Controllably degradable high-corrosion-resistant medical magnesium-aluminum alloy vascular stent and preparation method thereof

Abstract

The application discloses a controllable degradation high-corrosion-resistance medical magnesium-aluminum alloy blood vessel stent and a preparation method thereof. The method comprises the following steps: subjecting magnesium alloy ingots containing Al, Zn, Ca and Mn to homogenization treatment, hot extrusion, cold drawing and recrystallization annealing to obtain low-aluminum magnesium-aluminum alloy microtubular materials containing aluminum second-phase non-continuous discrete distribution; after laser cutting, deburring, electrochemical polishing and surface activation, an inner layer rich in MgF2 and an outer layer rich in calcium and phosphorus are sequentially constructed; a polydopamine interface anchoring layer is formed, and a degradable polymer sealing liquid containing a heparinized hyaluronic acid-REDV peptide composite active component is coated to form an active flexible sealing layer after solidification. The stent obtained by the application has good corrosion resistance, controllable degradation, mechanical support retention capacity and endothelial repair promotion performance.

Description

Technical Field

[0001] This invention relates to the field of vascular stent technology, and in particular to a controllable degradation, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent and its preparation method. Background Technology

[0002] Vascular stents are crucial interventional medical devices for treating diseases such as vascular stenosis and occlusion. Traditional metallic vascular stents are mostly made of non-degradable materials such as stainless steel, cobalt-chromium alloys, and nickel-titanium alloys. Although they possess high radial support strength and good processing and forming properties, they remain in the blood vessel for a long period after implantation, potentially causing chronic inflammation, decreased vascular compliance, late-stage thrombosis, and difficulties in re-intervention. Magnesium and magnesium alloys, with their characteristics of gradual degradation in vivo, relatively low elastic modulus, and good biocompatibility, are considered important candidate materials for biodegradable vascular stents. Magnesium-based vascular stents can provide necessary mechanical support in the early stages of implantation and gradually degrade and are absorbed after vascular repair, which helps reduce the long-term risks associated with permanent metallic implants.

[0003] However, existing magnesium-based vascular stents still suffer from problems such as excessively rapid degradation, insufficient corrosion resistance, and poor service stability. Magnesium alloys are highly reactive in the physiological environment containing chloride ions, making them prone to rapid corrosion. This leads to a significant decrease in the radial support capacity of the stent before vascular repair is complete. Simultaneously, the presence of coarse, continuous, or segregated aluminum-containing second phases in magnesium-aluminum alloys can easily form localized galvanic corrosion with the magnesium matrix, inducing pitting corrosion and non-uniform degradation. Existing single inorganic conversion layers or polymer coatings are prone to microcracks or peeling during stent clamping, delivery, and balloon dilation, affecting protective efficacy. Furthermore, corrosion resistance and endothelial repair promotion functions are often difficult to coordinate, and the matching between the stent degradation process and the vascular endothelial repair process is insufficient, requiring further improvement. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent and its preparation method. Using a low-aluminum magnesium-aluminum alloy as the stent matrix, homogenization treatment, hot extrusion, cold drawing, and recrystallization annealing are employed to refine the alloy grains uniformly and to create a discontinuous, discrete distribution of the aluminum-containing second phase, reducing the tendency for localized galvanic corrosion from the source. Subsequently, a MgF2-enriched inner layer and a calcium-phosphorus-enriched outer layer are sequentially constructed on the stent surface to form a dual-gradient corrosion-resistant conversion layer, blocking corrosive media and improving interfacial bonding. Furthermore, an interfacial anchoring layer containing catechol groups and an active flexible sealing layer containing heparinized hyaluronic acid-REDV peptide composite active components are introduced, enabling the stent to possess corrosion-resistant protection, controllable degradation, and endothelial repair-promoting functions.

[0005] This invention can be achieved through the following technical solutions: A method for preparing a controllable degradation, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent includes the following steps: S1. Magnesium alloy ingots containing Al, Zn, Ca and Mn are subjected to homogenization treatment, hot extrusion, cold drawing and recrystallization annealing treatment in sequence to obtain low-aluminum magnesium-aluminum alloy micro tubes with uniform grains and discontinuous discrete distribution of aluminum-containing second phase. S2. Laser cutting is performed on the low-aluminum-magnesium-aluminum alloy microtubes obtained in step S1 to form a vascular stent blank. The vascular stent blank is then subjected to deburring, electrochemical polishing, and surface activation treatment containing carboxyl or phosphate groups to obtain an activated stent. S3. The activated scaffold obtained in step S2 is subjected to fluorine-containing conversion treatment and calcium-phosphorus-containing conversion treatment in sequence to form a dual-gradient corrosion-resistant conversion layer on the surface of the scaffold. The dual-gradient corrosion-resistant conversion layer includes a MgF2-enriched inner layer close to the low-aluminum-magnesium-aluminum alloy substrate and a calcium-phosphorus-enriched outer layer located outside the MgF2-enriched inner layer. S4. An interface anchoring layer containing catechol groups is formed on the surface of the dual-gradient corrosion-resistant conversion layer obtained in step S3. Then, a biodegradable polymer sealing liquid containing heparinized hyaluronic acid-REDV peptide composite active components is coated. After drying and low-temperature curing, an active flexible sealing layer is formed on the outside of the dual-gradient corrosion-resistant conversion layer, thus obtaining a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent.

[0006] Preferably, the low-aluminum magnesium-aluminum alloy in S1 comprises, by mass percentage: Al 0.3%–1.2%, Zn 0.3%–1.5%, Ca 0.05%–0.5%, Mn 0.05%–0.3%, with the balance being Mg and unavoidable impurities; wherein, the unavoidable impurities contain no more than 0.005% Fe, no more than 0.001% Ni, and no more than 0.002% Cu.

[0007] Preferably, the homogenization treatment in S1 is carried out at a temperature of 360℃~420℃ for 6 h~12 h; the hot extrusion temperature is 250℃~350℃ and the extrusion ratio is 10~40; the cold drawing is carried out in 3~8 passes with a cumulative deformation of 20%~60%; and the recrystallization annealing temperature is 180℃~260℃ and the time is 5 min~30 min.

[0008] Preferably, the average grain size of the low-aluminum-magnesium-aluminum alloy microtube in S1 is 2 μm to 15 μm, the average size of the aluminum-containing second phase is 0.1 μm to 3 μm, and the aluminum-containing second phase does not form a continuous network grain boundary phase.

