High-toughness hydrogel for weight-bearing tissue repair and preparation method of high-toughness hydrogel

Abstract

The invention discloses high-toughness hydrogel for weight-bearing tissue repair and a preparation method of the high-toughness hydrogel, and belongs to the technical field of biomedical materials. In order to solve the problem that an existing degradable material is not matched with a natural load-bearing tissue due to insufficient mechanical properties, the invention provides a hydrogel taking polyvinyl alcohol as a matrix, and a preparation method of the hydrogel comprises the following steps: preparing a PVA aqueous solution, forming a physical cross-linked network precursor through freezing and thawing cycles with specific parameters, and preparing the hydrogel. Then putting into an SHMP solution with a specific concentration range (0.5-3.1 M), and carrying out salting-out treatment; through the synergistic effect of the super-chaotropic effect of the SHMP and the semi-crystalline characteristic of the PVA, molecular chain aggregation and crystallization are remarkably driven, so that the degradable high-toughness hydrogel is prepared; the hydrogel can be completely degraded in a physiological environment within 4-12 weeks, has good biocompatibility, can perfectly meet the mechanical and biological requirements of various load-bearing tissues from cartilage to tendon and the like, and is used for preparing medical instruments or implants for repairing or replacing the tissues.

Description

Technical Field

[0001] This invention belongs to the field of biomedical materials technology, specifically a high-strength and tough hydrogel for the repair of weight-bearing tissues and its preparation method. Background Technology

[0002] Tendons, cartilage, ligaments, and other biological weight-bearing tissues are the core load-bearing structures of the human musculoskeletal system. In daily activities, they perform crucial mechanical functions such as transmitting muscle force, maintaining joint stability, and cushioning mechanical shocks. The superior performance of these tissues stems from their unique extracellular matrix composition and intricate microscopic multilevel structure, such as the highly oriented type I collagen fiber bundles in tendons and the tension-compression biphasic network composed of type II collagen and proteoglycans in cartilage. These structures collectively endow natural weight-bearing tissues with extremely high stiffness (Young's modulus can reach hundreds of MPa or even GPa) and exceptional toughness (typically higher than 10 MJ / m³), enabling them to withstand millions of cyclic loads without damage.

[0003] However, due to their sparse blood vessel distribution and slow cell renewal, these tissues have extremely limited inherent self-repair and regeneration capabilities after trauma, degenerative changes, or surgical damage. Clinically, the repair often results in the formation of scar tissue with poor mechanical properties. Its main component is disordered type III collagen, with a modulus and strength far lower than normal tissue, failing to effectively restore weight-bearing function. This leads to a high risk of re-injury and long-term sequelae such as joint dysfunction.

[0004] Currently, standard clinical treatments for severe weight-bearing tissue defects mainly include autologous transplantation, allogeneic transplantation, and implantation of synthetic materials. While autologous transplantation (such as using hamstring tendons to reconstruct the anterior cruciate ligament) is considered the "gold standard," it inevitably causes donor site damage and functional impairment, and the availability of donor tissues is limited. Allogeneic transplantation faces risks such as immune rejection, disease transmission, slow graft integration, and long-term mechanical performance degradation. Existing synthetic polymer materials, such as non-degradable polyethylene terephthalate (PET) or ultra-high molecular weight polyethylene (UHMWPE), while possessing the required initial mechanical strength, are bioinert foreign bodies. Long-term implantation can easily trigger chronic inflammatory responses, stress shielding leading to atrophy of adjacent tissues, and patients often require a second surgery for removal, increasing both physical and psychological burden and economic costs.

[0005] On the other hand, most biodegradable biomaterials designed to promote tissue regeneration, including traditional collagen sponges, fibrin glue, and a range of synthetic hydrogels (such as polyethylene glycol PEG and polyacrylic acid PAA-based hydrogels), despite their good biocompatibility and biodegradability, generally suffer from a fatal flaw: severely inadequate mechanical properties. Their Young's modulus typically hovers in the range of kPa to low MPa, and their toughness is often below 1 MJ / m³, representing a huge gap of several orders of magnitude compared to the mechanical properties of natural load-bearing tissues. Implanting such "soft" materials into high-mechanical-load environments fails to provide effective mechanical support and necessary stress transmission to the damaged area in the early stages of healing. This not only fails to guide the regeneration of functional tissue but may also lead to early collapse and functional failure of the repaired structure.

