A double network hydrogel loaded with nano-silver and a preparation method and application thereof

Abstract

The application discloses a kind of double-network hydrogel loaded with nano-silver and its preparation method and application, belong to the technical field of hydrogel preparation.The application solves the problem that the current double-network hydrogel preparation method is complex, and the mechanical properties, gel forming property, elasticity, water resistance, antibacterial property and temperature stability are poor.The application first prepares polyvinyl alcohol / nano-silver solution, places gluconolactone solution in the above solution to obtain single-network gel solution, mixes sodium alginate solution with glycerol solution, and places it in the single-network hydrogel solution to obtain double-network hydrogel solution, then freezes and thaws the double-network hydrogel solution to obtain double-network hydrogel loaded with nano-silver.The application uses sodium alginate and polyvinyl alcohol to construct double-network gel structure, and loads antibacterial particles nano-silver, which not only has good antibacterial effect, but also has controllable structure, excellent mechanical properties and good swelling performance, and can be used as wound dressing for wound repair.

Description

Technical Field

[0001] This invention belongs to the field of hydrogel preparation technology, and particularly relates to a dual-network hydrogel loaded with silver nanoparticles, its preparation method and application. Background Technology

[0002] Hydrogels are hydrophilic polymers with a three-dimensional cross-linked network structure. They can absorb and store water without dissolving, and simultaneously possess high air permeability, antibacterial properties, flexibility, and adhesion, making them excellent wound dressing materials. Furthermore, hydrogels are diverse; by modifying the material formulation and preparation methods, gel parameters can be controlled to obtain hydrogels with desired structures and properties to suit different applications. Hydrogels can also load bioactive molecules for sustained drug release on wound surfaces, promoting healing and providing antibacterial effects. However, traditional hydrogels still have limitations: hydrogels formed from a single polymer network often struggle to balance mechanical strength, self-healing properties, or environmental responsiveness, limiting their performance in complex wound repair and adsorption scenarios.

[0003] In recent years, dual-network hydrogels have attracted attention due to their dual-network structure. Dual-network hydrogels consist of two polymer networks: a low-concentration, highly cross-linked, brittle first network and a high-concentration, cross-linked, soft, and stretchable second network. Common methods for preparing dual-network hydrogels include two-step polymerization and a one-pot method. The two-step polymerization method offers great versatility and flexibility in preparing robust dual-network hydrogels. However, this method requires multiple steps and has limitations; for example, the process is cumbersome and time-consuming, and it cannot directly prepare dual-network hydrogels with complex shapes, making it difficult to meet a wide range of or specific applications. The one-pot method combines multiple reaction steps in a single reaction vessel, eliminating the need for intermediate product separation and purification, reducing operational steps and experimental time, and improving preparation efficiency. The prepared dual-network hydrogels exhibit good uniformity. However, controlling the reaction conditions is difficult, and because multiple reactions occur simultaneously, it is difficult to precisely control the network structure. Parameters such as the cross-linking density and molecular weight of each network are difficult to precisely control, leading to deviations in the performance of the dual-network hydrogel from expectations. For example, one network may be over-crosslinked while the other is under-crosslinked, affecting the overall performance of the dual-network hydrogel. Therefore, developing an efficient and controllable strategy for preparing dual-network hydrogels remains a technical challenge.

[0004] Sodium alginate (SA) is a linear anionic polyelectrolyte polysaccharide derived from bacteria, brown algae, and kelp. It is inexpensive, widely available, and extracted using environmentally friendly methods, making it highly usable and non-toxic. However, as a natural polymer, the hydrogel formed from sodium alginate suffers from insufficient mechanical properties, poor temperature stability, and poor gel formation, making it difficult to withstand high loads when used alone. SA hydrogels are commonly prepared using ionic crosslinking methods, but traditional crosslinking agents (such as CaCl2) may cause local fluctuations in ion concentration, necessitating the use of crosslinking methods with higher biocompatibility. Polyvinyl alcohol (PVA) is a linear polyhydroxy polymer derived from the hydrolysis of polyvinyl acetate. It possesses excellent biodegradability and non-toxicity, along with superior elasticity and toughness, achieving an elongation at break of over 1000% and high compressive strength (elastic modulus 10-100 kPa). However, the hydrogel formed from PVA exhibits poor elasticity and insufficient water resistance, typically requiring 3-5 freeze-thaw cycles (each freezing lasting several hours), making it unsuitable for rapid prototyping needs.

