Locally degradable active dense net stent and preparation method thereof

Abstract

The invention relates to a biomedical material, in particular to a locally degradable active dense net stent and a preparation method thereof. A locally degradable active dense mesh stent is formed by weaving superfine magnesium alloy wires and nickel-titanium memory alloy wires, the magnesium alloy wires and the memory alloy wires are mixed and woven to form rhombic main meshes, and the proportion of the magnesium alloy wires to the memory alloy wires is 1: 9-1: 3. The preparation method comprises the following steps: S1, preparing the superfine magnesium wire by adopting a rotary swaging and drawing composite process; s2, the superfine magnesium alloy wires and the nickel-titanium memory alloy wires form a gradient composite structure through a three-dimensional tubular braiding machine, the composite stent is prepared, and the magnesium alloy wires and the memory alloy wires are mixed and braided to form rhombic main grids; and S3, carrying out chemical polishing treatment on the woven composite stent to improve the surface quality, and loading an active coating on the surface through degradation coupling of magnesium wires to realize degradation regulation and control and promote endothelialization functions.

Description

Technical Field

[0001] The present invention relates to a biomedical material, and more particularly to a locally degradable active dense mesh stent and a preparation method thereof. Background Art

[0002] Aneurysms are a disease that seriously threatens human life and health, manifested as local lesions of the aortic blood vessels. Once the blood vessels bleed after the lesion, it will seriously endanger people's lives.

[0003] Among many types of aneurysms, intracranial aneurysms are special due to their disease location. Once ruptured, the intracerebral hemorrhage caused has the characteristics of rapid onset and high mortality. According to statistics, the annual incidence of subarachnoid hemorrhage (SAH) caused by intracranial aneurysm rupture is 1%-2%, and the mortality rate of the first rupture is as high as 20%-30%. Even the mortality rate of the second rupture of untreated survivors is as high as 60%. For the treatment of intracranial aneurysms, the traditional craniotomy for aneurysm clipping has the risk of easy intracranial infection, while endovascular interventional treatment has the characteristics of less trauma and high safety, so it has become the preferred treatment plan for this lesion.

[0004] With the development of minimally invasive technology, the main methods for endovascular interventional treatment of intracranial aneurysms mainly include: stent-assisted coil embolization and implantation of a dense mesh stent. Stent-assisted coil embolization solves the problem that the coils cannot be densely packed in the coil embolization by using an auxiliary stent. However, due to the limitation of the stent, there will be embolization dead angles, resulting in segmented packing. In contrast, the dense mesh stent is based on hemodynamics, changes the flow direction of the blood, and then reduces the impact of the vortex in the aneurysm cavity on the aneurysm wall, achieving the restoration of normal blood flow, gradually disappearing the lesion site, and achieving the purpose of curing aneurysms. Whether it is the short-term surgical risk or the long-term recovery of patients, the dense mesh stent with a blood flow guiding effect can achieve a better effect of curing aneurysms.

[0005] At present, the clinically widely used traditional metal dense mesh stents mainly include cobalt-chromium alloy and nickel-titanium alloy. Since such materials are non-degradable, long-term storage will cause intimal hyperplasia and thrombus risk, limiting the further application of the dense mesh stent. The reason for this pathology is the high metal coverage rate (>30%) of the dense mesh stent, resulting in the formation of acute thrombus and slow endothelialization effect. And the degradable materials (such as polylactic acid, ferroalloy, etc.) in the research and development stage have insufficient support force, are prone to early exploration, and the degradation rate and endothelialization rate do not match, making it difficult to meet the implantation requirements. Therefore, a single material is difficult to simultaneously meet the requirements of the dense mesh stent for mechanical support, controllable degradation, and biological functionality. There is an urgent need to develop a new type of dense mesh stent.

