Stent and manufacturing method therefor

Abstract

Provided is a stent with which the complete recovery of a cerebral aneurysm can be accelerated. One aspect of the present invention is a stent 20 that is placed so as to be compression-bonded to a blood vessel wall and straddle a cerebral aneurysm 21, and has the function of promoting endothelialization prior to the complete occlusion of the cerebral aneurysm in a state of being compression-bonded to the blood vessel wall. This stent 20 is composed of a cylindrical braided body braided with a wire rod. The wire rod is obtained by coating the surface of an element wire, the element wire contains a magnesium alloy containing at least 90 at% of Mg, or pure magnesium, and the function is to promote neointimal formation on the neck of the cerebral aneurysm.

Description

Stent and manufacturing method thereof

[0001] The present invention relates to a stent for an aneurysm and a method for manufacturing the same.

[0002] A cerebral aneurysm is a swelling of a cerebral artery. These swellings typically form when a branching portion of a large blood vessel in the brain expands gradually due to pressure from cerebral blood flow. Rupture of a cerebral aneurysm can result in subarachnoid hemorrhage, making it a very dangerous condition. To prevent subarachnoid hemorrhage, cerebral aneurysms must be treated before rupture occurs. Surgical treatments include craniotomy (clipping) or endovascular treatment using a cerebral aneurysm stent. Treatment using a cerebral aneurysm stent involves inserting a tube through the femoral artery at the base of the leg and guiding it to the aneurysm. A flow diverter stent is deployed from a catheter across the aneurysm and placed in the blood vessel. This slows blood flow to the aneurysm, allowing it to gradually thrombose. As the thrombus is absorbed, the aneurysm gradually shrinks, eventually healing completely. As a stent for cerebral aneurysms, Patent Document 1 discloses a flow diverter stent made of a NiTi alloy.

[0003] JP 2013-135794 A

[0004] As described above, placing a flow diverter stent in a blood vessel slows blood flow to a cerebral aneurysm, leading to gradual thrombosis of the aneurysm. Specifically, it is believed that neointima is first gradually formed at the neck of the aneurysm, leading to gradual thrombosis of the aneurysm. Therefore, by realizing a flow diverter stent that promotes endothelialization, which generates neointima more quickly prior to thrombosis of the aneurysm, it is believed that the aneurysm can be cured more quickly. As a result, the burden on the patient can be reduced. Various aspects of the present invention aim to provide a stent that can accelerate the complete healing of a cerebral aneurysm and a method for manufacturing the same.

[0005] Various aspects of the present invention are described below. [1] A stent that is placed across a cerebral aneurysm by being pressed against the blood vessel wall, and that, when pressed against the blood vessel wall, has the function of promoting endothelialization prior to complete occlusion of the cerebral aneurysm. [2] The stent in [1] above, characterized in that the stent is composed of a tubular braided body woven from wire material. [3] The stent in [2] above, characterized in that the wire material has a coated surface, the wire material contains a magnesium alloy containing 90 atomic % or more of Mg or pure magnesium, and the function is to promote neointima formation in the neck of the cerebral aneurysm. [4] The stent in [3] above, characterized in that the wire material has a surface coated with a bioabsorbable polymer material coating, a parylene coating, or an MPC polymer coating. [5] The stent in [4] above, characterized in that the bioabsorbable polymer material coating, the parylene coating, or the MPC polymer coating each contain a drug. [6] The stent according to any one of [3] to [5] above, wherein the function is achieved by forming a skeleton in the braided body that serves as a scaffold for endothelial formation during the absorption process of the magnesium alloy or pure magnesium into the body, and the skeleton remaining for a certain period of time. [7] The stent according to [6] above, wherein the skeleton is a structure formed along the wires of the braided body. [8] The stent according to any one of [3] to [5] above, wherein 50% to 96% of all wires of the braided body contain magnesium alloy or pure magnesium, and each of the wires has an outer diameter of 80 μm or less. [9] The stent according to [4] or [5] above, wherein the wire strands have a 0.2% yield strength of 300 MPa or more and a ductility of 3% or more.

