Stents

Abstract

The present disclosure provides a stent comprising: an annular first strut in a wave shape; an annular second strut in a wave shape that is adjacent to the first strut in the axial direction; a first extension that is formed on a first crest, said first crest being a portion of a plurality of crests in the first strut being convex toward the second strut side, and extends toward the second strut side from both sides of a bisecting line of the first crest; a second extension that is formed on a second crest, said second crest being at a position displaced in the circumferential direction from the first crest among a plurality of crests in the second strut being convex toward the first strut side, and extends toward the first strut side from both sides of a bisecting line of the second crest; and a bridge part disposed between the first extension and the second extension.

Description

[Technical field]

[0001] The present disclosure relates to stents. [Background technology]

[0002] As one embodiment of a medical stent, for example, US Pat. No. 7,264,633 discloses a stent having links connecting opposing peaks of two adjacent struts. Summary of the Invention [Problem to be solved by the invention]

[0003] The stent disclosed in U.S. Patent No. 7,264,633 has a configuration in which the links extend from only one side of the crests of the struts. Therefore, this stent is prone to stress concentration in the links and their surrounding areas as the stent transitions from one of the contracted and expanded states to the other. This stress concentration causes a deterioration in the shape precision of the stent.

[0004] An object of the present disclosure is to improve the shape accuracy of a stent compared to a configuration in which the portion connecting the circumferentially offset peaks of axially adjacent struts extends from only one side of the bisector of the first peak or the second peak. [Means for solving the problem]

[0005] A stent according to a first aspect has a first strut arranged along a cylindrical surface and forming a wavy shape with an amplitude direction in the axial direction of the cylindrical surface; a second strut arranged along the cylindrical surface and forming a wavy shape with an amplitude direction in the axial direction and adjacent to the first strut in the axial direction; a first extension portion formed on a first peak portion which is a part of a plurality of peak portions of the first strut that are convex towards the second strut side and extends along the first bisector from both sides of a first bisector that bisects the first peak portion to the second strut side along the first bisector; a second extension portion formed on a second peak portion which is a part of the plurality of peak portions of the second strut that are convex towards the first strut side and is shifted in the circumferential direction from the first peak portion and extends along the second bisector that bisects the second peak portion to the first strut side; and a bridging portion bridging the first extension portion and the second extension portion.

[0006] A stent according to a second aspect is the stent according to the first aspect, wherein the thickness of the bridging portion is equal to and uniform with the thickness of the first extension portion or the second extension portion.

[0007] A stent according to a third aspect is the stent according to the first or second aspect, wherein the first extension portion is elliptical with the first bisector as its major axis, and the second extension portion is elliptical with the second bisector as its major axis.

[0008] A stent according to a fourth aspect is a stent according to any one of the first to third aspects, wherein the edge of the bridging portion, when viewed from the radial direction of the cylindrical surface, is curved such that one end on the first extension side forms a common tangent with the edge of the first extension side at the boundary with the first extension side, and the other end on the second extension side forms a common tangent with the edge of the second extension side at the boundary with the second extension side.

[0009] A stent according to a fifth aspect is the stent according to any one of the first to fourth aspects, and is made of a shape memory alloy.

[0010] A stent according to a sixth embodiment is the stent according to any one of the first to fifth embodiments, and has a coating layer on the surface.

[0011] A stent according to a seventh aspect is the stent according to the sixth aspect, wherein the coating layer includes a ceramic layer.

[0012] A stent according to an eighth embodiment is the stent according to the sixth or seventh embodiment, wherein the coating layer includes a drug-eluting coating layer.

[0013] A stent according to a ninth aspect is a stent according to any one of the first to eighth aspects, wherein the thickness of the first struts and the second struts is in the range of 0.6 times or more and B or less of the minimum width B of the first struts and the second struts in the direction along the cylindrical surface. Effect of the Invention

[0014] The stent of the first aspect has improved shape precision compared to a configuration in which the portion connecting the circumferentially offset peaks of axially adjacent struts extends from only one side of the bisector of the first or second peak.

