PDA (at) Ag (at) Ag2S / SA / F68 / F127 antibacterial temperature-sensitive hydrogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of photoacoustic response antibacterial dressings, and discloses PDA (at) Ag (at) Ag2S / SA / F68 / F127 antibacterial temperature-sensitive hydrogel as well as a preparation method and application thereof.The PDA (at) Ag (at) Ag2S / SA / F68 / F127 antibacterial temperature-sensitive hydrogel can complete conversion of gel and sol under the condition of 4-60 DEG C, PDA (at) Ag (at) Ag2S nano-enzyme is constructed by means of an in-situ growth method, a PDA (at) Ag (at) Ag2S nano-composite material can generate electron-hole pairs under photoacoustic combination, then reactive oxygen species (ROS) is generated, and the antibacterial temperature-sensitive hydrogel can be used for preparing antibacterial temperature-sensitive hydrogel. The photoacoustic response antibacterial effect is realized. Meanwhile, PDA (at) Ag (at) Ag2S has peroxidase (POD)-like activity, and the material can catalyze endogenous hydrogen peroxide (H2O2) in a common wound microenvironment with the pH value of 7-8 to generate reactive oxygen species (ROS) with high toxicity, such as hydroxyl free radicals (. OH), so that efficient killing of various bacteria under photoacoustic combination is realized. Synthesis conditions are mild, and the process is simple, economical and feasible. The hydrogel has thermosensitivity, can resist inflammation, stop bleeding and relieve wound pain, does not loosen after absorbing seepage, is free of residues and does not adhere to a wound surface when being removed, and a new way is provided for developing novel medical dressings for treating drug-resistant bacterial infection wounds.

Description

Technical Field

[0001] This invention belongs to the field of photoacoustic responsive antibacterial dressing technology, specifically relating to a PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel, its preparation method, and its application. Background Technology

[0002] The emergence of bacterial resistance has become a major challenge in public health, making many common infected wounds difficult to treat effectively. Methicillin-resistant Staphylococcus aureus (MRSA) has become one of the leading causes of hospital-acquired infections. Furthermore, common pathogens such as Escherichia coli and Klebsiella pneumoniae also widely exhibit multidrug resistance to multiple antibiotics. Traditional treatments such as antibiotics and surgical debridement are proving inadequate for these infected wounds, necessitating the development of more comprehensive treatment strategies.

[0003] In recent years, the application of nanotechnology in the biomedical field has been continuously expanding, providing new ideas for anti-infective treatment. Nano-antibacterial platforms have shown broad application prospects by improving antibacterial efficiency and reducing toxic side effects. The combination of photothermal therapy (PTT) and sonodynamic therapy (SDT) has become an emerging synergistic antibacterial strategy, achieving multimodal and precise bacterial clearance by integrating photothermal effects and ultrasound activation mechanisms. This strategy utilizes the local high-temperature effect generated by photothermal agents under near-infrared light irradiation, and leverages ultrasound to activate sonosensitive agents to generate reactive oxygen species (ROS). The synergistic effect of these two methods not only significantly improves bactericidal efficiency but also overcomes the limitations of single therapies in terms of tissue penetration depth. Crucially, there is a significant "1+1>2" synergistic effect between PTT and SDT: photothermal pretreatment enhances bacterial membrane permeability, promoting sonosensitive agent uptake and ROS generation; while the deep penetration characteristics of ultrasound compensate for the shortcomings of photothermal therapy in tissue penetration, making this combined strategy particularly suitable for deep tissue infections and refractory infections associated with bacterial biofilms. This collaborative treatment model not only avoids the risk of drug resistance associated with traditional antibiotic use, but also provides a more efficient and safer solution for complex wound infections.

[0004] Polydopamine (PDA), as a biomimetic functional material, possesses excellent chemical stability, maintaining structural and performance stability in various complex chemical environments. Its abundant hydroxyl and amino functional groups endow PDA with multiple functions in catalysis, adsorption, and sensing. Furthermore, the catechol structure in PDA can generate H₂O₂ through electron transfer initiated by phenolic quinone isomerization, thus serving as an excellent carrier material. By immobilizing silver nanoparticles (Ag NPs) in situ on its surface, the antibacterial properties of the material can be further enhanced. The hydroxyl and amino groups on the PDA molecular chain act as anchoring sites, binding with silver ions and promoting the in-situ growth of silver nanoparticles on its surface through reduction. The resulting PDA@Ag composite material continuously releases silver ions (Ag NPs). + The latter possesses broad-spectrum antibacterial activity: on the one hand, it disrupts membrane integrity by binding to negatively charged components (such as lipopolysaccharides and proteins) on bacterial cell membranes, leading to an imbalance in substance exchange and bacterial death; on the other hand, it can penetrate into the bacterial cell interior, reacting with thiol-containing enzyme systems, interfering with metabolic processes and inhibiting protein synthesis. Although silver nanoparticles have sustained antibacterial potential, they are prone to aggregation in practical applications, which may not only weaken the antibacterial effect but also accumulate within cells, causing significant cytotoxicity. This toxicity intensifies with prolonged exposure time, reflecting the non-specificity of silver ion action; while attacking bacteria, it may also damage normal cells.

