Titanium alloy surface antibacterial material and preparation method and application thereof

Abstract

The application provides a titanium alloy surface antibacterial material and a preparation method and application thereof, and comprises a metal phosphide coating constructed on a titanium alloy substrate surface through a plasma immersion injection process and a chemical vapor treatment process and application of the metal phosphide coating in antibacterial medical materials. The coating of the technical scheme has good sterilization function and biocompatibility.

Description

Technical Field

[0001] This invention relates to the field of medical biomaterial preparation technology, and more specifically, to the preparation and application of an antibacterial coating material for the surface of medical titanium alloy materials. Background Technology

[0002] With an aging population and the need for high-quality development of healthcare, people's requirements for the quality of medical implants are constantly increasing. Titanium alloys have good mechanical properties and biocompatibility, but their surface inertness makes them susceptible to bacterial infection, which can lead to implant failure. Imbuing the material surface with bioactivity is an important direction for the research and development of implantable devices.

[0003] Bacterial infection is a significant complication of implants. It is difficult to eradicate completely, poses serious risks, often leads to implant failure, and increases the cost of secondary treatment. Antibiotics are the primary treatment for bacterial infections; however, with the overuse of antibiotics, the problem of increasing antibiotic resistance in microorganisms is becoming increasingly prominent. Exploring antibiotic alternatives to effectively kill bacteria holds promise for mitigating the antibiotic crisis.

[0004] Coating technology can enable bio-inert materials to exert specific biological effects, but most coating modification processes face the problem of insufficient coating bonding strength. Ionization implantation can construct a nanoscale uniform coating on the surface without compromising the material's inherent mechanical properties. The implanted ions are diffusely distributed on the surface, without creating a noticeable coating interface. This comprehensive modification technology can be adapted to a wide variety of complex implantable devices, and the modified coating exhibits excellent bonding strength. Summary of the Invention

[0005] To address the problems in the prior art, the present invention aims to provide an antibacterial material for titanium alloy surfaces, its preparation method, and its application.

[0006] On one hand, the present invention provides an antibacterial material for titanium alloy surfaces, comprising a titanium alloy substrate and a modified coating on the surface of the titanium alloy substrate, wherein the modified coating comprises a metal phosphide.

[0007] Preferably, the metal phosphide is a transition metal phosphide.

[0008] Preferably, the metal phosphide is cuprous phosphide.

[0009] Preferably, the loading of metallic copper in the modified coating is less than 10 at.%.

[0010] Preferably, the metal phosphide coating is constructed on the surface of a titanium alloy substrate by chemical vapor deposition.

[0011] Preferably, the metal on the surface of the titanium alloy substrate is injected using a plasma immersion injection process.

[0012] Preferably, the titanium alloy substrate is a nickel-titanium alloy material.

[0013] On the other hand, the present invention provides a method for preparing the above-mentioned antibacterial material on the surface of titanium alloy, comprising the following steps:

[0014] Step 1: Metal is injected into the surface of the titanium alloy substrate using a plasma immersion injection process;

[0015] Step 2: Construct a metal phosphide coating on the surface of the titanium phosphide alloy substrate using a chemical vapor deposition process.

[0016] Preferably, the plasma immersion injection process parameters are: a background vacuum of 3 × 10⁻⁶. -3 ~5×10 -3 Pa, injection voltage of -10 to -40 kV, injection pulse width of 500 to 1000 μs, injection pulse frequency of 5 to 15 Hz, cathode source trigger pulse width of 500 to 2000 μs, and injection time of 30 to 180 minutes.

[0017] On the other hand, the present invention provides the application of the above-mentioned antibacterial material on the surface of titanium alloy in antibacterial medical materials.

[0018] The coating material of this invention is an in-situ grown metal phosphide coating, which possesses nanoscale properties, good adhesion, uniform dispersion, and a hydrophilic surface. Simultaneously, the modified coating endows the titanium material surface with potent bactericidal properties against *Escherichia coli*, *Staphylococcus aureus*, and *Proteus mirabilis*, while exhibiting good biocompatibility with normal cells. This coating material provides a new approach for the design and development of novel antibacterial implants for clinical use, demonstrating promising application prospects. Attached Figure Description

[0019] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0020] Figure 1 The images are scanning electron microscope (SEM) images of the materials, where NiTi represents the unmodified sample, NiTi-Cu represents the sample with copper ion implantation, and NiTi-Cu-P represents the sample with copper phosphating.