[10] The stent according to any one of [3] to [5] above, wherein the magnesium alloy is an alloy having a crystalline structure having an α-Mg phase or an α-Mg phase and a long-period stacking ordered structure phase.

[11] The stent according to [4] or [5] above, characterized in that the thickness of each of the bioabsorbable polymer material coating, the parylene coating, or the MPC polymer coating is 10 μm or less.

[12] The stent according to [1] above, characterized in that the stent is composed of a tubular braided body woven with wires, and the wires are coated on their surfaces with a film containing a magnesium-containing compound, a magnesium alloy, or pure magnesium.

[13] The stent according to

[12] above, characterized in that the wires are made of a bioabsorbable material or a radiopaque metal material.

[14] The stent according to any one of [2] to [5],

[12] , and

[13] above, characterized in that the tubular braided body is woven with two or more types of wires.

[15] The stent according to any one of [1] to [5],

[12] , and

[13] above, characterized in that the vascular wall in the function is a human vascular wall.

[16] A method for manufacturing a stent, comprising: (a) preparing a wire made of a magnesium alloy containing 90 atomic % or more of Mg or pure magnesium; (b) applying a coating to the wire by electrospinning, by attaching a positively charged polymer jet to the surface of the wire while rotating a counter electrode around the wire; (c) forming a wire by heat treatment to smooth the coating film; and (d) braiding the wire around a core using a braiding machine with a winding mechanism to form a tubular braid.

[17] A method for manufacturing a stent, comprising, after step (d), performing a heat treatment to increase the crystallinity of the coating film of step (c) and to impart shape memory to the braid and provide self-expandability to the braid. Various aspects of the present invention can provide a stent that can hasten the complete healing of cerebral aneurysms, and a method for manufacturing the same.

[0006] Fig. 1 is a schematic diagram showing a state in which a flow diverter stent 20 according to one embodiment of the present invention is placed in a blood vessel 22 so as to straddle a cerebral aneurysm 21. Fig. 2(A) is a schematic diagram showing the state in which a flow diverter stent (Co / Cr-FD) 120 containing Co / Cr as a comparative example is placed in a blood vessel 22 so as to straddle a cerebral aneurysm 21, whereby the cerebral aneurysm 21 thrombustes and progresses to complete healing. Fig. 2(B) is a schematic diagram showing the state in which a flow diverter stent (Mg-FD) 20 containing a magnesium alloy containing 90 atomic % or more of Mg or pure magnesium is placed in a blood vessel 22 so as to straddle a cerebral aneurysm 21, whereby the cerebral aneurysm 21 thrombustes and progresses to complete healing. Figure 3 shows SEM images of neointima formation on the surface of a flow diverter stent (MgFD PLLA-coated) made of a magnesium alloy wire with a PLLA coating on its surface, and a flow diverter stent (MgFD Bare) made of an uncoated magnesium alloy wire, after implantation in the abdominal aorta of a rabbit 14 days later. Figure 4 shows photographs of experimental results demonstrating the process by which a framework serving as a scaffold for endothelialization is formed on the braided Mg-FD stent at the neck of a cerebral aneurysm. Figure 5 shows part of the test system used to obtain the experimental results shown in Figure 4. Figure 6 is a schematic diagram illustrating a method for applying a coating to a wire 12 based on the electrospinning method. Figure 7(A) is a photograph showing the state of the wire coated with a film using the method shown in Figure 6, and Figure 7(B) is a photograph showing the state of the wire after heat treatment to smooth the film coated on the wire shown in Figure 7(A). FIG. 8 is a schematic diagram showing a braiding machine with a winding mechanism.