[0005] Silver sulfide (Ag₂S), as a silver-based semiconductor material, has attracted widespread attention due to its excellent conductivity and stability. Constructing an Ag₂S coating layer on the surface of PDA@Ag can effectively alleviate the cytotoxicity of silver ions while retaining its strong antibacterial properties. Normally, high concentrations of ROS induce oxidative stress, leading to a series of chain reactions such as protein and DNA damage. However, by synthesizing an Ag₂S modified layer, the biocompatibility of the material can be significantly improved, and cytotoxicity reduced. Furthermore, Ag₂S exhibits higher stability than elemental silver, and its nanoparticle structure easily adheres to various catalyst substrates. Under photoacoustic co-excitation, this novel acoustic sensitizer structure can effectively promote electron-hole pair separation, thereby generating hydroxyl radicals with strong oxidizing capabilities.

[0006] Thermosensitive hydrogels, with their temperature-responsive sol-gel transition properties, have become ideal candidate materials for medical dressings. Sodium alginate (SA)-based hydrogels possess multiple functions, including anti-inflammatory, hemostatic, antibacterial, antioxidant, and angiogenic properties, enabling them to systematically address various complex issues in the wound healing process. These hydrogels can be injected into the wound at body temperature and form a protective gel layer in situ, closely adhering to the wound and achieving controlled release of antibacterial components. By combining acoustically responsive antibacterial nanomaterials with thermosensitive hydrogels, it is expected to achieve synergistically enhanced antibacterial effects, providing an important technological pathway for the development of next-generation intelligent antibacterial dressings.

[0007] Current research has explored PDA-based nanocomposites, thermosensitive hydrogels, and their applications in the field of anti-infection. However, existing technologies still face the following key challenges: First, there are many single-functional designs, and a synergistic antibacterial material system that can simultaneously integrate multiple mechanisms such as photothermal, acoustic-dynamic, and thermosensitive self-adaptation, and is suitable for complex infected wounds, is still relatively lacking. Second, existing hydrogel dressings do not perform well in terms of responsiveness, antibacterial persistence, and wound adhesion, making it difficult to achieve efficient clearance and long-term protection against deep tissue infections and biofilms of multidrug-resistant bacteria. Therefore, developing a novel composite hydrogel dressing that combines highly efficient photoacoustic synergistic antibacterial activity, good biocompatibility, and thermosensitive self-adhesive properties is of great significance for advancing the clinical treatment of drug-resistant bacterial infections. Summary of the Invention

[0008] To address the limitations of existing treatment modalities in terms of their singularity and insufficient antibacterial efficacy, this invention aims to construct a nano-antibacterial system based on PDA@Ag@Ag2S, employing photothermal therapy (PTT) and sonodynamic therapy (SDT) as the primary mechanisms to develop a safe and efficient synergistic antibacterial strategy. First, polydopamine nanospheres (PDA) with redox properties are synthesized, and silver ions (Ag2S) with broad-spectrum antibacterial effects are introduced. + We systematically evaluated the anti-drug-resistant bacteria, broad-spectrum antibacterial properties, and biocompatibility of PDA@Ag@Ag2S / SA / F68 / F127 thermosensitive hydrogel with excellent biocompatibility. This material can generate reactive oxygen species through acoustic dynamics, effectively promoting the healing of bacterial-infected wounds.

[0009] The concept of this invention is as follows: Polydopamine (PDA) is a high-molecular-weight polymer formed by the self-polymerization of dopamine under alkaline conditions. PDA exhibits adhesive properties similar to mussel foot protein, spontaneously forming a uniform coating on various material surfaces. This adhesiveness makes it important for surface modification. PDA not only provides antibacterial properties but also achieves various functions such as catalysis, adsorption, and sensing through its abundant functional groups (e.g., hydroxyl and amino groups). Because PDA contains a large amount of catechols, it can generate H₂O₂ through electron transfer induced by phenolic quinone isomerization. Therefore, we selected PDA as a good carrier and modifier to enhance the antibacterial properties of the material by immobilizing an antibacterial agent (silver nanoparticles) on its surface. Silver ions (Ag) +Silver ions (AgNPs) possess broad-spectrum antibacterial activity. They can bind to negatively charged components of bacterial cell membranes (such as lipopolysaccharides and proteins), increasing cell membrane permeability, disrupting the exchange of substances between the inside and outside, and ultimately leading to bacterial death. They can also penetrate into bacterial cells, reacting with intracellular enzyme systems (especially those containing thiol groups), disrupting their activity, and thus inhibiting bacterial metabolic activity. They also interfere with bacterial protein synthesis. While AgNPs exhibit long-lasting antibacterial activity, they tend to form large aggregates. Although this has a smaller impact on antibacterial activity, it can have toxic side effects on human cells. Silver ions accumulate in large quantities within cells and are not easily eliminated. Over time, this cumulative effect gradually intensifies, leading to increased cytotoxicity. This indicates that the effects of silver ions are generally non-specific, meaning they can not only attack bacteria but also potentially cause toxicity to normal cells.