[0009] Preferably, the surface activation treatment containing carboxyl or phosphate groups in S2 is carried out using an aqueous solution containing one or more of citric acid, phytic acid, polyacrylic acid, and phosphate, and the surface roughness Ra of the scaffold after treatment is 0.05 μm to 0.30 μm.

[0010] Preferably, the fluorine-containing conversion treatment in S3 is carried out using a fluorine-containing conversion solution, wherein the fluoride ion concentration in the fluorine-containing conversion solution is 0.05 mol / L to 0.5 mol / L, the pH is 4.0 to 6.5, the treatment temperature is 20℃ to 50℃, and the treatment time is 5 min to 30 min; the calcium-phosphorus conversion treatment is carried out using a calcium-phosphorus conversion solution, wherein the calcium ion concentration is 0.01 mol / L to 0.20 mol / L, the phosphate ion concentration is 0.005 mol / L to 0.12 mol / L, the Ca / P molar ratio is 1.2 to 1.8, the pH is 5.0 to 7.0, the treatment temperature is 25℃ to 60℃, and the treatment time is 5 min to 60 min.

[0011] Preferably, the thickness of the MgF2 enriched inner layer in S3 is 0.2 μm to 3 μm, the thickness of the calcium-phosphorus enriched outer layer is 0.3 μm to 5 μm, and the total thickness of the dual-gradient corrosion-resistant conversion layer is 0.5 μm to 8 μm.

[0012] Preferably, the interface anchoring layer containing catechol groups in S4 is a polydopamine layer; the polydopamine layer is formed by reacting the scaffold obtained in step S3 in a weakly alkaline buffer solution containing dopamine hydrochloride, wherein the concentration of dopamine hydrochloride is 0.5 g / L to 2.0 g / L, the pH of the weakly alkaline buffer solution is 8.0 to 8.8, and the reaction time is 10 min to 60 min.

[0013] Preferably, the biodegradable polymer sealing solution in S4 comprises, by mass, 100 parts of biodegradable polymer, 0.5-8 parts of heparinized hyaluronic acid-REDV peptide composite active component, and 1000-5000 parts of organic solvent; the biodegradable polymer is a blend of polylactic acid-glycolic acid copolymer and polytrimethylene carbonate, wherein the mass ratio of polylactic acid-glycolic acid copolymer to polytrimethylene carbonate is 1:(0.2-1.5), and the heparinized hyaluronic acid-REDV peptide composite active component is REDV peptide grafted with heparinized hyaluronic acid.

[0014] Preferably, the thickness of the active flexible sealing layer is 1 μm to 15 μm; the drying temperature is 25℃ to 45℃; the low-temperature curing temperature is 45℃ to 70℃; and the low-temperature curing time is 0.5 h to 4 h.

[0015] The beneficial effects of this invention are: This invention uses a low-aluminum magnesium-aluminum alloy as the vascular stent matrix. Through homogenization treatment, hot extrusion, cold drawing, and recrystallization annealing, the alloy microstructure is synergistically controlled to achieve a more uniform grain distribution and a discontinuous, discrete distribution of the aluminum-containing second phase. This reduces localized galvanic corrosion caused by coarse or continuous second phases, improving the stent's uniform degradation capability and early mechanical support stability at the matrix level. A dual-gradient corrosion-resistant conversion layer is formed by sequentially constructing a MgF2-enriched inner layer and a calcium-phosphorus-enriched outer layer. The MgF2-enriched inner layer can block corrosive media such as chloride ions and water molecules from penetrating the magnesium alloy. The diffusion of the aluminum alloy matrix and the enrichment of calcium and phosphorus in the outer layer improve interfacial bonding and biocompatibility, thereby enhancing the corrosion resistance of the stent in simulated physiological environments. By incorporating a polydopamine interfacial anchoring layer, the bonding force between the inorganic corrosion-resistant layer and the organic flexible sealing layer is strengthened, reducing the risk of coating cracking, peeling, or detachment during stent gripping and balloon expansion. Furthermore, the introduction of heparinized hyaluronic acid-REDV peptide composite active components into the active flexible sealing layer enables the stent to simultaneously provide sealing and corrosion protection, slow-release of active components, and promotion of endothelial cell adhesion and repair during degradation. Therefore, the vascular stent obtained by this invention can simultaneously provide corrosion resistance, controllable degradation, mechanical support, and endothelial repair promotion, making it suitable for the field of biodegradable medical vascular stents. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 Corrosion current density, 28-day mass loss rate, and coating crack density of vascular stents after expansion; Figure 2 The 28-day radial support retention rate and endothelial cell adhesion rate of vascular stents are considered. Detailed Implementation

[0017] The following provides a detailed description of the embodiments of the present invention: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and processes. However, the scope of protection of the present invention is not limited to the following embodiments. Experimental methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions.