[0005] In summary, there is a need to develop a dual-network hydrogel that has a simple preparation method, can adsorb silver nanoparticles without causing them to agglomerate, and possesses good mechanical properties, formability, elasticity, antibacterial properties, and adsorption properties, exhibiting excellent overall performance. Summary of the Invention

[0006] To address the problems of complex preparation methods and poor mechanical properties, formability, elasticity, antibacterial properties, and adsorption properties of existing dual-network hydrogels, this invention provides a dual-network hydrogel loaded with silver nanoparticles, its preparation method, and its application.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] One objective of this invention is to provide a method for preparing a dual-network hydrogel loaded with silver nanoparticles, the method comprising the following steps:

[0009] (1) Preparation of polyvinyl alcohol / silver nano solution: Disperse silver nanoparticles in polyvinyl alcohol solution to obtain polyvinyl alcohol / silver nano solution;

[0010] (2) Preparation of single-network hydrogel solution: Place gluconolactone solution in polyvinyl alcohol / nano silver solution to obtain single-network hydrogel solution;

[0011] (3) Preparation of double network hydrogel solution: Sodium alginate solution and glycerol solution are mixed and stirred to obtain a mixture. The mixture is added to a single network hydrogel solution at a certain temperature and then stirred to obtain a double network hydrogel solution.

[0012] (4) Preparation of double network hydrogel loaded with silver nanoparticles: Pour the double network hydrogel solution into a mold, let it stand for a period of time, seal it, and perform freeze-thaw cycles to obtain double network hydrogel loaded with silver nanoparticles.

[0013] Further, the concentration of the polyvinyl alcohol solution in (1) is 4~10 g / L, and the concentration of nano silver in the polyvinyl alcohol / nano silver solution is 200~800 μg / mL.

[0014] Further, the concentration of gluconolactone solution in (2) is 0.6~1.2 g / L.

[0015] Further specifying, (3) the temperature is 40~55 ℃.

[0016] Further, in (3), the concentration of sodium alginate solution is 2~8 g / L, and the volume ratio of sodium alginate solution to glycerol is 1:1.

[0017] Further specified, (3) the stirring temperature is 40~70 ℃, the speed is 150~200 r / min, and the time is 1~3h.

[0018] Further specifying, the freeze-thaw cycle process in (4) is as follows: the sealed hydrogel solution is frozen at -80 °C for 0.5~4 h, and then thawed at room temperature.

[0019] Further, in (4), the number of freeze-thaw cycles is 2 to 5.

[0020] Further, the freeze-thaw cycle number in (4) is 4 times.

[0021] The second objective of this invention is to provide a dual-network hydrogel loaded with silver nanoparticles prepared by the above method.

[0022] The third objective of this invention is to provide an application of the above-mentioned dual-network hydrogel loaded with silver nanoparticles, specifically, the dual-network hydrogel is used in antibacterial materials and adsorbent materials.

[0023] The beneficial effects achieved by this invention are as follows:

[0024] (1) In this invention, sodium alginate has good biocompatibility, biodegradability, and low immunogenicity, and has a strong affinity for silver nanoparticles, resulting in good loading effect for silver nanoparticles. Polyvinyl alcohol has low protein adsorption and good biocompatibility, and the gel network structure it forms has good mechanical properties and high film-forming ability. This invention combines the natural polymer sodium alginate with the synthetic polymer polyvinyl alcohol to prepare a dual-network hydrogel loaded with silver nanoparticles that combines the advantages of both.

[0025] (2) This invention uses nano-silver as antibacterial particles. Compared with ordinary silver ions, nano-silver has high antibacterial activity, stability and permeability. Moreover, nano-silver has lower drug resistance and stronger membrane permeability compared with traditional antibiotics. In addition, this invention uses sodium alginate and polyvinyl alcohol as carriers to load nano-silver, which further improves the biocompatibility of the dual-network hydrogel and enhances its bioavailability.

