A porous tantalum surface strontium-doped hydroxyapatite and polydopamine composite coating, and a preparation method and application thereof

Abstract

This invention relates to the field of new materials technology, and discloses a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface, its preparation method, and its application. The method first prepares strontium-doped hydroxyapatite powder capable of continuously releasing strontium ions by precipitating calcium, strontium, and phosphorus sources in a predetermined ratio under alkaline conditions. Subsequently, this powder is mixed with dopamine in a weakly alkaline buffer solution to form a reaction solution. Through in-situ polymerization of dopamine, a composite coating containing strontium-doped hydroxyapatite and polydopamine is constructed on the porous tantalum surface. Through integrated structural design, the three functions of osteogenic properties, photothermal antibacterial properties, and interface strengthening are organically integrated and mutually promoted. This fundamentally solves the defects of existing hard tissue implant materials, such as single function, difficulty in simultaneously achieving antibacterial and osteogenic properties, and insufficient long-term stability. It provides a surface modification solution for orthopedic implants that combines excellent antibacterial activity and osteogenic capacity.

Description

Technical Field

[0001] This invention belongs to the field of new materials technology, specifically relating to a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface, its preparation method, and its application. Background Technology

[0002] Hard tissue implants play a crucial role in repairing bone defects caused by trauma, osteoporosis, and congenital defects. With the aging global population and rising incidence of bone-related diseases, the clinical demand for these implants is increasing. Currently, commonly used implant materials mainly include autologous bone, allogeneic bone, and various artificial bone repair materials. Among them, porous tantalum, due to its elastic modulus being similar to that of natural bone and its good biocompatibility, can effectively reduce stress shielding and promote osseointegration, and has become one of the important materials in the field of orthopedic implants. However, porous tantalum itself lacks bioactivity and antibacterial function, making it prone to infection in complex physiological environments, and its surface does not easily form a chemical bond with surrounding bone tissue, thus limiting its long-term implant stability.

[0003] To improve the bioactivity of implant materials, hydroxyapatite (HA), due to its composition similar to bone inorganic matter and its excellent bioactivity and osteoconductivity, is widely used in bone repair. Furthermore, by incorporating strontium ions (Sr... 2+ Active ingredients such as strontium ions can further enhance osteogenic properties. Strontium ions can simultaneously promote osteogenic formation and inhibit osteoclastosis, showing unique potential in osteoporosis treatment and bone regeneration. However, when hydroxyapatite is used alone, its antibacterial properties are insufficient, resulting in a higher risk of postoperative bacterial infection. Furthermore, pure hydroxyapatite has low mechanical strength, limiting its application in weight-bearing areas. Similarly, while strontium ions can promote bone formation when used alone, they lack a synergistic antibacterial mechanism, making it difficult to ensure successful implantation in infected environments.

[0004] To address the risk of bacterial infection after implantation, near-infrared photothermal therapy has been incorporated into the surface modification of implant materials, achieving sterilization through localized heating. Polydopamine (PDA), due to its excellent adhesion and photothermal conversion capabilities, is often used as a surface modification layer to enhance the multifunctionality of materials. However, temperature control in photothermal therapy is challenging; excessively low temperatures fail to completely sterilize, while excessively high temperatures can damage surrounding healthy tissues. Currently, most photothermal materials struggle to achieve safe and controllable antibacterial heating in the implantation environment. Furthermore, existing surface modification methods, such as single PDA coatings, have limited functionality, often only improving material adhesion or providing limited photothermal effects, making it difficult to simultaneously achieve multiple goals such as potent antibacterial activity, bone promotion, and long-term stable integration. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a porous tantalum surface strontium-doped hydroxyapatite and polydopamine composite coating, its preparation method and application, so as to solve the technical problems of existing hard tissue implant materials having single function, difficulty in achieving both antibacterial and osteogenic properties, and insufficient long-term stability.

