PH-responsive hydrogel as well as preparation method and application thereof

Abstract

The invention relates to the technical field of biological medicines, in particular to pH-responsive hydrogel as well as a preparation method and application thereof. The hydrogel is prepared from the following raw materials: a modified chitosan aqueous solution, a modified polyethylene glycol aqueous solution, a polyvinyl alcohol aqueous solution and dopamine hydrochloride. The hydrogel is prepared by compounding a methacrylic anhydride modified chitosan aqueous solution, an aldehyde-terminated polyethylene glycol aqueous solution, a polyvinyl alcohol aqueous solution and dopamine hydrochloride, and the hydrogel with the pH response characteristic can be prepared and has reliable mechanical supporting strength; and the drug-resistant drugs (such as diclofenac sodium) can be effectively adsorbed, and a slow release effect is generated, so that the treatment of IVD is fundamentally realized.

Description

Technical Field

[0001] This invention relates to the field of biomedical technology, and in particular to a pH-responsive hydrogel, its preparation method, and its applications. Background Technology

[0002] Lumbar disc herniation (LDH) is a very common clinical disease. Its persistent and recurring nature severely impacts people's quality of life. In reality, many patients diagnosed with LDH often lack scientific understanding of the disease and fall into the trap of blindly pursuing treatment, which can lead to lifelong regret. Therefore, correctly understanding LDH and adopting the most suitable treatment method is key to a cure. There are many treatment methods for LDH, including traction therapy, physical therapy (such as physiotherapy, massage), nerve blocks, acupuncture and knife therapy, surgical treatments (conventional open surgery, endoscopic discectomy, percutaneous aspiration, collagenase chemonucleolysis), ozone injection therapy, and traditional Chinese medicine hot compress therapy. Although there are many existing treatment methods for LDH, most can only alleviate clinical symptoms to a certain extent, such as reducing pain and improving mobility limitations, but cannot fundamentally eliminate the cause and achieve a complete cure.

[0003] The intervertebral disc (IVD) is mainly composed of three parts: the nucleus pulposus (NP) rich in proteoglycans, the annulus fibrosus (AF) rich in collagen, and the cartilaginous endplate (CEP). The IVD exhibits age-dependent degenerative characteristics, and this degenerative process intensifies with age after age 30. Furthermore, with rapid economic and technological development, prolonged sitting and long hours of desk work have become the norm for many professionals, placing additional pressure and damage on the intervertebral discs due to poor posture and lifestyle habits. Consequently, the age of onset for intervertebral disc-related diseases is gradually decreasing; disc lesions that were previously more common in middle-aged and elderly individuals are now increasingly prevalent in younger populations. Simultaneously, the incidence rate continues to rise, severely impacting patients' physical and mental health and quality of life.

[0004] Because intervertebral discs are mostly isolated from the external environment, there are no blood vessels, nerves, or other components in the internal aponeurotic fossa (AF) and intervertebral disc nuclei (NP). Nutrients and oxygen mainly diffuse from the cervical intervertebral disc (CEP) and AF. However, adverse factors such as trauma and oxidative stress cause structural and functional disorders of the CEP, disrupting the energy supply of the NP tissue. In severe cases, this can lead to mitochondrial imbalance. The NP tissue, isolated from the external environment for a long time, gradually undergoes pathological activities such as aging, apoptosis, and pyroptosis. Acidic metabolic byproducts gradually accumulate within the tissue, and water content decreases; the load-bearing capacity of the intervertebral disc (IVD) gradually declines. Based on these factors, the degeneration of the three components of the IVD reinforces each other, accelerating the degeneration process. Therefore, in-depth investigation and resolution of the root causes of intervertebral disc degeneration is a fundamental and effective principle and method for treating intervertebral disc-related diseases.

