A hydrogel dressing and a method of making the same

Abstract

The present application relates to the technical field of medical dressings, and particularly relates to a hydrogel dressing and a preparation method thereof, and the weight ratio of the hydrogel dressing comprises: bacterial cellulose: 1-20 parts; toluene isocyanate: 1-10 parts; modified folic acid: 0.5-5 parts; metal organic framework nanoparticles: 1-10 parts; solvent: 50-200 parts. The present application precisely modifies the outer surface of copper-based MOFs by using folic acid-polyethylene glycol conjugates, which not only solves the problem of copper ion burst release, but also retains the integrity of the pore channel to ensure the long-term controllable release of copper ions; toluene isocyanate is used to construct a three-dimensional covalent cross-linking network, which improves the mechanical properties of the hydrogel and the fixation of MOFs, and further combines the advantages of the biomimetic scaffold, wetting and moisturizing, double antibacterial and biocompatibility of bacterial cellulose, thereby solving the core problems of the poor stability of the existing copper-based MOFs, the easy plugging of the folic acid modification, the poor copper ion release control and the primary dosage form of the related wound products.

Description

Technical Field

[0001] This invention relates to the field of medical dressing technology, specifically to a hydrogel dressing and its preparation method. Background Technology

[0002] Chronic, non-healing wounds are one of the most serious complications of diabetes, with diabetic foot ulcers being particularly typical. Their core pathological features include persistent local inflammation, impaired angiogenesis, insufficient collagen deposition, and recurrent infections. This not only severely reduces patients' quality of life but also leads to extremely high disability rates and imposes a heavy social and medical burden.

[0003] Currently, the wound dressings routinely used in clinical practice are mainly traditional gauze, hydrocolloid dressings, and foam dressings. Their core functions are concentrated on physically isolating the wound, absorbing exudate, and maintaining a moist wound microenvironment. They generally lack the ability to actively regulate the wound microenvironment, cannot effectively promote the proliferation and migration of key cells related to wound repair, and are difficult to accelerate the regeneration process of damaged tissues. They lack biological activity and have a very limited effect on promoting the healing of chronic and refractory wounds.

[0004] To endow wound dressings with the biological function of actively promoting healing, researchers have focused their research on active ions with clear biological regulatory effects. Among them, copper ions have been extensively studied and confirmed to be a key regulator in the wound healing process. Copper ions can effectively promote local angiogenesis, collagen synthesis, epithelialization, and tissue matrix remodeling at the wound site by upregulating the expression of various core growth factors such as vascular endothelial growth factor and fibroblast growth factor, thereby significantly accelerating wound healing. However, the direct application of copper ions to wound treatment still faces several fundamental technical challenges: First, the release process is uncontrollable; copper ions are easily and rapidly released in wound exudate, leading to a sudden increase in local concentration and even causing cytotoxicity and oxidative stress damage. Second, the effect is short-lived; to maintain an effective therapeutic concentration at the wound site, frequent dressing changes are required, which not only increases treatment costs but also aggravates patient suffering. Third, there is a lack of targeting; copper ions are difficult to effectively accumulate at the wound site, resulting in low bioavailability.

[0005] To address the challenge of controlled release of copper ions, MOFs (Metal-Organic Frameworks) have emerged as a novel biomaterial carrier. MOFs are porous crystalline materials formed by the self-assembly of metal ions / clusters and organic ligands through coordination bonds. They possess ultra-high specific surface area, precisely controllable pore size, and chemical composition, making them ideal for loading and controlling the release of active ingredients. Among these, copper-based MOFs, capable of both holding copper ions and releasing them slowly as needed, are the preferred choice. However, copper-based MOFs suffer from a fatal flaw in practical wound treatment: extremely poor stability in protein-containing physiological environments. Protein molecules in wound exudate easily trigger rapid collapse of the MOF structure, leading to the rapid release of the loaded copper ions. This not only replicates the toxicity problems of directly using copper salts but also prevents the MOFs from realizing their sustained-release potential.

[0006] To address the stability bottleneck of copper-based MOFs, existing research has explored related technologies. One approach involves introducing small-molecule folic acid as a modifier during the synthesis of copper-based MOFs. Folic acid incorporation enhances the hydrophobicity of MOFs, slowing their degradation rate in serum-containing culture media, resulting in a slower release of copper ions compared to unmodified MOFs. This has also demonstrated superior healing effects in a diabetic mouse wound model. However, this approach suffers from a significant and unresolved core contradiction: while folic acid improves MOF stability, it also enters and occupies the pore space, causing severe pore blockage and a sharp decrease in the material's specific surface area. This significantly limits the loading capacity of MOFs as carriers, making it difficult to simultaneously load other therapeutic agents such as antibiotics and growth factors, thus hindering multi-effect synergistic therapy. Furthermore, it alters the ion / molecule diffusion pathway, making precise control of release kinetics difficult.

[0007] Furthermore, the dosage forms of existing MOF-based wound treatment products are still relatively rudimentary, mainly consisting of MOF nanoparticle suspensions or simply MOFs loaded onto traditional substrates such as nonwoven fabrics. These forms have significant application drawbacks: First, poor wound retention, as MOFs are easily washed away by wound exudate, failing to form a sustained and effective therapeutic concentration at the wound site; second, weak biomimetic adaptability, lacking a biomimetic three-dimensional structure similar to the extracellular matrix, which is not conducive to the adhesion, migration, and tissue ingrowth of wound-related cells; third, poor mechanical adaptability, making it difficult to closely adhere to irregular wounds in various parts of the body, especially at joints, resulting in insufficient physical protection of the wound; fourth, low functional integration, typically only achieving the single healing-promoting function of copper ions, failing to meet the multiple needs of chronic, refractory wound healing, such as antibacterial, moisturizing, and inflammatory regulation.

[0008] In summary, designing a surface modification strategy that can effectively protect the structural stability of copper-based MOFs without sacrificing their pore integrity, and applying the modified copper-based MOFs to dressings for chronic, non-healing wounds, has become a core technical challenge that urgently needs to be addressed in this field. Summary of the Invention

[0009] This application provides a hydrogel dressing and its preparation method to solve the problems of poor stability of copper-based MOFs, easy pore blockage due to folic acid modification, poor controllability of copper ion release, and rudimentary dosage forms of related wound products in the prior art.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a hydrogel dressing, wherein the weight proportions of the hydrogel dressing include: Bacterial cellulose: 1-20 parts; Toluene isocyanate: 1-10 parts; Modified folic acid: 0.5-5 parts; Metal-organic framework nanoparticles: 1-10 parts; Solvent: 50-200 parts.

[0011] Furthermore, the weight proportions of the hydrogel dressing include: Bacterial cellulose: 5-10 parts; Toluene isocyanate: 2-8 parts; Modified folic acid: 1-4 parts; Metal-organic framework nanoparticles: 2-8 parts; Solvent: 80-120 parts.

[0012] Furthermore, the modified folic acid comprises the following weight proportions: Folic acid: 0.5-1.5 parts; Polyethylene glycol: 2-10 parts; Coupling agent: 0.1-1 part; Catalyst: 0.01-0.1 parts; Reaction solvent: 10-50 parts.

[0013] Further, the polyethylene glycol has a molecular weight of 2000-5000 Da; the coupling agent is selected from at least one of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, dicyclohexylcarbodiimide, and N-hydroxysuccinimide; the catalyst is selected from at least one of 4-dimethylaminopyridine and triethylamine; and the reaction solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, and phosphate buffer.

[0014] Furthermore, the metal-organic framework nanoparticles are copper-based metal-organic frameworks selected from at least one of HKUST-1, NOTT-100, and Cu-MOF-74, and the particle size of the metal-organic framework nanoparticles is 100-200 nm.

[0015] Furthermore, the bacterial cellulose is nano-bacterial cellulose, with a fiber diameter of 20-100 nm and a length of 1-10 μm.

[0016] Furthermore, the solvent is selected from water, phosphate buffer, physiological saline, ethanol, or dimethyl sulfoxide.

[0017] Furthermore, the modified folic acid is applied to the outer surface of the metal-organic framework nanoparticles to form modified folic acid-modified metal-organic framework nanoparticles; wherein the molecular size of the modified folic acid is larger than the pore size of the metal-organic framework nanoparticles.

