Piezoelectric double-network hydrogel coating modified titanium material and preparation method and application thereof

Abstract

The invention discloses a piezoelectric double-network hydrogel coating modified titanium material and a preparation method and application thereof, and belongs to the technical field of biomedical materials. The piezoelectric double-network hydrogel coating modified titanium material provided by the invention comprises a titanium substrate, an adhesion layer and a piezoelectric double-network hydrogel coating, wherein the adhesion layer and the piezoelectric double-network hydrogel coating are compounded on the titanium substrate; the adhesion layer is compounded on the titanium substrate, and the adhesion layer is positioned between the titanium substrate and the piezoelectric double-network hydrogel coating; and the piezoelectric double-network hydrogel coating is prepared from methacrylic acid modified gelatin, sodium alginate and whitmanite nanoparticles. According to the prepared modified titanium material, electric signals can be generated on the surface of the piezoelectric material under the action of polarization or stress, recovery of charge transfer of a bone defect part is facilitated, a good electroactive microenvironment is created for bone regeneration, the osseointegration capacity of the modified titanium material is enhanced, and bone regeneration is effectively promoted; the method has a wide application prospect in preparation of bone graft materials and bone repair materials.

Description

Technical Field

[0001] This application belongs to the field of biomedical materials technology, and in particular relates to a piezoelectric dual-network hydrogel coating modified titanium material, its preparation method and application. Background Technology

[0002] Currently, bone defects caused by traumatic injuries, infections, and skeletal diseases are increasing dramatically. Bone transplantation has become the second most common transplant surgery after blood transfusion, and developing artificial implants with highly efficient osseointegration capabilities has become an important research topic both domestically and internationally. Existing methods typically involve rationally designing biomaterial scaffolds, such as nanostructures, electrical signals, magnetic signals, and thermal effects, to simulate the bone tissue microenvironment and regulate cell behavior around the bone repair scaffold to achieve better bone repair outcomes. However, traditional biomaterial scaffolds (such as chitosan scaffolds, ceramic scaffolds, and hydrogel scaffolds) still suffer from poor biodegradability and low bioactivity during actual repair processes, resulting in insufficient bone repair capabilities. Therefore, there is a need to develop a biomaterial scaffold with superior overall performance to achieve effective treatment of bone defects.

[0003] The prior art with application publication number CN 117717651 A discloses a method for preparing a biomimetic piezoelectric heteromaterial, which involves loading gelatin containing methacrylate, sodium alginate, sintered white calcium phosphite and a photoinitiator onto the surface of a bone-promoting porous material and then irradiating it with light to obtain the biomimetic piezoelectric heteromaterial.

[0004] However, existing biomimetic piezoelectric heteromaterials have the following problems: First, the piezoelectricity of piezoelectric hydrogels mainly depends on the amount of integrated piezoelectric materials. The higher the piezoelectric performance, the better its ability to convert mechanical stress into electrical signals. However, the properties of the hydrogel matrix itself, such as mechanical properties, also have a significant impact on its bone repair ability (the compressive modulus of natural bone is 4-30 GPa). Second, the content of piezoelectric materials will directly change the network structure of the hydrogel, thereby affecting its mechanical properties. Summary of the Invention

[0005] This application discloses a piezoelectric dual-network hydrogel coating modified titanium material, its preparation method and application, aiming to solve the technical problems of low bioactivity and high elastic modulus of existing titanium and its alloy surfaces.

[0006] To achieve the above objectives, the technical solution of this application is:

[0007] The first aspect of this application provides a piezoelectric dual-network hydrogel coating modified titanium material, comprising: a titanium substrate and an adhesive layer and a piezoelectric dual-network hydrogel coating composited on the titanium substrate;

[0008] The adhesive layer is laminated onto the titanium substrate, and the adhesive layer is located between the titanium substrate and the piezoelectric dual-network hydrogel coating;

[0009] The piezoelectric dual-network hydrogel coating is made of methyl methacrylate modified gelatin, sodium alginate and white phosphogypsum nanoparticles.

[0010] Preferably, in conjunction with the first aspect, the mass ratio of the methacrylate-modified gelatin, sodium alginate, and leucobionic calcium phosphate nanoparticles is 15:1:1-5.

[0011] Preferably, in conjunction with the first aspect, the mass ratio of the methacrylate-modified gelatin, sodium alginate, and leucobionic acid nanoparticles is 15:1:3.

[0012] The second aspect of this application provides a method for preparing the piezoelectric dual-network hydrogel coating modified titanium material described in the first aspect, the method comprising:

[0013] The pretreated titanium substrate was placed in a dopamine hydrochloride solution to obtain Ti-PDA;

[0014] Melamine-modified gelatin, sodium alginate, and photoinitiator were dissolved in PBS solution. After complete dissolution, white phosphogypsum nanoparticles were added to form a hydrogel precursor solution.

[0015] The hydrogel precursor solution was composited onto the Ti-PDA, and after being irradiated with ultraviolet light, it was immersed in a calcium salt aqueous solution to obtain the piezoelectric dual-network hydrogel coating modified titanium material.

