Magnetoelectric piezoelectric composite hydrogel, preparation method and application thereof

Abstract

This invention discloses a magnetron piezoelectric composite hydrogel and a method for preparing the composite hydrogel, comprising: modifying barium titanate with tannic acid to prepare tannic acid-functionalized barium titanate nanoparticles; modifying superparamagnetic Fe3O4 nanoparticles with carboxyl-terminated polyethylene glycol to obtain carboxylated superparamagnetic nanoparticles; uniformly dispersing the tannic acid-functionalized barium titanate nanoparticles and carboxylated superparamagnetic nanoparticles in deionized water to form a suspension, and then adding polyvinyl alcohol and glycerol to react and obtain the magnetron piezoelectric composite hydrogel. This invention also discloses the application of the above hydrogel in promoting the repair of peripheral nerve injuries. The composite hydrogel of this invention can remotely, non-invasively, and precisely convert mechanical stress into electrical signals that promote nerve regeneration, and can also exert anti-inflammatory and antioxidant stress-regulating microenvironment functions, providing a powerful intelligent platform for the functional regeneration of peripheral nerves.

Description

Technical Field

[0001] This invention belongs to the field of biomedical materials technology, and relates to a composite hydrogel with magnetic responsiveness and piezoelectric effect. This invention also relates to the preparation method and application of the composite hydrogel. Background Technology

[0002] Peripheral nerve injury is a common clinical condition, and its regeneration and functional recovery pose significant medical challenges. Autologous nerve transplantation is the gold standard, but it suffers from drawbacks such as limited donor availability and the risk of secondary injury. Biomaterial-based nerve conduits offer an alternative; however, existing material systems generally have the following limitations: First, simple physical support or static release of biochemical factors cannot simulate the dynamic microenvironment required for nerve regeneration. Second, although using piezoelectric materials to convert in vivo mechanical energy into endogenous electrical signals is a cutting-edge strategy, once these implants are placed in the body, the intensity, mode of action, and duration of the generated electrical signals are determined by the material's inherent properties and fixed physiological activities, making real-time, precise external regulation impossible according to the different needs of the repair stage. This "implantation-as-it-is" approach lacks the ability to intervene in the temporal sequence of this complex biological process of nerve regeneration.

[0003] In recent years, researchers have attempted to introduce magnetically responsive components to endow materials with remote manipulation capabilities. However, the functions of existing magnetically responsive materials are mostly limited to simple mechanical stimulation or spatial navigation, and they have not yet been able to be organically combined with the piezoelectric effect, let alone achieve programmable, non-invasive, and precise remote control of piezoelectric output performance (including intensity, frequency, and duration). The neural regeneration process involves multiple stages, each of which may have different requirements for the microenvironment (including electrical signals). Therefore, developing a smart material that can not only provide bioelectric stimulation but also remotely, in real-time, and precisely control the electrical stimulation parameters after implantation through external non-invasive means (such as magnetic fields) is crucial for achieving personalized and adaptive neural repair.

[0004] However, existing piezoelectric nerve repair materials still have the following limitations: (1) Traditional piezoelectric ceramic particles (such as BaTiO3) tend to agglomerate in the polymer matrix, resulting in poor dispersion and weak interfacial bonding, which affects the piezoelectric output efficiency and material uniformity; (2) The material has a single function and lacks the ability to actively regulate the damage microenvironment (such as oxidative stress and inflammation); (3) It lacks targeting and controllability, making it difficult to achieve precise treatment.

[0005] Therefore, designing a novel neural repair material that couples magnetic responsiveness with piezoelectric effect through innovative composite material composition and structural design to achieve remote, non-invasive, precise control and microenvironment improvement has significant innovative significance and clinical value. Summary of the Invention

[0006] The purpose of this invention is to provide a magnetron piezoelectric composite hydrogel that has high biocompatibility, allows for remote, non-invasive, and precise control of electrical signals, and also possesses anti-inflammatory and antioxidant properties.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned composite hydrogel.

[0008] A third objective of this invention is to provide the application of the aforementioned composite hydrogel in promoting the repair of peripheral nerve injuries.

[0009] The technical solution adopted in this invention is a method for preparing magnetron piezoelectric composite hydrogels, specifically implemented according to the following steps: Step 1: Modify barium titanate with tannic acid to prepare tannic acid-functionalized barium titanate nanoparticles; Step 2: Modify superparamagnetic Fe3O4 nanoparticles with carboxyl-terminated polyethylene glycol to obtain carboxylated superparamagnetic nanoparticles; Step 3: The tannic acid-functionalized barium titanate nanoparticles prepared in Step 1 and the carboxylated superparamagnetic nanoparticles prepared in Step 2 are uniformly dispersed in deionized water to form a suspension. Then, polyvinyl alcohol and glycerol are added to react and obtain a magnetron piezoelectric composite hydrogel.

[0010] The invention is further characterized by: Step 1 is as follows: Barium titanate nanoparticles were added to a hydrogen peroxide solution and reacted at a constant temperature of 100-120℃ for 3-5 hours. After the reaction was completed and cooled to room temperature, the resulting suspension was centrifuged, the precipitate was washed and dried, and then ground to obtain hydroxylated barium titanate powder. The hydroxylated barium titanate powder was mixed with tannic acid and uniformly dispersed in deionized water. 10% Tris-HCl buffer was added dropwise to adjust the pH of the mixed solution to 8.0-9.0. The mixture was then stirred and reacted at room temperature in the dark for 24-36 hours. After the reaction was completed, the resulting suspension was centrifuged, the precipitate was washed and dried to obtain tannic acid-functionalized barium titanate nanoparticles.