[0007] Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, the present invention is not limited to the following description, and those skilled in the art will readily understand that various modifications in form and detail are possible without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the following description of the embodiments. (First Embodiment) FIG. 1 is a schematic diagram illustrating a flow diverter stent 20 according to one aspect of the present invention, deployed in a blood vessel 22 so as to straddle a cerebral aneurysm 21. The flow diverter stent 20 shown in FIG. 1 is a stent that is crimped against the vascular wall 22 and deployed so as to straddle the cerebral aneurysm 21. When crimped against the vascular wall 22, it has the function of promoting endothelialization prior to complete occlusion of the cerebral aneurysm 21. The vascular wall in this function is preferably a human vascular wall. The stent 20 is composed of a tubular braided body woven with wire. Furthermore, the stent 20 has self-expanding properties, allowing it to be crimped against the vascular wall 22 and deployed. Although the present embodiment uses a self-expanding flow diverter stent 20, a non-self-expanding stent that is deployed in the blood vessel wall by balloon expansion may also be used. The wire of the stent 20 may have a coated surface. The wire may include a magnesium alloy containing 90 atomic % or more of Mg or pure magnesium. The above function may promote neointima formation in the neck of a cerebral aneurysm. The tubular braid may be woven with one type of wire or two or more types of wire. Figure 2(A) is a schematic diagram showing the progression of thrombosis and complete healing of a cerebral aneurysm 21 when a comparative example flow diverter stent 120 containing Co / Cr (Co / Cr-FD) is deployed in a blood vessel 22 across the cerebral aneurysm 21. The cerebral aneurysm 21 shown in Figures 2(A) and 2(B) was derived from the results of an experiment using an abdominal aortic aneurysm in a rabbit.As shown in Figure 2(A), in the Co / Cr-containing flow diverter stent 120, thrombus formation begins within the cerebral aneurysm 21 from three months (3M or more), the cerebral aneurysm 21 thrombusizes by six months (6M), and after six months (6M or more), the cerebral aneurysm gradually shrinks as the thrombus is absorbed, eventually leading to complete healing. Here, neointima 31 forms to cover the neck of the cerebral aneurysm 21 six months (6M or more) after the cerebral aneurysm 21 thrombusizes. In other words, the cerebral aneurysm 21 thrombusizes as the neointima 31 forms around the neck of the cerebral aneurysm 21. However, even when the entire cerebral aneurysm 21 thrombusizes, the neointima 31 does not completely cover the neck. As the cerebral aneurysm gradually shrinks with the absorption of the thrombus, the neointima 31 forms to completely cover the neck. This flow diverter stent 120 is not bioabsorbed and remains in the blood vessel 22. FIG. 2(B) is a schematic diagram showing the process of thrombus formation and complete healing of a cerebral aneurysm 21 after a flow diverter stent (Mg-FD) 20 containing a magnesium alloy containing 90 atomic % or more of Mg or pure magnesium is placed in a blood vessel 22 across the cerebral aneurysm 21. As shown in FIG. 2(B), before a thrombus forms in the cerebral aneurysm 21 within two weeks to one month (2W-1M), a neointima 31 forms to cover the neck of the cerebral aneurysm 21. In contrast, in the flow diverter stent 120 containing Co / Cr shown in FIG. 2(A), a neointima 31 does not yet form around the neck of the cerebral aneurysm 21. As shown in FIG. 2(B), the neointima 31 almost completely covers the neck of the cerebral aneurysm 21 within one month to three months (1M-3M). After three months (3M), the neointima 31 completely covers the neck of the cerebral aneurysm 21. In contrast, in the case of the Co / Cr-containing flow diverter stent 120 shown in Figure 2(A), neointima 31 has not yet formed significantly at the neck of the cerebral aneurysm 21. Then, as shown in Figure 2(B), after three months (3M~), the cerebral aneurysm becomes thrombotic, and as the thrombus is absorbed, the cerebral aneurysm gradually shrinks, eventually leading to a complete cure.In contrast, in the Co / Cr-containing flow diverter stent 120 shown in Figure 2(A), after three months (3 to 6 months), neointima 31 begins to form at the neck of the cerebral aneurysm 21, and thrombus formation begins within the cerebral aneurysm 21. From these findings, it can be said that the earlier the neointima 31 forms at the neck of the cerebral aneurysm 21, the earlier the thrombus formation in the cerebral aneurysm and the earlier the complete healing of the cerebral aneurysm. As