[0021] Figure 2 denoted as the water contact angle of the material, where NiTi represents the unmodified sample, NiTi-Cu represents the sample with copper ion implantation, and NiTi-Cu-P represents the sample with copper phosphating.

[0022] Figure 3XPS elemental spectrum of the material surface ( Figure 3 -a) and Cu2p on the surface of each group of samples Figure 3 -b), Ni2p( Figure 3 -c), P2p( Figure 3 -d) High-resolution spectrum;

[0023] Figure 4 The results of antibacterial experiments on Escherichia coli, Staphylococcus aureus, and Proteus mirabilis (E. coli represents Escherichia coli, S. aureus represents Staphylococcus aureus, and P. mirabilis represents Proteus mirabilis) are shown. NiTi represents the unmodified sample, NiTi-Cu represents the sample with copper ion implantation, and NiTi-Cu-P represents the sample with copper phosphating.

[0024] Figure 5 Scanning electron microscopy (SEM) images of Escherichia coli, Staphylococcus aureus, and Proteus mirabilis on the material surface (E. coli represents Escherichia coli, S. aureus represents Staphylococcus aureus, and P. mirabilis represents Proteus mirabilis). NiTi represents the unmodified sample, NiTi-Cu represents the sample with copper ion implantation, and NiTi-Cu-P represents the sample with copper phosphating.

[0025] Figure 6 The results of the initial adhesion and spreading experiment of ureteral epithelial cells on the material surface are shown. NiTi represents the unmodified sample, NiTi-Cu represents the sample with copper ion implantation, and NiTi-Cu-P represents the sample with copper phosphating.

[0026] Figure 7 The results show the proliferation activity of ureteral epithelial cells on the material surface. NiTi represents the unmodified sample, NiTi-Cu represents the sample with copper ion implantation, and NiTi-Cu-P represents the sample with copper phosphating.

[0027] Figure 8 The results of the live / dead staining experiment of ureteral epithelial cells after culturing on the material surface for 4 days are shown. NiTi represents the unmodified sample, NiTi-Cu represents the sample with copper ion implantation, and NiTi-Cu-P represents the sample with copper phosphating. Detailed Implementation

[0028] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted.

[0029] This invention provides an antibacterial material for titanium alloy surfaces, comprising a titanium alloy substrate and a modified coating on the surface of the titanium alloy substrate, wherein the modified coating comprises a metal phosphide.

[0030] The coating material is first injected into the surface of the titanium alloy by plasma immersion injection process, and then a metal phosphide coating is formed in situ on the surface of the titanium alloy by chemical vapor deposition process. The coating includes phosphine gas and the ion-implanted coating on the surface of the titanium alloy reacting to form phosphide at a certain temperature.

[0031] Nickel-titanium alloy is the preferred titanium alloy material.

[0032] Preferably, the metal ion-implanted onto the titanium alloy surface is a transition metal, and more preferably copper, and the implanted copper exists in the coating in the form of elemental or oxide. More preferably, cuprous phosphide is formed on the titanium alloy surface after phosphating treatment.

[0033] Furthermore, the preferred surface coating has a copper loading of less than 10 at.%.

[0034] In the plasma immersion injection process, the following process parameters are preferred: a base vacuum of 3 × 10⁻⁶. -3 ~5×10 -3 Pa (e.g., 3, 4 or 5 × 10) -3 The injection voltage is -10 to -40 kV (e.g., -10, -15, -20, -30 or -40 kV), the pulse width is 500 to 1000 μs (e.g., 500, 600, 700 or 800 μs), the frequency is 5 to 15 Hz (e.g., 5, 6, 7, 8, 9 or 10 Hz), and the injection time is 0.5 to 3 hours (e.g., 0.5, 1.0, 1.5, 2.0, 2.5 or 3.0 hours).

[0035] The background vacuum level is 5×10⁻⁶. -3 Pa, injection voltage of -15kV, pulse width of 500-800μs (e.g., 500, 600, 700 or 800μs), frequency of 10Hz, and injection time of 2-3 hours (e.g., 2, 2.5 or 3 hours).

[0036] Nickel-titanium is preferred as the substrate, and pure copper is used as the cathode.

[0037] The ion-implanted metal exists mainly in the metallic state within the modified layer, while the surface of the modified layer exists in the oxidized state, and there is no clear boundary between the modified layer and the substrate layer.

[0038] In addition, it is preferable to treat and wash the substrate with an acid pickling solution before performing plasma immersion ion implantation. The acid pickling solution is preferably a mixture of nitric acid and hydrofluoric acid; further preferably, the washing step involves ultrasonic cleaning sequentially using acetone, ethanol, and deionized water.