[0018] It should be noted that the modified folic acid in this embodiment is a folic acid-polyethylene glycol (PEG) conjugate, whose molecular size is significantly larger than the pore size of copper-based MOFs. When the PEG conjugate reacts with MOF nanoparticles, the large PEG conjugate is physically blocked from entering the pores, and can only selectively modify the outer surface of MOFs, unable to enter their internal pores. The PEG conjugate modified on the outer surface effectively blocks the attack of protein molecules in wound exudate on the MOF structure through steric hindrance and hydration layer effects, significantly improving the stability of copper-based MOFs in the physiological environment. Since the PEG conjugate is only modified on the outer surface, the internal pores of MOFs are completely preserved, and the decrease in specific surface area is reduced. Furthermore, the PEG segments in the folic acid-polyethylene glycol conjugate not only provide protection but also act as a bridge, presenting folic acid targeting ligands at an appropriate distance on the MOF surface. This allows folic acid to more effectively recognize and bind to overexpressed folic acid receptors in wound tissue, achieving active targeted enrichment of the active ingredient. Simultaneously, the polyethylene glycol segments also provide reaction sites for subsequent chemical cross-linking with the bacterial cellulose backbone, ensuring that the MOFs are firmly fixed within the hydrogel network and prevented from being washed away by wound exudate.

[0019] The present invention also provides a method for preparing a hydrogel dressing, the method comprising the following steps: S1. Preparation of modified folic acid: Folic acid, polyethylene glycol, coupling agent and catalyst are dissolved in a reaction solvent and reacted at 20-40℃ for 12-48 hours. After purification, folic acid-polyethylene glycol coupling product is obtained. S2. Preparation of folic acid-modified metal-organic framework nanoparticles: Disperse metal-organic framework nanoparticles in a solvent, add the modified folic acid obtained in step S1, react at 25-60℃ for 2-24 hours, centrifuge and wash to obtain folic acid-modified metal-organic framework nanoparticles. S3. Preparation of bacterial cellulose dispersion: Disperse bacterial cellulose in a solvent and homogenize at 5000-20000 rpm for 5-30 minutes to obtain a uniform bacterial cellulose dispersion with a mass percentage concentration of 3-8%. S4. Preparation of isocyanate-terminated polyethylene glycol: Toluene isocyanate and polyethylene glycol are mixed in a molar ratio of (2-10):1 and reacted in an anhydrous solvent at 40-80°C under nitrogen protection for 4-24 hours to obtain isocyanate-terminated polyethylene glycol. S5. Crosslinking reaction: The isocyanate-terminated polyethylene glycol obtained in step S4 is added to the bacterial cellulose dispersion obtained in step S3, and the reaction is carried out at 25-60℃ for 2-24 hours to form a crosslinked network; S6. Composite and molding: The modified folic acid-modified metal-organic framework nanoparticles obtained in step S2 are added to the crosslinking system obtained in step S5, mixed evenly, ultrasonically degassed, and then cast into a mold. The mixture is allowed to stand at 25-37℃ for 6-24 hours to obtain the hydrogel dressing.

[0020] Furthermore, in step S4, the anhydrous solvent is selected from dimethyl sulfoxide, N,N-dimethylformamide, or toluene.

[0021] The present invention also provides the use of a hydrogel dressing in the preparation of a medicament for treating chronic, difficult-to-heal wounds, wherein the chronic, difficult-to-heal wounds are diabetic foot ulcers, pressure ulcers, or venous ulcers.

[0022] The beneficial effects achieved by using the present invention described above are as follows: 1. This invention prepares a hydrogel dressing, which uses folic acid-polyethylene glycol coupling to modify the surface of copper-based MOFs. Taking advantage of the fact that the molecular size of folic acid-polyethylene glycol coupling is significantly larger than the pore size of MOFs, the selective modification of folic acid-polyethylene glycol coupling on the outer surface of MOFs without entering the internal pores is precisely controlled. The pore diameter of copper-based MOFs is approximately 0.9-1.2 nm, while the folic acid-polyethylene glycol (PEG) coupling compound exhibits a random coil conformation in solution, with a hydrodynamic radius reaching 5-10 nm, far exceeding the pore size of MOFs. When the PEG coupling compound is blended with MOF nanoparticles, the large PEG molecules are physically blocked outside the pore inlets, and can only bond with unsaturated coordination sites or defect sites on the outer surface of MOFs to form a protective layer, thus preventing it from entering and blocking the internal pores. The polyethylene glycol segments modified on the outer surface physically block protein molecules in wound exudate from approaching the MOF surface through steric hindrance, preventing protein adsorption and the resulting breakage of coordination bonds. Through the hydration layer effect, a stable hydration layer is formed on the MOF surface, effectively isolating water molecules from nucleophilic attack on the copper-carboxylic acid coordination bonds, effectively solving the fatal defects of copper-based MOFs in wound applications, such as easy structural collapse and copper ion burst release. Furthermore, since the folic acid-polyethylene glycol (PEG) conjugate is only modified on the outer surface, the internal pores of MOFs are completely preserved, resulting in a smaller decrease in their BET surface area. This ensures unimpeded diffusion channels for ions / molecules, providing a structural basis for the long-term, controllable release of copper ions. Simultaneously, the PEG layer modified on the outer surface not only provides protection but also acts as a diffusion barrier to regulate the release rate of copper ions. After diffusing from the internal pores of MOFs to the outer surface, copper ions must further penetrate the PEG layer to enter the external environment, allowing for a sustained release at an appropriate rate. This covers the entire wound healing process, including the inflammatory, proliferative, and remodeling phases, thereby accelerating the overall wound healing rate and effectively avoiding cytotoxicity caused by excessively high local copper ion concentrations. 2. This application also incorporates toluene isocyanate. As a highly efficient cross-linking agent, toluene isocyanate undergoes a nucleophilic addition reaction with the terminal hydroxyl groups of polyethylene glycol (PEG) to generate stable urethane bonds, forming isocyanate-terminated PEG. This transforms the originally linear PEG molecule into a reactive bridge, enabling further reaction with the hydroxyl groups on the bacterial cellulose backbone to construct a three-dimensional covalent cross-linked network. This enhances the tensile strength of the hydrogel, endowing the dressing with excellent mechanical properties. It allows the dressing to form an independent film while also adhering closely to irregular wounds on various parts of the body, especially at joints, solving the problems of poor mechanical properties, easy breakage, and poor adhesion of traditional hydrogel dressings. Secondly, the covalent cross-linked network constructed by toluene isocyanate achieves firm fixation of MOF nanoparticles through chemical anchoring and physical entanglement, effectively preventing the loss of active ingredients by wound exudate and ensuring the sustained and stable release of copper ions at the wound site. Furthermore, the amount of toluene isocyanate can precisely control the density of the cross-linked network, thereby achieving multi-level control over the dressing degradation time and copper ion release rate. 3. Furthermore, the three-dimensional nanofiber network formed by bacterial cellulose highly mimics the collagen fiber network of the natural extracellular matrix in terms of topology, providing an ideal adhesion matrix and migration scaffold for wound repair-related cells. The bacterial cellulose nanonetwork has extremely high porosity and specific surface area, enabling it to absorb water and form and maintain a moist microenvironment at the wound site. This not only promotes cell proliferation and migration but also prevents scab formation, reduces pain, and provides ideal physiological conditions for wound healing. Simultaneously, the physical barrier effect of the nanonetwork effectively prevents bacteria from invading the wound, forming a dual antibacterial barrier with the chemical antibacterial effect of copper ions, significantly reducing the risk of infection. In addition, bacterial cellulose exhibits excellent biocompatibility and biodegradability. As a natural nanomaterial derived from microbial fermentation, bacterial cellulose does not contain impurities such as lignin and hemicellulose found in plant cellulose, is non-immunogenic, and does not cause inflammatory reactions. It can be slowly degraded by cellulase in vivo, with the degradation rate matching the rate of new tissue growth. The dressing can be gradually absorbed as the wound heals, avoiding tissue damage and patient suffering caused by secondary dressing changes. 4. This invention provides a clear preparation method with controllable step-by-step preparation parameters, ensuring the precise construction of each functional unit. Furthermore, the preparation process is green and environmentally friendly, suitable for industrial production. All steps are carried out under mild conditions, resulting in low energy consumption. The solvents are mainly environmentally friendly solvents such as water, polyethylene glycol, and ethanol; a small amount of organic solvent can be recovered and reused through vacuum distillation, meeting green chemistry requirements. The reaction process does not involve toxic or harmful substances, and waste liquid treatment is simple. The raw materials are all commercially available or can be prepared in-house, ensuring controllable costs and suitability for large-scale production. In addition, by controlling key process parameters, product performance can be customized to meet specific needs, demonstrating broad clinical application prospects. This solves the problems in existing technologies, such as poor stability of copper-based MOFs, easy pore blockage due to folic acid modification, poor controllability of copper ion release, and the rudimentary formulation of related wound products.