[0015] According to the stent of the second aspect, the shape precision of the stent is improved, compared to a configuration in which the thickness of the bridging portion is smaller than the thickness of the first extension portion or the second extension portion.

[0016] According to the stent of the third aspect, the shape precision of the stent is improved as compared with a configuration in which the first extension portion or the second extension portion is rectangular when viewed in the radial direction.

[0017] According to the stent of the fourth aspect, the shape precision of the stent is improved, compared to a configuration in which the ends of the edge portions of the bridging portions are straight.

[0018] The stent of the fifth aspect, when formed from a shape memory alloy, has improved shape precision of the stent compared to a configuration in which the portion connecting the first and second peaks extends only from one side of the bisector of the first or second peak.

[0019] According to the stent of the sixth aspect, in a configuration having a coating layer, the coating layer is less likely to peel off compared to a configuration in which the portion connecting the first and second peaks extends only from one side of the bisector of the first or second peak.

[0020] According to the stent of the seventh aspect, in a configuration in which the coating layer includes a ceramic layer, deterioration of the stent over time is suppressed compared to a configuration in which the portion connecting the first and second peaks extends from only one circumferential side of the bisector of the first or second peak.

[0021] In the stent of the eighth aspect, in a configuration in which the coating layer includes a drug-eluting coating layer, the drug-eluting effect of the stent is sustained for a long period of time, compared to a configuration in which the portion connecting the first and second peaks extends only from one side of the bisector of the first or second peak.

[0022] The stent according to the ninth aspect has a larger inner diameter than a configuration in which the strut thickness exceeds the minimum strut width, and is less susceptible to distortion than a configuration in which the strut thickness is less than 0.6 times the minimum strut width. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 is a development view of a stent in a processed state according to an embodiment of the present disclosure, which is developed into a flat shape along the circumferential direction. [Diagram 2] FIG. 13 is an enlarged view of a link of a stent according to an embodiment of the present disclosure. [Diagram 3] FIG. 2 is a cross-sectional view showing a base layer and a coating layer constituting a stent according to an embodiment of the present disclosure. [Figure 4]FIG. 13 is an enlarged view showing a link of a stent according to a comparative embodiment of the present disclosure. [Diagram 5] FIG. 13 is a development view of a stent according to a modified example of an embodiment of the present disclosure, which is developed in the circumferential direction. [Figure 6] FIG. 13 is an enlarged view showing a link of a stent according to a variation of an embodiment of the present disclosure. [Figure 7] FIG. 1 is a perspective view of a stent in an expanded state according to an embodiment of the present disclosure. [Figure 8] FIG. 1 is a perspective view of a stent in a reduced diameter state according to an embodiment of the present disclosure. [Figure 9] FIG. 13 is a development view of a stent according to a modified example of an embodiment of the present disclosure, which is developed in the circumferential direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] An example of a stent according to an embodiment of the present disclosure will be described with reference to FIGS.

[0025] (Stent 10) The stent 10 according to the present embodiment is a substantially cylindrical stent (see Figs. 7 and 8) used to expand the lumen of a stenotic portion when stenosis or the like occurs in a biological organ having a tubular structure such as a blood vessel. Specifically, the stent 10 is formed along a cylindrical surface having a length L and a diameter D of a tubular member (described in detail later) from which the stent 10 is made. The term "cylindrical surface" used in the following description includes not only a cylindrical surface having a length L and a diameter D, but also a part of the cylindrical surface, an axial extension of the cylindrical surface, and an expanded or contracted cylindrical surface. Fig. 1 is a development view of the stent 10 in a processed state cut out from a tubular member by laser processing, which is developed into a planar shape along the circumferential direction. That is, the diameter of the stent 10 shown in Fig. 1 is D. The stent 10 is, for example, a self-expanding stent, and has a function of being able to switch between an expanded diameter state shown in Fig. 7 and a contracted diameter state shown in Fig. 8. The diameter of the stent 10 in the expanded diameter state is larger than the diameter D of the stent in the processed state. In addition, the diameter of the stent 10 in the reduced diameter state is smaller than the diameter D of the stent 10 in the processed state. The stent according to the present disclosure is not limited to a self-expanding type, and may be a balloon-expandable stent. In the following description, unless otherwise specified, the dimensions and shape of the stent 10 in the processed state will be described.

