Temperature-sensitive reversible phase-change hydrogel with high-humidity adhesion and preparation method of temperature-sensitive reversible phase-change hydrogel

Abstract

The invention discloses a temperature-sensitive reversible phase change hydrogel with high humidity adhesion and a preparation method thereof, and belongs to the technical field of hydrogel preparation. The hydrogel is prepared by taking poly N-isopropylacrylamide as a matrix and aldehyde hyaluronic acid and gallic acid grafted chitosan as a reinforcing agent and a tackifier together through mechanical stirring. The hydrogel prepared by the invention has relatively high strength, relatively excellent wet adhesion, biocompatibility, temperature-sensitive phase change and temperature-sensitive phase change reversibility, is high in phase change response speed and simple in preparation method, is mainly applied to the fields of medical treatment, plastic surgery and the like, and has remarkable economic value and social benefit.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogel preparation, and particularly relates to a temperature-sensitive reversible phase-change hydrogel with high wet adhesiveness and a preparation method thereof. Background Art

[0002] As a commonly used drug carrier, hydrogel has good biocompatibility, antibacterial property, adhesiveness, and drug-loading property, and is widely used in the field of wound dressings. However, traditional hydrogels are in a solid state during use, with poor adhesion performance and easy to fall off at the wound site. Especially when there is still bleeding on the wound surface, due to the high cohesive energy of the solid hydrogel and poor wet adhesiveness, it is more difficult to adhere to the wound surface. But if the adhesion performance of the hydrogel is too good, when removing the hydrogel from the wound during dressing change or wound inspection, it may cause secondary cracking of the already healed wound. Especially for irregular wounds, removing the hydrogel may cause wound dislocation and more serious damage to the wound. Summary of the Invention

[0003] Aiming at the problems existing in the application of current traditional hydrogels, the present invention provides a temperature-sensitive reversible phase-change hydrogel with high wet adhesiveness and a preparation method thereof. The hydrogel prepared by the present invention has high strength, excellent wet adhesiveness, biocompatibility, temperature-sensitive phase change property, and temperature-sensitive phase change reversibility, and has a fast phase change response speed and a simple preparation method. It is mainly used in the fields of medical treatment and plastic surgery, etc., and has significant economic value and social benefits.

[0004] To achieve the above object, the present invention adopts the following technical scheme: A temperature-sensitive reversible phase-change hydrogel with high wet adhesiveness, which is prepared by mechanical stirring with poly(N-isopropylacrylamide) as the matrix, and aldehyde-modified hyaluronic acid and gallic acid-grafted chitosan as the reinforcing agent and tackifier together.

[0005] Further, the polymerization degree of the aldehyde-modified hyaluronic acid is 500 - 1000, and the oxidation degree is 5% - 20%.

[0006] Further, the polymerization degree of the gallic acid-grafted chitosan is 10000 - 20000, and the grafting rate of gallic acid is 6% - 12%.

[0007] The preparation method of the temperature-sensitive reversible phase-change hydrogel comprises the following steps: 1) Adding poly(N-isopropylacrylamide) into deionized water, and mechanically stirring at room temperature for 30 - 60 min to obtain a poly(N-isopropylacrylamide) solution; 2) Adding aldehyde-modified hyaluronic acid into deionized water, and mechanically stirring at room temperature for 30 - 60 min to obtain an aldehyde-modified hyaluronic acid solution; 3) Add the gallic acid grafted chitosan into deionized water and mechanically stir for 30 - 60 min at room temperature to obtain a gallic acid grafted chitosan solution; 4) Add the aldehyde - modified hyaluronic acid solution and the gallic acid grafted chitosan solution prepared in steps 2) and 3) into the poly(N - isopropylacrylamide) solution prepared in step 1), and mechanically stir for 1 - 2 h at 0 - 10 °C to obtain the thermosensitive reversible phase - change hydrogel.

[0008] Further, the concentration of the poly(N - isopropylacrylamide) solution obtained in step 1) is 0.1 - 0.4 g / mL.

