Multifunctional hydrogel capable of switching mechanical and adhesive properties based on temperature triggering and preparation method and application thereof

Abstract

The invention belongs to the crossing field of biomedical engineering, material science and tissue engineering, and discloses multifunctional hydrogel capable of switching mechanical and adhesive properties based on temperature triggering as well as a preparation method and application of the multifunctional hydrogel. The water-based adhesive is prepared from acrylic acid, gelatin, hexadecyl trimethyl ammonium bromide, silver nanoparticle-loaded polydopamine nanoparticles and water. According to the present invention, the good adhesion property and the good mechanical property are provided for the skin tissue, the mechanical property and the adhesion property can be switched, and the adhesion property durability and the adhesion property repeatability are achieved. The temperature-triggered hydrogel prepared by the method has the advantages of simple process, low cost and no introduction of toxic chemical substances, can achieve the effects of tight fitting at body temperature and natural falling at low temperature according to the driving of temperature, still has excellent adhesion performance in a complex environment, and promotes the development of intelligent medical multifunctional wound dressings.

Description

Technical Field

[0001] The present invention belongs to the cross - field of biomedical engineering, materials science and tissue engineering, and particularly relates to a multifunctional hydrogel with temperature - triggered switchable mechanical and adhesive properties, a preparation method thereof and an application thereof. Background Art

[0002] Intelligent hydrogel materials, with their diverse functionality, excellent softness, outstanding stretchability, and good biocompatibility, have great application potential in cross - fields such as biomedical engineering, materials science and tissue engineering, and have become a research hotspot in the application scenario of wound dressings. With the development of modern medicine, tissue engineering, materials science and biomedicine have put forward more stringent requirements for the performance and function of biomaterials, and the research and exploration of intelligent hydrogels have received more and more attention.

[0003] Temperature - responsive hydrogels play a crucial role in the application scenario of wound dressings, and can achieve the effects of strong adhesion at high temperature and easy desorption at low temperature with the change of environmental temperature. Traditional dressings are difficult to maintain wound moisture, easily adhere to granulation tissue and hinder healing. Moreover, there are problems such as insufficient adhesion effect and easy shedding, or too strong adhesion ability resulting in secondary injury to the wound during peeling. Temperature - responsive hydrogel dressings can sense the temperature changes of the wound and the environment, maintain moisture and avoid adhesion, adhere firmly and desorb as needed, accelerate wound healing, and protect the wound from secondary trauma. Although there have been achievements in the research of temperature - responsive hydrogels, there are still challenges in practical applications and performance regulation. The performance of the materials is still not significantly affected by temperature changes, and the mechanical strength, adhesive properties and durability need to be improved urgently. These problems have greatly limited the wide application of temperature - responsive hydrogels. Therefore, developing a hydrogel patch with high - efficiency temperature drive, close fitting at body temperature, natural shedding at low temperature, breakthroughs in mechanical and adhesive properties, and significantly improved use persistence and repeatability has great application potential in the field of intelligent medical multifunctional wound dressings. This temperature - driven intelligent medical multifunctional wound dressing can provide higher - quality materials for the biomedical field and is of great significance for promoting the development of tissue engineering and biomedicine. Summary of the Invention

[0004] To overcome the disadvantages and deficiencies existing in the above-mentioned prior art, the primary object of the present invention is to provide a preparation method of a multifunctional hydrogel with temperature-triggerable switchable mechanical and adhesive properties; this method constructs a Gelatin / PAA / PDA@Ag / CTAB hydrogel, in which acrylic acid (AA) and gelatin can effectively improve the biocompatibility and tissue adhesiveness of the hydrogel; moreover, gelatin endows the hydrogel with temperature-sensitive characteristics, forming a stable three-dimensional network structure in a low-temperature environment, and the functional groups interact with each other, thereby causing an increase in the modulus of the hydrogel and a decrease in the adhesion effect; when in a high-temperature environment, the movement of the molecular chains becomes more intense, the network structure tends to be loose, and the functional groups are fully exposed, effectively acting with the active sites on the adhesion surface, thus reducing the modulus of the hydrogel and improving the adhesion effect; in addition, positively charged cetyltrimethylammonium bromide (CTAB) forms a hydrophobic binding region in the hydrogel network through strong electrostatic interaction with the PAA chain segment and the stabilization of the hydrophobic fragment of the polydopamine nanoparticles loaded with silver nanoparticles (PDA@Ag). These dual effects make the polymer chains cross-linked more uniformly and stably, thereby enhancing the mechanical properties of the hydrogel. At the same time, CTAB improves the wettability by reducing the surface tension and endows the hydrogel surface with positive electricity, synergistically enhancing the adhesion performance of the hydrogel in multiple dimensions; therefore, this temperature-driven hydrogel not only has good adhesion and mechanical properties, but also can achieve strong adhesion at body temperature and easy desorption at low temperature through temperature triggering, realizing the temperature-driven high-efficiency intelligent adhesion function.

