Preparation and application of self-piezoelectric aluminum nitride film / cavity assembly structure for promoting repair of large segment critical bone defects

Abstract

The application belongs to the field of biomedical materials and bone tissue engineering technology, and discloses a preparation and application of a self-piezoelectric aluminum nitride film / cavity assembly structure for promoting repair of large segment critical bone defects. The film is based on the piezoelectric properties of AlN, and through optimization of the cavity structure, self-power generation capability under a physiological vibration environment is realized, and the surface current density of AlN is significantly improved. The film can continuously provide stable bioelectric signals without polarization treatment and external physical stimulation, thereby promoting adhesion, proliferation and differentiation of osteoblasts. In vivo experiments show that the film / cavity assembly structure can effectively repair rabbit femoral critical bone defects without a scaffold, and is superior to existing piezoelectric materials. The application breaks through the limitations of traditional piezoelectric bone repair materials which depend on external stimulation and scaffolds, and provides an innovative strategy with high clinical conversion potential for bone tissue repair.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of bone tissue regeneration, and particularly relates to preparation and application of a self-piezoelectric aluminum nitride film / cavity assembly structure for promoting repair of large critical bone defects. BACKGROUND

[0002] Repair of bone defects has always been a major challenge in orthopedic clinics, especially critical size bone defects. Epidemiological data shows that there are about several million cases of bone defects worldwide each year, of which more than 1.5 million new bone defect patients are in China each year, of which about 15% are critical size bone defects. Due to the lack of sufficient bone regeneration capacity, if such bone defects are not repaired in time, it may lead to bone nonunion, limb deformity or loss of function, and seriously affect the quality of life of patients. At present, autologous bone transplantation, allogeneic bone transplantation and artificial bone materials are mainly used for treatment in clinics. Autologous bone transplantation is considered as the "gold standard", but its bone supply is insufficient, the incidence of complications in the donor area is as high as 20%-30%, and the surgical trauma is large, which limits its wide application. Although allogeneic bone transplantation avoids bone trauma, it has problems of immune rejection and bone resorption, and the long-term integration rate is less than 70%. In recent years, artificial synthetic bone materials have made some progress, and have excellent biocompatibility and plasticity, but their bone induction capacity and long-term mechanical properties are limited, especially the success rate in the repair of weight-bearing bone defects is only 60%-70%. In addition, emerging technologies such as stem cell transplantation and growth factor delivery have performed well in experimental studies, but due to their high cost and technical complexity, clinical promotion still faces challenges. Therefore, the current bone defect repair methods still have problems of lack of donor resources, insufficient bone integration capacity and high treatment cost, and the development of new, efficient and translatable bone repair materials has become the key to solving the difficulties of bone defect treatment.

[0003] Piezoelectric materials are widely used in bone tissue engineering due to their ability to generate electrical signals under mechanical stimulation. Studies have shown that bioelectric signals play a crucial role in bone regeneration, and the physiological load of the skeleton generates local potential differences, which in turn regulate the biological behavior of osteoblasts. However, most piezoelectric materials currently have the following problems: (1) Traditional inorganic piezoelectric materials (such as barium titanate and lead zirconate titanate) have high piezoelectric constants, but their chemical stability and biocompatibility are poor, making them difficult to use in biomedical fields; (2) Organic piezoelectric materials (such as polyvinylidene fluoride, PVDF) have good flexibility and biocompatibility, but their piezoelectric performance is low, and they must rely on external polarization or mechanical stretching to continuously output electrical signals; (3) Most existing piezoelectric bone repair materials need to be combined with scaffolds, making the application process complex and affecting their clinical feasibility. Therefore, developing a piezoelectric material that does not require external polarization or mechanical stimulation and can output long-term stable bioelectric signals without a scaffold is of great significance for bone defect repair.

[0004] Third-generation semiconductor materials (such as AlN, SiC, GaN) have attracted attention in high-frequency electronics, photodetection, 5G communication, and micro-electro-mechanical systems (MEMS) due to their wide bandgap, high breakdown electric field, excellent thermal stability, and mechanical properties. Compared to traditional piezoelectric materials (such as PZT and BaTiO3), third-generation semiconductor materials have higher chemical stability, better mechanical matching, and biocompatibility, making them suitable for biomedical sensing and implantable neural regulation. In the field of bone tissue regeneration, third-generation semiconductor materials have the potential to overcome the limitations of traditional piezoelectric materials. First, third-generation semiconductor materials have higher chemical stability and biocompatibility, avoiding the potential toxicity of harmful elements such as lead, making them more suitable for long-term implantation. Second, compared to organic piezoelectric materials (such as PVDF), third-generation semiconductor materials have superior piezoelectric properties and do not require polarization treatment or continuous external mechanical stretching to maintain stable bioelectric signal output. In addition, most traditional piezoelectric materials need to be combined with scaffolds, leading to material degradation and insufficient mechanical matching, while third-generation semiconductor materials have high mechanical strength and excellent structural stability, making them suitable for scaffold-free applications, simplifying the bone repair process, and improving clinical feasibility.