[0016] In conjunction with the second aspect, preferably, the ultraviolet irradiation time is 5 minutes.

[0017] Preferably, in conjunction with the second aspect, the concentration of the calcium salt aqueous solution is 2 wt%.

[0018] Preferably, in conjunction with the second aspect, the calcium salt is selected from one or more of Ca(OH)2, CaCO3, CaO, CaO2, and CaCl2.

[0019] In conjunction with the second aspect, preferably, the selected photoinitiator is one of I2959 and LAP.

[0020] The third aspect of this application provides the application of the piezoelectric dual-network hydrogel-coated modified titanium material described in the first aspect or the piezoelectric dual-network hydrogel-coated modified titanium material prepared by the preparation method described in the second aspect in the preparation of bone graft materials and bone repair materials.

[0021] Compared with the prior art, the advantages or beneficial effects of the embodiments of this application include at least the following:

[0022] The piezoelectric dual-network hydrogel coating modified titanium material provided in this application is a composite material formed by applying a piezoelectric dual-network hydrogel coating to the surface of a titanium substrate using methyl methacrylate-modified gelatin, sodium alginate, and leucobionic calcium alginate nanoparticles. Firstly, the leucobionic calcium alginate nanoparticles are uniformly dispersed within a hydrogel matrix formed by the methyl methacrylate-modified gelatin and sodium alginate forming a dual-network interpenetrating polymer network, endowing the composite coating with excellent adhesion strength to the modified titanium surface. Secondly, it can establish a special "buffer zone" between the titanium and tissue, possessing a porous structure similar to the extracellular matrix, which can induce cell migration and infiltration, exhibiting enhanced mechanical properties and stability. Thirdly, under low-intensity pulsed ultrasound stimulation (LIPUS), it can convert mechanical stress into electrical signals, which is beneficial for restoring charge transfer at bone defect sites and creating a favorable electroactive microenvironment for bone regeneration. This composite piezoelectric hydrogel coating comprehensively exhibits good mechanical properties, piezoelectricity, and biodegradability, which is beneficial for enhancing the bone integration capacity of titanium implants and effectively promoting bone regeneration. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 Scanning electron microscope (SEM) images and AFM images of Ti, α-Ti, and Ti-PDA prepared for the embodiments of this application;

[0025] Figure 2 The performance characterization diagram of the white phosphogypsum nanoparticles prepared in the embodiments of this application is shown.

[0026] Figure 3 Piezoelectric constant diagrams of Ti-GS / 1PWH, Ti-GS / 2PWH, Ti-GS / 3PWH, and Ti-GS / 5PWH prepared for embodiments of this application;

[0027] Figure 4 Stress-strain curves and compressive modulus diagrams of Ti-G, Ti-GS, Ti-GS / 1PWH, Ti-GS / 2PWH, Ti-GS / 3PWH, and Ti-GS / 5PWH prepared for embodiments of this application;

[0028] Figure 5 Cell compatibility diagrams of Ti, Ti-G, Ti-GS, Ti-GS / 1PWH, Ti-GS / 2PWH, Ti-GS / 3PWH, and Ti-GS / 5PWH hydrogel coatings prepared for embodiments of this application, as well as hydrogel coatings under different ultrasonic powers.

[0029] Figure 6 Scanning electron microscope images of Ti, Ti-G, Ti-GS, and Ti-GS / 3PWH prepared for embodiments of this application;

[0030] Figure 7 Adhesion force analysis diagram of Ti-GS / 3PWH piezoelectric dual-network hydrogel coating prepared in the embodiments of this application;

[0031] Figure 8 Qualitative and quantitative analysis diagrams of alkaline phosphatase and calcium nodule secretion of Ti, Ti+US, Ti-GS, Ti-GS+US, Ti-GS / PWH, and Ti-GS / PWH+US prepared for embodiments of this application. Detailed Implementation

[0032] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0033] In the following description of this embodiment, the term "and / or" is used to describe the association relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, B existing alone, and A and B existing simultaneously. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0034] In the following description of this embodiment, the term "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0035] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0036] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0037] It should be noted that all raw materials and reagents in the embodiments of this application were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0038] In a first aspect, embodiments of this application provide a piezoelectric dual-network hydrogel coating modified titanium material, comprising: a titanium substrate and an adhesive layer and a piezoelectric dual-network hydrogel coating composited on the titanium substrate;

[0039] The adhesive layer is laminated onto the titanium substrate, and the adhesive layer is located between the titanium substrate and the piezoelectric dual-network hydrogel coating;

[0040] The piezoelectric dual-network hydrogel coating is made of methyl methacrylate modified gelatin (GelMA), sodium alginate (SA), and annealed white calcium phosphite nanoparticles (PWH NPs).

