Medical titanium alloy surface modification coating for bone implantation

Abstract

The invention discloses a medical titanium alloy surface modified coating for bone implantation, which is prepared by the following steps: step (1) plasma-assisted nitriding pretreatment: placing a titanium alloy matrix in a vacuum chamber, introducing high-purity nitrogen, hydrogen and argon mixed gas, maintaining the air pressure at 0.15-2.0 Pa, applying-50 to-400 V pulsed bias to the matrix, performing plasma nitriding for 45-90 minutes at the temperature of 450-600 DEG C, and performing plasma nitriding treatment to obtain a titanium alloy surface modified coating; forming a gradient nitriding layer; according to the medical titanium alloy surface modification coating for bone implantation provided by the invention, nitriding reinforcement of a matrix, micro-arc oxidation construction of micropores and anodic oxidation growth of a nano structure are combined, so that the problems that a coating in a single technology is weak in binding force and the nano structure is easy to fall off are solved.

Description

Technical Field

[0001] This invention relates to the field of metal composite coating technology, and more specifically to a modified coating for the surface of a titanium alloy used in bone implants. Background Technology

[0002] Medical implants such as total hip arthroplasty, dental implants, and coronary artery stents are widely used in clinical practice, but they still face the risk of implant failure. Foreign body reactions caused by implant wear debris and corrosion products, as well as bacterial infections, are the main factors leading to implant failure. Depositing coatings on the implant surface is an effective strategy to enhance implant performance and improve its durability. To date, surface coating modification of implants is a research hotspot in the field of biomedical materials. TiN coatings possess good biocompatibility, high wear resistance, and corrosion resistance, making TiN coating deposition on the surface of metallic implants an effective strategy to address their performance shortcomings.

[0003] In recent years, the industry has partially addressed the above issues through the following technological optimizations. However, despite these improvements, the existing technologies still have the following shortcomings: For example, patent CN202410435186 uses only nitrided TiN.

[0004] For example, in patent CN202411783876, micro-arc / anodic oxidation is performed in steps but without matrix reinforcement.

[0005] The existing technology still has shortcomings and needs to be improved and strengthened. Therefore, it is urgent to design a surface modification coating for medical titanium alloys used in bone implants to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a modified coating for the surface of a medical titanium alloy for bone implants, in order to overcome the above-mentioned shortcomings of the prior art.

[0007] In order to achieve the above object, the present invention provides the following technical solutions: A surface-modified coating for medical titanium alloy used in bone implants, comprising the following steps: Step (1) Plasma-assisted nitriding pretreatment: The titanium alloy substrate is placed in a vacuum chamber and a mixture of high-purity nitrogen, hydrogen and argon is introduced. The gas pressure is maintained at 0.15~2.0 Pa. A pulse bias voltage of -50~-400 V is applied to the substrate, and the temperature is 450~600℃. Plasma nitriding is performed for 45~90 minutes to form a gradient nitriding layer. Step (2) Micro-arc oxidation treatment: Using an aqueous solution containing 0.01~0.1 mol / L sodium β-glycerophosphate and 0.1~1 mol / L calcium acetate as the electrolyte, the treatment is carried out for 1~10 minutes under the conditions of current density 0.1~3 A / cm², frequency 500~1000 Hz and duty cycle 10~50% to generate a micron-sized porous oxide layer; Step (3) Anodizing nanostructuring: Using a mixed electrolyte of ethylene glycol and water, add 0.05~0.5mol / L ammonium fluoride, and treat for 10 seconds to 180 minutes at a voltage of 5~150 V and a temperature of 25~60℃ to form a composite coating of nanotubes or cauliflower-shaped nanoparticles.

[0008] Preferably, in the plasma nitriding step, the mixed gas ratio is N2:H2:Ar=1:1:(3~5), the pulse frequency is 15~25 kHz, and the duty cycle is 65~95%. The nitrided layer depth is 10~50 μm, the surface hardness is ≥800 HV, and the elastic modulus is ≤55GPa.

