A Piezoelectric / Conductive Integrated Hydrogel for Skull Defect Repair and Its Application

Abstract

The present invention belongs to the technical field of hydrogels, and relates to a piezoelectric / conductive integrated hydrogel for skull defect repair, which is prepared by ultraviolet cross-linking of methacrylated protein, zwitterionic monomer and titanate-based piezoelectric particles under the action of a cross-linking agent and a photoinitiator. The piezoelectric / conductive integrated hydrogel provided by the present invention can realize the piezoelectric and conductive functions of the hydrogel, and can effectively promote the proliferation, differentiation and mineralization of bone cells under the action of an electric field, accelerate bone tissue repair, and has a more significant bone regeneration effect than the non-electric stimulation materials in the prior art.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogels, and specifically relates to a piezoelectric / conductive integrated hydrogel for skull defect repair and its application. Background Art

[0002] Skull defects are usually caused by various reasons such as trauma, tumor resection, infection, congenital malformations, etc. Repairing these defects is an important issue in clinical treatment. Traditional methods for skull defect repair mainly rely on metals, ceramics or synthetic polymer materials. Although these materials have certain mechanical strength, they often lack bioactivity, cannot effectively promote the growth and differentiation of bone cells, and may cause immune rejection or chronic inflammatory reactions. Therefore, developing a material that has both biocompatibility and can promote bone tissue repair has become a research hotspot in current medicine and materials science.

[0003] In recent years, the application of piezoelectric / conductive materials in the biomedical field has received extensive attention. Especially in bone repair, piezoelectric and conductive materials can stimulate cell growth, differentiation and bone formation through the action of an electric field, thereby promoting bone healing. As an ideal biomaterial, hydrogels have been widely used in the fields of soft tissue repair and wound dressings due to their excellent biocompatibility, flexibility, adjustable properties and high water hydration. The integrated hydrogel combining piezoelectricity and conductivity can more effectively enhance the response of organisms to electrical stimulation, becoming an important direction for a new generation of bone repair materials.

[0004] Protein materials have been widely used in biomedical materials in recent years due to their good biocompatibility and biodegradability. Silk fibroin, collagen and fibrin are common bio-protein materials. After being modified by methacrylation, these protein materials can enhance their compatibility and cross-linking performance with other monomers, thereby obtaining a more stable hydrogel system with mechanical strength. Methacrylated proteins play a scaffolding role in the hydrogel, providing a good growth environment for cells and promoting cell adhesion, proliferation and differentiation.

[0005] Zwitterionic monomers usually have the characteristics of carrying both positive and negative charges, and can provide additional charge effects in the hydrogel to regulate the electrical properties and biocompatibility of the hydrogel. Zwitterionic monomers can not only improve the mechanical properties of the hydrogel, but also enhance the response ability of the hydrogel to the electric field through their charge characteristics, which is crucial for the bioelectric stimulation effect of the piezoelectric / conductive integrated hydrogel. Existing studies have shown that hydrogel materials containing zwitterionic monomers can activate intracellular signal pathways under the action of a local electric field and promote bone tissue regeneration.

[0006] Piezoelectric particles such as barium titanate, strontium titanate, and barium strontium titanate have excellent piezoelectric properties, that is, they can generate electric charges when an external force is applied and can generate mechanical deformation under the action of an electric field. This property gives piezoelectric particles unique advantages in stimulating cell growth and accelerating tissue repair. Piezoelectric particles based on titanates are widely used in sensors, energy harvesting, and biomedical fields. In particular, research on promoting bone repair has shown that piezoelectric materials can accelerate the proliferation, differentiation, and mineralization of bone cells through the dual stimulation of mechanical force and electrical signals, thereby improving the healing rate of bone tissue.

[0007] Through the combination of these materials, the piezoelectric / conductive hydrogel can not only meet the repair requirements in terms of biocompatibility and degradability, but also accelerate the bone repair process through its electrical properties, providing a new technical approach for the repair of cranial defects. Summary of the Invention

[0008] One of the objectives of the present invention is to provide a piezoelectric / conductive integrated hydrogel that simultaneously has piezoelectric and conductive properties and promotes the repair of cranial defects. The piezoelectric / conductive integrated hydrogel is prepared by ultraviolet cross-linking of methacrylated protein, zwitterionic monomer, and piezoelectric particles based on titanates under the action of a cross-linking agent and a photoinitiator. The mass fractions of methacrylated protein, zwitterionic monomer, piezoelectric particles based on titanates, cross-linking agent, and photoinitiator in the hydrogel are 1.0% - 10%, 1.0% - 10%, 1.0% - 10%, 0.1% - 1%, and 0.1% - 0.5% respectively.