[0005] Another object of the present invention is to provide a multifunctional hydrogel with temperature-triggerable switchable mechanical and adhesive properties prepared by the above preparation method.

[0006] Another object of the present invention is to provide an application of a multifunctional hydrogel with temperature-triggerable switchable mechanical and adhesive properties.

[0007] The object of the present invention is achieved by the following technical solutions: A preparation method of a multifunctional hydrogel with temperature-triggerable switchable mechanical and adhesive properties, comprising the following operating steps: Using a one-pot mixing method, adding the freeze-dried powder of polydopamine nanoparticles loaded with silver nanoparticles, polymer monomers, cross-linking agents, initiators, and surfactants to a 15.50 wt% gelatin solution, mixing evenly to obtain a prepolymer solution; filling the prepolymer solution into a mold, and heating to induce polymerization to obtain a multifunctional hydrogel with temperature-triggerable switchable mechanical and adhesive properties (Gelatin / PAA / PDA@Ag / CTAB hydrogel); The dosage of the freeze-dried poly-dopamine nanoparticles loaded with silver nanoparticles is 0.10 wt% of the prepolymerization solution, the dosage of the polymer monomer is 24.50 wt% of the prepolymerization solution, the dosage of the crosslinking agent is 0.055 wt% of the prepolymerization solution, the dosage of the initiator is 0.60 wt% of the prepolymerization solution, and the dosage of the surfactant is 7.00 wt% of the prepolymerization solution; The polymer monomer is one of acrylic acid and methacrylic acid; the surfactant is cetyltrimethylammonium bromide.

[0008] The freeze-dried poly-dopamine nanoparticles loaded with silver nanoparticles are prepared by the following method: (1) By the solution oxidation method, dopamine hydrochloride, ammonium persulfate, absolute ethanol and pure water are formulated into a dopamine hydrochloride ethanol / water mixed solution, and the pH value of the dopamine hydrochloride ethanol / water mixed solution is adjusted with an alkali solution, and stirred and reacted. Dopamine hydrochloride is oxidized and self-polymerized to form poly-dopamine nanoparticles, which are centrifugally washed with a detergent and freeze-dried to obtain poly-dopamine (PDA) freeze-dried powder; (2) By the reduction deposition method, the pH value of the silver salt aqueous solution is adjusted to alkaline with an alkali solution, and then the poly-dopamine freeze-dried powder obtained in step (1) is added to the silver salt aqueous solution; at a temperature of 15 - 30 °C, stirring reaction is carried out at a speed of 500 - 700 rpm for 1 - 2 h, and silver nanoparticles are in-situ reduced on the surface of the poly-dopamine nanoparticles to generate silver nanoparticles, which are centrifugally washed with a detergent and freeze-dried to obtain the freeze-dried powder of poly-dopamine nanoparticles loaded with silver nanoparticles (PDA@Ag); In step (1), the pH value is adjusted to 10 - 11; the temperature of the stirring reaction is 15 - 30 °C, the time of the stirring reaction is 12 - 36 h, and the stirring speed is 500 - 700 rpm; the alkali solution is ammonia water, sodium hydroxide solution, potassium hydroxide solution or sodium bicarbonate solution; the detergent is pure water and absolute ethanol.

[0009] In step (1), the molar ratio of dopamine hydrochloride to ammonium persulfate is 2:1; the volume ratio of absolute ethanol to pure water is 2:7.

[0010] In step (2), the silver salt is silver nitrate.

[0011] In step (2), the mass ratio of the silver salt to the poly-dopamine freeze-dried powder is 2:3.

[0012] The gelatin solution is prepared by adding gelatin to pure water and stirring and dissolving it in a water bath at 60 - 80 °C to obtain a gelatin solution with a concentration of 15.50 wt%.