[0010] Silver sulfide (Ag₂S), as a silver-based semiconductor, has attracted much attention due to its excellent conductivity and stability. Modifying the surface of PDA@Ag with a layer of Ag₂S can reduce the cytotoxicity of silver ions while retaining its antibacterial ability. Ag@Ag₂S generates high levels of ROS, which induces oxidative stress and triggers a series of secondary reactions, such as protein damage and DNA damage. Synthesizing silver sulfide on silver can increase its biocompatibility, thereby mitigating this toxicity. Ag₂S is more stable than Ag, and the morphology of silver-based semiconductors is mostly nanoparticles, which is beneficial for adhesion to catalyst surfaces with different structures. Under PTT and SDT excitation, this novel structure effectively promotes electron-hole separation and gives it a strong redox potential. The separated holes can react with water molecules independently of oxygen to generate reactive oxygen species (hydroxyl radicals).

[0011] The technical solution of the present invention is as follows: This invention provides a PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel. The size of this catalytic antibacterial material is between 300-400 nm, and it is a rough-surfaced sphere.

[0012] This invention also provides the application of PDA@Ag@Ag2S / SA / F68 / F127 photoacoustic responsive antibacterial thermosensitive material in the inactivation of methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum β-lactamase-producing Escherichia coli (ESBL). The conditions for its inactivation of MRSA and ESBL are as follows: the hydrogel is added to a bacterial solution containing MRSA and ESBL, and the bacterial solution is placed in an 808 nm near-infrared laser therapy device (0.8-1.2 W / cm²). 2 Combined with ultrasound (1.5-2.5 W / cm) 2 Irradiate for 10-30 minutes.

[0013] Furthermore, in one embodiment of the above application: the amount of PDA@Ag@Ag2S / SA / F68 / F127 hydrogel used is 100-150 μg, the volume of MRSA and ESBL bacterial suspension is 200-300 μL, and the concentration of the bacterial suspension is 1×10⁻⁶. 5 -1×10 7 CFU / mL. In other application examples, the dosage can be scaled up or reduced by the same factor as described above.

[0014] This invention also provides a method for preparing a PDA@Ag@Ag2S / SA / F68 / F127 photoacoustic catalytic antibacterial thermosensitive hydrogel, comprising the following steps: S1. PDA Synthesis Prepare a solution of ethanol and ammonia in a specific ratio. Slowly add dopamine hydrochloride (DA) dissolved in deionized water or a buffer solution. The reaction is usually carried out at room temperature or under appropriate heating (25-55 °C) for 10-14 hours.

[0015] S2. Synthesis of PDA@Ag Dissolve PDA in deionized water, typically at a concentration of 8-18 mg / mL. Dissolve silver nitrate in deionized water, typically at a concentration of 0.05-0.15 mol / L, and add 2.5-3.5 mL of ammonia solution dropwise, observing the color change. Finally, mix the polydopamine base with the silver ammonia solution. The reaction is usually carried out with stirring at room temperature for 1-6 hours.

[0016] S3. Synthesis of PDA@Ag@Ag2S Repeat the above PDA@Ag synthesis method, stirring for a certain period of time at room temperature in the dark. Add 45-75 mg of sodium sulfide nonahydrate (Na2S·9H2O), mix well, and stir again in the dark for 4-6 hours before stopping the reaction to obtain a brownish-black suspension. Centrifuge the obtained suspension at 8000-12000 rpm for 7-10 minutes, wash 1-2 times with deionized water and 2-3 times with anhydrous ethanol, and dry in an oven to obtain PDA@Ag@Ag2S powder.

[0017] Synthesis of S4: PDA@Ag@Ag2S / SA / F68 / F127 hydrogel Weigh 20-45% (w / w) of Pluronic F-127, 1-10% (w / w) of Pluronic F-68, 15-25% (w / w) of sodium alginate (SA), and 200 μg / mL-300 μg / mL of PDA@Ag@Ag2S and add them to deionized water. Prepare PDA@Ag@Ag2S / SA / F68 / F127 composite hydrogels with different compositions and phase transition temperatures using a one-pot method.