[0005] Chinese invention patent application CN117100900A discloses a breathable hydrogel-based composite dressing with reversible adhesion function and its preparation method. By designing a breathable hydrogel-based composite dressing with reversible adhesion function, it solves the problems of poor breathability and uncontrollable adhesion of traditional dressings, achieving higher breathability and adhesion control. Chinese invention patent application CN119875162A discloses a polyvinyl alcohol hydrogel reinforced with oriented degummed filaments, its preparation method, and its application. By introducing oriented degummed filaments into the polyvinyl alcohol hydrogel and using a hot annealing process, it solves the problem of insufficient mechanical properties of traditional hydrogel materials, achieving improved mechanical properties of intervertebral disc repair materials. However, these existing technologies do not solve the aforementioned technical problems; they can only alleviate lumbar disc herniation symptoms to a certain extent and cannot cure lumbar disc herniation.

[0006] Against this backdrop, it is imperative to research a gel material that can fundamentally treat IVD. Summary of the Invention

[0007] The pH value of normal intervertebral disc (NP) tissue is typically in the range of 7.0-7.2, while the pH value of severely degenerated NP tissue can drop to 5.5-5.6. The acidic microenvironment within NP tissue is a significant contributing factor to intracranial disc degeneration (IVD). The decrease in pH value within the degenerated intervertebral disc can act as a trigger, initiating the release of drugs that precisely inhibit IVD. Against this backdrop, the development of a pH-responsive hydrogel capable of timely and precise drug release within the patient's body could fundamentally achieve the treatment of IVD.

[0008] The first aspect of the present invention provides a pH-responsive hydrogel, wherein the raw materials for preparing the hydrogel include: modified chitosan, modified polyethylene glycol, polyvinyl alcohol, dopamine hydrochloride and water.

[0009] Optionally, the raw materials for preparing the hydrogel include: modified chitosan aqueous solution, modified polyethylene glycol aqueous solution, polyvinyl alcohol aqueous solution, and dopamine hydrochloride.

[0010] Further optionally, the volume ratio of the modified chitosan aqueous solution, the modified polyethylene glycol aqueous solution, and the polyvinyl alcohol aqueous solution is (1-3):(1-2):(1-3).

[0011] Optionally, the modified chitosan aqueous solution includes a methacrylic anhydride-modified chitosan aqueous solution; further optionally, the preparation method of the methacrylic anhydride-modified chitosan is as follows: dissolving chitosan in an acid solution, adding a methacrylic anhydride aqueous solution and reacting for 10-15 hours, dialysis with deionized water, and lyophilizing to obtain water-soluble sponge-like methacrylic anhydride-modified chitosan.

[0012] In some embodiments, methacrylic anhydride-modified chitosan is dissolved in water to obtain an aqueous solution of methacrylic anhydride-modified chitosan for later use.

[0013] Optionally, the degree of deacetylation of the chitosan is >85%.

[0014] Optionally, the mass ratio of the methacrylic anhydride to chitosan is (0.4-1.2):1.

[0015] Optionally, the mass-to-volume ratio of methacrylic anhydride-modified chitosan to water in the methacrylic anhydride-modified chitosan aqueous solution is (0.005-0.05) g: 1 mL; more preferably, it is 0.02 g: 1 mL.

[0016] The acid solution may include an aqueous solution of at least one of acetic acid, citric acid, malic acid, and alginic acid; an aqueous solution of acetic acid may be selected.

[0017] In some embodiments, the concentration of acetic acid in the aqueous acetic acid solution is 0.01-2%.

[0018] Optionally, the modified polyethylene glycol is aldehyde-terminated polyethylene glycol, and the mass-to-volume ratio of aldehyde-terminated polyethylene glycol to water in the modified polyethylene glycol aqueous solution is (0.05-0.3) g: 1 mL; more preferably, it is 0.2 g: 1 mL.

[0019] This invention utilizes methacrylic anhydride-modified chitosan and aldehyde-terminated polyethylene glycol to prepare a pH-responsive hydrogel. Further addition of a specific amount of polyvinyl alcohol effectively enhances the mechanical properties of the hydrogel. The molecular structures of methacrylic anhydride-modified chitosan and aldehyde-terminated polyethylene glycol contain numerous hydroxyl groups, which can crosslink with polyvinyl alcohol through hydrogen bonds, thereby constructing a stable three-dimensional network. This effectively improves the mechanical strength of the hydrogel, enhancing its stress-bearing capacity and providing reliable mechanical support.