[0041] Firstly, the uniform dispersion of white phosphogypsum nanoparticles within a hydrogel matrix formed by a double-network interpenetrating polymer network of methyl methacrylate-modified gelatin and sodium alginate imparts excellent adhesion strength between the composite coating and the modified titanium surface. Secondly, it establishes a unique "buffer zone" between the titanium and tissue, possessing a porous structure similar to the extracellular matrix, which can induce cell migration and infiltration, exhibiting enhanced mechanical properties and stability. Thirdly, under low-intensity pulsed ultrasound stimulation (LIPUS), it can convert mechanical stress into electrical signals, which is beneficial for restoring charge transfer at bone defect sites and creating a favorable electroactive microenvironment for bone regeneration. This composite piezoelectric hydrogel coating comprehensively exhibits excellent mechanical properties, piezoelectricity, and biodegradability, which is beneficial for enhancing the osseointegration capacity of titanium implants and effectively promoting bone regeneration.

[0042] In this embodiment, the preferred mass ratio of the methyl methacrylate-modified gelatin, sodium alginate, and leucobionic calcium phosphate nanoparticles is 15:1:1-5, more preferably 15:1:3. By controlling the amount of each substance added, a two-component interpenetrating hydrogel network composed of GelMA and SA is constructed. Compared to traditional single-network hydrogels, this two-network hydrogel exhibits enhanced mechanical properties and stability. A novel composite hydrogel coating was developed by combining piezoelectric nanoparticles (PWH NPs) and a two-component hydrogel network. The mechanical properties, piezoelectricity, and biocompatibility of this composite hydrogel coating are improved. The aim is to improve its high elastic modulus and bioactivity by preparing a piezoelectric hydrogel coating, which, under external mechanical stimulation, has the ability to convert mechanical stimulation into electrical signals to restore the electrical microenvironment of bone defect sites.

[0043] It should be noted that the embodiments of this application do not impose any particular restrictions on the specific sources of the methacrylate-modified gelatin and annealed white calcium phosphite nanoparticles, which can be synthesized by commercial means or by methods known in the art. For example, the preparation method used in the embodiments of this application is as follows:

[0044] Synthesis of white phosphogypsum nanoparticles:

[0045] WH NPs were synthesized by chemical precipitation. Calcium hydroxide (0.37M) and magnesium hydroxide (0.13M) were co-dissolved in deionized water and kept at 85°C for 1 h. Then, phosphoric acid solution (0.5M) was added dropwise at a rate of 12.5 mL / min. After aging for 20 h, the resulting milky white precipitate was centrifuged (4000 rpm, 5 min), washed until neutralized, and finally dried overnight at 100°C to obtain highly crystalline WH NPs. Furthermore, the piezoelectricity of these nanoparticles was enhanced by annealing. To induce piezoelectricity, WH NPs were annealed in a muffle furnace at 750°C for 3 h to obtain piezoelectric whitlockite nanoparticles (PWH NPs).

[0046] Synthesis of methacrylic acid modified gelatin:

[0047] First, 10 g of gelatin was dispersed in 100 mL of phosphate-buffered saline (PBS, pH 7.4) and magnetically stirred at 50 °C for 1 h until completely dissolved. Then, 6 mL of methacrylic anhydride (MA) was slowly added while protecting from light, and the reaction was continued for 3 h. After the reaction was complete, 200 mL of preheated PBS solution was added to terminate the reaction. To eliminate any residual unreacted MA, the mixture was dialyzed at 50 °C for 5–7 days, with the solution changed multiple times daily. The molecular weight cutoff of the dialysis bag was 8 kDa–14 kDa. After dialysis, the dialysate was placed at -80 °C for 24 h and then freeze-dried. The GelMA sample was stored at -20 °C protected from light for further use.

[0048] Secondly, embodiments of this application also provide a method for preparing the piezoelectric dual-network hydrogel coating modified titanium material as described in the first aspect, the preparation method comprising:

[0049] The pretreated titanium substrate was placed in a dopamine hydrochloride solution to obtain Ti-PDA;

[0050] Melamine-modified gelatin, sodium alginate, and photoinitiator were dissolved in PBS solution. After complete dissolution, white phosphogypsum nanoparticles were added to form a hydrogel precursor solution.

[0051] The hydrogel precursor solution was composited onto the Ti-PDA, and after being irradiated with ultraviolet light, it was immersed in a calcium salt aqueous solution to obtain the piezoelectric dual-network hydrogel coating modified titanium material.

[0052] It should be noted that the titanium-based pretreatment described in this application includes: selecting a 10mm × 10mm titanium foil, ultrasonically cleaning it sequentially with acetone, ethanol, and distilled water, drying it, and then heat-treating it with 5M NaOH for 24 hours. After cleaning, the treated titanium foil is placed in a Tris-HCl solution containing 2 mg / mL dopamine hydrochloride and shaken overnight at room temperature in the dark. The resulting sample is then thoroughly ultrasonically cleaned with deionized water to obtain polydopamine-modified titanium sheets, which are dried for later use. The alkaline-treated titanium sheets are named a-Ti, and the dopamine-coated titanium is named Ti-PDA.