[0018] Example 1: A method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent, comprising the following steps: S1. Based on mass percentage, a low-aluminum-magnesium-aluminum alloy ingot is selected, comprising Al 0.3%, Zn 0.3%, Ca 0.05%, Mn 0.05%, with the balance being Mg and unavoidable impurities; wherein the Fe content is not higher than 0.005%, the Ni content is not higher than 0.001%, and the Cu content is not higher than 0.002%; the above-mentioned low-aluminum-magnesium-aluminum alloy ingot is homogenized at 360℃ for 12 h, and then hot-extruded at 250℃ with an extrusion ratio of 10; subsequently, it is cold-drawn in 3 passes with a cumulative deformation of 20%; and then recrystallized and annealed at 180℃ for 30 min to obtain low-aluminum-magnesium-aluminum alloy microtubes; the average grain size of the obtained low-aluminum-magnesium-aluminum alloy microtubes is approximately 2 μm, and the average size of the aluminum-containing second phase is approximately 0.1 μm, and the aluminum-containing second phase does not form a continuous network grain boundary phase; S2. The low-aluminum-magnesium-aluminum alloy microtubes obtained in step S1 are laser-cut to form a vascular stent blank; the vascular stent blank is then subjected to deburring and electrochemical polishing treatments, and then surface activation treatment with carboxyl groups is performed using an aqueous solution containing citric acid to obtain an activated stent; the surface roughness Ra of the stent after treatment is 0.05 μm. S3. The activated scaffold obtained in step S2 is first placed in a fluorine-containing conversion solution for fluorine conversion treatment. The fluorine-containing conversion solution has a fluoride ion concentration of 0.05 mol / L, a pH of 4.0, a treatment temperature of 20℃, and a treatment time of 30 min. Then, it is placed in a calcium-phosphorus-containing conversion solution for calcium-phosphorus conversion treatment. The calcium-phosphorus-containing conversion solution has a calcium ion concentration of 0.01 mol / L, a phosphate ion concentration of 0.0083 mol / L, a Ca / P molar ratio of 1.2, a pH of 5.0, a treatment temperature of 25℃, and a treatment time of 60 min, forming a dual-gradient corrosion-resistant conversion layer on the scaffold surface. The dual-gradient corrosion-resistant conversion layer includes a MgF2-enriched inner layer close to the low-aluminum-magnesium-aluminum alloy substrate and a calcium-phosphorus-enriched outer layer located outside the MgF2-enriched inner layer. The thickness of the MgF2-enriched inner layer is 0.2 μm, the thickness of the calcium-phosphorus-enriched outer layer is 0.3 μm, and the total thickness of the dual-gradient corrosion-resistant conversion layer is 0.5 μm. S4. The scaffold obtained in step S3 is placed in a weakly alkaline buffer solution containing dopamine hydrochloride to react and form a polydopamine interfacial anchoring layer; wherein the concentration of dopamine hydrochloride is 0.5 g / L, the pH of the weakly alkaline buffer solution is 8.0, and the reaction time is 10 minutes. min; then prepare a biodegradable polymer sealing solution; by mass, the biodegradable polymer sealing solution includes 100 parts of biodegradable polymer, 0.5 parts of heparinized hyaluronic acid-REDV peptide composite active component, and 1000 parts of organic solvent; the biodegradable polymer is a blend of polylactic acid-glycolic acid copolymer and polytrimethylene carbonate, with a mass ratio of polylactic acid-glycolic acid copolymer to polytrimethylene carbonate of 1:0.2; the heparinized hyaluronic acid-REDV peptide composite active component is REDV peptide grafted with heparinized hyaluronic acid, and dispersed in the biodegradable polymer sealing solution in the form of lyophilized microparticles; the organic solvent is a mixed solvent of hexafluoroisopropanol and ethanol; the biodegradable polymer sealing solution is coated on the surface of the polydopamine interface anchoring layer, dried at 25°C, and then cured at 45°C for 4 h to form an active flexible sealing layer with a thickness of 1 μm, thus obtaining a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent.

[0019] Example 2: A method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent, comprising the following steps: S1. Based on mass percentage, a low-aluminum-magnesium-aluminum alloy ingot was selected, comprising Al 0.75%, Zn 0.9%, Ca 0.275%, Mn 0.175%, with the balance being Mg and unavoidable impurities; wherein the Fe content is not higher than 0.005%, the Ni content is not higher than 0.001%, and the Cu content is not higher than 0.002%; the above-mentioned low-aluminum-magnesium-aluminum alloy ingot was homogenized at 390℃ for 9 h, and then hot-extruded at 300℃ with an extrusion ratio of 25; subsequently, it was cold-drawn in 5 passes with a cumulative deformation of 40%; and then recrystallized and annealed at 220℃ for 18 min to obtain low-aluminum-magnesium-aluminum alloy microtubes; the average grain size of the obtained low-aluminum-magnesium-aluminum alloy microtubes was approximately 8 μm, and the average size of the aluminum-containing second phase was approximately 1.5 μm, and the aluminum-containing second phase did not form a continuous network grain boundary phase; S2. The low-aluminum-magnesium-aluminum alloy microtubes obtained in step S1 are laser-cut to form a vascular stent blank; the vascular stent blank is then subjected to deburring and electrochemical polishing treatments, and then surface activation treatment containing carboxyl and phosphate groups is performed using an aqueous solution containing phytic acid and polyacrylic acid to obtain an activated stent; the surface roughness Ra of the stent after treatment is 0.18 μm. S3. The activated scaffold obtained in step S2 is first placed in a fluorine-containing conversion solution for fluorine conversion treatment. The fluorine-containing conversion solution has a fluoride ion concentration of 0.28 mol / L, a pH of 5.2, a treatment temperature of 35℃, and a treatment time of 18 min. Subsequently, it is placed in a calcium-phosphorus-containing conversion solution for calcium-phosphorus conversion treatment. The calcium-phosphorus-containing conversion solution has a calcium ion concentration of 0.105 mol / L, a phosphate ion concentration of 0.070 mol / L, a Ca / P molar ratio of 1.5, a pH of 6.0, a treatment temperature of 42℃, and a treatment time of 32 min, forming a dual-gradient corrosion-resistant conversion layer on the scaffold surface. The dual-gradient corrosion-resistant conversion layer includes a MgF2-enriched inner layer close to the low-aluminum-magnesium-aluminum alloy substrate and a calcium-phosphorus-enriched outer layer located outside the MgF2-enriched inner layer. The thickness of the MgF2-enriched inner layer is 1.6 μm, the thickness of the calcium-phosphorus-enriched outer layer is 2.65 μm, and the total thickness of the dual-gradient corrosion-resistant conversion layer is 4.25 μm. S4. The scaffold obtained in step S3 is placed in a weakly alkaline buffer solution containing dopamine hydrochloride to react and form a polydopamine interfacial anchoring layer; wherein the concentration of dopamine hydrochloride is 1.25 g / L, the pH of the weakly alkaline buffer solution is 8.4, and the reaction time is 35 minutes. min; then prepare a biodegradable polymer sealing solution; by mass, the biodegradable polymer sealing solution includes 100 parts of biodegradable polymer, 4.25 parts of heparinized hyaluronic acid-REDV peptide composite active component and 3000 parts of organic solvent; the biodegradable polymer is a blend of polylactic acid-glycolic acid copolymer and polytrimethylene carbonate, with a mass ratio of polylactic acid-glycolic acid copolymer to polytrimethylene carbonate of 1:0.85; the heparinized hyaluronic acid-REDV peptide composite active component is REDV peptide grafted with heparinized hyaluronic acid, and dispersed in the biodegradable polymer sealing solution in the form of lyophilized microparticles; the organic solvent is a mixed solvent of hexafluoroisopropanol and ethanol; the biodegradable polymer sealing solution is coated on the surface of the polydopamine interface anchoring layer, dried at 35°C, and then cured at 58°C for 2.25 h to form an active flexible sealing layer with a thickness of 8 μm, thus obtaining a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent.

