Preparation method of medical high-strength and high-antibacterial bearing bone implant

Abstract

The invention relates to the technical field of biomedical materials, in particular to a preparation method of a medical high-strength and high-antibacterial bearing bone implant, which comprises the following steps: mixing 1-5wt% of silver powder and 95-99wt% of nickel-titanium alloy powder through a laser powder bed fusion technology, and carrying out 3D printing forming in a low-oxygen environment. And by optimizing key process parameters such as laser power and scanning speed, uniform distribution of the silver element and dispersion strengthening of the second phase are achieved, and the comprehensive performance of the material is remarkably improved. The obtained implant has high density, high strength and high antibacterial property, the compressive strength of the implant can reach 3400-3800 MPa, the elastic modulus of the implant is close to that of a human bone, the antibacterial rate of the implant to staphylococcus aureus and escherichia coli exceeds 95%, meanwhile, the inherent superelasticity and shape memory effect of nickel-titanium alloy are kept, and the implant can be applied to the field of medical treatment. The device is particularly suitable for orthopedic implantation of high-load parts such as interbody fusion cages and artificial joints.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biomedical materials, in particular to a preparation method of a medical high-strength high-antibacterial load-bearing bone implant. BACKGROUND

[0002] NiTi alloy has good shape memory effect, the maximum recoverable strain reaches 9% to 10%, the unique super-elasticity makes the medical devices such as NiTi wire made of NiTi alloy have good flexibility; the lower elastic modulus makes up for the shortcomings that the traditional medical metal materials are prone to stress shielding when used as bone implants, thereby causing osteoporosis; in addition, the NiTi alloy also has good fatigue resistance, wear resistance and corrosion resistance. The shape memory alloy used in clinical practice is mainly a nickel-titanium shape memory alloy. The medical nickel-titanium shape memory alloy has shape memory characteristics and super-elasticity in the phase transition region, is relatively soft at low temperature, can be deformed, and immediately restores to the original shape when heated to body temperature, producing a continuous and gentle restoring force. At this time, the material is relatively hard and elastic, and can play a role in orthopedics or support. Its excellent biocompatibility, corrosion resistance, wear resistance, non-toxicity and other characteristics are called new functional materials in the 21st century. Because of its excellent mechanical properties, it is the first choice for use as a load-bearing implant material in clinical practice, which can improve the quality of life of patients with injuries and diseases. However, many metal implants can activate the local host immune system and cause persistent inflammatory reactions. Therefore, designing a medical nickel-titanium silver alloy with good mechanical properties and antibacterial properties is the key to solving the application of nickel-titanium silver alloy in large bone implants.

[0003] Chinese patent document CN101914757A discloses a NiTi shape memory alloy with surface injection of metal elements, a layer of nanocomposite oxide film is formed on the surface of the NiTi shape memory alloy by injecting metal elements, and the nanocomposite oxide film is composed of titanium dioxide and oxides formed by the injected metal elements. The nanocomposite oxide film improves the corrosion resistance, wear resistance and biocompatibility of the NiTi shape memory alloy. However, the prior art still cannot meet the actual application requirements, the alloy does not have antibacterial ability and its mechanics still cannot meet the requirements of some high-mechanical-property implants, and it is still necessary to optimize the alloy grain refinement, mechanical property enhancement and antibacterial property enhancement. SUMMARY

[0004] The purpose of the present application is to provide a preparation method of a medical high-strength high-antibacterial load-bearing bone implant, which introduces the antibacterial property of the alloy by adding a small amount of silver element, and uses a laser powder bed fusion method to promote the uniform and fine dispersion of the second phase in nickel-titanium, thereby further improving the mechanical properties of the nickel-titanium silver alloy. The problem of implant failure caused by insufficient strength and lack of antibacterial property of the implant is solved.