[0011] In step 1, the concentration of hydrogen peroxide solution is 20-40 wt%, the mass-to-volume ratio of barium titanate nanoparticles to hydrogen peroxide solution is 1:(5-15) g / mL, and the mass ratio of hydroxylated barium titanate powder to tannic acid is 1:1-2.

[0012] The centrifugation, washing, and drying process in the preparation of barium titanate hydroxylated powder is as follows: the obtained suspension is centrifuged at 8000 rpm for 5-10 min, the supernatant is discarded, the precipitate is resuspended with deionized water and centrifuged and washed multiple times, and then the precipitate is vacuum dried at 60-70℃ for 12-24 hours to obtain barium titanate hydroxylated powder. The centrifugation, washing, and drying process in the preparation of tannic acid-functionalized barium titanate nanoparticles is as follows: the suspension is centrifuged at 10,000 rpm for 8-10 min to collect the solid product, resuspended and washed multiple times with deionized water, and then the solid is vacuum dried at 60-70℃ for 12-24 hours to obtain tannic acid-functionalized barium titanate nanoparticles.

[0013] Step 2 is as follows: Carboxyl-terminated polyethylene glycol was added to an aqueous dispersion of superparamagnetic Fe3O4 nanoparticles, followed by the addition of a carbodiimide condensing agent and its auxiliary activator. The mixture was stirred at 20-40°C for 6-24 hours. After the reaction, the magnetic particles were separated and preliminarily washed, followed by centrifugation and a second washing. The purified concentrate was then diluted with deionized water to obtain an aqueous dispersion of carboxylated superparamagnetic nanoparticles with a concentration of 10-15 mg / mL.

[0014] In step 2, the mass of carboxyl-terminated polyethylene glycol is 1-10 times the mass of Fe3O4 nanoparticles, the mass of carbodiimide condensing agent is 0.2-2 times the mass of carboxyl-terminated polyethylene glycol, and the mass of auxiliary activator is 0.2-2 times the mass of carboxyl-terminated polyethylene glycol.

[0015] In step 2, the specific process for treating the reaction solution after the reaction is completed is as follows: Place the reaction solution next to a neodymium iron boron magnet and let it stand for 10-20 minutes to allow the magnetic particles to be completely adsorbed onto the reaction vessel wall. Discard the supernatant, add MES buffer, gently shake to resuspend the particles, and repeat this magnetic separation and resuspension process several times. Transfer the preliminarily washed particle dispersion to an ultrafiltration centrifuge tube and centrifuge at 4000g for 20-30 minutes to concentrate the system. Then add deionized water to dilute and centrifuge again to concentrate. Repeat this process several times to obtain the purified concentrate.

[0016] Step 3 specifically involves: Tannic acid-functionalized barium titanate nanoparticles and carboxylated superparamagnetic nanoparticles were mixed at a dry weight ratio of 2-10:1 and dispersed in an aqueous medium. The mixture was homogenized by ultrasonic treatment with a power of 100-500W in an intermittent pulse mode for a total treatment time of 15-20 minutes to obtain a uniform and stable composite nanofiller suspension. Polyvinyl alcohol and glycerol were added to the suspension to form a gel precursor solution, wherein the mass concentration of polyvinyl alcohol in the gel precursor solution was 5-20%, and the mass ratio of glycerol to polyvinyl alcohol was 5-15:1. The mixture was stirred at 110-130℃ for 2-5 hours to form a uniform pregel solution. The pregel solution was degassed, poured into a mold, and allowed to stand at room temperature for 2-4 hours to solidify, thus obtaining a magnetron piezoelectric composite hydrogel.

[0017] Another technical solution adopted in this invention is a magnetron piezoelectric composite hydrogel, which is prepared by the above method.

[0018] The third technical solution adopted in this invention is the application of the above-mentioned magnetron piezoelectric composite hydrogel in promoting the repair of peripheral nerve injuries.

[0019] The beneficial effects of this invention are: This invention utilizes tannic acid to functionalize barium titanate, giving the barium titanate particles good dispersibility and endowing them with antioxidant and anti-inflammatory bioactivity. Superparamagnetic Fe3O4 nanoparticles are modified with carboxyl-terminated polyethylene glycol (COOH-PEG-NH2), resulting in COOH-PEG-SPIONs with good dispersibility. The surface carboxyl groups can interact with PVA chains, enhancing interfacial bonding. Furthermore, the addition of glycerol to PVA increases the content of intermolecular hydrogen bonds and non-centrosymmetric structures, thereby enhancing the permanent dipole moment of the molecular chains. Mechanical stress is transferred to the -OH groups of PVA and glycerol chains through intermolecular hydrogen bonds, leading to changes in dipole moment and forming a potential gradient along the compression direction. Combining these two functionalized nanoparticles with a polymer matrix synthesizes a magnetron piezoelectric composite hydrogel with excellent physicochemical properties, superior magnetic properties, and a significant piezoelectric effect. When this hydrogel is implanted into the peripheral nerves, the material can be non-invasively and precisely manipulated through an external dynamic magnetic field. The magnetic force generates a piezoelectric effect through barium titanate particles, producing an electrical signal that regulates the regeneration of damaged nerves. At the same time, it has anti-inflammatory and antioxidant effects, promoting the repair of peripheral nerves after injury. Attached Figure Description