[0020] Example 3: A method for preparing a controllable degradation, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent, comprising the following steps: S1. Based on mass percentage, a low-aluminum-magnesium-aluminum alloy ingot is selected, comprising Al 1.2%, Zn 1.5%, Ca 0.5%, Mn 0.3%, with the balance being Mg and unavoidable impurities; wherein the Fe content is not higher than 0.005%, the Ni content is not higher than 0.001%, and the Cu content is not higher than 0.002%; the above low-aluminum-magnesium-aluminum alloy ingot is homogenized at 420℃ for 6 h, and then hot-extruded at 350℃ with an extrusion ratio of 40; subsequently, it is cold-drawn in 8 passes with a cumulative deformation of 60%; and then recrystallized and annealed at 260℃ for 5 min to obtain low-aluminum-magnesium-aluminum alloy microtubes; the average grain size of the obtained low-aluminum-magnesium-aluminum alloy microtubes is approximately 15 μm, and the average size of the aluminum-containing second phase is approximately 3 μm, and the aluminum-containing second phase does not form a continuous network grain boundary phase; S2. The low-aluminum-magnesium-aluminum alloy microtubes obtained in step S1 are laser-cut to form a vascular stent blank; the vascular stent blank is then subjected to deburring and electrochemical polishing treatments, and then surface activation treatment with phosphate groups is performed using an aqueous solution containing phytic acid and phosphate to obtain an activated stent; the surface roughness Ra of the stent after treatment is 0.30 μm. S3. The activated scaffold obtained in step S2 is first placed in a fluorine-containing conversion solution for fluorine conversion treatment. The fluorine-containing conversion solution has a fluoride ion concentration of 0.5 mol / L, a pH of 6.5, a treatment temperature of 50℃, and a treatment time of 5 min. Then, it is placed in a calcium-phosphorus-containing conversion solution for calcium-phosphorus conversion treatment. The calcium-phosphorus-containing conversion solution has a calcium ion concentration of 0.20 mol / L, a phosphate ion concentration of 0.111 mol / L, a Ca / P molar ratio of 1.8, a pH of 7.0, a treatment temperature of 60℃, and a treatment time of 5 min, forming a dual-gradient corrosion-resistant conversion layer on the scaffold surface. The dual-gradient corrosion-resistant conversion layer includes a MgF2-enriched inner layer close to the low-aluminum-magnesium-aluminum alloy substrate and a calcium-phosphorus-enriched outer layer located outside the MgF2-enriched inner layer. The thickness of the MgF2-enriched inner layer is 3 μm, the thickness of the calcium-phosphorus-enriched outer layer is 5 μm, and the total thickness of the dual-gradient corrosion-resistant conversion layer is 8 μm. S4. The scaffold obtained in step S3 is placed in a weakly alkaline buffer solution containing dopamine hydrochloride to react and form a polydopamine interfacial anchoring layer; wherein the concentration of dopamine hydrochloride is 2.0 g / L, the pH of the weakly alkaline buffer solution is 8.8, and the reaction time is 60 minutes. min; then prepare a biodegradable polymer sealing solution; by mass, the biodegradable polymer sealing solution includes 100 parts of biodegradable polymer, 8 parts of heparinized hyaluronic acid-REDV peptide composite active component and 5000 parts of organic solvent; the biodegradable polymer is a blend of polylactic acid-glycolic acid copolymer and polytrimethylene carbonate, with a mass ratio of polylactic acid-glycolic acid copolymer to polytrimethylene carbonate of 1:1.5; the heparinized hyaluronic acid-REDV peptide composite active component is REDV peptide grafted with heparinized hyaluronic acid, and dispersed in the biodegradable polymer sealing solution in the form of lyophilized microparticles; the organic solvent is a mixed solvent of hexafluoroisopropanol and ethanol; the biodegradable polymer sealing solution is coated on the surface of the polydopamine interface anchoring layer, dried at 45°C, and then cured at 70°C for 0.5 h to form an active flexible sealing layer with a thickness of 15 μm, thus obtaining a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent.

[0021] Comparative Example 1: The difference between this comparative example and Example 1 is that in S1, homogenization treatment, cold drawing and recrystallization annealing are not performed. Instead, the low-aluminum magnesium-aluminum alloy ingot of the same composition is prepared into magnesium-aluminum alloy micro tubes by conventional hot extrusion.

[0022] The method for preparing the vascular stent in this comparative example is as follows: S1. Based on mass percentage, a low-aluminum magnesium-aluminum alloy ingot is selected, comprising Al 0.3%, Zn 0.3%, Ca 0.05%, Mn 0.05%, with the balance being Mg and unavoidable impurities; wherein the Fe content is not higher than 0.005%, the Ni content is not higher than 0.001%, and the Cu content is not higher than 0.002%; the above low-aluminum magnesium-aluminum alloy ingot is subjected to conventional hot extrusion at 250℃ with an extrusion ratio of 10 to obtain magnesium-aluminum alloy microtubes; homogenization treatment, cold drawing, and recrystallization annealing are not performed in this step; metallographic microscopy and scanning electron microscopy examination show that the grain size distribution in the obtained magnesium-aluminum alloy microtubes is uneven, and the aluminum-containing second phase exhibits local segregation or continuous distribution; S2. The magnesium-aluminum alloy microtubes obtained in step S1 are laser-cut to form a vascular stent blank; the vascular stent blank is then subjected to deburring and electrochemical polishing treatments, and then surface activation treatment with carboxyl groups is performed using an aqueous solution containing citric acid to obtain an activated stent; the surface roughness Ra of the stent after treatment is 0.05 μm. S3. The activated scaffold obtained in step S2 is first placed in a fluorine-containing conversion solution for fluorine conversion treatment. The fluorine-containing conversion solution has a fluoride ion concentration of 0.05 mol / L, a pH of 4.0, a treatment temperature of 20℃, and a treatment time of 30 min. Subsequently, it is placed in a calcium-phosphorus-containing conversion solution for calcium-phosphorus conversion treatment. The calcium-phosphorus-containing conversion solution has a calcium ion concentration of 0.01 mol / L, a phosphate ion concentration of 0.0083 mol / L, a Ca / P molar ratio of 1.2, a pH of 5.0, a treatment temperature of 25℃, and a treatment time of 60 min, forming a dual-gradient corrosion-resistant conversion layer on the scaffold surface. The dual-gradient corrosion-resistant conversion layer includes a MgF2-enriched inner layer near the magnesium-aluminum alloy substrate and a calcium-phosphorus-enriched outer layer located outside the MgF2-enriched inner layer. The thickness of the MgF2-enriched inner layer is 0.2 μm, the thickness of the calcium-phosphorus-enriched outer layer is 0.3 μm, and the total thickness of the dual-gradient corrosion-resistant conversion layer is 0.5 μm. S4. The scaffold obtained in step S3 is placed in a weakly alkaline buffer solution containing dopamine hydrochloride to react and form a polydopamine interfacial anchoring layer; wherein the concentration of dopamine hydrochloride is 0.5 g / L, the pH of the weakly alkaline buffer solution is 8.0, and the reaction time is 10 minutes. min; then prepare a biodegradable polymer sealing solution; by mass, the biodegradable polymer sealing solution includes 100 parts of biodegradable polymer, 0.5 parts of heparinized hyaluronic acid-REDV peptide composite active component, and 1000 parts of organic solvent; the biodegradable polymer is a blend of polylactic acid-glycolic acid copolymer and polytrimethylene carbonate, with a mass ratio of polylactic acid-glycolic acid copolymer to polytrimethylene carbonate of 1:0.2; the heparinized hyaluronic acid-REDV peptide composite active component is REDV peptide grafted with heparinized hyaluronic acid, and dispersed in the biodegradable polymer sealing solution in the form of lyophilized microparticles; the organic solvent is a mixed solvent of hexafluoroisopropanol and ethanol; the biodegradable polymer sealing solution is coated on the surface of the polydopamine interface anchoring layer, dried at 25°C, and then cured at 45°C for 4 h to form an active flexible sealing layer with a thickness of 1 μm, thus obtaining a medical magnesium-aluminum alloy vascular stent.