[0006] Therefore, the field of biomaterials has long faced a severe challenge: how to develop a novel implantable material that simultaneously possesses tunable in vivo degradation characteristics, excellent biocompatibility, and ultra-high mechanical properties (including stiffness, strength, and toughness) that match and even support the regeneration of natural weight-bearing tissues. Existing technologies often compromise on one aspect while neglecting another, making it difficult to achieve a balance among these multiple stringent requirements. This invention aims to overcome this key technological bottleneck and provide a novel solution.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention optimizes the freeze-thaw cycle and sodium hexametaphosphate salting-out process to prepare a series of polyvinyl alcohol hydrogels. The Young's modulus of this series of hydrogels can range from hundreds to thousands of megapascals, and the fracture energy can reach hundreds of kilojoules per square meter. Its mechanical property spectrum can cover the needs of various weight-bearing tissues, from cartilage to tendons, thus providing a universal and efficient material for solving the biomechanical mismatch problem in tissue repair of different weight-bearing sites.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a biodegradable, high-strength, and tough hydrogel for repairing weight-bearing tissues, comprising the following steps:

[0010] Step 1:

[0011] To prepare an 8-15% (w / w) polyvinyl alcohol aqueous solution: Dissolve polyvinyl alcohol powder in deionized water and stir at 150-250 rpm for 3-5 hours in a water bath at 85-95°C until completely dissolved, obtaining a transparent and homogeneous solution; then centrifuge the solution at 2000-4000 rpm for 80-100 seconds to thoroughly remove air bubbles, obtaining a polyvinyl alcohol aqueous solution;

[0012] Step 2:

[0013] Freeze-thaw cycle treatment: The polyvinyl alcohol aqueous solution obtained in step 1 is injected into the mold and frozen at -20°C for 10-14 hours, and then transferred to 30-50°C for 6-10 hours to thaw; this freeze-thaw cycle treatment is repeated 2-4 times to form a physically cross-linked hydrogel precursor.

[0014] Step 3:

[0015] Salting-out treatment: The hydrogel precursor obtained in step 2 is immersed in a sodium hexametaphosphate (SHMP) solution for salting-out treatment for 12-36 hours to obtain the biodegradable high-strength and tough hydrogel; the sodium hexametaphosphate solution is prepared at 30-60°C with a concentration of 0.5-3.1 mol / L. -1 .

[0016] Preferably, the mass concentration of the polyvinyl alcohol aqueous solution in step 1 is 10%.

[0017] Preferably, the freeze-thaw cycle process in step 2 is repeated 3 times.

[0018] Preferably, in step 3, the hydrogel precursor is immersed in a sodium hexametaphosphate solution for salting out for 24 hours.

[0019] By adopting the above technical solution, a biodegradable, high-strength and tough hydrogel is obtained.

[0020] Preferably, in step 3, the concentration of the sodium hexametaphosphate solution is 2.0 mol / L. -1 Up to 3.1 mol L -1 .

[0021] Preferably, the molecular weight of the polyvinyl alcohol is 89,000-98,000.

[0022] Preferably, in step 3, the salting-out treatment is carried out at 60°C.

[0023] A second aspect of the present invention also provides a high-strength and tough hydrogel for the repair of weight-bearing tissues, which is prepared by the preparation method described above.

[0024] Preferably, the high-strength and high-toughness hydrogel has a Young's modulus of not less than 100 MPa and a toughness of not less than 40 MJ / m. -3 .

[0025] Preferably, the high-strength and high-toughness hydrogel has a Young's modulus of 200 MPa to 1000 MPa and a toughness of 40-90 MJm. -3 Its fracture strength is 10-40 MPa.

[0026] Preferably, the hydrogel can be completely degraded within 4-12 weeks under physiological conditions.

[0027] A third aspect of the present invention also discloses the application of a high-strength and tough hydrogel for the repair of weight-bearing tissues as an in-situ medical scaffold or bone repair implant.

[0028] Preferably, it is used to repair or replace tendons, cartilage, or ligaments.