[0006] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a method for preparing a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface, comprising the following steps: Step 1: Dissolve calcium, strontium, and phosphorus sources in water in a predetermined ratio, and carry out a precipitation reaction under alkaline conditions. After separation, washing, and drying, strontium-doped hydroxyapatite powder is obtained. Step 2: Disperse the strontium-doped hydroxyapatite powder obtained in Step 1 in a weakly alkaline buffer solution, add dopamine or its salt, and mix well to form a reaction solution; immerse porous tantalum in the reaction solution to allow dopamine to polymerize; after the reaction is complete, remove the porous tantalum, wash and dry it to form a composite coating of strontium-doped hydroxyapatite and polydopamine on the surface of the porous tantalum.

[0007] A further improvement of the present invention is that the calcium source is calcium nitrate, calcium chloride, or calcium acetate; the phosphorus source is disodium hydrogen phosphate, diammonium hydrogen phosphate, or diammonium dihydrogen phosphate; and the strontium source is strontium nitrate or strontium chloride.

[0008] A further improvement of the present invention is that, in step 1, the alkaline condition is achieved by adjusting the pH of the reaction system to 9.0~11.0 by adding sodium hydroxide solution and / or hydrochloric acid solution.

[0009] A further improvement of the present invention is that, in step 1, the predetermined ratio results in a molar substitution of strontium ions for calcium ions of 0.5% to 20%.

[0010] A further improvement of the present invention is that, in step 2, the weakly alkaline buffer solution is a tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution with a pH value of 7.5 to 8.5.

[0011] A further improvement of the present invention is that, in step 2, the dopamine or its salt is dopamine hydrochloride, and its final concentration in the reaction solution is 0.2~5 mg / mL.

[0012] A further improvement of the present invention is that, in step 2, the dispersion concentration of the strontium-doped hydroxyapatite powder in the weakly alkaline buffer solution is 0.1~10 mg / mL.

[0013] A further improvement of the present invention is that, in step 2, the polymerization reaction of the dopamine is carried out at room temperature for a reaction time of 20 to 30 hours.

[0014] Secondly, the present invention also provides a surface-modified porous tantalum implant, the surface of which has a strontium-doped hydroxyapatite and polydopamine composite coating formed by the above preparation method.

[0015] Thirdly, the present invention also provides the application of the surface-modified porous tantalum implant as described above in the preparation of medical devices for bone defect repair.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface. The method first involves a precipitation reaction of calcium, strontium, and phosphorus sources in a predetermined ratio under alkaline conditions to prepare strontium-doped hydroxyapatite powder capable of continuously releasing strontium ions. This powder is then mixed with dopamine in a weakly alkaline buffer solution to form a reaction solution. Through in-situ polymerization of dopamine, a composite coating containing strontium-doped hydroxyapatite and polydopamine is constructed on the porous tantalum surface. In the resulting coating, polydopamine's excellent adhesion ensures a strong bond between the coating and the porous tantalum substrate, significantly improving the long-term stability and biocompatibility of the implant interface. Simultaneously, polydopamine imparts near-infrared photothermal response characteristics to the material, enabling a controllable photothermal effect under in vitro near-infrared light irradiation. This achieves non-invasive, spatiotemporally controllable local physical antibacterial effects, effectively solving the problem of deep postoperative infections. Strontium-doped hydroxyapatite, through the continuous release of strontium ions, synergistically enhances osteoconductivity and osteoinductive properties, actively promoting osteoblast activity and new bone formation. This method, through integrated structural design, organically integrates and mutually promotes the three functions of osteopromoting, photothermal antibacterial properties, and interface strengthening. It fundamentally solves the shortcomings of existing hard tissue implant materials, such as single function, difficulty in simultaneously achieving antibacterial and osteogenic properties, and insufficient long-term stability. It provides a surface modification solution for orthopedic implants that combines excellent antibacterial activity with osteopromoting capabilities.