[0026] In addition, arrows A, R, and C in each drawing indicate the axial direction, radial direction, and circumferential direction of the stent 10.

[0027] 1, the stent 10 has end struts 20 arranged at both axial ends of the stent 10, and a plurality of struts 30 arranged side by side in the axial direction between the two end struts 20. The stent 10 also has links 60 connecting the end struts 20 to the struts 30, and links 70 connecting adjacent struts 30. The stent 10 also has a marker 80 protruding outward in the axial direction from a portion of the end strut 20. In the stent 10, the end struts 20, struts 30, links 60, 70, and marker 80 are integrally formed.

[0028] The end struts 20 are annular members that extend along a cylindrical surface. The end struts 20 are formed in a wave shape with the axial direction of the stent 10 as the amplitude direction.

[0029] The end strut 20 has a plurality of peaks 22 that are convex on the opposite side to the strut 30 adjacent to the end strut 20 with respect to the center line CT of the wave of the end strut 20. The end strut 20 also has a plurality of peaks 24 that protrude toward the strut 30 adjacent to the end strut 20 with respect to the center line CT of the wave of the end strut 20. The end strut 20 also has a straight portion 26 that linearly connects the peaks 22 and 24. At the boundary between the straight portion 26 and the peaks 22 and 24, the edge of the straight portion 26 forms a common tangent to the edge of the peak 22 and the edge of the peak 24. Note that the peaks 22 and 24 of the end strut 20 according to the present disclosure respectively indicate the folded back portions of the wave of the end strut 20. In this embodiment, the peaks 22 and 24 are both formed in an arc shape on the inner peripheral side edge and the outer peripheral side edge when viewed from the radial direction.

[0030] As shown developed on a plane in Figure 1, the marker 80 is a roughly disc-shaped member extending along a cylindrical surface, formed so as to protrude from the top of one of the multiple peaks 22 of the end strut 20 on the opposite side to the peak 24 relative to the peak 22.

[0031] (Strut 30) The strut 30 is an annular member disposed along the cylindrical surface between the two end struts 20. The struts 30 are disposed side by side at a fixed interval in the axial direction. Each strut 30 is formed in a wave shape with the axial direction of the stent 10 as the amplitude direction. Each strut 30 has the same shape as the end strut 20. More specifically, the strut 30 of the embodiment is wavy with nine periods in one revolution along the cylindrical surface, and has a peak portion 32 that is convex on one side in the axial direction with respect to the center line of the wave, and a peak portion 34 that is convex on the other side. That is, the strut 30 of the embodiment has nine peak portions 32 and 34. The strut 30 also has a straight portion 36 that linearly connects the peak portion 32 and the peak portion 34. At the boundaries between straight portion 36 and peak portion 32 and peak portion 34, the edge of straight portion 36 forms a common tangent to the edge of peak portion 32 and the edge of peak portion 34. Note that peak portions 32, 34 of strut 30 according to the present disclosure each indicate the folded back portions of the waves of strut 30. In this embodiment, the peaks 32 and 34 are formed in an arc shape on both the inner peripheral edge and the outer peripheral edge as viewed in the radial direction. In addition, a bisector (including a bisector D1 described later) that bisects the peaks 32 and 34 as viewed in the radial direction is parallel to the axial direction. In other words, a pair of straight portions 36 connected to one peak 32, 34 are formed symmetrically (i.e. equiangularly) with respect to the bisector. Furthermore, the pair of straight portions 36 connected to one peak 32 gradually widen in the distance from each other as they move toward the peaks 34 adjacent to each other in the circumferential direction. Furthermore, the pair of straight portions 36 connected to one peak 34 gradually widen in the distance from each other as they move toward the peaks 32 adjacent to each other in the circumferential direction. The angle α formed between the pair of straight portions 36 is preferably within a range of 25° to 50° in the stent 10 in the expanded state. In the stent 10 in the reduced diameter state, the angle α between the pair of straight portions 36 is preferably within a range of -10° or more and -5° or less. When the angle α between a pair of straight portions 36 connected to one peak 32 has a negative value, the pair of straight portions 36 are gradually spaced apart from each other toward the circumferentially adjacent peaks 34, as shown in Fig. 8. When the angle α between a pair of straight portions 36 connected to one peak 34 has a negative value, the pair of straight portions 36 are gradually spaced apart from each other toward the circumferentially adjacent peaks 32, as shown in Fig. 8.

