An adhesive hydrogel, its preparation method and application in wound dressings

Abstract

The present invention provides an adhesive hydrogel, a preparation method thereof, and an application in wound dressings. The adhesive hydrogel of the present invention is made from the following raw materials in parts by weight: 2 to 3 parts of a thermosensitive hydrogel skeleton, 0.1 to 0.7 parts of polyzwitterionic microgel, and 0 to 0.02 parts of polydopamine; the thermosensitive hydrogel skeleton is composed of a thermosensitive polymer; the polyzwitterionic microgel is made from polyzwitterion and acrylic acid as raw materials. The adhesive hydrogel prepared by the present invention has excellent adhesion, antibacterial property, and mechanical properties, has the ability to pull the wound closed and promote wound healing, and has good biocompatibility; the double-layer hydrogel prepared based on the adhesive hydrogel can also achieve the effect of anti-fouling on the upper layer and adhesion on the lower layer, and has great application potential in the field of wound dressings.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and particularly relates to a thermosensitive hydrogel wound dressing, a preparation method thereof and an application thereof. Background Art

[0002] A variety of wound dressings are used to treat wounds, such as gauze, film dressings, foam dressings, hypertonic saline dressings and hydrogel dressings, etc. Among them, hydrogel dressings are a current research hotspot, and a variety of hydrogels that promote wound healing have been used in medical practice, such as alginate (Alg), hyaluronic acid (HA), dextran (Dex), chitosan (Chi), etc. These hydrogels have excellent biocompatibility and biodegradability, are non-toxic to the human body, and can absorb the tissue fluid exuded from the wound while having a high water content. However, for actual wounds, the functions of the above-mentioned hydrogels are too single, and it is of practical significance to develop a multifunctional hydrogel wound dressing.

[0003] Poly(N-isopropylacrylamide) (PNIPAM) is a widely studied thermosensitive polymer and has good biocompatibility. The molecular chain of PNIPAM contains hydrophobic isopropyl groups and hydrophilic amide groups. When the temperature is higher than its lower critical solution temperature (LCST~33°C), the hydrophobicity of the isopropyl groups plays a role, the molecular chain spacing becomes smaller, and the polymer shows volume shrinkage. When the temperature is lower than its LCST, the polymer swells by absorbing water. Due to the advantages of the volume phase transition behavior of PNIPAM at a certain temperature, intelligent hydrogels based on PNIPAM are widely used in many fields, such as sensors, actuators, wound dressings, etc. When using PNIPAM hydrogel as a wound dressing, in order to make full use of its thermosensitive phase transition characteristics, materials with strong adhesion performance need to be combined to drive wound closure. At present, the strategies for endowing PINIPAM with adhesion performance mainly include compounding substances that can provide adhesion, such as chitosan and polydopamine (PDA), into PINIPAM. However, the adhesion strength provided by chitosan and PDA is relatively limited, and chitosan has poor mechanical properties. After adding it to the PNIPAM hydrogel, it often reduces the mechanical properties of the hydrogel; there is also a certain degree of uncertainty in the dosage control of PDA, and inappropriate dosage may also reduce the mechanical properties of the hydrogel; the reduction of the mechanical properties of the hydrogel will in turn have an adverse effect on the adhesion strength.

[0004] In addition to the adhesion performance, considering that open wounds are vulnerable to bacterial infection, researchers will add antibacterial materials to the hydrogel to endow the hydrogel with antibacterial ability. Commonly used antibacterial materials include antibiotics, antimicrobial peptides, and nanomaterials, etc. However, the use of antibiotics is likely to lead to microbial drug resistance, making treatment more difficult; the high cost and complex preparation process of antimicrobial peptides limit their application; silver nanoparticles (AgNPs), copper nanoparticles (CuNPs), and metal oxide nanoparticles, etc. have all been reported to have good antibacterial ability, but they may have cytotoxicity, which makes them controversial.