[0017] This invention also provides a surface-modified porous tantalum implant. Its three-dimensional interconnected pore structure provides ideal space for bone tissue ingrowth and fluid transport, while the firmly bonded strontium-doped hydroxyapatite and polydopamine composite coating on the surface gives it multiple clinical applications. When applied to bone defect repair medical devices, this implant, on the one hand, utilizes the photothermal response properties of polydopamine to achieve non-invasive, on-demand, and precise local antibacterial treatment via in vitro near-infrared light irradiation post-surgery, effectively avoiding the side effects and risks of deep infection associated with systemic medication. On the other hand, the continuously released strontium ions in the coating endow the implant with the ability to actively induce osteogenesis, significantly accelerating new bone formation and implant-bone interface integration. This design, integrating antibacterial function with osteogenic activity, ensures long-term stability of the implant in complex physiological environments while actively participating in bone tissue regeneration, providing a safe, efficient, and controllable innovative solution for clinical bone defect repair. Attached Figure Description

[0018] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way. Furthermore, the shapes and proportions of the components in the drawings are merely illustrative to aid in understanding the invention and do not specifically limit the shapes and proportions of the components of the invention.

[0019] Figure 1 This is a structural diagram of a porous tantalum support with a three-dimensional interconnected hole structure; Figure 2 Scanning electron microscope images and energy dispersive spectroscopy data of different samples. (a) HA sample, (b) SrHA 1 sample, (c) SrHA 2 sample, (d) SrHA 3 sample, (e) SrHA 4 sample.

[0020] Figure 3 SEM images of different samples: (a) HA sample, (b) porous tantalum scaffold encapsulating HA@PDA, (c) SrHA4 sample, (d) SrHA4@PDA sample, (e) TEM image of SrHA4@PDA sample; Figure 4 FTIR spectra of different samples before and after PDA packaging; Figure 5 (a) shows the heating and cooling curves of different liquid samples under laser irradiation, and (b) shows the heating and cooling curves of different Sr... 2+ SrHA@PDA samples with a doping concentration of 1.5 W / cm 2 The temperature curve under laser irradiation, (c) is 1.7 W / cm². 2 Temperature curve under laser irradiation, (d) is 2W / cm 2 Temperature curve under laser irradiation; Figure 6(a) shows colony images of different samples after photothermal incubation with Escherichia coli for 12 hours; (b) shows SEM images of SrHA4 samples before and after photothermal incubation with Escherichia coli and Staphylococcus aureus. Figure 7 The absorbance (490 nm) of MC3T3-E1 cells co-cultured with pure Ta, HA@PDA, and SrHA@PDA for 1, 3, and 7 days is statistically shown. Figure 8 (a) is a macroscopic SEM image of MC3T3-E1 cells cultured on SrHA@PDA sample for 1 day; (b) is a microscopic SEM image of MC3T3-E1 cells cultured on SrHA@PDA sample for 1 day; (c) is a low-magnification SEM image of SrHA@PDA sample immersed in simulated body fluid for 7 days; and (d) is a high-magnification SEM image of SrHA@PDA sample immersed in simulated body fluid for 7 days. Figure 9 SrHA@PDA samples with different doping levels in deionized water (0-21d) 2+ Curve showing the change in precipitated concentration. Detailed Implementation

[0021] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0022] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0023] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0024] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0025] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0026] This invention provides a method for preparing a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface, comprising the following steps: Step 1: Preparation of hydroxyapatite (HA) precipitate 1) Raw materials and proportions: Accurately weigh the calcium and phosphorus source materials, wherein the calcium source is calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and the phosphorus source is disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O). The molar ratio of the two is accurately calculated and weighed based on the stoichiometric ratio of the target hydroxyapatite (Ca / P=1.67).

[0027] 2) Mixing and dissolving: Place the weighed calcium and phosphorus sources in a suitable container (such as a beaker), add sufficient deionized water, and continuously stir mechanically at room temperature until a homogeneous mixed solution is formed.