[0005] To achieve the above technical purposes and effects, the present application is implemented by the following technical solutions: A preparation method of a medical high-strength and high-antibacterial load-bearing bone implant, comprising the following steps: Providing a NiTi alloy powder and an Ag powder, mixing the two to form a mixed powder with a mass percentage of Ag element of 1-5%; Using a laser powder bed melting technology to layer-by-layer melt and solidify the mixed powder to form a shape under a protective atmosphere, wherein the laser power is controlled to be 120-160 W, and the scanning speed is 600-1000 mm / s; Post-processing the formed component to obtain the load-bearing bone implant; The load-bearing bone implant has a yield strength of not less than 500 MPa, a compressive strength of not less than 3400 MPa, an elastic modulus of not higher than 30 GPa, and an antibacterial rate of not less than 95%.

[0006] Further, before the laser powder bed melting forming, a structure model of the load-bearing bone implant is designed by a three-dimensional modeling software, and the model is imported into a printing device.

[0007] Further, the mass percentage of Ni in the NiTi alloy powder is 55.47 wt.%, and the mass percentage of Ti is 44.53 wt.%; the particle size of the NiTi alloy powder and the Ag powder is 15-53 μm.

[0008] Further, the protective atmosphere is an atmosphere with an oxygen content of less than 0.1% obtained by first vacuuming to an oxygen content of less than 100 ppm and then filling in inert gas; wherein the inert gas is argon with a purity of greater than or equal to 99.9%.

[0009] Further, in the laser powder bed melting forming process, the process parameters also include a scanning interval of 0.06-0.07 mm and a powder laying thickness of 0.03 mm.

[0010] Further, in the laser powder bed melting forming process, the printing substrate is preheated to 40-80°C.

[0011] Further, the post-processing includes separating the formed component from the substrate by wire cutting, and Cleaning step: placing the implant in a 95% anhydrous ethanol solution and ultrasonic cleaning for 5-10 minutes, replacing the ethanol and repeating 3-4 times.

[0012] Further, the post-treatment after the cleaning step further comprises an acid pickling step: pickling the implant with an acid pickling solution prepared from concentrated HF, concentrated HNO3 and H2O in a volume ratio of 1: (2-4): (5-8).

[0013] A medical high-strength and high-antibacterial load-bearing bone implant prepared by the above preparation method, the load-bearing bone implant has a yield strength of not less than 500 MPa, a compressive strength of not less than 3400 MPa, an elastic modulus of not higher than 30 GPa, and an antibacterial rate of not less than 95%.

[0014] The beneficial effects of the present application are: The present application adopts laser powder bed fusion technology (L-PBF) to melt NiTi-Ag mixed powder layer by layer by high-energy laser beam, and realizes precise forming of the implant under a protective atmosphere. By using its fine laser spot and accurate digital control system, a load-bearing bone implant with complex three-dimensional structure can be prepared. During the forming process, the molten pool formed by the interaction of laser and powder undergoes a rapid melting process, resulting in a very high cooling rate, and the non-equilibrium solidification conditions significantly refine the grain size of the material and promote the formation of sub-micron structure. At the same time, rapid solidification effectively inhibits element segregation, so that the Ag element can be uniformly distributed in the NiTi matrix in the form of supersaturated solid solution and nano-scale precipitated phase, which not only eliminates the macro-segregation defects in traditional casting methods such as SPS sintering and vacuum non-consumable arc melting technology, but also significantly improves the mechanical properties of the material through fine-grain strengthening and second-phase strengthening mechanisms.

[0015] In the laser powder bed fusion forming process, the present application adopts the parameter combination of 120-160W laser power and 600-1000mm / s scanning speed, which not only ensures the complete melting and densification of the powder, but also effectively controls the volatilization loss of Ag element. Ag element is uniformly distributed in the matrix structure in the form of solid solution and nano-particles, which can continuously release Ag + ions in the physiological environment and play a long-acting antibacterial effect. At the same time, the refined microstructure and uniformly distributed strengthening phase work together to significantly improve the mechanical properties of the material through grain boundary strengthening and precipitation strengthening mechanisms, so that the implant maintains the super-elasticity of NiTi alloy while the compressive strength reaches more than 3400MPa, realizing the synergistic improvement of high strength and antibacterial function.

