A multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties, its preparation method, and its applications.

Abstract

This invention belongs to the interdisciplinary field of biomedical engineering, materials science, and tissue engineering, and discloses a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering, its preparation method, and applications. The invention consists of acrylic acid, gelatin, hexadecyltrimethylammonium bromide, polydopamine nanoparticles loaded with silver nanoparticles, and water. This invention not only exhibits excellent adhesion and mechanical properties to skin tissue but also possesses switchable mechanical and adhesive properties, achieving durable and repeatable adhesion. The temperature-triggered hydrogel prepared by this invention is simple to process, low in cost, and introduces no toxic chemicals. It can achieve a close fit at body temperature and natural detachment at low temperatures, driven by temperature, and maintains excellent adhesion properties even in complex environments, thus promoting the development of intelligent medical multifunctional wound dressings.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of biomedical engineering, materials science and tissue engineering, and specifically relates to a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering, its preparation method and application. Background Technology

[0002] Smart hydrogel materials, with their diverse functionalities, excellent softness, superior stretchability, and good biocompatibility, have great application potential in interdisciplinary fields such as biomedical engineering, materials science, and tissue engineering, becoming a research hotspot in wound dressing applications. Furthermore, with the development of modern medicine, tissue engineering, materials science, and biomedicine are placing increasingly stringent demands on the performance and function of biomaterials, leading to growing attention on the research and exploration of smart hydrogels.

[0003] Temperature-triggered hydrogels play a crucial role in wound dressing applications, achieving strong adhesion at high temperatures and easy detachment at low temperatures in response to changes in ambient temperature. Traditional dressings struggle to maintain wound moisture, easily adhere to granulation tissue hindering healing, and suffer from insufficient adhesion leading to easy detachment, or excessive adhesion causing secondary damage to the wound upon removal. Temperature-triggered hydrogel dressings, however, sense changes in wound and environmental temperature, maintaining moisture and preventing adhesion, adhering firmly as needed and detaching as required, accelerating wound healing and protecting the wound from secondary trauma. Although research on temperature-triggered hydrogels has yielded results, challenges remain in practical application and performance control. The material's performance is not significantly affected by temperature changes, and its mechanical strength, adhesion, and durability require improvement. These issues significantly limit the widespread application of temperature-triggered hydrogels. Therefore, developing a hydrogel patch with highly efficient temperature-driven properties, close adhesion at body temperature, and natural detachment at low temperatures; breakthroughs in mechanical and adhesive properties; and significantly improved durability and repeatability has significant 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 shortcomings and deficiencies of the existing technology, the primary objective of this invention is to provide a method for preparing a multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties. This method constructs a gelatin / PAA / PDA@Ag / CTAB hydrogel, wherein acrylic acid (AA) and gelatin effectively enhance the biocompatibility and tissue adhesion of the hydrogel. Furthermore, gelatin imparts temperature-sensitive properties to the hydrogel, forming a stable three-dimensional network structure at low temperatures, where functional groups interact, leading to an increase in the hydrogel's modulus and a decrease in adhesion. At high temperatures, the molecular chain movement becomes more vigorous, the network structure becomes looser, and the functional groups are fully exposed, effectively interacting with the active sites on the adhesion surface, thereby reducing the hydrogel's modulus and improving its adhesion. In addition, the positively charged hexadecyltrimethylammonium bromide (CTAB) interacts with PAA... The strong electrostatic interactions between the chain segments and the stabilizing effect on the hydrophobic segments of the polydopamine nanoparticles (PDA@Ag) loaded with silver nanoparticles form hydrophobic binding regions in the hydrogel network. This dual effect makes the cross-linking of polymer chains more uniform and stable, thereby improving the mechanical properties of the hydrogel. At the same time, CTAB improves wettability by reducing surface tension and imparts positive charge to the hydrogel surface, thus enhancing the adhesion performance of the hydrogel in multiple dimensions. Therefore, this temperature-driven hydrogel not only has good adhesion and mechanical properties, but can also achieve strong adhesion at body temperature and easy desorption at low temperature through temperature triggering, realizing a temperature-driven, efficient, and intelligent adhesion function.