[0005] Therefore, it is a key point and difficulty in current research and development to provide a hydrogel for wound dressings that has multiple functions such as thermosensitivity, adhesion, and antibacterial property, and has excellent mechanical properties, low cost, and high safety. Summary of the Invention

[0006] The purpose of the present invention is to provide an adhesive hydrogel with good application prospects in wound dressings. PNIPAM is used as the matrix material of the thermosensitive hydrogel, and polyzwitterionic microgels and polydopamine nanoparticles (PDANPs) are added as fillers. Choosing poly(N-isopropylacrylamide) (PNIPAM) as the backbone of the hydrogel is to utilize its thermosensitive property to undergo a phase change and volume shrinkage at human body temperature, thereby pulling the wound closed. The polyzwitterionic microgels improve the adhesion strength of the hydrogel. PDA NPs can not only improve the crosslinking density and mechanical strength of the hydrogel, but also the large number of catechol groups on its surface can improve the adhesion ability of the hydrogel and endow the hydrogel with antioxidant ability at the same time. The photothermal response ability of PDANPs also enables the hydrogel to exhibit excellent antibacterial effects.

[0007] To achieve the above-mentioned invention purpose, the technical solution provided by the present invention is as follows:

[0008] The present invention provides an adhesive hydrogel, which is made from the following raw materials in parts by weight: 2 - 3 parts of a thermosensitive hydrogel backbone, 0.1 - 0.7 parts of polyzwitterionic microgels, and 0 - 0.02 parts of polydopamine;

[0009] The thermosensitive hydrogel backbone is composed of a thermosensitive polymer; the polyzwitterionic microgels are made from polyzwitterions and acrylic acid as raw materials.

[0010] Further, it is made from the following raw materials in parts by weight: 2.71 parts of a thermosensitive hydrogel backbone, 0.3 parts of polyzwitterionic microgels, and 0.005 - 0.02 parts of polydopamine.

[0011] Furthermore, it is made from the following raw materials in parts by weight: 2.71 parts of a thermosensitive hydrogel skeleton, 0.3 part of polyzwitterionic microgel, and 0.02 part of polydopamine; or 2.71 parts of a thermosensitive hydrogel skeleton, 0.3 part of polyzwitterionic microgel, and 0.01 part of polydopamine; or 2.71 parts of a thermosensitive hydrogel skeleton, 0.3 part of polyzwitterionic microgel, and 0.005 part of polydopamine.

[0012] Furthermore, the above polyzwitterionic microgel is particles with a particle size of 10 nm to 100 nm, and the polydopamine is particles with a particle size of 400 nm to 600 nm.

[0013] Furthermore, the mass ratio of the above polyzwitterion to acrylic acid is 1:(0.5 - 5), preferably 1:(2.5 - 3.5), and more preferably 1:2.5 or 1:3.5.

[0014] Furthermore, the above polyzwitterion is poly(sulfobetaine methacrylate).

[0015] Furthermore, the above thermosensitive polymer is made from a thermosensitive polymer monomer and a crosslinking agent; the thermosensitive polymer monomer is N - isopropylacrylamide, and the crosslinking agent is N,N’ - methylenebisacrylamide; the weight ratio of the thermosensitive polymer monomer to the crosslinking agent is (50 - 60):1, preferably 53.2:1.

[0016] The present invention also provides a preparation method of the above - mentioned adhesive hydrogel, which includes the following steps:

[0017] (1) Dissolve the thermosensitive polymer monomer, crosslinking agent, polyzwitterionic microgel, polydopamine, and initiator in an aqueous solvent to form a mixed solution;

[0018] (2) Add a catalyst to the mixed solution under an inert gas condition and mix well, and then let it stand at room temperature for 20 - 30 hours.

[0019] Furthermore, the above aqueous solvent is a PBS solution, the initiator is potassium persulfate, and the catalyst is N,N,N',N' - tetramethylethylenediamine; the dosage ratio of the thermosensitive polymer monomer, aqueous solvent, initiator, and catalyst is: (0.2 - 0.3) g:(2 - 2.5) g:(0.003 - 0.008) g:(2 - 10) μL.

[0020] The present invention also provides a double - layer hydrogel, the lower layer is the above - mentioned adhesive hydrogel, and the upper layer is a polyzwitterionic hydrogel; the polyzwitterionic hydrogel is made from a zwitterionic monomer and a crosslinking agent.

[0021] Preferably, the polyzwitterionic hydrogel is made from sulfobetaine methacrylate and N,N’ - methylenebisacrylamide.

[0022] The present invention also provides the use of the above-mentioned adhesive hydrogel or double-layer hydrogel in preparing wound dressings.