[0016] The present application establishes a reliable process-performance correspondence by optimizing the laser powder bed fusion process parameters. A specific laser power and scanning speed combination ensures appropriate energy density input, avoiding both un-melted defects and over-burning phenomena. A scanning spacing of 0.06-0.07 mm and a powder laying thickness of 0.03 mm ensure good overlap between the melt tracks and inter-layer metallurgical bonding, forming a dense and uniform microstructure. A substrate preheating of 40-80℃ effectively reduces the thermal stress during the forming process, preventing cracks. Precise control of the protective atmosphere ensures the stability of the forming process. The prepared implant has stable performance: the elastic modulus is not more than 30 GPa, which is well matched with the bone tissue; the antibacterial rate is not less than 95%, providing reliable infection protection for implant surgery.

[0017] Of course, the implementation of any product of the present application does not necessarily require the simultaneous achievement of all the advantages described above. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0019] Figure 1 SEM images of the NiTiAg powder after ball milling in Examples 1-5; Figure 2 Compression stress-strain curves of the load-bearing bone implants in Examples 1-5, 120W represents Example 1, 140W represents Example 2, and 160W represents Example 3. Figure 3 Antibacterial performance graph of Example 4, where Control sample is the control group, and 140-600 represents Example 4. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0021] The mass percentage of Ag powder in the NiTi alloy powder and Ag powder as described in the present embodiment is 1-5 wt.%, and the mass percentage of NiTi alloy powder is 95-99 wt.%.

[0022] In the embodiment, the particle size of the NiTi alloy powder and the Ag powder is 15-53 μm, the Ag powder is uniformly distributed in the titanium alloy powder, and the sphericity is good.

[0023] In the embodiment, the laser power parameter of the laser powder bed fusion technology is 120-160 W, the scanning speed is 600-1000 mm / s, the scanning interval is 60-70 μm, the powder laying thickness is 20-30 μm, and the spot diameter is 40-60 μm.

[0024] In the embodiment, the acid immersion solution is a mixed solution prepared from concentrated HF, concentrated HNO3 and H2O, and the volume ratio of HF:HNO3:H2O in the mixed solution is 1:(2-4):(5-8).

[0025] In the embodiment, the argon concentration of the high-purity argon is above 99.999%.

[0026] Example 1 The preparation method of the medical high-strength and high-antibacterial load-bearing bone implant as described in the embodiment comprises the following steps: S1: design the required load-bearing bone implant by using a three-dimensional modeling software, export the model designed by the three-dimensional modeling software into an STL format file, and slice the STL three-dimensional model by using a slicing software.

[0027] S2: import the sliced model obtained in step S1 into a selective laser melting device, place the NiTiAg mixed powder in the powder bin of the device, the Ag element accounts for 3% by mass ratio, the Ni element accounts for 55.47% by mass ratio, and the rest is the Ti element, close the chamber of the device and start pumping, then fill in high-purity argon, and perform selective melting of the electron beam under the high-purity argon atmosphere, set the laser power parameter to 120 W, the scanning speed to 1000 mm / s, the scanning interval to 0.07 mm, and the powder laying thickness to 0.03 mm; after the electron beam finishes scanning in one layer, perform powder laying; form layer by layer until the structure is formed, and complete printing.

[0028] S3: remove the structure obtained in step S2 after cooling to room temperature in the high-purity argon atmosphere, and obtain an alloy sample.

[0029] S4: place the porous structure obtained in step S3 in a beaker, pour alcohol into the beaker to cover the sample, then place it in an ultrasonic cleaning instrument for cleaning, then replace the alcohol, and repeat for 5-6 times to completely remove the excess powder, and obtain the medical high-strength and high-antibacterial implant biomaterial after cleaning.