[0020] Figure 1 This is a scanning electron microscope image of the hydrogel prepared in Example 1 of the present invention; Figure 2 This is a diagram showing the pore size of the hydrogel prepared in Example 1 of the present invention; Figure 3 This is the energy spectrum of the hydrogel prepared in Example 1 of this invention; Figure 4 These are the energy dispersive X-ray spectra of the hydrogels prepared in Comparative Examples 1, 2 and 1 of this invention; Figure 5 This is the hysteresis curve of the hydrogel prepared in Example 1 of the present invention; Figure 6 This is an experimental diagram showing the repeated folding and recovery properties of the hydrogel material prepared in Example 1 in water; Figure 7 This is a time-voltage waveform diagram of the hydrogel material prepared in Example 1; Figure 8 This is a comparison chart of muscle size in different groups; Figure 9These are immunofluorescence staining images of different groups of nerve cells; Figure 10 This is a statistical analysis chart of the sciatic nerve function index for different groups; Figure 11 This is a comparison chart of the anti-inflammatory effects of different groups. Detailed Implementation

[0021] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0022] The preparation method of the magnetron piezoelectric composite hydrogel of the present invention is carried out according to the following steps: Step 1: Preparation of tannic acid-functionalized barium titanate nanoparticles Barium titanate nanoparticles were added to an aqueous solution of hydrogen peroxide, with a hydrogen peroxide concentration of 20-40 wt% and a mass-to-volume ratio of barium titanate nanoparticles to hydrogen peroxide solution of 1:(5-15) g / mL. The mixture was placed in a high-pressure reactor and reacted at 100-120℃ for 3-5 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting suspension was centrifuged at 8000 rpm for 5-10 minutes, and the supernatant was carefully discarded. The precipitate was resuspended in deionized water and washed by centrifugation, a process repeated three times. The final precipitate was transferred to a petri dish and dried in a vacuum drying oven at 60-70℃ for 12-24 hours. After grinding, hydroxylated barium titanate powder was obtained.

[0023] The hydroxylated barium titanate powder obtained above was mixed with tannic acid at a mass ratio of 1:(1-2) and dispersed in deionized water (1g barium titanate dispersed in 5-10mL deionized water) to form a mixed dispersion. The mixture was initially stirred evenly using a magnetic stirrer. 10% Tris-HCl buffer was added dropwise, and the pH of the mixed solution was monitored and adjusted to 8.0-9.0 using a pH meter. The reaction was then carried out under light-protected conditions at room temperature with continuous stirring for 24-36 hours. After the reaction was complete, the suspension was centrifuged at 10000rpm for 8-10 minutes to collect the solid product. The solid was resuspended in deionized water and washed three times to completely remove physically adsorbed free tannic acid. The washed solid was vacuum dried overnight at 60-70℃, and then lightly ground in a mortar to obtain tannic acid-functionalized barium titanate nanoparticle powder, which was then sealed and stored for later use.

[0024] Step 2: Preparation of carboxylated superparamagnetic nanoparticles A superparamagnetic iron oxide nanoparticle aqueous dispersion was placed in a reaction vessel, and carboxyl-amino bifunctional polyethylene glycol (COOH-PEG-NH2), specifically carboxyl-terminated polyethylene glycol, was added at an amount 1-10 times the mass of the solid iron oxide nanoparticles. Subsequently, a carbodiimide condensing agent and its auxiliary activator were added, at amounts of 0.2-2 times and 0.1-1 times the mass of the carboxyl-amino bifunctional polyethylene glycol, respectively. The mixed reaction system was placed on a stirrer and stirred continuously for 6-24 hours within a temperature range of 20-40℃. After the reaction was completed, the reaction vessel was placed next to a strong neodymium iron boron magnet and allowed to stand for 10-20 minutes to allow the magnetic particles to be completely adsorbed onto the vessel wall. Then, the supernatant was carefully decanted, an appropriate amount of MES buffer was added, the particles were gently shaken to resuspend, and magnetic separation was performed again, discarding the supernatant. This process was repeated 2-3 times to remove most of the unreacted small molecules. The pre-washed particle dispersion was transferred to an ultrafiltration centrifuge tube and centrifuged at 4000g for 20-30 minutes to concentrate the system. Deionized water was then added for dilution, followed by another centrifugation and concentration. This "dilution-concentration" cycle could be repeated 2-5 times to thoroughly remove residual salts, ungrafted polymers, and reaction byproducts. The final purified concentrate was diluted with an appropriate amount of deionized water to obtain an aqueous dispersion of carboxylated PEG-modified superparamagnetic nanoparticles with a concentration of 10-15 mg / mL, which was stored at 4°C for later use.

[0025] Step 3: Preparation of magnetron piezoelectric hydrogel The tannic acid-functionalized barium titanate nanoparticles prepared in step 1 and the carboxylated superparamagnetic nanoparticles prepared in step 2 were mixed at a dry weight ratio of 2–10:1 and dispersed together in an aqueous medium. The mixture was homogenized by ultrasonic treatment with a power of 100–500 W in an intermittent pulse mode for a total treatment time of 15–20 minutes until a uniform and stable composite nanofiller suspension was obtained.

[0026] Polyvinyl alcohol (PVA) and glycerol are added to the above suspension to form a gel precursor solution, wherein the mass concentration of PVA in the gel precursor solution is 5-20%, and the mass ratio of glycerol to PVA is 5-15:1. The mixture is heated at 110-130℃ and stirred continuously for 2-5 hours until the polymer is completely dissolved, forming a homogeneous pregel solution. After degassing the pregel solution, it is poured into a mold and allowed to stand and solidify at room temperature (20-25℃) for 2-4 hours to form a magnetron piezoelectric composite hydrogel.