[0006] The ideal degradable dense mesh stent is completely degraded after implantation, which can effectively reduce the occurrence of postoperative ischemic complications and reduce the intake of dual antiplatelet drugs. At present, the existing technologies have not achieved the effect of complete degradation, and dual antiplatelet drugs still need to be taken after surgery. Patent literatures such as "A Degradable Local Dense Mesh Stent" (CN208989271U), "A Degradable Dense Mesh Stent and Its Weaving Method" (CN116983482A), "A Degradable Double-Layer Stent" (CN215080335U), "Blood Flow Guiding Device" (CN222218023U), "Dense Mesh Stent and Its Preparation Method" (CN119061577A), etc. all mention the concept of locally degradable stents. However, from the material perspective, using polymer fibers as degradable materials, the key concerns are the weaving and structural design of the stent, etc. According to the feedback of clinical needs, the therapeutic effect after the implantation of the dense mesh stent lies in the speed of its endothelialization, and none of the above-mentioned degradable dense mesh stents mention the promotion of endothelialization function.

[0007] In fact, the microenvironment after the degradation of polymer fibers presents an acidic environment, which is not conducive to the proliferation of endothelial cells. Therefore, it can be speculated that the current degradable dense mesh stents have poor promotion effect on endothelialization function. And the current research on degradable dense mesh stents mainly focuses on the degradation function and the weaving structure design of the stent. Summary of the Invention

[0008] Aiming at the deficiencies of the existing technology, the present invention proposes a locally degradable active dense mesh stent and its preparation method. It mainly includes the preparation of ultra-fine magnesium alloy wires suitable for dense mesh stents, the composite weaving scheme of degradable functional dense mesh stents, and the surface treatment of the final stent. Through material composite and structural design, the degradability, endothelialization-promoting characteristics of magnesium alloy and the super-elastic support ability of shape memory alloy are integrated to solve the problem of the contradiction between the support force and the degradation rate in the existing technology.

[0009] The technical solution adopted by the present invention: A locally degradable active dense mesh stent is woven from ultra-fine magnesium alloy wires and nickel-titanium shape memory alloy wires. A rhombic main grid is formed by the mixed weaving of magnesium alloy wires and shape memory alloy wires, and the ratio of magnesium alloy wires to shape memory alloy wires is 25%:75% to 90%:10%.

[0010] On the surface of the locally degradable active dense mesh stent, a corrosion-resistant - endothelialization-promoting sequential degradation coating is loaded. The degradation-regulating corrosion-resistant - endothelialization-promoting sequential degradation coating has a corrosion-resistant layer MgF 2 as the base layer, and a copper polythiolate as the functional coating to achieve the endothelialization-promoting function and degradation regulation.

[0011] The weaving scheme (preparation method) of the composite dense mesh stent of the present invention: Select magnesium alloys with good biocompatibility, including but not limited to ZE21B, ZE21C, AZ31, etc. Through the composite weaving of magnesium alloys and shape memory alloys, the magnesium alloy realizes the functions of biodegradation and promoting endothelialization, and the shape memory alloy realizes the stent support ability; combined with surface polishing and the construction of a corrosion-resistant and drug-loaded coating, the degradation regulation and the promotion of endothelialization are realized synchronously.

[0012] Reciprocating extrusion combined with hot extrusion is used to process the magnesium alloy ingot into a magnesium alloy rod with a diameter of 2-3 mm. Then, the above-mentioned magnesium alloy rod is subjected to rotary forging treatment at a temperature from room temperature to 300 °C, with a deformation per pass of 10-15% and a cumulative deformation of ≥60%. Through the synergistic effect of dynamic recrystallization and stacking fault structure, the multiplication of dislocations is promoted, and the tensile strength (≥350 MPa) and ductility (elongation at break ≥15%) of the magnesium alloy rod are improved.

[0013] To obtain the above-mentioned ultra-fine magnesium wires, the rotary-forged magnesium alloy bars are subjected to multi-pass cold drawing, combined with intermediate annealing, and finally ultra-fine magnesium wires with a diameter of 50-100 μm are obtained. The drawing speed adopted in the present invention is 0.3-2 m / min, the deformation between passes is 5-8%, the heat treatment temperature is 200-250 °C, and the time is 10-20 min.