[0009] Further, the concentration of the aldehyde - modified hyaluronic acid solution obtained in step 2) is 4 - 75 mg / mL.

[0010] Further, the concentration of the gallic acid grafted chitosan solution obtained in step 3) is 7.5 - 150 mg / mL.

[0011] Further, the volume ratio of the aldehyde - modified hyaluronic acid solution, the gallic acid grafted chitosan solution to the poly(N - isopropylacrylamide) solution used in step 4) is 1:(1 - 1.6):(2 - 30).

[0012] The remarkable advantages of the present invention are as follows: (1) The phase - change temperature of poly(N - isopropylacrylamide) is about 32 °C. When the temperature is lower than 32 °C, it is a colorless transparent liquid, and when the temperature is higher than 32 °C, it is a white turbid liquid with low strength and poor application performance. In the present invention, using aldehyde - modified hyaluronic acid and gallic acid grafted chitosan as reinforcing agents, after the phase - change of poly(N - isopropylacrylamide), the long molecular chains of chitosan and hyaluronic acid are tightly entangled with the molecular chains of poly(N - isopropylacrylamide) through hydrogen - bond interaction and dynamic covalent - bond interaction to form a stable network structure. At the same time, under the action of the steric - hindrance effect of gallic acid and the rigid benzene ring on the chitosan molecular chain, this network structure is very stable. Therefore, the hydrogel prepared in the present invention is a white solid hydrogel with high strength after phase - change.

[0013] (2) When the temperature is lower than the phase transition temperature of poly(N-isopropylacrylamide), the hydrophilic interaction dominated by amide groups in poly(N-isopropylacrylamide) is stronger than the hydrophobic interaction dominated by isopropyl groups. The molecular chain segments unfold and can be stably dissolved in deionized water. At this time, through the hydrogen bond interaction between the aldehyde group-modified hyaluronic acid molecular chain, the gallic acid-grafted chitosan molecular chain and the poly(N-isopropylacrylamide) molecular chain, a yellow liquid hydrogel can be formed, but the gel strength is very low. When the temperature is higher than the phase transition temperature, the hydrophobic interaction dominated by isopropyl groups in poly(N-isopropylacrylamide) is stronger than the hydrophilic interaction dominated by amide groups. The molecular chain segments curl. At this time, through the hydrogen bond interaction and dynamic covalent bond interaction between the aldehyde group-modified hyaluronic acid molecular chain, the gallic acid-grafted chitosan molecular chain and the poly(N-isopropylacrylamide) molecular chain, a white solid hydrogel can be formed, completing the phase transition of the hydrogel. When the temperature is lower than the phase transition temperature again, the hydrophilic interaction dominated by amide groups in poly(N-isopropylacrylamide) is stronger than the hydrophobic interaction dominated by isopropyl groups. The molecular chain segments unfold again. At this time, through the hydrogen bond interaction between the aldehyde group-modified hyaluronic acid molecular chain, the gallic acid-grafted chitosan molecular chain and the poly(N-isopropylacrylamide) molecular chain, a yellow liquid hydrogel is formed again, completing the reversible phase transition of the hydrogel. Because with the change of temperature, the curling and unfolding speed of the poly(N-isopropylacrylamide) molecular chain segments is relatively fast, and moreover, the steric hindrance effect of gallic acid on the chitosan molecular chain can increase the distance between the hyaluronic acid molecular chain, the chitosan molecular chain and the poly(N-isopropylacrylamide) molecular chain, providing a larger space size for the diffusion of free water. Therefore, the hydrogel prepared by the present invention has a relatively fast phase transition response speed.

