Preparation and application of a diagnosis and treatment integrated antibacterial hydrogel dressing

Abstract

This invention discloses the preparation and application of an integrated antibacterial hydrogel dressing for diagnosis and treatment. The preparation method of the integrated antibacterial hydrogel dressing includes: mixing a polyvinyl alcohol solution and a sodium alginate solution to prepare a spinning solution; adding gold nanoparticles; and then using wet spinning technology to obtain hydrogel fibers, which are woven into a dressing. After freeze-drying, the dressing is immersed in a bromothymol blue solution and then vacuum dried to obtain the dressing. In the dressing, bromothymol blue can achieve real-time visual detection of bacterial infection by sensing changes in the pH of the wound; the gold nanoparticles, with their unique bipyramidal needle-like structure and excellent photothermal properties, exhibit highly efficient antibacterial activity with or without laser assistance; and wet spinning imparts high porosity and excellent water vapor permeability to the dressing, providing a suitable microenvironment for wound healing.

Description

Technical Field

[0001] This invention relates to the field of biomedical dressings, specifically to the preparation and application of an integrated diagnostic and therapeutic antibacterial hydrogel dressing. Background Technology

[0002] Iatrogenic bacterial infections caused by wound infections seriously threaten patients' lives and health, and are a key challenge in clinical trauma treatment. Commonly used pathogen detection methods (such as plate culture and polymerase chain reaction) have drawbacks such as complex operation and long testing cycles, easily delaying optimal diagnosis and treatment. In terms of infection treatment, the clinical approach often uses antibiotics combined with fabric dressings. This not only easily induces bacterial resistance, leading to decreased antibacterial efficacy, but also, traditional fabric dressings have poor breathability and are prone to fluid accumulation, hindering wound healing. It is worth noting that pH-sensitive detection technology can rapidly capture minute changes in pH caused by bacterial metabolism, enabling rapid identification of wound infections; metal nanoparticles possess highly efficient antibacterial properties and can replace traditional antibiotics to reduce the development of resistance; wet spinning technology can achieve stable loading of various functional components while effectively improving the breathability of dressings. However, most existing antibacterial dressings do not integrate these three key technologies, possessing only a single antibacterial function and lacking rapid infection detection capabilities. They cannot achieve synergistic linkage between "infection detection and antibacterial treatment," failing to meet the actual clinical needs for integrated trauma diagnosis and treatment.

[0003] According to published patents and related literature, the composite application of natural polymer materials and nanoparticles can effectively improve the breathability, moisturizing properties, mechanical properties, and antibacterial properties of dressings, while reducing preparation costs and promoting wound healing, offering advantages for large-scale production and market promotion. However, existing technologies generally suffer from the following shortcomings in such composite dressings: First, the photothermal conversion efficiency of the nano-antibacterial materials used (such as gold nanorods) is limited, and their antibacterial ability is weak without laser assistance, making it difficult to achieve efficient and stable antibacterial effects; second, the loading stability of pH-responsive indicators in the dressing structure is insufficient, making it impossible to achieve continuous visual monitoring of the infection process; third, dressings prepared using traditional casting-type hydrogel processes have low porosity and poor water vapor permeability, which is not conducive to the establishment of a wound healing microenvironment. These defects make it difficult for existing composite dressings to achieve a synergistic closed loop of "infection detection—antibacterial treatment—efficacy monitoring," and there is still considerable room for optimization in their preparation process and diagnostic and therapeutic synergy, requiring further research and improvement.

[0004] Therefore, developing a novel integrated diagnostic and therapeutic antibacterial hydrogel dressing has significant clinical importance and practical application value. Summary of the Invention

[0005] In view of the problems existing in the background technology, the present invention provides a preparation and application of an integrated diagnostic and therapeutic antibacterial hydrogel dressing.

[0006] This invention is implemented through the following technical solutions: The first aspect of this invention provides a method for preparing an integrated diagnostic and therapeutic antibacterial hydrogel dressing, comprising the following steps: (1) Mix polyvinyl alcohol solution with sodium alginate solution to obtain spinning solution; (2) Add gold nanobipyramidal particles to the spinning solution, stir and mix well to obtain a mixed solution; (3) The mixed solution is extruded into a coagulation bath containing calcium chloride and boric acid by wet spinning, and after cross-linking and solidification, hydrogel fiber filaments are obtained, which are then woven into dressings and freeze-dried. (4) After the freeze-dried dressing is swollen and moistened with a buffer solution, it is soaked in bromothymol blue solution and vacuum dried to obtain the integrated antibacterial hydrogel dressing.

[0007] In some embodiments of the present invention, the polyvinyl alcohol solution contains 10%–20% polyvinyl alcohol by mass; the sodium alginate solution contains 1%–5% sodium alginate by mass; and the volume ratio of the polyvinyl alcohol solution to the sodium alginate solution is 2:1–8:1. Polyvinyl alcohol imparts good flexibility and film-forming properties to the fiber, while sodium alginate provides sites for ionic crosslinking with calcium ions in the coagulation bath. The synergistic optimization of the concentrations and ratios of both ensures the spinnability of the spinning solution and the final mechanical properties of the fiber.