[0009] Preferably, the methacrylated protein is one or more of methacrylated silk fibroin, methacrylated collagen, and methacrylated fibrin.

[0010] Preferably, the zwitterionic monomer is one or more of 2-methacryloyloxyethyl phosphorylcholine, 1-propylsulfonic acid-3-vinylimidazolium inner salt, 2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl), and 2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) ammonium hydroxide.

[0011] Preferably, the piezoelectric particles based on titanates are one or more of barium titanate, strontium titanate, barium strontium titanate, and calcium barium titanate.

[0012] Preferably, the cross-linking agent is one or more of polyethylene glycol diacrylate, N,N'-methylenebisacrylamide, diglycerol dimethacrylate, divinyl acrylate, divinylacrylic acid, and bisacrylamide.

[0013] Preferably, the photoinitiator is one or more of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, lithium phenyl-2,4,6-trimethylbenzoylphosphinate, diphenylacetone, 2,2-dimethyl-2-phenylpropiophenone, and 1,2-diphenyl-2-styrylacetone.

[0014] Preferably, the mass fractions of the methacrylated protein, zwitterionic monomer, titanate-based piezoelectric particles, crosslinking agent, and photoinitiator in the hydrogel are 4.0% - 8.0%, 5.0% - 10%, 3.0% - 5.0%, 0.1% - 0.4%, and 0.1% - 0.5%, respectively.

[0015] Preferably, the mass fractions of the methacrylated protein, zwitterionic monomer, titanate-based piezoelectric particles, crosslinking agent, and photoinitiator in the hydrogel are 8.0%, 5.0%, 5.0%, 0.1%, and 0.25%, respectively.

[0016] Preferably, the specific preparation steps of the hydrogel are as follows: Add the methacrylated protein, zwitterionic monomer, titanate-based piezoelectric particles, crosslinking agent, and photoinitiator to the PBS solution. After magnetic stirring at room temperature, crosslink the mixture under ultraviolet light to form a piezoelectric / conductive integrated hydrogel.

[0017] Preferably, the wavelength of the ultraviolet light is 365 nm, 395 nm, or 405 nm; the power of the ultraviolet light is 5 W - 6000 W; the crosslinking time of the ultraviolet light is 5 s - 300 s.

[0018] Preferably, the time of the magnetic stirring is 0.5 h - 10 h, and the speed regulation of the magnetic stirring is 300 rpm - 1500 rpm.

[0019] In another preferred embodiment of the present invention, the present invention also provides the application of the hydrogel described in the present invention in the preparation of bone tissue regeneration materials.

[0020] Compared with the prior art, the main advantages of the present invention are as follows:

[0021] 1. The piezoelectric / conductive integrated hydrogel of the present invention can achieve the piezoelectric and conductive functions of the hydrogel by combining the zwitterionic monomer with the titanate-based piezoelectric particles. Under the action of an electric field, it can effectively promote the proliferation, differentiation, and mineralization of bone cells, accelerate bone tissue repair, and has a more significant bone regeneration effect than the non-electrically stimulated materials in the prior art.

[0022] 2. In the piezoelectric / conductive integrated hydrogel of the present invention, the combination of methacrylated protein and titanate-based piezoelectric particles endows the hydrogel with not only good mechanical strength but also certain flexibility, enabling it to better meet the repair requirements of cranial defects and reducing the risk of material rupture or deformation after surgery.

[0023] 3. By adjusting the ratios of methacrylated protein, zwitterionic monomer, and titanate-based piezoelectric particles in the piezoelectric / conductive integrated hydrogel of the present invention, the properties of the hydrogel can be flexibly adjusted, such as electrical properties, mechanical strength, and biodegradation rate. This high tunability enables the hydrogel to provide personalized treatment plans according to the needs of different patients.

[0024] 4. Based on the excellent biocompatibility of methacrylated protein, the piezoelectric / conductive integrated hydrogel of the present invention combines the piezoelectric effect of titanate-based piezoelectric particles and the conductive characteristics after the polymerization of zwitterionic monomers. It integrates the biocompatibility of biomaterials, the electric field stimulation of piezoelectric materials, and the regulation of electrical properties by zwitterionic monomers, possessing multiple functions that traditional single-functional materials do not have, and can provide more comprehensive support and more efficient healing effects during bone repair.

[0025] 5. The piezoelectric / conductive integrated hydrogel material system of the present invention simplifies the cross-linking method and low-temperature synthesis process, making the production process more convenient and cost-effective, and is expected to achieve large-scale production and promotion in clinical applications.

[0026] The concept, specific structure, and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, features, and effects of the present invention. Description of the Drawings

[0027] Figure 1 is the preparation flow chart of the piezoelectric / conductive integrated hydrogel.

