenetrating network structure, thereby improving the structural strength of the hydrogel.

[0011] (2) By introducing tannic acid and zinc chloride into a hydrogel with an interpenetrating network structure, the catechol structure of tannic acid forms a coordination effect with zinc chloride, and tannic acid also undergoes a cross-linking reaction with the carboxyl or amine groups in the hydrogel to form a complex and tightly structured antibacterial and antioxidant lignin composite hydrogel, thereby effectively dispersing stress, reducing defects caused by phase separation, and improving the antibacterial and antioxidant properties, mechanical stability and self-healing properties of the hydrogel.

[0012] (3) The antibacterial and antioxidant lignin composite hydrogel in this application has a mechanical strength of 1.3-1.7 MPa and also has strong antioxidant, antibacterial and self-healing properties.

[0013] (4) The antibacterial and antioxidant lignin composite hydrogel in this application can be used as a medical dressing to help repair wounds, prevent wound inflammation, and accelerate wound repair.

[0014] (5) When using the antibacterial and antioxidant lignin composite hydrogel in this application, the lignin composite hydrogel can be detached from the skin surface by dripping an acidic solution, and will not adhere to the skin surface.

[0015] (6) The antibacterial and antioxidant lignin composite hydrogel in this application can also be used as a cartilage tissue material. By utilizing the dynamic reversible coordination between zinc chloride, tannic acid and hydrogel matrix, the self-repair of cartilage tissue can be achieved. Detailed Implementation

[0016] This application provides an antibacterial and antioxidant lignin composite hydrogel, the raw materials for which include acrylamide, acrylic acid, N,N-methylenebisacrylamide, initiator, sodium lignin sulfonate, tannic acid and zinc chloride.

[0017] In this application, acrylamide and acrylic acid are monomers for synthesizing the hydrogel, with a mass ratio of 9:1 to 7:3. N,N-methylenebisacrylamide is a crosslinking agent, added at 0.05-1% of the total mass of acrylamide and acrylic acid. An initiator is used to initiate the crosslinking reaction between acrylamide and acrylic acid, added at 0.05-0.5% of the total mass of acrylamide and acrylic acid. The initiators in this application include ammonium persulfate and / or potassium persulfate. Sodium lignosulfonate is a rigid molecular chain for forming an interpenetrating network structure hydrogel and an antibacterial and antioxidant agent, added at a mass ratio of 1:2 to 1:10 of the total mass of acrylamide and acrylic acid. Tannic acid is an antibacterial and antioxidant agent, added at a mass ratio of 1:2 to 1:10 of the total mass of acrylamide and acrylic acid. Zinc chloride is an antibacterial agent and also acts as a coordinating crosslinking agent for the binding of tannic acid and the hydrogel, with a mass ratio of zinc chloride to tannic acid of 1:1 to 1:4.

[0018] In the antibacterial and antioxidant lignin composite hydrogel provided in this application embodiment, acrylamide and acrylic acid undergo a cross-linking reaction under the action of N,N-methylenebisacrylamide and an initiator to form a hydrogel matrix. After adding sodium lignin sulfonate, an interpenetrating network structure is introduced into the hydrogel matrix while retaining its antibacterial and antioxidant properties. By introducing tannic acid and zinc chloride, a complex and tightly structured antibacterial and antioxidant lignin composite hydrogel is formed, thereby effectively dispersing stress, reducing defects caused by phase separation, and improving the antibacterial and antioxidant properties, mechanical stability, and self-healing properties of the hydrogel.

[0019] Specifically, in the antibacterial and antioxidant lignin composite hydrogel provided in this application embodiment, the mechanism of action of tannic acid and zinc chloride is as follows: (1) Tannic acid is a class of polyphenolic compounds that are widely found in plants and have strong biological activity. Tannic acid can bind to proteins on the surface of bacteria, causing damage to the cell wall and membrane structure and affecting the normal function of bacteria; it can also chelate metal ions such as iron ions required for bacterial survival, thereby inhibiting the metabolic process of bacteria and the activity of key enzymes in the body, interfering with the physiological metabolism of bacteria; it can also bind to the cell membrane, destroy the integrity of the membrane, and cause leakage of cell contents, thus having strong antibacterial properties.