[0023] Advantages of the present invention: The adhesive hydrogel of the present invention has excellent adhesiveness, antibacterial property and mechanical properties, has the ability to pull wound closure and promote wound healing, and has good biocompatibility; the double-layer hydrogel prepared based on the adhesive hydrogel can also achieve the effects of anti-fouling on the upper layer and adhesion on the lower layer, and has great application potential in the field of wound dressings.

[0024] The "thermosensitive polymer" of the present invention refers to a polymer whose volume changes with temperature.

[0025] In the "double-layer hydrogel" of the present invention, the "lower layer" refers to the side close to the mold during film formation, and also the side that adheres to the wound during application; the "upper layer" refers to the side close to the air during film formation, and also the side that does not directly contact the wound during application.

[0026] Obviously, based on the above content of the present invention, according to the common general knowledge and conventional means in the art, without departing from the above basic technical idea of the present invention, various other forms of modifications, substitutions or changes can be made.

[0027] The following is a further detailed description of the above content of the present invention through specific embodiments in the form of examples. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. All technologies implemented based on the above content of the present invention fall within the scope of the present invention. Description of the Drawings

[0028] Figure 1 is the infrared spectrum diagram of the hydrogel, microgel and polydopamine nanoparticles of the present invention.

[0029] Figure 2 In a, it is the test result diagram of the adhesion performance of the NM1P0, NM3P0, NM5P0, NM7P0 hydrogels of Comparative Example 1 and Example 1 to pig skin, plastic, glass, aluminum sheet and cardboard; Figure 2 In b, it is the test result diagram of the adhesion performance of the NM3P0, NM3P 0.5 、NM3P1 and NM3P2 hydrogels of Example 1 to pig skin, plastic, glass, aluminum sheet and cardboard.

[0030] Figure 3 In a, it is the NM3P0, NM3P 0.5 、NM3P1 and NM3P2 hydrogels of the present invention under the irradiation of near-infrared laser at 0.5 W / cm 2 The temperature change diagram, Figure 3 In b, it is the NM3P0, NM3P 0.5 、NM3P1 and NM3P2 hydrogels of the present invention at 1 W / cm2 Temperature change diagram under near-infrared laser irradiation; Figure 3 In c, it is the temperature change diagram of NM3P1 hydrogel in the photothermal switching cycle state.

[0031] Figure 4 In a, NM3P0, NM3P 0.5 Photothermal antibacterial rate test result diagrams of NM3P0, NM3P Figure 4 In b, NM3P0, NM3P 0.5 Photothermal antibacterial rate test result diagrams of NM3P1 and NM3P2 hydrogels against Staphylococcus aureus.

[0032] Figure 5 It is the adsorption rate test result diagrams of the double-layer hydrogels D-NM3P0, D-NM3P 0.5 against Escherichia coli (E.coli) and Staphylococcus aureus (S.aureus) of D-NM3P1 and D-NM3P2 of the present invention.

[0033] Figure 6 It is the adsorption rate test result diagrams of the double-layer hydrogels D-NM3P0, D-NM3P 0.5 against different concentrations of BCA protein of D-NM3P1 and D-NM3P2 of the present invention.

[0034] Figure 7 It is the antioxidant rate test result diagrams of the double-layer hydrogels D-NM3P0, D-NM3P 0.5 against D-NM3P1 and D-NM3P2 of the present invention.

[0035] Figure 8 It is the hemolysis rate test result diagrams of the double-layer hydrogels D-NM3P0, D-NM3P 0.5 against D-NM3P1 and D-NM3P2 of the present invention.

[0036] Figure 9 It is the test result diagram of the promotion of wound healing by D-NM3P1 hydrogel of the present invention.

[0037] Figure 10 In a, it is the test result diagram of the expression of wound inflammatory factor IL-4 during the promotion of wound healing by D-NM3P1 hydrogel of the present invention; Figure 10 In b, it is the test result diagram of the expression of wound inflammatory factor TNF-α during the promotion of wound healing by D-NM3P1 hydrogel of the present invention; Figure 10 In c, it is the test result diagram of the expression of wound inflammatory factor IL-6 during the promotion of wound healing by D-NM3P1 hydrogel of the present invention; Figure 10Figure d shows the test results of the expression of wound inflammatory factor ITGb1 during the process of promoting wound healing by the D-NM3P1 hydrogel of the present invention. Detailed implementation mode