[0053] It should be noted that methyl methacrylate-modified gelatin (GelMA) and sodium alginate were chosen as the hydrogel base materials to form a double-network interpenetrating polymer network hydrogel. Alginate has advantages such as good biocompatibility, easy availability, rapid gelation, and improved tissue strength, but it has low flexibility and low degradation rate. GelMA, a gelatin-based material, has high biocompatibility, but relatively poor mechanical strength and toughness. Using sodium alginate as the second component of the composite hydrogel coating, a hydrogel coating with better mechanical strength than modified gelatin was prepared, which can improve the osseointegration ability of titanium implants. Meanwhile, Whitlockite (WH, Ca...) was selected... 18 Mg2(HPO4)2(PO4) 12 Nanoparticles, the second most abundant inorganic bone mineral in the body, release additional Mg. 2+It is a multifunctional therapeutic ion that has been shown to enhance osteoblast activity, promote angiogenesis, and thus improve bone integration. As magnesium-doped calcium phosphate, the annealed WH nanoparticles exhibit significant polarization above the phase transition temperature, which corresponds to the electrical activity of natural bone. By selecting and doping with high-temperature annealed Whitlockite nanoparticles (PWHNPs) which possess piezoelectric properties, the hydrogel is endowed with piezoelectric properties, which is beneficial for charge transfer and can effectively restore the electrical microenvironment of bone defect sites, thereby enhancing the bone regeneration capacity of titanium implants.

[0054] In this embodiment, the hydrogel precursor solution is composited onto the Ti-PDA and irradiated with ultraviolet light for 5 minutes. The concentration of the calcium salt aqueous solution is preferably 2 wt%. The calcium salt is preferably one or more of Ca(OH)2, CaCO3, CaO, CaO2, and CaCl2.

[0055] In this embodiment, the selected photoinitiator is preferably one of I2959 and LAP; the ultraviolet light wavelength is preferably 365-405nm. Specifically, the piezoelectric double-network hydrogel prepared by dissolving methyl methacrylate-modified gelatin, sodium alginate, and the photoinitiator in PBS solution can be cross-linked and cured into a hydrogel by ultraviolet light irradiation.

[0056] The third aspect of this application provides the application of the piezoelectric dual-network hydrogel-coated modified titanium material described in the first aspect or the piezoelectric dual-network hydrogel-coated modified titanium material prepared by the preparation method described in the second aspect in the preparation of bone graft materials and bone repair materials. Specifically, the modified titanium material possesses excellent mechanical properties and piezoelectricity while maintaining high water content and adhesion, effectively promoting osteogenic differentiation of stem cells, and has broad application prospects in the preparation of bone graft materials and bone repair materials.

[0057] The technical solution of this application will be further described below with reference to specific embodiments.

[0058] Example 1

[0059] This embodiment provides a method for preparing A1-piezoelectric dual-network hydrogel coating modified titanium material (Ti-GS / PWH), specifically including:

[0060] S101: Titanium sheets are placed in 5M NaOH solution for alkaline heat treatment to obtain pretreated a-Ti. The pretreated titanium substrate is placed in dopamine hydrochloride solution to obtain Ti-PDA.

[0061] S102: Melamine-modified gelatin (15% w / v) and photoinitiator LAP (0.1% w / v) were stirred in PBS solution at 37°C until completely dissolved, and then white phosphogypsum nanoparticles (3 wt%) were added to obtain a mixed solution;

[0062] S103: The mixed solution was dropped onto the Ti-PDA surface and exposed to 365nm ultraviolet light for photocrosslinking for 5 minutes. Subsequently, the prepared titanium-based hydrogel was immersed in a 2% w / v CaCl2 solution for Ca crosslinking. 2+ Crosslinking for 10 minutes yields Al-piezoelectric dual-network hydrogel-coated modified titanium material (Ti-GS / 3PWH).

[0063] Example 2

[0064] The preparation method, composition ratio, preparation operation, and process parameters of the piezoelectric dual-network hydrogel coating modified titanium material provided in this embodiment are basically the same as those in Example 1. The difference is that the amount of white phosphogypsum nanoparticles added in the second step of this embodiment is 1wt%, 2wt%, and 5wt%, respectively, resulting in A2-piezoelectric dual-network hydrogel coating modified titanium material (Ti-GS / 1PWH), A3-piezoelectric dual-network hydrogel coating modified titanium material (Ti-GS / 2PWH), and A4-piezoelectric dual-network hydrogel coating modified titanium material (Ti-GS / 5PWH).

[0065] Meanwhile, to verify the comprehensive performance of the piezoelectric dual-network hydrogel coating modified titanium material prepared in the above embodiments, this application provides the following comparative examples for detailed illustration.

[0066] Comparative Example 1

[0067] In this comparative example, the raw material a-Ti from Example 1 is used as Comparative Example 1, denoted as B1-modified titanium material (a-Ti).

[0068] Comparative Example 2

[0069] In this comparative example, the raw material Ti-PDA used in Example 1 is used as Comparative Example 1, denoted as B1-modified titanium material (Ti-PDA).

[0070] Comparative Example 3

[0071] The preparation method, composition ratio, preparation operation, and process parameters of the piezoelectric dual-network hydrogel coating modified titanium material provided in this comparative example are basically the same as those in Example 1. The difference is that white phosphogypsum nanoparticles were not added in the second step of this example to obtain B3-modified titanium material (Ti-GS).