[0029] The beneficial effects of this invention are:

[0030] 1) First, stable physical cross-linking points (microcrystalline regions) are formed in the PVA network through freeze-thaw cycles with specific parameters; then, salting out is performed using SHMP with super-liquid effect. Its high charge density anions can not only further drive the aggregation of PVA chains to form dense, high-strength crystalline domains, significantly improving the stiffness and strength of the material, but also fix free water molecules in the network through strong hydration, hardening the scarce phase of the polymer, thereby synergistically achieving material reinforcement and toughening at the molecular scale.

[0031] 2) Secondly, SHMP in this invention, as a metabolically compatible salt, not only helps maintain mechanical properties in the residual portion of the gel network, but also endows the material with the characteristic of gradual degradation in the physiological environment; by controlling the concentration of SHMP, the final mechanical property spectrum of the hydrogel can be precisely adjusted so that its Young's modulus covers the needs of various weight-bearing tissues from cartilage to tendons.

[0032] 3) It should be noted that due to the strong hydration capacity of SHMP, the strengthening effect is insufficient when its concentration is too low, while excessively high concentration may increase the brittleness of the material. By controlling the SHMP concentration within the range of 2.0 M to 3.1 M, the hydrogel obtained by this invention can achieve the best balance of stiffness (modulus up to 1.0 GPa), strength (fracture strength up to 40 MPa), and toughness (toughness up to 88 MJ / m³). Its performance is highly matched with that of natural tendons / cartilage, and it can be completely degraded within about 8-12 weeks, perfectly meeting the dual stringent requirements of mechanical support and biocompatibility for implants in the repair of weight-bearing tissues.

[0033] In summary, the invention successfully constructed a polyvinyl alcohol hydrogel that combines degradability, biosafety, and ultra-high mechanical properties through an optimized freeze-thaw cycle combined with sodium hexametaphosphate (SHMP) salting-out treatment. Attached Figure Description

[0034] Figure 1 Electron microscopy characterization of PVA-SHMP hydrogel;

[0035] Figure 2 This is a diagram showing the difference between the repaired and unrepaired results. Detailed Implementation

[0036] The present invention will be further described below through specific embodiments. To make the inventive objectives, technical solutions, and beneficial technical effects of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the embodiments described in this specification are merely for explaining the present invention and are not intended to limit the present invention.

[0037] Unless otherwise stated, all instruments and reagents used in the examples are commercially available or synthesized using conventional methods and can be used directly without further processing, and all instruments used in the examples are commercially available.

[0038] Example 1: High-strength and tough PVA-SHMP2.5 hydrogel

[0039] Step 1: Prepare a 10% (w / w) aqueous solution of polyvinyl alcohol (PVA, Mw: 89000-98000 Da): Dissolve PVA powder in deionized water and stir at 200 rpm for 4 hours in a 95°C water bath until completely dissolved to obtain a transparent and homogeneous solution; then centrifuge the solution at 3000 rpm for 90 seconds to thoroughly remove air bubbles.

[0040] Step 2: Freeze-thaw cycle treatment: The PVA solution obtained in Step 1 is injected into a custom mold and frozen at -20°C for 12 hours, then transferred to 40°C for thawing for 8 hours. This freeze-thaw cycle is repeated 3 times to form a physically cross-linked hydrogel precursor.

[0041] Step 3: Salting out: The hydrogel precursor obtained in Step 2 was immersed in a 2.5 M sodium hexametaphosphate (SHMP) solution prepared at 60°C and subjected to salting out at room temperature for 24 hours. After the treatment was completed, the PVA-SHMP2.5 hydrogel was obtained.

[0042] Example 2: High-strength and tough PVA-SHMP3.1 hydrogel

[0043] Step 1: Prepare a 10% (w / w) aqueous solution of polyvinyl alcohol (PVA, Mw: 89000-98000 Da): Dissolve PVA powder in deionized water and stir at 200 rpm for 4 hours in a 95°C water bath until completely dissolved to obtain a transparent and homogeneous solution; then centrifuge the solution at 3000 rpm for 90 seconds to thoroughly remove air bubbles.