[0009] Preferably, the micro-arc oxidation electrolyte contains 0.05~0.2 mol / L ammonium fluoride and is doped with at least one of strontium ions (Sr²⁺) or zinc ions (Zn²⁺) at a concentration of 0.01~0.1 mol / L.

[0010] Preferably, the anodizing step employs a gradient voltage method: initially maintaining 5 V for 10 minutes, then increasing to 20 V and maintaining for 30 minutes, and finally increasing to 50~100 V for 60 minutes.

[0011] Preferably, the nanostructure surface is loaded with bone morphogenetic protein-2 (BMP-2) and mesoporous silica nanoparticles loaded with vancomycin, which are adsorbed into the inside of the nanotube by an impregnation method.

[0012] Preferably, the bonding strength of the composite coating is ≥50 N.

[0013] Preferably, the titanium alloy is Ti-24Nb-4Zr-7.9Sn or Ti-6Al-4V ELI.

[0014] Preferably, a hydrothermal crosslinking step is added between the micro-arc oxidation layer and the nanostructure layer: treatment in an alkaline solution at 180~200℃ and pH=9.5 for 6 hours to generate hydroxyapatite / titanium oxide nanorod heterojunctions, accelerating in vitro mineralization.

[0015] Preferably, the wetting angle of the coating surface is 10~30°, and the surface energy is ≥70 mJ / m².

[0016] Preferably, it is suitable for artificial joints, interbody fusion devices or bone screws, with a bone integration strength ≥25 MPa 12 weeks after implantation.

[0017] In the above technical solution, the present invention provides a surface modification coating for medical titanium alloy for bone implantation. The present invention combines nitriding to strengthen the matrix, micro-arc oxidation to construct micropores, and anodic oxidation to grow nanostructures, thereby solving the problems of weak adhesion of coatings using single technologies and easy detachment of nanostructures. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0019] Figure 1 This is a schematic diagram illustrating the steps of an embodiment of a modified titanium alloy surface coating for bone implantation according to the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0021] like Figure 1 As shown in the figure, an embodiment of the present invention provides a surface modification coating for medical titanium alloy used in bone implants, comprising the following steps: Step (1) Plasma-assisted nitriding pretreatment: The titanium alloy substrate is placed in a vacuum chamber and a mixture of high-purity nitrogen, hydrogen and argon is introduced. The gas pressure is maintained at 0.15~2.0 Pa. A pulse bias voltage of -50~-400 V is applied to the substrate, and the temperature is 450~600℃. Plasma nitriding is performed for 45~90 minutes to form a gradient nitriding layer. Step (2) Micro-arc oxidation treatment: Using an aqueous solution containing 0.01~0.1 mol / L sodium β-glycerophosphate and 0.1~1 mol / L calcium acetate as the electrolyte, the treatment is carried out for 1~10 minutes under the conditions of current density 0.1~3 A / cm², frequency 500~1000 Hz and duty cycle 10~50% to generate a micron-sized porous oxide layer; Step (3) Anodizing nanostructuring: Using a mixed electrolyte of ethylene glycol and water (ethylene glycol volume ratio 90~98%), add 0.05~0.5 mol / L ammonium fluoride, and treat at a voltage of 5~150 V and a temperature of 25~60℃ for 10 seconds~180 minutes to form a composite coating of nanotubes or cauliflower-shaped nanoparticles.

[0022] This invention combines nitriding to strengthen the matrix, micro-arc oxidation to construct micropores, and anodic oxidation to grow nanostructures, solving the problems of weak coating adhesion (such as patent CN202410435186 which only uses nitriding-TiN) and easy detachment of nanostructures (such as patent CN202411783876 where micro-arc / anodic oxidation are performed in steps but without matrix strengthening). The nitriding layer reduces the elastic modulus (close to 45 GPa in human bone), the micro-arc oxidation layer loads Ca / P elements to promote osteointegration, and the nanolayer increases the specific surface area to enhance cell adhesion. The overall performance is superior to existing technologies.