[0027] In the preparation method of the magnetron piezoelectric composite hydrogel of the present invention: Step 1 aims to prepare tannic acid-functionalized barium titanate nanoparticles. The core of this step lies in the covalent grafting of the bioactive molecule tannic acid onto the surface of the barium titanate nanoparticles through a surface chemical modification strategy. The principle is as follows: First, barium titanate is hydroxylated using hydrogen peroxide, introducing abundant active hydroxyl groups onto its surface. Subsequently, under weakly alkaline buffer conditions, the catechol / phenolic hydroxyl groups in the tannic acid molecules undergo strong coordination and possible covalent coupling with the hydroxyl groups on the particle surface, thereby achieving robust surface modification.

[0028] The advantages of functionalizing barium titanate with tannic acid are as follows: the tannic acid-modified layer can significantly improve the dispersion stability of nanoparticles in the polymer matrix through steric hindrance and hydrophilicity, which is the physical basis for exerting its uniform piezoelectric effect; at the same time, the intrinsic antioxidant and anti-inflammatory activities derived from tannic acid are directly endowed to the piezoelectric filler, enabling the material to actively neutralize oxidative stress and inflammatory response at the nerve injury site while providing electrical stimulation, thus optimizing the regenerative microenvironment.

[0029] Step 2 aims to prepare carboxylated polyethylene glycol-modified superparamagnetic iron oxide nanoparticles. This step seeks to endow the magnetic nanoparticles with excellent colloidal stability, biocompatibility, and surface reactivity through chemical coupling. The principle is as follows: the carboxyl groups at the ends of the carboxylated polyethylene glycol are activated using a carbodiimide condensing agent to form an active ester intermediate. This intermediate then undergoes a highly efficient amidation reaction with pre-introduced or inherent amino groups on the surface of the magnetic particles, thereby firmly anchoring the polyethylene glycol chains to the particle surface in the form of covalent bonds.

[0030] Modifying superparamagnetic nanoparticles with carboxylated polyethylene glycol (PEG) offers several advantages: the covalently grafted PEG chains effectively prevent aggregation of magnetic particles due to magnetic dipole-dipole interactions through strong steric hindrance, ensuring uniform dispersion in the composite system; the PEG modification layer significantly enhances the biocompatibility of the particles and reduces non-specific protein adsorption; furthermore, the carboxyl groups exposed at the ends of the modification layer provide active sites for further chemical coupling with the gel matrix or loading of biomolecules, enhancing the material's functional scalability.

[0031] Step 3 involves combining the two types of functionalized nanoparticles with a polymer matrix to construct a magnetically-electrically responsive smart hydrogel. The key to this step lies in achieving the synthesis of multifunctional components at the molecular level through an integrated process. The principle is as follows: First, functionalized barium titanate and magnetic nanoparticles are uniformly dispersed in an aqueous phase using the cavitation effect of high-energy ultrasound. Then, under heating and stirring, polyvinyl alcohol particles dissolve, and their molecular chains interact with glycerol molecules and the functional groups on the surface of the dispersed nanoparticles through hydrogen bonds and other interactions to form a homogeneous precursor solution. Finally, during the cooling process, the polyvinyl alcohol chains physically crosslink and, together with the dynamic hydrogen bond network formed between glycerol and nanoparticles, construct a stable three-dimensional gel network.

[0032] The advantages of using this method to prepare composite hydrogels are as follows: the process achieves a highly homogeneous composite of piezoelectricity, magnetic responsiveness, and bioactivity in a single material system, with each component generating a synergistic effect through tight interfacial bonding; the resulting hydrogel can not only convert mechanical stress into electrical signals that promote nerve regeneration, but also respond to external magnetic fields to achieve targeted positioning and manipulation, and can apply controllable mechanical stimulation to the implanted material by adjusting magnetic field parameters (such as frequency and intensity), thereby achieving remote, non-invasive, and precise regulation of multiple repair signals of "magnetism-electricity-microenvironment", providing a powerful intelligent platform for the functional regeneration of peripheral nerves.

[0033] Example 1: Step 1: Preparation of tannic acid-functionalized barium titanate nanoparticles 10 g of barium titanate nanoparticles were added to 100 mL of a 30 wt% hydrogen peroxide aqueous solution. The mixture was placed in a high-pressure reactor and reacted at 100 °C for 4 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting suspension was centrifuged at 8000 rpm for 8 minutes, and the supernatant was carefully discarded. The precipitate was resuspended in deionized water and washed by centrifugation, a process repeated three times. The final precipitate was transferred to a petri dish and dried in a vacuum drying oven at 70 °C for 12 hours. After grinding, hydroxylated barium titanate powder was obtained.

[0034] 10g of hydroxylated barium titanate powder and 15g of tannic acid were mixed and dispersed in 80mL of deionized water to form a mixed dispersion. The mixture was initially stirred evenly using a magnetic stirrer. 10% Tris-HCl buffer was added dropwise, and the pH of the mixed solution was adjusted to 8.0 using a pH meter. The reaction was then carried out under light-protected conditions at room temperature with continuous stirring for 24 hours. After the reaction was completed, the suspension was centrifuged at 10,000 rpm for 10 minutes to collect the solid product. The solid was resuspended in deionized water and washed three times to completely remove the physically adsorbed free tannic acid. The washed solid was vacuum dried overnight at 65℃ and then lightly ground in a mortar to obtain tannic acid-functionalized barium titanate nanoparticle powder, which was then sealed and stored for later use.