[0044] Step 2: Freeze-thaw cycle treatment: The PVA solution obtained in Step 1 is injected into a custom mold and frozen at -20°C for 12 hours, then transferred to 40°C for thawing for 8 hours. This freeze-thaw cycle is repeated 3 times to form a physically cross-linked hydrogel precursor.

[0045] Step 3: Salting out: The hydrogel precursor obtained in Step 2 was immersed in a 3.1 M sodium hexametaphosphate (SHMP) solution prepared at 60°C and subjected to salting out at room temperature for 24 hours. After the treatment was completed, the PVA-SHMP3.1 hydrogel was obtained.

[0046] Example 3: High-strength and tough PVA-SHMP1.0 hydrogel

[0047] Step 1: Prepare an 8% (w / w) polyvinyl alcohol (PVA, Mw: 89000-98000 Da) aqueous solution: Dissolve PVA powder in deionized water and stir at 250 rpm for 3 hours in an 85°C water bath until completely dissolved to obtain a transparent and homogeneous solution; then centrifuge the solution at 2000 rpm for 100 seconds to thoroughly remove air bubbles.

[0048] Step 2: Freeze-thaw cycle treatment: The PVA solution obtained in Step 1 is injected into a custom mold and frozen at -20°C for 10 hours, then transferred to 30°C for thawing for 10 hours. This freeze-thaw cycle is repeated twice to form a physically cross-linked hydrogel precursor.

[0049] Step 3: Salting out: The hydrogel precursor obtained in Step 2 was immersed in a 1.0 M sodium hexametaphosphate (SHMP) solution prepared at 60°C and subjected to salting out at room temperature for 24 hours. After the treatment was completed, the PVA-SHMP1.0 hydrogel was obtained.

[0050] Example 4: High-strength and tough PVA-SHMP1.5 hydrogel

[0051] Step 1: Prepare a 12% (w / w) aqueous solution of polyvinyl alcohol (PVA, Mw: 89000-98000 Da): Dissolve PVA powder in deionized water and stir at 150 rpm for 5 hours in a 90°C water bath until completely dissolved to obtain a transparent and homogeneous solution; then centrifuge the solution at 4000 rpm for 90 seconds to thoroughly remove air bubbles.

[0052] Step 2: Freeze-thaw cycle treatment: The PVA solution obtained in Step 1 is injected into a custom mold and frozen at -20°C for 36 hours, then transferred to 50°C for 6 hours to thaw. This freeze-thaw cycle is repeated 3 times to form a physically cross-linked hydrogel precursor.

[0053] Step 3: Salting out: The hydrogel precursor obtained in Step 2 was immersed in a 1.5 M sodium hexametaphosphate (SHMP) solution prepared at 60°C and subjected to salting out at room temperature for 24 hours. After the treatment was completed, the PVA-SHMP1.5 hydrogel was obtained.

[0054] Example 5: High-strength and tough PVA-SHMP2.0 hydrogel

[0055] Step 1: Prepare a 15% (w / w) polyvinyl alcohol (PVA, Mw: 89000-98000 Da) aqueous solution: Dissolve PVA powder in deionized water and stir at 150 rpm for 4 hours in a 90°C water bath until completely dissolved to obtain a transparent and homogeneous solution; then centrifuge the solution at 2000 rpm for 90 seconds to thoroughly remove air bubbles.

[0056] Step 2: Freeze-thaw cycle treatment: The PVA solution obtained in Step 1 is injected into a custom mold and frozen at -20°C for 24 hours, then transferred to 40°C for thawing for 8 hours. This freeze-thaw cycle is repeated 4 times to form a physically cross-linked hydrogel precursor.

[0057] Step 3: Salting out: The hydrogel precursor obtained in Step 2 was immersed in a 2.0 M sodium hexametaphosphate (SHMP) solution prepared at 60°C and subjected to salting out at room temperature for 24 hours. After the treatment was completed, the PVA-SHMP2.0 hydrogel was obtained.

[0058] Example 6: High-strength and tough PVA-SHMP2.8 hydrogel

[0059] Step 1: Prepare a 12% (w / w) aqueous solution of polyvinyl alcohol (PVA, Mw: 89000-98000 Da): Dissolve PVA powder in deionized water and stir at 200 rpm for 4 hours in a 95°C water bath until completely dissolved to obtain a transparent and homogeneous solution; then centrifuge the solution at 3000 rpm for 90 seconds to thoroughly remove air bubbles.