[0014] By adopting the above special processing technology and introducing stacking faults to promote dislocation multiplication, the plastic deformation ability during the drawing process of magnesium alloy wires can be improved, thereby breaking through the bottleneck problem of poor room-temperature deformation ability of traditional magnesium alloys and realizing the preparation of ultra-fine magnesium wires.

[0015] Select the ultra-fine magnesium alloy wires prepared above and composite them with commercial shape memory alloy wires (diameter 36-50 μm) for hybrid weaving, where the ratio of magnesium alloy wires to shape memory alloy wires is 25%:75% to 90%:10%.

[0016] The weaving parameters of the present invention are that the magnesium alloy wires and the shape memory alloy wires are evenly mixed. A 24-48 spindle three-dimensional tubular weaving machine is used, the weaving angle is 55°-70°, the linear density is 8-12 picks / cm, and the woven stent is subjected to shape memory heat treatment in a vacuum furnace (450-500 °C, holding for 15-30 min, and then water quenching) to make the nickel-titanium alloy obtain a superelastic phase transformation temperature (Af = 30-35 °C).

[0017] The surface of the above heat-set composite mesh stent is polished with a phosphoric acid-glycerol mixed solution, and the ratio of the phosphoric acid-glycerol mixed solution is phosphoric acid:glycerol:ethanol = 80 ml:50 ml:180 ml.

[0018] Before polishing, the surface of the stent needs to be cleaned with anhydrous ethanol. The method is to put the composite stent into anhydrous ethanol and ultrasonically clean it for three minutes, and repeat this process 2-3 times.

[0019] The cleaned composite stent is polished by soaking it in a phosphoric acid-glycerol solution for 180 s. After polishing, the stent is quickly placed in absolute ethanol and ultrasonically treated for 3-5 min. This ultrasonic process is repeated 2-3 times. After taking out the ultrasonically cleaned stent and drying it, the polishing process is completed.

[0020] To have both controllable degradation and endothelialization promotion functions, the surface of the stent needs to be loaded with a coating. On the basis of the above coating, a functional coating for promoting endothelialization is loaded on the stent again. The coating is copper polythiolate.

[0021] Advantages of the invention: 1. As a medical device, the functional vascular stent for promoting endothelialization has great potential in the interventional treatment of aortic aneurysms and has broad application prospects. The locally degradable active dense mesh stent of the present invention proposes the application of a composite braided structure of magnesium alloy and shape memory alloy. Using magnesium alloy wire as the degradable material, compared with polymer fibers, magnesium alloy has excellent biological activity, which can facilitate the proliferation of endothelial cells. Secondly, the microenvironment after the degradation of magnesium alloy is an alkaline environment, and the generated Mg 2+ is also beneficial to the rapid proliferation of endothelial cells. According to the report in the article (doi:10.1136 / jnis-2024-022527), the endothelialization effect of magnesium alloy two weeks after implantation is better than that of the fully non-degradable dense mesh stent six months after implantation. Therefore, it shows that the dense mesh stent with magnesium alloy as the degradable wire has excellent endothelialization promotion function.

[0022] 2. The preparation method of the locally degradable active dense mesh stent of the present invention and the preparation method reintroduce a drug coating for promoting endothelialization function in the surface coating treatment, which can quickly achieve the adhesion of endothelial cells in the initial stage of implantation, and the degradation of magnesium alloy in the middle and late stages of implantation can achieve rapid endothelialization function. However, the room temperature plastic deformation ability of magnesium alloy is poor, and it is difficult to process magnesium alloy wire suitable for dense mesh stents. Another difference in this patent is the discussion of the influence of special processing on the preparation of ultra-fine magnesium wire. The prior art mainly focuses on the braiding and structural design of degradable stents, using polymer fibers as degradable materials; in this patent, magnesium alloy wire is used as the degradable material, and the focus is on the endothelialization promotion function of dense mesh stents and the preparation of ultra-fine wires suitable for dense mesh stents.