[0014] (3) The present invention uses aldehyde group-modified hyaluronic acid and gallic acid-grafted chitosan as thickeners. Among them, hydrogen bonds can be formed between the hydroxyl groups and amino groups on the gallic acid-grafted chitosan molecular chain and the hydroxyl groups and amino groups on the skin surface. Dynamic covalent bonds can be formed between the aldehyde groups on the aldehyde group-modified hyaluronic acid molecular chain and the amino groups on the skin surface. Electrostatic interactions can be formed between the carboxyl groups on the aldehyde group-modified hyaluronic acid molecular chain and the amino groups on the skin surface. Through the above effects, the hydrogel prepared by the present invention has relatively excellent wet adhesion performance, which is completely different from the mechanism in the existing reports that Schiff base reaction between the aldehyde groups of aldehyde group-modified hyaluronic acid and the amino groups of chitosan is used to form dynamic covalent bonds, thereby forming a solid hydrogel. The hydrogel prepared by the present invention can undergo conformational changes to form a solid hydrogel when heated, while the hydrogels prepared in the existing reports do not have thermosensitive phase change properties and thermosensitive phase change reversibility.

[0015] (4) When the temperature is lower than the phase transition temperature, the hydrogel of the present invention is a yellow liquid hydrogel with low complex viscosity, which is beneficial to drug dispersion. When the hydrogel of the present invention comes into contact with a wound, since the wound temperature is higher than the phase transition temperature, at this time, the yellow liquid hydrogel rapidly transforms into a white solid hydrogel. At the same time, due to the excellent wet adhesion of the hydrogel of the present invention, it can firmly adhere to the wound surface. Even if there is bleeding from the wound, it will not fall off from the wound. When it is necessary to replace the hydrogel or check the wound, apply an ice pack with a lower temperature on the surface of the solid hydrogel. At this time, the white solid hydrogel undergoes a reversible phase transition and transforms back into a yellow liquid hydrogel. Therefore, the hydrogel can be removed from the wound by wiping or rinsing, effectively avoiding secondary damage to the wound caused by removing traditional solid hydrogels from the wound. In addition, the components for preparing the hydrogel of the present invention are poly(N-isopropylacrylamide), aldehyde-modified hyaluronic acid, and gallic acid-grafted chitosan, all of which have excellent biocompatibility. Therefore, the hydrogel of the present invention also has excellent biocompatibility and has no harmful effects on the human body.

[0016] (5) The hydrogel prepared by the present invention has high strength, excellent wet adhesion, biocompatibility, thermosensitive phase transition property, and thermosensitive phase transition reversibility, and has a fast phase transition response speed. Its phase transition temperature is 33 - 34 °C, the phase transition time is 1.6 - 2.0 s, the storage modulus at 37 °C is 322.1 - 367.5 Pa, the complex viscosity at 5 °C is 1523.8 - 1643.6 Pa·s, the complex viscosity at 37 °C is 48720 - 59484 Pa·s, the adhesion time is 27.5 - 29.8 h, and the burst pressure is 38.8 - 42.6 kPa. It is mainly used in the fields of medical treatment and plastic surgery, etc., and has significant economic value and social benefits. Description of the Drawings

[0017] Figure 1 It is the infrared absorption spectrum of poly(N-isopropylacrylamide) used in the examples.

[0018] Figure 2 It is the infrared absorption spectrum of aldehyde-modified hyaluronic acid used in the examples.

[0019] Figure 3 It is the infrared absorption spectrum of gallic acid-grafted chitosan used in the examples.

[0020] Figure 4 It is the morphology diagram of the thermosensitive reversible phase transition hydrogel prepared in Example 1 at 18 °C (A), when heated to 37 °C (B), and when cooled to 18 °C again (C).