[0032] The struts 30 are arranged side by side in the axial direction as shown in Fig. 1. Two struts 30 adjacent to each other in the axial direction are arranged such that the wave phase shift in the circumferential direction is within a range of 10° to 90°. The amount of wave phase shift in the circumferential direction between two adjacent struts 30 is preferably within a range of 5° to 20°. Furthermore, among the multiple struts 30 arranged in the axial direction, the nth strut (n is an integer greater than or equal to 1) and the (n-2)th or (n+2)th strut are arranged so that their wave phases in the circumferential direction are the same.

[0033] The strut 30 adjacent to the end strut 20 is arranged such that the phase of the waves in the circumferential direction is shifted by 180° with respect to the end strut 20. That is, one end strut 20 (in FIG. 1, the lower side The strut 30 adjacent to the end strut 20 of the other end strut 20 (has a peak portion 32 facing the peak portion 24 of the end strut 20 in the axial direction. Although not shown in the figure, Page Upper The strut 30 adjacent to the end strut 20 is 32 The struts 30 adjacent to the end struts 20 are arranged axially opposite the crests 24 of the end struts 20. 32is connected via a link 60 to the peak portion 24 of the end strut 20 that faces it in the axial direction.

[0034] Two struts 30 adjacent to each other in the axial direction are connected such that some of the peaks 32a of the multiple peaks 32 of one strut 30 are connected to some of the peaks 34a of the multiple peaks 34 of the other strut 30 via links 70, which will be described in detail later. For example, in this embodiment, which includes struts 30 that are wavy with nine periods per revolution, axially adjacent struts 30 are connected to each other by three links 70 that are equally spaced in the circumferential direction. The peaks 32a of one strut 30 and the peaks 34a of the other strut 30 connected by links 70 are connected to each other by three links 70 that are equally spaced in the circumferential direction. Struts The peak portion 34 a of the strut 30 is the peak portion 34 that is closest to the peak portion 32 a of the strut 30 of the one side among the multiple peak portions 34 of the other strut 30 . Among the struts 30 arranged in the axial direction, the link 70 connecting the nth strut 30 (n is an even number of 2 or more) and the (n-1)th strut 30 is shifted in the circumferential direction from the link 70 connecting the nth strut 30 and the (n+1)th strut 30. Furthermore, the link 70 connecting the nth strut 30 and the (n-1)th strut 30 is inclined in the opposite direction to the link 70 connecting the nth strut 30 and the (n+1)th strut 30. Here, the peak 32a is an example of a first peak, and the peak 34a is an example of a second peak. If the odd-numbered struts 30 are an example of first struts, the even-numbered struts 30 are an example of second struts, and if the odd-numbered struts 30 are an example of second struts, the even-numbered struts 30 are an example of first struts.

[0035] (Detailed structure of Link 70) As described above, in the stent 10, the link 70 connects the peak 32a of one strut 30 to the peak 34a of the other strut 30 among two struts 30 that are adjacent in the axial direction. The link 70 includes an extension 44 formed on the peak 32a, an extension 54 formed on the peak 34a, and a bridging portion 72 that bridges between the extension 44 and the extension 54. In the following description, the bisector of the peak 32a will be referred to as the bisector D1, and the bisector of the peak 34a will be referred to as the bisector D2.