described above, the stent 20 is a tubular braided structure made of wires. The wires may be coated on their surfaces with a bioabsorbable polymer material, a parylene coating (paraxylylene resin coating), or an MPC (2-methacryloyl-loxyethyl phosphorylcholine) polymer coating. However, in this embodiment, wires coated with bioabsorbable PLLA (polylactic acid) are used. Specific examples of bioabsorbable polymer coatings include polycaprolactone, polyglycolic acid (PGA), copolymer of glycolic acid and L-lactic acid (PGLA), copolymer of glycolic acid and DL-lactic acid (PGDLLA), poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), poly-DL-lactic acid (PDLLA), copolymer of L-lactic acid and ε-caprolactone (LCL), and poly-p-dioxanone (PDO). The thickness of each of the bioabsorbable polymer coatings, parylene coatings, and MPC polymer coatings is preferably 10 μm or less. Furthermore, the stent 20 preferably contains 50% to 96% of the total wire material of the braided body of the stent 20. The magnesium alloy is preferably an alloy having a crystalline structure with an α-Mg phase or a α-Mg phase and a long-period stacking ordered structure phase. The long period stacking ordered structure phase is a Long Period Stacking Order (LPSO) structure phase. The outer diameter of each of the wires is preferably 80 μm or less. The lower limit of the outer diameter of each of the wires is preferably 30 μm. The wire strands of the wire preferably have a 0.2% yield strength of 300 MPa or more and a ductility of 3% or more.As mentioned above, the wires are preferably made of a magnesium alloy containing 90 atomic % or more of Mg or pure magnesium. In this embodiment, wires of a magnesium alloy of Mg-0.9Zn-2.05Y-0.15Al-0.1Yb (at.%) are used. Figure 3 shows SEM images of a flow diverter stent (MgFD PLLA-coated) made from a wire of the above-mentioned magnesium alloy with a PLLA coating on its surface, and a flow diverter stent (MgFD Bare) made from a wire of the above-mentioned magnesium alloy without a coating, placed in the abdominal aorta of a rabbit. The neointima on the surface of each flow diverter stent was evaluated 14 days later. Figure 2(B) shows the flow diverter stent (MgFD PLLA-coated) used. As shown in Figure 3, the neointima was completely covered in both stents within two weeks, forming a neointima thick enough to obscure the stent's irregularities, demonstrating high biocompatibility. This corresponds to 2W in Figure 2(B). This also confirms that, as shown in Figure 2(B), a neointima 31 forms to cover the neck of the cerebral aneurysm 21 prior to thrombus formation within two weeks to one month (2W-1M). While the results shown in Figures 2(A), 2(B), and 3 are based on animal (rabbit) experiments, similar effects are likely to be observed in humans. Furthermore, the bioabsorbable polymer coating, parylene coating, or MPC polymer coating may each contain a drug. This drug may regulate endothelialization, for example, promote endothelialization. The stent's ability to promote endothelialization prior to complete occlusion of the cerebral aneurysm 21 is achieved by forming a scaffold for endothelialization in the braided structure during the absorption process of the magnesium alloy or pure magnesium into the body, and this scaffold remains for a certain period of time. The framework may be a structure formed along the wires of the braid. It has been confirmed that the Mg-FD shown in Fig. 2(B) allows the neointima to grow and cover the neck of the aneurysm earlier than the Co / Cr-FD shown in Fig. 2(A), resulting in earlier and higher probability of occlusion of the aneurysm.This is thought to be because the Mg-FD shown in Figure 2(B) forms a scaffold for endothelialization in the braided stent more quickly than the Co / Cr-FD shown in Figure 2(A). Figure 4 is a photograph of experimental results showing the process of formation of a scaffold for endothelialization in the braided Mg-FD stent at the neck of a cerebral aneurysm. Figure 5 is a diagram showing part of the test system used to obtain the experimental results shown in Figure 4. The system reproduces a human cerebral artery and aneurysm, and an Mg-FD stent is placed in a crimped position against the vessel wall and straddles the aneurysm, thereby recreating an environment similar to that of a human cerebral artery, thereby evaluating the degradation performance of the Mg-FD stent over time. The wire material for the Mg-FD stent shown in Figure 4 is an uncoated wire made of a magnesium alloy (Mg-0.9Zn-2.05Y-0.15Al-0.1Yb (at.