[0008] In some embodiments of the present invention, the volume ratio of the gold nanobipyramidal particles to the spinning solution is 0.5:10 to 2:10; and the concentration of bromothymol blue in the bromothymol blue solution is 0.3 to 0.5 mg / mL.

[0009] In some embodiments of the present invention, a solubilizer is used during the dissolution of the bromothymol blue solution. The solubilizer is selected from one or more of PEG 2000, PEG 4000, PVP 10000, PVP 24000, and PVP K30; the pH of the buffer solution in step (4) is 7-9. Swelling and wetting the freeze-dried dressing under alkaline buffer conditions helps the bromothymol blue to be uniformly loaded into the fiber matrix in its initial blue state, establishing a sensitive color change benchmark for subsequent visual detection of bacterial infection.

[0010] In some embodiments of the present invention, the needle aperture of wet spinning in step (3) is 18–24 G, and the spinning speed is 5–20 mm / min. By adjusting the above parameters, the fiber diameter and pore structure can be effectively adjusted, thereby optimizing the mechanical properties and air permeability of the dressing.

[0011] In some embodiments of the present invention, the temperature of vacuum drying in step (4) is 30 to 60°C.

[0012] In some embodiments of the present invention, the gold nanoparticles are prepared by a seed growth method, comprising: dissolving hexadecyltrimethylammonium chloride and citric acid monohydrate in tetrachloroauric acid solution, adding sodium borohydride solution, heating and stirring to obtain a seed solution; dissolving hexadecyltrimethylammonium bromide in deionized water by heating, adding tetrachloroauric acid solution, silver nitrate solution, hydrochloric acid solution and ascorbic acid solution in sequence, mixing evenly to obtain a growth solution; adding the seed solution to the growth solution, stirring and mixing evenly, and allowing to stand to obtain the gold nanoparticles.

[0013] Furthermore, in the preparation of the seed solution, the concentration of hexadecyltrimethylammonium chloride was 0.016 g / mL, the concentration of citric acid monohydrate was 0.0012 g / mL, and the amount of sodium borohydride solution added per 10 mL of tetrachloroauric acid solution was 250–270 μL. The heating temperature was 80–95 °C, and the stirring time was 60–90 min. In the preparation of the growth solution, the concentration of hexadecyltrimethylammonium bromide was 0.0364 g / mL, the dissolution temperature was 30–60 °C, and 0.5 mL of 10 mM tetrachloroauric acid solution, 0.1 mL of 10 mM silver nitrate solution, 0.2 mL of 1 M hydrochloric acid solution, and 80 μL of 100 mM ascorbic acid solution were added sequentially to each 10 mL of deionized water. The amount of seed solution added per 10 mL of growth solution was 80–120 μL, and the standing time was 2–12 minutes. h; The obtained gold nanobipyramidal particles have a particle size of 140 ~ 170 nm and can be stored at 4℃ for 1 ~ 14 days.

[0014] A second aspect of the present invention provides a therapeutic antibacterial hydrogel dressing, wherein the dressing is a wet-spun fiber membrane; the fiber membrane comprises hydrogel fibers formed by crosslinking sodium alginate and polyvinyl alcohol, and gold nanobipyramidal particles and bromothymol blue dispersed in the hydrogel fibers; the particle size of the gold nanobipyramidal particles is 140-170 nm.

[0015] A third aspect of the present invention provides the application of the aforementioned integrated diagnostic and therapeutic antibacterial hydrogel dressing in the preparation of wound dressings.

[0016] The beneficial effects of this invention are: 1. The integrated antibacterial hydrogel dressing provided by this invention achieves a closed-loop diagnosis-treatment-monitoring system. Bromothymol blue, as a pH-responsive indicator, can sense pH changes caused by bacterial metabolism in the lesion area, enabling real-time naked-eye visualization of the wound infection level. Gold nanoparticles, with their unique bipyramidal needle-like structure, exhibit superior autonomous antibacterial activity compared to gold nanorods of the same concentration even without laser irradiation. After 808 nm laser irradiation, their photothermal conversion efficiency is further enhanced, enabling efficient bacterial killing. Bromothymol blue can simultaneously reflect the dynamic changes in the infection status during treatment. These three elements work synergistically to form a complete closed loop of infection detection, antibacterial treatment, and efficacy monitoring, effectively solving the problem of disconnect between diagnosis and treatment in existing diagnostic and treatment technologies.

[0017] 2. The gold nanoparticles are effectively encapsulated by hydrogel fibers, reducing the cytotoxicity of free nanoparticles; the photothermal therapy temperature can be controlled within a mild range of 40-45℃, acting only on the infected lesion area without damaging the surrounding normal tissue; bromothymol blue is a pH-responsive dye with good biocompatibility, is non-cytotoxic, and can achieve non-invasive infection monitoring.