[0035] Step 2: Preparation of carboxylated superparamagnetic nanoparticles 2g of superparamagnetic iron oxide nanoparticles were dispersed in water to form an aqueous dispersion, which was then placed in a reaction vessel. 15g of carboxyl-amino bifunctional polyethylene glycol was added; subsequently, 10g of carbodiimide condensing agent and 1g of its auxiliary activator were added. The mixed reaction system was placed on a stirrer and stirred continuously at 40℃ for 24 hours. After the reaction was completed, the reaction vessel was placed next to a strong neodymium iron boron magnet and allowed to stand for 20 minutes to allow the magnetic particles to be completely adsorbed onto the vessel wall. Then, the supernatant was carefully decanted, an appropriate amount of MES buffer was added, the particles were gently shaken to resuspend, and magnetic separation was performed again to discard the supernatant. This process was repeated twice to remove most of the unreacted small molecules. The preliminarily washed particle dispersion was transferred to an ultrafiltration centrifuge tube and centrifuged at 4000g for 25 minutes to concentrate the system. Then, deionized water was added for dilution and centrifugation was performed again for concentration. This "dilution-concentration" cycle was repeated 3 times to thoroughly remove residual salts, ungrafted polymers, and reaction byproducts. The final purified concentrate was diluted with an appropriate amount of deionized water to obtain an aqueous dispersion of carboxylated PEG-modified superparamagnetic nanoparticles, which was stored at 4°C for later use.

[0036] Step 3: Preparation of magnetron piezoelectric hydrogel 10g of tannic acid-functionalized barium titanate nanoparticles prepared in step 1 were mixed with 2g of carboxylated superparamagnetic nanoparticles prepared in step 2 and dispersed together in 30g of water. The mixture was homogenized by ultrasonic treatment at a power of 500W in an intermittent pulse mode for a total treatment time of 20 minutes to obtain a uniform and stable composite nanofiller suspension.

[0037] Add 4g of polyvinyl alcohol and 40g of glycerol to the above suspension to form a gel precursor solution. Heat the mixture at 120°C and stir continuously for 3 hours until the polymer is completely dissolved to form a homogeneous pregel solution. After degassing the pregel solution, pour it into a mold and allow it to stand at room temperature for 3 hours to solidify, thus forming a magnetron piezoelectric composite hydrogel.

[0038] Example 2: Step 1: Preparation of tannic acid-functionalized barium titanate nanoparticles 10 g of barium titanate nanoparticles were added to 50 mL of a 40 wt% hydrogen peroxide aqueous solution. The mixture was placed in a high-pressure reactor and reacted at 120 °C for 3 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting suspension was centrifuged at 8000 rpm for 10 minutes, and the supernatant was carefully discarded. The precipitate was resuspended in deionized water and washed by centrifugation, a process repeated three times. The final precipitate was transferred to a petri dish and dried in a vacuum drying oven at 60 °C for 24 hours. After grinding, hydroxylated barium titanate powder was obtained.

[0039] 10g of hydroxylated barium titanate powder and 10g of tannic acid were mixed and dispersed in 100mL of deionized water to form a mixed dispersion. The mixture was initially stirred evenly using a magnetic stirrer. 10% Tris-HCl buffer was added dropwise, and the pH of the mixture was adjusted to 8.0 using a pH meter. The reaction was then carried out under light-protected conditions at room temperature with continuous stirring for 30 hours. After the reaction was complete, the suspension was centrifuged at 10000rpm for 10 minutes to collect the solid product. The solid was resuspended in deionized water and washed three times to completely remove physically adsorbed free tannic acid. The washed solid was vacuum dried overnight at 70℃, and then lightly ground in a mortar to obtain tannic acid-functionalized barium titanate nanoparticle powder, which was then sealed and stored for later use.

[0040] Step 2, same as in Example 1.

[0041] Step 3, same as in Example 1.

[0042] Example 3: Step 1, same as in Example 1.

[0043] Step 2: Preparation of carboxylated superparamagnetic nanoparticles 2g of superparamagnetic iron oxide nanoparticles were dispersed in water to form an aqueous dispersion, which was then placed in a reaction vessel. 5g of carboxyl-amino bifunctional polyethylene glycol was added; subsequently, 10g of carbodiimide condensing agent and 1g of its auxiliary activator were added. The mixed reaction system was placed on a stirrer and stirred continuously at 20°C for 12 hours. After the reaction, the reaction vessel was placed next to a strong neodymium iron boron magnet and allowed to stand for 15 minutes to allow the magnetic particles to be completely adsorbed onto the vessel wall. The supernatant was then carefully discarded, and an appropriate amount of MES buffer was added. The particles were gently vortexed to resuspend the particles, and magnetic separation was performed again, discarding the supernatant. This process was repeated twice to remove most of the unreacted small molecules. The preliminarily washed particle dispersion was transferred to an ultrafiltration centrifuge tube and centrifuged at 4000g for 25 minutes to concentrate the system. Deionized water was then added for dilution, and the system was centrifuged again for concentration. This "dilution-concentration" cycle was repeated 5 times to thoroughly remove residual salts, ungrafted polymers, and reaction byproducts. The final purified concentrate was diluted with an appropriate amount of deionized water to obtain an aqueous dispersion of carboxylated PEG-modified superparamagnetic nanoparticles, which was stored at 4°C for later use.

[0044] Step 3, same as in Example 1.

[0045] Example 4: Step 1, same as in Example 1.

[0046] Step 2, same as in Example 1.

[0047] Step 3: Preparation of magnetron piezoelectric hydrogel 10g of tannic acid-functionalized barium titanate nanoparticles prepared in step 1 were mixed with 1g of carboxylated superparamagnetic nanoparticles prepared in step 2 and dispersed together in 25g of water. The mixture was homogenized by ultrasonic treatment at a power of 300W in an intermittent pulse mode for a total treatment time of 20 minutes to obtain a uniform and stable composite nanofiller suspension.