[0020] Optionally, the mass-to-volume ratio of polyvinyl alcohol to water in the polyvinyl alcohol aqueous solution is (0.05-0.2) g: 1 mL; more preferably, it is 0.15 g: 1 mL.

[0021] Optionally, the mass ratio of dopamine hydrochloride to polyvinyl alcohol is 1:(4-10); more preferably, it is 1:7.5. This invention introduces a specific amount of dopamine hydrochloride into the hydrogel system, which can endow the hydrogel with better mechanical properties and biocompatibility. During application, the hydrogel can improve cell survival rate and cell adhesion, thereby enhancing the therapeutic effect.

[0022] A second aspect of the present invention provides an application of a pH-responsive hydrogel; the method for preparing the hydrogel includes:

[0023] S1. Prepare modified chitosan and prepare modified chitosan aqueous solution;

[0024] S2. Prepare a modified polyethylene glycol aqueous solution;

[0025] S3 prepares an aqueous solution of polyvinyl alcohol containing dopamine hydrochloride;

[0026] S4. Mix the modified chitosan aqueous solution, the modified polyethylene glycol aqueous solution, and the polyvinyl alcohol aqueous solution containing dopamine hydrochloride evenly to obtain a hydrogel.

[0027] The gelation time of the hydrogel in step S4 is 20-60 seconds.

[0028] A third aspect of this invention provides an application of a pH-responsive hydrogel; the hydrogel is used in the preparation of an intervertebral disc repair material; the raw materials for preparing the intervertebral disc repair material include the hydrogel and a drug. The preparation method of the repair material includes: adsorbing the drug onto the hydrogel to obtain the finished hydrogel product.

[0029] In some embodiments, the adsorption time is 3-24 hours; examples include 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, 21 hours, 22 hours, 23 hours, and 24 hours.

[0030] In some embodiments, the drug is selected as an anti-inflammatory drug, including, for example, diclofenac sodium, latonicin, salicylaldehyde, tannic acid, resveratrol, mannitol, dexamethasone, celecoxib, loxoprofen sodium, meloxicam, prednisolone acetate, methylprednisolone, etc. Optionally, the drug includes one or more combinations of diclofenac sodium, latonicin, salicylaldehyde, tannic acid, and resveratrol; more preferably, the drug is diclofenac sodium.

[0031] The hydrogel prepared in this invention can load drugs into the body and then release them through sustained-release action, thereby fundamentally achieving the therapeutic goal; a further preferred drug is diclofenac sodium. The addition of the anti-inflammatory drug diclofenac sodium and its combination with the hydrogel forms a favorable synergistic mechanism. Under the synergistic effect of the hydrogel, this drug can more effectively reduce NP cell apoptosis and significantly promote autophagy. Simultaneously, it has a positive impact on the conditions of NP cells, achieving the dual goals of anti-oxidation and extracellular matrix (ECM) regulation, thus obtaining ideal IVD therapeutic effects.

[0032] Beneficial effects:

[0033] This invention provides a pH-responsive hydrogel, its preparation method, and its applications, which have the following advantages:

[0034] (1) The present invention uses modified chitosan aqueous solution, modified polyethylene glycol aqueous solution, polyvinyl alcohol aqueous solution and dopamine hydrochloride to prepare hydrogel. In particular, methacrylic anhydride is preferred to modify chitosan, which can produce hydrogel with pH responsive characteristics, providing reliable technical support for the fundamental realization of IVD treatment.

[0035] (2) The present invention further preferably uses aldehyde-terminated polyethylene glycol as modified polyethylene glycol and introduces polyvinyl alcohol as a preparation raw material, which can effectively improve the mechanical strength of hydrogel, thereby enhancing the stress bearing capacity of hydrogel and providing mechanical support.

[0036] (3) The present invention further optimizes the concentration and ratio of specific methacrylic anhydride modified chitosan aqueous solution, aldehyde-terminated polyethylene glycol aqueous solution, polyvinyl alcohol aqueous solution and dopamine hydrochloride. The resulting hydrogel not only has high compressive strength, but also has a simple processing and preparation process and good dimensional stability, and can be well applied to the preparation of intervertebral disc repair materials.