[0038] The raw materials and equipment used in the embodiments of the present invention are all known products and can be obtained by purchasing commercially available products. As an example, the polydopamine nanoparticles (PDA NPs), polyzwitterionic poly(sulfobetaine methacrylate) (PSBMA), and polyzwitterionic microgels of the present invention are prepared by ourselves, and the methods are as follows:

[0039] Preparation of PDA NPs:

[0040] Polydopamine nanoparticles (PDA NPs) are synthesized by the self-polymerization reaction of dopamine in an alkaline environment. 100 mL of deionized water, 40 mL of ethanol, and 2 mL of ammonia water are mixed under magnetic stirring at room temperature, and then 0.5 g of dopamine hydrochloride is dissolved in the mixed solution and reacted for 24 h. The reaction solution is centrifuged and washed three times with deionized water. Finally, the reaction product PDA NPs are collected by freeze-drying. Observed by scanning electron microscopy, the particle size ranges from 400 nm to 600 nm.

[0041] Preparation of polyzwitterionic PSBMA and microgels:

[0042] 4 g of sulfobetaine methacrylate (SBMA) and 0.18 g of NaCl are dissolved in 30 mL of deionized water, and nitrogen is introduced into the mixed solution for 40 min. Then 40 mg of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AIBA) is added, and the reaction is carried out at 70 °C for 12 h under a nitrogen atmosphere. After the reaction is completed, the product is poured into a dialysis bag with a molecular weight cut-off of 3500, and the dialysis solution is changed 6 times in the middle, and each dialysis time is not less than 6 h. After dialysis, the product PSBMA is collected by freeze-drying.

[0043] Mix 26.43 g of liquid paraffin, 0.6 g of span, and 0.2 g of tween, and label it as mixed solution A. Dissolve 1 g of PSBMA and 0.025 g of APS in 8.17 g of 0.1 mol / L LiCl solution, and then add 2.5 g of acrylic acid (AAc) and mix, which is labeled as mixed solution B. Under the action of mechanical stirring, slowly add mixed solution B to mixed solution A, and introduce nitrogen into the mixed system for 20 min. After reacting at 60 °C for 4 h, centrifuge three times and wash with absolute ethanol. Finally, freeze-dry to collect the reaction product microgel. After observation by scanning electron microscopy, the particle size ranges from 10 nm to 100 nm. It should be noted that the inventors found in previous studies that microgels with better performance can be prepared when the dosage of PSBMA and AAc is in the range of 1:(0.5 - 5). However, under the ratio of microgel raw materials used in the examples of the present invention, the improvement of the adhesion performance of the prepared microgel particles to the hydrogel is relatively better. However, this preparation ratio is only an example and does not serve as a special limitation on the specific dosage of the microgel raw materials.

[0044] Example 1. Preparation of the Adhesive Monolayer Hydrogel of the Present Invention

[0045] Dissolve 0.266 g of N-isopropylacrylamide (NIPAM) in 2.334 g of 0.01 M PBS solution, and add 0.005 g of N,N'-methylenebisacrylamide (MBAA), 0.005 g of potassium persulfate (KPS), and a certain amount (the dosage is shown in Table 1) of PDANPs and microgel into the system. After dissolution, introduce nitrogen into the mixed solution for 5 min, and then add 2 - 10 μL of the catalyst tetramethylethylenediamine (TEMED). Place it at room temperature in the mold for 24 h to obtain the adhesive monolayer hydrogel. Each group of monolayer hydrogels is named NM1P0, NM3P0, NM5P0, NM7P0, NM3P 0.5 , NM3P1 and NM3P2.

[0046] Table 1:

[0047]

[0048] Example 2. Preparation of the Double-Layer Hydrogel of the Present Invention

[0049] Take the adhesive hydrogels NM3P0, NM3P 0.5 , NM3P1 and NM3P2. Dissolve 0.3 g of SBMA, 0.003 g of MBAA, and 0.003 g of photoinitiator (Irgacure 2959) in 1.7 g of 0.01 M PBS solution to obtain a mixed solution. Take the mixed solution and add it to the surface of the adhesive hydrogel, and initiate polymerization with ultraviolet light to prepare the double-layer hydrogels D-NM3P0, D-NM3P0.5 , D-NM3P1 and D-NM3P2.