[0021] Figure 5Scanning electron microscope images of the freeze-dried thermosensitive reversible phase change hydrogel (A) and poly(N-isopropylacrylamide) hydrogel (B) prepared in Example 1. Detailed implementation mode

[0022] A thermosensitive reversible phase change hydrogel with high humidity adhesion is prepared as follows: 1) Add 6 - 10 g of poly(N-isopropylacrylamide) to 25 - 60 mL of deionized water and mechanically stir at room temperature for 30 - 60 min to obtain a poly(N-isopropylacrylamide) solution; 2) Add 0.05 - 0.15 g of aldehyde-modified hyaluronic acid to 2 - 12 mL of deionized water and mechanically stir at room temperature for 30 - 60 min to obtain an aldehyde-modified hyaluronic acid solution; 3) Add 0.05 - 0.3 g of gallic acid-grafted chitosan to 2 - 20 mL of deionized water and mechanically stir at room temperature for 30 - 60 min to obtain a gallic acid-grafted chitosan solution; 4) Add the aldehyde-modified hyaluronic acid solution and gallic acid-grafted chitosan solution prepared in steps 2) and 3) to the poly(N-isopropylacrylamide) solution prepared in step 1), and mechanically stir at 0 - 10 °C for 1 - 2 h to obtain a thermosensitive reversible phase change hydrogel.

[0023] Among them, the degree of polymerization of the aldehyde-modified hyaluronic acid used is 500 - 1000, and the degree of oxidation is 5% - 20%. The degree of polymerization of the gallic acid-grafted chitosan used is 10000 - 20000, and the grafting rate of gallic acid is 6% - 12%.

[0024] To make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific implementation modes, but the present invention is not limited thereto.

[0025] The poly(N-isopropylacrylamide) used in the examples was prepared according to the published patent 2023114239962, and its infrared absorption spectrum is shown in Figure 1 . As Figure 1 shown, the absorption peaks at 3400 cm -1 and 3271 cm -1 are the stretching vibration absorption peaks of the N-H bond, and the absorption peaks at 2970 cm -1 and 2930 cm -1 are the stretching vibration absorption peaks of the C-H bond. The absorption peaks at 1639 cm -1 and 1543 cm -1 are the C=O absorption peak and N-H bending vibration absorption peak of the amide group respectively. The absorption peaks at 1386 cm -1 and 1367 cm -1The absorption peak at [specific position] is the absorption peak formed by the symmetric deformation vibration coupling splitting of the dimethyl group on the isopropyl group, proving that poly(N-isopropylacrylamide) was successfully synthesized.

[0026] The aldehyde-functionalized hyaluronic acid used in the examples was prepared according to the literature (Que Bai, Qian Gao, Fangfang Hu, Caiyun Zheng, Wenting Chen, Na Sun, Jinxi Liu, Yanni Zhang, Xianglong Wu, Tingli Lu; Chitosan and hyaluronic-based hydrogels could promote the infected wound healing, International Journal of Biological Macromolecules, 2023, 232: 123271). Its infrared absorption spectrum is shown in Figure 2 . As Figure 2 shown, compared with the infrared absorption spectrum of hyaluronic acid, the infrared absorption spectrum of aldehyde-functionalized hyaluronic acid shows a characteristic absorption peak of C=O at [specific wavenumber] cm -1 , proving that aldehyde-functionalized hyaluronic acid was successfully synthesized.

[0027] The gallic acid-grafted chitosan used in the examples was prepared according to the literature (Kai Chen, Zihan Wu, Yutong Liu, Yuan Yuan, Changsheng Liu; Injectable double-crosslinked adhesive hydrogels with high mechanical resilience and effective energy dissipation for joint wound treatment, Advanced Functional Materials. 2022, 32, 2109687). Its infrared absorption spectrum is shown in Figure 3 . As Figure 3 shown, compared with the infrared absorption spectrum of chitosan, the gallic acid-grafted chitosan shows an absorption peak of the stretching vibration of the C=C skeleton of the gallic acid aromatic ring at [specific wavenumber] cm -1 , and the intensity of the N-H bending vibration absorption peak of chitosan at [specific wavenumber] cm -1 weakens, proving that gallic acid-grafted chitosan was successfully synthesized.