[0037] (4) The hydrogel prepared by the present invention has excellent adsorption and sustained release effects. It can adsorb a large number of drug molecules in just 3 hours and can continuously release drug molecules under different pH conditions, which is of positive significance for the treatment of IVD.

[0038] (5) The present invention further prefers diclofenac sodium as the drug molecule, which has good compatibility with hydrogel and can effectively reduce inflammation. Under the action of the hydrogel as a carrier, it can achieve the dual therapeutic goals of antioxidant defense and ECM dynamic regulation.

[0039] (6) The raw materials of this invention are safe and environmentally friendly, non-toxic and harmless, and have good degradation stability. They are suitable for widespread application in the field of intervertebral disc treatment and have high application value. Attached Figure Description

[0040] Figure 1Images of the hydrogels prepared in Examples 6, 7, 15, and 16 (from left to right: Examples 6, 7, 15, and 16).

[0041] Figure 2 The in vitro sustained-release curve of Example 1;

[0042] Figure 3 The in vitro sustained-release curve of Example 2 is used. Detailed Implementation

[0043] The following is some information about the raw materials used in the embodiments of the present invention.

[0044] Chitosan: Deacetylation degree > 85%, derived from Adamas.

[0045] Modified polyethylene glycol (specifically aldehyde-terminated polyethylene glycol): sourced from Xiamen Sainuobang Biotechnology Co., Ltd.

[0046] Polyvinyl alcohol: sourced from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0047] Furthermore, the room temperature in this invention is 25°C, and all raw materials, equipment, and other consumables used are commercially available.

[0048] Example 1

[0049] This embodiment provides a pH-responsive hydrogel and its preparation method.

[0050] The raw materials for preparing the hydrogel include: methacrylic anhydride-modified chitosan aqueous solution and aldehyde-terminated polyethylene glycol aqueous solution.

[0051] The preparation steps of the hydrogel include:

[0052] S1. Prepare methacrylic anhydride-modified chitosan and prepare an aqueous solution of methacrylic anhydride-modified chitosan; specifically: weigh 0.2 g of chitosan and dissolve it in 100 mL of 1% acetic acid aqueous solution, add methacrylic anhydride aqueous solution (0.155 g of methacrylic anhydride dissolved in 2 mL of water), react at room temperature for 12 h, dialyze with deionized water for 3 days, and freeze dry to obtain water-soluble spongy methacrylic anhydride-modified chitosan; weigh 0.02 g of methacrylic anhydride-modified chitosan and dissolve it in 1 mL of ultrapure water to obtain an aqueous solution of methacrylic anhydride-modified chitosan for later use.

[0053] S2. Prepare modified polyethylene glycol aqueous solution (aldehyde-terminated polyethylene glycol aqueous solution); Specifically: Weigh 0.2g of aldehyde-terminated polyethylene glycol and dissolve it in 1mL of ultrapure water to obtain aldehyde-terminated polyethylene glycol aqueous solution for later use.

[0054] S3. Mix 1 mL of methacrylic anhydride-modified chitosan aqueous solution and 1 mL of aldehyde-terminated polyethylene glycol aqueous solution evenly, let stand for 20 s, and obtain a uniform hydrogel product.

[0055] Example 2

[0056] This embodiment provides a pH-responsive hydrogel and its preparation method.

[0057] The raw materials for preparing the hydrogel include: methacrylic anhydride-modified chitosan aqueous solution, aldehyde-terminated polyethylene glycol aqueous solution, and polyvinyl alcohol aqueous solution.

[0058] The preparation steps of the hydrogel include:

[0059] S1. Prepare methacrylic anhydride-modified chitosan and prepare an aqueous solution of methacrylic anhydride-modified chitosan; specifically: weigh 0.2 g of chitosan and dissolve it in 100 mL of 1% acetic acid aqueous solution, add methacrylic anhydride aqueous solution (0.155 g of methacrylic anhydride dissolved in 2 mL of water), react at room temperature for 12 h, dialyze with deionized water for 3 days, and freeze dry to obtain water-soluble spongy methacrylic anhydride-modified chitosan; weigh 0.02 g of methacrylic anhydride-modified chitosan and dissolve it in 1 mL of ultrapure water to obtain an aqueous solution of methacrylic anhydride-modified chitosan for later use.