[0060] Step 2: Freeze-thaw cycle treatment: The PVA solution obtained in Step 1 is injected into a custom mold and frozen at -20°C for 12 hours, then transferred to 40°C for thawing for 8 hours. This freeze-thaw cycle is repeated 3 times to form a physically cross-linked hydrogel precursor.

[0061] Step 3: Salting out: The hydrogel precursor obtained in Step 2 was immersed in a 2.8 M sodium hexametaphosphate (SHMP) solution prepared at 60°C and subjected to salting out at room temperature for 24 hours. After the treatment was completed, the PVA-SHMP2.8 hydrogel was obtained.

[0062] Example 7: High-strength and tough PVA-SHMP0.5 hydrogel

[0063] Step 1: Prepare a 10% (w / w) aqueous solution of polyvinyl alcohol (PVA, Mw: 89000-98000 Da): Dissolve PVA powder in deionized water and stir at 200 rpm for 4 hours in a 95°C water bath until completely dissolved to obtain a transparent and homogeneous solution; then centrifuge the solution at 3000 rpm for 90 seconds to thoroughly remove air bubbles.

[0064] Step 2: Freeze-thaw cycle treatment: The PVA solution obtained in Step 1 is injected into a custom mold and frozen at -20°C for 36 hours, then transferred to 40°C for thawing for 8 hours. This freeze-thaw cycle is repeated 4 times to form a physically cross-linked hydrogel precursor.

[0065] Step 3: Salting out: The hydrogel precursor obtained in Step 2 was immersed in a 0.5 M sodium hexametaphosphate (SHMP) solution prepared at 60°C and salted out at room temperature for 24 hours. After the treatment was completed, the PVA-SHMP0.5 hydrogel was obtained.

[0066] Comparative Example 1: Salting out with sodium sulfate

[0067] Following the preparation process of Example 1, a sodium sulfate (Na2SO4) solution of the same molar concentration (2.5 M) was used instead of the SHMP solution for salting out for 24 hours.

[0068] Comparative Example 2: PVA hydrogel without salting out treatment

[0069] The 10 wt% PVA solution was subjected to the same freeze-thaw cycle treatment as in Example 1 only three times, without any salting out.

[0070] Comparative Example 3: Preparation of carrageenan hydrogel by SHMP salting-out method

[0071] A 1.5% (w / w) aqueous solution of κ-carrageenan was prepared and stirred at 80°C until completely dissolved. The solution was poured into a mold and cooled to room temperature to form an initial gel. The mold was then immersed in a 2.5 M SHMP solution prepared at 60°C and subjected to salting-out treatment at room temperature for 24 hours to obtain a carrageenan-SHMP hydrogel.

[0072] Comparative Example 4: Preparation of sodium alginate hydrogel by SHMP salting-out method

[0073] A 4% (w / w) sodium alginate aqueous solution was prepared and stirred until completely dissolved at room temperature. The solution was poured into a mold and then immersed in a 2.5 M SHMP solution prepared at 60°C for salting out at room temperature for 24 hours. To avoid cross-linking interference between sodium alginate and Ca²⁺ ions, deionized water was used throughout the process, and no calcium source was added, resulting in a sodium alginate-SHMP hydrogel.

[0074] Comparative Example 5: Preparation of gelatin hydrogels by SHMP salting-out method

[0075] A 20% (w / w) aqueous solution of gelatin was prepared and stirred at 60°C until completely dissolved. The solution was poured into a mold and cooled to 25°C, where a hydrogel was formed within one hour. The gelatin was then immersed in a 2.5 M SHMP solution prepared at 30°C and subjected to salting-out treatment at room temperature for 24 hours to obtain a gelatin-SHMP hydrogel.

[0076] Comparative Example 6: Salting out using sodium phosphate (Na3PO4)

[0077] Following the preparation process of Example 1, a saturated concentration (1.5 M) sodium phosphate (Na3PO4) solution was used instead of SHMP solution. The solution was dissolved and prepared at 60°C and then salted out at room temperature for 24 hours to obtain PVA-Na3PO4 hydrogel.