[0005] Another objective of this invention is to provide a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering, prepared by the above-described method.

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

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for preparing a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering includes the following steps:

[0009] A one-pot mixing method was used to add lyophilized polydopamine nanoparticles loaded with silver nanoparticles, polymer monomers, crosslinking agents, initiators, and surfactants to a 15.50 wt% gelatin solution and mix them evenly to obtain a prepolymer solution. The prepolymer solution was then filled into a mold and heated to induce polymerization, resulting in a multifunctional hydrogel (Gelatin / PAA / PDA@Ag / CTAB hydrogel) with switchable mechanical and adhesive properties based on temperature triggering.

[0010] The amount of the polydopamine nanoparticle lyophilized powder loaded with silver nanoparticles is 0.10 wt% of the prepolymer solution, the amount of polymer monomer is 24.50 wt% of the prepolymer solution, the amount of crosslinking agent is 0.055 wt% of the prepolymer solution, the amount of initiator is 0.60 wt% of the prepolymer solution, and the amount of surfactant is 7.00 wt% of the prepolymer solution.

[0011] The polymer monomer is one of acrylic acid and methacrylic acid; the surfactant is hexadecyltrimethylammonium bromide.

[0012] The lyophilized powder of polydopamine nanoparticles loaded with silver nanoparticles was prepared by the following method:

[0013] (1) By solution oxidation, dopamine hydrochloride, ammonium persulfate, anhydrous ethanol and pure water are prepared into a dopamine hydrochloride ethanol / water mixed solution. The pH value of the dopamine hydrochloride ethanol / water mixed solution is adjusted with alkali solution and stirred to react. Dopamine hydrochloride is oxidized and self-polymerized to form polydopamine nanoparticles. After centrifugation and washing with detergent and freeze drying, polydopamine (PDA) freeze-dried powder is obtained.

[0014] (2) Using the reduction deposition method, the pH value of the silver salt aqueous solution was adjusted to alkaline with alkaline solution, and then the polydopamine lyophilized powder obtained in step (1) was added to the silver salt aqueous solution; the reaction was stirred at 500-700 rpm for 1-2 hours at 15-30℃, and silver salt was reduced in situ on the surface of polydopamine nanoparticles to generate silver nanoparticles. After centrifugation and washing with detergent and freeze-drying, polydopamine nanoparticles (PDA@Ag) lyophilized powder loaded with silver nanoparticles was obtained.

[0015] The pH value in step (1) is adjusted to 10-11; the temperature of the stirring reaction is 15-30℃, the stirring reaction time is 12-36 h, and the stirring speed is 500-700 rpm; the alkaline solution is ammonia water, sodium hydroxide solution, potassium hydroxide solution or sodium bicarbonate solution; the detergent is pure water and anhydrous ethanol.

[0016] In step (1), the molar ratio of dopamine hydrochloride to ammonium persulfate is 2:1; and the volume ratio of anhydrous ethanol to pure water is 2:7.

[0017] The silver salt mentioned in step (2) is silver nitrate.

[0018] The mass ratio of silver salt to polydopamine lyophilized powder in step (2) is 2:3.

[0019] The gelatin solution is obtained by adding gelatin to pure water and stirring to dissolve it in a water bath at 60-80℃, resulting in a gelatin solution with a concentration of 15.50wt%.

[0020] 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.

[0021] The heat-induced polymerization is carried out at 75-85℃ for 30-120 min.

[0022] The mold is a square polytetrafluoroethylene or silicone mold; the thickness of the final multifunctional hydrogel is controlled by controlling the amount of prepolymer added to fill the mold.