[0072] Comparative Example 4

[0073] The preparation method, composition ratio, preparation operation, and process parameters of the piezoelectric dual-network hydrogel coating modified titanium material provided in this comparative example are basically the same as those in Example 1. The difference is that sodium alginate and white phosphogypsum nanoparticles were not added in the second step of this example to obtain B4-modified titanium material (Ti-G).

[0074] 1. Microscopic morphology inspection of hydrogel coating surface:

[0075] To verify the morphology of the modified titanium material prepared in the embodiments of this application, the intermediate prepared in the embodiments was tested by scanning electron microscopy and atomic force microscopy. The results were as follows: Figure 1 As shown; where, Figure 1 Scanning electron microscope (SEM) images and AFM images of Ti, a-Ti, and Ti-PDA are shown.

[0076] according to Figure 1 As is known, (a) is a scanning electron microscope image, showing that the surface of pure titanium (Ti) is relatively smooth and flat, while the alkaline-treated titanium (a-Ti) exhibits a rough micro-nano structure, which provides more contact sites for grafting organic molecular layers. The polydopamine coating is uniformly distributed on the titanium surface (Ti-PDA) and also exhibits a similar rough surface structure. (b) is an AFM image, showing that the surface roughness of the sample can regulate cell behavior. The results indicate that the surface roughness of titanium significantly increases after alkaline-treated treatment and the preparation of the polydopamine coating, which is significantly higher than that of pure titanium. This provides more grafting sites for the hydrogel coating, thereby enhancing the adhesion strength of the hydrogel coating on the titanium surface.

[0077] To verify the effect of adding white phosphogypsum nanoparticles on the prepared material, corresponding performance tests were conducted before and after calcination. Here, WH NPs and PWH NPs represent the white phosphogypsum nanoparticles before and after calcination, respectively. The results are as follows: Figure 2 As shown.

[0078] according to Figure 2As is known, (a) SEM images of WH NPs; (b) TEM images of WH NPs; (c) EDS images of WH NPs; (d) thermogravimetric analysis of WH NPs and PWH NPs; (e) XRD images of WH NPs and PWH NPs; (f) FTIR images of WH NPs and PWH NPs; and (g) hysteresis loop analysis of PWH NPs. WH NPs were synthesized by chemical precipitation. The size and morphology of WH NPs were analyzed by SEM and TEM, as shown in Figures (a) and (b). The morphology of WH NPs was relatively uniform. The WH NPs magnified by transmission electron microscopy showed highly ordered lattice fringes with a crystal plane spacing of 0.2501 nm, corresponding to the (2110) crystal plane of WH NPs. Energy-dispersive X-ray spectroscopy (EDS) analysis of the elemental color mapping in Figure (c) shows that Ca, Mg, P, and O elements are uniformly present in WHNPs. To induce the piezoelectricity of WH NPs, the obtained nanoparticles were annealed at 750 °C for 3 h to obtain PWH NPs. Thermogravimetric analysis (TGA) of WH NPs, as shown in Figure (d), revealed rapid evaporation of water molecules and the formation of hydrogen phosphate (HPO4) at 112 °C and 752 °C. 2- The transformation of ) . In order to analyze the effect of H2O loss during high-temperature annealing on the chemical and crystal structure of WH NPs, the structures of WH NPs and PWH NPs were analyzed by XRD and FTIR. As shown in Figure (e), the main diffraction peaks of the sample are located at 28.02°, 31.28° and 34.64°, corresponding to the (214), (0210) and (220) crystal planes, respectively, and corresponding to the standard XRD pattern PDF#04-009-339. FITR analysis results show that, as shown in Figure (f), at 962 cm -1 604cm -1 and 558cm -1 The characteristic peak of WHNPs was observed at 921 cm⁻¹. -1 The characteristic peak at this location confirms the presence of HPO4 in PWH NPs. 2- As shown in Figure (g), PWH NPs exhibit an almost saturated electric field-dependent polarization loop (PE loop), confirming their ferroelectric behavior and indicating that they possess a non-centrosymmetric crystal structure. These results confirm that at an annealing temperature of 750℃, WH NPs readily lose some H₂O, leading to partial reorientation of the HPO₄ and PO₄ domains, thus endowing PWH NPs with good electroactivity. Due to the piezoelectricity of natural bone, PWH NPs are more advantageous than WH NPs in bone tissue regeneration because they have the potential to restore the local endogenous electrical microenvironment.

[0079] 2. Piezoelectricity test of piezoelectric dual-network hydrogel coating:

[0080] To verify the piezoelectric constant of the piezoelectric dual-network hydrogel-coated modified titanium material, a quasi-static d-coating was used. 33 The ZJ-3A instrument was used to measure its piezoelectric constant, and the test results are as follows: Figure 3 As shown.