[0050] Comparative Example 1, Preparation of Hydrogel NM0P0

[0051] Dissolve 0.266 g of N-isopropylacrylamide (NIPAM) in 2.334 g of 0.01 M PBS solution, and add 0.005 g of N,N'-methylenebisacrylamide (MBAA) and 0.005 g of potassium persulfate (KPS) to the system. After dissolution, pass nitrogen into the mixed solution for 5 min, and then add 2 - 10 μL of the catalyst tetramethylethylenediamine (TEMED). Let it stand at room temperature for 24 h to obtain the hydrogel NM0P0 of the pure PNIPAM matrix.

[0052] Comparative Example 2, Preparation of Hydrogel Containing Only PDA NPs

[0053] Refer to the preparation methods of NM3P 0.5 , NM3P1 and NM3P2, and only adjust the dosage of the microgel to 0 to prepare the hydrogel NM0P 0.5 , NM0P1 and NM0P2. Through the adhesion performance test, it is found that only doping with PDA NPs has no obvious effect of enhancing adhesion

[0054] The beneficial effects of the present invention are demonstrated by the following experimental examples. The characterization methods involved in the present invention are as follows:

[0055] 1. Structure and Morphology Analysis

[0056] Use FT-IR spectroscopy (Bruker Tensor-27 spectrometer) to characterize the chemical structure of the single-layer hydrogel, with the microgel and PDA NPs as control samples.

[0057] 2. Adhesion Performance

[0058] The adhesion of the single-layer hydrogel to different materials is evaluated by the lap shear experiment. Remove the fat layer on the fresh pig skin, wash the surface grease with dishwashing liquid, and cut it into strips of 100 mm (length) × 25 mm (width). Prepare aluminum sheets, plastics, cardboard, and glass of the same size. Sandwich the hydrogel of 25 mm (length) × 25 mm (width) × 1 mm (thickness) and the hydrogel of Comparative Example 1 between the above five substrates, and let it stand at room temperature for 5 minutes for the tensile test. At room temperature, use a universal testing machine (CMT-6104, MITS) for the tensile test, and the tensile rate is 10 mm / min. Each sample is tested three times.

[0059] 2. Photothermal Performance Evaluation

[0060] Prepare a single-layer hydrogel into a cylinder with a diameter of 1 cm and a height of 1 cm. Irradiate the hydrogel from a height of 20 cm with a near-infrared laser (NIR) with a wavelength of 808 nm, and select 0.50 W / cm 2 and 1.00 W / cm 2 for testing with two different powers. Use an infrared thermal imager (UTI120S) to record the surface temperature of the hydrogel at different irradiation times of the near-infrared light. Select a power of 1.00 W / cm 2 for the photothermal cycling test. When the surface temperature of the hydrogel reaches the peak under the action of the near-infrared light, turn off the laser emitter and let the hydrogel cool at room temperature. This cycle is repeated three times.

[0061] 3. Photothermal antibacterial performance

[0062] Use Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) for the photothermal antibacterial test of the single-layer hydrogel. Place the prepared hydrogel sample under ultraviolet light for sterilization treatment, and irradiate both the front and back sides of the hydrogel for 10 hours. Apply 100 μL of the bacterial suspension (10 7 CFU / mL) on the surface of the hydrogel. One group is irradiated with a near-infrared laser (808 nm, 1.00 W / cm 2 ) at a height of 20 cm from the sample for 5 minutes, and the other group is not irradiated with near-infrared light. Then add 900 μL of PBS solution to resuspend the bacteria surviving on the surface of the hydrogel, and dilute the bacterial suspension to 10 5 CFU / mL. Take 100 μL of the diluted bacterial suspension for plate counting. In addition, take 100 μL of the bacterial suspension (10 7 CFU / mL) and place it in a centrifuge tube, and perform the same operations as above as the negative control group.

[0063] 4. Bacterial surface adhesion

[0064] Add 10 μL of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) suspensions with a concentration of 10 7 CFU / mL to the double-layer hydrogel respectively, and incubate at 37 °C for 1 h. After incubation, gently wash the hydrogel five times with PBS solution to remove the loosely attached bacteria on the surface. Then, soak the double-layer hydrogel in 1 mL of PBS solution, ultrasonically vibrate for 1 h, and then dilute the solution to 10 5 CFU / mL. Take 100 μL of the diluted bacterial suspension for plate counting. Use the same diluted original bacterial suspension as the control group.