[0026] (3) The nano-silver used in this invention is self-made biosynthesized using fungal fermentation broth. The synthesized nano-silver is spherical and has a uniform particle size. In the method of this invention, polyvinyl alcohol is first dissolved and nano-silver powder is added. A polyvinyl alcohol solution with a concentration of 4~10 g / mL can help the nano-silver to be uniformly dispersed in the polyvinyl alcohol / nano-silver solution without agglomeration. After the gel is formed, the nano-silver will not precipitate due to repeated freeze-thaw cycles.

[0027] (4) In the prior art, the preparation of hydrogels by crosslinking sodium alginate and polyvinyl alcohol often adopts multiple crosslinking methods, such as combining freeze-thaw (physical crosslinking of polyvinyl alcohol) and ionic crosslinking (chemical crosslinking of sodium alginate) to form a double-network hydrogel. However, the above methods are complicated to operate and use chemical crosslinking agents, which affects the biocompatibility of the hydrogel. Moreover, the preparation method of double-network hydrogels in the prior art requires repeated freeze-thaw methods with a single overnight freeze, resulting in a long preparation time for the hydrogel.

[0028] (5) In the freeze-thaw cycle of the present invention, sodium alginate and polyvinyl alcohol are rapidly frozen at -80 ℃ for 0.5~4 h, then thawed at room temperature, and the freeze-thaw cycle is repeated. However, the freeze-thaw cycle does not need to be overnight, which greatly shortens the freeze-thaw cycle time and thus reduces the gel preparation time. In addition, glycerol solution is added as a protective agent in the preparation process of the double network hydrogel to protect the uniformity of sodium alginate in the rapid freezing freeze-thaw cycle environment and prevent the system from stratifying or decreasing in viscosity after the sodium alginate is thawed, thus preventing the formation of hydrogel. The ratio of sodium alginate, polyvinyl alcohol and nano silver is appropriate. Under the rapid freezing conditions with a short freezing time, both sodium alginate and polyvinyl alcohol can help disperse nano silver, so that nano silver does not precipitate and sodium alginate does not clump. They can interpenetrate with polyvinyl alcohol to form a double network hydrogel.

[0029] In this invention, the concentration of the polyvinyl alcohol solution is 4~10 g / L, the concentration of nano-silver in the polyvinyl alcohol / nano-silver solution is 200~800 μg / mL, and the concentration of sodium alginate solution is 2~8 g / L. This results in a polyvinyl alcohol concentration of 2~5 g / L, a nano-silver concentration of 50~200 μg / mL, and a sodium alginate concentration of 1~4 g / L in the double-network hydrogel loaded with nano-silver. Under this concentration system, the hydrogel has high uniformity, does not separate into layers after repeated freeze-thaw cycles, does not hydrate, and the nano-silver does not agglomerate. Attached Figure Description

[0030] Figure 1These are morphological images of the double-network hydrogels loaded with silver nanoparticles prepared in Examples 1-4;

[0031] Figure 2 These are scanning electron microscope images of the silver nanoparticle-loaded double-network hydrogels prepared in Examples 2-3;

[0032] Figure 3 These are Fourier transform infrared spectra of the double-network hydrogels loaded with silver nanoparticles prepared in Examples 1-4;

[0033] Figure 4 These are the XRD patterns of the double-network hydrogels loaded with silver nanoparticles prepared in Examples 1-4;

[0034] Figure 5 The results are the viscosity test results of the dual-network hydrogel loaded with silver nanoparticles prepared in Example 6;

[0035] Figure 6 The swelling performance test results are for the dual-network hydrogels loaded with silver nanoparticles prepared in Examples 1-4;

[0036] Figure 7 These are test images of the antibacterial effect of the double-network hydrogels loaded with silver nanoparticles prepared in Examples 5-7;

[0037] Figure 8 These are images of antibacterial biofilms of the dual-network hydrogels loaded with silver nanoparticles prepared in Examples 5-7;

[0038] Figure 9 This is a morphological diagram of the double-network hydrogel loaded with silver nanoparticles prepared in Comparative Example 1.