[0018] Further, the specific steps of PDA synthesis in step S1 are as follows: First, measure 450-550 mL of deionized water, 180-220 mL of anhydrous ethanol, and 2.5-3.5 mL of ammonia water into a beaker, and heat and stir at 28-32 ℃ for 25-35 min, which is recorded as solution ①. Then, weigh 2.0-4.0 g of dopamine hydrochloride, dissolve it in 40-60 mL of deionized water, and slowly add it dropwise to the above solution ①. After stirring in the dark for 20-28 h, centrifuge at 8000-12000 r / min for 8-12 min. Wash the obtained product alternately with deionized water and anhydrous ethanol 2-4 times, and dry at room temperature for 10-14 h to obtain PDA powder.

[0019] Further, the specific steps for synthesizing PDA@Ag in step S2 are as follows: Take 70-110 mg of silver nitrate and add deionized water to prepare a silver nitrate solution with a concentration of 0.05-0.15 mol / L. Add 2.5-3.5 mL of ammonia water dropwise to the silver nitrate solution until a brown precipitate appears in the system and it becomes clear again. Add 5-12 mL of PDA dispersion with a concentration of 8-18 mg / mL to the clear solution. Stir for 3-8 hours at room temperature in the dark. After the reaction is complete, centrifuge at 8000-12000 rpm for 8-12 minutes. Wash the centrifuged product with deionized water and anhydrous ethanol 2-4 times each, and then dry it in an oven at 55-65℃ for 6-12 hours.

[0020] Further, the specific steps for synthesizing PDA@Ag@Ag2S in step S3 are as follows: Weigh 35-55 mg of PDA@Ag and 45-75 mg of sodium sulfide nonahydrate (Na2S·9H2O), dissolve each in 15-25 mL of deionized water, mix, and stir under light-protected conditions for 3-8 hours to obtain a brownish-black suspension. Centrifuge the suspension at 8000-12000 rpm for 8-12 minutes, wash with deionized water 1-2 times, wash with anhydrous ethanol 2-3 times, and finally dry in an oven at 50-70 ℃ for 6-12 hours.

[0021] Further, the specific steps for synthesizing the PDA@Ag@Ag2S / SA / F68 / F127 hydrogel in step S4 are as follows: The composite hydrogel is prepared using a cooling method. Weigh 20-45% (w / w) of Pluronic F-127, 1-10% (w / w) of Pluronic F-68, and 15-25% (w / w) of sodium alginate (SA) into deionized water, followed by the addition of 150-350 μg / mL of PDA@Ag@Ag2S nanomaterials. Transfer the mixture to a 2-8℃ environment and react for 10-24 hours until all components are completely dissolved and a homogeneous gel is formed, thus obtaining the PDA@Ag@Ag2S / SA / F68 / F127 composite hydrogel.

[0022] A multifunctional hydrogel, PDA@Ag@Ag2S / SA / F68 / F127, utilizing photothermal and acoustic dynamics to generate reactive oxygen species (ROS) for antibacterial and wound-healing purposes, was developed for treating wounds infected with drug-resistant bacteria in mice. The PDA@Ag@Ag2S nanocomposite material generates electron-hole pairs under photoacoustic catalysis, leading to the production of ROS and achieving photoacoustic dynamic antibacterial activity. Simultaneously, the semiconductor properties of Ag2S endow it with peroxidase-like (POD) activity, catalyzing the decomposition of hydrogen peroxide (H2O2) to produce hydroxyl radicals (•OH), further enhancing the antibacterial effect. Furthermore, the introduction of sodium alginate (SA) not only improves the biocompatibility of the hydrogel but also synergistically enhances the antibacterial effect through its antibacterial properties. Encapsulating PDA@Ag@Ag2S within the hydrogel ensures uniform distribution within the wound and provides wound moisturizing. PDA@Ag@Ag2S / SA / F68 / F127 hydrogel exhibits excellent thermosensitivity. It remains liquid at low temperatures for easy injection and application, and rapidly transforms into a gel upon contact with body temperature, adhering tightly to the wound surface to form a protective barrier and effectively prevent bacterial invasion. This property makes it particularly suitable for wounds with complex shapes, such as diabetic foot ulcers. PDA@Ag@Ag2S / SA / F68 / F127 hydrogel also demonstrates good biocompatibility and no significant toxicity to cells. Furthermore, the hydrogel absorbs wound exudate, keeping the wound moist and promoting healing.