[0023] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0024] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein: Figure 1 A flowchart illustrating a method for preparing a hydrogel dressing according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the hydrogen nuclear magnetic resonance spectrum of HKUST-1 after digestion, provided in one embodiment of the present invention; Figure 3 This is a schematic diagram of the FTIR of HKUST-1 provided in one embodiment of the present invention; Figure 4 This is a schematic diagram of the unit cell of HKUST-1 provided in one embodiment of the present invention; Figure 5 This is a schematic diagram of the proton NMR spectrum of NOTT-100 after digestion, provided in one embodiment of the present invention. Figure 6 This is a schematic diagram of the hydrogen nuclear magnetic resonance spectrum of Cu-MOF-74 after digestion, provided in one embodiment of the present invention; Figure 7 This is a SEM image of the hydrogel dressing provided in Example 1 of this invention; Figure 8 This is a SEM image of the hydrogel dressing provided in Example 2 of this invention; Figure 9 This is a SEM image of the hydrogel dressing provided in Example 3 of this invention; Figure 10 This is a SEM image of the hydrogel dressing provided in Example 4 of this invention; Figure 11 This is a SEM image of the hydrogel dressing provided in Example 5 of this invention; Figure 12 SEM image of the hydrogel dressing provided in Comparative Example 1 of this invention; Figure 13 This is a SEM image of the hydrogel dressing provided in Comparative Example 2 of this invention; Figure 14 This is a SEM image of the hydrogel dressing provided in Comparative Example 3 of this invention; Figure 15 Comparison of X-ray diffraction patterns of MOFs samples from Example 3, Comparative Example 2, and Comparative Example 3 after immersion in FBS; Figure 16 This is a schematic diagram illustrating cell viability provided in an embodiment of the present invention; Figure 17 This is a schematic diagram of a digital camera capturing an image of a wound, provided in one embodiment of the present invention. Figure 18 This is a schematic diagram of the immunofluorescence staining results provided in one embodiment of the present invention. Detailed Implementation

[0025] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0026] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0027] The drug sources for this application are as follows: bacterial cellulose is a bacterial cellulose membrane prepared by static fermentation of Acetobacter xylinum, with a thickness of about 2-5 mm and a water content of >99%. Among them, Acetobacter xylinum was purchased from Beina Biotechnology; toluene isocyanate was purchased from Sigma-Aldrich with a purity of 99%; folic acid was purchased from Shanghai Maclean Biotechnology Co., Ltd. with a purity of 98%; and polyethylene glycol was purchased from Sigma-Aldrich.

[0028] Example 1

[0029] This invention provides a hydrogel dressing, the hydrogel dressing comprising the following weight proportions: Bacterial cellulose: 5 parts; Toluene isocyanate: 2 parts; Modified folic acid: 1 part; Metal-organic framework nanoparticles: 2 parts; Solvent: 80 parts.

[0030] The modified folic acid is formulated in the following weight proportions: Folic acid: 0.5 parts; Polyethylene glycol: 2 parts; Coupling agent: 0.1 parts; Catalyst: 0.01 parts; Reaction solvent: 10 parts.

[0031] The polyethylene glycol has a molecular weight of 2000-5000 Da; the coupling agent is selected from 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide; the catalyst is selected from 4-dimethylaminopyridine; and the reaction solvent is selected from dimethyl sulfoxide.

[0032] The metal-organic framework nanoparticles are copper-based metal-organic frameworks selected from HKUST-1, and the particle size of the metal-organic framework nanoparticles is 100-200 nm.

[0033] It should be noted that the preparation process of HKUST-1 is as follows: Copper nitrate trihydrate (Cu(NO3)2·3H2O, 0.5g) was dissolved in 10mL of deionized water to obtain a clear blue solution. Tristyric acid (H3BTC, 0.25g) was dissolved in 10mL of anhydrous ethanol to obtain a colorless clear solution. After mixing the two solutions, triethylamine (0.1mL) was immediately added as a deprotonating agent, and the mixture was magnetically stirred (500rpm) at room temperature for 1 hour. During the reaction, the solution gradually became turbid, eventually forming a blue suspension. After the reaction was complete, the product was transferred to a centrifuge tube and centrifuged at 8000 rpm for 5 minutes, discarding the supernatant. The precipitate was washed three times (10 mL each) with N,N-dimethylformamide (DMF) and three times (10 mL each) with anhydrous ethanol to remove unreacted starting materials and byproducts. The washed product was then vacuum-dried overnight at 60 °C to obtain blue powdery HKUST-1 nanoparticles.

[0034] The blue powdery HKUST-1 nanoparticles were tested, and the nuclear magnetic resonance spectrum was obtained, as shown below. Figure 2 As shown, HKUST-1 was successfully prepared using the above-described preparation method. Figure 3 As shown, different peak values ​​can be obtained from the in-field FTIR test, such as... Figure 4 As shown, the cell structure was exported using Vesta software, and the structure is stable and porous.

[0035] Among them, bacterial cellulose is nano-bacterial cellulose, with a fiber diameter of 20-100nm and a length of 1-10μm.

[0036] The solvent is selected from water.

[0037] In this process, modified folic acid is applied to the outer surface of metal-organic framework nanoparticles to form modified folic acid-modified metal-organic framework nanoparticles; wherein the molecular size of the modified folic acid is larger than the pore size of the metal-organic framework nanoparticles.

[0038] It should be noted that the pore size distribution of HKUST-1, determined using nitrogen adsorption-desorption isotherms, showed an average pore size of 0.95 nm; while the hydrodynamic radius of the folic acid-polyethylene glycol (PEG) conjugate in solution is 6.5 nm. Calculations show that the ratio of the molecular size of the PEG conjugate to the pore size of HKUST-1 is approximately 6.8, a difference of nearly seven times. This significant difference in magnitude physically eliminates the possibility of PEG molecules entering the internal pores of HKUST-1, limiting their application to selective modification of the outer surface of MOFs.

[0039] This invention also provides a method for preparing a hydrogel dressing, such as... Figure 1 As shown, the preparation method includes the following steps: S1. Preparation of modified folic acid: Folic acid, polyethylene glycol, coupling agent and catalyst are dissolved in a reaction solvent and reacted at 20°C for 12 hours. After purification, folic acid-polyethylene glycol coupling compound is obtained. S2. Preparation of folic acid-modified metal-organic framework nanoparticles: Disperse metal-organic framework nanoparticles in a solvent, add the modified folic acid obtained in step S1, react at 25°C for 2 hours, centrifuge and wash to obtain folic acid-modified metal-organic framework nanoparticles. S3. Preparation of bacterial cellulose dispersion: Disperse bacterial cellulose in a solvent and homogenize at 5000 rpm for 5 minutes to obtain a uniform bacterial cellulose dispersion with a mass percentage concentration of 3%. S4. Preparation of isocyanate-terminated polyethylene glycol: Toluene isocyanate and polyethylene glycol are mixed in a molar ratio of 2:1 and reacted in an anhydrous solvent at 40°C under nitrogen protection for 4 hours to obtain isocyanate-terminated polyethylene glycol. S5. Crosslinking reaction: The isocyanate-terminated polyethylene glycol obtained in step S4 is added to the bacterial cellulose dispersion obtained in step S3, and the reaction is carried out at 25°C for 2 hours to form a crosslinked network; S6. Composite and molding: The modified folic acid-modified metal-organic framework nanoparticles obtained in step S2 are added to the crosslinking system obtained in step S5, mixed evenly, ultrasonically degassed, and then cast into a mold. The mixture is allowed to stand at 25°C for 6 hours to form the hydrogel dressing.