[0018] 3. Compared to traditional cast hydrogels, hydrogel fiber membranes prepared by wet spinning have significantly higher porosity, with a water vapor permeability of approximately 10.06 mg·cm⁻¹. -2 ·h -1 It is significantly superior to commonly used cotton gauze in clinical practice, providing a suitable moist microenvironment for wound healing; the prepared dressing (PSBAH) has a fracture stress of about 0.57 MPa and a swelling rate of about 680%, and has excellent mechanical properties and absorbency, good fit, and helps to absorb wound exudate in a timely manner.

[0019] 4. The wet spinning process achieves uniform dispersion and stable loading of gold nanobipyramidal particles and bromothymol blue in the fiber matrix; after loading the two functional components, the porosity of the wet-spun hydrogel is not significantly affected, maintaining the excellent hydrophilicity and breathability of the dressing while ensuring the diagnostic and therapeutic functions. Attached Figure Description

[0020] The accompanying drawings are provided to further explain the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a physical image of the therapeutic antibacterial hydrogel dressing (PSBAH) prepared in Example 1 of the present invention.

[0021] Figure 2 This is a transmission electron microscope (TEM) image of the gold nanobipyramidal particles (AuNBPs) prepared in Example 1 of the present invention.

[0022] Figure 3 This is the UV-Vis absorption spectrum of the gold nanobipyramidal particles prepared in Example 1 of the present invention.

[0023] Figure 4 The image shows the photothermal change curve of the gold nanobipyramidal particles prepared in Example 1 of this invention under 808 nm laser irradiation.

[0024] Figure 5 Photographs and UV-Vis absorption spectra of bromothymol blue (BTB) solutions after incubation with Staphylococcus aureus solutions of different concentrations.

[0025] Figure 6 The photothermal change curve of the therapeutic antibacterial hydrogel dressing (PSBAH) prepared in this invention under 808 nm laser irradiation.

[0026] Figure 7 The stress-strain curves of three wet-spun hydrogels (PSH, PSAH, PSBAH) are shown. PSH is a pure PVA / SA hydrogel fiber, PSAH is a hydrogel fiber loaded with AuNBPs, and PSBAH is a therapeutic hydrogel dressing loaded with both AuNBPs and BTB.

[0027] Figure 8 Characterization diagrams of the skin-adhesive properties of different hydrogel dressings.

[0028] Figure 9 A bar chart comparing the porosity of cast hydrogels with three wet-spun hydrogels (PSH, PSAH, PSBAH).

[0029] Figure 10 A comparison chart of the swelling rates of three types of hydrogels—castable hydrogel, PSH, and PSBAH—after full swelling.

[0030] Figure 11 This is a comparison chart of the water vapor transmission rates of cast hydrogel, PSBAH hydrogel, and cotton gauze at 37°C for 24 h, with an open-top placement as a negative control.

[0031] Figure 12 This is a comparison of Staphylococcus aureus colony counts using two gold nanomaterials, gold nanorods (Au nanorods) and gold nanobipyramidal particles (AuNBPs), under conditions of irradiation with and without 808 nm laser light.

[0032] Figure 13 This image shows the in vitro antimicrobial plate count results of the blank control dressing and therapeutic antimicrobial hydrogel dressing (PSBAH) at different bacterial concentrations.

[0033] Figure 14Visual images of wounds with different hydrogel dressings at different stages of infection in vivo, showing the dynamic color changes of PSBAH dressings as the degree of infection changes.

[0034] Figure 15 Photographs showing the wound healing process in the blank control group and the PSBAH laser / non-laser treatment group in a mouse dorsal skin infection model.

[0035] Figure 16 The figure shows the results of the gold nanobipyramidal particles prepared under different sodium borohydride dosages (250 μL, 260 μL, 270 μL) in Example 5.

[0036] Figure 17 The figure shows the results of the gold nanobipyramidal particles prepared under different seed solution volumes (80 μL, 100 μL, 120 μL) in Example 6. Detailed Implementation

[0037] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art, and the materials and reagents used can be obtained commercially.

[0038] The naming rules for the four hydrogel samples described in this invention are as follows: PSH is a blank hydrogel fiber dressing prepared by wet spinning of polyvinyl alcohol (PVA) and sodium alginate (SA); PSAH is a hydrogel fiber dressing loaded with gold nanoparticles (AuNBPs) on the basis of PSH; PSBAH is a therapeutic antibacterial hydrogel dressing further loaded with bromothymol blue (BTB) on the basis of PSAH; PSBH is a control hydrogel fiber dressing loaded with bromothymol blue (BTB) on the basis of PSH and without gold nanoparticles (AuNBPs).