[0028] 3) pH Adjustment: During stirring, the pH of the above mixed solution was adjusted using a sodium hydroxide (NaOH) solution with a concentration of approximately 3 mol / L and / or a hydrochloric acid (HCl) solution. By adding the solution dropwise and monitoring it in real time, the final pH value of the solution was precisely controlled and stabilized at 10.0±1. This alkaline environment is conducive to the formation and precipitation of hydroxyapatite crystals.

[0029] 4) Reaction and maturation: The pH-adjusted solution was stirred at a constant speed at room temperature for 24 hours to ensure that calcium and phosphorus ions reacted fully and formed a well-crystallized HA precipitate.

[0030] 5) Separation and washing of the precipitate: After the reaction is complete, the solution is centrifuged and the supernatant is discarded to obtain a white precipitate. The precipitate is washed repeatedly with anhydrous ethanol and deionized water to remove residual sodium ions, nitrate ions and other soluble impurities.

[0031] 6) Drying: Transfer the washed HA precipitate to a desiccator and place it in a 60°C forced-air drying oven for 48 hours to finally obtain pure hydroxyapatite (HA) powder.

[0032] Step 2: Preparation of Strontium-doped hydroxyapatite (Sr-HA) 1) Doping design: Based on the pre-designed ion doping formula, determine the molar substitution of strontium (Sr) for calcium (Ca) to be 0.5%~20% (e.g., x=1,5,10, etc.).

[0033] 2) Raw Materials and Batching: Based on the HA synthesis process obtained in Step 1, strontium nitrate (Sr(NO3)2) was selected as the strontium source. During batching, according to the doping ratio, a portion of the calcium source (Ca(NO3)2·4H2O) was replaced by an equimolar amount of strontium nitrate, while the amount of phosphorus source remained unchanged, thereby achieving the desired Sr content in the HA crystal structure. 2+ Partially replaces Ca 2+ .

[0034] 3) Synthesis and Processing: Repeat steps 2 to 6 of section 1 (mixing, pH adjustment, reaction, washing, drying), but use the adjusted calcium-strontium mixed raw material. The final result is strontium-doped hydroxyapatite (Sr-HA) powders with different strontium doping levels (e.g., ...). Figure 2 (As shown).

[0035] Step 3: Construction of the polydopamine (PDA) composite coating 1) Matrix pretreatment: Provide porous tantalum scaffolds with a three-dimensional interconnected hole structure (such as...) Figure 1 (As shown). The bracket can be pre-cleaned (e.g., ultrasonically cleaned with ethanol or deionized water) and dried to ensure a clean surface.

[0036] 2) Preparation of the reaction system: Prepare a 10 mM Tris-HCl buffer solution with a pH of 7.5-8.5. Weigh 0.1 g of the Sr-HA powder prepared in step 2 (or the pure HA powder prepared in step 1 as a control) and add it to 50 mL of the above Tris-HCl buffer solution. Disperse by sonication or mechanical stirring for 10 minutes to form a uniform suspension.

[0037] 3) Addition of dopamine solution: Prepare a 1 mg / mL dopamine hydrochloride aqueous solution. Add 50 mL of the dopamine hydrochloride aqueous solution to the above suspension. At this point, the total volume of the entire reaction system is approximately 100 mL, and the total mass of dopamine is 50 mg. Specifically, the final concentration of the dopamine hydrochloride aqueous solution in the reaction solution is 0.2~5 mg / mL.

[0038] 4) Impregnation and Polymerization Reaction: The cleaned and dried porous tantalum scaffold is completely immersed in the reaction solution prepared in step 3). The entire system is placed at room temperature and mechanically stirred continuously for 20-30 hours. During this process, dopamine dissolved in the solution undergoes a self-polymerization reaction to generate polydopamine (PDA). Simultaneously, the adhesive properties of PDA cause it to co-deposit with suspended Sr-HA (or HA) nanoparticles and firmly coat all surfaces of the porous tantalum scaffold (including the inner and outer pore walls), forming a uniform composite coating of strontium-doped hydroxyapatite and polydopamine (its microstructure can be found in [reference needed]). Figure 3 ).