%)). An experiment was conducted in which an Mg-FD stent (not shown) shown in Fig. 2(B) was placed in a blood vessel 42 of a cerebral artery 41 in a test system shown in Fig. 5, and blood with the chemical components and concentrations shown in Table 1 was flowed through the blood vessel 42 in the direction of arrow 43 at the flow rate, pressure, and temperature shown in Table 2, to observe the change over time of the Mg-FD stent. The results of the experiment are shown in Fig. 4. As shown in Figure 4, after 20 days, a skeletal structure begins to form along the stent's braided wires (dark wires) in the Mg-FD stent at the neck of the cerebral aneurysm. Next, after 23 days, the stent's wires begin to dissolve (absorb) in the blood, decompose, and decrease, and the skeletal structure increases. Next, after 25 days, the stent's wires decrease further, and the skeletal structure increases accordingly. Finally, after 30 days, most of the stent's wires are absorbed by the blood, and a skeletal structure forms along the stent's braided wires. Although not shown, there was no significant change (decomposition) in the Mg-FD stent at the neck until 15 days. Considering the results shown in Figures 2(A), 2(B), 3, and 4, the reason why the Mg-containing flow diverter stent (Mg-FD) 20 shown in Figure 2(B) results in faster neointima formation 31 at the neck of the cerebral aneurysm 21 than the Co / Cr-containing flow diverter stent 120 shown in Figure 2(A) is believed to be as follows: As the Mg in the braided wires of the stent shown in Figure 4 dissolves in the blood, a skeleton-like structure is formed along the braided wires. This skeleton remains for a certain period of time and serves as a scaffold for endothelial formation, promoting neointima formation at the neck of the cerebral aneurysm as shown in Figure 3. Note that the results shown in Figure 3 were obtained from an animal (rabbit) experiment, while the results shown in Figure 4 are a reproduction of a human cerebral artery and cerebral aneurysm. However, these results suggest that similar effects and trends are likely to be obtained in humans. According to this embodiment, it is possible to realize a flow diverter stent 20 that promotes endothelialization, which generates neointima 31 more quickly prior to thrombosis in the cerebral aneurysm 21, thereby hastening the complete healing of the cerebral aneurysm. As a result, the burden on the patient can be reduced. (Second Embodiment) The stent according to this embodiment is a flow diverter stent that is crimped against the blood vessel wall and placed so as to straddle the cerebral aneurysm. In this state, while crimped against the blood vessel wall, it has the function of promoting endothelialization prior to complete occlusion of the cerebral aneurysm, and is similar to the first embodiment in that the stent is made of a tubular braided body made of wire.The following describes differences from the first embodiment, and omits a description of the same parts. The wire of the stent is a wire whose surface is coated with a coating containing a magnesium-containing compound, a magnesium alloy, or pure magnesium. The wire is preferably made of a bioabsorbable material or a radiopaque metal material. Using a radiopaque metal material makes it easier to observe the condition of the stent placed in the patient's blood vessel. Examples of bioabsorbable materials include bioabsorbable polymeric materials (e.g., polycaprolactone, polyglycolic acid (PGA), copolymer of glycolic acid and L-lactic acid (PGLA), copolymer of glycolic acid and DL-lactic acid (PGDLLA), poly-L-lactic acid (PLLA), poly-D-lactic acid (PDLA), poly-DL-lactic acid (PDLLA), copolymer of L-lactic acid and ε-caprolactone (LCL), and poly-p-dioxanone (PDO)). Examples of radiopaque metal materials include platinum tungsten (e.g., Pt-8 wt % W) and Nitinol (nickel-titanium alloy), a shape-memory alloy. This embodiment can also achieve the same effects as the first embodiment. (Third Embodiment) In this embodiment, a method for manufacturing a stent according to the first embodiment will be described. FIG. 6 is a schematic diagram illustrating a method for applying a coating to a wire 12 based on an electrospinning method. Fig. 7(A) is a photograph showing the state of a wire coated with a film using the method shown in Fig. 6 , and Fig. 7(B) is a photograph showing the state of the wire after heat treatment to smooth the film coated on the wire shown in Fig. 7(A). Fig. 8 is a schematic diagram 61 showing a braiding machine with a winding mechanism 62. A wire 12 made of a magnesium alloy containing 90 atomic % or more of Mg or pure magnesium is prepared (step (a)). Next, as shown in Fig. 6 , a coating is applied to the wire 12 by electrospinning, by attaching a positively charged polymer jet to the surface of the wire 12 while rotating a counter electrode 14 around the wire 12 (step (b)). Step (b) will be described in detail below. As shown in Fig. 6 , the wire 12 is moved at a predetermined speed