[0065] 5. Protein adsorption test

[0066] Using bovine serum albumin (BCA) as a model protein, the anti-fouling performance of the double-layer hydrogel was tested through protein adsorption experiments. 200 μL of bovine serum albumin solutions with concentrations of 250, 500, or 1000 μg / mL were added to the hydrogel samples respectively. After incubating at 37 °C for 30 minutes, 20 μL of the solution was taken out from each well, 200 μL of BCA working solution was added, and after waiting for 30 minutes, the absorbance of the solutions in the standard product wells and sample wells was measured with an enzyme-linked immunosorbent assay (ELISA) reader.

[0067] 6. Antioxidant Test

[0068] The antioxidant capacity of the materials was evaluated using a total antioxidant capacity detection kit. The double-layer hydrogel samples were immersed in ABTS solution and incubated at 37 °C for 30 minutes, and then the absorbance was measured at 735 nm with an ELISA reader.

[0069] 7. In vitro Hemolysis Test

[0070] Rat blood was centrifuged at 1500 rpm for 10 minutes, the supernatant was discarded, and the red blood cells were diluted tenfold with physiological saline to obtain a red blood cell suspension. In the experimental group, double-layer hydrogel, 100 μL of red blood cell suspension, and 900 μL of physiological saline were added. In the negative control group, 100 μL of red blood cell suspension and 900 μL of physiological saline were added. In the positive control group, 100 μL of red blood cell suspension and 900 μL of double-distilled water were added. After incubating at 37 °C for 1 hour, the materials were taken out, centrifuged at 2000 rpm for 10 minutes, the supernatant was taken into a 96-well plate, and the absorbance was measured at 540 nm with an ELISA reader.

[0071] 8. Cytotoxicity Test

[0072] The cytotoxicity of the double-layer hydrogel on L929 mouse fibroblasts was tested using a CCK-8 kit. The hydrogel was sterilized by soaking in 75% ethanol for 24 hours and irradiating with ultraviolet light for 1 hour. Then the sample was rinsed 5 times with PBS to remove the residual ethanol, and then the sample was placed in a 24-well plate, added with 1 mL of complete DMEM medium for soaking. The plate without the sample was used as a control group. The plate was placed in a constant temperature incubator for 72 hours to prepare the extract. At the same time, L929 cells were inoculated into a 96-well plate at a density of 5000 cells / well. After the cells grew for 24 hours, the old medium was discarded and replaced with 200 μL / well of the extract. L929 cells were cultured in the extract for 24 hours and 72 hours. After the incubation ended, the extract was replaced with 100 μL of DMEM medium containing 10% CCK-8 reagent, and after incubating at 37 °C for 1 hour, the absorbance was measured at 450 nm with an ELISA reader.

[0073] 9. Wound Healing Test

[0074] Male SD rats were anesthetized, and the hair on their backs was shaved off to establish a full-thickness skin defect model on the back. After the wounds were treated with D-NM3P1 hydrogel or PBS, half of them were irradiated with NIR laser, and the other half were not. The wound sites were photographed at days 0, 3, 7, and 14, and the wound closure rate was calculated. On day 14, after sampling, cytokine determination was performed.

[0075] Experimental Example 1. Results of the structural characterization of the hydrogel of the present invention

[0076] As Figure 1 shown, in the FTIR spectrum, there is an obvious absorption peak at 3434 cm -1 , corresponding to the stretching vibration of -O-H, and the absorption peak at 3311 cm -1 corresponds to the stretching vibration of -N-H. The absorption peak at 2965 cm -1 indicates the presence of -C-H stretching vibration, and the absorption peak at 1172 cm -1 corresponds to the stretching vibration of the C-O bond, and the absorption peak at 1643 cm -1 corresponds to the stretching vibration of C=O, proving the successful synthesis of the hydrogel of the present invention.