[0023] A multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties, prepared by the above-described method, is characterized by stretchability and compressibility. It exhibits stable and durable adhesion both above and below water. At body temperature (37°C), it displays low modulus, easy deformation (tensile modulus 0.3 kPa, compressive modulus 0.3 kPa), high elongation (elongation at break 964.5%), and strong adhesion (adhesion strength 17.8 kPa). At low temperature (4°C), it displays high modulus (tensile modulus 0.7 kPa, compressive modulus 1.5 kPa), resistance to deformation (compressive stress at 80% compressive deformation rate 728.6 kPa), and easy detachment (adhesion strength 6.7 kPa). This hydrogel can be used as a temperature-driven intelligent multifunctional medical wound dressing, enabling highly adaptable wound treatment applications that achieve close adhesion at body temperature and natural detachment at low temperatures.

[0024] The above-mentioned multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering is used in the preparation of patches with switchable mechanical and adhesive properties.

[0025] The aforementioned multifunctional hydrogel, based on temperature-triggered switchable mechanical and adhesive properties, is used to prepare a temperature-driven intelligent medical multifunctional wound dressing that achieves close adhesion at body temperature and natural detachment at low temperatures.

[0026] The present invention has the following advantages and beneficial effects compared with the prior art:

[0027] (1) The present invention is based on a multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties, which has temperature-triggered switchable adhesive properties.

[0028] (2) The multifunctional hydrogel based on temperature-triggered switchable mechanical and adhesive properties of the present invention has temperature-triggered switchable mechanical properties, namely stretchability, compressibility, etc.

[0029] (3) The multifunctional hydrogel prepared by the present invention based on temperature-triggered switchable mechanical and adhesive properties can be applied to the fields of intelligent wound dressing and tissue repair. Its temperature-triggered switchable adhesive properties can be used as intelligent wound dressings that can be applied on demand or as a gentle tissue repair material that will not cause secondary damage during the replacement process. In addition, its temperature-triggered switchable mechanical properties can meet the requirements for patch shape and deformation during treatment, thereby achieving close adhesion between the gel and the complex wound environment, as well as high wound adaptability to environmental changes during the wound repair process, thereby achieving a highly efficient treatment effect. Attached Figure Description

[0030] Figure 1 The FTIR spectra of AA, PDA@Ag, and CTAB are shown.

[0031] Figure 2 FTIR spectra of Gelatin and Gelatin / PAA / PDA@Ag / CTAB hydrogels.

[0032] Figure 3 The adhesion strength of Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel, Gelatin3 / PAA7 / PDA@Ag / DTAB hydrogel, and Gelatin3 / PAA7 / PDA@Ag / HTAB hydrogel to steel plates.

[0033] Figure 4 The adhesion strength of four different formulations of Gelatin / PAA / PDA@Ag / CTAB hydrogels to pigskin was determined at 4°C and 37°C.

[0034] Figure 5 Temperature-modulus curves for four different formulations of Gelatin / PAA / PDA@Ag / CTAB hydrogels.

[0035] Figure 6 Tensile stress-strain strength curves of Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel at 4℃ and 37℃.

[0036] Figure 7 The tensile modulus and toughness of Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel at 4℃ and 37℃ are determined.

[0037] Figure 8 The compressive stress-strain intensity curves of Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel at 4℃ and 37℃ are shown.

[0038] Figure 9The compressive modulus and toughness of Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel at 4℃ and 37℃. Detailed Implementation

[0039] The following specific embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention.

[0040] The following embodiments describe the preparation process of a multifunctional hydrogel with temperature-triggered switchable mechanical and adhesive properties, following these steps:

[0041] Step 1: Dopamine hydrochloride, ammonium persulfate, anhydrous ethanol, and pure water are prepared into a dopamine hydrochloride ethanol / water mixed solution by solution oxidation. The pH of the dopamine hydrochloride ethanol / water mixed solution is adjusted to 10-11 with alkaline solution. The mixture is stirred at 500-700 rpm at 15-30℃ for 12-36 h. After centrifugation and washing with pure water and anhydrous ethanol, and freeze-drying, polydopamine (PDA) lyophilized powder is obtained.