[0028] Figure 2 is the SEM image of the methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate piezoelectric / conductive integrated hydrogel.

[0029] Figure 3 is the EDS image of the methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate piezoelectric / conductive integrated hydrogel.

[0030] Figure 4 is the XRD pattern of the methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate piezoelectric / conductive integrated hydrogel and strontium titanate.

[0031] Figure 5is the stress-strain curve of the methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate piezoelectric / conductive integrated hydrogel.

[0032] Figure 6 is the open-circuit voltage under repeated pressing detected by a digital multimeter for the hydrogel of methacrylated silk fibroin (1), methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine hydrogel (2), and methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate piezoelectric / conductive integrated hydrogel (3).

[0033] Figure 7 is the cranial micro-CT image after the methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate piezoelectric / conductive integrated hydrogel is used for cranial defect repair.

[0034] Figure 8 is the statistical chart of the new bone volume fraction after the methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate piezoelectric / conductive integrated hydrogel is used for cranial defect repair. Detailed implementation manners

[0035] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments, but it should not be construed as a limitation of the present invention. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art. The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0036] Example 1 Methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate composite piezoelectric / conductive integrated hydrogel

[0037] (I) Preparation of methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate piezoelectric / conductive integrated hydrogel

[0038] Add 160 mg of methacrylated silk fibroin, 100 mg of 2-methacryloyloxyethyl phosphorylcholine, 100 mg of strontium titanate particles, 2 mg of N,N'-methylenebisacrylamide, and 5 mg of lithium phenyl-2,4,6-trimethylbenzoylphosphinate into 2 mL of PBS, magnetically stir at room temperature at 500 rpm for 1 h, and crosslink with ultraviolet light of 405 nm and 30 W power for 30 s to obtain the methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate composite piezoelectric / conductive integrated hydrogel.

[0039] (II) Characterization of methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate piezoelectric / conductive integrated hydrogel

[0040] (A)Analysis by scanning electron microscopy (SEM): Observe the morphology of the hydrogel under SEM. As Figure 2 shown, the hydrogel has a porous structure, which is beneficial to cell infiltration.

[0041] (B)Analysis by energy dispersive spectroscopy (EDS): During the SEM imaging, perform energy dispersive spectroscopy scanning. As Figure 3 shown, analyze the important elements of the hydrogel, which contains phosphorus (P) from 2-methacryloyloxyethyl phosphorylcholine, titanium (Ti) and strontium (Sr) from strontium titanate, indicating that 2-methacryloyloxyethyl phosphorylcholine and strontium titanate are successfully incorporated into the hydrogel.

[0042] (C)X-ray diffraction (XRD) analysis: Perform X-ray diffraction analysis on the hydrogel and strontium titanate using an X-ray diffractometer. Figure 4 The results show that the XRD pattern of the hydrogel contains the XRD diffraction characteristic peaks of strontium titanate, indicating that strontium titanate is successfully incorporated into the hydrogel.

[0043] (D)Compressive property analysis: Construct the stress-strain curve of the hydrogel by compressing the hydrogel with a mechanical testing machine. As Figure 5 shown, the hydrogel has good elasticity and compressibility.

[0044] (E)Piezoelectric property analysis: Detect the open-circuit voltage generated when repeatedly pressing the hydrogel with a digital multimeter. As Figure 6 shown, it can be found that the open-circuit voltage of the methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine / strontium titanate piezoelectric / conductive integrated hydrogel (3) is significantly higher than that of the methacrylated silk fibroin / 2-methacryloyloxyethyl phosphorylcholine hydrogel (2), reaching 150 mV, indicating that the hydrogel has a piezoelectric effect, and the addition of strontium titanate significantly enhances the piezoelectric effect.

[0045] (F)Skull repair experiment of the hydrogel: Create a 4-mm diameter non-healing skull defect in C57 mice, and use the hydrogel for repair (gel group), use the group without any treatment as the control group (Con group), and use the hydrogel and apply a capacitive electric field of 100 mV / mm, 75 Hz, and a duty cycle of 80% as the hydrogel combined with electric field group (gel+EF group). After 8 weeks of repair, as Figure 6 shown, the repair level of the hydrogel repair group is higher than that of the control group, and the repair effect of the combined electric field group is better.

[0046] (G)Statistical analysis of the newly formed bone volume fraction (BV / TV) for the skull repair situation: As Figure 7As shown, the newly formed bone in the control group was only 2.77±1.11%, significantly lower than 6.85±1.90% in the hydrogel group and 11.12±1.79% in the hydrogel combined with electric field group. This indicates that the methacrylated collagen / [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide / barium titanate piezoelectric / conductive integrated hydrogel accelerates the repair of refractory skull defects in mice, and the repair effect is further accelerated under electric field stimulation.