[0030] The mechanical properties of the NiTiAg biomaterial prepared in the embodiment are tested as follows: the elastic modulus is 30 GPa, the yield strength is 671 / 1220 MPa, the compressive strength is 3591 MPa, and the antibacterial rate is above 95%, the material has high strength, low elastic modulus, and meets the mechanical compatibility requirements of the implant.

[0031] Example 2 The preparation method of the medical high-strength and high-antibacterial load-bearing bone implant as described in the embodiment comprises the following steps: S1: design the required load-bearing bone implant by using a three-dimensional modeling software, export the model designed by the three-dimensional modeling software into an STL format file, and slice the STL three-dimensional model by using a slicing software.

[0032] S2: import the sliced model obtained in step S1 into a selective laser melting device, and place the NiTiAg mixed powder in the powder bin of the device, the Ag element accounts for 3% by mass ratio, the Ni element accounts for 55.47% by mass ratio, and the rest is Ti element, close the chamber of the device, start pumping, then fill high-purity argon, and perform selective melting under the high-purity argon atmosphere, set the laser power parameter to 140 W, the scanning speed to 1000 mm / s, the scanning interval to 0.07 mm, and the powder laying thickness to 0.03 mm; after the scanning of the electron beam in a layer is completed, perform powder laying; form layer by layer until the structure is formed, and complete the printing.

[0033] S3: remove the structure obtained in step S2 after cooling to room temperature in the high-purity argon atmosphere, and obtain an alloy sample.

[0034] S4: place the porous structure obtained in step S3 in a beaker, pour alcohol into the beaker to cover the sample, then place it in an ultrasonic cleaning instrument, replace the alcohol repeatedly for 5-6 times, completely remove the excess powder, and obtain the medical high-strength and high-antibacterial implant biomaterial after the cleaning is completed.

[0035] The mechanical properties of the NiTiAg biomaterial prepared in the embodiment are tested as follows: the elastic modulus is 28 GPa, the yield strength is 544 / 1025 MPa, the compressive strength is 3543 MPa, and the antibacterial rate is above 95%, the material has high strength, low elastic modulus, and meets the mechanical compatibility requirements of the implant.

[0036] Example 3 The preparation method of the medical high-strength and high-antibacterial load-bearing bone implant as described in the embodiment comprises the following steps: S1: design the required load-bearing bone implant by using a three-dimensional modeling software, export the model designed by the three-dimensional modeling software into an STL format file, and slice the STL three-dimensional model by using a slicing software.

[0037] S2: The slice model obtained in step S1 is imported into a selective laser melting device, and a NiTiAg mixed powder is placed in the powder bin of the device, the Ag element accounts for 3% by mass in the NiTiAg mixed powder, the Ni element accounts for 55.47% by mass, and the rest is Ti element, the chamber of the device is closed and gas pumping is started, then high-purity argon is filled, selective melting is carried out under the high-purity argon atmosphere, the laser power parameter is set to 160W, the scanning speed is 1000mm / s, the scanning interval is 0.07mm, and the powder laying thickness is 0.03mm; after the electron beam finishes scanning a layer, powder laying is carried out; one layer after another is formed until the structure is formed, and the printing is completed.

[0038] S3: The structure obtained in step S2 is removed after being cooled to room temperature in a high-purity argon atmosphere to obtain an alloy sample.

[0039] S4: The porous structure obtained in step S3 is placed in a beaker, alcohol is poured into the beaker to cover the sample, and then the beaker is placed in an ultrasonic cleaning instrument for cleaning, then the alcohol is replaced, and the process is repeated 5-6 times to completely remove the excess powder. After cleaning, a medical high-strength and high-antibacterial implant biomaterial is obtained.