[0036] The extension 44 extends from both sides of the bisector D1 at the outer periphery of the peak 32a along the bisector D1 toward the strut 30 to be connected by the link 70. In this embodiment, the extension 44 is symmetrical with respect to the bisector D1. More specifically, the extension 44 is formed in an ellipse with the bisector D1 as the major axis. In this embodiment, the ellipse means that the outer edge viewed from the radial direction forms a part of an ellipse. In addition, the elliptical edge of the extension 44 has a common tangent with the peak 32a at two boundaries with the peak 32a. In other words, the peak 32a and the extension 44 are smoothly continuous with each other without steps or inflection points. The extension 54 is formed in the same manner as the extension 44. Although a detailed description is omitted, the extension 54 has a shape that is symmetrical to the extension 44 in the axial direction, and extends from the peak 34a along the bisector D2 toward the strut 30 to be connected by the link 70. As described above, the extensions 44, 54 can be regarded as portions of the peaks 32a, 34a extended along the respective bisectors D1, D2. Here, the extension 44 is an example of a first extension, and the extension 54 is an example of a second extension. Note that no extension is formed on the peaks 32, 34 other than the peaks 32a, 34a. In other words, the peaks 32a, 34a can be regarded as peaks having an elliptical outer edge and an arcuate inner edge, and being longer in the axial direction than the other peaks 32, 34. As shown in FIG. 2, the bridge portion 72 is a substantially rectangular portion formed between the first extension portion 44 and the second extension portion 54 when viewed from the radial direction (i.e., the R direction). The bridge portion 72 extends in a direction inclined with respect to the axial direction (i.e., the bisectors D1, D2). Specifically, the bridge portion 72 is formed along an extension direction extending from the peak portion 32a to the peak portion 34a. In this embodiment, the bridge portion 72 has a center line that is a virtual straight line (not shown) passing through the center of the ellipse that forms the outer edge of the extension portion 44 and the center of the ellipse that forms the outer edge of the extension portion 54. The bridging portion 72 has two edges 74 extending in the extension direction. One edge 74 reaches from near the top of the extension portion 44 to the portion of the extension portion 54 on the straight portion 36 side between the bisectors D1 and D2. The other edge 74 reaches from near the top of the extension portion 54 to the portion of the extension portion 44 on the straight portion 36 side between the bisectors D1 and D2.

[0037] The edge 74 of the bridge portion 72 has both ends formed in a curved shape, and the portion between the both ends is formed in a straight line parallel to the imaginary straight line. Specifically, when viewed from the radial direction, the end of the edge 74 on the apex side of the extension portion 44 or the apex side of the extension portion 54 forms a common tangent with the edge of the extension portion 44 or the edge of the extension portion 54 at the boundary with the vicinity of the apex of the extension portion 44 or the extension portion 54, respectively. Also, when viewed from the radial direction, the end of the edge 74 on the straight portion 36 side of the extension portion 44 or the straight portion 36 side of the extension portion 54 forms a common tangent with the edge of the extension portion 44 or the edge of the extension portion 54 at the boundary with the straight portion 36 side part of the extension portion 44 or the straight portion 36 side part of the extension portion 54, respectively. That is, one end of the edge 74 of the bridging portion 72 on the extension portion 44 side forms a common tangent with the edge of the extension portion 44 at the boundary with the extension portion 44 when viewed from the radial direction. In addition, the other end of the edge 74 of the bridging portion 72 on the extension portion 54 side forms a common tangent with the edge of the second extension portion 54 at the boundary with the second extension portion 54 when viewed from the radial direction.

[0038] In the stent 10 , the minimum width of the bridging portion 72 (that is, the width of the bridging portion 72 in a direction perpendicular to the above-mentioned inclination direction) is approximately equal to the minimum width of the straight portion 36 of the strut 30 .

[0039] (Cross-sectional structure of stent 10) The stent 10 has a cross section formed in a layered shape having a base layer 90 and a coating layer 92. Specifically, as shown in Figure 3, the wavy strut 30 has, in a cross section cut along an imaginary plane perpendicular to the direction along the wavy line, a base layer 90 located at the center of the cross section, and a coating layer 92 formed on the surface of the base layer 90. The same applies to the end struts 20, links 60, 70 and markers 80.