[0039] 5) Sample removal and preliminary drying: After the reaction is completed, carefully remove the porous tantalum sample with the composite coating on the surface with tweezers, rinse gently with deionized water to remove loose particles physically adsorbed on the surface, and then place it in a 60°C oven to dry for 24 hours to obtain the coated porous tantalum implant sample (denoted as Sr-HA@PDA / Ta or HA@PDA / Ta).

[0040] The final product of this invention is a surface-modified porous tantalum scaffold. It macroscopically maintains the original three-dimensional porous framework structure (e.g., Figure 1 This structure facilitates bone ingrowth and fluid transport. Microscopically, all surfaces of its framework are covered by a composite coating composed of interwoven strontium-doped hydroxyapatite nanoparticles and a polydopamine polymer matrix (e.g., Figure 3 (As shown). The coating is tightly bonded to the tantalum substrate through the strong adhesion of the PDA, while the Sr-HA particles are embedded in the PDA network.

[0041] The present invention also provides the application of the surface-modified porous tantalum implant as described above in the preparation of medical devices for bone defect repair.

[0042] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0043] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents parts by weight, and "ratio" represents weight proportion.

[0044] Example 1 This embodiment provides a porous tantalum surface with a 5% strontium-doped hydroxyapatite / polydopamine composite coating. The strontium-doped hydroxyapatite is prepared using the following chemical formula:

[0045] Its preparation method includes the following steps: Step 1: Prepare 5% strontium-doped hydroxyapatite (SrHA1) powder Accurately weigh 5.60 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 0.27 g of strontium nitrate (Sr(NO3)2), and 1.99 g of disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O), place them in a 500 mL beaker, add 200 mL of deionized water, and stir magnetically at room temperature until completely dissolved. During stirring, slowly add 3 mol / L sodium hydroxide solution to adjust the pH of the reaction system to 10.0. Continue stirring at room temperature for 24 hours. After the reaction is complete, transfer the resulting white precipitate to a centrifuge tube, centrifuge at 4000 rpm for 10 minutes, and discard the supernatant. Wash the precipitate three times alternately with anhydrous ethanol and deionized water. Dry the washed precipitate in a 60°C oven for 48 hours, grind it to obtain 5% strontium-doped hydroxyapatite powder, denoted as SrHA1 (the molar substitution of strontium for calcium is 5%).

[0046] Step 2: Constructing a composite coating The porous tantalum scaffold (Φ10mm×5mm) was sequentially ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 minutes each, and then dried at 60°C for later use. 100 mL of a 10 mM Tris-HCl buffer solution with pH 8.0 was prepared. 0.1 g of the SrHA1 powder prepared in step 1 was weighed and added to 50 mL of the above Tris-HCl buffer solution, and ultrasonically dispersed for 10 minutes to form a homogeneous suspension. 50 mg of dopamine hydrochloride was weighed and dissolved in 50 mL of deionized water to prepare a 1 mg / mL dopamine solution. The dopamine solution was added to the above SrHA1 suspension and mixed thoroughly to form a reaction solution. The pretreated porous tantalum scaffold was completely immersed in the reaction solution, and the reaction was carried out with magnetic stirring at room temperature for 24 hours. After the reaction was completed, the porous tantalum scaffold was removed, rinsed gently three times with deionized water, and dried in a 60°C oven for 24 hours to obtain a porous tantalum implant with a 5% strontium-doped hydroxyapatite / polydopamine composite coating on the surface, denoted as SrHA1@PDA / Ta.