[0023] Comparative Example 2: The difference between this comparative example and Example 1 is that only the fluorine-containing conversion treatment is performed in S3, and the calcium-phosphorus-containing conversion treatment is not performed.

[0024] The method for preparing the vascular stent in this comparative example is as follows: S1. Based on mass percentage, a low-aluminum-magnesium-aluminum alloy ingot is selected, comprising Al 0.3%, Zn 0.3%, Ca 0.05%, Mn 0.05%, with the balance being Mg and unavoidable impurities; wherein the Fe content is not higher than 0.005%, the Ni content is not higher than 0.001%, and the Cu content is not higher than 0.002%; the above-mentioned low-aluminum-magnesium-aluminum alloy ingot is homogenized at 360℃ for 12 h, and then hot-extruded at 250℃ with an extrusion ratio of 10; subsequently, it is cold-drawn in 3 passes with a cumulative deformation of 20%; and then recrystallized and annealed at 180℃ for 30 min to obtain low-aluminum-magnesium-aluminum alloy microtubes; the average grain size of the obtained low-aluminum-magnesium-aluminum alloy microtubes is approximately 2 μm, and the average size of the aluminum-containing second phase is approximately 0.1 μm, and the aluminum-containing second phase does not form a continuous network grain boundary phase; S2. The low-aluminum-magnesium-aluminum alloy microtubes obtained in step S1 are laser-cut to form a vascular stent blank; the vascular stent blank is then subjected to deburring and electrochemical polishing treatments, and then surface activation treatment with carboxyl groups is performed using an aqueous solution containing citric acid to obtain an activated stent; the surface roughness Ra of the stent after treatment is 0.05 μm. S3. The activated scaffold obtained in step S2 is placed in a fluorine-containing conversion solution for fluorine conversion treatment. The fluorine-containing conversion solution has a fluoride ion concentration of 0.05 mol / L, a pH of 4.0, a treatment temperature of 20℃, and a treatment time of 30 min, forming a MgF2 enriched layer on the scaffold surface. No calcium-phosphorus conversion treatment is performed in this step, so no calcium-phosphorus enriched outer layer is formed. The thickness of the MgF2 enriched layer is 0.2 μm. S4. The scaffold obtained in step S3 is placed in a weakly alkaline buffer solution containing dopamine hydrochloride to react and form a polydopamine interfacial anchoring layer; wherein the concentration of dopamine hydrochloride is 0.5 g / L, the pH of the weakly alkaline buffer solution is 8.0, and the reaction time is 10 minutes. min; then prepare a biodegradable polymer sealing solution; by mass, the biodegradable polymer sealing solution includes 100 parts of biodegradable polymer, 0.5 parts of heparinized hyaluronic acid-REDV peptide composite active component, and 1000 parts of organic solvent; the biodegradable polymer is a blend of polylactic acid-glycolic acid copolymer and polytrimethylene carbonate, with a mass ratio of polylactic acid-glycolic acid copolymer to polytrimethylene carbonate of 1:0.2; the heparinized hyaluronic acid-REDV peptide composite active component is REDV peptide grafted with heparinized hyaluronic acid, and dispersed in the biodegradable polymer sealing solution in the form of lyophilized microparticles; the organic solvent is a mixed solvent of hexafluoroisopropanol and ethanol; the biodegradable polymer sealing solution is coated on the surface of the polydopamine interface anchoring layer, dried at 25°C, and then cured at 45°C for 4 h to form an active flexible sealing layer with a thickness of 1 μm, thus obtaining a medical magnesium-aluminum alloy vascular stent.

[0025] Comparative Example 3: The difference between this comparative example and Example 1 is that in S4, a polydopamine interface anchoring layer is not constructed. Instead, a biodegradable polymer sealing liquid containing heparinized hyaluronic acid-REDV peptide composite active components is directly coated on the surface of the dual-gradient corrosion-resistant conversion layer.