[0013] The crosslinking agent is one of N,N'-methylenebisacrylamide, bisacrylamide, polyethylene glycol diacrylate, and polyethylene glycol dimethacrylate; the initiator is potassium persulfate or ammonium persulfate.

[0014] The heat-induced polymerization is carried out by heating at 75 - 85 °C for 30 - 120 min.

[0015] The mold is a square polytetrafluoroethylene or silicone mold; filling the prepolymer solution into the mold is to control the thickness of the finally obtained multifunctional hydrogel by controlling the addition amount of the prepolymer solution.

[0016] A multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties prepared by the above preparation method. The multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties has stretchability and compressibility, and has stable and durable adhesive ability both on water and underwater. Driven by body temperature (37 °C), it shows low modulus, easy deformation (tensile modulus 0.3 kPa, compressive modulus 0.3 kPa), high extensibility (elongation at break 964.5%), and strong adhesive property (adhesive strength 17.8 kPa). Driven by low temperature (4 °C), it shows high modulus (tensile modulus 0.7 kPa, compressive modulus 1.5 kPa), anti-deformation (compressive stress at 80% compressive deformation rate 728.6 kPa), and easy desorption property (adhesive strength 6.7 kPa). It can be used as a temperature-driven intelligent medical multifunctional wound dressing to realize high-adaptability wound treatment applications with close fitting at body temperature and natural shedding at low temperature.

[0017] The application of the above-mentioned multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties in preparing patches with switchable mechanical and adhesive properties.

[0018] The above-mentioned multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties is applied to prepare a temperature-driven intelligent medical multifunctional wound dressing that can closely fit at body temperature and naturally shed at low temperature.

[0019] The present invention has the following advantages and beneficial effects compared with the prior art: (1) The multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties of the present invention has temperature-triggered switchable adhesive properties.

[0020] (2) The multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties of the present invention has temperature-triggered switchable mechanical properties, namely stretchability, compressibility, etc.

[0021] (3)The multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties prepared by the present invention can be applied to the fields of intelligent wound dressing and tissue repair; its temperature-triggered switchable adhesive property can be used as an intelligent wound dressing for on-demand application or a gentle tissue repair that does not cause secondary damage during replacement; in addition, its temperature-triggered switchable mechanical property can meet the requirements for the shape and deformation of the patch during the treatment process, so as to achieve a tight fit between the gel and the complex wound environment, as well as a high degree of wound adaptation to the environmental changes during the wound repair process, thereby achieving an efficient treatment effect. Description of the Drawings

[0022] Figure 1 FTIR spectra of AA, PDA@Ag, and CTAB.

[0023] Figure 2 FTIR spectra of Gelatin and Gelatin / PAA / PDA@Ag / CTAB hydrogels.

[0024] Figure 3 For Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel, Gelatin 3 / PAA 7 / PDA@Ag / DTAB hydrogel, and Gelatin 3 / PAA 7 / PDA@Ag / HTAB hydrogel's adhesion strength to the steel plate.

[0025] Figure 4 Adhesion strength of four different formulation ratios of Gelatin / PAA / PDA@Ag / CTAB hydrogels to porcine skin at 4 °C and 37 °C.

[0026] Figure 5 Temperature-modulus curves of four different formulation ratios of Gelatin / PAA / PDA@Ag / CTAB hydrogels.

[0027] Figure 6 For Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel's tensile stress-strain strength curves at 4 °C and 37 °C.

[0028] Figure 7 For Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel's tensile modulus and toughness at 4 °C and 37 °C.

[0029] Figure 8 It is Gelatin 3 / PAA 7 Compressive stress-strain strength curves of the Gelatin / PAA / PDA@Ag / CTAB hydrogel at 4 °C and 37 °C.

[0030] Figure 9 It is Gelatin 3 / PAA 7 Compressive modulus and toughness of the Gelatin / PAA / PDA@Ag / CTAB hydrogel at 4 °C and 37 °C. Specific implementation manners

[0031] The content of the present invention will be further described below in conjunction with specific embodiments, but should not be construed as a limitation to the present invention.