[0020] (2) The structure of tannic acid is similar to that of sodium lignosulfonate, and its molecular structure contains a large number of phenolic hydroxyl groups and benzene rings. The phenolic hydroxyl groups in tannic acid can capture and neutralize free radicals such as hydroxyl radicals (·OH) and peroxy radicals (·OOH) by providing hydrogen atoms, generating relatively stable phenoxy radicals, thereby interrupting the free radical chain reaction. In addition, the phenolic hydroxyl groups in tannic acid can also react with Fe... 2+ The coordination of tannins with metal ions reduces the Fenton reaction that catalyzes the generation of free radicals. The aromatic rings and conjugated structures in tannins can stabilize electrons, acting as electron donors and reducing the activity of free radicals. Therefore, in addition to its antibacterial properties, tannins also possess strong antioxidant capabilities.

[0021] (3) Zn in zinc chloride 2+ It can bind to proteins and enzymes within bacterial cells, inhibiting their activity and interfering with bacterial metabolic processes; it can also bind to bacterial DNA, affecting DNA replication and transcription, thereby inhibiting bacterial growth and reproduction; it can also enter bacterial cells, disrupting intracellular ion balance and enzyme activity, leading to cell death; and it can inhibit the formation of bacterial biofilms, which is particularly important for combating chronic infections.

[0022] (4) Zn in zinc chloride 2+ It possesses strong coordination ability, enabling it to form coordinate bonds with donor atoms containing lone pairs of electrons (such as oxygen and nitrogen). The catechol in tannic acid and the hydroxyl and amino groups in the hydrogel matrix can serve as Zn... 2+ The coordination sites facilitate the coordination of zinc ions with them, and the resulting coordination bonds can greatly increase the crosslinking density of the polymer network in the hydrogel, thereby increasing the mechanical strength and mechanical stability of the hydrogel.

[0023] (5) Zn in zinc chloride 2+ The coordination bonds formed between the hydrogel and tannic acid and the hydrogel matrix can be broken and recombined under the influence of external stimuli such as pH and solvent environment, that is, dynamic reversible coordination can be formed. This dynamic characteristic can endow the hydrogel with self-healing ability.

[0024] In addition, this application provides a method for preparing an antibacterial and antioxidant lignin composite hydrogel, the method comprising: S01: Under a nitrogen atmosphere, acrylamide, acrylic acid, and N,N-methylenebisacrylamide undergo a polymerization reaction under the action of an initiator to form a hydrogel matrix.

[0025] Acrylamide and acrylic acid were dissolved in water to form acrylamide solution and acrylic acid solution, respectively. Under a nitrogen atmosphere, the acrylamide solution and acrylic acid solution were mixed, and N,N-methylenebisacrylamide and an initiator were added. Free radical polymerization was initiated at 50-80℃ for 3-8 hours to synthesize the hydrogel matrix.

[0026] S02: Sodium lignosulfonate solution is slowly added to the hydrogel matrix to form a hydrogel with an interpenetrating network structure.

[0027] Sodium lignosulfonate is dissolved in water to form a sodium lignosulfonate solution. Under a nitrogen atmosphere, the sodium lignosulfonate solution is slowly added to a hydrogel matrix, and the reaction is carried out at 30-50℃ for 2-4 hours to form a hydrogel with an interpenetrating network structure. During the reaction, the hydroxyl and sulfonic acid groups in sodium lignosulfonate undergo hydrogen bonding and electrostatic interactions with the hydroxyl and amino groups in the hydrogel matrix. Simultaneously, they interpenetrate and entangle with the polymer molecular chains in the hydrogel matrix, forming a hydrogel with an interpenetrating network structure.

[0028] S03: After slowly adding tannic acid solution to the hydrogel, zinc chloride is added for cross-linking reaction to obtain lignin composite hydrogel.

[0029] Tannic acid and zinc chloride were dissolved in water to form tannic acid solution and zinc chloride solution, respectively. Under a nitrogen atmosphere, the tannic acid solution was slowly added to the hydrogel, followed by zinc chloride. After adjusting the pH to 7, the cross-linking reaction was carried out at 10-30℃ for 0.5-1 h to obtain a lignin composite hydrogel. During the cross-linking reaction, the catechol structure of tannic acid forms a coordination relationship with zinc chloride, and tannic acid also undergoes cross-linking reactions with carboxyl or amine groups in the hydrogel, resulting in a lignin composite hydrogel with good compatibility, structural stability, and antibacterial and antioxidant properties.