[0042] Step 2: Using a reduction deposition method, the pH of the silver salt (0.22 mmol / L) aqueous solution was adjusted to 10-11 with an alkaline solution. Then, the polydopamine lyophilized powder obtained in Step 1 was added to the above silver salt aqueous solution; the reaction was carried out at 15-30℃ and 500-700 rpm for 1-2 h with stirring. Silver salt was reduced in situ on the surface of the polydopamine nanoparticles to generate silver nanoparticles. After centrifugation and washing with pure water and anhydrous ethanol, and freeze-drying, polydopamine nanoparticles (PDA@Ag) lyophilized powder loaded with silver nanoparticles were obtained.

[0043] Step 3: Add gelatin to pure water and stir to dissolve in a water bath at 60-80℃ to obtain a gelatin solution with a concentration of 15.50 wt%.

[0044] Step 4: Using a one-pot mixing method, the lyophilized polydopamine nanoparticles (PDA@Ag) powder loaded with silver nanoparticles obtained in Step 2, polymer monomers, crosslinking agents, initiators, and surfactants are added to the gelatin solution obtained in Step 3 and mixed evenly to obtain a prepolymer solution. The prepolymer solution is filled into a polytetrafluoroethylene or silicone mold, and the thickness of the final gel patch is controlled by controlling the amount of prepolymer solution added. Heating induces polymerization to obtain a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering. The amount of lyophilized polydopamine nanoparticles loaded with silver nanoparticles is 0.10 wt% of the prepolymer solution, the amount of polymer monomers is 24.50 wt% of the prepolymer solution, the amount of crosslinking agent is 0.055 wt% of the prepolymer solution, the amount of initiator is 0.60 wt% of the prepolymer solution, and the amount of surfactant is 7.00 wt% of the prepolymer solution. The polymer monomer is one of acrylic acid and methacrylic acid; the surfactant is hexadecyltrimethylammonium bromide.

[0045] The multifunctional hydrogel prepared in this invention, based on temperature-triggered switchable mechanical and adhesive properties, can be applied to the fields of intelligent wound dressing and tissue repair. Its temperature-triggered switchable adhesive properties allow it to be used as an on-demand intelligent wound dressing or for gentle tissue repair without causing secondary damage during replacement. Furthermore, its temperature-triggered switchable mechanical properties can meet the requirements for patch shape and deformation during treatment, thereby achieving a tight fit between the gel and the complex wound environment, and a high degree of wound adaptability to environmental changes during wound repair, thus achieving highly efficient therapeutic effects. This provides a new approach for the development of intelligent wound dressing and tissue repair.

[0046] Example 1

[0047] This embodiment provides four methods for preparing gelatin / PAA / PDA@Ag / CTAB hydrogels with different formulation ratios, including the following specific steps:

[0048] Step 1: Mix dopamine hydrochloride (225 mg), ammonium persulfate (139.5 mg), anhydrous ethanol (10 mL), and pure water (35 mL) evenly. Adjust the pH to 10 by adding ammonia. Stir at 600 rpm at 25°C for 24 h. After centrifugation and washing with pure water and anhydrous ethanol, and freeze-drying, polydopamine (PDA) lyophilized powder is obtained.

[0049] Step 2: Using a reduction deposition method, the pH of the silver nitrate (0.22 mmol / L) aqueous solution was adjusted to 10-11 with ammonia. Then, the polydopamine lyophilized powder (147 mg) obtained in Step 1 was added to the above silver nitrate aqueous solution; the mixture was stirred at 25 °C for 1 h at a stirring speed of 500 rpm to reduce silver salt in situ on the surface of the polydopamine nanoparticles, generating silver nanoparticles. After centrifugation and washing with pure water and anhydrous ethanol, and freeze-drying, polydopamine nanoparticles (PDA@Ag) lyophilized powder loaded with silver nanoparticles were obtained.

[0050] Step 3: Add gelatin (2.10 g) to pure water (11.45 mL), stir and dissolve in a 70°C water bath to obtain a gelatin solution with a concentration of 15.50 wt%.