[0040] The mechanical properties of the NiTiAg biomaterial prepared in this example are tested as follows: the elastic modulus is 27GPa, the yield strength is 529 / 1023MPa, the compressive strength is 3490MPa, and the antibacterial rate is above 95%. The material has high strength and low elastic modulus, which meets the mechanical compatibility requirements of implants.

[0041] Example 4 A method for preparing a medical high-strength and high-antibacterial load-bearing bone implant is provided, which comprises the following steps: S1: A three-dimensional modeling software is used to design a load-bearing bone implant, and the model designed by the three-dimensional modeling software is exported as an STL format file, and the STL three-dimensional model is sliced by a slicing software.

[0042] S2: The slice model obtained in step S1 is imported into a selective laser melting device, and a NiTiAg mixed powder is placed in the powder bin of the device, the Ag element accounts for 3% by mass in the NiTiAg mixed powder, the Ni element accounts for 55.47% by mass, and the rest is Ti element, the chamber of the device is closed and gas pumping is started, then high-purity argon is filled, selective melting is carried out under the high-purity argon atmosphere, the laser power parameter is set to 160W, the scanning speed is 1000mm / s, the scanning interval is 0.07mm, and the powder laying thickness is 0.03mm; after the electron beam finishes scanning a layer, powder laying is carried out; one layer after another is formed until the structure is formed, and the printing is completed.

[0043] S3: The structure obtained in step S2 is removed after being cooled to room temperature in a high-purity argon atmosphere to obtain an alloy sample.

[0044] S4: The porous structure obtained in step S3 is placed in a beaker, alcohol is poured into the beaker to cover the sample, and then the sample is placed in an ultrasonic cleaning instrument for cleaning. Then the alcohol is replaced, and the process is repeated 5-6 times to completely remove the excess powder. After cleaning is completed, a medical high-strength and high-antibacterial implant biomaterial is obtained.

[0045] The mechanical properties of the NiTiAg biomaterial prepared in this example are tested as follows: the elastic modulus is 27 GPa, the yield strength is 620 / 1100 MPa, the compressive strength is 3533 MPa, and the antibacterial rate is above 95%. The material has high strength and low elastic modulus, which meets the mechanical compatibility requirements of implants.

[0046] Example 5 A method for preparing a medical high-strength and high-antibacterial load-bearing bone implant is described in this example, which comprises the following steps: S1: A three-dimensional modeling software is used to design a load-bearing bone implant, and the model designed by the three-dimensional modeling software is exported as an STL format file. The STL three-dimensional model is sliced by a slicing software.

[0047] S2: The sliced model obtained in step S1 is imported into a selective laser melting device, and a NiTiAg mixed powder is placed in the powder bin of the device. The Ag element accounts for 3% by mass ratio, the Ni element accounts for 55.47% by mass ratio, and the rest is Ti element in the NiTiAg mixed powder. The chamber of the device is closed, and then the gas is pumped out and high-purity argon is filled. The selective melting is carried out under the high-purity argon atmosphere. The laser power parameter is set to 140 W, the scanning speed is 800 mm / s, the scanning interval is 0.07 mm, and the powder laying thickness is 0.03 mm. After the electron beam finishes scanning on one layer, the powder is laid. One layer after another is formed until the structure is formed, and the printing is completed.

[0048] S3: The structure obtained in step S2 is removed after being cooled to room temperature in a high-purity argon atmosphere to obtain an alloy sample.

[0049] S4: The porous structure obtained in step S3 is placed in a beaker, alcohol is poured into the beaker to cover the sample, and then the sample is placed in an ultrasonic cleaning instrument for cleaning. Then the alcohol is replaced, and the process is repeated 5-6 times to completely remove the excess powder. After cleaning is completed, a medical high-strength and high-antibacterial implant biomaterial is obtained.

[0050] The mechanical properties of the NiTiAg biomaterial prepared in the embodiment are tested as follows: the elastic modulus is 27 GPa, the yield strength is 650 / 1128 MPa, the compressive strength is 3742 MPa, and the antibacterial rate is above 95%, the material has high strength, low elastic modulus, and meets the mechanical compatibility requirements of the implant.