[0030] This application also provides an application of antibacterial and antioxidant lignin composite hydrogel, namely, the application of antibacterial and antioxidant lignin composite hydrogel in the preparation of medical dressings.

[0031] When used as a medical dressing, lignin-based hydrogels can aid in wound repair, prevent inflammation, and accelerate healing. After the wound has healed, applying an acidic solution to the surface of the lignin-based hydrogel will cause it to detach from the skin without adhering to it.

[0032] In addition, this application provides another application of antibacterial and antioxidant lignin composite hydrogel, namely, the application of antibacterial and antioxidant lignin composite hydrogel in the preparation of cartilage tissue materials.

[0033] When lignin-based hydrogels are used as cartilage tissue materials, the dynamic and reversible coordination between zinc chloride, tannic acid, and the hydrogel matrix enables the self-repair of cartilage tissue.

[0034] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0035] Example 1 This application provides an antibacterial and antioxidant lignin composite hydrogel, the preparation method of which includes: S101: Dissolve 2g of acrylamide in 40mL of water, then adjust the pH to 7 with 0.5mol / L NaOH solution to form an acrylamide solution. Dissolve 8g of acrylic acid in 40mL of water to form an acrylic acid solution. Add the acrylamide solution and acrylic acid solution to a four-necked flask and stir thoroughly under a nitrogen atmosphere. Mix 0.02g of ammonium persulfate and 0.02g of potassium persulfate, dissolve in 5mL of water, and slowly add 0.005g of N,N-methylenebisacrylamide to the four-necked flask. Initiate free radical polymerization at 60℃ and a stirring rate of 200r / min for 6h to synthesize the hydrogel matrix.

[0036] S102: Dissolve 2g of sodium lignosulfonate in 20mL of water to form a sodium lignosulfonate solution. Under a nitrogen atmosphere, slowly add the sodium lignosulfonate solution to the hydrogel matrix and react for 3h at 40℃ and a stirring rate of 200r / min to form a hydrogel with an interpenetrating network structure.

[0037] S103: 2g of tannic acid was dissolved in 10mL of water to form a tannic acid solution. 1g of zinc chloride was dissolved in 10mL of water to form a zinc chloride solution. Under a nitrogen atmosphere, the tannic acid solution was slowly added to the hydrogel and mixed thoroughly. Then, the zinc chloride solution was added, and the pH was adjusted to 7 using a 0.5mol / L NaOH solution. The cross-linking reaction was carried out at 20℃ and a stirring rate of 200r / min for 1h to obtain a lignin composite hydrogel.

[0038] Example 2 This application provides an antibacterial and antioxidant lignin composite hydrogel, the preparation method of which includes: S201: Dissolve 1g of acrylamide in 40mL of water, then adjust the pH to 7 with 0.5mol / L NaOH solution to form an acrylamide solution. Dissolve 9g of acrylic acid in 40mL of water to form an acrylic acid solution. Add the acrylamide solution and acrylic acid solution to a four-necked flask and stir thoroughly under a nitrogen atmosphere. Dissolve 0.05g of potassium persulfate in 5mL of water, and slowly add 0.1g of N,N-methylenebisacrylamide to the four-necked flask. Initiate free radical polymerization at 50℃ and a stirring rate of 200r / min for 8 hours to synthesize the hydrogel matrix.

[0039] S202: Dissolve 5g of sodium lignosulfonate in 20mL of water to form a sodium lignosulfonate solution. Under a nitrogen atmosphere, slowly add the sodium lignosulfonate solution to the hydrogel matrix and react for 4h at 30℃ and a stirring rate of 200r / min to form a hydrogel with an interpenetrating network structure.

[0040] S203: Dissolve 1g of tannic acid in 10mL of water to form a tannic acid solution. Dissolve 1g of zinc chloride in 10mL of water to form a zinc chloride solution. Under a nitrogen atmosphere, slowly add the tannic acid solution to the hydrogel and mix thoroughly. Then add the zinc chloride solution. Adjust the pH to 7 using a 0.5mol / L NaOH solution. Perform a crosslinking reaction at 10℃ and a stirring rate of 200r / min for 1h to obtain a lignin composite hydrogel.