[0047] Example 2 This embodiment provides a method for preparing a 10% strontium-doped hydroxyapatite / polydopamine composite coating on a porous tantalum surface, comprising the following steps: Step 1: Prepare 10% strontium-doped hydroxyapatite (SrHA2) powder Accurately weigh 5.32 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 0.53 g of strontium nitrate (Sr(NO3)2), and 1.99 g of disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O), place them in a 500 mL beaker, add 200 mL of deionized water, and stir magnetically at room temperature until completely dissolved. During stirring, slowly add 3 mol / L sodium hydroxide solution to adjust the pH of the reaction system to 10.0. Continue stirring at room temperature for 24 hours. After the reaction is complete, transfer the resulting white precipitate to a centrifuge tube, centrifuge at 4000 rpm for 10 minutes, and discard the supernatant. Wash the precipitate three times alternately with anhydrous ethanol and deionized water. Dry the washed precipitate in a 60°C oven for 48 hours, grind it to obtain 10% strontium-doped hydroxyapatite powder, denoted as SrHA2 (the molar substitution of strontium for calcium is 10%).

[0048] Step 2: Constructing a composite coating The coating construction steps are the same as step 2 in Example 1, except that SrHA2 powder is used instead of SrHA1 powder. Specifically, 0.1g of SrHA2 powder is weighed and a composite coating is constructed on the porous tantalum surface using the same method to obtain a porous tantalum implant with a surface coated with a 10% strontium-doped hydroxyapatite / polydopamine composite coating, denoted as SrHA2@PDA / Ta.

[0049] Example 3 This embodiment provides a method for preparing a 15% strontium-doped hydroxyapatite / polydopamine composite coating on a porous tantalum surface, comprising the following steps: Step 1: Prepare 15% strontium-doped hydroxyapatite (SrHA3) powder Accurately weigh 5.02 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 0.80 g of strontium nitrate (Sr(NO3)2), and 1.99 g of disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O), place them in a 500 mL beaker, add 200 mL of deionized water, and stir magnetically at room temperature until completely dissolved. During stirring, slowly add 3 mol / L sodium hydroxide solution to adjust the pH of the reaction system to 10.0. Continue stirring at room temperature for 24 hours. After the reaction is complete, transfer the resulting white precipitate to a centrifuge tube, centrifuge at 4000 rpm for 10 minutes, and discard the supernatant. Wash the precipitate three times alternately with anhydrous ethanol and deionized water. Dry the washed precipitate in a 60°C oven for 48 hours, grind it to obtain 15% strontium-doped hydroxyapatite powder, denoted as SrHA3 (the molar substitution of strontium for calcium is 15%).

[0050] Step 2: Constructing a composite coating The coating construction steps are the same as step 2 in Example 1, except that SrHA3 powder is used instead of SrHA1 powder. Specifically, 0.1g of SrHA3 powder is weighed and a composite coating is constructed on the porous tantalum surface using the same method to obtain a porous tantalum implant with a surface coated with a 15% strontium-doped hydroxyapatite / polydopamine composite coating, denoted as SrHA3@PDA / Ta.

[0051] Example 4 This embodiment provides a method for preparing a 20% strontium-doped hydroxyapatite / polydopamine composite coating on a porous tantalum surface, comprising the following steps: Step 1: Prepare 20% strontium-doped hydroxyapatite (SrHA4) powder Accurately weigh 4.72 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 1.06 g of strontium nitrate (Sr(NO3)2), and 1.99 g of disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O), place them in a 500 mL beaker, add 200 mL of deionized water, and stir magnetically at room temperature until completely dissolved. During stirring, slowly add 3 mol / L sodium hydroxide solution to adjust the pH of the reaction system to 10.0. Continue stirring at room temperature for 24 hours. After the reaction is complete, transfer the resulting white precipitate to a centrifuge tube, centrifuge at 4000 rpm for 10 minutes, and discard the supernatant. Wash the precipitate three times alternately with anhydrous ethanol and deionized water. Dry the washed precipitate in a 60°C oven for 48 hours, grind it to obtain 20% strontium-doped hydroxyapatite powder, denoted as SrHA4 (the molar substitution of strontium for calcium is 20%).