[0039] DR2, DR3, DR4, and DR5 represent freeze-thaw cycles of 2, 3, 4, and 5, respectively. Detailed Implementation

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the embodiments in the specification. Many specific details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0042] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0043] Example 1

[0044] (1) Preparation of polyvinyl alcohol / nano silver solution: Accurately weigh polyvinyl alcohol, dissolve polyvinyl alcohol in distilled water, place the solution on a rotary evaporator and stir in a water bath at 180 r / min at 95℃ for 45 min to ensure that the polyvinyl alcohol is fully dissolved, prepare 100 mL of 8 g / L polyvinyl alcohol solution, and after the polyvinyl alcohol solution is cooled to about 50℃, evenly disperse 5 mg of nano silver particles in 100 mL of polyvinyl alcohol solution to obtain polyvinyl alcohol / nano silver solution;

[0045] The process of synthesizing nano-silver is as follows: silver nitrate solution (1 mg / mL) and cell-free filtrate from liquid fermentation of oyster mushrooms were mixed at a volume ratio of 6:4 (v / v). The pH of the reaction system was adjusted to 11.2, the reaction temperature was 88 ℃, the reaction time was 30 min, and the stirring rate was 80 rpm. Compared with before synthesis, the color of the cell-free filtrate solution was significantly darker after synthesis. The system after centrifugation was centrifuged at 12000 rpm for 30 min. The supernatant was discarded, and the system was washed repeatedly with distilled water three times to obtain pure nano-silver. The nano-silver was then freeze-dried into nano-silver powder for later use.

[0046] Method for obtaining cell-free filtrate from liquid fermentation of oyster mushrooms: Oyster mushrooms were cultured in PDA liquid medium at an inoculation rate of 3 mycelial blocks / 150mL medium at 25℃ for 6 days. After cultivation, the mycelium was removed by filtration through 6 layers of gauze to obtain cell-free filtrate. The culture medium formula was as follows: 200g potato chunks were boiled for 20 minutes, filtered, and then 20g glucose was added to bring the volume to 1000mL.

[0047] (2) Preparation of single-network gel solution: Dissolve gluconolactone in distilled water to obtain 10 mL of gluconolactone solution with a concentration of 0.8 g / L. Place the gluconolactone solution in 100 mL of polyvinyl alcohol / nano silver solution prepared in (1) to obtain single-network gel solution.

[0048] (3) Preparation of double network gel solution: Sodium alginate was dissolved in distilled water to prepare 50 mL of sodium alginate solution with a concentration of 5 g / L. Glycerin was used as a protective agent and added to water to form a 5 wt% glycerin solution. The sodium alginate solution and the glycerin solution were mixed at a volume ratio of 1:1 and stirred evenly to form a paste. 50 mL of the paste was placed in 50 mL of single network gel solution and then placed on a rotary evaporator and stirred in a water bath at 180 r / min at 65℃ for 1 h to ensure that sodium alginate was fully dissolved and mixed evenly with polyvinyl alcohol and nano silver to obtain double network gel solution.

[0049] (4) Preparation of double network hydrogel loaded with silver nanoparticles: Pour the double network gel solution into the mold, let it stand for a period of time until the temperature drops to room temperature, and seal it after the bubbles are eliminated. Perform freeze-thaw cycle. The freeze-thaw process is as follows: put the sealed gel solution and the mold into a -80℃ freezer for 2 h, and then place it at room temperature to thaw. This is one cycle. A total of 5 freeze-thaw cycles are performed to obtain sodium alginate / polyvinyl alcohol double network hydrogel loaded with silver nanoparticles.

[0050] Example 2

[0051] The difference between this embodiment and embodiment 1 is that: (4) involves two freeze-thaw cycles, while the other operations and process parameters are the same as in embodiment 1.

[0052] Example 3

[0053] The difference between this embodiment and embodiment 1 is that: (4) involves 3 freeze-thaw cycles, while the other operations and process parameters are the same as in embodiment 1.

[0054] Example 4

[0055] The difference between this embodiment and embodiment 1 is that: (4) involves 4 freeze-thaw cycles, while the other operations and process parameters are the same as in embodiment 1.