[0039] Example 1: (1) Preparation of hydrogel spinning solution: Polyvinyl alcohol 1799 (PVA 1799) was dissolved in deionized water and stirred to obtain a 10% PVA solution. Sodium alginate (SA) was dissolved in deionized water and stirred to obtain a 1% SA solution. The PVA solution and SA solution were mixed at a volume ratio of 4:1 to obtain the spinning solution; (2) Preparation of gold nanoparticles: AuNBPs were prepared by seed growth method. 0.16 g of hexadecyltrimethylammonium chloride and 0.012 g of citric acid monohydrate were dissolved in 10 mL of tetrachloroauric acid solution. Then, 0.25 mL of sodium borohydride solution was added to the above reaction solution, and the mixture was slowly stirred in a water bath at 80 °C for 90 min to obtain a seed solution. 0.364 g of hexadecyltrimethylammonium bromide was dissolved in 10 mL of deionized water, and 0.5 mL of 10 mM tetrachloroauric acid solution was added. After stirring and mixing, 0.1 mL of 10 mM silver nitrate solution, 0.2 mL of 1 M hydrochloric acid solution, 80 μL of 100 mM ascorbic acid solution were added in sequence, with a two-minute interval between each solution. Finally, 60 μL of seed solution was added, and the mixture was allowed to stand at 30 °C for 2 h to obtain gold nanoparticles. (3) Preparation of hydrogel containing antibacterial agent: Gold nanobipyramidal particles were added to the spinning solution at a volume ratio of 0.5:10, stirred and mixed, and ultrasonically defoamed for half an hour. A coagulation bath (containing 50 g / L calcium chloride and 20 g / L boric acid) was prepared. The spinning solution was injected into the coagulation bath at a uniform speed of 5 mm / min through a syringe with an 18 G needle. After soaking for a period of time, hydrogel fibers were obtained. After weaving into a dressing, the fibers were thoroughly washed with deionized water and freeze-dried to obtain a hydrogel dressing containing antibacterial agent. (4) Preparation of bromothymol blue indicator: Prepare a 5 wt% PEG 2000 solution with a pH 8 buffer solution, and then dissolve bromothymol blue in a solution containing a solubilizer to obtain a 5% bromothymol blue solution.

[0040] (5) Preparation of the integrated antibacterial hydrogel dressing for diagnosis and treatment: The freeze-dried hydrogel dressing containing antibacterial agent was swollen and moistened with a pH 8 buffer solution, then immersed in bromothymol blue solution, and placed in a vacuum drying oven for a period of time to fully adsorb the indicator to obtain the integrated antibacterial hydrogel dressing for diagnosis and treatment.

[0041] Figure 1 This is a sample image of the therapeutic antibacterial hydrogel dressing prepared in Example 1 of the present invention.

[0042] Example 2: To improve the mechanical properties of hydrogel fibers, the sodium alginate content in the hydrogel was investigated using a single variable method. The difference from Example 1 was that only the mass fraction of the sodium alginate solution was changed, with mass fractions of 1%, 2%, 3%, 4%, and 5%. The results are shown in Table 1. A 2% sodium alginate solution was selected as the raw material for subsequent reactions.

[0043] Table 1. Investigation of sodium alginate content in hydrogel precursor solution Example 3: To improve the mechanical properties of hydrogel fibers, the polyvinyl alcohol content in the hydrogel was investigated as a single variable. The difference from Example 1 was that only the mass fraction of the polyvinyl alcohol solution was changed, with mass fractions of 10%, 15%, and 20%. The results are shown in Table 2. A 10% polyvinyl alcohol solution was selected as the raw material for subsequent reactions.

[0044] Table 2. Investigation of polyvinyl alcohol content in hydrogel precursor solution Example 4: To improve the mechanical properties of hydrogel fibers, a univariate study was conducted on the ratio of polyvinyl alcohol (PVA) to sodium alginate in the hydrogel. The difference from Example 1 was that only the volume ratio of the PVA solution to the sodium alginate solution was changed, with volume ratios of 2:1, 4:1, 6:1, and 8:1. The results are shown in Table 3. A volume ratio of 4:1 was selected for subsequent wet spinning.

[0045] Table 3. Investigation of the ratio of polyvinyl alcohol to sodium alginate in the hydrogel precursor solution. Example 5: To prepare gold nanoparticles with a unique bipyramidal needle-like structure and excellent photothermal properties, the volume of sodium borohydride in the seed solution during the preparation process was investigated. The difference from Example 1 was that only the volume of sodium borohydride in the gold nanoparticle seed preparation process was changed to 250 μL, 260 μL, and 270 μL, respectively. The results are as follows: Figure 16 As shown, an excellent seed solution was prepared using a volume of 270 μL of sodium borohydride.

[0046] Example 6: To prepare gold nanoparticles with a unique bipyramidal needle-like structure and excellent photothermal properties, the volume of the seed solution added to the growth solution during the preparation process was investigated. The difference from Example 1 was that only the volume of seeds added to the growth solution was changed to 80 μL, 100 μL, and 120 μL. The results are shown in the figure. Choosing a seed volume of 80 μL resulted in gold nanoparticles with excellent photothermal properties.

[0047] Example 7: To obtain an antibacterial hydrogel dressing with mild photothermal properties, the volume ratio of gold nanoparticles to the hydrogel precursor solution was investigated. The difference from Example 1 was that only the volume ratio of the gold nanoparticles to the spinning solution was changed to 0.5:10, 1:10, 1.5:10, and 2:10. The results are shown in Table 4. Adding the gold nanoparticles to the spinning solution at a volume ratio of 0.5:10 resulted in a dressing with mild photothermal properties.