[0040] In step S4, the anhydrous solvent is selected from dimethyl sulfoxide.

[0041] The present invention also provides the use of a hydrogel dressing in the preparation of a medicament for treating chronic, difficult-to-heal wounds, wherein the chronic, difficult-to-heal wounds are diabetic foot ulcers, pressure ulcers, or venous ulcers.

[0042] Example 2

[0043] This invention provides a hydrogel dressing, the hydrogel dressing comprising the following weight proportions: Bacterial cellulose: 6 parts; Toluene isocyanate: 4 parts; Modified folic acid: 2 parts; Metal-organic framework nanoparticles: 3 parts; Solvent: 90 parts.

[0044] The modified folic acid is formulated in the following weight proportions: Folic acid: 0.8 parts; Polyethylene glycol: 4 parts; Coupling agent: 0.3 parts; Catalyst: 0.03 parts; Reaction solvent: 20 parts.

[0045] The polyethylene glycol has a molecular weight of 2000-5000 Da; the coupling agent is selected from dicyclohexylcarbodiimide; the catalyst is selected from triethylamine; and the reaction solvent is selected from N,N-dimethylformamide.

[0046] The metal-organic framework nanoparticles are copper-based metal-organic frameworks selected from NOTT-100, and the particle size of the metal-organic framework nanoparticles is 100-200 nm.

[0047] It should be noted that the preparation process of NOTT-100 is as follows: Biphenyl-3,3',5,5'-tetracarboxylic acid (BPTC, 33 mg) and copper nitrate pentahydrate (Cu(NO3)2·2.5H2O, 100 mg) were dissolved in a mixed solvent of N,N-dimethylformamide (DMF) / deionized water (25 mL, volume ratio 2:1). 37% concentrated hydrochloric acid (20 μL) was added as a regulator. After stirring evenly, the mixture was transferred to a reaction vessel and reacted at 85°C for 24 hours. After the reaction, the mixture was allowed to cool naturally, and the precipitate was collected by centrifugation. It was washed three times each with warm DMF and anhydrous ethanol, and then vacuum-dried overnight at 60°C to obtain blue powdered NOTT-100 nanoparticles with an average particle size of approximately 150 nm, a BET specific surface area of ​​1275 m² / g, and a pore size of approximately 1.0 nm. The blue powdered NOTT-100 nanoparticles were tested, and the nuclear magnetic resonance spectrum was obtained, as shown below. Figure 5 As shown, NOTT-100 was successfully prepared using the above-described preparation method.

[0048] Among them, bacterial cellulose is nano-bacterial cellulose, with a fiber diameter of 20-100nm and a length of 1-10μm.

[0049] The solvent is selected from phosphate buffer.

[0050] In this process, modified folic acid is applied to the outer surface of metal-organic framework nanoparticles to form modified folic acid-modified metal-organic framework nanoparticles; wherein the molecular size of the modified folic acid is larger than the pore size of the metal-organic framework nanoparticles.

[0051] It should be noted that the pore size distribution of NOTT-100, determined using nitrogen adsorption-desorption isotherms, showed an average pore size of 1.02 nm; while the hydrodynamic radius of the folic acid-polyethylene glycol (PEG) conjugate in solution was 6.5 nm. Calculations showed that the ratio of the molecular size of the PEG conjugate to the pore size of NOTT-100 was approximately 6.4. This significant difference in magnitude physically eliminates the possibility of PEG molecules entering the internal pores of HKUST-1, limiting their application to selective modification of the outer surface of MOFs.

[0052] This invention also provides a method for preparing a hydrogel dressing, the method comprising the following steps: S1. Preparation of modified folic acid: Folic acid, polyethylene glycol, coupling agent and catalyst are dissolved in a reaction solvent and reacted at 25°C for 20 hours. After purification, folic acid-polyethylene glycol coupling compound is obtained. S2. Preparation of folic acid-modified metal-organic framework nanoparticles: Disperse metal-organic framework nanoparticles in a solvent, add the modified folic acid obtained in step S1, react at 33°C for 8 hours, centrifuge and wash to obtain folic acid-modified metal-organic framework nanoparticles. S3. Preparation of bacterial cellulose dispersion: Disperse bacterial cellulose in a solvent and homogenize at 8000 rpm for 10 minutes to obtain a uniform bacterial cellulose dispersion with a mass percentage concentration of 4%. S4. Preparation of isocyanate-terminated polyethylene glycol: Toluene isocyanate and polyethylene glycol are mixed in a molar ratio of 4:1 and reacted in an anhydrous solvent at 50°C under nitrogen protection for 9 hours to obtain isocyanate-terminated polyethylene glycol. S5. Crosslinking reaction: The isocyanate-terminated polyethylene glycol obtained in step S4 is added to the bacterial cellulose dispersion obtained in step S3, and the reaction is carried out at 33°C for 10 hours to form a crosslinked network; S6. Composite and molding: The modified folic acid-modified metal-organic framework nanoparticles obtained in step S2 are added to the crosslinking system obtained in step S5, mixed evenly, ultrasonically degassed, and then cast into a mold. The mixture is allowed to stand at 27°C for 10 hours to form the hydrogel dressing.

[0053] In step S4, the anhydrous solvent is selected from N,N-dimethylformamide.

[0054] The present invention also provides the use of a hydrogel dressing in the preparation of a medicament for treating chronic, difficult-to-heal wounds, wherein the chronic, difficult-to-heal wounds are diabetic foot ulcers, pressure ulcers, or venous ulcers.

[0055] Example 3

[0056] This invention provides a hydrogel dressing, the hydrogel dressing comprising the following weight proportions: Bacterial cellulose: 8 parts; Toluene isocyanate: 6 parts; Modified folic acid: 3 parts; Metal-organic framework nanoparticles: 6 parts; Solvent: 100 parts.

[0057] The modified folic acid is formulated in the following weight proportions: Folic acid: 1.0 part; Polyethylene glycol: 6 parts; Coupling agent: 0.5 parts; Catalyst: 0.05 parts; Reaction solvent: 30 parts.

[0058] The polyethylene glycol has a molecular weight of 2000-5000 Da; the coupling agent is selected from N-hydroxysuccinimide; the catalyst is selected from 4-dimethylaminopyridine; and the reaction solvent is selected from phosphate buffer.

[0059] Among them, the metal-organic framework nanoparticles are copper-based metal-organic frameworks, selected from at least one of Cu-MOF-74, and the particle size of the metal-organic framework nanoparticles is 100-200 nm.

[0060] It should be noted that the preparation process of Cu-MOF-74 is as follows: 2,5-dihydroxyterephthalic acid (DHTP, 74.5 mg) and copper nitrate trihydrate (Cu(NO3)2·3H2O, 400 mg) were dissolved in a mixed solvent of N,N-dimethylformamide (DMF) / isopropanol (60 mL, volume ratio 20:1) and stirred until completely dissolved. The solution was transferred to a reaction vessel and reacted at 80℃ for 18 hours. After the reaction was completed, the mixture was allowed to cool naturally, and the precipitate was collected by centrifugation. The precipitate was washed three times each with DMF and anhydrous ethanol, and then dried under vacuum at 60℃ overnight to obtain dark brown powdery Cu-MOF-74 nanoparticles. The average particle size of the obtained product was approximately 100-200 nm, and the BET specific surface area was 1122 m² / g. The dark brown powdery Cu-MOF-74 nanoparticles were tested, and the nuclear magnetic resonance spectrum was obtained, as shown below. Figure 6 As shown, Cu-MOF-74 was successfully prepared using the above method.

[0061] Among them, bacterial cellulose is nano-bacterial cellulose, with a fiber diameter of 20-100nm and a length of 1-10μm.

[0062] The solvent is selected from physiological saline.

[0063] In this process, modified folic acid is applied to the outer surface of metal-organic framework nanoparticles to form modified folic acid-modified metal-organic framework nanoparticles; wherein the molecular size of the modified folic acid is larger than the pore size of the metal-organic framework nanoparticles.

[0064] It should be noted that the pore size distribution of Cu-MOF-74, determined using nitrogen adsorption-desorption isotherms, showed an average pore size of 1.11 nm; while the hydrodynamic radius of the folic acid-polyethylene glycol (PEG) coupling in solution was 6.5 nm. Calculations showed that the ratio of the molecular size of the PEG coupling to the pore size of NOTT-100 was approximately 5.9. This significant difference in magnitude physically eliminates the possibility of PEG molecules entering the internal pores of Cu-MOF-74, limiting their application to selective modification of the outer surface of MOFs.