[0041] Example 3 This application provides an antibacterial and antioxidant lignin composite hydrogel, the preparation method of which includes: S301: Dissolve 3g of acrylamide in 40mL of water, then adjust the pH to 7 with 0.5mol / L NaOH solution to form an acrylamide solution. Dissolve 8g of acrylic acid in 40mL of water to form an acrylic acid solution. Add the acrylamide solution and acrylic acid solution to a four-necked flask and stir thoroughly under a nitrogen atmosphere. Dissolve 0.005g of ammonium persulfate in 5mL of water, and slowly add 0.05g of N,N-methylenebisacrylamide to the four-necked flask. Initiate free radical polymerization at 80℃ and a stirring rate of 200r / min for 3h to synthesize the hydrogel matrix.

[0042] S302: Dissolve 1g of sodium lignosulfonate in 20mL of water to form a sodium lignosulfonate solution. Under a nitrogen atmosphere, slowly add the sodium lignosulfonate solution to the hydrogel matrix and react for 2h at 50℃ and a stirring rate of 200r / min to form a hydrogel with an interpenetrating network structure.

[0043] S303: Dissolve 5g of tannic acid in 10mL of water to form a tannic acid solution. Dissolve 1.25g of zinc chloride in 10mL of water to form a zinc chloride solution. Under a nitrogen atmosphere, slowly add the tannic acid solution to the hydrogel and mix thoroughly. Then add the zinc chloride solution. Adjust the pH to 7 using a 0.5mol / L NaOH solution. Perform a crosslinking reaction at 30℃ and a stirring rate of 200r / min for 0.5h to obtain a lignin composite hydrogel.

[0044] Comparative Example 1 The comparative example in this application provides a hydrogel, the raw materials of which are the same as in Example 1, except that sodium lignosulfonate, tannic acid and zinc chloride are not included. The preparation method of this hydrogel is the same as in Example 1, except that steps S102 and S103 are not included.

[0045] Comparative Example 2 The comparative example in this application provides a hydrogel, which is prepared using the same raw materials as in Example 1, except that it does not include tannic acid and zinc chloride. The preparation method of this hydrogel is the same as in Example 1, except that step S103 is not included.

[0046] Comparative Example 3 The comparative example in this application provides a hydrogel, the raw materials of which are the same as in Example 1, except that sodium lignosulfonate is not included. The preparation method of this hydrogel is the same as in Example 1, except that step S102 is not included.

[0047] Comparative Example 4 The comparative example in this application provides a hydrogel, the raw materials of which are the same as those in Example 1, except that tannic acid is not included. The preparation method of this hydrogel is the same as that in Example 1, except that only zinc chloride is added in step S103.

[0048] Comparative Example 5 The comparative example in this application provides a hydrogel, the raw materials of which are the same as those in Example 1, except that zinc chloride is not included. The preparation method of this hydrogel is the same as that in Example 1, except that only tannic acid is added in step S103.

[0049] Comparative Example 6 The comparative example in this application provides a hydrogel, the raw materials of which are the same as those in Example 1. The preparation method of this hydrogel is the same as that in Example 1, except that the pH value in step S103 is set to 6.

[0050] Comparative Example 7 The comparative example in this application provides a hydrogel, the raw materials of which are the same as those in Example 1. The preparation method of this hydrogel is the same as that in Example 1, except that the pH value in step S103 is adjusted to 8.5.

[0051] In this application, the mechanical properties, antioxidant properties, antibacterial properties, and self-healing properties of the hydrogels prepared in Examples 1-3 and Comparative Examples 1-7 were tested respectively, and the specific contents are as follows: 1. Mechanical property testing The mechanical properties of the hydrogels prepared in Examples 1-3 and Comparative Examples 1-7 were tested in this application to compare the effects of sodium lignosulfonate, tannic acid, zinc chloride, and system pH on the mechanical properties of the hydrogels. The test results are shown in Table 1.

[0052] Table 1: Mechanical properties of hydrogels prepared in Examples 1-3 and Comparative Examples 1-7 As shown in Table 1, compared with Example 1 and Comparative Example 1, the hydrogel exhibits the lowest mechanical strength when sodium lignosulfonate, tannic acid, and zinc chloride are absent. Compared with Example 1 and Comparative Example 2, the hydrogel also exhibits low mechanical strength when tannic acid and zinc chloride are absent. Compared with Example 1 and Comparative Examples 3-5, the mechanical strength of the hydrogel decreases when sodium lignosulfonate, tannic acid, or zinc chloride are absent. Compared with Example 1 and Comparative Examples 6 and 7, the mechanical strength of the hydrogel is affected by pH, being weaker under acidic conditions and stronger under alkaline conditions.