[0032] The preparation process of the multifunctional hydrogel with temperature-triggerable switchable mechanical and adhesive properties in the following examples is carried out according to the following operating steps: Step 1: By the solution oxidation method, dopamine hydrochloride, ammonium persulfate, absolute ethanol and pure water are formulated into a dopamine hydrochloride ethanol / water mixed solution, and the pH of the dopamine hydrochloride ethanol / water mixed solution is adjusted to 10-11 with an alkali solution, and stirred at a stirring speed of 500-700 rpm at 15-30 °C for 12-36 h, and then centrifugally washed with pure water and absolute ethanol and freeze-dried to obtain polydopamine (PDA) lyophilized powder; Step 2: Adopt the reduction deposition method, and adjust the pH value of the silver salt (0.22 mmol / L) aqueous solution to 10-11 with an alkali solution. Then, add the polydopamine lyophilized powder obtained in Step 1 to the above silver salt aqueous solution; at a temperature of 15-30 °C, stir and react at a rotation speed of 500-700 rpm for 1-2 h, and in-situ reduce the silver salt on the surface of the polydopamine nanoparticles to generate silver nanoparticles, and then centrifugally wash with pure water and absolute ethanol and freeze-dry to obtain polydopamine nanoparticles loaded with silver nanoparticles (PDA@Ag) lyophilized powder; Step 3: Add gelatin to pure water and stir to dissolve it in a water bath at 60-80 °C to obtain a gelatin solution with a concentration of 15.50 wt%; Step 4: Using a one-pot mixing method, add the freeze-dried powder of poly(dopamine) nanoparticles loaded with silver nanoparticles (PDA@Ag) obtained in Step 2, polymer monomers, crosslinking agents, initiators, and surfactants to the gelatin solution obtained in Step 3, and mix evenly to obtain a prepolymer solution; fill the prepolymer solution into a polytetrafluoroethylene or silicone mold, control the thickness of the final obtained hydrogel patch by controlling the addition amount of the prepolymer solution, and induce polymerization by heating to obtain a multifunctional hydrogel with temperature-triggered switchable mechanical and adhesion properties; the dosage of the freeze-dried powder of poly(dopamine) nanoparticles loaded with silver nanoparticles is 0.10 wt% of the prepolymer solution, the dosage of the polymer monomer is 24.50 wt% of the prepolymer solution, the dosage of the crosslinking agent is 0.055 wt% of the prepolymer solution, the dosage of the initiator is 0.60 wt% of the prepolymer solution, and the dosage of the surfactant is 7.00 wt% of the prepolymer solution; the polymer monomer is one of acrylic acid and methacrylic acid; the surfactant is cetyltrimethylammonium bromide.

[0033] The multifunctional hydrogel with temperature-triggered switchable mechanical and adhesion properties prepared in the present invention can be applied to the fields of intelligent wound dressing and tissue repair. Its temperature-triggered switchable adhesion property can be used as an intelligent wound dressing for on-demand application or a gentle tissue repair that does not cause secondary damage during replacement; in addition, its temperature-triggered switchable mechanical property can meet the requirements for the shape and deformation of the patch during the treatment process, so as to achieve a tight fit between the hydrogel and the complex wound environment, and a high wound adaptability to environmental changes during the wound repair process, thereby achieving an efficient treatment effect. It provides a new idea for the development of intelligent wound dressing and tissue repair.

[0034] Example 1

[0035] This example provides a preparation method for four Gelatin / PAA / PDA@Ag / CTAB hydrogels with different formulation ratios, including the following steps specifically: Step 1: Mix 225 mg of dopamine hydrochloride, 139.5 mg of ammonium persulfate, 10 mL of absolute ethanol, and 35 mL of pure water evenly, adjust the pH to 10 by adding ammonia water, stir at a stirring speed of 600 rpm at 25 °C for 24 h, and after centrifugal washing with pure water and absolute ethanol and freeze-drying, obtain the freeze-dried powder of poly(dopamine) (PDA).

[0036] Step 2: Using the reduction deposition method, adjust the pH value of an aqueous silver nitrate (0.22 mmol / L) solution to 10 - 11 with ammonia water. Then, add the poly-dopamine freeze-dried powder (147 mg) obtained in Step 1 to the above aqueous silver nitrate solution; stir at a speed of 500 rpm at 25 °C for 1 h, in-situ reduce the silver salt on the surface of the poly-dopamine nanoparticles to generate silver nanoparticles, and after centrifugal washing with pure water and absolute ethanol and freeze-drying, obtain the poly-dopamine nanoparticles loaded with silver nanoparticles (PDA@Ag) freeze-dried powder.