[0060] S2. Prepare modified polyethylene glycol aqueous solution (aldehyde-terminated polyethylene glycol aqueous solution); Specifically: Weigh 0.2g of aldehyde-terminated polyethylene glycol and dissolve it in 1mL of ultrapure water to obtain aldehyde-terminated polyethylene glycol aqueous solution for later use.

[0061] S3. Prepare a polyvinyl alcohol aqueous solution: Weigh 0.15g of polyvinyl alcohol and dissolve it in 1mL of ultrapure water for later use.

[0062] S4. Mix 1 mL of methacrylic anhydride-modified chitosan aqueous solution, 1 mL of aldehyde-terminated polyethylene glycol aqueous solution and 1 mL of polyvinyl alcohol aqueous solution evenly, let stand for 40 s, and obtain a uniform hydrogel product.

[0063] Example 3

[0064] This embodiment provides a pH-responsive hydrogel and its preparation method.

[0065] The raw materials for preparing the hydrogel include: methacrylic anhydride-modified chitosan aqueous solution, aldehyde-terminated polyethylene glycol aqueous solution, polyvinyl alcohol aqueous solution, and dopamine hydrochloride.

[0066] The preparation steps of the hydrogel include:

[0067] S1. Prepare methacrylic anhydride-modified chitosan and prepare an aqueous solution of methacrylic anhydride-modified chitosan; specifically: weigh 0.2 g of chitosan and dissolve it in 100 mL of 1% acetic acid aqueous solution, add methacrylic anhydride aqueous solution (0.155 g of methacrylic anhydride dissolved in 2 mL of water), react at room temperature for 12 h, dialyze with deionized water for 3 days, and freeze dry to obtain water-soluble spongy methacrylic anhydride-modified chitosan; weigh 0.02 g of methacrylic anhydride-modified chitosan and dissolve it in 1 mL of ultrapure water to obtain an aqueous solution of methacrylic anhydride-modified chitosan for later use.

[0068] S2. Prepare modified polyethylene glycol aqueous solution (aldehyde-terminated polyethylene glycol aqueous solution); Specifically: Weigh 0.2g of aldehyde-terminated polyethylene glycol and dissolve it in 1mL of ultrapure water to obtain aldehyde-terminated polyethylene glycol aqueous solution for later use.

[0069] S3. Prepare an aqueous solution of polyvinyl alcohol containing dopamine hydrochloride; specifically: weigh 0.02 g of dopamine hydrochloride and 0.15 g of polyvinyl alcohol and dissolve them in 1 mL of ultrapure water for later use.

[0070] S4. Mix 1 mL of methacrylic anhydride-modified chitosan aqueous solution, 1 mL of aldehyde-terminated polyethylene glycol aqueous solution, and 1 mL of polyvinyl alcohol aqueous solution containing dopamine hydrochloride evenly, and let stand for 40 s to obtain a uniform hydrogel product.

[0071] Example 4

[0072] This embodiment provides a pH-responsive hydrogel and its preparation method. The specific implementation method is the same as in Embodiment 3, except for step S1. Specifically: S1. Prepare methacrylic anhydride-modified chitosan and prepare an aqueous solution of methacrylic anhydride-modified chitosan. Specifically: Weigh 0.5g of chitosan and dissolve it in 100mL of 1% acetic acid aqueous solution, add methacrylic anhydride aqueous solution (0.2g of methacrylic anhydride dissolved in 2mL of water), react at room temperature for 12h, dialyze with deionized water for 3 days, and freeze-dry to obtain water-soluble spongy methacrylic anhydride-modified chitosan; Weigh 0.02g of methacrylic anhydride-modified chitosan and dissolve it in 1mL of ultrapure water to obtain an aqueous solution of methacrylic anhydride-modified chitosan for later use.