[0026] The method for preparing the vascular stent in this comparative example is as follows: S1. Based on mass percentage, a low-aluminum-magnesium-aluminum alloy ingot is selected, comprising Al 0.3%, Zn 0.3%, Ca 0.05%, Mn 0.05%, with the balance being Mg and unavoidable impurities; wherein the Fe content is not higher than 0.005%, the Ni content is not higher than 0.001%, and the Cu content is not higher than 0.002%; the above-mentioned low-aluminum-magnesium-aluminum alloy ingot is homogenized at 360℃ for 12 h, and then hot-extruded at 250℃ with an extrusion ratio of 10; subsequently, it is cold-drawn in 3 passes with a cumulative deformation of 20%; and then recrystallized and annealed at 180℃ for 30 min to obtain low-aluminum-magnesium-aluminum alloy microtubes; the average grain size of the obtained low-aluminum-magnesium-aluminum alloy microtubes is approximately 2 μm, and the average size of the aluminum-containing second phase is approximately 0.1 μm, and the aluminum-containing second phase does not form a continuous network grain boundary phase; S2. The low-aluminum-magnesium-aluminum alloy microtubes obtained in step S1 are laser-cut to form a vascular stent blank; the vascular stent blank is then subjected to deburring and electrochemical polishing treatments, and then surface activation treatment with carboxyl groups is performed using an aqueous solution containing citric acid to obtain an activated stent; the surface roughness Ra of the stent after treatment is 0.05 μm. S3. The activated scaffold obtained in step S2 is first placed in a fluorine-containing conversion solution for fluorine conversion treatment. The fluorine-containing conversion solution has a fluoride ion concentration of 0.05 mol / L, a pH of 4.0, a treatment temperature of 20℃, and a treatment time of 5 min. Then, it is placed in a calcium-phosphorus-containing conversion solution for calcium-phosphorus conversion treatment. The calcium-phosphorus-containing conversion solution has a calcium ion concentration of 0.01 mol / L, a phosphate ion concentration of 0.0083 mol / L, a Ca / P molar ratio of 1.2, a pH of 5.0, a treatment temperature of 25℃, and a treatment time of 60 min, forming a dual-gradient corrosion-resistant conversion layer on the scaffold surface. The dual-gradient corrosion-resistant conversion layer includes a MgF2-enriched inner layer close to the low-aluminum-magnesium-aluminum alloy substrate and a calcium-phosphorus-enriched outer layer located outside the MgF2-enriched inner layer. The thickness of the MgF2-enriched inner layer is 0.2 μm, the thickness of the calcium-phosphorus-enriched outer layer is 0.3 μm, and the total thickness of the dual-gradient corrosion-resistant conversion layer is 0.5 μm. S4. By mass, the biodegradable polymer sealing solution comprises 100 parts of biodegradable polymer, 0.5 parts of heparinized hyaluronic acid-REDV peptide composite active component, and 1000 parts of organic solvent; the biodegradable polymer is a blend of polylactic acid-glycolic acid copolymer and polytrimethylene carbonate, with a mass ratio of polylactic acid-glycolic acid copolymer to polytrimethylene carbonate of 1:0.2; the heparinized hyaluronic acid-REDV peptide composite active component is REDV peptide grafted with heparinized hyaluronic acid, and dispersed in the biodegradable polymer sealing solution in the form of lyophilized microparticles; the organic solvent is a mixed solvent of hexafluoroisopropanol and ethanol; the biodegradable polymer sealing solution is directly coated onto the surface of the dual-gradient corrosion-resistant conversion layer, dried at 25°C, and then cured at 45°C for 4 h to form an active flexible sealing layer with a thickness of 1 μm, thereby obtaining a medical magnesium-aluminum alloy vascular stent.

[0027] Comparative Example 3: The difference between this comparative example and Example 1 is that the biodegradable polymer sealing solution in step S4 does not contain heparinized hyaluronic acid-REDV peptide complex active components, but is composed only of biodegradable polymer and organic solvent.

[0028] The method for preparing the vascular stent in this comparative example is as follows: S1. Based on mass percentage, a low-aluminum-magnesium-aluminum alloy ingot is selected, comprising Al 0.3%, Zn 0.3%, Ca 0.05%, Mn 0.05%, with the balance being Mg and unavoidable impurities; wherein the Fe content is not higher than 0.005%, the Ni content is not higher than 0.001%, and the Cu content is not higher than 0.002%; the above-mentioned low-aluminum-magnesium-aluminum alloy ingot is homogenized at 360℃ for 12 h, and then hot-extruded at 250℃ with an extrusion ratio of 10; subsequently, it is cold-drawn in 3 passes with a cumulative deformation of 20%; and then recrystallized and annealed at 180℃ for 30 min to obtain low-aluminum-magnesium-aluminum alloy microtubes; the average grain size of the obtained low-aluminum-magnesium-aluminum alloy microtubes is approximately 2 μm, and the average size of the aluminum-containing second phase is approximately 0.1 μm, and the aluminum-containing second phase does not form a continuous network grain boundary phase; S2. The low-aluminum-magnesium-aluminum alloy microtubes obtained in step S1 are laser-cut to form a vascular stent blank; the vascular stent blank is then subjected to deburring and electrochemical polishing treatments, and then surface activation treatment with carboxyl groups is performed using an aqueous solution containing citric acid to obtain an activated stent; the surface roughness Ra of the stent after treatment is 0.05 μm. S3. The activated scaffold obtained in step S2 is first placed in a fluorine-containing conversion solution for fluorine conversion treatment. The fluorine-containing conversion solution has a fluoride ion concentration of 0.05 mol / L, a pH of 4.0, a treatment temperature of 20℃, and a treatment time of 30 min. Then, it is placed in a calcium-phosphorus-containing conversion solution for calcium-phosphorus conversion treatment. The calcium-phosphorus-containing conversion solution has a calcium ion concentration of 0.01 mol / L, a phosphate ion concentration of 0.0083 mol / L, a Ca / P molar ratio of 1.2, a pH of 5.0, a treatment temperature of 25℃, and a treatment time of 60 min, forming a dual-gradient corrosion-resistant conversion layer on the scaffold surface. The dual-gradient corrosion-resistant conversion layer includes a MgF2-enriched inner layer close to the low-aluminum-magnesium-aluminum alloy substrate and a calcium-phosphorus-enriched outer layer located outside the MgF2-enriched inner layer. The thickness of the MgF2-enriched inner layer is 0.2 μm, the thickness of the calcium-phosphorus-enriched outer layer is 0.3 μm, and the total thickness of the dual-gradient corrosion-resistant conversion layer is 0.5 μm. S4. The stent obtained in step S3 is placed in a weakly alkaline buffer solution containing dopamine hydrochloride to react and form a polydopamine interface anchoring layer. The concentration of dopamine hydrochloride is 0.5 g / L, the pH of the weakly alkaline buffer solution is 8.0, and the reaction time is 10 min. Subsequently, a biodegradable polymer sealing solution without active components is prepared. By mass, the biodegradable polymer sealing solution includes 100 parts of biodegradable polymer and 1000 parts of organic solvent. The biodegradable polymer is a blend of polylactic acid-glycolic acid copolymer and polytrimethylene carbonate, and the mass ratio of polylactic acid-glycolic acid copolymer to polytrimethylene carbonate is 1:0.2. The organic solvent is a mixed solvent of hexafluoroisopropanol and ethanol. The biodegradable polymer sealing solution without active components is coated on the surface of the polydopamine interface anchoring layer, dried at 25°C, and then cured at 45°C for 4 h to form a flexible sealing layer with a thickness of 1 μm, thus obtaining a medical magnesium-aluminum alloy vascular stent.