[0023] Compared with existing technologies, the present invention has the following advantages: This invention proposes a PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel. By integrating photodynamic therapy and utilizing the reversible sol-gel phase transition behavior, self-adaptability, and anti-inflammatory and hemostatic effects of the thermosensitive hydrogel, it can spontaneously form a three-dimensional network gel structure under body temperature conditions, perfectly conforming to wounds of various complex shapes and achieving tight coverage. This provides a novel, highly efficient, safe, and intelligent antibacterial dressing suitable for the treatment of wounds infected with drug-resistant bacteria.

[0024] 1. The method for preparing PDA@Ag@Ag2S / SA / F68 / F127 hydrogel provided by the present invention has significant advantages such as mild synthesis conditions, simple and easy process route, and strong economic feasibility.

[0025] 2. The PDA@Ag@Ag2S / SA / F68 / F127 hydrogel provided by this invention can achieve synergistic antibacterial effects of self-activated enzymatic reaction and photoacoustic catalysis, reducing side effects while improving antibacterial efficiency.

[0026] 3. The PDA@Ag@Ag2S / SA / F68 / F127 hydrogel provided by this invention is thermosensitive and, as a self-activated enzymatic reaction platform, can also alleviate wound pain. It absorbs wound exudate without loosening, breaking, or leaving residue. Compared to traditional dressings, this hydrogel does not adhere to the wound surface upon removal, avoiding secondary damage.

[0027] This hydrogel can undergo gel-sol transformation at 4-37 °C. PDA@Ag@Ag2S nanozymes were constructed using an in-situ growth method. PDA@Ag@Ag2S generates reactive oxygen species for antibacterial activity under photoacoustic stimulation. The preparation method is mild, simple, and economically feasible. This hydrogel is thermosensitive, can reduce wound pain, absorbs exudate without crumbling or leaving residue, and does not adhere to the wound surface upon removal. It was used with an 808 nm near-infrared laser (0.8-1.2 W / cm²). 2 Combined with ultrasound (1.5-2.5 W / cm) 2 Under irradiation conditions of 10-30 min, it has a good inactivation effect on methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamase-producing Escherichia coli, providing a new approach for the treatment of wounds infected with drug-resistant bacteria. Attached Figure Description

[0028] Figure 1 The XRD pattern of the nano-antibacterial agent PDA@Ag@Ag2S prepared in Example 1; Figure 2 TEM images of the nano-antibacterial agent PDA@Ag@Ag2S prepared in Example 1: (a) PDA, (b) PDA@Ag, and (c) PDA@Ag@Ag2S. Figure 3 Thermosensitive and injectable properties of PDA@Ag@Ag2S / SA / F68 / F127 hydrogel, (a) and (b) show the sol-gel transition properties of PDA@Ag@Ag2S / SA / F68 / F127 hydrogel, and (c) shows the injectability of PDA@Ag@Ag2S / SA / F68 / F127 hydrogel; Figure 4PDA@Ag@Ag2S POD enzyme activity assay: (a) enzyme activity assay of PDA@Ag@Ag2S at different pH levels; (b) enzyme activity assay at different concentrations; (c) enzyme activity assay of different materials. Figure 5 Antibacterial properties of PDA@Ag@Ag2S / SA / F68 / F127 hydrogel: (a) Antibacterial plate plots of different materials irradiated by photoacoustic radiation, (b) Photoacoustic catalytic antibacterial rate; Figure 6 The broad-spectrum antibacterial properties of PDA@Ag@Ag2S / SA / F68 / F127 hydrogel are shown in the following figures: (a) broad-spectrum antibacterial plate plot, and (b) photoacoustic catalytic broad-spectrum antibacterial rate. Figure 7 The application of PDA@Ag@Ag2S / SA / F68 / F127 hydrogel to the healing of MRSA wound infection in mice: (a) is a graph of mouse wound healing, and (b) is the wound healing rate of mice. Detailed Implementation

[0029] To better understand the content of this invention, specific implementation examples will be used to further illustrate the invention below. The following embodiments are based on the technology of this invention and include detailed implementation methods and operating steps; however, the scope of protection of this invention is not limited to the following embodiments. Unless otherwise specified, the experimental methods used in this invention are all conventional methods, and the experimental equipment, materials, reagents, etc., used are all commercially available.

[0030] Example 1 Synthesis of S1.PDA First, measure 450-550 mL of deionized water, 180-220 mL of anhydrous ethanol, and 2.5-3.5 mL of ammonia water into a beaker, and heat and stir at 28-32 ℃ for 25-35 min, which is recorded as solution ①. Then, weigh 2.0-4.0 g of dopamine hydrochloride, dissolve it in 40-60 mL of deionized water, and slowly add it dropwise to solution ① above. After stirring in the dark for 20-28 h, centrifuge at 8000-10000 r / min for 8-12 min. Wash the obtained product alternately with deionized water and anhydrous ethanol 2-4 times, and dry at room temperature for 10-14 h to obtain PDA powder.