[0065] This invention also provides a method for preparing a hydrogel dressing, the method comprising the following steps: S1. Preparation of modified folic acid: Folic acid, polyethylene glycol, coupling agent and catalyst are dissolved in a reaction solvent and reacted at 30°C for 30 hours. After purification, folic acid-polyethylene glycol coupling product is obtained. S2. Preparation of folic acid-modified metal-organic framework nanoparticles: Disperse metal-organic framework nanoparticles in a solvent, add the modified folic acid obtained in step S1, react at 40°C for 14 hours, centrifuge and wash to obtain folic acid-modified metal-organic framework nanoparticles. S3. Preparation of bacterial cellulose dispersion: Bacterial cellulose was dispersed in a solvent and homogenized at 12000 rpm for 18 minutes to obtain a uniform bacterial cellulose dispersion with a mass percentage concentration of 5%. S4. Preparation of isocyanate-terminated polyethylene glycol: Toluene isocyanate and polyethylene glycol are mixed in a molar ratio of 5:1 and reacted in an anhydrous solvent at 60°C under nitrogen protection for 12 hours to obtain isocyanate-terminated polyethylene glycol. S5. Crosslinking reaction: The isocyanate-terminated polyethylene glycol obtained in step S4 is added to the bacterial cellulose dispersion obtained in step S3, and the reaction is carried out at 40°C for 12 hours to form a crosslinked network; S6. Composite and molding: The modified folic acid-modified metal-organic framework nanoparticles obtained in step S2 are added to the crosslinking system obtained in step S5, mixed evenly, degassed by ultrasonication, and then cast into a mold. The mixture is allowed to stand at 30°C for 15 hours to form the hydrogel dressing.

[0066] In step S4, the anhydrous solvent is selected from toluene.

[0067] The present invention also provides the use of a hydrogel dressing in the preparation of a medicament for treating chronic, difficult-to-heal wounds, wherein the chronic, difficult-to-heal wounds are diabetic foot ulcers, pressure ulcers, or venous ulcers.

[0068] Example 4

[0069] This invention provides a hydrogel dressing, the hydrogel dressing comprising the following weight proportions: Bacterial cellulose: 9 parts; Toluene isocyanate: 7 parts; Modified folic acid: 3 parts; Metal-organic framework nanoparticles: 7 parts; Solvent: 110 parts.

[0070] The modified folic acid is formulated in the following weight proportions: Folic acid: 1.2 parts; Polyethylene glycol: 8 parts; Coupling agent: 0.8 parts; Catalyst: 0.07 parts; Reaction solvent: 40 parts.

[0071] The polyethylene glycol has a molecular weight of 2000-5000 Da; the coupling agent is selected from 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide; the catalyst is selected from triethylamine; and the reaction solvent is selected from phosphate buffer.

[0072] The metal-organic framework nanoparticles are copper-based metal-organic frameworks selected from HKUST-1, and the particle size of the metal-organic framework nanoparticles is 100-200 nm.

[0073] Among them, bacterial cellulose is nano-bacterial cellulose, with a fiber diameter of 20-100nm and a length of 1-10μm.

[0074] The solvent is selected from ethanol.

[0075] In this process, modified folic acid is applied to the outer surface of metal-organic framework nanoparticles to form modified folic acid-modified metal-organic framework nanoparticles; wherein the molecular size of the modified folic acid is larger than the pore size of the metal-organic framework nanoparticles.

[0076] This invention also provides a method for preparing a hydrogel dressing, the method comprising the following steps: S1. Preparation of modified folic acid: Folic acid, polyethylene glycol, coupling agent and catalyst are dissolved in a reaction solvent and reacted at 35°C for 40 hours. After purification, folic acid-polyethylene glycol coupling compound is obtained. S2. Preparation of folic acid-modified metal-organic framework nanoparticles: Disperse metal-organic framework nanoparticles in a solvent, add the modified folic acid obtained in step S1, react at 50°C for 20 hours, centrifuge and wash to obtain folic acid-modified metal-organic framework nanoparticles. S3. Preparation of bacterial cellulose dispersion: Bacterial cellulose was dispersed in a solvent and homogenized at 18000 rpm for 22 minutes to obtain a uniform bacterial cellulose dispersion with a mass percentage concentration of 7%. S4. Preparation of isocyanate-terminated polyethylene glycol: Toluene isocyanate and polyethylene glycol are mixed in a molar ratio of 8:1 and reacted in an anhydrous solvent at 70°C under nitrogen protection for 20 hours to obtain isocyanate-terminated polyethylene glycol. S5. Crosslinking reaction: The isocyanate-terminated polyethylene glycol obtained in step S4 is added to the bacterial cellulose dispersion obtained in step S3, and the reaction is carried out at 50°C for 20 hours to form a crosslinked network; S6. Composite and molding: The modified folic acid-modified metal-organic framework nanoparticles obtained in step S2 are added to the crosslinking system obtained in step S5, mixed evenly, degassed by ultrasonication, and then cast into a mold. The mixture is allowed to stand at 33°C for 20 hours to obtain the hydrogel dressing.

[0077] In step S4, the anhydrous solvent is selected from N,N-dimethylformamide.

[0078] The present invention also provides the use of a hydrogel dressing in the preparation of a medicament for treating chronic, difficult-to-heal wounds, wherein the chronic, difficult-to-heal wounds are diabetic foot ulcers, pressure ulcers, or venous ulcers.

[0079] Example 5

[0080] This invention provides a hydrogel dressing, the hydrogel dressing comprising the following weight proportions: Bacterial cellulose: 10 parts; Toluene isocyanate: 8 parts; Modified folic acid: 4 parts; Metal-organic framework nanoparticles: 8 parts; Solvent: 120 parts.

[0081] The modified folic acid is formulated in the following weight proportions: Folic acid: 1.5 parts; Polyethylene glycol: 10 parts; Coupling agent: 1 part; Catalyst: 0.1 parts; Reaction solvent: 50 parts.

[0082] The polyethylene glycol has a molecular weight of 2000-5000 Da; the coupling agent is selected from N-hydroxysuccinimide; the catalyst is selected from 4-dimethylaminopyridine; and the reaction solvent is selected from N,N-dimethylformamide.

[0083] The metal-organic framework nanoparticles are copper-based metal-organic frameworks selected from NOTT-100, and the particle size of the metal-organic framework nanoparticles is 100-200 nm.

[0084] Among them, bacterial cellulose is nano-bacterial cellulose, with a fiber diameter of 20-100nm and a length of 1-10μm.

[0085] The solvent is selected from dimethyl sulfoxide.

[0086] In this process, modified folic acid is applied to the outer surface of metal-organic framework nanoparticles to form modified folic acid-modified metal-organic framework nanoparticles; wherein the molecular size of the modified folic acid is larger than the pore size of the metal-organic framework nanoparticles.

[0087] This invention also provides a method for preparing a hydrogel dressing, the method comprising the following steps: S1. Preparation of modified folic acid: Folic acid, polyethylene glycol, coupling agent and catalyst are dissolved in a reaction solvent and reacted at 40°C for 48 hours. After purification, folic acid-polyethylene glycol coupling product is obtained. S2. Preparation of folic acid-modified metal-organic framework nanoparticles: Disperse metal-organic framework nanoparticles in a solvent, add the modified folic acid obtained in step S1, react at 60°C for 24 hours, centrifuge and wash to obtain folic acid-modified metal-organic framework nanoparticles. S3. Preparation of bacterial cellulose dispersion: Bacterial cellulose was dispersed in a solvent and homogenized at 20,000 rpm for 30 minutes to obtain a uniform bacterial cellulose dispersion with a mass percentage concentration of 8%. S4. Preparation of isocyanate-terminated polyethylene glycol: Toluene isocyanate and polyethylene glycol are mixed in a molar ratio of 10:1 and reacted in an anhydrous solvent at 80°C under nitrogen protection for 24 hours to obtain isocyanate-terminated polyethylene glycol. S5. Crosslinking reaction: The isocyanate-terminated polyethylene glycol obtained in step S4 is added to the bacterial cellulose dispersion obtained in step S3, and the reaction is carried out at 60°C for 24 hours to form a crosslinked network; S6. Composite and molding: The modified folic acid-modified metal-organic framework nanoparticles obtained in step S2 are added to the crosslinking system obtained in step S5, mixed evenly, ultrasonically degassed, and then cast into a mold. The mixture is allowed to stand at 37°C for 24 hours to form the hydrogel dressing.