[0048] Table 4. Effect of different volume ratios of gold nanobipyramidal nanoparticles and hydrogel precursor solutions on the photothermal properties of the hydrogel. Example 8: The effect of needle aperture size on the mechanical properties of hydrogel fibers during wet spinning was investigated using a single variable method. The difference from Example 1 was that only the needle aperture size during wet spinning was changed to 18 G, 20 G, 22 G, and 24 G. The results are shown in Table 5. Selecting 20 G for wet spinning yielded fibers with good mechanical properties.

[0049] Table 5. Effect of needle aperture size on the mechanical properties of fiber in wet spinning. Example 9: The effect of spinning speed on the mechanical properties of hydrogel fibers during wet spinning was investigated using a single variable method. The difference from Example 1 was that only the spinning speed during wet spinning was changed to 5 mm / min, 10 mm / min, 15 mm / min, and 20 mm / min. The results are shown in Table 6. A spinning speed of 5 mm / min was selected for wet spinning, resulting in fibers with good mechanical properties.

[0050] Table 6. Effect of spinning speed on the mechanical properties of fiber in wet spinning Example 10: To obtain a suitable concentration of bromothymol blue solution for rapid pH detection, different solubilizers were selected to increase the solubility of bromothymol blue. The difference from Example 1 is that only the solubilizer used in the dissolution process of the bromothymol blue solution was changed. Selectable solubilizers included PEG 2000, PEG 4000, PVP 10000, PVP 24000, and PVP K30. The results are shown in Table 7. PEG 2000 was selected as the solubilizer for the dissolution process of the bromothymol blue solution.

[0051] Table 7. Effect of different solubilizers on the solubility of bromothymol blue Example 11: Based on Example 10, a suitable solubilizer was selected, and bromothymol blue solutions with different mass fractions were prepared. The colorimetric properties of these solutions loaded onto hydrogels were investigated. The difference from Example 1 was that only the concentration of bromothymol blue in the solutions was changed, to 0.3 mg / mL, 0.4 mg / mL, and 0.5 mg / mL. The results are shown in Table 8. Selecting bromothymol blue solutions with concentrations of 0.4 mg / mL to 0.5 mg / mL resulted in excellent colorimetric properties for the therapeutic antibacterial hydrogel dressing.

[0052] Table 8 Effect of bromothymol blue solution concentration on the colorimetric properties of hydrogels Comparative Example 1: Preparation of cast-type hydrogel dressing.

[0053] Prepare a PVA / SA spinning solution with the same composition according to step (1) of Example 1, add AuNBPs with the same volume ratio to it, stir and mix well, pour directly into a mold for casting, cure at room temperature, immerse in the same coagulation bath (containing 50 g / L calcium chloride and 20 g / L boric acid) for crosslinking for 30 min, take it out and wash with deionized water, freeze dry, and then load BTB according to steps (4) to (5) of Example 1 to obtain a cast-type comparative dressing.

[0054] The only difference between this comparative example and Example 1 is the molding process: Example 1 uses wet spinning, while this comparative example uses casting molding, and the raw material composition is exactly the same.

[0055] Comparative Example 2: Preparation of dressings using gold nanorods instead of gold nanobipyramidal particles.

[0056] Gold nanorods were prepared using conventional methods and added to the spinning solution obtained in step (1) of Example 1 at the same volume ratio (0.5:10) as the spinning solution. Subsequent steps were exactly the same as in Example 1 to obtain a comparative dressing containing gold nanorods.

[0057] The only difference between this comparative example and Example 1 is the type of antibacterial agent: Example 1 used gold nanobipyramidal nanoparticles, while this comparative example uses gold nanorods. The rest of the composition and preparation process are the same.

[0058] Comparative Example 3: BTB-free hydrogel dressing (PSAH).

[0059] Prepare hydrogel fiber dressing (PSAH) containing AuNBPs according to steps (1) to (3) of Example 1, omitting the BTB loading step in steps (4) to (5), and directly using the freeze-dried PSAH as the control dressing.

[0060] The only difference between this comparative example and Example 1 is that it does not contain BTB indicator; the rest of the composition and process are the same.

[0061] Comparative Example 4: Hydrogel dressing without AuNBPs (PSBH).

[0062] After preparing the spinning solution according to step (1) of Example 1, without adding AuNBPs, wet spinning was carried out directly. The subsequent freeze drying and BTB loading steps were the same as in Example 1, and a blank hydrogel fiber dressing (PSBH) containing only BTB was obtained.

[0063] Experimental Example 1: Morphology and Spectroscopic Characterization of Gold Nanoparticles: The gold nanoparticles obtained in Example 1 were observed using a transmission electron microscope (TEM), and the results are as follows: Figure 2 As shown, the prepared particles exhibit a distinct bipyramidal needle-like structure, regular morphology, good dispersibility, and a particle size of approximately 140–170 nm.

[0064] The gold nanoparticles obtained in Example 1 were subjected to ultraviolet-visible absorption spectroscopy (UV-Vis) testing, and the results are as follows: Figure 3 As shown, AuNBPs have a characteristic absorption peak in the near-infrared region (about 808 nm), which matches the 808 nm laser wavelength, providing a spectral basis for their photothermal antibacterial properties.