[0037] Step 3: Add gelatin (2.10 g) to pure water (11.45 mL), stir and dissolve it in a water bath at 70 °C to obtain a gelatin solution with a concentration of 15.50 wt%. Step 4: Using the one-pot mixing method, add the poly-dopamine nanoparticles loaded with silver nanoparticles (PDA@Ag) freeze-dried powder (0.02 g), acrylic acid (4.90 g), N,N'-methylenebisacrylamide (0.01 g), ammonium persulfate (0.12 g), and cetyltrimethylammonium bromide (1.40 g) obtained in Step 2 to the gelatin solution obtained in Step 3, and mix evenly to obtain a Gelatin:PAA:CTAB mass ratio of 3:7:2 Gelatin 3 / PAA 7 / PDA@Ag / CTAB prepolymer solution. Fill the prepolymer solution into a polytetrafluoroethylene mold, control the thickness of the final obtained hydrogel patch by controlling the addition amount of the prepolymer solution, and heat at 80 °C for 40 min to obtain a hydrogel, denoted as Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel.

[0038] Modify the cetyltrimethylammonium bromide (CTAB) in the above prepolymer solution to an equimolar amount of dodecyltrimethylammonium bromide (DTAB) (1.18 g) to obtain a Gelatin with dodecyltrimethylammonium bromide (DTAB) as the surfactant 3 / PAA 7 / PDA@Ag / DTAB prepolymer solution. The finally obtained hydrogel is denoted as Gelatin 3 / PAA 7 / PDA@Ag / DTAB hydrogel.

[0039] Modify the cetyltrimethylammonium bromide (CTAB) in the above prepolymer solution to an equimolar amount of hexyltrimethylammonium bromide (HTAB) (0.86 g) to obtain a Gelatin with hexyltrimethylammonium bromide (HTAB) as the surfactant 3 / PAA 7 / PDA@Ag / HTAB prepolymer solution. The finally obtained hydrogel is denoted as Gelatin 3 / PAA 7 / PDA@Ag / HTAB hydrogel.

[0040] The addition amounts of gelatin and acrylic acid in the above prepolymer solution were respectively modified to 0.70 g and 6.30 g, and Gelatin with a mass ratio of Gelatin:PAA:CTAB of 1:9:2 was obtained 1 / PAA 9 / PDA@Ag / CTAB prepolymer solution. The finally obtained hydrogel is denoted as Gelatin 1 / PAA 9 / PDA@Ag / CTAB hydrogel.

[0041] The addition amounts of gelatin and acrylic acid in the above prepolymer solution were respectively modified to 1.40 g and 5.60 g, and Gelatin with a mass ratio of Gelatin:PAA:CTAB of 2:8:2 was obtained 2 / PAA 8 / PDA@Ag / CTAB prepolymer solution. The finally obtained hydrogel is denoted as Gelatin 2 / PAA 8 / PDA@Ag / CTAB hydrogel.

[0042] The addition amounts of gelatin and acrylic acid in the above prepolymer solution were respectively modified to 2.80 g and 4.20 g, and Gelatin with a mass ratio of Gelatin:PAA:CTAB of 4:6:2 was obtained 4 / PAA 6 / PDA@Ag / CTAB prepolymer solution. The finally obtained hydrogel is denoted as Gelatin 4 / PAA 6 / PDA@Ag / CTAB hydrogel.

[0043] For the above obtained Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel was subjected to infrared spectroscopy analysis, and the experimental results are as follows: As Figure 1 、 Figure 2 shown, from the spectral data of cetyltrimethylammonium bromide (CTAB), a stretching vibration peak of -CH -1 appeared at 2929 cm 3 The stretching vibration of bromide ions appears at 723 cm -1 . For PDA@Ag, the broad peak at 3000 - 3500 cm -1 is attributed to the combined peak of O-H and N-H, and 1284 cm-1 The peak is the stretching vibration peak of phenolic C-O. In addition, 1590 cm -1 is the stretching vibration peak of aromatic C=C in the aromatic group. 829 cm -1 The peak is the out-of-plane vibration peak of C-H in the aromatic hydrocarbon. For acrylic acid (AA), a combined stretching vibration peak of O-H and C-H appears around 2700 - 3400 cm -1 A peak appears around 1634 cm -1 and 1697 cm -1 are attributed to C=C and C=O vibrations respectively. For gelatin, peaks appear at 3286 cm -1 and 2944 cm -1 are attributed to N-H and C-H vibrations respectively. 1634 cm -1 is the stretching vibration peak of C=O. For the Gelatin / PAA / PDA@Ag / CTAB hydrogel, wide and narrow peaks of O-H and N-H appear around 3000 - 3500 cm -1 A stretching vibration attributed to C-H appears at 2919 cm -1 , and a peak appears at 1646 cm -1 attributed to C=O vibration. The peak at 1200 cm -1 is the stretching vibration peak of phenolic C-O. The double bond peak at 1634 cm -1 attributed to C=C disappears, proving that C=C undergoes polymerization.