[0023] 3. The locally degradable active mesh stent of the present invention has both degradable characteristics and rapid endothelialization promotion function, which better meets the actual clinical needs. In the prior art, the microenvironment after the degradation of polymer fibers presents an acidic environment, which is not conducive to the proliferation of endothelial cells. Therefore, the effect of promoting endothelialization function is poor. According to the literature (doi:10.1136 / jnis-2024-022527), magnesium alloy has excellent biological activity and can facilitate the proliferation of endothelial cells. Secondly, the microenvironment after the degradation of magnesium alloy is an alkaline environment, and the generated Mg 2+ is also conducive to the rapid proliferation of endothelial cells. The endothelialization effect two weeks after the implantation of magnesium alloy is better than that of the fully non-degradable mesh stent at 6 months. Therefore, the degradable mesh stent of the present invention uses ultrafine magnesium alloy as the degradable material and has excellent endothelialization promotion function.

[0024] 4. The present invention compositely weaves a mesh stent with magnesium alloy wires and shape memory alloy wires. While ensuring the realization of the shunt guiding function, the composite form of magnesium wires and shape memory alloy wires can solve the coordinated balance problem of dynamic degradation and mechanical support, which is mainly achieved in the following ways: 1) Introduce special processing to prepare ultrafine magnesium alloy wires, and realize the locally degradable function of the stent through magnesium wires, reduce the metal coverage rate of the mesh stent, thereby reducing the risk of postoperative ischemic complications, and the magnesium alloy releases bioactive ions (Mg 2+ ) after degradation, which has the function of promoting endothelialization. 2) Through the loading of the time-sequential degradation coating, realize the endothelialization promotion function and corrosion resistance characteristics, and synchronously realize degradation regulation and endothelialization promotion.

[0025] 5. The locally degradable active mesh stent of the present invention uses magnesium alloy with good biocompatibility. Introducing swaging processing can greatly promote the activation of partial dislocations in the magnesium alloy, and then form a high-density stacking fault inside the material. During the subsequent room-temperature wire drawing process of the magnesium alloy wire, the introduction of the stacking fault changes part of the crystal structure, which can promote the formation of partial dislocations, and then improve the plastic deformation ability and strength and toughness of the magnesium alloy wire during the wire drawing process. The tensile strength of the magnesium alloy wire prepared by special processing is ≥380 MPa, and the elongation rate is ≥20%, which can meet the weaving requirements of the composite mesh stent. Description of the Drawings

[0026] Figure 1 It shows a schematic diagram of the locally degradable mesh stent after weaving in Example 1; Figure 2 It shows a schematic diagram of the locally degradable mesh stent after weaving in Example 2; Figure 3 It shows the chemical polishing effect of the locally degradable mesh stent woven in Example 2; Figure 4 It shows a schematic diagram of the diamond main grid of the locally degradable composite mesh stent woven in Example 2; Figure 5 Shown is a time-sequential degradation coating with corrosion resistance regulation and endothelialization promotion loaded on the surface of the stent, which degrades Figure 6 Shown is a schematic diagram of the radio-opaque markers at both ends of the locally degradable composite mesh stent in Example 3. Figure 7 Shown is the self-expansion effect of the locally degradable composite mesh stent in Example 3 after being pushed. Figure 8 Shown is the imaging effect of the locally degradable composite mesh stent in Example 3 implanted in the rabbit carotid artery. Detailed implementation manners

[0027] To make the technical concept and advantages for realizing the invention purpose of the present invention clearer and more understandable, the technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the following embodiments are only used to explain and illustrate the preferred implementation manners of the present invention, and should not be regarded as and do not constitute a limitation on the scope of patent protection required by the present invention. Embodiment

[0028] A locally degradable active mesh stent / composite woven active mesh stent is woven from ultra-fine magnesium alloy wires and nitinol shape memory alloy wires. A rhombic main grid is formed by the mixed weaving of magnesium alloy wires and shape memory alloy wires. There are a total of 48 magnesium alloy wires and shape memory alloy wires, and their ratio is 1:2. The diameter of the magnesium alloy wires used is 100 microns, and the diameter of the shape memory alloy wires is 50 microns.