[0078] Comparative Example 7: Salting out using sodium trimetaphosphate (STPP)

[0079] Following the preparation process of Example 1, a saturated concentration (1.0 M) sodium trimetaphosphate (STPP) solution was used instead of SHMP solution. The solution was dissolved and prepared at 60°C and then salted out at room temperature for 24 hours to obtain PVA-STPP hydrogel.

[0080] The performance of Examples 1-2 was compared with that of Comparative Examples 1-4 and 6-7. The experimental methods are as follows:

[0081] 1. A uniaxial tensile test was conducted on a PVA-SHMP hydrogel measuring 28 cm × 5 cm × 2 cm and weighing 35 g using a universal testing machine. The Young's modulus and toughness were calculated, and the measurement data were obtained.

[0082] II. A rat Achilles tendon mid-section transverse rupture model was established. Animals were randomly divided into three groups: a blank control group (sutured only) and a strong hydrogel group (implanted with PVA-SHMP hydrogel). The effect of the hydrogel of this invention in tendon rupture repair was evaluated. A rat Achilles tendon partial defect or full-thickness transverse rupture model was established. Under aseptic conditions, a longitudinal defect or complete transverse rupture wound of about 5 mm in length was prepared in the mid-section of the Achilles tendon of the rat hind limb. Subsequently, the hydrogel repair scaffold was implanted into the defect or transverse site to tightly integrate with the tendon end. The tendon sheath and skin incision were sutured, disinfected with povidone-iodine, and bandaged with sterile dressing. After 8 weeks of routine feeding after surgery, the sample was euthanized and the Achilles tendon sample was removed to observe the repair.

[0083] The results are shown in the table below:

[0084]

[0085] As can be seen from the table, the PVA-SHMP2.5 hydrogel group showed the best repair effect under comprehensive conditions: the regenerated tissue morphology was similar to that of normal tendons, the collagen fibers were neatly and densely arranged, type I collagen was dominant, and the expression of the tendon maturation marker TNMD was continuously elevated. (See attached table for reference.) Figure 2 The top left image shows that the PVA-SHMP3.1 hydrogel group also showed good repair results (see attached image). Figure 2 The lower left image shows gait analysis. The hard hydrogel group recovered to normal levels in core functional parameters such as swing speed and stride length, significantly outperforming other groups. (See attached image) Figure 2 The four images on the right, from left to right and top to bottom, correspond to proportions 1 / 2 / 3 / 4 respectively. Meanwhile, the implanted PVA-SHMP2.5 hydrogel was almost completely degraded after 8 weeks, and no abnormal inflammatory reaction was observed at the implantation site, demonstrating its good biocompatibility and controllable degradation.

[0086] Data from Examples 1-4 show that the PVA-SHMP hydrogel prepared in this invention exhibits excellent performance. A comparison between Comparative Example 1 and Example 1 demonstrates that sodium hexametaphosphate (SHMP) as a salting-out agent provides a significantly better reinforcing effect than traditional salts (sodium sulfate).

[0087] The comparison between Comparative Example 2 and Example 1 shows that SHMP salting-out treatment is a key step in achieving ultra-high mechanical properties of hydrogels. More importantly, the comparison between Comparative Examples 3, 4, and 5 and Example 1 shows that although SHMP salting-out can enhance the mechanical properties of other biopolymer hydrogels (carrageenan, sodium alginate, gelatin) to some extent, the magnitude of enhancement (modulus increase of tens to hundreds of times) and the final absolute mechanical properties achieved (modulus < 5 MPa) are orders of magnitude lower than those of the PVA system (modulus increase of thousands of times, with final modulus reaching the GPa level). This strongly demonstrates that there is a synergistic effect between the unique semi-crystalline properties of PVA and the superfluid effect of SHMP. The combination of these two is a necessary and unique condition for obtaining this "glass-like" high-strength and tough hydrogel, and cannot be achieved simply by combining any polymer with SHMP.

[0088] III. Subcutaneous implantation experiments were conducted on water rats using Examples 1 and 7 to verify the degradation time of the gel in a physiological environment. The specific steps are as follows:

[0089] 1. Laboratory animals and grouping:

[0090] Healthy adult SD rats (weighing 200±20g) were randomly divided into two groups of 6 rats each.