[0056] Example 5

[0057] The difference between this embodiment and Example 1 is that: (1) 50 mg of silver nanoparticles were uniformly dispersed in 100 mL of polyvinyl alcohol solution to obtain a polyvinyl alcohol / silver nanoparticle solution with a silver nanoparticle concentration of 500 μg / mL and a polyvinyl alcohol concentration of 4 g / L; (2) the sodium alginate concentration was 6 g / L, the freeze-thaw conditions were the same, and the number of freeze-thaw cycles was 3. The final concentration of silver nanoparticles in the dual-network hydrogel in this embodiment was 250 μg / mL. This embodiment can successfully prepare a dual-network hydrogel, and the hydrogel has better extensibility than that prepared in Example 1.

[0058] Example 6

[0059] The difference between this embodiment and Example 2 is that: (1) 25 mg of silver nanoparticles were uniformly dispersed in 100 mL of polyvinyl alcohol solution to obtain a polyvinyl alcohol / silver nanoparticle solution with a silver nanoparticle concentration of 250 μg / mL. The freeze-thaw conditions were the same, and the number of freeze-thaw cycles was 3. The final concentration of silver nanoparticles in the dual-network hydrogel in this embodiment was 125 μg / mL. This embodiment can successfully prepare a dual-network hydrogel, and the hydrogel has better extensibility than that prepared in Example 1.

[0060] Example 7

[0061] The difference between this embodiment and Example 2 is that: (1) 12.5 mg of silver nanoparticles were uniformly dispersed in 100 mL of polyvinyl alcohol solution to obtain a polyvinyl alcohol / silver nanoparticle solution with a silver nanoparticle concentration of 125 μg / mL. The polyvinyl alcohol concentration was 4 g / mL, and the sodium alginate concentration was 6 g / mL. The freeze-thaw conditions were the same, and the number of freeze-thaw cycles was 3. The final concentration of silver nanoparticles in the dual-network hydrogel in this embodiment was 62.5 μg / mL. This embodiment can successfully prepare a dual-network hydrogel, and the hydrogel extensibility is better than that prepared in Example 1.

[0062] Comparative Example 1

[0063] The differences between this comparative example and Example 1 are: (1) the concentration of polyvinyl alcohol solution is 16 g / mL, and (2) the concentration of sodium alginate solution is 7 g / L. The remaining process steps and parameter settings are the same as in Example 1. Figure 9 As shown, although the surface of the hydrogel is smooth and flat, the edges are irregular and there is obvious damage, indicating that the hydrogel in this comparison ratio is hard, has poor extensibility, and is easy to break.

[0064] Comparative Example 2

[0065] The difference between this comparative example and Example 1 is that the crosslinking method of polyvinyl alcohol and sodium alginate is different from that in Example 1. This comparative example uses CaCl2 for chemical crosslinking, and the specific steps are as follows:

[0066] (1) Preparation of polyvinyl alcohol / nano silver solution: Accurately weigh polyvinyl alcohol, dissolve polyvinyl alcohol in distilled water, place the solution on a rotary evaporator and stir in a water bath at 95 ℃ and 180 r / min for 45 min to ensure that the polyvinyl alcohol is fully dissolved, prepare 100 mL of 8 g / L polyvinyl alcohol solution, and after the polyvinyl alcohol solution is cooled to about 50 ℃, evenly disperse 5 mg of nano silver particles in 100 mL of polyvinyl alcohol solution to obtain polyvinyl alcohol / nano silver solution;

[0067] (2) Preparation of single-network gel solution: Same as (2) in Example 1;

[0068] (3) Preparation of the double-network gel solution: Same as (3) in Example 1;

[0069] (4) Preparation of a double-network hydrogel loaded with silver nanoparticles: The double-network gel solution was poured into a mold and allowed to stand for a period of time until the temperature dropped to room temperature. Then, 300 mL of a 2 wt% CaCl2 solution was slowly added along the mold wall. The mixture was gently shaken to assist cross-linking. Cross-linking was successful after 7 minutes, resulting in a sodium alginate / polyvinyl alcohol double-network hydrogel loaded with silver nanoparticles. However, the surface of the hydrogel was uneven, with air bubbles, and the gel was soft and easily broken.