[0051] Step 4: Using a one-pot mixing method, 0.02 g of lyophilized polydopamine nanoparticles (PDA@Ag) loaded with silver nanoparticles obtained in Step 2, 4.90 g of acrylic acid, 0.01 g of N,N'-methylenebisacrylamide, 0.12 g of ammonium persulfate, and 1.40 g of hexadecyltrimethylammonium bromide were added to the gelatin solution obtained in Step 3 and mixed thoroughly to obtain a Gelatin3 / PAA7 / PDA@Ag / CTAB prepolymer solution with a mass ratio of Gelatin:PAA:CTAB of 3:7:2. The prepolymer solution was filled into a polytetrafluoroethylene mold, and the thickness of the final gel patch was controlled by adjusting the amount of prepolymer solution added. After heating at 80°C for 40 min, a hydrogel was obtained, denoted as Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel.

[0052] The hexadecyltrimethylammonium bromide (CTAB) in the above prepolymer solution was replaced with an equimolar amount of dodecyltrimethylammonium bromide (DTAB) (1.18 g), resulting in a Gelatin3 / PAA7 / PDA@Ag / DTAB prepolymer solution with dodecyltrimethylammonium bromide (DTAB) as the surfactant. The resulting hydrogel is denoted as Gelatin3 / PAA7 / PDA@Ag / DTAB hydrogel.

[0053] The cetyltrimethylammonium bromide (CTAB) in the above prepolymer solution was replaced with an equimolar amount of hexyltrimethylammonium bromide (HTAB) (0.86 g), resulting in a Gelatin3 / PAA7 / PDA@Ag / HTAB prepolymer solution with hexyltrimethylammonium bromide (HTAB) as the surfactant. The resulting hydrogel is denoted as Gelatin3 / PAA7 / PDA@Ag / HTAB hydrogel.

[0054] The amounts of gelatin and acrylic acid added to the above prepolymer solution were modified to 0.70 g and 6.30 g, respectively, to obtain a Gelatin1 / PAA9 / PDA@Ag / CTAB prepolymer solution with a Gelatin:PAA:CTAB mass ratio of 1:9:2. The resulting hydrogel is denoted as Gelatin1 / PAA9 / PDA@Ag / CTAB hydrogel.

[0055] The amounts of gelatin and acrylic acid added to the above prepolymer solution were modified to 1.40 g and 5.60 g, respectively, to obtain a Gelatin2 / PAA8 / PDA@Ag / CTAB prepolymer solution with a Gelatin:PAA:CTAB mass ratio of 2:8:2. The resulting hydrogel is denoted as Gelatin2 / PAA8 / PDA@Ag / CTAB hydrogel.

[0056] The amounts of gelatin and acrylic acid added to the above prepolymer solution were modified to 2.80 g and 4.20 g, respectively, to obtain a Gelatin4 / PAA6 / PDA@Ag / CTAB prepolymer solution with a Gelatin:PAA:CTAB mass ratio of 4:6:2. The resulting hydrogel is denoted as Gelatin4 / PAA6 / PDA@Ag / CTAB hydrogel.

[0057] Infrared spectroscopy analysis was performed on the obtained Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel, and the experimental results are as follows: Figure 1 , Figure 2 As shown, from the spectral data of hexadecyltrimethylammonium bromide (CTAB), 2929 cm⁻¹ -1 A stretching vibration peak of -CH3 was observed, and the stretching vibration of the bromide ion appeared at 723 cm⁻¹. -1 For PDA@Ag, 3000-3500 cm -1 The broad peak is attributed to the merging of OH and NH peaks, 1284 cm⁻¹. -1 The peak at 1590 cm⁻¹ is the stretching vibration peak of phenolic CO. Additionally, the peak at 1590 cm⁻¹... -1 This is the stretching vibration peak of the aromatic C=C group. 829 cm⁻¹ -1 The peak is the out-of-plane vibration peak of the CH group in aromatic hydrocarbons. For acrylic acid (AA), it is 2700-3400 cm⁻¹. -1 A combined peak of the stretching vibrations of OH and CH appeared on both sides. The peak value appeared at 1634 cm⁻¹. -1 and 1697 cm -1 These vibrations are attributed to C=C and C=O vibrations, respectively. For gelatin, the peak occurs at 3286 cm⁻¹. -1 and 2944 cm -1It belongs to the NH and CH vibrations respectively. 1634 cm -1 This is the stretching vibration peak of C=O. For Gelatin / PAA / PDA@Ag / CTAB hydrogel, the peak value is 3000-3500 cm⁻¹. -1 Broad and narrow peaks for OH and NH appeared on the left and right sides, at 2919 cm⁻¹. -1 It is a stretching vibration belonging to CH, with a peak at 1646 cm⁻¹. -1 Belongs to C=O vibration, 1200 cm -1 The peak at 1634 cm⁻¹ is the stretching vibration peak of phenolic CO. -1 The disappearance of the double bond peaks belonging to C=C proves that C=C has undergone polymerization.