[0088] In step S4, the anhydrous solvent is selected from dimethyl sulfoxide.

[0089] The present invention also provides the use of a hydrogel dressing in the preparation of a medicament for treating chronic, difficult-to-heal wounds, wherein the chronic, difficult-to-heal wounds are diabetic foot ulcers, pressure ulcers, or venous ulcers.

[0090] Comparative Example 1 The difference from Example 1 is that the weight proportions of the hydrogel dressing include: Bacterial cellulose: 5 parts; Modified folic acid: 1 part; Metal-organic framework nanoparticles: 2 parts; Solvent: 80 parts.

[0091] The preparation process for the remaining components is the same as in Example 1.

[0092] Comparative Example 2 The difference from Example 1 is that the weight proportions of the hydrogel dressing include: Bacterial cellulose: 5 parts; Toluene isocyanate: 2 parts; Folic acid: 1 serving; Metal-organic framework nanoparticles: 2 parts; Solvent: 80 parts.

[0093] The preparation process for the remaining components is the same as in Example 1.

[0094] Comparative Example 3 The difference from Example 1 is that the weight proportions of the hydrogel dressing include: Bacterial cellulose: 5 parts; Metal-organic framework nanoparticles: 2 parts; Solvent: 80 parts.

[0095] The preparation process for the remaining components is the same as in Example 1.

[0096] Performance testing

[0097] Examples 1-5 and Comparative Examples 1-3 of this application were tested. The tensile strength and elongation at break of the hydrogel dressing were determined using a universal testing machine. The sample size was 50 mm × 10 mm × 2 mm, and the tensile rate was 10 mm / min. The dried hydrogel dressing was weighed, immersed in PBS buffer at 37°C, and removed at different time points. The surface moisture was blotted with filter paper and weighed again to calculate the swelling rate. The water contact angle of the surface of the hydrogel dressing was measured using a contact angle meter to evaluate its hydrophilicity and hydrophobicity. The results are shown in Table 1 below.

[0098] Table 1 Basic Performance Tests

[0099] As shown in Table 1, the hydrogel dressings prepared in Examples 1-5 of the present invention have excellent comprehensive performance, while Comparative Examples 1-3 have obvious defects in each performance index, which fully demonstrates the advanced nature of the technical solution of the present invention and the necessity of the synergistic effect of each component.

[0100] First, the tensile strength of Examples 1-5 of this invention reached 2.8-3.5 MPa, and the elongation at break was 310-380%, with Example 3 showing the best performance (tensile strength 3.5 MPa, elongation at break 380%). This indicates that the covalently cross-linked network constructed by toluene isocyanate forms an effective structure with the bacterial cellulose nanofiber skeleton, giving the dressing both high strength and high flexibility. It can form a film independently and also closely adhere to irregular wounds on moving parts such as joints. In contrast, Comparative Example 1 (without chemical cross-linking) had a tensile strength of only 0.1 MPa and an elongation at break of only 40%, with extremely low mechanical properties, failing to form a self-supporting film. This demonstrates the decisive role of toluene isocyanate chemical cross-linking in mechanical properties. The mechanical properties of Comparative Examples 2 and 3 (2.6-2.7 MPa, 290-300%) were slightly lower than those of Example 1, indicating that the introduction of modified folic acid also contributed to the integrity of the network structure.

[0101] Secondly, the 24-hour swelling rates of Examples 1-5 ranged from 1050% to 1350%, with Example 3 showing the lowest (1050%). This indicates that the chemical cross-linking network effectively limited the excessive swelling of the hydrogel, maintaining structural stability while absorbing wound exudate and avoiding a decline in mechanical properties and excessive pressure on the wound due to excessive swelling. Comparative Example 1 exhibited a swelling rate as high as 2800%, a typical example of the inability of the non-cross-linked network to limit water absorption. The swelling rates of Comparative Examples 2 and 3 (1650% and 2200%, respectively) were also significantly higher than that of Example 1, indicating that the folic acid-polyethylene glycol coupling modification and the presence of folic acid have a positive effect on the regularity of the network structure and its anti-swelling ability.

[0102] Furthermore, the water contact angles of Examples 1-5 ranged from 45.2° to 55.1°, with Example 3 exhibiting the smallest (45.2°), demonstrating good hydrophilicity, which is beneficial for absorbing wound exudate and maintaining a moist microenvironment. Comparative Example 2 showed a water contact angle as high as 68.2°, indicating that small-molecule folic acid modification significantly increased the hydrophobicity of the MOF. However, the present invention successfully avoided this problem by using a folic acid-polyethylene glycol coupling macromolecular modification, thus maintaining good hydrophilicity in the dressing.

[0103] like Figure 7 , Figure 8 , Figure 9 , Figure 10 and Figure 11As shown in the scanning electron microscope images of the hydrogel dressings prepared in Examples 1-5 of this application, MOF nanoparticles are uniformly dispersed in the bacterial cellulose network. The particles have regular morphology and clear boundaries, with no obvious damage or aggregation. This demonstrates that the selective surface modification of the folic acid-polyethylene glycol conjugate effectively maintains the structural integrity of the MOF and exhibits excellent stability in hydrogel preparation and physiological environments. Figure 12 , Figure 13 and Figure 14 As shown, after the samples of Comparative Examples 1-3 were soaked in FBS, the MOF particles showed obvious morphological blurring, edge collapse, and even complete fragmentation, confirming that the structural stability of MOFs that were not modified or only modified with small molecule folic acid was much lower than that of the embodiments of the present invention.

[0104] like Figure 15 As shown, to further verify the stability of the MOF crystal structure, X-ray diffraction analysis was performed on Example 3. After immersion in FBS, the modified MOFs still exhibited clear and sharp characteristic diffraction peaks, essentially consistent with the unimmersed standard sample. However, under the same conditions, the characteristic diffraction peak indices of Comparative Examples 2 and 3 decreased significantly or even disappeared completely. The XRD results were highly consistent with SEM observations, jointly confirming that the folic acid-polyethylene glycol macromolecular surface modification strategy employed in this invention effectively blocks protein attack on the MOF backbone without clogging the pores, thereby significantly improving the structural stability of copper-based MOFs in the physiological environment.

[0105] In summary, Example 3 exhibits the best performance across all performance indicators and is the preferred embodiment of the present invention. In this formulation, the amount of toluene isocyanate is 6 parts, achieving the optimal crosslinking density, ensuring the hydrogel network is fully crosslinked without becoming excessively rigid; the folic acid-polyethylene glycol coupling agent-modified MOF is uniformly dispersed within the network, achieving a balance between stability and activity.

[0106] Toxicity tests were performed on Examples 1-5 and Comparative Examples 1-3 of this application. L929 mouse fibroblasts were seeded at a density of 5 × 10³ cells / well in 96-well plates and cultured for 24 hours. Sample extracts (prepared according to ISO 10993-12 standard) at different concentrations (0.1, 0.5, 1, 5, 10 mg / mL) were added, and the cells were cultured for another 48 hours. MTT solution was added and incubated for 4 hours to dissolve the formazan crystals. The absorbance at 570 nm was measured, and cell viability was calculated.

[0107] like Figure 16As shown, Examples 1-5 of this invention exhibited excellent cell compatibility at various concentrations, with cell viability curves decreasing gradually and remaining at a high level throughout the 0.1-10 mg / mL concentration range. Even at a high concentration (10 mg / mL), cell viability remained above 76%, with Example 3 showing the best result (88.6%). All examples had IC50 values ​​greater than 10 mg / mL, meeting the requirements of ISO 10993-5 for biocompatibility of medical devices. This indicates that the selective surface modification of the folic acid-polyethylene glycol conjugate effectively stabilized the MOF structure, preventing the rapid release of copper ions. Simultaneously, the chemical cross-linking network firmly immobilized the MOFs, preventing free particles from contacting cells and significantly reducing the cytotoxicity of the material.