[0023] Preferably, in the plasma nitriding step, the mixed gas ratio is: The pulse frequency is 15~25kHz, and the duty cycle is 65~95%. The nitrided layer depth is 10~50 μm, the surface hardness is ≥800 HV, and the elastic modulus is ≤55 GPa. These parameters ensure that the nitrided layer forms a metallurgical bond with the titanium matrix, avoiding local overheating and stress concentration caused by traditional glow discharge (such as patent CN202410435186), while reducing the elastic modulus to match bone tissue and reduce stress shielding effect.

[0024] Preferably, the micro-arc oxidation electrolyte contains 0.05~0.2 mol / L ammonium fluoride and is doped with strontium ions. or zinc ions At least one of the following, at a concentration of 0.01~0.1 mol / L. Doping Upregulating osteoblast BMP-2 gene expression and incorporating Zn²⁺ inhibits Staphylococcus aureus proliferation (inhibition rate ≥90%), synergistically enhancing the coating's bioactivity and antibacterial properties.

[0025] Preferably, the anodizing step employs a gradient voltage method: initially maintaining 5 V for 10 minutes, then increasing to 20 V and maintaining for 30 minutes, and finally increasing to 50-100 V for 60 minutes. The gradient voltage forms a tapered nanotube array with a bottom diameter of 80-100 nm and a top diameter of 30-50 nm, increasing the specific surface area by 40% compared to nanotubes produced by a single voltage, thus promoting the spread and differentiation of bone marrow mesenchymal stem cells.

[0026] Preferably, bone morphogenetic protein-2 (BMP-2) and vancomycin-loaded mesoporous silica nanoparticles are loaded onto the surface of the nanostructure and adsorbed into the interior of the nanotubes via an impregnation method. The BMP-2 loading is ≥5 μg / cm², and the vancomycin sustained-release time is ≥28 days, achieving the dual functions of early antibacterial (reducing bacterial adhesion by 85%) and late osteogenic (increasing ALP activity by 50%).

[0027] Preferably, the bonding strength of the composite coating is ≥50 N (ASTM F1044 standard), which is much higher than that of a single TiN coating (10~20 N, patent CN202410435186); the wear resistance is improved by 5 times compared with untreated titanium alloy (friction coefficient ≤0.2), and the corrosion resistance is improved by 1 time (corrosion current density). Soak in physiological saline for 30 days.

[0028] Preferably, the titanium alloy is Ti-24Nb-4Zr-7.9Sn or Ti-6Al-4V ELI. The former has an elastic modulus of 45 GPa, matching human bone; the latter, after nitriding, reduces V ion release to 0.01 ppm (ICP-MS test), eliminating toxicity risks.

[0029] Preferably, a hydrothermal crosslinking step is added between the micro-arc oxidation layer and the nanostructure layer: treatment in an alkaline solution at 180~200℃ and pH=9.5 for 6 hours generates hydroxyapatite / titanium oxide nanorod heterojunctions, which accelerates in vitro mineralization (calcium and phosphorus deposition reaches 15 mg / cm² after SBF immersion for 7 days).

[0030] Preferably, the coating surface has a wetting angle of 10~30° and a surface energy of ≥70 mJ / m², which promotes osteoblast pseudopodia extension and increases cell adhesion density by 3 times.

[0031] Preferably, it is suitable for artificial joints, interbody fusion devices or bone screws, with a bone integration strength ≥25 MPa 12 weeks after implantation (rabbit femoral implantation model). Example 1