[0053] The above indicates that sodium lignosulfonate, tannic acid, zinc chloride, and the pH value of the system all significantly affect the mechanical properties of the hydrogel, especially zinc chloride and the pH value. This is mainly because zinc chloride can form coordination bonds with the catechol groups in tannic acid and the hydroxyl and amino groups in the hydrogel, thereby achieving cross-linking between tannic acid and the hydrogel and increasing the cross-linking density of the hydrogel network. In addition, the pH value of the system regulates the changes in the coordination form between zinc chloride and catechol, hydroxyl, and amino groups. The coordination ability gradually increases as the pH changes from acidic to alkaline, thus affecting the overall mechanical properties of the hydrogel. Therefore, from the perspective of mechanical properties, if the hydrogel does not contain sodium lignosulfonate, tannic acid, and zinc chloride, its application areas may be limited to materials such as skin dressings with lower mechanical property requirements; while the introduction of sodium lignosulfonate, tannic acid, and zinc chloride significantly improves the mechanical properties of the hydrogel, expanding its application range to areas with higher mechanical property requirements, such as cartilage replacement and tissue repair.

[0054] 2. Antioxidant performance testing The antioxidant properties of hydrogels can broaden their application areas, such as inhibiting inflammatory responses in tissue repair processes. Based on this, in the embodiments of this application, 0.1g of the hydrogels prepared in Examples 1-3 and Comparative Examples 1-7 were placed in 50mL centrifuge tubes, and 10mL of 0.2mmol / L DPPH (1,1-diphenyl-2-trinitrophenylhydrazine) solution was added to the centrifuge tubes. The mixtures were shaken and reacted for 180min to form test samples. Simultaneously, different hydrogels were placed in 50mL centrifuge tubes, 10mL of anhydrous ethanol was added, and the mixtures were shaken and reacted for 180min to serve as control samples. The absorbance of the test samples and control samples was detected at 517nm using a UV spectrophotometer, and the residual DPPH content was calculated, as shown in Table 2, to characterize the antioxidant properties of different hydrogels.

[0055] The formula for calculating the residual DPPH content is as follows: In the formula: The absorbance of the hydrogel in the DPPH dilution solution; The absorbance of the hydrogel in ethanol solution; Soaking time, in hours (h); and The absorbance is at t=0.

[0056] Table 2: Residual DPPH content of hydrogels prepared in Examples 1-3 and Comparative Examples 1-7 As shown in Table 2, compared with Comparative Examples 1-4 which did not contain sodium lignosulfonate or tannic acid, the hydrogels prepared in Examples 1-3 had lower residual DPPH content and stronger antioxidant properties. This indicates that sodium lignosulfonate and tannic acid play a significant role in improving the antioxidant properties of the hydrogels. However, compared with Comparative Examples 5-7, the residual DPPH content of the hydrogels prepared in Examples 1-3 did not change significantly, indicating that zinc chloride and the pH of the system had little effect on the antioxidant properties of the hydrogels.

[0057] 3. Antibacterial performance testing In this application, the antibacterial properties of the hydrogels prepared in Examples 1-3 and Comparative Examples 1-7 were tested using the method described in the WS / T 650-2019 standard, and the results are shown in Table 3.

[0058] Table 3: Antibacterial properties of the hydrogels prepared in Examples 1-3 and Comparative Examples 1-7 As shown in Table 3, the hydrogels prepared in Comparative Examples 1 and 2 without sodium lignosulfonate, tannic acid and zinc chloride had poor antibacterial properties. This indicates that sodium lignosulfonate, tannic acid and zinc chloride all play an important role in the antibacterial properties of the hydrogels.

[0059] 4. Self-healing performance test Traditional hydrogel materials are prone to breakage, tearing, or permanent deformation when subjected to external forces, leading to performance degradation and frequent replacement. Self-healing hydrogels, on the other hand, can automatically repair themselves after damage, restoring their original structure and function, thereby extending their lifespan, reducing replacement frequency, and lowering operating costs.