[0028] Example 1 First, 8 g of poly(N-isopropylacrylamide) was placed in 40 mL of deionized water and mechanically stirred at room temperature for 45 min to prepare a poly(N-isopropylacrylamide) solution. Then, 0.1 g of aldehyde-functionalized hyaluronic acid with a degree of polymerization of 800 and an oxidation degree of 12% was placed in 8 mL of deionized water and mechanically stirred at room temperature for 45 min to prepare an aldehyde-functionalized hyaluronic acid solution. Next, 0.2 g of gallic acid-grafted chitosan with a degree of polymerization of 15000 and a grafting rate of 9% was placed in 16 mL of deionized water and mechanically stirred at room temperature for 45 min to prepare a gallic acid-grafted chitosan solution. Finally, the obtained aldehyde-functionalized hyaluronic acid solution and gallic acid-grafted chitosan solution were added to the poly(N-isopropylacrylamide) solution, and the mixture was mechanically stirred at 5 °C for 1.5 h to prepare a highly humidity-adhesive thermosensitive reversible phase-change hydrogel.

[0029] Figure 4 The morphology diagrams of the thermosensitive reversible phase-change hydrogel prepared in this example at 18 °C (A), when heated to 37 °C (B), and when cooled to 18 °C again (C) are shown. As can be seen, the hydrogel is yellow and liquid at 18 °C, turns into white solid when heated to 37 °C, and turns back into yellow liquid when cooled to 18 °C again, indicating that the obtained hydrogel has excellent thermosensitive phase-change reversibility.

[0030] Figure 5 The freeze-dried scanning electron microscope images of the thermosensitive reversible phase-change hydrogel (A) and poly(N-isopropylacrylamide) hydrogel (B) prepared in this example are shown. As can be seen, compared with the hydrogel prepared from pure poly(N-isopropylacrylamide), the hydrogel prepared in this example has a more uniform porous structure, indicating that the long molecular chains of chitosan and hyaluronic acid can be tightly entangled with the poly(N-isopropylacrylamide) molecular chains through hydrogen bonding and dynamic covalent bonding to form a stable and uniform cross-linked network structure.

[0031] Example 2 First, 6 g of poly(N-isopropylacrylamide) was placed in 25 mL of deionized water and mechanically stirred at room temperature for 30 min to prepare a poly(N-isopropylacrylamide) solution. Then, 0.05 g of aldehyde-functionalized hyaluronic acid with a degree of polymerization of 500 and an oxidation degree of 5% was placed in 2 mL of deionized water and mechanically stirred at room temperature for 30 min to prepare an aldehyde-functionalized hyaluronic acid solution. Next, 0.05 g of gallic acid-grafted chitosan with a degree of polymerization of 10000 and a grafting rate of 6% was placed in 2 mL of deionized water and mechanically stirred at room temperature for 30 min to prepare a gallic acid-grafted chitosan solution. Finally, the obtained aldehyde-functionalized hyaluronic acid solution and gallic acid-grafted chitosan solution were added to the poly(N-isopropylacrylamide) solution, and the mixture was mechanically stirred at 0 °C for 1 h to prepare a highly humidity-adhesive thermosensitive reversible phase-change hydrogel.

[0032] Example 3 First, 10 g of poly(N-isopropylacrylamide) was placed in 60 mL of deionized water and mechanically stirred at room temperature for 60 min to obtain a poly(N-isopropylacrylamide) solution. Then, 0.15 g of aldehyde-functionalized hyaluronic acid with a polymerization degree of 1000 and an oxidation degree of 20% was placed in 12 mL of deionized water and mechanically stirred at room temperature for 60 min to obtain an aldehyde-functionalized hyaluronic acid solution. Next, 0.3 g of gallic acid-grafted chitosan with a polymerization degree of 20000 and a grafting rate of 12% was placed in 20 mL of deionized water and mechanically stirred at room temperature for 60 min to obtain a gallic acid-grafted chitosan solution. Finally, the obtained aldehyde-functionalized hyaluronic acid solution and gallic acid-grafted chitosan solution were added to the poly(N-isopropylacrylamide) solution, and the mixture was mechanically stirred at 10 °C for 2 h to obtain a thermosensitive reversible phase-change hydrogel with high humidity adhesion.