[0065] Experimental Example 2: Photothermal Performance Test of Gold Nanoparticles (Bipyramidal Particles): The AuNBPs solution obtained in Example 1 was placed under an 808 nm laser (power density 1 W / cm²). 2 The solution was continuously irradiated, and the temperature changes of the solution were recorded in real time with an infrared thermal imager. Multiple cyclic switching tests were conducted.

[0066] like Figure 4 As shown, the temperature of the AuNBPs solution rises rapidly under laser irradiation, and the photothermal conversion efficiency remains stable after multiple cycles, proving that it has excellent and stable photothermal performance.

[0067] Experimental Example 3: In vitro colorimetric performance test of BTB solution: A certain amount of BTB solution was added to Staphylococcus aureus bacterial suspensions of different concentrations (original bacterial suspension concentration was 10). 9 CFU / mL, diluted to 0, 10, 50, 100, 200 and 500 times respectively, and incubated in a shaker at 37°C. The color changes were observed and the results were characterized by UV-Vis spectroscopy.

[0068] Figure 5 As shown, with increasing bacterial concentration, more acidic substances are produced by bacterial metabolism, and the pH gradually decreases. The color of the BTB solution gradually changes from blue to yellow, and the peak position of the ultraviolet-visible absorption spectrum shifts regularly with pH changes, proving that BTB can sensitively respond to pH changes caused by bacterial infection and achieve visual detection.

[0069] Experimental Example 4: Photothermal Performance Test of Therapeutic Antibacterial Hydrogel Dressing: The PSBAH dressing obtained in Example 1 was irradiated with an 808 nm laser (power density 1 W / cm²), and the surface temperature change of the dressing was monitored with an infrared thermal imager.

[0070] Test results: such as Figure 6As shown, the PSBAH dressing can reach a temperature of 60°C under irradiation with an 808 nm laser, which is a mild photothermal range. This effectively kills bacteria in the lesion area without damaging the surrounding normal tissue, proving that the dressing has mild and controllable photothermal antibacterial properties.

[0071] Experimental Example 5: Mechanical Property Testing of Hydrogel Dressings: Stress-strain tests were conducted on three types of hydrogels (PSH, PSAH, and PSBAH) using a universal testing machine. Hydrogel samples were prepared as strips with dimensions of 40 × 20 × 2 mm (length × width × thickness). Tests were performed at room temperature (25°C) with a clamping distance of 30 mm and a tensile speed of 50 mm / min. Each sample was tested at least three times, and the average value was taken.

[0072] like Figure 7 As shown, PSH fractured at approximately 1.1% strain with a fracture stress of approximately 0.12 MPa; PSAH fractured at approximately 1.6% strain with a fracture stress of approximately 0.20 MPa; and PSBAH fractured at approximately 2.0% strain with a fracture stress of approximately 0.57 MPa. The results indicate that loading AuNBPs and BTB significantly improved the strength and ductility of the hydrogel dressings, with PSBAH exhibiting the best overall mechanical properties.

[0073] Experimental Example 6: Adhesion Performance Test of Hydrogel Dressings: The PSBAH and PSH dressings obtained in Example 1 were applied to human skin and curved areas such as joints, respectively. Adhesion effect photographs were taken, and the results are as follows: Figure 8 As shown, wet-spun hydrogel fiber dressings have good flexibility and can adhere closely to the skin surface, making them suitable for wound coverage in different anatomical locations.

[0074] Experimental Example 7: Porosity Test of Hydrogel Dressings: After drying each group of hydrogels, square samples were prepared, and the dry weight (M1) was measured. The length, width, and height of the samples were accurately measured using vernier calipers, and the volume V (cm³) was calculated. 3 Immerse the sample in anhydrous ethanol until the pores are fully filled, then remove the sample, wipe off excess ethanol with filter paper, and weigh the wet weight (M2). The porosity calculation formula is as follows: ; In the formula, ρ is the density of anhydrous ethanol (g / cm³). 3 ).

[0075] like Figure 9As shown, the porosity of the cast hydrogel is significantly lower than that of the wet-spun hydrogels (PSH, PSAH, PSBAH), indicating that the wet spinning process imparts a large-pore structure to the hydrogel, which facilitates the rapid diffusion of water molecules, ions, and nutrients, thereby improving the dressing's water absorption capacity. The porosity differences among the three wet-spun hydrogels are not significant, indicating that loading AuNBPs and BTB does not affect the pore structure of the hydrogel, and the dressing still possesses excellent hydrophilicity.

[0076] Experiment 8: Swelling Performance Test of Hydrogel Dressings: Each group of hydrogels was dried to constant weight, and the dry weight (W1) was measured. The samples were placed in a container filled with deionized water and immersed until fully swollen. After immersion, the samples were removed, excess surface moisture was wiped dry with clean filter paper, and the wet weight (W2) was measured. The swelling rate was calculated using the following formula: .