[0029] The preparation process of the locally degradable active mesh stent in this embodiment includes: Step S1, take ultra-fine magnesium alloy wires with a diameter of 100 microns and nitinol shape memory alloy wires in proportion; Step S2, compound and weave the ultra-fine magnesium alloy wires and nitinol shape memory alloy wires through a three-dimensional tubular weaving machine to obtain a locally degradable mesh stent. The woven stent is as shown in Figure 1 shown; Step S3, chemically polish the woven composite stent, and load a time-sequential degradation coating with corrosion resistance regulation and endothelialization promotion on the surface of the stent. The time-sequential degradation coating with corrosion resistance regulation and endothelialization promotion has a corrosion-resistant layer MgF 2 as the base layer and copper polythiolate as the functional coating to achieve the functions of degradation regulation and endothelialization promotion.

[0030] In step S1, the weaving machine uses 24 - 48 spindles for weaving, the weaving angle is 55° - 70°, and the linear density is 8 - 12 picks / cm; the woven stent is subjected to heat setting treatment at a temperature of 450 - 500 °C, and the superelastic strain recovery rate is ≥95%.

[0031] In step S1, the magnesium alloy used is ZE21B (ZE21C or AZ31 can also be used). The ultrafine magnesium alloy wire is strengthened by rotary swaging. The process parameters of the rotary swaging are as follows: the temperature ranges from room temperature to 250°C, the single-pass deformation amount is 10-15%, and the strain rate is 0.1-1 s⁻¹. In the cold drawing process, the pass deformation amount is 5-8%, the intermediate annealing temperature is 200-250°C, and the annealing time is 10-20 min. Example

[0032] This example is a locally degradable composite braided active dense mesh stent and its preparation method. The process includes: Step S1, take ultrafine magnesium alloy wires according to a proportion or prepare ultrafine magnesium alloy wires and Ni-Ti shape memory alloy wires. There are a total of 48 wires of magnesium alloy wires and shape memory alloy wires, and their ratio is 1:3. The diameter of the ultrafine magnesium alloy wire used for braiding is 70 μm, and the diameter of the shape memory alloy wire is 46 μm; Step S2, construct a gradient composite structure by three-dimensional tubular braiding of the ultrafine magnesium alloy wire and the Ni-Ti shape memory alloy wire to obtain a composite stent. The outer diameter of the stent is 4 mm. Among them, a diamond-shaped main grid is formed by mixing and braiding the magnesium alloy wire and the shape memory alloy wire, as Figure 2 shown; Step S3, perform chemical polishing on the braided composite stent to improve the surface quality. The polished stent is as Figure 3 shown in Figure 4, and a degradation-regulating corrosion-resistant - promoting endothelialization sequential degradation coating is loaded on the surface of the stent, as Figure 5 shown. The degradation-regulating corrosion-resistant - promoting endothelialization sequential degradation coating has a corrosion-resistant layer MgF 2 as the base layer and copper polythiolate as the functional coating.

[0033] Step S3, adopt chemical polishing. The polishing solution is a phosphoric acid - glycerol solution, and its ratio is phosphoric acid: glycerol: ethanol = 80 ml: 50 ml: 180 ml. Before polishing, clean the surface of the stent with absolute ethanol. Put the composite stent into absolute ethanol and ultrasonically clean it for three minutes, and repeat this process 2-3 times; then put the cleaned stent into the phosphoric acid - glycerol solution and soak it for 180 s. Immediately after polishing, put the stent into absolute ethanol and perform ultrasonic treatment for 3-5 min, and repeat this ultrasonic process 2-3 times.