[0031] Synthesis of S2.PDA@Ag Dissolve 70-110 mg of silver nitrate in deionized water to form a silver nitrate solution. Slowly add ammonia to the silver nitrate solution until a brown substance is observed and the solution becomes clear again. Add 5-12 mL of 8-18 mg / mL PDA to this clear solution. Stir at room temperature in the dark for 4-6 hours. After the reaction is complete, centrifuge at 8000-12000 rpm for 8-12 minutes. Wash the centrifuged product 2-4 times each with deionized water and anhydrous ethanol, then dry it in an oven at 55-65℃ for 6-12 hours.

[0032] S3. Synthesis of PDA@Ag@Ag2S Weigh 35-55 mg of PDA@Ag and 45-75 mg of sodium sulfide nonahydrate (Na2S·9H2O), dissolve them separately in 15-25 mL of deionized water, mix thoroughly, and stir in the dark for 3-8 hours to stop the reaction, obtaining a brownish-black suspension. Centrifuge the obtained suspension at 8000-12000 rpm for 10 minutes, wash it sequentially with deionized water 1-2 times, and then with anhydrous ethanol 2-3 times. Finally, dry it in an oven at 50-70℃ for 6-12 hours.

[0033] S4: Synthesis of PDA@Ag@Ag2S / SA / F68 / F127 hydrogel.

[0034] Weigh 20-45% (w / w) of Pluronic F-127, 1-10% (w / w) of Pluronic F-68, and 15-25% (w / w) of sodium alginate (SA) and add them to deionized water. Then, add different amounts of PDA@Ag@Ag2S. Transfer the resulting mixture to a refrigerator at 2-8 °C and react for 10-24 h until F68, F127, and SA can be completely dissolved in deionized water to prepare a PDA@Ag@Ag2S / SA / F68 / F127 composite hydrogel.

[0035] Example 2 The crystal structure of the samples in Example 1 was analyzed by XRD. X-ray diffraction data of all samples were acquired using a LabX XRD-6000 X-ray diffractometer (Shimadzu International Trading Co., Ltd., Japan). The experiment used Cu target radiation (λ = 0.15405 nm) as the X-ray source and scanned the crystal structure of the materials at a speed of 2° / min within the 2θ range of 6-80°. Figure 1The presence of characteristic peaks for Ag and Ag₂S, along with the observation of major Ag diffraction peaks (111), (200), (220), and (311) in the XRD pattern, confirms the successful preparation of PDA@Ag. Similarly, the observation of major Ag₂S diffraction peaks (111), (-112), (-121), and (031) in the XRD pattern further confirms the successful preparation of PDA@Ag@Ag₂S.

[0036] Example 3 The morphology and microstructure of the samples in Example 1 were analyzed by TEM. The TEM images were taken using a JEM-2100 transmission electron microscope (JEOL Ltd.). Figure 2 As can be seen, a single PDA is a nanoparticle with a smooth surface and a spherical morphology of about 150-200 nm; after loading Ag and Ag2S nanoparticles, it becomes a sphere with a rough surface. The Ag and Ag2S nanoparticles are smaller in size, relatively uniform, about 20-30 nm, and are evenly dispersed.

[0037] Example 4 Using TMB (3,3′,5,5′-tetramethylbenzidine) as the oxidizing substrate, the POD enzyme-like activity of the composite material was determined in sodium acetate buffer. PDA@Ag@Ag2S exhibited significant POD enzyme catalytic performance at pH=7. This type of material can catalyze the generation of highly toxic reactive oxygen species (ROS) such as hydroxyl radicals (·OH) from endogenous hydrogen peroxide (H2O2) in neutral pH environments (such as the common wound microenvironment), achieving highly efficient killing of various bacteria.

[0038] Example 5 The samples from Example 1 were placed in glass vials. The ambient temperature was varied. At 4-6 °C, both the SA / F68 / F127 hydrogel and the PDA@Ag@Ag2S / SA / F68 / F127 hydrogel were highly fluid liquids. When the temperature rose to 37 °C, both hydrogels immediately transformed into gel-like solids. Changing the proportion of F127 altered the gelation temperature of the hydrogels, which ranged from 20-37 °C. Furthermore, neither hydrogel flowed under gravity and remained in a gel state. This indicates that both hydrogels can remain in the wound area and will not detach due to gravity. It was also noted that when the temperature dropped to 4-6 °C, both hydrogels reverted to a liquid state, indicating that the F68 / F127 hydrogel and the PDA@Ag@Ag2S / SA / F68 / F127 hydrogel possess reversible sol-gel transition properties. Figure 4 a, b). The SA / F68 / F127 hydrogel can be smoothly extruded from the syringe at room temperature without resistance and can form an "A" shape, indicating that the hydrogel has excellent injectability. Figure 4c).