[0060] Based on this, to ensure that the hydrogels prepared in the embodiments of this application have self-healing properties, the hydrogels prepared in Examples 1-3 and Comparative Examples 1-7 were cut into dumbbell-shaped strips of 4×50cm, cut and rejoined. By comparing the mechanical strength of the strips before and after repair, their self-healing efficiency was calculated, and Table 4 was obtained, thereby quantifying the self-healing performance of the material.

[0061] The formula for calculating self-repair efficiency is as follows: Self-healing efficiency (%) = Tensile strength of the repaired hydrogel (MPa) / Tensile strength of the original hydrogel (MPa) × 100% Table 4: Self-healing efficiency of the hydrogels prepared in Examples 1-3 and Comparative Examples 1-7 As shown in Table 4, the self-healing efficiency of the hydrogels prepared in Examples 1-3 is 98.7-99.8%, exhibiting high self-healing efficiency. Comparative Examples 1-5 show that when the hydrogel does not contain tannic acid and / or zinc chloride, the self-healing efficiency is low, especially when tannic acid and zinc chloride are absent, with a self-healing efficiency of only 28%. This indicates that tannic acid and zinc chloride play an important role in the self-healing properties of the hydrogel. The principle is mainly based on the dynamic coordination bonds formed between the catechol groups in tannic acid and the amine or hydroxyl groups in the hydrogel through zinc chloride. After breakage, these bonds can recombine, repairing cracks and promoting fracture healing.

[0062] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An antibacterial and antioxidant lignin composite hydrogel, characterized in that, The raw materials for preparation include acrylamide, acrylic acid, N,N-methylenebisacrylamide, initiator, sodium lignosulfonate, tannic acid and zinc chloride.

2. The antibacterial and antioxidant lignin composite hydrogel according to claim 1, characterized in that, The mass ratio of acrylamide to acrylic acid is 9:1-7:

3.

3. The antibacterial and antioxidant lignin composite hydrogel according to claim 1, characterized in that, Based on the total mass of the acrylamide and the acrylic acid, the amounts of N,N-methylenebisacrylamide and the initiator added are 0.05-1% and 0.05-0.5%, respectively.

4. The antibacterial and antioxidant lignin composite hydrogel according to claim 1, characterized in that, The mass ratio of sodium lignosulfonate to the total mass of acrylamide and acrylic acid is 1:2 to 1:10; the mass ratio of tannic acid to the total mass of acrylamide and acrylic acid is 1:2 to 1:

10.

5. The antibacterial and antioxidant lignin composite hydrogel according to claim 1, characterized in that, The mass ratio of zinc chloride to tannic acid is 1:1 to 1:

4.

6. The antibacterial and antioxidant lignin composite hydrogel according to claim 1, characterized in that, The initiator includes ammonium persulfate and / or potassium persulfate.

7. The method for preparing the antibacterial and antioxidant lignin composite hydrogel according to any one of claims 1-6, characterized in that, include: Under a nitrogen atmosphere, acrylamide, acrylic acid, and N,N-methylenebisacrylamide undergo a polymerization reaction in the presence of an initiator to form a hydrogel matrix; A sodium lignosulfonate solution is slowly added to the hydrogel matrix to react and form a hydrogel with an interpenetrating network structure. After slowly adding tannic acid solution to the hydrogel, zinc chloride is added for cross-linking reaction to obtain lignin composite hydrogel.

8. The method for preparing the antibacterial and antioxidant lignin composite hydrogel according to claim 7, characterized in that, The polymerization reaction is carried out at a temperature of 50-80℃ for 3-8 hours; the hydrogel with the interpenetrating network structure is prepared at a temperature of 30-50℃ for 2-4 hours; the crosslinking reaction is carried out at a temperature of 10-30℃ for 0.5-1 hours and at a pH of 7.

9. The application of the antibacterial and antioxidant lignin composite hydrogel according to any one of claims 1-6 or the antibacterial and antioxidant lignin composite hydrogel prepared by the preparation method according to claim 7 or 8 in the preparation of medical dressings.

10. The application of the antibacterial and antioxidant lignin composite hydrogel according to any one of claims 1-6 or the antibacterial and antioxidant lignin composite hydrogel prepared by the preparation method according to claim 7 or 8 in the preparation of cartilage tissue materials.

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