[0005] Therefore, third-generation semiconductor materials provide a more stable, efficient, and convenient new strategy for bone defect repair, and have the potential to become the next generation of bioelectric stimulation bone repair materials. SUMMARY

[0006] The purpose of the present application is to provide a self-piezoelectric aluminum nitride film / cavity assembly structure for promoting the repair of large critical bone defects and its application.

[0007] This invention is achieved through the following technical solution:

[0008] A method for preparing a self-piezoelectric aluminum nitride thin film / cavity component structure that promotes the repair of large-segment critical bone defects includes the following steps:

[0009] S1. A shallow cavity structure of 3mm*10mm*2.5μm is formed on a silicon (Si) substrate by photolithography.

[0010] S2. Continue to use magnetron sputtering technology to deposit a 1.0 μm thick aluminum nitride (AlN) piezoelectric layer;

[0011] S3. A cavity structure is formed in the Si substrate using wet etching technology, combined with silicon substrate thinning process to enhance the piezoelectric properties of the film, and finally a self-piezoelectric AlN film is obtained.

[0012] S4. The prepared film is attached to the surface of the titanium alloy cavity component using PDMS. After the PDMS solidifies, a self-piezoelectric AlN film / cavity component structure is formed.

[0013] Furthermore, the etching described in step S1 is wet etching, and the mask material used for etching is SiO2.

[0014] Furthermore, the parameters for magnetron sputtering described in step S2 are as follows:

[0015] Target material: Aluminum (99.9999%);

[0016] Substrate: Si(111);

[0017] Splashing time: 710s;

[0018] Deposition rate: 76 nm / min;

[0019] Nitrogen flow rate: 50 sccm;

[0020] AC power: 7kW;

[0021] DC voltage: 15V;

[0022] Sputtering pressure: 0.2 Pa.

[0023] Furthermore, the wet etching process described in step S3 uses a 10% hydrofluoric acid solution, is performed at room temperature, and takes 40 minutes.

[0024] Furthermore, the dimensions of the self-piezoelectric AlN film described in step S3 are 5mm*10mm*0.1mm.

[0025] Application of a self-piezoelectric aluminum nitride thin film / cavity component structure in the fabrication of implants for treating large-segment critical bone defects.

[0026] The present invention has the following advantages over the prior art:

[0027] 1. The core innovation of the self-piezoelectric AlN thin film / cavity component structure of the present invention lies in the cavity structure design of the self-piezoelectric AlN thin film. By precisely controlling the cavity size, the current density on the AlN surface is significantly improved, thereby enhancing the piezoelectric performance and enabling it to autonomously output a stable electrical signal in a physiological environment.

[0028] 2. Based on the piezoelectric properties of AlN, the thin film of this invention achieves self-generating power under physiological vibration conditions through optimized cavity structure, significantly improving the surface current density of AlN. The thin film of this invention can continuously provide stable bioelectric signals without polarization treatment or external physical stimulation, thereby promoting osteoblast adhesion, proliferation, and differentiation. In vivo experiments show that this thin film / cavity component structure can effectively repair critical bone defects in the rabbit femur without a scaffold, achieving significant bone regeneration within 4 weeks, which is superior to existing piezoelectric materials. This invention overcomes the limitations of traditional piezoelectric bone repair materials that rely on external stimulation and scaffolds, providing an innovative strategy with high clinical translational potential for bone tissue repair. Attached Figure Description

[0029] Figure 1 This is a photograph of an AlN thin film.

[0030] Figure 2 This is a scanning electron microscope (SEM) image of a cross-section of an AlN thin film.

[0031] Figure 3 The graph shows the electrical properties of the AlN thin film.

[0032] Figure 4 The cell proliferation results of r-BMSCs cells after culturing on AlN film surface for 24 h, 48 h and 72 h;

[0033] Figure 5 The effect of AlN film on promoting osteogenic proliferation and differentiation of BMSCs;

[0034] Figure 6 To enhance bone regeneration under critical bone defects using AlN thin film / cavity component structures;

[0035] Figure 7 This is a schematic diagram of the AlN thin film structure;

[0036] Figure 8 This is a schematic diagram of the AIN thin-film / cavity assembly structure;

[0037] Figure 9A schematic diagram of a seven-hole bone plate without an AIN film.