[0073] Example 5

[0074] This embodiment provides a pH-responsive hydrogel and its preparation method. The specific implementation method is the same as in Embodiment 3, except for step S1. Specifically: S1. Prepare methacrylic anhydride-modified chitosan and prepare an aqueous solution of methacrylic anhydride-modified chitosan. Specifically: Weigh 0.5g of chitosan and dissolve it in 100mL of 1% acetic acid aqueous solution, add methacrylic anhydride aqueous solution (0.4g of methacrylic anhydride dissolved in 2mL of water), react at room temperature for 12h, dialyze with deionized water for 3 days, and freeze-dry to obtain water-soluble sponge-like methacrylic anhydride-modified chitosan; Weigh 0.02g of methacrylic anhydride-modified chitosan and dissolve it in 1mL of ultrapure water to obtain an aqueous solution of methacrylic anhydride-modified chitosan for later use.

[0075] Example 6

[0076] This embodiment provides a pH-responsive hydrogel and its preparation method. The specific implementation method is the same as in Embodiment 3, except for step S1; specifically:

[0077] S1. Prepare methacrylic anhydride-modified chitosan and prepare an aqueous solution of methacrylic anhydride-modified chitosan; specifically: weigh 0.5 g of chitosan and dissolve it in 100 mL of 1% acetic acid aqueous solution, add methacrylic anhydride aqueous solution (0.6 g of methacrylic anhydride dissolved in 2 mL of water), react at room temperature for 12 h, dialyze with deionized water for 3 days, and freeze dry to obtain water-soluble spongy methacrylic anhydride-modified chitosan; weigh 0.02 g of methacrylic anhydride-modified chitosan and dissolve it in 1 mL of ultrapure water to obtain an aqueous solution of methacrylic anhydride-modified chitosan for later use.

[0078] Comparative studies of the methacrylic anhydride-modified chitosan prepared in Examples 3-6 revealed that the mass ratio of methacrylic anhydride to chitosan affects the strength and morphology of the hydrogel. When the mass ratio of methacrylic anhydride to chitosan is less than 0.8, the final hydrogel has lower strength; while when too much methacrylic anhydride is added, the material is difficult to dialysis, easily produces toxic substances, and is not suitable for use in hydrogels and repair materials.

[0079] Example 7

[0080] Example 7 provides a pH-responsive hydrogel and its preparation method. The specific implementation method is the same as that in Example 6, except that the concentration of aldehyde-terminated polyethylene glycol in the aqueous solution is different. Specifically, 0.1 g of aldehyde-terminated polyethylene glycol is dissolved in 1 mL of ultrapure water to obtain an aqueous solution of aldehyde-terminated polyethylene glycol.

[0081] Examples 8-16

[0082] Examples 8-16 provide a pH-responsive hydrogel and its preparation method. The specific implementation method is the same as that of Example 6, except that in step S4, the methacrylic anhydride modified chitosan aqueous solution, aldehyde-terminated polyethylene glycol aqueous solution and polyvinyl alcohol aqueous solution containing dopamine hydrochloride are mixed evenly according to a certain volume ratio (see Table 3 below) (the concentration of each solution remains unchanged and the volume is scaled up proportionally), and allowed to stand for 40s to obtain a uniform hydrogel product.

[0083] Table 3

[0084]

[0085] Application Example 1

[0086] Application Example 1 provides the application of a pH-responsive hydrogel and its preparation method in the preparation of intervertebral disc repair materials. The hydrogel is derived from Example 10, and the preparation method of the repair material includes:

[0087] The hydrogel product was placed in 10 mL of a 2 mg / mL diclofenac sodium aqueous solution and left for 3 hours to obtain the repair material.

[0088] Application Example 2

[0089] Application Example 2 provides an application of a pH-responsive hydrogel and its preparation method in the preparation of intervertebral disc repair materials. The hydrogel is derived from Example 10, and the preparation method of the repair material includes:

[0090] The hydrogel product was placed in 10 mL of a 2 mg / mL diclofenac sodium aqueous solution and left for 24 hours to obtain the repair material.