[0091] Experimental Group A: Implanted with PVA-SHMP2.5 hydrogel (SHMP concentration 2.5 M) prepared in Example 1.

[0092] Experimental Group B: Implanted with PVA-SHMP0.5 hydrogel (SHMP concentration 0.5 M) prepared in Example 7.

[0093] All animal experiments were conducted in accordance with the Guidelines for the Management and Use of Laboratory Animals and were approved by the institution’s animal ethics committee.

[0094] 2. Sample pretreatment:

[0095] The two sets of hydrogels were cut into uniform sizes (10 mm in diameter and 2 mm in thickness) and then sterilized by ultraviolet light.

[0096] 3. Surgical implantation:

[0097] After anesthetizing rats with intraperitoneal injection of sodium pentobarbital (40 mg / kg), the skin of the midline area of ​​the back was prepared and disinfected.

[0098] Make a longitudinal incision of about 2 cm on each side of the back, bluntly dissect the subcutaneous tissue to form a small cavity;

[0099] The pre-equilibrated hydrogel sample was implanted into the cavity to ensure that the sample adhered to the surrounding tissue;

[0100] The skin incision was sutured, and the animal was observed daily postoperatively. No abnormalities such as infection or rejection were observed.

[0101] 4. Sample collection and quality determination:

[0102] Two rats from each group were sacrificed at 30 minutes, 1 week, 2 weeks, 4 weeks, and 8 weeks post-implantation. Hydrogel samples were removed from the implantation site and gently rinsed with sterile saline to remove attached tissue.

[0103] Weigh the dry weight using a precision electronic balance (accuracy 0.01 mg). The formula for calculating the remaining mass percentage (MassRemaining%) is as follows:

[0104] Remaining mass (%) = Wt / W0 × 100% where W0 is the initial dry weight of the sample before implantation and Wt is the dry weight of the sample after removal.

[0105] 5. Results and Analysis:

[0106] The experimental data are shown in the table below:

[0107] Remaining mass (%) of PVA-SHMP2.5 at time point Remaining mass (%) of PVA-SHMP0.5

[0108] 30 minutes 100 ± 0.2 100 ± 0.3

[0109] 1 week 94.5 ± 1.1 81.9 ± 2.0

[0110] 2 weeks 80.9 ± 2.5 45.2 ± 3.1

[0111] 4 weeks 51.2 ± 3.8 Completely degraded (not detected)

[0112] 8 weeks 46.7 ± 2.1 Completely degraded (not detected)

[0113] in conclusion:

[0114] 1) Degradation behavior exhibits a significant concentration dependence: Sodium hexametaphosphate (SHMP) concentration has a decisive influence on the in vivo degradation rate of hydrogels. PVA-SHMP0.5 hydrogels degrade rapidly, completely degrading within 4 weeks; while PVA-SHMP2.5 hydrogels show a slow, controllable degradation trend, retaining approximately 46.7% of their mass even after 8 weeks. This indicates that by adjusting the SHMP concentration (0.5-3.1 M), the degradation cycle of hydrogels in vivo can be precisely controlled, achieving degradation time windows ranging from several weeks to several months to meet the needs of tissues at different repair stages.

[0115] 2) The degradation kinetics of PVA-SHMP2.5 hydrogel are highly matched with the repair cycle of weight-bearing tissues: PVA-SHMP2.5 hydrogel maintains high structural integrity (remaining mass >80%) within 1-2 weeks after implantation, which can provide stable mechanical support for the early stage of tissue repair; it gradually degrades during 4-8 weeks (remaining mass decreases from 51.2% to 46.7%), and its degradation rate is consistent with the natural healing cycle of weight-bearing tissues such as tendons and cartilage (usually 6-12 weeks), which is conducive to gradually transferring the load to the new tissue during the repair process and achieving a benign transition of "support-degradation-replacement".

[0116] 3) All systems exhibited good biocompatibility and degradation safety: Throughout the experimental period, no obvious acute or chronic inflammatory reactions, signs of infection, or abnormal fibrous encapsulation were observed at any implantation site. PVA-SHMP0.5 hydrogel left no residue after complete degradation, and PVA-SHMP2.5 hydrogel did not cause any local or systemic toxicity during degradation, demonstrating that SHMP, as a metabolically compatible salt, forms degradation products with PVA that have good biocompatibility.