[0034] For the degradable composite braided active dense mesh stent of the present invention, the preparation process of the used ultrafine magnesium alloy wire is as follows: Perform reciprocating extrusion + hot extrusion on the magnesium alloy ingot, followed by multi-pass rotary swaging strengthening with a cumulative deformation amount ≥ 60%. Subsequently, perform multi-pass cold drawing and intermediate annealing to obtain an ultrafine magnesium alloy wire with a diameter of 50-100 μm, whose tensile strength ≥ 380 MPa and elongation ≥ 20%.

[0035] The present invention prepares high-strength magnesium wires with a diameter ≤ 100 μm (tensile strength ≥ 380 MPa; elongation ≥ 20%) through rotary forging strengthening and multi-pass cold drawing processes, solving the problems of insufficient strength and toughness of traditional magnesium alloy wires and difficulty in meeting the weaving requirements in terms of size; adopts magnesium alloy-memory alloy composite weaving, integrating the degradability and endothelialization-promoting characteristics of magnesium alloy with the superelastic support ability of memory alloy to achieve a dynamic balance between degradation and mechanical properties; enhances the surface quality of the composite stent through surface chemical polishing and loads a degradation regulation-promoting endothelialization sequential degradation coating on the surface to simultaneously achieve the functions of degradation regulation and endothelialization promotion.

[0036] The degradable composite woven active mesh stent of this embodiment has high supportability, controllable degradation and multiple biological functions, can adapt to the blood vessel remodeling cycle, and significantly reduces postoperative ischemic complications. Example

[0037] This example uses the locally degradable composite woven active mesh stent prepared in Example 2 for implantation experiments in rabbit carotid arteries and conducts self-expansion function and degradation experiments. The process includes: Step S1: Use the composite woven locally degradable mesh stent in Example 2 to make a radiographic mark at one end of the stent, as Figure 6 shown; Step S2: Assemble the mesh stent obtained in S1 above into a delivery device, and the self-expansion effect after pushing is as Figure 7 shown; Step S3: Implant the locally degradable composite woven active mesh stent obtained in S1 above into the rabbit carotid artery and evaluate its self-expansion function. Select adult New Zealand white rabbits (body weight 2.5 - 3.0 kg) and implant the woven stent into the rabbit carotid artery model. Through the stent delivery device described in Step S2, accurately release the locally degradable mesh stent (diameter 4.0 mm, length 10 mm) at the target blood vessel segment. After the operation, use optical coherence tomography (OCT) for three-dimensional morphological evaluation. The imaging results show that the locally degradable mesh stent has good wall apposition with the blood vessel, as Figure 8 shown.

[0038] Among them, the above imaging results show that the mesh stent prepared by composite weaving has excellent self-expansion function and can meet the implantation requirements of the mesh stent.

[0039] In view of the problems that traditional dense mesh stents are non-degradable, the endothelialization rate is too slow, and the mechanical support performance of fully degradable stents cannot meet the use requirements, the present invention innovatively proposes to use magnesium alloy and memory alloy composite materials, composite woven dense mesh stents, and through structural design, the magnesium alloy can achieve the functions of promoting endothelialization and degradation, and the memory alloy can achieve the supporting capacity. The designed composite active dense mesh stent is expected to solve the pain points in clinical application. The triple innovation concept of materials, processes, and structures mentioned in the present invention has undoubtedly opened up a new path for the research and development and application of vascular stent materials, and is expected to lead the innovation and development in the field of medical devices.

[0040] Based on the design concept of the present invention, it can also play an innovative role in other wire-woven medical device fields, thereby hopefully solving the long-standing technical bottleneck of "mechanical support-degradation rate-biological function" in the field of medical devices.

Claims

1. A locally degradable active dense mesh stent, characterized in that: The stent is woven from ultrafine magnesium alloy wires and nickel-titanium memory alloy wires, and a diamond-shaped main grid is formed by mixing and weaving the magnesium alloy wires and the memory alloy wires, wherein the ratio of the magnesium alloy wires to the memory alloy wires is 25%:75% to 90%:10%.