[0033] Comparative Example 1 First, 8 g of poly(N-isopropylacrylamide) was placed in 40 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a poly(N-isopropylacrylamide) solution. Then, 0.1 g of aldehyde-functionalized hyaluronic acid with a polymerization degree of 800 and an oxidation degree of 12% was placed in 8 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain an aldehyde-functionalized hyaluronic acid solution. Finally, the obtained aldehyde-functionalized hyaluronic acid solution was added to the poly(N-isopropylacrylamide) solution, and the mixture was mechanically stirred at 5 °C for 1.5 h to obtain the finished product.

[0034] Comparative Example 2 First, 8 g of poly(N-isopropylacrylamide) was placed in 40 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a poly(N-isopropylacrylamide) solution. Then, 0.2 g of gallic acid-grafted chitosan with a polymerization degree of 15000 and a grafting rate of 9% was placed in 16 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a gallic acid-grafted chitosan solution. Finally, the obtained gallic acid-grafted chitosan solution was added to the poly(N-isopropylacrylamide) solution, and the mixture was mechanically stirred at 5 °C for 1.5 h to obtain the finished product.

[0035] Comparative Example 3 First, 8 g of poly(N-isopropylacrylamide) was placed in 40 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a poly(N-isopropylacrylamide) solution. Then, 0.1 g of aldehyde-functionalized hyaluronic acid with a degree of polymerization of 800 and an oxidation degree of 12% was placed in 8 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain an aldehyde-functionalized hyaluronic acid solution. Next, 0.2 g of chitosan with a degree of polymerization of 15000 was placed in 16 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a chitosan solution. Finally, the obtained aldehyde-functionalized hyaluronic acid solution and chitosan solution were added to the poly(N-isopropylacrylamide) solution, and the mixture was mechanically stirred at 5 °C for 1.5 h to obtain the finished product.

[0036] Comparative Example 4 First, 8 g of poly(N-isopropylacrylamide) was placed in 40 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a poly(N-isopropylacrylamide) solution. Then, 0.1 g of hyaluronic acid with a degree of polymerization of 800 was placed in 8 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a hyaluronic acid solution. Next, 0.2 g of gallic acid-grafted chitosan with a degree of polymerization of 15000 and a grafting rate of 9% was placed in 16 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a gallic acid-grafted chitosan solution. Finally, the obtained hyaluronic acid solution and gallic acid-grafted chitosan solution were added to the poly(N-isopropylacrylamide) solution, and the mixture was mechanically stirred at 5 °C for 1.5 h to obtain the finished product.

[0037] Comparative Example 5 First, 8 g of poly(N-isopropylacrylamide) was placed in 40 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a poly(N-isopropylacrylamide) solution. Then, 0.1 g of hyaluronic acid with a degree of polymerization of 800 was placed in 8 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a hyaluronic acid solution. Next, 0.2 g of chitosan with a degree of polymerization of 15000 was placed in 16 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a chitosan solution. Finally, the obtained hyaluronic acid solution and chitosan solution were added to the poly(N-isopropylacrylamide) solution, and the mixture was mechanically stirred at 5 °C for 1.5 h to obtain the finished product.

[0038] Comparative Example 6 First, 8 g of poly(N-isopropylacrylamide) was placed in 40 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a poly(N-isopropylacrylamide) solution. Then, 0.1 g of aldehyde-functionalized hyaluronic acid with a degree of polymerization of 800 and an oxidation degree of 12% was placed in 8 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain an aldehyde-functionalized hyaluronic acid solution. Next, 0.2 g of gallic acid-grafted chitosan with a degree of polymerization of 8000 and a grafting rate of 4% was placed in 16 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a gallic acid-grafted chitosan solution. Finally, the obtained aldehyde-functionalized hyaluronic acid solution and gallic acid-grafted chitosan solution were added to the poly(N-isopropylacrylamide) solution, and the mixture was mechanically stirred at 5 °C for 1.5 h to obtain the finished product.