[0070] Testing and experimentation:

[0071] (1) The freeze-thaw morphology of the sodium alginate / polyvinyl alcohol double network hydrogels loaded with silver nanoparticles prepared in Examples 1-4 is as follows: Figure 1 As shown, the double-network hydrogels of Examples 1-4 exhibit good moldability and did not crack or break. Further tensile tests were conducted on the double-network hydrogels of Examples 1-4 using a universal testing machine. The test conditions were room temperature, a sample diameter of 5 mm, a length of 30 mm, and a tensile rate of 50 mm / min. The test results were as follows: the elongation at break and tensile strength of the double-network hydrogel after two freeze-thaw cycles in Example 2 were 253% and 10.7 kPa, respectively. With the increase in the number of freeze-thaw cycles, the elongation and tensile strength of the hydrogel both increased. The elongation rates after 3, 4, and 5 freeze-thaw cycles were 325%, 496%, and 514%, respectively, and the tensile strengths were 19.1 kPa, 35.8 kPa, and 40.9 kPa, respectively. Among them, the sodium alginate / polyvinyl alcohol double-network hydrogel loaded with nano-silver prepared in Example 1 exhibited the best hardness and toughness.

[0072] (2) Scanning electron micrographs of the sodium alginate / polyvinyl alcohol dual-network hydrogels loaded with silver nanoparticles prepared in Examples 2 and 3 are shown below. Figure 2 As shown in Figures A and B, both examples of the dual-network hydrogel exhibit a three-dimensional network structure, composed of numerous small pores of varying sizes and shapes, forming a honeycomb morphology. Pore measurement results show that the average pore size of the dual-network hydrogel after two freeze-thaw cycles is 13.80 nm, while the average pore size of the hydrogel after three cycles is 22.25 nm. The dual-network hydrogel after three freeze-thaw cycles has a greater number of pores than the dual-network hydrogel after two cycles, and the pore size distribution is wider and the shape is more regular and ordered. Therefore, the degree of cross-linking of the dual-network hydrogel after three freeze-thaw cycles is higher than that after two cycles, resulting in a more stable structure.

[0073] (3) The Fourier transform infrared spectra of the sodium alginate / polyvinyl alcohol dual-network hydrogels loaded with silver nanoparticles prepared in Examples 1-4 after freeze-thaw cycles are shown below. Figure 3 As shown in the figure. It can be seen from the figure that 1630cm -1The absorption peaks at the left and right correspond to the stretching vibrations of the C=O functional group, located at 1400 cm⁻¹. -1 The absorption peak at 1100 cm⁻¹ corresponds to the symmetric stretching vibration of the COO- functional group in sodium alginate. -1 The absorption peaks at the left and right correspond to the stretching vibrations of the CO functional groups in polyvinyl alcohol. Regardless of the number of freeze-thaw cycles, the positions of these peaks do not change significantly. (3450~3470 cm⁻¹) -1 The absorption peak at 2925 cm⁻¹ corresponds to the stretching vibration of the OH functional group in polyvinyl alcohol and sodium alginate. After 2 to 3 cycles, the absorption peak shifts to the left, indicating a weakening of the intermolecular hydrogen bond strength. However, the peak value remains almost unchanged in the subsequent two cycles. -1 The absorption peaks at the left and right correspond to the stretching vibrations of the CH functional group, appearing after 2 cycles and disappearing after 3 cycles.

[0074] (4) The XRD patterns of the sodium alginate / polyvinyl alcohol dual-network hydrogels loaded with silver nanoparticles prepared in Examples 1-4 are as follows: Figure 4 As shown in the figure, the dual-network hydrogels of Examples 1-4 all exhibited obvious characteristic diffraction peaks at around 19.3°, indicating the presence of a crystalline phase in these dual-network hydrogels. Furthermore, with the increase in the number of freeze-thaw cycles, the peak values ​​gradually became larger and the peak shapes gradually became sharper, indicating that the freeze-thaw cycles caused structural changes in the dual-network hydrogels. These structural changes ultimately led to an increase in the crystalline phase, promoting the increasingly perfect crystallization of the dual-network hydrogels.