2. The locally degradable active dense mesh stent according to claim 1, characterized in that: The surface of the stent is loaded with a corrosion-resistant and endothelialization-promoting sequential degradation coating, wherein the degradation-regulating corrosion-resistant and endothelialization-promoting sequential degradation coating has a base layer of corrosion-resistant MgF2 and a functional coating of polythioic acid copper, so as to achieve degradation regulation and endothelialization-promoting functions.

3. The locally degradable active dense mesh stent according to claim 1 or 2, characterized in that: The preparation process of the ultrafine magnesium alloy wire is as follows: the magnesium alloy ingot is subjected to reciprocating extrusion + hot extrusion and then strengthened by multiple rotary forging, with a cumulative deformation of ≥60%, followed by multiple cold drawing and intermediate annealing to obtain ultrafine magnesium alloy wire with a diameter of 50-100μm, with a tensile strength of ≥380MPa and an elongation of ≥20%.

4. The method for preparing a locally degradable active dense mesh stent according to claim 1 or 2, characterized in that the process include: Step S1, taking ultrafine magnesium alloy wire or preparing ultrafine magnesium alloy wire and nickel-titanium memory alloy wire in proportion; Step S2, constructing a gradient composite structure of ultrafine magnesium alloy wires and nickel-titanium memory alloy wires through a three-dimensional tubular braiding machine to obtain a composite stent, wherein the magnesium alloy wires and the memory alloy wires are mixed and braided to form a diamond-shaped main grid; Step S3, chemically polishing the braided composite stent to improve the surface quality, and loading a degradation-regulating corrosion-resistant coating that promotes endothelialization sequential degradation on the stent surface.

5. The method for preparing a partially degradable active dense mesh stent according to claim 4, characterized in that: In step S1, ultrafine magnesium alloy wire is prepared: the magnesium alloy ingot is subjected to reciprocating extrusion + hot extrusion and then subjected to multiple rotary forging strengthening, with a cumulative deformation of ≥60%, followed by multiple cold drawing and intermediate annealing to obtain an ultrafine magnesium alloy wire with a diameter of 50-100μm, a tensile strength of ≥380MPa, and an elongation of ≥20%; the diameter of the nickel-titanium memory alloy wire used is 36-50μm.

6. The method for preparing a partially degradable active dense mesh stent according to claim 5, characterized in that: The magnesium alloy is selected from ZE21B, ZE21C or AZ31, and the rotary forging strengthening process parameters in step S1 are: temperature from room temperature to 250°C, single-pass deformation amount of 10-15%, and strain rate of 0.1-1s⁻¹.

7. The method for preparing a partially degradable active dense mesh stent according to claim 6, characterized in that: In step S1, the deformation amount per pass in the cold drawing process is 5-8%, the intermediate annealing temperature is 200-250° C., and the annealing time is 10-20 min.

8. The method for preparing a partially degradable active dense mesh stent according to claim 5, 6 or 7, characterized in that: In step S2, the braiding machine uses 24-48 spindles for weaving, the braiding angle is 55°-70°, and the line density is 8-12 picks / cm; the braided stent is subjected to heat setting treatment at a temperature of 450-500°C, and the superelastic strain recovery rate is ≥95%.

9. The method for preparing a partially degradable active dense mesh stent according to claim 5, 6 or 7, characterized in that: In step S3, chemical polishing is adopted, and the polishing solution is a phosphoric acid-glycerol solution, and the ratio thereof is phosphoric acid: glycerol: ethanol = 80 ml: 50 ml: 180 ml.

10. The method for preparing a partially degradable active dense mesh stent according to claim 9, characterized in that: In step S3, chemical polishing is used. Before polishing, the surface of the bracket is cleaned with anhydrous ethanol. The composite bracket is placed in anhydrous ethanol and ultrasonically cleaned for three minutes. This process is repeated 2-3 times; then the cleaned bracket is placed in a phosphate-glycerol solution and soaked for 180 seconds. The polished bracket is quickly placed in anhydrous ethanol and ultrasonically treated for 3-5 minutes. This ultrasonic process is repeated 2-3 times.

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