[0051] In conclusion, the application provides a preparation method of a medical high-strength and high-antibacterial load-bearing bone implant, 1-5 wt.% of silver powder is mixed with 95-99 wt.% of nickel-titanium alloy powder by laser powder bed fusion technology, and 3D printing is performed in a low-oxygen environment. By optimizing the key process parameters such as laser power and scanning speed, the uniform distribution of silver elements and the dispersion strengthening of the second phase are realized, and the comprehensive performance of the material is significantly improved. The obtained implant has high density, high strength and high antibacterial property, the compressive strength can reach 3400-3800 MPa, the elastic modulus is close to human bone, the antibacterial rate of staphylococcus aureus and escherichia coli is more than 95%, and the inherent super-elasticity and shape memory effect of the nickel-titanium alloy are maintained, and it is especially suitable for orthopedic implants such as intervertebral fusion cages and artificial joints in high-load parts.

[0052] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details, nor limit the application to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of the specification. The specification selects and describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for producing a medical high-strength high-antibacterial load-bearing bone implant, characterized by, The method comprises the following steps: providing a NiTi alloy powder and an Ag powder, mixing the two to form a mixed powder with an Ag element mass percentage of 1-5%; using a laser powder bed melting technology to layer-by-layer melt and solidify the mixed powder in a protective atmosphere, wherein the laser power is controlled to be 120-160 W, and the scanning speed is 600-1000 mm / s; post-processing the formed component to obtain the load-bearing bone implant.

2. The method of making a medical high strength high antibacterial load bearing bone implant according to claim 1, wherein: Before the laser powder bed melting forming, the method further comprises designing a load-bearing bone implant structure model by using a three-dimensional modeling software, and importing the model into a printing device.

3. The method of making a medical high strength high antibacterial load bearing bone implant according to claim 1, wherein: The mass percentage of Ni in the NiTi alloy powder is 56 wt.%, and the mass percentage of Ti is 44 wt.%. The particle size of the NiTi alloy powder and the Ag powder is 15-53 μm.

4. The method of making a medical high strength high antibacterial load bearing bone implant according to claim 1, wherein: The protective atmosphere is an atmosphere with an oxygen content of less than 0.1% obtained by first vacuumizing to an oxygen content of less than 100 ppm, and then filling in inert gas. The inert gas is argon with a purity of greater than or equal to 99.9%.

5. The method of making a medical high strength high antibacterial load bearing bone implant according to claim 1, wherein: In the laser powder bed melting forming process, the process parameters further include a scanning interval of 0.06-0.07 mm and a powder laying thickness of 0.03 mm.

6. The method of making a medical high strength high antibacterial load bearing bone implant according to claim 1, wherein: In the laser powder bed melting forming process, the printing substrate is preheated to 40-80°C.

7. The method of making a medical high strength high antibacterial load bearing bone implant according to claim 1, wherein: The post-processing comprises separating the formed component from the substrate by wire cutting, and a cleaning step: placing the implant in a 95% anhydrous ethanol solution for ultrasonic cleaning for 5-10 minutes, replacing the ethanol and repeating for 3-4 times.

8. The method of making a medical high strength high antibacterial load bearing bone implant according to claim 1, wherein: The post-processing after the cleaning step further comprises an acid pickling step: using an acid pickling solution prepared from concentrated HF, concentrated HNO3 and H2O in a volume ratio of 1:(2-4):(5-8) to acid pickle the implant.

9. A medical high-strength high-antibacterial load-bearing bone implant, characterized by: The load-bearing bone implant prepared by the method of any one of claims 1-8 has a yield strength of not less than 500 MPa, a compressive strength of not less than 3400 MPa, an elastic modulus of not higher than 30 GPa, and an antibacterial rate of not less than 95%.

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