[0091] Performance testing

[0092] 1. Compression performance

[0093] A general-purpose mechanical testing instrument was used to conduct compression tests on the hydrogel samples (10 mm in diameter and 15 mm in height) prepared in Examples 1-16 at a speed of 10 mm / min. In the static compression test, each hydrogel sample was compressed to the maximum stress at which it would break. Three parallel samples were taken from each example for testing, and the average value of the test results was taken. The test results are recorded in Table 4.

[0094] 2. Swelling degree

[0095] Take samples from the examples and weigh them. Place each sample in a 50mL centrifuge tube and add 10 times the mass of the hydrogel of ultrapure water. Transfer the centrifuge tubes to a 37℃ constant temperature water bath for 1 hour. Then take them out and measure the water absorption of the samples. The test results are recorded in Table 4.

[0096] 3. Stability

[0097] Weigh 1g of the example sample and place it in a 15mL centrifuge tube containing 10mL PBS (phosphate buffer). Transfer the centrifuge tube to a water bath shaker at 37°C and observe the degradation of the hydrogel periodically. The test results after 2 months are recorded in Table 4.

[0098] 4. Sustained-release

[0099] Weigh 1g of each of the samples from Application Examples 1 and 2, and immerse them in 10mL of PBS solutions with pH values ​​of 5.0, 7.4, and 10.0, respectively. Transfer to a 37°C water bath shaker for incubation. Periodically collect 1mL of the supernatant, and measure the absorbance of each sample at 276nm using a UV spectrophotometer. Determine the diclofenac sodium content in each sample based on the diclofenac sodium standard curve to detect the diclofenac sodium release rate. Plot an in vitro release curve and calculate the cumulative release rate of diclofenac sodium. The test results are shown in [Figure number missing]. Figure 2 , 3 .

[0100] Table 4

[0101] Example Compressive strength / MPa Swelling rate / % stability Example 1 / / Hydrogel degradation Example 2 / / Hydrogel degradation Example 3 / / Hydrogel degradation Example 4 / / Hydrogel degradation Example 5 / / Hydrogel degradation Example 6 0.25 134 The hydrogel underwent significant degradation. Example 7 / 110 The hydrogel showed no significant changes and was almost undegraded. Example 8 0.11 / / Example 9 0.35 / / Example 10 0.15 / / Example 11 0.17 / / Example 12 0.22 / / Example 13 0.06 / / Example 14 0.29 / / Example 15 0.11 110 The hydrogel showed no significant changes and was almost undegraded. Example 16 0.13 110 The hydrogel showed no significant changes and was almost undegraded.

[0102] Table 4 shows that the compressive strength of the hydrogel changes to varying degrees when the concentrations of the methacrylic anhydride-modified chitosan aqueous solution, the aldehyde-terminated polyethylene glycol aqueous solution, and the polyvinyl alcohol aqueous solution containing dopamine hydrochloride are adjusted, or when the volume ratio of each raw material solution is adjusted. When the mass-volume concentrations of the methacrylic anhydride-modified chitosan aqueous solution, the aldehyde-terminated polyethylene glycol aqueous solution, or the polyvinyl alcohol are too low, the hydrogel is in poor condition, mainly exhibiting low strength and difficulty in molding. When the mass-volume concentration of the methacrylic anhydride-modified chitosan aqueous solution is >2% or the mass-volume concentration of the polyvinyl alcohol is greater than 20%, the hydrogel material is difficult to dissolve and cannot undergo subsequent reactions. When the volume ratio of the methacrylic anhydride-modified chitosan aqueous solution, the aldehyde-terminated polyethylene glycol aqueous solution, and the polyvinyl alcohol aqueous solution containing dopamine hydrochloride is 2:1:1, the hydrogel exhibits the highest compressive strength, reaching 0.35 MPa.

[0103] The test results in Table 4 also show that Example 6 has a high swelling rate and poor material stability. The hydrogel degrades significantly after 2 months of storage. In contrast, Examples 7, 15, and 16 have relatively low swelling rates, good dimensional stability of the hydrogel, and no significant change in shape after 2 months of storage, indicating strong degradation stability.