[0108] Comparative Example 1 (without cross-linking network) showed the highest cytotoxicity, with a steep drop in the curve. At a concentration of 10 mg / mL, the cell survival rate was only 32.5%, and the IC50 was 1.8 mg / mL. This indicates that without chemical cross-linking fixation, MOF particles are easily taken up by cells or rapidly degraded, releasing high concentrations of copper ions, leading to severe cytotoxicity. Comparative Example 3 (unmodified folic acid) also showed high cytotoxicity (38.5% at 10 mg / mL, IC50 = 4.2 mg / mL), demonstrating that folic acid-PEG conjugate modification plays a crucial role in reducing toxicity. Comparative Example 2 (modified with small molecule folic acid) showed intermediate toxicity (52.3% at 10 mg / mL, IC50 = 8.5 mg / mL), indicating that while small molecule folic acid can partially reduce toxicity, its effect is far less than that of the large molecule modification of the folic acid-PEG conjugate of this invention.

[0109] Staphylococcus aureus and Escherichia coli were respectively spread on LB agar plates. Samples from Examples 1-5 and Comparative Examples 1-3 of this application were made into discs with a diameter of 6 mm, affixed to the center of the plates, and incubated at 37°C for 24 hours. The diameter of the inhibition zone was measured, and the results are shown in Table 2 below.

[0110] Table 2 Antibacterial Performance Test

[0111] As shown in Table 2, Examples 1-5 of this application exhibit significant antibacterial activity against Staphylococcus aureus and Escherichia coli, with Example 3 showing the strongest antibacterial activity (16.1 mm for Staphylococcus aureus and 14.5 mm for Escherichia coli). Comparative Example 2, while showing some antibacterial effect (12.6 mm and 10.8 mm), is weaker than the examples of this invention. Comparative Examples 1 and 3 showed no inhibition zones, confirming that the antibacterial activity originates from copper ions released by MOFs.

[0112] To verify the therapeutic effect of the hydrogel dressing of the present invention on chronic refractory wounds, referring to the classic diabetic mouse wound healing experiment method, db / db diabetic mice were used as experimental subjects. Examples 1-5 of the present invention, comparative examples 1-3, and a blank control group were set up to carry out a wound healing comparison experiment. The wound healing rate, histopathological indicators, and angiogenesis level were systematically detected. The specific experimental scheme and results are as follows.

[0113] Eight-week-old male db / db diabetic mice (BKS.Cg-m+ / +Leprdb), weighing 22-26g, were selected and housed in a constant temperature (22±2℃) and constant humidity (50±5%) environment with 12-hour light-dark cycles and free access to food and water. After one week of acclimatization, experiments were conducted. The hydrogel dressings prepared in Examples 1-5 and the dressings prepared in Comparative Examples 1-3 were all cut into circular sheets with a diameter of 8mm and sterilized with 60Co γ-rays (irradiation dose 25kGy) before use. The blank control group used sterile medical gauze of the same size.

[0114] After the mice underwent acclimatization, fasting blood glucose was measured by blood collection from the tail vein. Mice with blood glucose levels ≥16.7 mmol / L were selected for the experiment. Before the experiment, the mice were fasted for 12 hours and anesthetized by intraperitoneal injection of 10% chloral hydrate at a dose of 300 mg / kg body weight. After anesthesia, the hair on the back of the mice was removed (the hair removal cream was applied for 5 minutes and then washed off with saline). The skin on the back was disinfected with povidone-iodine. Two full-thickness skin excision wounds (6 mm in diameter, reaching the fascia layer) were symmetrically made on both sides of the spine using a sterile punch, ensuring that the size and depth of the wounds were consistent. After hemostasis, the wounds were prepared for use.

[0115] The successfully modeled diabetic mice were randomly divided into 9 groups of 10 mice each. Each mouse had two wounds as parallel samples. The wound treatment methods for each group were as follows: Examples 1-5: The hydrogel dressings corresponding to the examples were applied to the wounds, covered and fixed with sterile medical gauze, and the dressings were changed every 3 days. Comparative Examples 1-3: Apply the corresponding proportion of dressings to the wound, cover and fix with sterile medical gauze, and change the dressing once every 3 days; Blank control group: Sterile medical gauze was applied to the wound and fixed in place as usual, and the dressing was changed once every 3 days.

[0116] On day 21 after modeling, five mice were randomly selected from each group and euthanized by intraperitoneal injection of an excessive amount of chloral hydrate. Skin tissue from the wound and surrounding 0.5 cm was taken, fixed with 4% paraformaldehyde solution for 24 h, routinely dehydrated, embedded in paraffin, and 5 μm serial sections were prepared for immunofluorescence staining.

[0117] The experimental results are as follows: None of the mice died, and their mental state, diet and water intake were basically normal. In the blank control group and the three comparative groups, some mice showed slight exudation and redness on the wounds from day 3 to day 7, and a small number of wounds showed infection under the scab. The mice in the 1-5 examples and the 1-3 comparative groups showed no bleeding or infection on the wounds throughout the process. The dressings adhered well and did not fall off. There was no redness or inflammation on the skin around the wounds.

[0118] The wound was photographed with a digital camera on days 3, 7, 10, 14 and 21 after modeling. The wound area was measured using ImageJ image analysis software. The wound healing rate was calculated using the following formula: Wound healing rate (%) = (Initial wound area - Wound area on day n) / Initial wound area × 100%. The results are shown in Table 3.

[0119] Table 3 Wound healing rate

[0120] As shown in Table 3, the wound healing rates of groups 1-5 of this invention at each time point were significantly higher than those of the blank control group and the comparative group (P<0.01). Group 3 of this invention showed the best results. Figure 17 As shown, the wound healing rate reached 85.2% on day 14 and 97.5% on day 21, with the wound essentially completely closed. While Comparative Example 2 showed some healing-promoting effect (89.5% on day 21), it was significantly weaker than the group in the present invention. The healing rates of Comparative Example 1 and Comparative Example 3 were 82.3% and 85.6%, respectively, slightly higher than the blank control group (75.6%), but significantly lower than the group in the present invention.

[0121] On day 21 after modeling, the wound tissues of mice in each group were stained with Masson's trichrome and immunofluorescence staining for eNOS, α-SMA, VEGF, and CD68. The results showed: Examples 1-5: The wound achieved complete epithelialization, with a sufficient thickness and dense structure of granulation tissue, abundant and orderly collagen fiber deposition; the number of microvessels double-positive for eNOS and α-SMA was significantly increased, with intact vascular morphology and uniform distribution in the granulation tissue; VEGF protein expression was significantly upregulated; there was almost no CD68-positive inflammatory cell infiltration in the wound area; and the inflammatory response completely subsided. Among these, such as... Figure 18 As shown, the collagen deposition, microvascular density, and VEGF expression level of Group 3 in Example 3 were the highest among all groups, indicating the best tissue repair effect.

[0122] Comparative Example 2: The wound had partially epithelialized, and the thickness of the granulation tissue and the amount of collagen deposition were lower than those in the Example 1 group. The collagen fiber arrangement was relatively disordered. There were fewer eNOS / α-SMA double-positive microvessels, the VEGF expression level was moderate, and a small number of CD68 positive inflammatory cells were visible in the local wound area, indicating that a mild inflammatory response still existed.

[0123] Comparative Example 1 and Comparative Example 3: The wound surface showed incomplete epithelialization, obvious epithelial defects, loose and thin granulation tissue layer, low collagen deposition and disordered arrangement; sparse distribution and incomplete morphology of microvessels, significantly reduced VEGF expression level, and a large number of CD68 positive inflammatory cells infiltrated the local wound surface, with slow inflammation resolution.

[0124] Blank control group: The degree of epithelialization of the wound surface was extremely low, the formation of granulation tissue was insufficient, and the deposition of collagen fibers was extremely low; there was almost no formation of mature eNOS / α-SMA double positive microvessels, the VEGF expression level was the lowest among all groups, and a large number of CD68 positive inflammatory cells were visible in the local wound surface, indicating a significant inflammatory response.