[0058] Example 2

[0059] This embodiment provides a method for evaluating the lap shear adhesion performance of hydrogels with three different surfactants to steel plates, including the following steps:

[0060] Step 1: Fill the prepolymer liquids of the three different surfactants obtained in Example 1 into a silicone mold with a length (40 mm) × width (20 mm) × height (2 mm), and heat at 80°C for 40 min to obtain hydrogels of the three different surfactants.

[0061] Step 2: Evaluate the adhesion performance of the two materials using a steel plate as the adhesive substrate. The hydrogel is sandwiched between two identical substrate materials. Then, a 1 kg weight is applied to the overlapping area of ​​the substrate material and hydrogel for 30 seconds.

[0062] Step 3: Clamp the substrate materials at both ends using the tensile clamps of the universal testing machine, and test the adhesion performance using the lap shear method. The tensile rate is 15 mm / min.

[0063] Experimental results: such as Figure 3 The adhesion strengths of the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel, Gelatin3 / PAA7 / PDA@Ag / DTAB hydrogel, and Gelatin3 / PAA7 / PDA@Ag / HTAB hydrogel shown are 46.5 kPa, 26.1 kPa, and 6.4 kPa, respectively. This indicates that compared to hydrogels with other surfactants, the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel with CTAB surfactant exhibits better adhesion ability.

[0064] Example 3

[0065] This embodiment provides a method for evaluating the lap shear adhesion properties of four different formulations of hydrogels on pigskin at 4℃ and 37℃, including the following steps:

[0066] Step 1: The four prepolymer solutions with different formulation ratios obtained in Example 1 above (Gelatin3 / PAA7 / PDA@Ag / CTAB, Gelatin1 / PAA9 / PDA@Ag / CTAB, Gelatin2 / PAA8 / PDA@Ag / CTAB, Gelatin4 / PAA6 / PDA@Ag / CTAB) were filled into a silicone mold with a length (40 mm) × width (20 mm) × height (2 mm), and heated at 80°C for 40 min to obtain four hydrogels with different formulation ratios.

[0067] Step 2: Place the hydrogel obtained in Step 1 at 4℃ and 37℃ for constant temperature treatment for 30 min respectively.

[0068] Step 3: Evaluate the adhesion performance of the two materials using pigskin as the adhesive substrate. A hydrogel, after being treated at 4°C or 37°C, is sandwiched between two identical substrate materials. Then, a 1 kg weight is applied to the overlapping area of ​​the substrate material and hydrogel for 30 seconds.

[0069] Step 4: Clamp the substrate materials at both ends using the tensile clamps of the universal testing machine, and test the adhesion performance using the lap shear method. The tensile rate is 15 mm / min.

[0070] Experimental results: such as Figure 4 As shown, compared to other formulations of hydrogels, the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel with a mass ratio of Gelatin:PAA:CTAB of 3:7:2 exhibits higher adhesion strength at 37°C and lower adhesion strength at 4°C. This indicates that among hydrogels with different formulations, the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel has the best temperature-triggered switchable adhesion performance.

[0071] For the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel, the adhesion strength to pigskin at 37℃ (17.8 kPa) is much greater than that at 4℃ (6.7 kPa), indicating that the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel has the ability to adhere tightly to the bonding surface at body temperature and can detach naturally after cooling treatment.