in the direction indicated by arrow AR4.A counter electrode 14 is disposed around the wire 12 and is supported by a support 13. The counter electrode 14 and support 13 are configured to rotate around the wire 12 at a preset rotational speed in the direction indicated by arrow AR3 by a rotary drive unit (not shown). While the counter electrode 14 rotates around the wire 12, a positively charged polymer jet is discharged onto the surface of the wire 12 by a polymer discharge unit 11, causing the polymer jet to adhere to the surface of the wire 12. This results in a coating on the wire 12. The support 13 has a funnel shape and includes a bowl-shaped main portion 131 with an opening 131a at its bottom, and a cylindrical portion 132 whose inside is connected to the inside of the main portion 131 via the opening 131a. The counter electrode 14 is also bowl-shaped and disposed so as to cover the inner wall of the main portion 131 of the support 13. The counter electrode 14 is grounded via a ground wire (not shown). The polymer discharge unit 11 includes a cylindrical syringe 111 storing a polymer liquid therein, a nozzle 112 attached to the tip of the syringe 111, a plunger 113 inserted on the side of the syringe 111 opposite the nozzle 112, and a voltage application unit 114 that applies a DC voltage to the nozzle 112. The voltage application unit 114 is a DC voltage source that applies a predetermined DC voltage to the nozzle 112. The polymer discharge unit 11 also includes a pressing mechanism (not shown) that presses the plunger 113 into the syringe 111 by air pressure. The polymer discharge unit 11 is configured to discharge the polymer liquid from the nozzle 112 toward the portion of the wire 12 facing the counter electrode 14 while maintaining the nozzle 112 at a higher potential than the counter electrode 14. Furthermore, it is preferable that the tip 112a of the nozzle 112, where the injection port is provided, is located within the projection area A1 of the counter electrode 14 in the direction of the rotation axis of the counter electrode 14. The polymer liquid is a liquid in which a polymer is dissolved in an organic solvent. As the polymer, a polymer with high bioabsorbability can be used, for example, PLLA (polylactic acid). As the organic solvent, dichloromethane, trichloromethane (CHCl), ３), dichloroethane, N,N-dimethylformamide, tetrahydrofuran, toluene, pyridine, acetonitrile, formamide, benzene, dimethylacetamide, N-methylpyrrolidone, hexane, 1,4-dioxane, acetone, methanol, ethanol, etc. Next, a heat treatment is performed to smooth the coating film, thereby forming a wire (step (c)). Step (c) will be described in detail below. By performing a heat treatment on the film coated on the wire 12 (see FIG. 7(A)) in step (b), a wire with a smoothed film (see FIG. 7(B)) can be formed. This heat treatment melts the polymer and smooths the film. The heat treatment here is preferably performed at a temperature of 30°C or higher and 250°C or lower for a heat treatment time of 1 second or higher and 10 minutes or shorter. Next, as shown in FIG. 8, the wire is braided around the core using a braiding machine 61 equipped with a winding mechanism 62, thereby forming a tubular braided body 51 (step (d)). The core material is preferably a low-friction core material. A subsequent step (c) may be performed to increase the crystallinity of the coating film and to impart shape memory and self-expandability to the braided body 61. The heat treatment temperature is preferably 30°C to 180°C for a period of 1 second to 10 hours. A method for using the flow diverter stent manufactured as described above will be described with reference to FIG. 1 . A physician guides a catheter into the skull via the femoral artery at the base of the leg. The flow diverter stent 20 is inserted into a blood vessel 22 from the catheter so as to straddle a cerebral aneurysm 21. The self-expanding stent is deployed so as to press against the blood vessel wall. When the flow diverter stent 20 is placed in the parent blood vessel 22 in which the cerebral aneurysm 21 is present, the mesh structure on the surface of the flow diverter stent 20 restricts the blood flow (not shown) into the cerebral aneurysm 21, gradually promoting thrombosis inside the cerebral aneurysm 21, and the neck portion of the aneurysm 21 becomes covered with a stent neointima, resulting in complete occlusion of the cerebral aneurysm 21 after several months. Moreover, the flow diverter stent 20 itself gradually decomposes over the course of several months and eventually disappears, leaving no foreign body behind.However, if a non-bioabsorbable wire material or the like is used in part of the flow diverter stent 20 to ensure visibility, that material may not disappear and may remain.