[0038] Figure 10 A schematic diagram of a seven-hole bone plate loaded with an AIN film;

[0039] Figure 11 A schematic diagram of an eight-hole bone plate without an AIN film.

[0040] Figure 12 A schematic diagram of an eight-hole bone plate loaded with an AIN film;

[0041] In the figure: 1. AIN film; 2. Cavity in AIN film; 3. Bolt of cavity assembly; 4. Bone plate; 5. Hole in bone plate; 6. Nut of cavity assembly; 7. Groove of cavity assembly; 8. Cavity in cavity assembly; 9. Groove of bone plate. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention.

[0043] Unless otherwise specified, all experimental materials and equipment used in the following embodiments were commercially available; wherein: the experimental cells included:

[0044] rBMSCs cells: purchased from Cyagen (Guangzhou) Biotechnology Co., Ltd.

[0045] Example 1

[0046] Preparation and characterization of AlN thin films

[0047] S1. A shallow cavity structure with a depth of approximately 2.5 μm is formed on a silicon (Si) substrate by photolithography.

[0048] S2. Continue to use magnetron sputtering technology to deposit a 1.0 μm thick AlN piezoelectric layer;

[0049] S3. A cavity structure is formed within the Si substrate using wet etching technology, combined with a silicon substrate thinning process to enhance the piezoelectric properties of the thin film, ultimately yielding a self-piezoelectric AlN thin film (size: 5mm*10mm*0.1mm); Figure 1 As shown, the physical image of the AlN thin film demonstrates its structural integrity and fine processing technology.

[0050] To characterize the microstructure and structural properties of the prepared films, the self-piezoelectric AlN films prepared in this embodiment were analyzed using scanning electron microscopy (SEM). Figure 2The cross-section shows the AlN thin film structure, indicating that the multilayer structure of the film is complete and well-bonded.

[0051] To verify the electrical properties of the AlN thin film, the film was fixed on a Ti6Al4V bone plate, and its electrical properties were tested by simulating physiological movement frequencies using a vibration platform. Figure 3 The results showed that, compared to the group without a film, the piezoelectric properties of the AlN film with cavities and the introduction of cavities into the cavity assembly improved by an order of magnitude. This indicates that the introduction of the cavity structure effectively optimized the electrical response of the film, providing a stable bioelectric signal for bone tissue repair.

[0052] Example 2

[0053] Fabrication of AIN thin film / cavity component structure and its bonding to bone plate

[0054] S1. The prepared AlN thin film 1 is attached to the surface of the titanium alloy cavity component using PDMS. After the PDMS solidifies, a self-piezoelectric AlN thin film / cavity component structure is formed.

[0055] S2, such as Figures 9 to 12 As shown, the AIN film / cavity assembly structure is fixed on the bone plate 4 by embedding the AIN film / cavity assembly structure into the bone plate groove 9 and connecting the nut 6 of the cavity assembly through the bone plate hole 5 with the bolt 3 of the cavity assembly.

[0056] like Figure 8 As shown, the self-piezoelectric AlN thin film / cavity assembly structure of the present invention consists of an AlN thin film 1, a cavity 2 in the AlN thin film, and a cavity 8 in the cavity assembly, wherein the AlN thin film 1 is attached to the groove 7 of the cavity assembly by PDMS.

[0057] Example 3

[0058] In vitro cell compatibility verification of AlN thin film and titanium alloy cavity assembly

[0059] To verify the biocompatibility of the prepared self-piezoelectric AlN films, four groups were established: a cavity-free component group, a cavity-free component + vibration group, a film + cavity-free component + vibration group, and a film / cavity component composite + vibration group. Films and cavity component sheets (with the same surface morphology as the film but without internal cavities and Mo electrodes, thus unable to generate current) were attached to the bottom of 12-well cell culture plates using polydimethylsiloxane (PDMS). r-BMSCs were seeded on the film surface and cultured to assess their biocompatibility. CCK-8 and live / dead staining were used to evaluate the biocompatibility. Figure 4The proliferation of r-BMSCs was detected after 24h, 48h, and 72h of culture. The results showed that the cell proliferation capacity of the film group was not significantly different from that of the control group, indicating that the AlN film and the cavity component had no obvious cytotoxicity.

[0060] Example 4

[0061] AlN film can promote osteoblast proliferation and differentiation in in vitro experiments.