[0077] like Figure 10 As shown, the swelling rate of the cast hydrogel after full swelling is approximately 437%; the swelling rate of PSH is approximately 523%; and the swelling rate of PSBAH is approximately 680%, which is significantly higher than that of the cast hydrogel. This indicates that the wet-spun hydrogel has excellent water absorption driving force, which can absorb wound exudate in a timely manner and provide a suitable moist environment for wound healing.

[0078] Experimental Example 9: Water Vapor Transmission Rate Test of Hydrogel Dressings: Deionized water was added to a glass bottle, ensuring a gap of 5 (±1) mm between the liquid level and the bottle opening. Each group of hydrogel samples was prepared into thin sheets of the same size and thickness, and the glass bottle openings were sealed. The initial mass (W) was then measured. i After sealing the glass bottle, place it in a 37°C incubator for 24 hours, then remove it and weigh the final mass (W). t (The sample was placed in an open container as a negative control.) The formula for calculating water vapor transmission rate is as follows: ; In the formula, A represents the area of ​​the bottle opening (cm²). 2 ); t represents the interval time (h).

[0079] like Figure 11 As shown, the water vapor transmission rate of the cast hydrogel is approximately 4.28 mg·cm⁻¹. -2 ·h -1 The water vapor transmission rate is lower than that of commonly used clinical cotton gauze; the water vapor transmission rate of PSBAH wet-spun hydrogel is approximately 10.06 mg·cm⁻¹. -2 ·h -1 The results showed that the wet-spun dressing was significantly better than cotton gauze and cast hydrogel, indicating that the dressing has excellent breathability, can provide a good moist microenvironment for wound healing, and at the same time avoid fluid accumulation.

[0080] Example 10: Comparison of In Vitro Antibacterial Properties of Gold Nanomaterials: The in vitro antibacterial properties of gold nanorods and gold nanobipyramidal materials were compared using the plate coating method. A blank control group, a gold nanorod group, and a gold nanobipyramidal group were set up, with laser irradiation and non-laser irradiation groups within each group. A concentration of 1.0 × 10⁻⁶ was added to both the gold nanorod group and the gold nanobipyramidal group at the same ratio. 5 CFU / mL Staphylococcus aureus solution, laser irradiation group using 808 nm, 1 W / cm 2 The group was irradiated with laser for 5 minutes, and the non-laser irradiated group was not treated. After incubation at 37°C for 2 hours, 50 μL of bacterial solution was spread on LB agar plates and incubated at 37°C overnight. The colonies were counted, and 3 replicates were set up for each group.

[0081] like Figure 12 As shown, the bacterial colony growth of three treatment groups—blank control, gold rod, and gold nanoparticle bipyramidal group—under conditions with and without laser irradiation is illustrated. Without laser irradiation, the number of colonies in the gold rod group was slightly lower than that in the blank control group, but still densely packed; the number of colonies in the gold nanoparticle bipyramidal group was significantly lower. After laser irradiation, there was no significant change in the number of colonies in the blank control group and the gold rod group, while the colonies in the gold nanoparticle bipyramidal group almost completely disappeared. These phenomena indicate that the unique bipyramidal needle-like structure of gold nanoparticles exhibits excellent antibacterial effects under both laser irradiation and non-laser irradiation conditions. At the same concentration, the photothermal properties of gold nanoparticle bipyramidal groups are superior to those of gold rods, resulting in a more outstanding antibacterial effect.

[0082] Experimental Example 11: In vitro antibacterial performance test of therapeutic antibacterial hydrogel dressing: Gram-positive Staphylococcus aureus was used as the model bacteria, and bacterial suspensions of different concentrations (10... 4 ~10 8 The CFU / mL serially diluted solution was mixed with fixed amounts of blank dressing and PSBAH dressing, and incubated at 37°C for 2 h in a shaker at 150 rpm. 50 μL of the bacterial solution was then spread onto a plate and incubated at 37°C for 24 h before counting the colonies.

[0083] like Figure 13 As shown, a large number of colonies grew in the blank dressing group at all concentrations; PSBAH dressing showed significant antibacterial effects at all test bacterial concentrations under laser irradiation, with almost no colony growth in the plates, proving that PSBAH has excellent in vitro antibacterial properties.

[0084] Experiment 12: Visualization of in vivo infection detection of therapeutic antibacterial hydrogel dressing: A mouse dorsal skin infection model was established (see Experiment 13 for details). PSBAH dressing was applied to the wound, and the color change of the dressing was observed and photographed within 30 minutes. The color development of the dressing under different degrees of infection was recorded.

[0085] like Figure 14As shown, the color of the PSBAH dressing changes significantly depending on the degree of wound infection after application. When the infection is more severe, the color shifts towards yellow, while when the infection is mild, it remains blue-green. This demonstrates that PSBAH can achieve real-time naked-eye visualization diagnosis of bacterial infection in wounds and sensitively reflect the dynamic process of infection.

[0086] Experiment 13: Evaluation of antibacterial and healing-promoting effects in a mouse skin infection model: Animal model establishment: Four-week-old female mice of the same age were selected. Before modeling, the hair on their backs was removed and treated with depilatory cream. Before surgery, the mice were anesthetized by intraperitoneal injection of 1.25% tribromoethanol (0.2 mL / 10 g). A circular incision with a diameter of about 1 cm was made on the back using sterile surgical instruments. Staphylococcus aureus was applied to the wound. The infection model was considered to be successfully established when obvious redness, swelling and exudate appeared.