[0039] In chemical vapor phase reactions, a dual-temperature zone vacuum tube furnace is preferred for operation under programmed temperature control. Phosphine gas is generated by heating a phosphorus-containing precursor in the tube furnace, which is placed upstream of the gas flow, while the material to be modified is placed downstream of the gas flow.

[0040] Phosphite precursor is preferably used as phosphorus source. The precursor decomposes upon heating to produce phosphine gas. Sodium hypophosphite is preferably used as phosphorus source.

[0041] An inert gas is preferably selected as the protective gas, and argon is preferably selected as the protective gas, with a flow rate of 20 to 100 sccm.

[0042] The preferred phosphating reaction temperature is 250–500℃, the heating rate is 2–10℃ / min, and the holding time is 0.5–3h. Preferably, the reaction temperature is set to 300℃, the heating rate is 2℃ / min, and the holding time is 2h.

[0043] The method of this invention is stable and controllable, simple to operate, and can modify in all directions without being limited by the shape of the workpiece. The metal phosphide coating has nanoscale uniform dispersion and good bonding. Moreover, this process is suitable for workpieces with complex shapes and has applications in the biomedical field, especially in antibacterial applications.

[0044] The present invention will now be described with reference to specific embodiments and comparative examples:

[0045] Example 1

[0046] Substrate: A 12mm×12mm×1mm nickel-titanium sheet was ultrasonically treated twice with a mixed acid (hydrofluoric acid: nitric acid: deionized water = 1:5:4) (5 minutes each time), and then ultrasonically cleaned twice with deionized water and ethanol, 5 minutes each time, to obtain a nickel-titanium alloy sheet with a smooth surface. The resulting material was named NiTi.

[0047] Copper was implanted into a nickel-titanium matrix using plasma immersion ion implantation technology, named NiTi-Cu. The specific process parameters are shown in Table 1.

[0048] Table 1. Copper ion implantation and deposition parameters

[0049] parameter Target cathode Voltage (kV) -15 - Frequency (Hz) 10 10 Pulse width (μs) 500 800 Time (min) 120 -

[0050] The ion-implanted copper-copper nickel-titanium sample was placed downstream of the gas in a dual-temperature zone tube furnace. 200 mg of sodium hypophosphite (monohydrate) powder was weighed, dispersed in an alumina ceramic boat, and placed upstream of the gas in the tube furnace. The tube furnace heating program parameters were set as follows: under an argon atmosphere, the temperature was increased from room temperature to 300°C at a rate of 2°C / min, held for 2 hours, and the exhaust gas was carefully disposed of. The phosphated material was named NiTi-Cu-P.

[0051] Evaluation of the surface physicochemical properties of the material:

[0052] like Figure 1 As shown, the surface morphology of the NiTi sample is smooth and clean, while the surface of the NiTi-Cu sample exhibits nano-grooves after being bombarded by high-energy plasma, and the micro-level of the NiTi-Cu-P sample forms closely linked nano-hills.

[0053] Figure 2 The contact angle of the sample surface to water is shown. The wettability of the material surface affects behaviors such as protein deposition and cell adhesion. The contact angle of the chemically acid-washed NiTi surface is approximately 87°, while that of the NiTi-Cu implanted sample surface decreases to 73°. After Cu implantation, the surface forms micro-nano structures, making it more hydrophilic. The contact angle of the NiTi-Cu-P sample further decreases to 49°, which is due to the formation of P-OH groups through hydration of the PO bonds on the sample surface, which is beneficial for water molecule adsorption.

[0054] like Figure 3 As shown, the ion-implanted copper is mainly elemental Cu and Cu2+. 2+ Cu after phosphating 2+ The peaks essentially disappeared, and copper existed as elemental Cu and Cu. + exist( Figure 3 b) It is worth noting that nickel ions move from Ni before and after phosphating. 3+ Restored to Ni 2+ ( Figure 3 c) The P2p peak on the surface indicates that phosphorus is bonded to the metal, while the PO peak is generated by the oxidation of the surface coating.