[0032] A surface-modified coating for medical titanium alloy used in bone implants, comprising the following steps: Step (1) Plasma-assisted nitriding pretreatment: The titanium alloy substrate is placed in a vacuum chamber and a mixture of high-purity nitrogen, hydrogen and argon is introduced. The gas pressure is maintained at 0.15~2.0 Pa. A pulse bias voltage of -50~-400 V is applied to the substrate, and the temperature is 450~600℃. Plasma nitriding is performed for 45~90 minutes to form a gradient nitriding layer. Step (2) Micro-arc oxidation treatment: Using an aqueous solution containing 0.01~0.1 mol / L sodium β-glycerophosphate and 0.1~1 mol / L calcium acetate as the electrolyte, the treatment is carried out for 1~10 minutes under the conditions of current density 0.1~3 A / cm², frequency 500~1000 Hz and duty cycle 10~50% to generate a micron-sized porous oxide layer; Step (3) Anodizing nanostructuring: Using a mixed electrolyte of ethylene glycol and water (ethylene glycol volume ratio 90~98%), add 0.05~0.5 mol / L ammonium fluoride, and treat at a voltage of 5~150 V and a temperature of 25~60℃ for 10 seconds~180 minutes to form a composite coating of nanotubes or cauliflower-shaped nanoparticles. Example 2

[0033] This embodiment further specifies the requirements based on Embodiment 1. In the plasma nitriding step, the mixed gas ratio is: The pulse frequency is 15-25 kHz, and the duty cycle is 65-95%. The nitriding layer depth is 10-50 μm, the surface hardness is ≥800 HV, and the elastic modulus is ≤55 GPa. These parameters ensure that the nitriding layer forms a metallurgical bond with the titanium substrate, avoiding local overheating and stress concentration caused by traditional glow discharge (such as patent CN202410435186). At the same time, the elastic modulus is reduced to match bone tissue and reduce stress shielding effect. 0.05-0.2 mol / L ammonium fluoride and strontium ions are added to the micro-arc oxidation electrolyte. or zinc ions At least one of the following, at a concentration of 0.01~0.1 mol / L. Doping Upregulate osteoblast BMP-2 gene expression, incorporating It inhibits the proliferation of Staphylococcus aureus (antibacterial inhibition rate ≥90%) and synergistically enhances the bioactivity and antibacterial properties of the coating. The anodizing step adopts a gradient voltage method: initially 5 V for 10 minutes, then increased to 20 V for 30 minutes, and finally increased to 50~100 V for 60 minutes. The gradient voltage forms a cone-shaped nanotube array with a bottom diameter of 80~100 nm and a top diameter of 30~50 nm, which increases the specific surface area by 40% compared with single-voltage nanotubes, promoting the spread and differentiation of bone marrow mesenchymal stem cells. The surface of the nanostructure is loaded with bone morphogenetic protein-2 (BMP-2) and vancomycin-loaded mesoporous silica nanoparticles, which are adsorbed into the interior of the nanotubes by impregnation. With a BMP-2 loading capacity ≥5 μg / cm² and a vancomycin sustained-release time ≥28 days, it achieves dual functions of early antibacterial (85% reduction in bacterial adhesion) and late-stage osteogenic (50% increase in ALP activity). The composite coating has a bonding strength ≥50 N (ASTM F1044 standard), far exceeding that of a single TiN coating (10~20 N, patent CN202410435186). Its wear resistance is 5 times higher than untreated titanium alloys (friction coefficient ≤0.2), and its corrosion resistance is 1 time higher (corrosion current density). The titanium alloy is either Ti-24Nb-4Zr-7.9Sn or Ti-6Al-4V ELI, which is soaked in physiological saline for 30 days. The former has an elastic modulus of 45 GPa, matching human bone; the latter, after nitriding, reduces V ion release to 0.01 ppm (ICP-MS test), eliminating toxicity risks. A hydrothermal cross-linking step is added between the micro-arc oxidation layer and the nanostructure layer: treatment in an alkaline solution at 180~200℃ and pH=9.5 for 6 hours generates hydroxyapatite / titanium oxide nanorod heterostructures, accelerating in vitro mineralization (calcium and phosphorus deposition reaches 15 mg / cm² after SBF soaking for 7 days). The surface wetting angle of the coating is 10~30°, and the surface energy is ≥70 mJ / m², promoting osteoblast pseudopodia extension and increasing cell adhesion density by 3 times. It is suitable for artificial joints, intervertebral fusion devices, or bone nails. The bone integration strength is ≥25 MPa 12 weeks after implantation (rabbit femoral implantation model).