[0047] Example 2 Preparation of methacrylated collagen / [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide / barium titanate piezoelectric / conductive integrated hydrogel

[0048] Add 50 mg of methacrylated collagen, 100 mg of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 50 mg of barium titanate particles, 2 mg of bisacrylamide, and 5 mg of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone into 1 mL of PBS, magnetically stir at room temperature at 400 rpm for 2 h, and crosslink with ultraviolet light at 365 nm and 20 W power for 25 s to obtain the methacrylated collagen / [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide / barium titanate composite piezoelectric / conductive integrated hydrogel.

[0049] Example 3 Preparation of methacrylated fibrin / 1-propylsulfonic acid-3-vinylimidazolium inner salt / barium strontium titanate piezoelectric / conductive integrated hydrogel

[0050] Add 75 mg of methacrylated collagen, 75 mg of 1-propylsulfonic acid-3-vinylimidazolium inner salt, 40 mg of barium strontium titanate particles, 4 mg of divinyl acrylate, and 4 mg of 2,2-dimethyl-2-phenylpropiophenone into 1 mL of PBS, magnetically stir at room temperature at 600 rpm for 1.5 h, and crosslink with ultraviolet light at 365 nm and 30 W power for 35 s to obtain the methacrylated fibrin / 1-propylsulfonic acid-3-vinylimidazolium inner salt / barium strontium titanate piezoelectric / conductive integrated hydrogel.

[0051] Example 4 Preparation of methacrylated silk fibroin-methacrylated collagen / [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) / barium calcium titanate piezoelectric / conductive integrated hydrogel

[0052] Add 40 mg of methacrylated silk fibroin, 40 mg of methacrylated collagen, 80 mg of 2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl), 60 mg of calcium barium titanate particles, 5 mg of polyethylene glycol diacrylate, and 3 mg of 1,2-diphenyl-2-styrylacetone into 2 mL of PBS. Stir magnetically at room temperature at 500 rpm for 1.5 h, and crosslink with ultraviolet light of 395 nm and 25 W power for 30 s to obtain a methacrylated silk fibroin-methacrylated collagen / 2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl) / calcium barium titanate piezoelectric / conductive integrated hydrogel.

[0053] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations based on the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field according to the concept of the present invention through logical analysis, reasoning, or limited experiments on the basis of the prior art should fall within the protection scope determined by the claims.

Claims

1. A piezoelectric / conductive integrated hydrogel for skull defect repair, which is prepared by ultraviolet cross-linking of methacrylated protein, zwitterionic monomer and titanate-based piezoelectric particles under the action of a cross-linking agent and a photoinitiator. The mass fractions of methacrylated protein, zwitterionic monomer, titanate-based piezoelectric particles, cross-linking agent and photoinitiator in the hydrogel are 8.0%, 5.0%, 5.0%, 0.1% and 0.25% respectively; The methacrylated protein is methacrylated silk fibroin, the zwitterionic monomer is 2-methacryloyloxyethyl phosphorylcholine, and the titanate-based piezoelectric particles are strontium titanate; The specific preparation steps of the hydrogel are as follows: add methacrylated protein, zwitterionic monomer, titanate-based piezoelectric particles, cross-linking agent and photoinitiator into PBS solution, after magnetic stirring at room temperature, cross-link the mixture under ultraviolet light to form a piezoelectric / conductive integrated hydrogel.

2. The hydrogel according to claim 1, characterized in that, The cross-linking agent is one or more of polyethylene glycol diacrylate, N,N'-methylenebisacrylamide, diglycerol dimethacrylate, divinyl acrylate, divinyl acrylic acid and bisacrylamide.

3. The hydrogel according to claim 1, characterized in that, The photoinitiator is one or more of 2-hydroxy-2-methyl-1-[4-(2-hydroxyethoxy)phenyl]-1-propanone, lithium phenyl-2,4,6-trimethylbenzoylphosphinate, diphenylacetophenone, 2,2-dimethyl-2-phenylpropiophenone and 1,2-diphenyl-2-styrylacetone.

4. The hydrogel according to claim 1, characterized in that, The wavelength of the ultraviolet light is 365nm, 395nm or 405nm; the power of the ultraviolet light is 5W - 6000W; the ultraviolet cross-linking time is 5s - 300s.

5. The hydrogel according to claim 1, characterized in that, The magnetic stirring time is 0.5h - 10h, and the speed regulation of the magnetic stirring is 300rpm - 1500rpm.

6. Use of the hydrogel according to any one of claims 1 - 5 in the preparation of bone tissue regeneration materials.

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