[0039] Comparative Example 7 First, 8 g of poly(N-isopropylacrylamide) was placed in 40 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a poly(N-isopropylacrylamide) solution. Then, 0.1 g of aldehyde-functionalized hyaluronic acid with a degree of polymerization of 800 and an oxidation degree of 12% was placed in 8 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain an aldehyde-functionalized hyaluronic acid solution. Next, 0.2 g of gallic acid-grafted chitosan with a degree of polymerization of 22000 and a grafting rate of 15% was placed in 16 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a gallic acid-grafted chitosan solution. Finally, the obtained aldehyde-functionalized hyaluronic acid solution and gallic acid-grafted chitosan solution were added to the poly(N-isopropylacrylamide) solution, and the mixture was mechanically stirred at 5 °C for 1.5 h to obtain the finished product.

[0040] Comparative Example 8 First, 0.1 g of aldehyde-functionalized hyaluronic acid with a degree of polymerization of 800 and an oxidation degree of 12% was placed in 8 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain an aldehyde-functionalized hyaluronic acid solution. Next, 0.2 g of gallic acid-grafted chitosan with a degree of polymerization of 15000 and a grafting rate of 9% was placed in 16 mL of deionized water and mechanically stirred at room temperature for 45 min to obtain a gallic acid-grafted chitosan solution. Finally, the obtained aldehyde-functionalized hyaluronic acid solution was added to the gallic acid-grafted chitosan solution, and the mixture was mechanically stirred at 5 °C for 1.5 h to obtain the finished product.

[0041] The hydrogels prepared in the examples and comparative examples were subjected to the following performance tests: 1) The storage modulus, loss modulus, and complex viscosity during the heating process were measured using a rotational rheometer. At the same time, as the test temperature increased, when the storage modulus of the hydrogel was greater than the loss modulus, a phase transition occurred, and the temperature at this time was defined as the phase transition temperature.

[0042] 2) Leave the solid hydrogel to stand still at 18 °C for 1 h. When the solid hydrogel reverts to the liquid hydrogel, it is determined that the hydrogel has reversible phase transition.

[0043] 3) Inject the prepared liquid hydrogel onto the surface of porcine skin that has been soaked in PBS buffer solution with a pH value of 7.4 and a temperature of 37 °C. The time taken for the hydrogel to change from being fluid to non-fluid is defined as the phase transition time of the hydrogel.

[0044] 4) Inject the prepared liquid hydrogel onto the surface of porcine skin that has been soaked in PBS buffer solution with a pH value of 7.4, and quickly place it into PBS buffer solution at 37 °C. Stir the PBS buffer solution at a rotational speed of 800 revolutions per minute. At this time, the porcine skin with the hydrogel attached to its surface rotates together with the PBS buffer solution until the hydrogel detaches from the porcine skin surface. Record the time the hydrogel adheres to the porcine skin surface to characterize the wet adhesion performance of the hydrogel.

[0045] 5) First, soak the porcine skin in PBS buffer solution with a pH value of 7.4, then make a 1-cm long incision on the wet porcine skin surface. After that, precisely inject the liquid hydrogel into the incision area to ensure it completely covers the incision area. After the hydrogel completes the phase transition at 37 °C, test the bursting pressure of the hydrogel by continuously inflating the porcine skin to characterize the wet adhesion performance of the hydrogel.

[0046] The performance test results are shown in Table 1.