[0052] Step 2: Constructing a composite coating The coating construction steps are the same as step 2 in Example 1, except that SrHA4 powder is used instead of SrHA1 powder. Specifically, 0.1g of SrHA4 powder is weighed and a composite coating is constructed on the porous tantalum surface using the same method to obtain a porous tantalum implant with a 20% strontium-doped hydroxyapatite / polydopamine composite coating on the surface, denoted as SrHA4@PDA / Ta.

[0053] Comparative Example 1 This comparative example provides a method for preparing a porous tantalum surface hydroxyapatite / polydopamine composite coating, comprising the following steps: Step 1: Preparation of hydroxyapatite (HA) powder Accurately weigh 5.91 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and 1.99 g of disodium hydrogen phosphate dodecahydrate (Na2HPO4·12H2O), place them in a 500 mL beaker, add 200 mL of deionized water, and stir magnetically at room temperature until completely dissolved. During stirring, slowly add 3 mol / L sodium hydroxide solution to adjust the pH of the reaction system to 10.0. Continue stirring at room temperature for 24 hours. After the reaction is complete, transfer the resulting white precipitate to a centrifuge tube, centrifuge at 4000 rpm for 10 minutes, and discard the supernatant. Wash the precipitate three times alternately with anhydrous ethanol and deionized water. Dry the washed precipitate in a 60°C oven for 48 hours, grind it to obtain hydroxyapatite powder, denoted as HA.

[0054] Step 2: Constructing a composite coating The porous tantalum scaffold (Φ10mm×5mm) was sequentially ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 minutes each, and then dried at 60°C for later use. Prepare 100 mL of a 10 mM Tris-HCl buffer solution with a pH of 8.0. Weigh 0.1 g of the HA powder prepared in step 1 and add it to 50 mL of the above Tris-HCl buffer solution, then ultrasonically disperse for 10 minutes to form a homogeneous suspension. Weigh 50 mg of dopamine hydrochloride and dissolve it in 50 mL of deionized water to prepare a 1 mg / mL dopamine solution. Add the dopamine solution to the above HA suspension and mix well to form a reaction solution. Completely immerse the pretreated porous tantalum scaffold in the reaction solution and react magnetically at room temperature for 24 hours. After the reaction was completed, the porous tantalum scaffold was removed, rinsed gently three times with deionized water, and dried in a 60°C oven for 24 hours to obtain a porous tantalum implant with a hydroxyapatite / polydopamine composite coating on the surface, denoted as HA@PDA / Ta.

[0055] Figure 4 FTIR data showed that strontium doping did not alter the phosphate and hydroxyl vibrational peak positions in hydroxyapatite; only at high doping concentrations did the peaks broaden slightly, confirming that Sr... 2+ The substitution of calcium ions by isomorphic substitution did not alter the lattice chemical bonding state. After polydopamine coating, the characteristic peaks of the substrate remained intact, while characteristic peaks of organic functional groups such as CO and NH appeared, indicating that PDA successfully modified the surface of the nanorods through physical attachment without destroying the HA lattice structure.

[0056] Figure 5 Sr was displayed 2+Doping significantly enhances the photothermal conversion capability of the material. The SrHA4@PDA sample with the highest doping concentration reached a temperature of 62.7°C, far exceeding that of the undoped sample and the control group. The study confirmed that the conjugated system of PDA and the lattice defects induced by Sr doping work together to enhance light absorption and heat conduction. Calculations showed that the photothermal conversion efficiency of SrHA@PDA reached 63.79%, establishing its excellent clinical application potential in the field of photothermal therapy.

[0057] Figure 6 The results show that after irradiation with an 808 nm laser, the efficient photothermal conversion of SrHA@PDA (efficiency 63.79%) raises the local temperature to 62.7°C, causing bacterial morphological damage and cytoplasmic outflow, exhibiting a significant photothermal antibacterial effect against Escherichia coli.