[0034] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A surface-modified coating for medical titanium alloy used in bone implants, characterized in that, Includes the following steps: Step (1) Plasma-assisted nitriding pretreatment: The titanium alloy substrate is placed in a vacuum chamber and a mixture of high-purity nitrogen, hydrogen and argon is introduced. The gas pressure is maintained at 0.15~2.0 Pa. A pulse bias voltage of -50~-400 V is applied to the substrate, and the temperature is 450~600℃. Plasma nitriding is performed for 45~90 minutes to form a gradient nitriding layer. Step (2) Micro-arc oxidation treatment: Using an aqueous solution containing 0.01~0.1 mol / L sodium β-glycerophosphate and 0.1~1 mol / L calcium acetate as the electrolyte, the treatment is carried out for 1~10 minutes under the conditions of current density 0.1~3 A / cm², frequency 500~1000 Hz and duty cycle 10~50% to generate a micron-sized porous oxide layer; Step (3) Anodizing nanostructuring: Using a mixed electrolyte of ethylene glycol and water, add 0.05~0.5 mol / L ammonium fluoride, and treat for 10 seconds to 180 minutes at a voltage of 5~150 V and a temperature of 25~60℃ to form a composite coating of nanotubes or cauliflower-shaped nanoparticles.

2. The surface modification coating for medical titanium alloy used in bone implants according to claim 1, characterized in that, In the plasma nitriding step, the mixed gas ratio is N2:H2:Ar=1:1:(3~5), the pulse frequency is 15~25 kHz, and the duty cycle is 65~95%. The nitrided layer depth is 10~50 μm, the surface hardness is ≥800 HV, and the elastic modulus is ≤55 GPa.

3. The surface modification coating for medical titanium alloy used in bone implants according to claim 1, characterized in that, The micro-arc oxidation electrolyte contains 0.05~0.2 mol / L ammonium fluoride and is doped with at least one of strontium ions (Sr²⁺) or zinc ions (Zn²⁺) at a concentration of 0.01~0.1 mol / L.

4. The surface modification coating for medical titanium alloy used in bone implants according to claim 1, characterized in that, The anodizing step employs a gradient voltage method: initially 5 V for 10 minutes, then increased to 20 V for 30 minutes, and finally increased to 50~100 V for 60 minutes.

5. The surface modification coating for medical titanium alloy used in bone implants according to claim 1, characterized in that, The nanostructure is loaded with bone morphogenetic protein-2 (BMP-2) and mesoporous silica nanoparticles loaded with vancomycin, which are adsorbed into the inside of the nanotube by impregnation.

6. The surface modification coating for medical titanium alloy used in bone implants according to claim 1, characterized in that, The bonding strength of the composite coating is ≥50 N.

7. The surface modification coating for medical titanium alloy used in bone implants according to claim 1, characterized in that, The titanium alloy is either Ti-24Nb-4Zr-7.9Sn or Ti-6Al-4V ELI.

8. The surface-modified coating for medical titanium alloy used in bone implants according to claim 1, characterized in that, A hydrothermal crosslinking step is added between the micro-arc oxidation layer and the nanostructure layer: treatment in an alkaline solution at 180~200℃ and pH=9.5 for 6 hours generates hydroxyapatite / titanium oxide nanorod heterojunctions, accelerating in vitro mineralization.

9. The surface-modified coating for medical titanium alloy used in bone implants according to claim 1, characterized in that, The coating surface has a wetting angle of 10~30° and a surface energy of ≥70 mJ / m².

10. The surface-modified coating for medical titanium alloy used in bone implants according to claim 1, characterized in that, Suitable for artificial joints, interbody fusion devices or bone screws, with a bone integration strength ≥25 MPa 12 weeks after implantation.

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