[0075] (5) Sodium alginate and polyvinyl alcohol both have advantages such as good biocompatibility, strong biodegradability, low immunogenicity, and safety and non-toxicity, and also have certain adhesiveness, making them two good gel materials for preparing wound dressings. The sodium alginate / polyvinyl alcohol dual-network hydrogel loaded with nano-silver prepared in Example 6 was cut into circular pieces using a punch, gently placed on the back of the hand, and the back of the hand was rotated to test the viscosity of the dual-network hydrogel. The results... Figure 5 As shown, the dual-network hydrogel of the present invention can adhere well to the skin surface. When the hand is rotated 90° to the left and placed vertically, the dual-network hydrogel still adheres to the original position on the back of the hand without moving or falling off, indicating that the dual-network hydrogel has good adhesion.

[0076] (6) Hydrogels with high swelling ratios can absorb more liquid, making them suitable for applications requiring large amounts of liquid absorption. However, this can lead to structural instability or decreased mechanical strength, potentially causing wound infection when used as dressings. Hydrogels with low swelling ratios have limited liquid absorption capacity but are more structurally stable, making them suitable for applications requiring shape and strength maintenance, thus limiting their application range. Therefore, hydrogels used as wound dressings need to have moderate swelling capacity, absorbing wound exudate and maintaining a moist environment without excessive expansion that could cause discomfort or hinder wound healing. The swelling performance test results of the sodium alginate / polyvinyl alcohol dual-network hydrogels loaded with nano-silver prepared in Examples 1-4 are as follows: Figure 6 As shown in the figure, the dual-network hydrogel exhibited a rapid swelling rate during the initial swelling stage, and the swelling became more pronounced with increasing time. Over the next 12 hours, the dual-network hydrogel demonstrated strong water absorption capacity. The equilibrium swelling rates of the dry gels after 2, 3, 4, and 5 freeze-thaw cycles were 2058%, 1951%, 1844%, and 1791%, respectively. Both the equilibrium swelling rate and the initial swelling rate decreased with increasing freeze-thaw cycles, indicating that freeze-thaw cycles can modulate the swelling capacity of the dual-network hydrogel.

[0077] (7) The antibacterial activity of the sodium alginate / polyvinyl alcohol dual-network hydrogels loaded with silver nanoparticles prepared in Examples 5-7 was tested, and the test methods are as follows:

[0078] a. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of free Irwinia oleifera.

[0079] The activated *Ivania africanus* strain, previously cultured on Luria-Bertani (LB) solid medium, was transferred to LB liquid medium and incubated overnight at 37 °C and 220 rpm. 1 mL of the bacterial culture was then transferred to a 1.5 mL centrifuge tube and centrifuged at 5000 rpm for 5 min. The supernatant was removed, and the culture was resuspended in 1 mL of LB liquid medium with shaking. The absorbance (OD) was measured using a UV spectrophotometer. 600nm ), continuously dilute, and adjust the bacterial suspension to OD. 600nm =0.5, which means 0.5 McFarland turbidity, and the bacterial concentration is approximately 10. 8 At CFU / mL, serial dilutions were performed in a laminar flow hood to obtain 10... 6 CFU / mL bacterial suspension. A 12-well cell culture plate was used as the test system. A double-network hydrogel containing different concentrations of silver nanoparticles was added to each well. The plates were incubated at 37 ℃ for 24 h. Six parallel groups were set up, and the incubation was repeated for 6 days. The clarity of the bacterial suspension in the wells was observed, and the MIC and MBC concentrations were recorded. The experiment was repeated 10 times until the results were consistent. Results are shown below. Figure 7 As shown. From Figure 7As can be seen, when the MIC concentration of the dual-network hydrogel is the same as that of the nano-silver in Example 7, and the MBC concentration is the same as that of the nano-silver in Example 6, the results are consistent after repeating 10 times.