[0072] Example 4

[0073] This embodiment provides a method for evaluating the changes and trends of viscoelastic properties of four different formulations of hydrogels at different temperatures, including the following steps:

[0074] Step 1: The four prepolymer solutions with different formulation ratios obtained in Example 1 above (Gelatin3 / PAA7 / PDA@Ag / CTAB, Gelatin1 / PAA9 / PDA@Ag / CTAB, Gelatin2 / PAA8 / PDA@Ag / CTAB, Gelatin4 / PAA6 / PDA@Ag / CTAB) were filled into cylindrical silicone molds with a diameter of (25 mm) × height of (2 mm) respectively, and heated at 80 ℃ for 40 min to obtain four hydrogels with different formulation ratios.

[0075] Step 2: Clean and dry the rheometer test platform beforehand, and spread the sample evenly on the test platform to complete the sample installation.

[0076] Step 3: Set the rheometer temperature scanning range to 5℃ to 50℃ and the oscillation frequency to 1Hz. Data should be recorded every 1.5 minutes.

[0077] Experimental results: such as Figure 5 As shown, compared to Gelatin1 / PAA9 / PDA@Ag / CTAB hydrogels and Gelatin2 / PAA8 / PDA@Ag / CTAB hydrogels, Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogels and Gelatin4 / PAA6 / PDA@Ag / CTAB hydrogels, which have higher gelatin content, exhibit a stronger temperature response. Around 35°C, both storage modulus and loss modulus show a clear inflection point, allowing for better switching of mechanical properties driven by the transition between body temperature and low-temperature conditions. Furthermore, compared to Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogels, Gelatin4 / PAA6 / PDA@Ag / CTAB hydrogels generally have lower storage and loss moduli. This means that Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogels can withstand greater stress, possess better energy absorption capacity, and offer higher durability and reusability when used as wound dressings, better adapting to the challenges of complex environments.

[0078] For the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel with a mass ratio of Gelatin:PAA:CTAB of 3:7:2, the storage modulus of the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel gradually decreases with increasing temperature, reaching a minimum at 32.5℃, while the loss modulus gradually increases, reaching a maximum at 40℃. This indicates that the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel exhibits good deformation ability at 37℃, better maintaining its specific shape, while at 4℃, it demonstrates good resistance to deformation. This means that the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel can achieve the ideal effect of changing shape at body temperature, closely adhering to the wound environment, maintaining its shape at low temperatures, and resisting deformation. Furthermore, under body temperature conditions, the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel can also achieve a close fit even in complex wound environments.

[0079] Example 5

[0080] This embodiment provides a method for evaluating the tensile and compressive properties of Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogels with a Gelatin:PAA:CTAB mass ratio of 3:7:2 at 4°C and 37°C, including the following steps:

[0081] Step 1: Fill the Gelatin3 / PAA7 / PDA@Ag / CTAB prepolymer obtained in Example 1 above with a mass ratio of Gelatin:PAA:CTAB of 3:7:2 into a grooved polytetrafluoroethylene mold with dimensions of length (50 mm) × width (10 mm) × height (2 mm). After heating at 80°C for 40 min, a 2 mm thick Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel is obtained.

[0082] Step 2: Place the hydrogel obtained in Step 1 at 4℃ and 37℃ for constant temperature treatment for 30 min respectively.

[0083] Step 3: Use a universal testing machine to perform tensile and compression tests on the hydrogel after the isothermal treatment in Step 2.

[0084] Experimental results: such as Figure 6 , Figure 7 , Figure 8 , Figure 9As shown, when the temperature changes from 4℃ to 37℃, the elongation at break of the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel increases by 2.4 times (397.6% vs. 964.5%), indicating that the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel has stronger tensile strength at 37℃; the tensile modulus decreases by 2.3 times (0.7kPa vs. 0.3kPa), indicating that the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel at 37℃ is more prone to tensile deformation and has better flexibility; it is worth noting that the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel at 4℃ and 37℃ have similar tensile toughness (376.6kJ / m). 3 and 359.2 kJ / m 3 This means that both the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogels at 37℃ and 4℃ exhibit good tensile toughness. Regarding compressive properties, the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogels show similar mechanical behavior. When the temperature changes from 4℃ to 37℃, the compressive stress of the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel at 80% compression set decreases by 3.9 times (728.6 kPa vs. 184.8 kPa), and the compressive modulus decreases by 5 times (1.5 kPa vs. 0.3 kPa), indicating that the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel at 37℃ is more prone to compressive deformation.