[0055] Evaluation of the antibacterial properties of the material:

[0056] The materials were immersed in a 75% ethanol solution and shaken on a shaker, with the solution changed every 30 minutes. After sterilization for 2 hours, they were air-dried for later use. In experiments with *E. coli* (ATCC 25922) and *S. aureus* (ATCC 25923), the bacterial solution was adjusted to an absorbance of 0.1 at 600 nm using TSB medium, then diluted 10-fold with physiological saline. The bacterial density was approximately 10⁷ CFU / mL, and the bacteria were grown at a density of 0.06 mL / cm³. 2 In the experiment with *Proteus mirabilis* (ATCC 35659), the bacterial solution was adjusted to an absorbance of 0.1 at 600 nm using culture medium. It was then diluted 10-fold with culture medium and further diluted 10-fold with physiological saline before use, resulting in a bacterial density of approximately 10⁶ CFU / mL. The bacteria were inoculated onto the material surface at a rate of 0.06 mL / cm² and incubated at 37°C for 24 hours. After incubation, the bacterial solution was serially diluted and inoculated onto solid agar medium, incubated at 37°C for 12-14 hours before being photographed. After inoculating the bacteria onto the material surface and incubating at 37°C for 24 hours, the bacterial morphology was fixed with 2.5% glutaraldehyde, dehydrated, and observed using a scanning electron microscope.

[0057] like Figure 4 As shown in the bacterial agar plate coating, NiTi-Cu-P exhibits an inhibition rate of nearly 100% against Escherichia coli, Staphylococcus aureus, and Proteus mirabilis.

[0058] like Figure 5 As shown, a large number of E. coli, S. aureus, and P. mirabilis are uniformly distributed on the surface of NiTi and NiTi-Cu samples, while there are very few bacteria on the surface of NiTi-Cu-P samples, and the cell membranes show obvious damage.

[0059] Biocompatibility evaluation of materials:

[0060] The material was immersed in a 75% ethanol solution and shaken on a shaker, with the solution changed every 30 minutes. After sterilization for 2 hours, it was air-dried for later use. To evaluate cell adhesion behavior on the material surface, ureteral epithelial cells were seeded at a density of 20,000 cells / well. Cell morphology was fixed with paraformaldehyde at 1, 4, and 24 hours. The cytoskeleton was stained red with rhodamine, and the nuclei were stained blue with DAPI. Cell adhesion and spreading were observed under a fluorescence microscope. To evaluate cell proliferation on the material surface, Alamar Blue was used to test fluorescence intensity at 1, 4, and 7 days to reflect cell proliferation activity. To evaluate cell viability on the material surface, a live / dead staining kit (BioVison, USA) was used. Dead cells stained red, and live cells stained green. After 4 days, the culture medium was removed, and the cells were stained at 37°C for 30 minutes. The staining status was observed under a fluorescence microscope.

[0061] Figure 6 These are fluorescence images showing the initial adhesion and spreading of cells on the sample surface. After 1 hour of culture, the cells in the suspension begin to settle and adhere to the material surface, with a generally spherical morphology. After 4 hours of culture, the cells gradually spread outwards. After 24 hours of culture, the cells transform into a more elongated shape. Notably, NiTi-Cu and NiTi-Cu-P samples promote early cell adhesion and spreading.

[0062] like Figure 7 As shown, compared with the NiTi sample, the cell proliferation activity of both NiTi-Cu and NiTi-Cu-P samples was reduced, but the cells in each group were in a growth state at 1 day, 4 days and 7 days after cell seeding.

[0063] like Figure 8 As shown, the cells can be evenly spread on the surface of the NiTi-Cu-P sample, and no dead cells were observed with the naked eye, indicating that the modified coating has good biocompatibility.

[0064] In summary, the method of this invention is stable and controllable, simple to operate, and can modify workpieces in all directions without being limited by shape. The prepared coating has good antibacterial properties and excellent biocompatibility.

[0065] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A titanium alloy surface antibacterial material, characterized in that, The process includes a titanium alloy substrate and a modified coating on the surface of the substrate. The modified coating includes a metal phosphide, specifically cuprous phosphide. The titanium alloy substrate is a nickel-titanium alloy. Metal is implanted onto the surface of the titanium alloy substrate using a plasma immersion injection process. A metal phosphide coating is then constructed on the surface of the titanium alloy substrate using a chemical vapor deposition (CVD) process. The plasma immersion injection process parameters are a base vacuum of 3 × 10⁻⁶. -3 ~5×10 -3 Pa, injection voltage of -10 to -40 kV, injection pulse width of 500 to 1000 μs, injection pulse frequency of 5 to 15 Hz, cathode source trigger pulse width of 500 to 2000 μs, and injection time of 30 to 180 minutes.

2. The antibacterial material for titanium alloy surfaces according to claim 1, characterized in that: The loading of metallic copper in the modified coating is less than 10 at.

3. The application of the titanium alloy surface antibacterial material according to claim 1 in antibacterial medical materials.

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