[0087] Grouping and Treatment: Mice were randomly divided into a blank control group and a PSBAH group, with 3 mice in each group. Each group was further divided into laser irradiation and non-laser irradiation subgroups. Medications were administered according to the groups. The laser irradiation group was irradiated with an 808 nm laser for 5 minutes after administration, while the temperature of the irradiated area was monitored using an infrared thermal imager to maintain it at 40–45°C. Administered medication twice daily, morning and evening, and wound healing was continuously observed and recorded.

[0088] like Figure 15 As shown, the blank control group had slow wound healing and persistent infection; the PSBAH laser irradiation group had efficient removal of bacteria, significantly reduced inflammation, and significantly accelerated wound healing, demonstrating that PSBAH dressing can effectively kill bacteria, control infection, and synergistically promote wound healing through gentle photothermal therapy.

[0089] Finally, it should be noted that the above embodiments are merely illustrative of several implementations of the present invention and are not intended to limit the scope of the invention. For those skilled in the art, any modifications, equivalent substitutions, or improvements made without departing from the concept of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a therapeutic antibacterial hydrogel dressing, characterized in that, Includes the following steps: (1) Mix polyvinyl alcohol solution with sodium alginate solution to obtain spinning solution; (2) Add gold nanobipyramidal particles to the spinning solution, stir and mix well to obtain a mixed solution; (3) The mixed solution is extruded into a coagulation bath containing calcium chloride and boric acid by wet spinning, and after cross-linking and solidification, hydrogel fiber filaments are obtained, which are then woven into dressings and freeze-dried. (4) After the freeze-dried dressing is swollen and moistened with a buffer solution, it is soaked in bromothymol blue solution and vacuum dried to obtain the integrated antibacterial hydrogel dressing.

2. The preparation method according to claim 1, characterized in that, The polyvinyl alcohol solution contains 10% to 20% polyvinyl alcohol by mass; the sodium alginate solution contains 1% to 5% sodium alginate by mass; and the volume ratio of the polyvinyl alcohol solution to the sodium alginate solution is 2:1 to 8:

1.

3. The preparation method according to claim 1, characterized in that, The volume ratio of the gold nanobipyramidal particles to the spinning solution is 0.5:10 to 2:10; the concentration of bromothymol blue in the bromothymol blue solution is 0.3 to 0.5 mg / mL.

4. The preparation method according to claim 1, characterized in that, A solubilizer is used during the dissolution of the bromothymol blue solution. The solubilizer is selected from one or more of PEG 2000, PEG 4000, PVP 10000, PVP 24000, and PVP K30. The pH of the buffer solution in step (4) is 7 to 9.

5. The preparation method according to claim 1, characterized in that, In step (3), the needle aperture of wet spinning is 18~24G, and the spinning speed is 5~20mm / min.

6. The preparation method according to claim 1, characterized in that, The vacuum drying temperature in step (4) is 30~60℃.

7. The preparation method according to claim 1, characterized in that, The gold nanoparticles are prepared by a seed growth method, comprising: dissolving hexadecyltrimethylammonium chloride and citric acid monohydrate in tetrachloroauric acid solution, adding sodium borohydride solution, heating and stirring to obtain a seed solution; dissolving hexadecyltrimethylammonium bromide in deionized water by heating, and sequentially adding tetrachloroauric acid solution, silver nitrate solution, hydrochloric acid solution and ascorbic acid solution, mixing evenly to obtain a growth solution; adding the seed solution to the growth solution, stirring and mixing evenly, and allowing to stand to obtain the gold nanoparticles.

8. The preparation method according to claim 7, characterized in that, In the preparation of the seed solution, the concentration of hexadecyltrimethylammonium chloride was 0.016 g / mL, the concentration of citric acid monohydrate was 0.0012 g / mL, the amount of sodium borohydride solution added per 10 mL tetrachloroauric acid solution was 250~280 μL, the heating temperature was 80~95℃, and the stirring time was 60~90 min. In the preparation of the growth solution, the concentration of hexadecyltrimethylammonium bromide was 0.0364 g / mL, the dissolution temperature was 30~60℃, and 0.5 mL of 10 mM tetrachloroauric acid solution, 0.1 mL of 10 mM silver nitrate solution, 0.2 mL of 1 M hydrochloric acid solution, and 80 μL of 100 mM ascorbic acid solution were added sequentially to every 10 mL of deionized water. The amount of seed solution added to every 10 mL of growth medium is 60~120 μL, and the standing time is 2~12 h; The obtained gold nanobipyramidal particles have a particle size of 140~170nm and can be stored at 4℃ for 1~14 days.

9. Therapeutic antibacterial hydrogel dressing prepared by the preparation method according to any one of claims 1-8.

10. The application of the therapeutic antibacterial hydrogel dressing as described in claim 9 in the preparation of wound dressings.

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