[0029] Performance testing 1. Corrosion current density The corrosion current density of each group of vascular stents was measured using an electrochemical workstation to evaluate their corrosion resistance in a simulated physiological environment. The test medium was phosphate-buffered saline (PBS, pH 7.4) or simulated body fluid (SBF), and the test temperature was controlled at 37 ± 0.5 °C. A three-electrode system was used, with the stent sample as the working electrode, a platinum sheet electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Before testing, the stent sample was immersed in the test medium for 30 min to stabilize, and the open-circuit potential was recorded. Potentiodynamic polarization testing was performed after the open-circuit potential fluctuation was less than 5 mV. The test scan range was -250 mV to +500 mV relative to the open-circuit potential, and the scan rate was 0.5 mV / s. After the test, the corrosion current density Icorr was calculated using the Tafel extrapolation method, with units of μA / cm². A lower corrosion current density indicates better corrosion protection of the stent surface.

[0030] 2.28-day in vitro mass loss rate The 28-day mass loss rate of each group of vascular stents was tested using an in vitro immersion method to evaluate the degradation rate and controllable degradation performance of the stents. The test medium was PBS buffer, pH 7.4, and the immersion temperature was 37±0.5℃. Before the test, the initial dry mass of each group of stents was weighed and recorded as m0. Then, the stents were placed in centrifuge tubes or sealed glass bottles, and PBS buffer was added at a sample surface area to immersion liquid volume ratio of 1 cm2:20 mL. The samples were then placed in a constant temperature water bath or incubator at 37℃ and immersed for 28 days. The PBS buffer was changed every 2 days during the immersion period to maintain a stable simulated physiological environment. After immersion, the samples were removed, gently rinsed with deionized water, and surface corrosion products were removed using a chromic acid-containing solution or a magnesium corrosion product removal solution commonly used in the field. Subsequently, the samples were washed with deionized water and anhydrous ethanol, and vacuum dried at 37℃ to constant weight. The remaining dry mass was weighed and recorded as m1. The mass loss rate was calculated using the following formula: Quality loss rate (%) = (m0-m1) / m0×100%.

[0031] The lower the mass loss rate, the slower the stent degrades within 28 days; the more uniform the corrosion morphology of each part, the better the uniformity of stent degradation.

[0032] 3.28 d radial support force retention rate The radial support performance of each group of vascular stents before and after in vitro degradation was tested using a radial compression testing device or a vascular stent radial force tester. Before testing, the stents were inflated to their nominal diameter using a balloon, and the initial outer diameter of the stents was recorded. Unsoaked samples were placed in a radial compression fixture and compressed radially at a compression rate of 0.1 mm / s until the outer diameter decreased by 10%, and the corresponding radial support force was recorded as F0. Another sample from the same group was soaked in PBS buffer at 37±0.5℃ and pH 7.4 for 28 days, with the PBS buffer being changed every 2 days during the soaking period. After soaking, the samples were removed, gently rinsed with deionized water, and dried at 37℃. The radial support force after 28 days of soaking was then tested under the same compression conditions and recorded as F28. The radial support force retention rate was calculated using the following formula: Radial support force retention rate (%) = F28 / F0 × 100%.

[0033] A higher radial support retention rate indicates that the mechanical support of the stent decreases less during in vitro degradation, and it is better able to meet the vascular support needs in the early stages of implantation.

[0034] 4. Crack density and adhesion area retention rate of the coating after expansion The integrity of the vascular stent coating after deformation was evaluated using balloon dilation combined with scanning electron microscopy. Each stent was first compressed to its delivery diameter, then inflated to its nominal diameter using a balloon at a pressure controlled at 8–12 atm for 30 s. After inflatation, the stent was removed, and the morphology of the coating on the outer surface of the stent struts was observed using scanning electron microscopy. The observation acceleration voltage was 5 kV–10 kV, and the magnification was 500x–2000x. At least five strut regions were randomly selected from each stent, with each region having a length of at least 1 mm. The number of through-cracks and the area of ​​coating peeling were recorded.

[0035] The coating crack density is calculated using the following formula: Coating crack density (cracks / mm2) = number of through cracks in the observation area / area of ​​the observation area.

[0036] The coating adhesion area retention rate is calculated using the following formula: Coating adhesion area retention rate (%) = (total observed area - coating peeling area) / total observed area × 100%.

[0037] The lower the crack density of the coating and the higher the adhesion area retention rate, the better the coating’s resistance to cracking and peeling during the support holding and expansion process.

[0038] 5. Endothelial cell adhesion rate The promoting effect of human umbilical vein endothelial cells (HUVECs) on endothelial cell adhesion on the surface of vascular scaffolds in each group was evaluated. Before the test, scaffold samples in each group were sterilized by UV irradiation for 30 min and washed three times with sterile PBS. The scaffold samples were placed in 24-well cell culture plates, and HUVEC cell suspension was added to each well at a cell seeding density of 1×10⁵ cells / mL. The plates were incubated at 37℃ in a 5% CO₂ incubator for 4 h. After incubation, the samples were gently washed three times with sterile PBS to remove non-adhering cells. Subsequently, the cells were fixed with 4% paraformaldehyde for 15 min, and the nuclei were stained with DAPI or fluorescent dye. The number of cells adhering to the scaffold surface was observed using a fluorescence microscope, and at least five fields of view were randomly selected from each sample for counting.

[0039] Endothelial cell adhesion rate is calculated using the following formula: Endothelial cell adhesion rate (%) = number of cells adhering to the scaffold surface / initial number of seeded cells × 100%.