[0048] Add 3g of polyvinyl alcohol and 20g of glycerol to the above suspension to form a gel precursor solution. Heat the mixture at 130°C and stir continuously for 5 hours until the polymer is completely dissolved to form a homogeneous pregel solution. After degassing the pregel solution, pour it into a mold and allow it to stand at room temperature for 4 hours to solidify, thus forming a magnetron piezoelectric composite hydrogel.

[0049] Example 5: Step 1: Preparation of tannic acid-functionalized barium titanate nanoparticles 10 g of barium titanate nanoparticles were added to 150 mL of a 20 wt% hydrogen peroxide aqueous solution. The mixture was placed in a high-pressure reactor and reacted at 110 °C for 4 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting suspension was centrifuged at 8000 rpm for 5 minutes, and the supernatant was carefully discarded. The precipitate was resuspended in deionized water and washed by centrifugation, a process repeated three times. The final precipitate was transferred to a petri dish and dried in a vacuum drying oven at 65 °C for 20 hours. After grinding, hydroxylated barium titanate powder was obtained.

[0050] 10g of hydroxylated barium titanate powder and 20g of tannic acid were mixed and dispersed in 100mL of deionized water to form a mixed dispersion. The mixture was initially stirred evenly using a magnetic stirrer. 10% Tris-HCl buffer was added dropwise, and the pH of the mixed solution was adjusted to 9.0 using a pH meter. The reaction was then carried out under light-protected conditions at room temperature with continuous stirring for 36 hours. After the reaction was completed, the suspension was centrifuged at 10,000 rpm for 10 minutes to collect the solid product. The solid was resuspended in deionized water and washed three times to completely remove the physically adsorbed free tannic acid. The washed solid was vacuum dried overnight at 60℃ and then lightly ground in a mortar to obtain tannic acid-functionalized barium titanate nanoparticle powder, which was then sealed and stored for later use.

[0051] Step 2, same as in Example 1.

[0052] Step 3, same as in Example 1.

[0053] Example 6: Step 1, same as in Example 1.

[0054] Step 2: Preparation of carboxylated superparamagnetic nanoparticles 2g of superparamagnetic iron oxide nanoparticles were dispersed in water to form an aqueous dispersion, which was then placed in a reaction vessel. 20g of carboxyl-amino bifunctional polyethylene glycol was added; subsequently, 5g of carbodiimide condensing agent and 3g of its auxiliary activator were added. The mixed reaction system was placed on a stirrer and stirred continuously at 30°C for 18 hours. After the reaction, the reaction vessel was placed next to a strong neodymium iron boron magnet and allowed to stand for 10 minutes to allow the magnetic particles to be completely adsorbed onto the vessel wall. The supernatant was then carefully discarded, and an appropriate amount of MES buffer was added. The particles were gently vortexed to resuspend the particles, and magnetic separation was performed again, discarding the supernatant. This process was repeated 3 times to remove most of the unreacted small molecules. The preliminarily washed particle dispersion was transferred to an ultrafiltration centrifuge tube and centrifuged at 4000g for 20 minutes to concentrate the system. Deionized water was then added for dilution, and the system was centrifuged again for concentration. This "dilution-concentration" cycle was repeated 5 times to thoroughly remove residual salts, ungrafted polymers, and reaction byproducts. The final purified concentrate was diluted with an appropriate amount of deionized water to obtain an aqueous dispersion of carboxylated PEG-modified superparamagnetic nanoparticles, which was stored at 4°C for later use.

[0055] Step 3, same as in Example 1.

[0056] Comparative Example 1: This comparative example prepared the original hydrogel PG, i.e., a hydrogel without barium titanate nanoparticles and superparamagnetic nanoparticles. The preparation process was the same as step 3 in Example 1, specifically: Mix 4g of polyvinyl alcohol and 40g of glycerol, heat at 120°C and stir continuously for 3 hours to form a homogeneous pregel solution. After degassing the pregel solution, pour it into a mold and allow it to stand at room temperature for 3 hours to solidify, forming a hydrogel.

[0057] Comparative Example 2: This comparative example prepared a hydrogel PGT containing only barium titanate nanoparticles and no superparamagnetic nanoparticles. The preparation process was the same as steps 1 and 3 in Example 1, specifically: Step 1: Preparation of tannic acid-functionalized barium titanate nanoparticles 10 g of barium titanate nanoparticles were added to 100 mL of a 30 wt% hydrogen peroxide aqueous solution. The mixture was placed in a high-pressure reactor and reacted at 100 °C for 4 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting suspension was centrifuged at 8000 rpm for 8 minutes, and the supernatant was carefully discarded. The precipitate was resuspended in deionized water and washed by centrifugation, a process repeated three times. The final precipitate was transferred to a petri dish and dried in a vacuum drying oven at 70 °C for 12 hours. After grinding, hydroxylated barium titanate powder was obtained.

[0058] 10g of hydroxylated barium titanate powder and 15g of tannic acid were mixed and dispersed in 80mL of deionized water to form a mixed dispersion. The mixture was initially stirred evenly using a magnetic stirrer. 10% Tris-HCl buffer was added dropwise, and the pH of the mixed solution was adjusted to 8.0 using a pH meter. The reaction was then carried out under light-protected conditions at room temperature with continuous stirring for 24 hours. After the reaction was completed, the suspension was centrifuged at 10,000 rpm for 10 minutes to collect the solid product. The solid was resuspended in deionized water and washed three times to completely remove the physically adsorbed free tannic acid. The washed solid was vacuum dried overnight at 65℃ and then lightly ground in a mortar to obtain tannic acid-functionalized barium titanate nanoparticle powder, which was then sealed and stored for later use.