[0044] Example 2

[0045] This example provides a method for evaluating the lap shear adhesion performance of hydrogels with three different surfactants on steel plates, including the following steps specifically: Step 1: Fill the prepolymer solutions of the three different surfactants obtained in Example 1 above into silicone molds with a length of (40 mm) × width of (20 mm) × height of (2 mm), and heat at 80 °C for 40 min to obtain hydrogels with three different surfactants.

[0046] Step 2: Use a steel plate as the adhesion substrate material to evaluate their adhesion performance. Sandwich the hydrogel between two identical substrate materials. Then, apply a pressure of 1 kg weight to the overlapping area of the substrate material and the hydrogel for 30 s.

[0047] Step 3: Clamp the substrate materials at both ends through the tensile fixture of a universal testing machine, and use the lap shear method to test the adhesion performance. Among them, the tensile rate is 15 mm / min.

[0048] Experimental results: As Figure 3 shown, Gelatin3 / PAA 7 / PDA@Ag / CTAB hydrogel, Gelatin 3 / PAA 7 / PDA@Ag / DTAB hydrogel and Gelatin 3 / PAA 7 The adhesion strengths of the / PDA@Ag / HTAB hydrogels are 46.5 kPa, 26.1 kPa, and 6.4 kPa, respectively. This indicates that compared with hydrogels with other surfactants, the Gelatin with CTAB as the surfactant is 3 / PAA 7 / PDA@Ag / CTAB hydrogel has better adhesion ability.

[0049] Example 3

[0050] This embodiment provides a method for evaluating the lap shear adhesion performance of four hydrogels with different formulation ratios to pigskin at 4° C. and 37° C., respectively, comprising the following steps: Step 1: The four prepolymer solutions (Gelatin 3 / PAA 7 / PDA@Ag / CTAB, Gelatin 1 / PAA 9 / PDA@Ag / CTAB, Gelatin 2 / PAA 8 / PDA@Ag / CTAB, Gelatin 4 / PAA 6 / PDA@Ag / CTAB) were filled into silicone molds of length (40 mm) × width (20 mm) × height (2 mm), and heated at 80°C for 40 min to obtain four hydrogels with different formula ratios.

[0051] Step 2: The hydrogel obtained in step 1 was placed at 4°C and 37°C for 30 minutes respectively.

[0052] Step 3: Use pigskin as the adhesion substrate to evaluate the adhesion performance of the two. The 4°C or 37°C hydrogel after constant temperature treatment was sandwiched between two identical substrates. Then, a 1 kg weight was used to press the overlapping area of ​​the substrate and the hydrogel for 30 s.

[0053] Step 4: Clamp the base material at both ends with the tensile fixture of the universal testing machine and test the adhesion performance using the lap shear method, where the tensile rate is 15 mm / min.

[0054] Experimental results: Figure 4Compared with the hydrogels with other formulation ratios, Gelatin with a mass ratio of Gelatin:PAA:CTAB of 3:7:2 3 / PAA 7 / PDA@Ag / CTAB hydrogel exhibits higher adhesion strength at 37 °C and lower adhesion strength at 4 °C, indicating that among the hydrogels with different formulation ratios, Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel has the best temperature-triggered switchable adhesion performance.

[0055] For Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel, the adhesion strength to porcine skin at 37 °C (17.8 kPa) is much greater than that at 4 °C (6.7 kPa), indicating that Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel has the ability to closely adhere to the surface to be bonded at body temperature and can naturally fall off after cooling treatment.