[0125] In summary, this application successfully developed a multifunctional hydrogel dressing that possesses excellent mechanical properties, controllable swelling behavior, good hydrophilicity, low cytotoxicity, broad-spectrum antibacterial activity, and significant healing-promoting effects. It employs a folic acid-polyethylene glycol (PEG) conjugate macromolecule to selectively modify the surface of copper-based MOFs. Utilizing the fact that its molecular size (6.5 nm) is significantly larger than the MOF pore size (0.95-1.1 nm), precise control is achieved by modifying only the outer surface without clogging the pores, solving the technical challenge of "sacrificing activity for stability" in traditional small-molecule folic acid modification. Simultaneously, through the synergistic effect of the covalent cross-linked network constructed with toluene isocyanate and the bacterial cellulose nanofiber skeleton, the dressing exhibits both high strength (tensile strength 3.5 MPa) and high flexibility (elongation at break 380%), and its swelling behavior can be controlled (1050% swelling rate in 24 hours). A diabetic mouse wound model confirmed that the wound healing rate in the Example 3 group reached 85.2% on day 14, and the healing half-life was significantly shortened, 7.5 days shorter than that in the blank control group. Histological analysis showed that it could effectively promote re-epithelialization, collagen deposition, angiogenesis and inhibit inflammatory response.

[0126] This invention significantly enhances the structural stability of MOFs in physiological environments through surface modification with folic acid-polyethylene glycol conjugates without clogging the MOF channels, thereby effectively controlling copper ion release, reducing cytotoxicity, and imparting good hydrophilicity to the dressing. A covalently cross-linked network constructed using toluene isocyanate endows the hydrogel with excellent mechanical properties and controllable swelling behavior. The bacterial cellulose nanofiber network provides a biomimetic scaffold and physical barrier. The synergistic effect of these three components ultimately enables this multifunctional hydrogel dressing to exhibit broad-spectrum antibacterial activity in vitro and achieve significant healing-promoting effects in a diabetic mouse chronic wound model.

[0127] This application proposes a hydrogel dressing that precisely modifies the outer surface of copper-based MOFs using a folic acid-polyethylene glycol coupling agent. This addresses the issues of easy collapse and copper ion release in the physiological environment while preserving the integrity of the pores to ensure long-term, controllable release of copper ions. A three-dimensional covalent cross-linked network is constructed using toluene isocyanate to enhance the hydrogel's mechanical properties and MOF fixation. Combined with the biomimetic scaffold, moisturizing properties, dual antibacterial activity, and biocompatibility advantages of bacterial cellulose, a high-performance hydrogel dressing is prepared using a controllable and environmentally friendly method. This effectively solves the core problems of poor stability of existing copper-based MOFs, easy pore blockage due to folic acid modification, poor control of copper ion release, and the rudimentary formulation of related wound care products.

[0128] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A hydrogel dressing, characterized in that, The hydrogel dressing is formulated in the following weight proportions: Bacterial cellulose: 5-10 parts; Toluene isocyanate: 2-8 parts; Modified folic acid: 1-4 parts; Metal-organic framework nanoparticles: 2-8 parts; Solvent: 80-120 parts; The modified folic acid is applied to the outer surface of the metal-organic framework nanoparticles to form modified folic acid-modified metal-organic framework nanoparticles; wherein the molecular size of the modified folic acid is larger than the pore size of the metal-organic framework nanoparticles, and the metal-organic framework nanoparticles are copper-based metal-organic frameworks. The preparation method of the hydrogel dressing includes the following steps: S1. Preparation of modified folic acid: Folic acid, polyethylene glycol, coupling agent and catalyst are dissolved in a reaction solvent and reacted at 20-40℃ for 12-48 hours. After purification, folic acid-polyethylene glycol coupling product is obtained. S2. Preparation of folic acid-modified metal-organic framework nanoparticles: Disperse metal-organic framework nanoparticles in a solvent, add the modified folic acid obtained in step S1, react at 25-60℃ for 2-24 hours, centrifuge and wash to obtain folic acid-modified metal-organic framework nanoparticles. S3. Preparation of bacterial cellulose dispersion: Disperse bacterial cellulose in a solvent and homogenize at 5000-20000 rpm for 5-30 minutes to obtain a uniform bacterial cellulose dispersion with a mass percentage concentration of 3-8%. S4. Preparation of isocyanate-terminated polyethylene glycol: Toluene isocyanate and polyethylene glycol are mixed in a molar ratio of (2-10):1 and reacted in an anhydrous solvent at 40-80°C under nitrogen protection for 4-24 hours to obtain isocyanate-terminated polyethylene glycol. S5. Crosslinking reaction: The isocyanate-terminated polyethylene glycol obtained in step S4 is added to the bacterial cellulose dispersion obtained in step S3, and the reaction is carried out at 25-60℃ for 2-24 hours to form a crosslinked network; S6. Composite and molding: The modified folic acid-modified metal-organic framework nanoparticles obtained in step S2 are added to the crosslinking system obtained in step S5, mixed evenly, ultrasonically degassed, and then cast into a mold. The mixture is allowed to stand at 25-37℃ for 6-24 hours to obtain the hydrogel dressing.

2. The hydrogel dressing according to claim 1, characterized in that, The modified folic acid is formulated in the following weight proportions: Folic acid: 0.5-1.5 parts; Polyethylene glycol: 2-10 parts; Coupling agent: 0.1-1 part; Catalyst: 0.01-0.1 parts; Reaction solvent: 10-50 parts.

3. The hydrogel dressing according to claim 2, characterized in that, The polyethylene glycol in the modified folic acid has a molecular weight of 2000-5000 Da; the coupling agent is selected from at least one of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, dicyclohexylcarbodiimide, and N-hydroxysuccinimide; the catalyst is selected from at least one of 4-dimethylaminopyridine and triethylamine; and the reaction solvent is selected from at least one of dimethyl sulfoxide, N,N-dimethylformamide, and phosphate buffer.

4. The hydrogel dressing according to claim 1, characterized in that, The metal-organic framework nanoparticles are copper-based metal-organic frameworks, selected from at least one of HKUST-1, NOTT-100, and Cu-MOF-74, and the particle size of the metal-organic framework nanoparticles is 100-200 nm.

5. A hydrogel dressing according to claim 1, characterized in that, The bacterial cellulose is nano-bacterial cellulose, with a fiber diameter of 20-100 nm and a length of 1-10 μm.

6. The hydrogel dressing according to claim 1, characterized in that, The solvent in the formulation of the hydrogel dressing is selected from water, phosphate buffer, physiological saline, ethanol or dimethyl sulfoxide.

7. The method for preparing the hydrogel dressing according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: S1. Preparation of modified folic acid: Folic acid, polyethylene glycol, coupling agent and catalyst are dissolved in a reaction solvent and reacted at 20-40℃ for 12-48 hours. After purification, folic acid-polyethylene glycol coupling product is obtained. S2. Preparation of folic acid-modified metal-organic framework nanoparticles: Disperse metal-organic framework nanoparticles in a solvent, add the modified folic acid obtained in step S1, react at 25-60℃ for 2-24 hours, centrifuge and wash to obtain folic acid-modified metal-organic framework nanoparticles. S3. Preparation of bacterial cellulose dispersion: Disperse bacterial cellulose in a solvent and homogenize at 5000-20000 rpm for 5-30 minutes to obtain a uniform bacterial cellulose dispersion with a mass percentage concentration of 3-8%. S4. Preparation of isocyanate-terminated polyethylene glycol: Toluene isocyanate and polyethylene glycol are mixed in a molar ratio of (2-10):1 and reacted in an anhydrous solvent at 40-80°C under nitrogen protection for 4-24 hours to obtain isocyanate-terminated polyethylene glycol. S5. Crosslinking reaction: The isocyanate-terminated polyethylene glycol obtained in step S4 is added to the bacterial cellulose dispersion obtained in step S3, and the reaction is carried out at 25-60℃ for 2-24 hours to form a crosslinked network; S6. Composite and molding: The modified folic acid-modified metal-organic framework nanoparticles obtained in step S2 are added to the crosslinking system obtained in step S5, mixed evenly, ultrasonically degassed, and then cast into a mold. The mixture is allowed to stand at 25-37℃ for 6-24 hours to obtain the hydrogel dressing.

8. The method for preparing the hydrogel dressing according to claim 7, characterized in that, In step S4, the anhydrous solvent is selected from dimethyl sulfoxide, N,N-dimethylformamide, or toluene.

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