[0081] according to Figure 3 It can be seen that, by testing the piezoelectric constants of B3-modified titanium materials (Ti-GS) and piezoelectric dual-network hydrogel-coated modified titanium materials (Ti-GS / 1PWH, Ti-GS / 2PWH, Ti-GS / 3PWH, Ti-GS / 5PWH), the pure dual-network hydrogel has a lower piezoelectric constant, while the hydrogel coating has a lower d... 33 The piezoelectric coefficient gradually increases with increasing concentration of PWH NPs, with Ti-GS / 3PWH and Ti-GS / 5PWH showing the highest dpiezoelectricity. 33 The piezoelectric coefficients reached 4.8±0.5 pC / N and 6.1±1.4 pC / N, respectively, which are close to the piezoelectric coefficients of bone tissue (femur d). 33 The piezoelectric coefficient is approximately 0.7 pC / N, and the tibial d 33 The piezoelectric coefficient is approximately 7.7-8.7 pC / N. However, excessively high concentrations of PWH NPs can affect the cross-linking of the hydrogel network, thus impacting its mechanical properties. The specific concentration of PWH NPs needs to be balanced with the mechanical properties and biocompatibility of the hydrogel coating to achieve better bone repair effects. Under ultrasonic stimulation, this hydrogel coating can generate an electric charge, restoring the electrical microenvironment at the bone defect site and promoting osteogenic differentiation.

[0082] 3. Mechanical property testing of piezoelectric dual-network hydrogel coating:

[0083] according to Figure 4 As shown in Figure (a), the stress-strain curves of each hydrogel coating in the strain range of 0-60% were determined by compression experiments. Compared with pure GelMA hydrogel, the GelMA / SA dual-network hydrogel coating exhibited significantly enhanced fracture stress in the strain range of 60%. With the increase of particle concentration, the mechanical properties of the hydrogel coating were further improved until the fracture stress decreased significantly when the particle concentration was 5wt%. The compressive modulus of the hydrogel coating in the strain range of 5-15% was quantitatively determined, as shown in Figure (b). The results were consistent with the trend of the stress-strain curve. The compressive modulus of the dual-network hydrogel network was significantly higher than that of pure GelMA hydrogel. The addition of a certain concentration of PWH NPs can improve the mechanical properties of the hydrogel. The compressive modulus of the hydrogel coating with 3wt% PWH NPs reached 87.9±5.6kPa. Excessively high concentrations of PWH NPs (greater than 3wt%) significantly reduced the compressive modulus of the hydrogel coating, resulting in poor mechanical properties.

[0084] 4. Biocompatibility testing of piezoelectric dual-network hydrogel coating:

[0085] The CCK-8 assay was used to evaluate the cytotoxicity of different samples and ultrasound power levels on mouse bone marrow mesenchymal stem cells (BMSCs).

[0086] according to Figure 5 To verify the cell compatibility of the modified titanium material prepared in this application, we evaluated the cell compatibility of BMSCs on titanium-based hydrogel coatings with different concentrations of PWH NPs (1 wt%, 2 wt%, 3 wt%, and 5 wt%) and screened for safe PWH NP concentrations. The experimental groups were Ti, Ti-GS, Ti-GS / 1PWH, Ti-GS / 2PWH, Ti-GS / 3PWH, and Ti-GS / 5PWH. As shown in Figure (a), after 3 days of culture, the Ti-GS group exhibited good cell compatibility; when the concentration of PWH NPs was 3 wt%, the cell viability was approximately 82.0%. When the concentration of PWH NPs was too high, the Ti-GS / 5PWH group showed low biocompatibility, with a cell viability of only 64.3%. By day 7, when the PWH NP concentration was below 3 wt%, all hydrogels showed good biocompatibility, while the cell viability of the Ti-GS / 5PWH group decreased significantly. Low-intensity pulsed ultrasound (LIPUS) can apply mechanical stress to cells to regulate cell behavior, but excessive power may negatively impact cell compatibility. Therefore, this experiment screened safe ultrasound parameters. As shown in Figure (b), when the ultrasound power is greater than 0.8 W / cm², the optimal parameters are considered safe. 2 Cell viability decreased significantly, far below 80%, therefore the subsequent ultrasound (US) parameters for cell experiments were determined to be 0.6 W / cm. 2 1.0MHz, 50% duty cycle, 60s stimulation time.

[0087] Studies have shown that the piezoelectricity of piezoelectric hydrogels mainly depends on the number of integrated piezoelectric materials, while the network structure and mechanical properties of the hydrogel matrix are also affected by the number of integrated piezoelectric materials. Hydrogel coatings with higher piezoelectric coefficients can better convert mechanical stress into electrical signals to restore the electrical microenvironment of bone defects and promote bone defect repair. Similarly, the network structure and mechanical properties of hydrogels also affect the bone regeneration capacity of implants. Excessively high particle loading can affect the cross-linking of the hydrogel itself, thereby deteriorating its network structure and mechanical properties. This application investigated the piezoelectric coefficient, mechanical properties, and cell compatibility of hydrogel coatings with different PWH NPs concentrations. The piezoelectric hydrogel coating group with a PWH NPs concentration of 3wt% (Ti-GS / 3PWH) was selected as the final material group, which showed good overall piezoelectricity (piezoelectric coefficient of (4.8±0.5 pC / N), significantly improved mechanical properties (compressive modulus of 87.9±5.6 kPa), and good biocompatibility.