[0056] Example 4

[0057] This example provides a method for evaluating the change and trend of viscoelastic properties of four hydrogels with different formulation ratios at different temperatures, including the following specific steps: Step 1: Fill the four different formulation ratio prepolymers obtained in Example 1 above (Gelatin 3 / PAA 7 / PDA@Ag / CTAB, Gelatin 1 / PAA 9 / PDA@Ag / CTAB, Gelatin 2 / PAA 8 / PDA@Ag / CTAB, Gelatin 4 / PAA 6 / PDA@Ag / CTAB) into cylindrical silicone molds with a diameter of (25 mm) × height of (2 mm) respectively, and heat at 80 °C for 40 min to obtain four hydrogels with different formulation ratios.

[0058] Step 2: Clean and dry the rheometer test platform in advance, evenly spread the sample on the test platform, and complete the installation of the sample.

[0059] Step 3: Set the temperature scanning range of the rheometer to be from 5 °C to 50 °C and the oscillation frequency to be 1 Hz. Among them, data is recorded every 1.5 min.

[0060] Experimental results: As Figure 5 shown, compared with Gelatin 1 / PAA 9 / PDA@Ag / CTAB hydrogel and Gelatin 2 / PAA 8 / PDA@Ag / CTAB hydrogel, Gelatin with a higher gelatin content 3 / PAA 7 / PDA@Ag / CTAB hydrogel and Gelatin 4 / PAA 6 / PDA@Ag / CTAB hydrogel has a stronger response to temperature. At around 35°C, there are obvious turning points in both the storage modulus and the loss modulus, and it can better achieve the effect of driving the mechanical property switching through the switching between body temperature conditions and low temperature conditions. Compared with Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel, for Gelatin 4 / PAA 6 / PDA@Ag / CTAB hydrogel, both the storage modulus and the loss modulus are generally poor, which means that Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel can withstand greater stress, has better energy absorption ability, and has higher durability and reusability when used as a wound dressing, and can better adapt to the challenges brought by complex environments.

[0061] For Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel with a mass ratio of Gelatin:PAA:CTAB of 3:7:2, as the temperature increases, the storage modulus of Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel gradually decreases, and the lowest point is at 32.5°C, while the loss modulus gradually increases, and the highest point is at 40°C, indicating that at 37°C, Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel will have good deformation ability and can better maintain a specific shape. At 4°C, Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel will have better anti-deformation ability. This means that Gelatin 3 / PAA 7The / PDA@Ag / CTAB hydrogel can achieve the ideal effect of changing its shape at body temperature, closely fitting the wound environment, maintaining its shape unchanged at low temperature, and resisting deformation. And at body temperature, in the face of a wound environment with a complex shape, Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel can also achieve the effect of close fitting.

[0062] Example 5

[0063] This example provides a method for evaluating the tensile and compressive properties of Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel at 4°C and 37°C, including the following steps specifically: Step 1: Fill the Gelatin 3 / PAA 7 / PDA@Ag / CTAB prepolymer solution obtained in Example 1 above into a groove-shaped polytetrafluoroethylene mold with a length of (50 mm) × width of (10 mm) × height of (2 mm), and heat it at 80°C for 40 min to obtain a 2-mm-thick Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel.

[0064] Step 2: Place the hydrogel obtained in Step 1 at 4°C and 37°C respectively for constant temperature treatment for 30 min.

[0065] Step 3: Use a universal testing machine to perform tensile and compression tests on the hydrogel after the constant temperature treatment in Step 2.

[0066] Experimental results: As shown in Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 , when the temperature changes from 4°C to 37°C, the elongation at break of the Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel increases by 2.4 times (from 397.6% to 964.5%), indicating that the Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel has stronger tensile and extensibility at 37°C; the tensile modulus decreases by 2.3 times (from 0.7 kPa to 0.3 kPa), indicating that the Gelatin 3 / PAA 7The / PDA@Ag / CTAB hydrogel is more prone to tensile deformation and has better flexibility; it is worth noting that Gelatin at 4 °C and 37 °C 3 / PAA 7 The / PDA@Ag / CTAB hydrogel has similar tensile toughness (376.6 kJ / m 3 and 359.2 kJ / m 3 ), which means that the Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogels at 37 °C and 4 °C both have good tensile toughness. In terms of compression performance, the Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel shows similar mechanical behavior. When the temperature changes from 4 °C to 37 °C, the compression stress of the Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel decreases by 3.9 times (from 728.6 kPa to 184.8 kPa) when the compression deformation rate is 80%, and the compression modulus decreases by 5 times (from 1.5 kPa to 0.3 kPa), indicating that the Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel is more prone to compression deformation.