[0085] This indicates that the Gelatin3 / PAA7 / PDA@Ag / CTAB hydrogel has stronger deformation capacity and compliance under body temperature conditions. It can deform under small external forces, conform to the curves and movements of body parts, and has the ability to maintain close contact with complex wound environments under body temperature conditions.

[0086] 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 changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within 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 following steps are included: A one-pot mixing method was used to add lyophilized polydopamine nanoparticles loaded with silver nanoparticles, polymer monomers, crosslinking agents, initiators, and surfactants to a 15.50 wt% gelatin solution and mix them evenly to obtain a prepolymer solution. The prepolymer solution was then filled into a mold and heated to induce polymerization, resulting in a multifunctional hydrogel with switchable mechanical and adhesive properties based on temperature triggering. The amount of the polydopamine nanoparticle lyophilized powder loaded with silver nanoparticles is 0.10 wt% of the prepolymer solution, the amount of polymer monomer is 24.50 wt% of the prepolymer solution, the amount of crosslinking agent is 0.055 wt% of the prepolymer solution, the amount of initiator is 0.60 wt% of the prepolymer solution, and the amount of surfactant is 7.00 wt% of the prepolymer solution. The polymer monomer is acrylic acid; the surfactant is hexadecyltrimethylammonium bromide; The prepolymer solution is a Gelatin3 / PAA7 / PDA@Ag / CTAB prepolymer solution with a mass ratio of Gelatin:PAA:CTAB of 3:7:

2.

2. 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 lyophilized powder of polydopamine nanoparticles loaded with silver nanoparticles was prepared according to the following method: (1) By solution oxidation, dopamine hydrochloride, ammonium persulfate, anhydrous ethanol and pure water are prepared into a dopamine hydrochloride ethanol / water mixed solution. The pH value of the dopamine hydrochloride ethanol / water mixed solution is adjusted with alkali solution and stirred to react. Dopamine hydrochloride is oxidized and self-polymerized to form polydopamine nanoparticles. After centrifugation and washing with detergent and freeze-drying, polydopamine freeze-dried powder is obtained. (2) Using the reduction deposition method, the pH value of the silver salt aqueous solution was adjusted to alkaline with alkaline solution, and then the polydopamine lyophilized powder obtained in step (1) was added to the silver salt aqueous solution; the reaction was stirred at 500-700 rpm for 1-2 h at 15-30℃, and silver salt was reduced in situ on the surface of polydopamine nanoparticles to generate silver nanoparticles. After centrifugation and washing with detergent and freeze-drying, polydopamine nanoparticle lyophilized powder loaded with silver nanoparticles was obtained. The pH value in step (1) is adjusted to 10-11; the temperature of the stirring reaction is 15-30℃, the stirring reaction time is 12-36 h, and the stirring speed is 500-700 rpm; the alkaline 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 mentioned 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 and stirring to dissolve it in a water bath at 60-80°C, resulting in 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 at 75-85℃ 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 thickness of the final multifunctional hydrogel is controlled by controlling the amount of prepolymer added when filling the mold with the prepolymer.

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

8. The application of the temperature-triggered switchable mechanical and adhesive properties of the multifunctional hydrogel according to claim 7 in the preparation of patches with switchable mechanical and adhesive properties.

9. The multifunctional hydrogel based on temperature-triggered switchable mechanical and adhesive properties as described in claim 7, applied to the preparation of a temperature-driven intelligent medical multifunctional wound dressing that achieves close adhesion at body temperature and natural detachment at low temperature.

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