[0088] 5. Morphology and composition characterization of the hydrogel coating on the titanium surface:

[0089] To verify the appearance and morphology of the piezoelectric dual-network hydrogel coating prepared in the embodiments of this application, the modified titanium material prepared in the embodiments was subjected to scanning electron microscopy (SEM) testing. The piezoelectric hydrogel coating group (Ti-GS / 3PWH) was tested, and is denoted as Ti-GS / PWH in the figure.

[0090] according to Figure 6 As shown in Figure (a), the unmodified titanium surface is relatively smooth, and the Ti-G and Ti-GS surfaces have a relatively uniform porous structure, which is beneficial to the adhesion and growth of BMSCs. The addition of PWH NPs did not disrupt the porous structure of the hydrogel coating surface, and the Ti-GS / PWH surface has a relatively uniform network structure, which is beneficial to cell growth. The approximate distribution of PWH NPs in the piezoelectric hydrogel coating on the titanium surface was analyzed by energy dispersive spectroscopy (EDS), as shown in Figure (b). The Ca, Mg, P, and O elements on the surface of the hydrogel coating are relatively uniformly distributed, indicating that the PWH NPs loaded in the dual-network hydrogel coating are relatively uniformly distributed in the hydrogel coating. The three-dimensional hydrogel network with a porous structure can form a buffer zone between the titanium implant and the surrounding bone tissue, guiding the migration, adhesion, proliferation, and differentiation of osteoblast-related cells. As the hydrogel gradually degrades, the newly formed bone tissue will gradually replace the buffer zone and form good osseointegration with the titanium implant.

[0091] 6. Testing of the bonding strength between the hydrogel coating and the titanium interface:

[0092] The bonding strength between the electrospun hydrogel fiber coating and modified titanium was tested using an overlap shear test. Simply put, overlapping areas (10mm × 10mm) were formed between groups of titanium or modified titanium sheets, ensuring the coating surface overlapped parallel to the other titanium sheet. An in-situ mechanical testing system was used, with tensile testing performed at a speed of 0.1mm / s. A significant decrease in traction force was considered a failure of coating adhesion. The bond strength (kPa) was calculated, and the test results are shown below. Figure 7 As shown. The calculation formula is: S a =F m / A. S a For bond strength, A is the overlap area, and F is the bonding strength. m It is the maximum tensile force required during the test.

[0093] This application used lap shear experiments to analyze the changes in adhesion strength between the titanium surface and the hydrogel coating before and after pretreatment. Figures (a) show the stress-strain curves and (b) show the quantitative analysis of adhesion strength. Compared with pure titanium, the modified titanium with alkaline heat treatment and a polydopamine coating exhibited significantly enhanced adhesion strength to the hydrogel coating, with an average adhesion strength of 84.8 ± 13.7 kPa. In contrast, the adhesion strength between unmodified titanium and the hydrogel coating was only 36.6 ± 6.0 kPa. This is not only due to the chemical anchoring effect of the polydopamine coating on the titanium surface, but also because the preparation of the surface topology enhances the adhesion between the titanium surface and the hydrogel coating. High adhesion strength allows functional titanium implants to maintain overall structural stability during implantation and prevents detachment, which is beneficial for the long-term function of the functional coating, as bone defect repair is slow, especially for large bone defects.

[0094] 5. Determination of osteogenic differentiation capacity of cells:

[0095] To investigate the ability of different titanium-based materials to promote osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), this experiment performed qualitative and quantitative detection of ALP and calcium nodules. BMSCs were seeded onto a titanium-based piezoelectric hydrogel coating for 24 hours, followed by ultrasound stimulation for 1 minute each time. The experiment was divided into 6 groups. Based on different material groups, ultrasound stimulation was applied to each material group: Ti, Ti+US, Ti-GS, Ti-GS+US, Ti-GS / PWH, and Ti GS / PWH+US. US represents additional low-intensity pulsed ultrasound (LIPUS) stimulation (0.6 W / cm²). 2 , 1.0MHz, 50% duty cycle, 60s).