[0104] Figure 1 The images shown are actual pictures of the hydrogels prepared in Examples 6, 7, 15 and 16. Figure 2 , Figure 3The in vitro sustained-release curves for Examples 1 and 2 are shown. The in vitro sustained-release curves show that the release rate of the repair material (drug-loaded hydrogel) is slower under acidic conditions and faster under alkaline conditions. Under acidic conditions, the cumulative release rate of the hydrogel that adsorbed diclofenac sodium for 3 hours and 24 hours was approximately 50% after 2 days; under alkaline conditions, the cumulative release rate of the hydrogel that adsorbed diclofenac sodium for 3 hours and 24 hours was approximately 80% after 2 days. Furthermore, the results show that the hydrogel had essentially completed drug adsorption after 3 hours, and the sustained-release performance of the material was close to that of the material prepared after 24 hours of adsorption.

Claims

1. A pH-responsive hydrogel, characterized in that, The raw materials for preparing the hydrogel include: modified chitosan, modified polyethylene glycol, polyvinyl alcohol, dopamine hydrochloride, and water.

2. The hydrogel according to claim 1, characterized in that, The raw materials for preparing the hydrogel include: modified chitosan aqueous solution, modified polyethylene glycol aqueous solution, polyvinyl alcohol aqueous solution and dopamine hydrochloride; the volume ratio of the modified chitosan aqueous solution, modified polyethylene glycol aqueous solution and polyvinyl alcohol aqueous solution is (1-3):(1-2):(1-3).

3. The hydrogel according to claim 2, characterized in that, The modified chitosan aqueous solution includes a methacrylic anhydride-modified chitosan aqueous solution; the preparation method of the methacrylic anhydride-modified chitosan is as follows: dissolve chitosan in an acid solution, add a methacrylic anhydride aqueous solution and react for 10-15 hours, dialyze with deionized water, and freeze dry to obtain methacrylic anhydride-modified chitosan.

4. The hydrogel according to claim 3, characterized in that, The mass ratio of methacrylic anhydride to chitosan is (0.4-1.2):

1.

5. The hydrogel according to claim 3, characterized in that, The mass-to-volume ratio of methacrylic anhydride-modified chitosan to water in the aqueous solution is (0.005-0.05) g: 1 mL.

6. The hydrogel according to claim 2, characterized in that, The modified polyethylene glycol is aldehyde-terminated polyethylene glycol, and the mass-to-volume ratio of aldehyde-terminated polyethylene glycol to water in the modified polyethylene glycol aqueous solution is (0.05-0.3) g: 1 mL.

7. The hydrogel according to claim 2, characterized in that, The mass-to-volume ratio of polyvinyl alcohol to water in the polyvinyl alcohol aqueous solution is (0.05-0.2) g: 1 mL; The mass ratio of dopamine hydrochloride to polyvinyl alcohol is 1:(4-10).

8. A method for preparing a hydrogel according to claim 2, characterized in that, The method for preparing the hydrogel includes: S1. Prepare modified chitosan and prepare modified chitosan aqueous solution; S2. Prepare a modified polyethylene glycol aqueous solution; S3 prepares an aqueous solution of polyvinyl alcohol containing dopamine hydrochloride; S4. Mix the modified chitosan aqueous solution, the modified polyethylene glycol aqueous solution, and the polyvinyl alcohol aqueous solution containing dopamine hydrochloride evenly to obtain a hydrogel; The gelation time of the hydrogel in step S4 is 20-60 seconds.

9. An application of the hydrogel according to claim 2 or the preparation method according to claim 8, characterized in that, The hydrogel is used in the preparation of intervertebral disc repair materials; the raw materials for preparing the intervertebral disc repair materials include hydrogel and drugs.

10. An application according to claim 9, characterized in that, The drugs include one or more of the following: diclofenac sodium, latonic acid, salicylaldehyde, tannic acid, resveratrol, mannitol, dexamethasone, celecoxib, loxoprofen sodium, meloxicam, prednisolone acetate, and methylprednisolone.

Images