[0067] This shows that the Gelatin 3 / PAA 7 / PDA@Ag / CTAB hydrogel has stronger deformation ability and compliance under body temperature conditions, can deform under a smaller external force, conform to the curves and movements of body parts, and has the ability to closely fit the complex shape of the wound environment under body temperature conditions.

[0068] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for preparing a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering, characterized in that The steps include: Using a one-pot mixing method, freeze-dried powder of polydopamine nanoparticles loaded with silver nanoparticles, polymer monomers, crosslinking agents, initiators and surfactants were added to a gelatin solution with a concentration of 15.50 wt% and mixed evenly to obtain a prepolymer solution; the prepolymer solution was filled into a mold and heated to induce polymerization to obtain a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering; The amount of the polydopamine nanoparticle freeze-dried powder loaded with silver nanoparticles is 0.10 wt% of the prepolymer solution, the amount of the polymer monomer is 24.50 wt% of the prepolymer solution, the amount of the crosslinking agent is 0.055 wt% of the prepolymer solution, the amount of the initiator is 0.60 wt% of the prepolymer solution, and the amount of the surfactant is 7.00 wt% of the prepolymer solution; The polymer monomer is one of acrylic acid and methacrylic acid; and the surfactant is hexadecyltrimethylammonium bromide.

2. A method for preparing a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering according to claim 1, characterized in that The polydopamine nanoparticle freeze-dried powder loaded with silver nanoparticles is prepared according to the following method: (1) dopamine hydrochloride, ammonium persulfate, anhydrous ethanol and pure water are prepared into a dopamine hydrochloride ethanol / water mixed solution by a solution oxidation method, the pH value of the dopamine hydrochloride ethanol / water mixed solution is adjusted with an alkali solution, the reaction is stirred, the dopamine hydrochloride is oxidized and self-polymerized to form polydopamine nanoparticles, the particles are centrifuged and washed with a detergent, and freeze-dried to obtain polydopamine freeze-dried powder; (2) using a reduction deposition method, adjusting the pH value of the silver salt aqueous solution to alkaline with an alkali solution, and then adding the polydopamine freeze-dried powder obtained in step (1) to the silver salt aqueous solution; stirring the reaction at a temperature of 15-30° C. and a speed of 500-700 rpm for 1-2 h, in situ reducing the silver salt on the surface of the polydopamine nanoparticles to generate silver nanoparticles, washing with a detergent by centrifugation, and freeze-drying to obtain a polydopamine nanoparticle freeze-dried powder loaded with silver nanoparticles; The pH value of step (1) is adjusted to 10-11; the temperature of the stirring reaction is 15-30°C, the time of the stirring reaction is 12-36 h, and the stirring speed is 500-700 rpm; the alkali solution is ammonia water, sodium hydroxide solution, potassium hydroxide solution or sodium bicarbonate solution; the detergent is pure water and anhydrous ethanol; The silver salt in step (2) is silver nitrate.

3. The method for preparing a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering according to claim 1, characterized in that The gelatin solution is prepared by adding gelatin to pure water, stirring and dissolving the mixture in a 60-80°C water bath to obtain a gelatin solution with a concentration of 15.50 wt%.

4. The method for preparing a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering according to claim 1, characterized in that : The crosslinking agent is one of N,N'-methylenebisacrylamide, bisacrylamide, polyethylene glycol diacrylate and polyethylene glycol dimethacrylate; the initiator is potassium persulfate or ammonium persulfate.

5. The method for preparing a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering according to claim 1, characterized in that The heat-induced polymerization is carried out by heating at 75-85°C for 30-120 min.

6. The method for preparing a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering according to claim 1, characterized in that : The mold is a square polytetrafluoroethylene or silicone mold; the filling of the prepolymer liquid into the mold is to control the thickness of the multifunctional hydrogel finally obtained by controlling the amount of prepolymer liquid added.

7. A multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties prepared by the preparation method according to any one of claims 1 to 6.

8. Use of a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering according to claim 7 in the preparation of a patch with switchable mechanical and adhesive properties.

9. According to claim 7, a multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties is used to prepare a temperature-driven intelligent medical multifunctional wound dressing that can fit tightly at body temperature and fall off naturally at low temperature.

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