[0096] according to Figure 8As shown in Figure (b), after 4 and 7 days of co-culture and continuous ultrasound stimulation, staining results showed that the Ti-GS / PWH+US group had higher ALP expression and deeper staining, which was consistent with the trend of quantitative results. On day 4, there was no significant difference in ALP expression among the Ti, Ti+US, Ti-GS, and Ti-GS+US groups, while the Ti-GS / PWH+US group had the highest ALP expression (p<0.01). On day 7, the Ti GS / PWH+US group further promoted ALP expression under US stimulation (p<0.01). This may be attributed to the fact that the three-dimensional network structure of the hydrogel coating is more conducive to BMSCs adhesion and osteogenic differentiation. The incorporation of PWH NPs endows the hydrogel coating with piezoelectricity, and the electrical signal generated by ultrasound stimulation coupled with the dual-network hydrogel coating promotes early osteogenic differentiation of BMSCs. After 14 and 21 days of co-culture and continuous ultrasound stimulation, the secretion of calcium nodules was assessed by alizarin red staining, as shown in Figure (a). Compared with the Ti, Ti+US, Ti-GS, Ti-GS+US, and Ti-GS / PWH groups, the Ti-GS / PWH+US group showed more stained areas of calcium nodules and a clear mineralization trend. As shown in Figure (c), the quantitative detection of cell mineralization level was consistent with its qualitative results. Compared with the Ti, Ti+US, Ti-GS, and Ti-GS+US groups, the Ti GS / PWH and Ti-GS / PWH+US groups had higher cell mineralization levels, while the Ti-GS / PWH+US group showed a further increase in cell mineralization level compared with the Ti GS / PWH group (p<0.01). This is because the Ti-GS / PWH+US group can convert mechanical stress into electrical signals under ultrasound stimulation, which further promotes osteogenic differentiation of BMSCs. In summary, the quantitative and qualitative analysis of ALP and calcium nodule secretion revealed that among the three groups without ultrasound stimulation (Ti, Ti-GS, and Ti-GS / PWH), the Ti-GS / PWH group showed the best osteogenic differentiation effect. This may be due to the release of active Mg ions from PWH NPs. 2+ , Ca 2+ and PO4 3- It can effectively regulate BMSCs activity and promote extracellular matrix mineralization, thereby promoting osteogenic differentiation of bone marrow mesenchymal stem cells. After ultrasound stimulation, the osteogenic differentiation effect of the Ti+US and Ti-GS+US groups did not change significantly, while the osteogenic differentiation effect of the Ti-GS / PWH+US group was significantly improved. This may be because the incorporation of PWH NPs endows the dual-network hydrogel coating with piezoelectricity. Under ultrasound stimulation, the hydrogel coating can convert the mechanical stress applied by ultrasound into an electrical signal. The dual-network hydrogel coating coupled with ultrasound-driven electrical stimulation can effectively promote osteogenic differentiation of BMSCs.

[0097] Therefore, the piezoelectric dual-network hydrogel-coated modified titanium material provided in this application has excellent osteogenic differentiation-promoting ability. Utilizing the piezoelectricity imparted to the hydrogel coating by PWH NPs, it can convert the mechanical stress applied by the US (ultra-invasive stress) into an electrical signal, synergistically inducing osteogenic differentiation of BMSCs with the hydrogel matrix. The titanium-based piezoelectric dual-network hydrogel coating prepared in this study, in conjunction with the endogenous electrical stimulation generated by US-driven processes, promotes osteogenic differentiation of BMSCs.

[0098] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0099] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A piezoelectric dual-network hydrogel coating modified titanium material, characterized in that, include: A titanium substrate and an adhesive layer and a piezoelectric dual-network hydrogel coating composited on the titanium substrate; The adhesive layer is laminated onto the titanium substrate, and the adhesive layer is located between the titanium substrate and the piezoelectric dual-network hydrogel coating; The piezoelectric dual-network hydrogel coating is made of methyl methacrylate modified gelatin, sodium alginate and white phosphogypsum nanoparticles.

2. The piezoelectric dual-network hydrogel coating modified titanium material according to claim 1, characterized in that, The mass ratio of the methyl methacrylate-modified gelatin, sodium alginate, and leucobionic calcium carbonate nanoparticles is 15:1:1-5.

3. The piezoelectric dual-network hydrogel coating modified titanium material according to claim 1, characterized in that, The mass ratio of the methyl methacrylate-modified gelatin, sodium alginate, and leucobionic calcium carbonate nanoparticles is 15:1:

3.

4. A method for preparing a piezoelectric dual-network hydrogel coating modified titanium material according to any one of claims 1-3, characterized in that, The preparation method includes: The pretreated titanium substrate was placed in a dopamine hydrochloride solution to obtain Ti-PDA; Melamine-modified gelatin, sodium alginate, and photoinitiator were dissolved in PBS solution. After complete dissolution, white phosphogypsum nanoparticles were added to form a hydrogel precursor solution. The hydrogel precursor solution was composited onto the Ti-PDA, and after being irradiated with ultraviolet light, it was immersed in a calcium salt aqueous solution to obtain the piezoelectric dual-network hydrogel coating modified titanium material.

5. The method for preparing the piezoelectric dual-network hydrogel coating modified titanium material according to claim 4, characterized in that, The duration of ultraviolet light irradiation is 5 minutes.

6. The method for preparing the piezoelectric dual-network hydrogel coating modified titanium material according to claim 4, characterized in that, The concentration of the calcium salt aqueous solution is 2 wt%.

7. The method for preparing the piezoelectric dual-network hydrogel coating modified titanium material according to claim 4, characterized in that, The calcium salt is selected from one or more of Ca(OH)2, CaCO3, CaO, CaO2, and CaCl2.

8. The method for preparing the piezoelectric dual-network hydrogel coating modified titanium material according to claim 4, characterized in that, The selected photoinitiator is either I2959 or LAP.

9. The application of a piezoelectric dual-network hydrogel-coated modified titanium material according to any one of claims 1-3 or a piezoelectric dual-network hydrogel-coated modified titanium material prepared by the preparation method according to any one of claims 4-8 in the preparation of bone graft materials and bone repair materials.

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