[0039] Example 6 Using methicillin-resistant Staphylococcus aureus (MRSA), the most common pathogenic bacterium among drug-resistant bacteria, as a model strain, the antibacterial activity of the prepared composite hydrogel under visible light irradiation was studied using the plate count method. The bacterial suspension concentration was adjusted to 1×10⁻⁶. 5 -1×10 7 CFU / mL was used as the initial bacterial concentration for photoacoustic catalysis. The total reaction volume was 1-4 mL, containing 100-300 μL of bacterial suspension, 50-200 μL of composite hydrogel (1-4 mg / mL) aqueous solution, and the remaining volume was supplemented with PBS buffer. The mixed solution was heated in an 808 nm near-infrared laser therapy device (0.8-1.2 W / cm²). 2 Combined with ultrasound (1.5-2.5 W / cm) 2 Irradiate for 10-30 min. After the reaction, dilute 500-2000 times and take 2-100 μL to spread on LB solid medium. Incubate at 35-38 ℃ for 18-30 h. Repeat each experiment three times and calculate the photoacoustic catalytic antibacterial rate.

[0040] Observe the bacterial morphology regularly, and once the colonies reach the ideal size, count the number of colonies on each culture medium. From Figure 5 It can be seen that the number of colonies in the PBS group did not decrease significantly under the four conditions, and even showed negative growth, indicating that photoacoustic alone does not have a significant impact on bacteria; MRSA and other bacterial species can achieve a sterilization rate of over 99% within 10-30 minutes under the action of PTT and SDT.

[0041] Example 7 To further explore the universality of the antibacterial activity of PDA@Ag@Ag2S / SA / F68 / F127, we selected nine representative microorganisms (including Gram-negative bacteria, Gram-positive bacteria, and fungi) to analyze their antibacterial spectrum. The concentration of each bacterial suspension was adjusted to 1×10⁻⁶. 5 -1×10 7 CFU / mL was used as the initial bacterial concentration for photocatalysis. The total reaction system was 1-4 mL, containing 100-300 μL of bacterial suspension, 50-200 μL of composite hydrogel (1-4 mg / mL) aqueous solution, and the remainder was supplemented to the appropriate volume with PBS buffer. The mixed solution was heated in an 808 nm near-infrared laser therapy device (0.8-1.2 W / cm²). 2 Combined with ultrasound (1.5-2.5 W / cm) 2Irradiate for 10-30 min. After the reaction, dilute 500-2000 times, and spread 20-100 μL onto the culture medium. Incubate at 35-38 ℃ for 18-30 h. Each experiment is repeated three times, and the photoacoustic catalytic antibacterial rate is calculated. The antibacterial results are as follows: Figure 6 As shown in a and 6b, under US+Light conditions, the PBS control group did not show significant antibacterial activity. However, the experimental group treated with PDA@Ag@Ag2S / SA / F68 / F127 showed significant killing effects on the vast majority of tested bacterial species, thus confirming that this PTT / SDT synergistic strategy has a broad antibacterial spectrum.

[0042] Example 8 To evaluate the antibacterial effect and wound-healing promoting effect of the PDA@Ag@Ag2S / SA / F68 / F127 composite material in vivo, this study used a mouse wound model of MRSA infection. Mice were acclimatized to their environment through adaptive feeding. After anesthesia, a circular wound with a diameter of 8-9 mm was made on the upper midline of the back, cutting through the full thickness of the skin to the fascia layer. The wound was then wrapped with gauze to establish a hypoxic environment and ensure the establishment of a suitable recipient. MRSA Infected wound model. Mice were randomly divided into four groups and treated with PDA@Ag@Ag2S / SA / F68 / F127 hydrogel under the following conditions: no photoacoustic, light alone, sound alone, and a combination of photoacoustic and light-sound, respectively. Wounds were photographed every other day to record the wound healing process. Figure 7 a). Representative wound photographs taken on days 0, 2, 4, 6, and 8 were selected for comparative analysis. Figure 7 b). As shown in the figure, the wounds in the PDA@Ag@Ag2S / SA / F68 / F127 hydrogel group were nearly healed after 8 days of treatment. ImageJ software was used to analyze the wound area and calculate the wound healing rate. The quantitative analysis results are as follows: Figure 7 As shown in b, on day 9, the PDA@Ag@Ag2S / SA / F68 / F127 hydrogel achieved a wound healing rate of up to 90% in the photoacoustic treatment group, which was higher than that of other treatment groups, demonstrating the best wound healing efficiency.

[0043] The above description is merely 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 PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel, characterized in that, The antibacterial thermosensitive hydrogel has a size between 300-400 nm and is a rough-surfaced sphere composed of PDA@Ag@Ag2S, sodium alginate (SA), Pluronic F-68 (F68), and Pluronic F-127 (F127).