[0008] 12 wire 14 counter electrode 20 stent 21 cerebral aneurysm 22 blood vessel 31 neointima 41 cerebral artery 42 blood vessel 43 arrow 51 braided body 61 braiding machine 62 winding mechanism

Claims

1. A stent that is placed so as to straddle a cerebral aneurysm by being pressed against the blood vessel wall, and that, when pressed against the blood vessel wall, has the function of promoting endothelialization prior to complete occlusion of the cerebral aneurysm.

2. The stent according to claim 1, characterized in that the stent is made of a tubular braided body made of wire material.

3. A stent according to claim 2, wherein the wire material has a coated surface, the wire contains a magnesium alloy containing 90 atomic % or more of Mg or pure magnesium, and the function is to promote neointima formation in the neck of the cerebral aneurysm.

4. A stent according to claim 3, wherein the wire material has a surface coated with a bioabsorbable polymer material, or a parylene coating, or an MPC polymer coating, and the wire is made of a magnesium alloy containing 90 atomic % or more of Mg or pure magnesium.

5. A stent according to claim 4, wherein each of the bioabsorbable polymer material coating, the parylene coating, and the MPC polymer coating contains a drug.

6. A stent according to any one of claims 3 to 5, characterized in that the function is realized by forming a skeleton in the braided body that serves as a scaffold for endothelial formation during the process of absorption of the magnesium alloy or pure magnesium into the body, and the skeleton remaining for a certain period of time.

7. A stent according to claim 6, wherein the framework is a structure formed along the wire material of the braided body.

8. A stent according to any one of claims 3 to 5, characterized in that 50% to 96% of all wires of the braided body contain magnesium alloy or pure magnesium, and the outer diameter of each of the wires is 80 μm or less.

9. A stent according to claim 4 or 5, wherein the wire of the wire material has a 0.2% yield strength of 300 MPa or more and a ductility of 3% or more.

10. A stent according to any one of claims 3 to 5, wherein the magnesium alloy is an alloy having a crystalline structure having an α-Mg phase or an α-Mg phase and a long-period stacking ordered structure phase.

11. A stent according to claim 4 or 5, wherein the thickness of each of the bioabsorbable polymer material coating, the parylene coating, and the MPC polymer coating is 10 μm or less.

12. A stent according to claim 1, characterized in that the stent is composed of a tubular braided body made of wire material, and the surface of the wire material is coated with a film containing a magnesium-containing compound, a magnesium alloy, or pure magnesium.

13. A stent according to claim 12, wherein the wires are made of a bioabsorbable material or an X-ray opaque metal material.

14. A stent according to any one of claims 2 to 5, 12 and 13, wherein the tubular braided body is braided with two or more types of wire materials.

15. A stent according to any one of claims 1 to 5, 12 and 13, characterized in that the vessel wall in the function is a human vessel wall.

16. A method for manufacturing a stent, comprising: (a) the step of preparing a wire made of a magnesium alloy containing 90 atomic % or more of Mg or pure magnesium; (b) the step of applying a coating to the wire by electrospinning, by attaching a positively charged polymer jet to the surface of the wire while rotating a counter electrode around the wire; (c) the step of forming a wire by heat treatment to smooth the coating film; and (d) the step of braiding the wire around a core material using a braiding machine with a winding mechanism, to form a tubular braided body.

17. A method for manufacturing a stent according to claim 16, characterized in that after step (d), there is a step of performing a heat treatment to increase the crystallinity of the coating film of step (c) and to give the braided body shape memory and self-expandability.

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