[0040] Table 1. Comprehensive performance test results of vascular stents

[0041] As shown in Table 1, the corrosion current density of the vascular stents obtained in Examples 1-3 was all below 5 μA / cm², the 28-day mass loss rate was controlled within 10%, and the 28-day radial support force retention rate was all above 80%. This indicates that the present invention, through low-aluminum-magnesium-aluminum alloy tissue regulation and the construction of a dual-gradient corrosion-resistant conversion layer, can effectively reduce the stent corrosion rate and delay the decay of mechanical support performance. Compared with Example 1, Comparative Example 1 did not undergo complete tissue regulation treatment, resulting in a corrosion current density that increased to 12.74 μA / cm², a 28-day mass loss rate that increased to 18.69%, and a 28-day radial support force retention rate that decreased to 59.4%. This indicates that grain homogenization and the discontinuous discrete distribution of the aluminum-containing second phase can reduce local galvanic corrosion and improve the service stability of the stent. Comparative Example 2 did not construct a calcium-phosphorus enriched outer layer, but only formed a MgF2 enriched layer. Its corrosion current density, mass loss rate, and coating crack density were all higher than those of Example 1, indicating that the dual-gradient corrosion-resistant structure formed by the MgF2 enriched inner layer and the calcium-phosphorus enriched outer layer has better corrosion resistance and interface stability than a single fluorine-containing conversion layer. Comparative Example 3 did not have a polydopamine interface anchoring layer. After expansion, the coating crack density increased to 13.92 cracks / mm2, indicating that the polydopamine interface anchoring layer can significantly improve the coating's resistance to cracking and peeling during gripping and balloon expansion. Comparative Example 4 did not add the heparinized hyaluronic acid-REDV peptide composite active component. Its endothelial cell adhesion rate was only 62.9%, significantly lower than that of Example 1, indicating that the composite active component can effectively promote early endothelial cell adhesion, which is beneficial to vascular endothelial repair after stent implantation.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent, characterized in that, Includes the following steps: S1. Magnesium alloy ingots containing Al, Zn, Ca and Mn are subjected to homogenization treatment, hot extrusion, cold drawing and recrystallization annealing treatment in sequence to obtain low-aluminum magnesium-aluminum alloy micro tubes with uniform grains and discontinuous discrete distribution of aluminum-containing second phase. S2. Laser cutting is performed on the low-aluminum-magnesium-aluminum alloy microtubes obtained in step S1 to form a vascular stent blank. The vascular stent blank is then subjected to deburring, electrochemical polishing, and surface activation treatment containing carboxyl or phosphate groups to obtain an activated stent. S3. The activated scaffold obtained in step S2 is subjected to fluorine-containing conversion treatment and calcium-phosphorus-containing conversion treatment in sequence to form a dual-gradient corrosion-resistant conversion layer on the surface of the scaffold. The dual-gradient corrosion-resistant conversion layer includes a MgF2-enriched inner layer close to the low-aluminum-magnesium-aluminum alloy substrate and a calcium-phosphorus-enriched outer layer located outside the MgF2-enriched inner layer. S4. An interface anchoring layer containing catechol groups is formed on the surface of the dual-gradient corrosion-resistant conversion layer obtained in step S3. Then, a biodegradable polymer sealing liquid containing heparinized hyaluronic acid-REDV peptide composite active components is coated. After drying and low-temperature curing, an active flexible sealing layer is formed on the outside of the dual-gradient corrosion-resistant conversion layer, thus obtaining a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent.

2. The method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that, The low-aluminum magnesium-aluminum alloy in S1 comprises, by mass percentage: Al 0.3%–1.2%, Zn 0.3%–1.5%, Ca 0.05%–0.5%, Mn 0.05%–0.3%, with the balance being Mg and unavoidable impurities; wherein, the unavoidable impurities contain no more than 0.005% Fe, no more than 0.001% Ni, and no more than 0.002% Cu.

3. The method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that, The homogenization treatment in S1 is carried out at a temperature of 360℃~420℃ for 6 h~12 h; the hot extrusion temperature is 250℃~350℃ and the extrusion ratio is 10~40; the cold drawing is carried out in 3~8 passes with a cumulative deformation of 20%~60%; the recrystallization annealing temperature is 180℃~260℃ and the time is 5 min~30 min.

4. The method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that, The average grain size of the low-aluminum-magnesium-aluminum alloy microtubes in S1 is 2 μm to 15 μm, the average size of the aluminum-containing second phase is 0.1 μm to 3 μm, and the aluminum-containing second phase does not form a continuous network grain boundary phase.

5. The method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that, The surface activation treatment containing carboxyl or phosphate groups in S2 is carried out using an aqueous solution containing one or more of citric acid, phytic acid, polyacrylic acid, and phosphate. After treatment, the surface roughness Ra of the scaffold is 0.05 μm to 0.30 μm.

6. The method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that, The fluorine-containing conversion treatment in S3 is carried out using a fluorine-containing conversion solution with a fluoride ion concentration of 0.05 mol / L to 0.5 mol / L, a pH of 4.0 to 6.5, a treatment temperature of 20℃ to 50℃, and a treatment time of 5 min to 30 min. The calcium-phosphorus conversion treatment is carried out using a calcium-phosphorus conversion solution with a calcium ion concentration of 0.01 mol / L to 0.20 mol / L, a phosphate ion concentration of 0.005 mol / L to 0.12 mol / L, a Ca / P molar ratio of 1.2 to 1.8, a pH of 5.0 to 7.0, a treatment temperature of 25℃ to 60℃, and a treatment time of 5 min to 60 min.

7. The method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that, The thickness of the MgF2 enriched inner layer in S3 is 0.2 μm to 3 μm, the thickness of the calcium-phosphorus enriched outer layer is 0.3 μm to 5 μm, and the total thickness of the dual-gradient corrosion-resistant conversion layer is 0.5 μm to 8 μm.

8. The method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that, The interface anchoring layer containing catechol groups in S4 is a polydopamine layer; the polydopamine layer is formed by reacting the scaffold obtained in step S3 in a weakly alkaline buffer solution containing dopamine hydrochloride, wherein the concentration of dopamine hydrochloride is 0.5 g / L to 2.0 g / L, the pH of the weakly alkaline buffer solution is 8.0 to 8.8, and the reaction time is 10 min to 60 min.

9. The method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that, The biodegradable polymer sealing solution in S4 comprises, by mass, 100 parts of biodegradable polymer, 0.5-8 parts of heparinized hyaluronic acid-REDV peptide composite active component, and 1000-5000 parts of organic solvent; the biodegradable polymer is a blend of polylactic acid-glycolic acid copolymer and polytrimethylene carbonate, wherein the mass ratio of polylactic acid-glycolic acid copolymer to polytrimethylene carbonate is 1:(0.2-1.5), and the heparinized hyaluronic acid-REDV peptide composite active component is REDV peptide grafted with heparinized hyaluronic acid.

10. The method for preparing a controllable degradable, highly corrosion-resistant medical magnesium-aluminum alloy vascular stent according to claim 1, characterized in that, The thickness of the active flexible sealing layer is 1 μm to 15 μm; the drying temperature is 25℃ to 45℃; the low-temperature curing temperature is 45℃ to 70℃; and the low-temperature curing time is 0.5 h to 4 h.

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