2. A method for preparing the PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel as described in claim 1, characterized in that, The process includes the following steps: Weigh 20-45% (w / w) of Pluronic F-127, 1-10% (w / w) of Pluronic F-68, and 15-25% (w / w) of sodium alginate (SA) into deionized water, then add 150-350 μg / mL of PDA@Ag@Ag2S nanomaterials. Transfer the mixture to a 2-8 ℃ environment and react for 10-24 hours until all components are completely dissolved and a uniform gel is formed, thus obtaining the PDA@Ag@Ag2S / SA / F68 / F127 composite hydrogel.

3. The preparation method of the PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel according to claim 2, characterized in that, After stirring PDA@Ag at room temperature in the dark for a certain period of time, sodium sulfide nonahydrate (Na2S·9H2O) was added, and after mixing evenly, the mixture was stirred in the dark for 4-6 hours. After centrifugation, washing, and drying, PDA@Ag@Ag2S powder was obtained.

4. The preparation method of the PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel according to claim 3, characterized in that, Dissolve PDA in deionized water, dissolve silver nitrate in deionized water and add ammonia dropwise, mix the polydopamine base with the silver ammonia solution, and stir at room temperature for 1-6 hours.

5. The preparation method of the PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel according to claim 4, characterized in that, Prepare a solution by mixing ethanol and ammonia in a certain ratio, and slowly add dopamine hydrochloride (DA) dissolved in deionized water or buffer solution. React for 10-14 hours at room temperature or under heating conditions of 25-55°C.

6. The method for preparing the PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel according to claim 2 or 5, characterized in that, The specific steps for synthesizing PDA are as follows: Measure 450-550 mL of deionized water, 180-220 mL of anhydrous ethanol, and 2.5-3.5 mL of ammonia into a beaker, heat and stir at 28-32℃ for 25-35 min, and record this as solution ①; Weigh 2.0-4.0 g of dopamine hydrochloride, dissolve it in 40-60 mL of deionized water, and slowly add it dropwise to solution ①. Stir in the dark for 20-28 h, then centrifuge at 8000-12000 r / min for 8-12 min. Wash the obtained product alternately with deionized water and anhydrous ethanol 2-4 times, and dry at room temperature for 10-14 h to obtain PDA powder.

7. The method for preparing the PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel according to claim 2 or 4, characterized in that, The specific steps for synthesizing PDA@Ag are as follows: Take 70-110 mg of silver nitrate, add deionized water to prepare a silver nitrate solution with a concentration of 0.05-0.15 mol / L, add 2.5-3.5 mL of ammonia water dropwise to the silver nitrate solution until a brown precipitate appears in the system and turns clear again, add 5-12 mL of PDA dispersion with a concentration of 8-18 mg / mL to the clear solution, stir for 3-8 hours at room temperature in the dark, after the reaction is completed, centrifuge at 8000-12000 rpm for 8-12 minutes, wash the centrifuged product with deionized water and anhydrous ethanol 2-4 times each, and then dry in an oven at 55-65 ℃ for 6-12 hours.

8. The method for preparing the PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel according to claim 2 or 3, characterized in that, The specific steps for synthesizing PDA@Ag@Ag2S are as follows: Weigh 35-55 mg of PDA@Ag and 45-75 mg of sodium sulfide nonahydrate (Na2S·9H2O), dissolve each in 15-25 mL of deionized water, mix and stir for 3-8 hours under light-protected conditions to obtain a brown-black suspension. Centrifuge the suspension at 8000-12000 rpm for 8-12 minutes, wash with deionized water 1-2 times and anhydrous ethanol 2-3 times, and finally dry in an oven at 50-70 ℃ for 6-12 hours.

9. The application of the PDA@Ag@Ag2S / SA / F68 / F127 antibacterial thermosensitive hydrogel as described in claim 1 in the inactivation of methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum β-lactamase-producing Escherichia coli (ESBL), characterized in that, The application conditions are as follows: The hydrogel is added to a bacterial solution containing MRSA and ESBL, and the bacterial solution is placed in an 808 nm near-infrared laser therapy device (0.8-1.2 W / cm²). 2 Combined with ultrasound (1.5-2.5 W / cm) 2 Irradiate for 10-30 minutes.

10. The application according to claim 9, characterized in that, In one embodiment of the application: the amount of PDA@Ag@Ag2S / SA / F68 / F127 hydrogel used is 100-150 μg, the volume of MRSA and ESBL bacterial suspension is 200-300 μL, and the concentration of the bacterial suspension is 1×10⁻⁶. 5 -1×10 7 CFU / mL; in other application examples, the dosage ratio described above can be scaled up or reduced by the same factor.

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