[0077] Experimental Example 2. Test results of the adhesion performance of the hydrogel of the present invention

[0078] The test results of selecting five substrates such as pigskin, plastic, glass, aluminum sheet, and cardboard are as Figure 2 shown. The pure PNIPAM hydrogel NM0P0 of Comparative Example 1 hardly showed adhesion; while in the hydrogels without adding PDA NPs, with the increase in the addition amount of microgels, the adhesion ability of the hydrogels showed a trend of first increasing and then decreasing, and NM3P0 showed the best adhesion ( Figure 2 a in). After adding PDA NPs, a large number of catechol groups in PDA NPs further improved the mechanical strength and adhesion strength of the NMP hydrogel. Therefore, with the increase in the content of PDA NPs, the adhesion strength of the hydrogel increased in turn ( Figure 2 b in).

[0079] Experimental Example 3. Test results of the photothermal performance of the hydrogel of the present invention

[0080] After irradiating the hydrogel with NIR laser, the temperatures of NM3P 0.5 , NM3P1, and NM3P2 increased rapidly, and at the same time, the temperature of NM3P0 also increased under long-term NIR laser irradiation. Under NIR laser irradiation, the rate of increase in the temperature of the hydrogel increased with the increase in the content of PDANPs. In addition, by changing the power density of the NIR laser, the photothermal conversion rate of the hydrogel can be adjusted. When the power density was changed from 0.5 W / cm2 ( Figure 3 in a), it is increased to 1 W / cm 2 ( Figure 3 in b), the stable temperature of NM3P1 rises from 42 °C to 68 °C. Thus, it can be seen that the photothermal performance of the hydrogel of the present invention can be adjusted, and the stable temperatures of NM3P 0.5 , NM3P1 under higher density NIR laser irradiation are more suitable for skin contact. Considering the mechanical properties, adhesion properties and photothermal density test results comprehensively, NM3P1 is the sample with the best performance. Further evaluating its photothermal stability through laser on-off cycles, it is found that after three laser on-off cycles, the stable temperature of NM3P1 is relatively stable ( Figure 3 in c), which proves that the hydrogel of the present invention has good photothermal stability and can be used for photothermal antibacterial.

[0081] Experimental Example 4. Test results of the photothermal antibacterial performance of the hydrogel of the present invention

[0082] Using Escherichia coli and Staphylococcus aureus as models for photothermal antibacterial testing, the results are as Figure 4 shown. Without NIR laser irradiation, the control group and the experimental group hardly have bactericidal ability. After NIR laser irradiation, the control group and NM3P0 hardly show bactericidal ability because they cannot perform photothermal conversion. However, the hydrogel added with PDA NPs rapidly heats up under the irradiation of NIR laser and shows good bactericidal ability. The bactericidal rate of NM3P1 against Escherichia coli is 99.96%, and the bactericidal rate against Staphylococcus aureus is 99.97%.

[0083] Experimental Example 5. Test results of the anti-adsorption of the double-layer hydrogel of the present invention

[0084] Using Escherichia coli and Staphylococcus aureus as models, the ability of the double-layer hydrogel to prevent bacterial adsorption is tested, and the results are as Figure 5 shown. The removal rates of the double-layer hydrogel of the present invention against Escherichia coli and Staphylococcus aureus both exceed 99%.

[0085] Using BCA protein as a model, the ability of the double-layer hydrogel to prevent protein adsorption is tested. The results are as Figure 6 shown. When the protein concentration is low (250 μg / mL), the protein removal rates of the double-layer hydrogel of the present invention are all above 99%; for a 500 μg / mL protein solution, the removal rates are all above 98%; when the protein concentration is high (1000 μg / mL), the removal rate can also reach 95%.

[0086] Experimental Example 6. Test results of the antioxidant performance of the double-layer hydrogel of the present invention

[0087] The antioxidant ability of the D-NMP hydrogel is measured by the ABTS method, and the results are asFigure 7 As shown, D-NM3P0 without doped PDA NPs has little ability to scavenge reactive oxygen species, while D-NM3P 0.5 , D-NM3P1 and D-NM3P2 all have a scavenging ability of about 50% for ROS.

[0088] Experimental Example 7. Test results of blood compatibility of the double-layer hydrogel of the present invention

[0089] The results of evaluating the blood compatibility of the hydrogel of the present invention through hemolysis experiments are as Figure 8 shown. The hemolysis rates of D-NM3P0, D-NM3P 0.5 , D-NM3P1 and D-NM3P2 are 2.39%, 1.22%, 1.75% and 3.54% respectively, all below 5%, showing good blood compatibility.