[0080] b. Evaluation of the biofilm inhibitory activity of *Ivermicularis*

[0081] American Irwinia was cultured in LB medium for 24 h, the bacterial suspension was centrifuged, and resuspended in physiological saline solution. The bacterial concentration was adjusted to 10. 6 CFU / mL is prepared for use. Add 2 mL of TSB medium (1×10⁻⁶) containing 2% sucrose to each well of a 6-well plate. 6 CFU / mL) was used to obtain free *Ivermicularia africanus*. Hydrogels containing different concentrations of silver nanoparticles were added to 12-well plates and incubated at 37 °C for 48 h (washed 2-3 times with PBS every 24 h with buffer changes). After staining with 1% crystal violet for 15 min and dissolving in 30% acetic acid for 30 min, the inhibition of biofilm growth was recorded. The results are as follows: Figure 8 As shown, the control group represents hydrogels without the addition of nano-silver. From Figure 8 It can be visually observed that the staining color becomes lighter as the concentration of nano-silver increases, indicating that the biomass of the biofilm decreases with the increase of nano-silver concentration, suggesting that the inhibitory effect on biofilm growth is enhanced with the increase of nano-silver gel concentration.

[0082] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a dual-network hydrogel loaded with silver nanoparticles, characterized in that, The method includes: (1) Preparation of polyvinyl alcohol / silver nano solution: Disperse silver nanoparticles in polyvinyl alcohol solution to obtain polyvinyl alcohol / silver nano solution; (2) Preparation of single-network hydrogel solution: Place gluconolactone solution in polyvinyl alcohol / nano silver solution to obtain single-network hydrogel solution; (3) Preparation of double network hydrogel solution: Sodium alginate solution and glycerol solution are mixed and stirred to obtain a mixture. The mixture is added to a single network hydrogel solution at a certain temperature and then stirred to obtain a double network hydrogel solution. (4) Preparation of double network hydrogel loaded with silver nanoparticles: Pour the double network hydrogel solution into a mold, let it stand for a period of time, seal it, and perform freeze-thaw cycles to obtain double network hydrogel loaded with silver nanoparticles. The method for synthesizing nano-silver in (1) is as follows: a silver nitrate solution with a concentration of 1 mg / mL is mixed with cell-free filtrate from liquid fermentation of oyster mushrooms at a volume ratio of 6:

4. The pH of the reaction system is adjusted to 11.2, the reaction temperature is 88 ℃, the reaction time is 30 min, the stirring rate is 80 rpm, the system after centrifugation is centrifuged at 12000 rpm for 30 min, the supernatant is discarded, and the system is washed repeatedly with distilled water 3 times to obtain pure nano-silver, which is then freeze-dried into nano-silver powder. The method for obtaining cell-free filtrate from the liquid fermentation of oyster mushrooms is as follows: Oyster mushrooms are cultured in PDA liquid medium at an inoculation rate of 3 mycelial blocks / 150mL medium at a culture temperature of 25℃ for 6 days. After the culture is completed, the mycelium of oyster mushrooms is removed by filtration through 6 layers of gauze to obtain cell-free filtrate. The culture medium formula is 200g potato chunks boiled for 20min, filtered, and then 20g glucose is added to make up to 1000mL. The concentration of the polyvinyl alcohol solution in (1) is 4~10 g / L; The freeze-thaw cycle process in (4) is as follows: the sealed hydrogel solution is frozen at -80°C for 0.5 to 4 hours, and then thawed at room temperature; The freeze-thaw cycle number in (4) is 2 to 5 times.

2. The preparation method according to claim 1, characterized in that, (1) The concentration of nano-silver in the polyvinyl alcohol / nano-silver solution is 200~800 μg / mL.

3. The preparation method according to claim 1, characterized in that, (2) The concentration of gluconolactone solution is 0.6~1.2 g / L.

4. The preparation method according to claim 1, characterized in that, (3) The temperature is 40~55℃.

5. The preparation method according to claim 1, characterized in that, (3) The concentration of sodium alginate solution is 2~8 g / L, and the volume ratio of sodium alginate solution to glycerol is 1:

1.

6. The preparation method according to claim 1, characterized in that, (3) The stirring temperature is 40~70 ℃, the stirring speed is 150~200 r / min, and the stirring time is 1~3 h.

7. A dual-network hydrogel loaded with silver nanoparticles, characterized in that, It is prepared by the method according to any one of claims 1 to 6.

8. A dual-network hydrogel loaded with silver nanoparticles as described in claim 7, characterized in that, This dual-network hydrogel is used in antibacterial and adsorbent materials.

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