[0117] 4) Comprehensive mechanical and degradation properties indicate that PVA-SHMP2.5 is the optimal system: Combining the previous mechanical test results with the degradation data in this study, PVA-SHMP2.5 hydrogel maintains ultra-high mechanical properties that match those of natural tendons / cartilage while possessing controllable, gradual, and complete in vivo degradation characteristics. Furthermore, no premature degradation or degradation stagnation was observed within 8 weeks, indicating that it is an ideal load-bearing tissue repair material with both "high strength and toughness" and "controllable degradation" characteristics.

[0118] In summary, this invention pioneers a novel technical route for preparing ultra-high mechanical properties hydrogels through "physical cross-linking + salting out," addressing the challenges of simultaneously achieving high mechanical properties and biodegradability and biosafety, as well as the mismatch between the mechanical properties of synthetic materials and natural load-bearing tissues, solely through the synergistic effect of PVA and SHMP.

[0119] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0120] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a high-strength and tough hydrogel for repairing weight-bearing tissues, characterized in that, Includes the following steps: Step 1: Preparation of polyvinyl alcohol aqueous solution: Dissolve polyvinyl alcohol powder in deionized water and stir in a water bath at 85-95°C until completely dissolved to obtain a transparent and homogeneous solution; The solution was then centrifuged to completely remove air bubbles, yielding an aqueous solution of polyvinyl alcohol. Step 2: Freeze-thaw cycle treatment: The polyvinyl alcohol aqueous solution obtained in step 1 is injected into the mold, and the freeze-thaw cycle treatment is repeated 2-4 times to form a physically cross-linked hydrogel precursor. Step 3: Salting out treatment: The hydrogel precursor obtained in step 2 was immersed in sodium hexametaphosphate SHMP solution for salting out treatment to obtain a biodegradable high-strength and tough hydrogel. The concentration of the sodium hexametaphosphate solution is 0.5-3.1 mol / L. -1 .

2. The method for preparing a high-strength and tough hydrogel for repairing load-bearing tissues according to claim 1, characterized in that, In step 1, the mass concentration of the polyvinyl alcohol aqueous solution is 8-15%, and it is stirred at 150-250 rpm for 3-5 hours and centrifuged at 2000-4000 rpm for 80-100 seconds; the molecular weight of the polyvinyl alcohol is 89000-98000.

3. The method for preparing a high-strength and tough hydrogel for repairing weight-bearing tissues according to claim 1, characterized in that, The freeze-thaw cycle process in step 2 involves freezing at -20°C for 10-14 hours, and then thawing at 30-50°C for 6-10 hours.

4. The method for preparing a high-strength and tough hydrogel for repairing load-bearing tissues according to claim 1, characterized in that, In step 3, the sodium hexametaphosphate solution is prepared by dissolving at 30-60°C, and the concentration of the sodium hexametaphosphate solution is 2.0 mol / L. -1 Up to 3.1 mol L -1 The salting-out time is 12-36 hours, and the salting-out treatment is carried out at 60°C.

5. A high-strength and tough hydrogel for repairing weight-bearing tissues, characterized in that, The high-strength and tough hydrogel prepared by the preparation method according to any one of claims 1-4 has a Young's modulus of not less than 0.1 GPa and a toughness of not less than 40 MJ / m. -3 The hydrogel can be completely degraded within 4-12 weeks under physiological conditions.

6. A high-strength and tough hydrogel for repairing weight-bearing tissues according to claim 5, characterized in that, The high-strength and high-toughness hydrogel has a Young's modulus of 0.2 GPa to 1.0 GPa and a toughness of 40-90 MJ / m. -3 Its fracture strength is 10-40 MPa.

7. A high-strength and tough hydrogel for the repair of weight-bearing tissues, used as an in-situ medical scaffold or bone repair implant.

8. The application according to claim 7, characterized in that, For repairing or replacing tendons, cartilage, or ligaments, the hydrogel degrades and restores gait function within 8 weeks in vivo.

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