[0058] Figure 7 The MTT assay showed that the SrHA@PDA material was non-cytotoxic, and Sr... 2+ The doping significantly promoted the proliferation of MC3T3-E1 cells after long-term culture, and combined with its photothermal antibacterial properties, it was confirmed that the material has good biosafety at therapeutic doses.

[0059] Figure 8 SEM results showed that the surface cells of SrHA@PDA were well extended and the coating was stably bonded; it could induce the formation of a honeycomb hydroxyapatite layer in simulated body fluid, confirming that it has excellent biocompatibility, interfacial stability and bone mineralization ability.

[0060] Figure 9 The display shows that SrHA@PDA's Sr 2+ The release exhibits a two-stage characteristic: rapid release of surface ions in the early stage, followed by slow diffusion influenced by the crystal lattice and PDA layer in the later stage. The highly doped sample showed a higher release rate (51.754 ppm after 21 days), with a concentration far below the safety threshold. This sustained release, synergistic with photothermal effects, exerts an antibacterial effect while simultaneously promoting osteoblast proliferation, confirming that the material possesses both long-term safety and biofunctionality.

[0061] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface, characterized in that, Includes the following steps: Step 1: Dissolve calcium, strontium, and phosphorus sources in water in a predetermined ratio, and carry out a precipitation reaction under alkaline conditions. After separation, washing, and drying, strontium-doped hydroxyapatite powder is obtained. Step 2: Disperse the strontium-doped hydroxyapatite powder obtained in Step 1 in a weakly alkaline buffer solution, add dopamine or its salt, and mix well to form a reaction solution; immerse porous tantalum in the reaction solution to allow dopamine to polymerize; after the reaction is complete, remove the porous tantalum, wash and dry it to form a composite coating of strontium-doped hydroxyapatite and polydopamine on the surface of the porous tantalum.

2. The method for preparing a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface according to claim 1, characterized in that, The calcium source is calcium nitrate, calcium chloride, or calcium acetate; the phosphorus source is disodium hydrogen phosphate, diammonium hydrogen phosphate, or diammonium dihydrogen phosphate; and the strontium source is strontium nitrate or strontium chloride.

3. The method for preparing a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface according to claim 1, characterized in that, In step 1, the alkaline condition is achieved by adjusting the pH of the reaction system to 9.0-11.0 by adding sodium hydroxide solution and / or hydrochloric acid solution.

4. The method for preparing a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface according to claim 1, characterized in that, In step 1, the predetermined ratio results in a molar substitution of strontium ions for calcium ions of 0.5% to 20%.

5. The method for preparing a porous tantalum surface strontium-doped hydroxyapatite and polydopamine composite coating according to claim 1, characterized in that, In step 2, the weakly alkaline buffer solution is a tris(hydroxymethyl)aminomethane-hydrochloric acid buffer solution with a pH value of 7.5 to 8.

5.

6. The method for preparing a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface according to claim 1, characterized in that, In step 2, the dopamine or its salt is dopamine hydrochloride, and its final concentration in the reaction solution is 0.2~5 mg / mL.

7. The method for preparing a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface according to claim 1, characterized in that, In step 2, the dispersion concentration of the strontium-doped hydroxyapatite powder in the weakly alkaline buffer solution is 0.1~10 mg / mL.

8. The method for preparing a strontium-doped hydroxyapatite and polydopamine composite coating on a porous tantalum surface according to claim 1, characterized in that, In step 2, the polymerization reaction of dopamine is carried out at room temperature for 20-30 hours.

9. A surface-modified porous tantalum implant, characterized in that, Its surface has a strontium-doped hydroxyapatite and polydopamine composite coating formed by the preparation method described in any one of claims 1 to 8.

10. The use of a surface-modified porous tantalum implant as described in claim 9 in the preparation of a medical device for bone defect repair.

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