[0047] Table 1 Performance test results

[0048] As can be seen from the results in Table 1, in the examples, poly(N-isopropylacrylamide) was used as the matrix, and aldehyde-functionalized hyaluronic acid and gallic acid-grafted chitosan were used as the reinforcing agent and tackifier. Through mechanical stirring, a hydrogel with high strength, excellent wet adhesion, biocompatibility, thermosensitive phase transition property and thermosensitive phase transition reversibility, and a fast phase transition response rate can be prepared. In contrast, in Comparative Examples 1 and 2, adding aldehyde-functionalized hyaluronic acid or gallic acid-grafted chitosan alone could not prepare a thermosensitive reversible phase transition hydrogel. In Comparative Examples 3 and 4, although the prepared products using chitosan instead of gallic acid-grafted chitosan or using hyaluronic acid instead of aldehyde-functionalized hyaluronic acid had thermosensitive phase transition reversibility, their gel strength was low and their wet adhesion was poor. In Comparative Example 5, although the prepared product using chitosan and hyaluronic acid to replace gallic acid-grafted chitosan and aldehyde-functionalized hyaluronic acid respectively had thermosensitive phase transition reversibility, its gel strength was even lower and its wet adhesion was even worse. In Comparative Example 6, although the prepared product using gallic acid-grafted chitosan with a low grafting rate had thermosensitive phase transition reversibility, its gel strength was relatively low and its wet adhesion was relatively poor. In Comparative Example 7, the prepared product using gallic acid-grafted chitosan with a high grafting rate had a serious phase separation phenomenon due to the large internal force among the components, so it did not have thermosensitive phase transition property. In Comparative Example 8, the prepared product obtained by Schiff base reaction of the amino group of chitosan and the aldehyde group of aldehyde-functionalized hyaluronic acid was a white solid hydrogel and did not have thermosensitive phase transition property.

[0049] The above are only the preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A method for preparing a thermosensitive reversible phase change hydrogel with high wet adhesion, characterized in that: The hydrogel is prepared by mechanical stirring with poly N-isopropylacrylamide as a matrix, aldehyde-modified hyaluronic acid and gallic acid grafted chitosan as reinforcing agents and thickeners.

2. The preparation method according to claim 1, characterized in that: The degree of polymerization of the aldehyde-modified hyaluronic acid is 500-1000, and the degree of oxidation is 5%-20%.

3. The preparation method according to claim 1, characterized in that: The polymerization degree of the gallic acid grafted chitosan is 10000-20000, wherein the grafting rate of gallic acid is 6%-12%.

4. The preparation method according to claim 1, characterized in that: The steps include: 1) Add poly (N-isopropylacrylamide) into deionized water and mechanically stir at room temperature for 30-60 min to prepare a poly (N-isopropylacrylamide) solution; 2) Adding aldehyde-modified hyaluronic acid into deionized water, and mechanically stirring at room temperature for 30 to 60 minutes to prepare aldehyde-modified hyaluronic acid solution; 3) Add gallic acid grafted chitosan into deionized water and mechanically stir at room temperature for 30-60 min to prepare a gallic acid grafted chitosan solution; 4) adding the aldehyde-modified hyaluronic acid solution and the gallic acid grafted chitosan solution prepared in steps 2) and 3) to the poly (N-isopropylacrylamide) solution prepared in step 1), and mechanically stirring at 0-10°C for 1-2 h to obtain the thermosensitive reversible phase change hydrogel.

5. The preparation method according to claim 4, characterized in that: The concentration of the poly (N-isopropylacrylamide) solution obtained in step 1) is 0.1-0.4 g / mL.

6. The preparation method according to claim 4, characterized in that: Step 2) The concentration of the aldehyde-modified hyaluronic acid solution obtained is 4-75 mg / mL.

7. The preparation method according to claim 4, characterized in that: Step 3) The concentration of the obtained gallic acid grafted chitosan solution is 7.5-150 mg / mL.

8. The preparation method according to claim 4, characterized in that: The volume ratio of the aldehyde-modified hyaluronic acid solution, the gallic acid grafted chitosan solution and the poly (N-isopropylacrylamide) solution used in step 4) is 1:(1-1.6):(2-30).

9. A thermosensitive reversible phase-change hydrogel with high wet adhesion prepared by the method according to any one of claims 1 to 8.

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