[0062] The following groups were set up: cavity-free component group, cavity-free component + vibration group, membrane + cavity-free component + vibration group, and membrane / cavity component complex + vibration group. The membrane and cavity component were attached to the bottom of a 6-well cell culture plate using PDMS, and BMSCs were seeded into the wells. When the cell aggregation degree reached 70-80%, osteogenic induction medium was added for culture. Vibration intervention (0.5N, 1Hz, 10 minutes / day) was added to each well. Alkaline phosphatase staining was performed after 7 days, and Alizarin Red staining was performed after 21 days to evaluate the effect of promoting osteoblast proliferation and differentiation in vitro.

[0063] Test results as follows Figure 5 As shown in the figure, the vibrating AIN film can significantly promote the expression of alkaline phosphatase and calcium deposition in osteoblasts.

[0064] The following groups were set up: cavity-free component group, cavity-free component + vibration group, membrane + cavity-free component + vibration group, and membrane / cavity component complex + vibration group. The membrane and cavity component were attached to the bottom of a 6-well cell culture plate using PDMS, and BMSCs were seeded into the wells. When the cell aggregation degree reached 70-80%, osteogenic induction medium was added for culture. Vibration intervention (0.5N, 1Hz, 10 minutes / day) was added to each well. After 7 days, RNA was extracted, and the expression of BMP-2, Runx2, and Col-1a genes was detected.

[0065] Test results as follows Figure 5 As shown in the figure, the vibrating self-piezoelectric film can significantly promote the expression of osteogenic-related genes.

[0066] Example 5

[0067] Functions of AlN film / cavity component structure in promoting regeneration of large bone defects in vivo

[0068] We constructed a critical bone defect model of the femoral shaft in New Zealand rabbits by setting up three groups: a cavity-free component group, a membrane + cavity-free component group, and a membrane / cavity component composite group. We used AlN membrane / cavity component structures to internally fix the femoral shaft bone defect. After 4 weeks of treatment, we harvested tissue and observed the imaging results.

[0069] Animal experiment results such as Figure 6 As shown, the defect site in the cavityless component group showed almost no new bone ingrowth. The membrane + cavityless component group showed partial bone ingrowth, while the membrane / cavity component composite group showed extensive bone ingrowth and complete healing.

[0070] In summary, the self-piezoelectric AlN thin film / cavity component composite prepared by this invention can significantly promote osteogenic formation in vitro and be used in vivo for the repair of critical bone defects, thereby treating large-segment critical bone defects.

[0071] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a self-piezoelectric aluminum nitride thin film / cavity assembly structure for promoting repair of large segmental critical bone defects, characterized in that, The method comprises the following steps: S1, etching a 3 mm*10 mm*2.5 μm shallow cavity structure on a silicon substrate by using a photolithography process; S2, continuing to use a magnetron sputtering technology to deposit a 1.0 μm thick aluminum nitride piezoelectric layer; S3, using a wet etching technology to form a cavity structure in the Si substrate, and combining a silicon substrate thinning process to enhance the piezoelectric performance of the thin film, and finally obtaining a self-piezoelectric AlN thin film; S4, attaching the prepared thin film to the surface of a titanium alloy cavity assembly by using PDMS, and forming a self-piezoelectric AlN thin film / cavity assembly structure after the PDMS solidifies.

2. The method for preparing a self-piezoelectric aluminum nitride thin film / cavity component structure for promoting the repair of large-segment critical bone defects according to claim 1, characterized in that, The etching in step S1 is wet etching, and the mask material used for etching is SiO2.

3. The method for preparing a self-piezoelectric aluminum nitride thin film / cavity component structure for promoting the repair of large-segment critical bone defects according to claim 1, characterized in that, The parameters during the magnetron sputtering in step S2 are as follows: Target material: aluminum, purity 99.9999%; Substrate: Si, silicon wafer with (111) crystal orientation; Sputtering time: 710 s; Deposition rate: 76 nm / min; Nitrogen flow rate: 50 sccm; AC power: 7 kW; DC voltage: 15 V; Sputtering pressure: 0.2 Pa.

4. The method for preparing a self-piezoelectric aluminum nitride thin film / cavity component structure for promoting the repair of large-segment critical bone defects according to claim 1, characterized in that, The wet etching in step S3 uses an etching solution of 10% hydrofluoric acid solution, etching at room temperature, and the etching time is 40 min.

5. The method for preparing a self-piezoelectric aluminum nitride thin film / cavity component structure for promoting the repair of large-segment critical bone defects according to claim 1, characterized in that, The size of the self-piezoelectric AlN thin film in step S3 is 5 mm*10 mm*0.1 mm.

6. A self-piezoelectric aluminum nitride thin film / cavity assembly structure prepared by the method of any one of claims 1-5.

7. Use of the self-piezoelectric aluminum nitride thin film / cavity assembly structure of claim 6 in preparing an implant for treating large critical bone defects.

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