[0090] Experimental Example 7. Test results of treating wounds with the double-layer hydrogel of the present invention

[0091] The results are as Figure 9 shown. The D-NM3P1 hydrogel combined with NIR was used to treat the wound. The wound closure rate on the third day was significantly higher than that of other control groups and experimental groups. On the fourteenth day, the healing rate of the D-NM3P1+NIR group was the highest and the wound had completely closed.

[0092] For further characterization of wound inflammation, the results are as Figure 10 shown. Inflammatory factors such as TNF-α and IL-6 in the wound tissue of the D-NM3P1+NIR group decreased, and the expression of IL-4 increased, indicating that the wound healing effect of the D-NM3P1+NIR group was better. The D-NM3P1+NIR group also expressed more integrin β1 (ITGb1). Integrin β1 is part of the cell surface receptor and participates in the interaction between cells and the extracellular matrix (ECM). During wound healing and tissue reconstruction, integrin β1 is crucial for cell adhesion, migration and extracellular matrix remodeling. During the experiment, the D-NM3P1 hydrogel was irradiated with NIR to heat and contract it, thereby driving tissue closure. During this process, the hydrogel provided a tensile force in the direction of wound healing, and the force signal would activate the mechanosensitive signaling pathway in cells (such as focal adhesion kinase, FAK, or Rho family GTPases, etc.), and then up-regulate the expression of integrin β1. The increase in integrin β1 helps to enhance the adhesion ability between cells and the matrix, promote the migration of fibroblasts, epithelial cells, etc., and thus promote tissue repair and healing.

[0093] In summary, the adhesive hydrogel prepared by the present invention has excellent adhesion, antibacterial property and mechanical properties, has the ability to pull wound closure and promote wound healing, and has good biocompatibility; the double-layer hydrogel prepared based on the adhesive hydrogel can also achieve the effects of anti-fouling on the upper layer and adhesion on the lower layer, and has great application potential in the field of wound dressings.

Claims

1. An adhesive hydrogel, characterized in that, It is made from the following raw materials in parts by weight: 2.71 parts of a thermosensitive hydrogel skeleton, 0.3 part of polyzwitterionic microgel, and 0.005 - 0.02 part of polydopamine; The thermosensitive hydrogel skeleton is composed of a thermosensitive polymer. The specific preparation method of the adhesive hydrogel is to dissolve a thermosensitive polymer monomer, a crosslinking agent, a polyzwitterionic microgel, polydopamine, and an initiator in an aqueous solvent to form a mixed solution for reaction; the thermosensitive polymer monomer is N - isopropylacrylamide, and the crosslinking agent is N,N’ - methylenebisacrylamide; the weight ratio of the thermosensitive polymer monomer to the crosslinking agent is (50 - 60):1; the polyzwitterionic microgel is a polymer prepared by polymerizing polyzwitterion and acrylic acid under the action of an initiator; the polyzwitterion is poly(sulfobetaine methacrylate); the mass ratio of the polyzwitterion to acrylic acid is 1:(0.5 - 5), and the polyzwitterionic microgel is particles with a particle size of 10 nm - 100 nm; the polydopamine is particles with a particle size of 400 nm - 600 nm.

2. The preparation method of the adhesive hydrogel according to claim 1, characterized in that, It includes the following steps: (1) Dissolve a thermosensitive polymer monomer, a crosslinking agent, a polyzwitterionic microgel, polydopamine, and an initiator in an aqueous solvent to form a mixed solution; (2) Add a catalyst to the mixed solution under an inert gas condition, mix well, and let it stand at room temperature for 20 - 30 hours.

3. The preparation method according to claim 2, characterized in that, The aqueous solvent is a PBS solution, the initiator is potassium persulfate, and the catalyst is N,N,N',N' - tetramethylethylenediamine; the dosage ratio of the thermosensitive polymer monomer, the aqueous solvent, the initiator, and the catalyst is: (0.2 - 0.3) g:(2 - 2.5) g:(0.003 - 0.008) g:(2 - 10) μL.

4. A double-layer hydrogel, characterized in that, The lower layer is the hydrogel described in claim 1, and the upper layer is a polyzwitterionic hydrogel; the polyzwitterionic hydrogel is made from a zwitterionic monomer and a crosslinking agent.

5. Use of the adhesive hydrogel described in claim 1, or the double - layer hydrogel described in claim 4 for preparing a wound dressing.

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