[0059] Step 2: Preparation of magnetron piezoelectric hydrogel 10g of the tannic acid-functionalized barium titanate nanoparticles prepared in step 1 were dispersed in 30g of water. The mixed dispersion was homogenized by ultrasonic treatment with an ultrasonic power of 500W and an intermittent pulse mode. The total treatment time was 20 minutes to obtain a uniform and stable nanofiller suspension.

[0060] Add 4g of polyvinyl alcohol and 40g of glycerol to the above suspension to form a gel precursor solution. Heat the mixture at 120°C and stir continuously for 3 hours until the polymer is completely dissolved, forming a homogeneous pregel solution. After degassing the pregel solution, pour it into a mold and allow it to stand at room temperature for 3 hours to solidify, thus forming a composite hydrogel.

[0061] The hydrogels prepared in the embodiments and comparative examples of the present invention were subjected to the following performance tests: like Figure 1 and Figure 2 The images shown are scanning electron microscope (SEM) images and pore size diagrams of the hydrogel prepared in Example 1. It can be seen that the hydrogel of the present invention exhibits a porous network structure with uniform pore size, and the average pore size is 360±147.20μm.

[0062] like Figure 3 As shown, this is the energy spectrum of the hydrogel prepared in Example 1. Figure 4 The figures show the energy dispersive X-ray spectra of the hydrogel PG prepared in Comparative Example 1, the hydrogel PGT prepared in Comparative Example 2, and the hydrogel PGTF prepared in Example 1. It can be seen from these two figures that the hydrogel PGTF of the present invention contains Ti, Fe and Ba elements, indicating that the material has been successfully modified.

[0063] like Figure 5 As shown, the hysteresis curve of the hydrogel prepared in Example 1 can be seen, indicating that the hydrogel material of the present invention has good magnetic responsiveness.

[0064] Figure 6The experimental diagram shows the repeated folding and recovery characteristics of the hydrogel material prepared in Example 1 in water. It can be seen that the hydrogel material of the present invention can still recover after 100 folds, which proves that it has excellent fatigue resistance and repeated deformation ability.

[0065] Figure 7 The time-voltage waveform of the hydrogel material prepared in Example 1 shows that the material generates a dynamic voltage after periodic magnetic stimulation, proving that the material has a good magneto-piezoelectric effect.

[0066] Figure 8 The figures show a comparison of muscle size in different groups. Autologous transplantation, using rat sciatic nerve, served as the clinical gold standard and control. The PG catheter and magnetically responsive nerve scaffold were fabricated from the PG hydrogel prepared in Comparative Example 1 and the magnetically responsive PGTF hydrogel prepared in Example 1, respectively. The severed nerve ends were connected using these two types of scaffolds, and the atrophy of the target muscle was observed. Less atrophy indicated better nerve function recovery. The figures show that the gastrocnemius muscle atrophy in the magnetically responsive nerve scaffold treatment group was significantly less than that in the PG catheter treatment group. Although mild atrophy still existed compared to the autologous transplantation group, it significantly improved the post-injury denervation atrophy state.

[0067] Figure 9 The immunofluorescence staining images of the nerves show that the density of regenerated nerve fibers at the site of sciatic nerve injury in rats treated with magnetically responsive nerve scaffolds was significantly increased, and the integrity and maturity of myelin regeneration (remyelination) were significantly better than those in the PG catheter treatment group. Although its nerve regeneration and repair effect was slightly inferior to that of the autologous nerve transplantation (gold standard) group, it showed good repair characteristics in terms of the regularity of the arrangement of regenerated fibers and the efficiency of myelin sheath encapsulation.

[0068] Figure 10 The statistical analysis of the sciatic nerve function index (SFI) shows that the SFI values ​​at 4, 8, and 12 weeks post-surgery exhibit a consistent time-dependent recovery trend. The SFI values ​​at each time point in the magnetically responsive nerve scaffold treatment group were significantly higher than those in the PG catheter group, and continued to increase over time. Although the SFI values ​​at each time point were slightly lower than those in the autologous transplantation group, the gap in functional recovery between the two groups gradually narrowed over time. This indicates that the magnetically responsive nerve scaffold can effectively promote structural reconstruction and motor function recovery after sciatic nerve transverse injury, and its repair effect is significantly better than that of PG catheter treatment.

[0069] Figure 11The figure shows a comparison of the anti-inflammatory effects of the three groups of experiments. It can be seen that the expression levels of pro-inflammatory factors IL-6, IL-1β, and TNF-α at the injury site were significantly reduced in the magnetically responsive neural scaffold treatment group, and the inflammatory response was effectively suppressed. The anti-inflammatory effect was significantly better than that of the PG catheter treatment group. However, the anti-inflammatory indicators of the autologous transplantation group were not significantly different from those of the PG catheter group, and no significant anti-inflammatory effect was observed.

Claims

1. The preparation method of the magnetron piezoelectric composite hydrogel is carried out according to the following steps: Step 1: Modify barium titanate with tannic acid to prepare tannic acid-functionalized barium titanate nanoparticles; Step 2: Modify superparamagnetic Fe3O4 nanoparticles with carboxyl-terminated polyethylene glycol to obtain carboxylated superparamagnetic nanoparticles; Step 3: The tannic acid-functionalized barium titanate nanoparticles prepared in Step 1 and the carboxylated superparamagnetic nanoparticles prepared in Step 2 are uniformly dispersed in deionized water to form a suspension. Then, polyvinyl alcohol and glycerol are added to react and obtain a magnetron piezoelectric composite hydrogel.

2. The preparation method of the magnetron piezoelectric composite hydrogel according to claim 1, characterized in that, Step 1 is as follows: Barium titanate nanoparticles were added to a hydrogen peroxide solution and reacted at a constant temperature of 100-120℃ for 3-5 hours. After the reaction was completed and cooled to room temperature, the resulting suspension was centrifuged, the precipitate was washed and dried, and then ground to obtain hydroxylated barium titanate powder. The hydroxylated barium titanate powder was mixed with tannic acid and uniformly dispersed in deionized water. 10% Tris-HCl buffer was added dropwise to adjust the pH of the mixed solution to 8.0-9.

0. The mixture was then stirred and reacted at room temperature in the dark for 24-36 hours. After the reaction was completed, the resulting suspension was centrifuged, the precipitate was washed and dried to obtain tannic acid-functionalized barium titanate nanoparticles.

3. The preparation method of the magnetron piezoelectric composite hydrogel according to claim 2, characterized in that, In step 1, the concentration of the hydrogen peroxide solution is 20-40 wt%, the mass-to-volume ratio of barium titanate nanoparticles to hydrogen peroxide solution is 1:(5-15) g / mL, and the mass ratio of the hydroxylated barium titanate powder to tannic acid is 1:1-2.

4. The preparation method of the magnetron piezoelectric composite hydrogel according to claim 2, characterized in that, The centrifugation, washing, and drying process in the preparation of the hydroxylated barium titanate powder is as follows: the obtained suspension is centrifuged at 8000 rpm for 5-10 min, the supernatant is discarded, the precipitate is resuspended with deionized water and centrifuged and washed multiple times, and then the precipitate is vacuum dried at 60-70℃ for 12-24 hours to obtain hydroxylated barium titanate powder. The centrifugation, washing, and drying process in the preparation of tannic acid-functionalized barium titanate nanoparticles is as follows: the suspension is centrifuged at 10,000 rpm for 8-10 min to collect the solid product, resuspended and washed multiple times with deionized water, and then the solid is vacuum dried at 60-70℃ for 12-24 hours to obtain tannic acid-functionalized barium titanate nanoparticles.

5. The method for preparing the magnetron piezoelectric composite hydrogel according to claim 1, characterized in that, Step 2 is as follows: Carboxyl-terminated polyethylene glycol was added to an aqueous dispersion of superparamagnetic Fe3O4 nanoparticles, followed by the addition of a carbodiimide condensing agent and its auxiliary activator. The mixture was stirred at 20-40°C for 6-24 hours. After the reaction, the magnetic particles were separated and preliminarily washed, followed by centrifugation and a second washing. The purified concentrate was then diluted with deionized water to obtain an aqueous dispersion of carboxylated superparamagnetic nanoparticles with a concentration of 10-15 mg / mL.

6. The method for preparing the magnetron piezoelectric composite hydrogel according to claim 5, characterized in that, In step 2, the mass of the carboxyl-terminated polyethylene glycol is 1-10 times the mass of the Fe3O4 nanoparticles, the mass of the carbodiimide condensing agent is 0.2-2 times the mass of the carboxyl-terminated polyethylene glycol, and the mass of the auxiliary activator is 0.2-2 times the mass of the carboxyl-terminated polyethylene glycol.

7. The method for preparing the magnetron piezoelectric composite hydrogel according to claim 5, characterized in that, In step 2, the specific process for treating the reaction solution after the reaction is completed is as follows: Place the reaction solution next to a neodymium iron boron magnet and let it stand for 10-20 minutes to allow the magnetic particles to be completely adsorbed onto the reaction vessel wall. Discard the supernatant, add MES buffer, gently shake to resuspend the particles, and repeat this magnetic separation and resuspension process several times. Transfer the preliminarily washed particle dispersion to an ultrafiltration centrifuge tube and centrifuge at 4000g for 20-30 minutes to concentrate the system. Then add deionized water to dilute and centrifuge again to concentrate. Repeat this process several times to obtain the purified concentrate.

8. The method for preparing the magnetron piezoelectric composite hydrogel according to claim 1, characterized in that, Step 3 specifically involves: Tannic acid-functionalized barium titanate nanoparticles and carboxylated superparamagnetic nanoparticles were mixed at a dry weight ratio of 2-10:1 and dispersed in an aqueous medium. The mixture was homogenized by ultrasonic treatment with a power of 100-500W in an intermittent pulse mode for a total treatment time of 15-20 minutes to obtain a uniform and stable composite nanofiller suspension. Polyvinyl alcohol and glycerol were added to the suspension to form a gel precursor solution, wherein the mass concentration of polyvinyl alcohol in the gel precursor solution was 5-20%, and the mass ratio of glycerol to polyvinyl alcohol was 5-15:

1. The mixture was stirred at 110-130℃ for 2-5 hours to form a uniform pregel solution. The pregel solution was degassed, poured into a mold, and allowed to stand at room temperature for 2-4 hours to solidify, thus obtaining a magnetron piezoelectric composite hydrogel.

9. A magnetron-controlled piezoelectric composite hydrogel, characterized in that, It is prepared by the method described in any one of claims 1-8.

10. The application of the magnetron piezoelectric composite hydrogel as described in any one of claims 1-9 in promoting the repair of peripheral nerve injuries.

Images