[0040] The base layer 90 is formed of a material containing a metal having shape memory properties, such as a nickel-titanium alloy. That is, the stent 10 is formed of a shape memory alloy. The shape of the stent 10 is formed, for example, by cutting out a tubular member having a cylindrical surface with a length L and a diameter D, which is formed of the above metal, by laser processing. The material forming the base layer 90 according to the present disclosure is not limited to the nickel-titanium alloy, and may contain metals such as iron, copper, titanium, nickel, cobalt, chromium, aluminum, zinc, manganese, tantalum, tungsten, platinum, and gold. In particular, the metal forming the base layer 90 preferably contains at least one selected from the group consisting of titanium, nickel, cobalt, chromium, tantalum, platinum, and gold. In addition, the material forming the base layer 90 may contain an alloy such as a cobalt-chromium alloy, a copper-aluminum-manganese alloy, a copper-zinc alloy, a nickel-aluminum alloy, or stainless steel. In particular, the metal forming the base layer 90 preferably contains a nickel-titanium alloy, a cobalt-chromium alloy, or stainless steel, among the alloys.

[0041] Furthermore, the material forming the base layer 90 according to the present disclosure is not limited to the above metals, and may include, for example, a polymer such as polyester or polycarbonate copolymer. Furthermore, the polymer forming the base layer 90 according to the present disclosure may include a biodegradable polymer having biodegradability, such as polylactic acid, polyhydroxybutyrate, polyglycolic acid, lactic acid-glycolic acid copolymer, polycaprolactone, lactic acid-caprolactone copolymer, glycolic acid-caprolactone copolymer, poly-γ-glutamic acid, collagen, or the like.

[0042] The base material layer 90 of the end struts 20 and 30 has a rectangular cross section, as shown in Figure 3. The thickness of the cross section in the R direction is thickness T. The minimum width in the width direction relative to the thickness T of the cross section is minimum width B. The thickness T of the base material layer 90 of the end struts 20 and 30 is in the range of 0.6 times or more the minimum width B and less than or equal to the minimum width B. As a specific example, the thickness T of the end struts 20 and 30 is 120 µm ± 10 µm, and the minimum width B of the end struts 20 and 30 is 150 µm ± 10 µm.

[0043] The end struts 20, struts 30, links 60, 70, and markers 80 are each formed so that the thickness in the R direction of the base material layer 90 is uniform, being a thickness T. In other words, the thickness in the R direction of the bridging portion 72 is equal to and uniform to the thicknesses in the R direction of the extension portions 44 and 54.

[0044] (Coating layer 92) The coating layer 92 includes a diamond-like carbon layer (DLC layer) 94 formed on the surface of the base layer 90 , and a drug-eluting coating layer 96 formed on the surface of the DLC layer 94 .

[0045] (DLC layer 94) The DLC layer 94 is made of diamond-like carbon containing fluorine (F) and silicon (Si). The DLC layer 94 is an example of a ceramic layer. The stent 10 includes the DLC layer 94, which is an example of a ceramic layer, in the coating layer 92, thereby suppressing the elution of metal ions constituting the stent and suppressing the biological reaction of the stent 10 to biological organs or blood. The DLC layer 94 includes F and Si, and thus has the conformability to stably follow the deformation of the stent 10 caused by the movement of the living body, and the flexibility to flexibly deform in response to various stresses when following. Furthermore, the DLC layer 94 includes F, and thus has antithrombotic properties. The ceramic layer according to the present disclosure is not limited to the DLC layer 94, as long as it is composed of a metal oxide layer, a metal nitride layer, a Si layer, or a carbon layer. The metal oxide layer or metal nitride layer according to the present disclosure preferably contains titanium, nickel, cobalt, chromium, aluminum, zinc, manganese, tantalum, or the like. The Si layer according to the present disclosure preferably contains silicon carbide or silicon dioxide. The carbon layer according to the present disclosure preferably contains diamond-like carbon or graphene.

[0046] The DLC layer 94 may be a layer formed by any method as long as it contains F and Si. The DLC layer 94 can be formed by utilizing a known method such as a vapor deposition method or a sputtering method. In particular, the DLC layer 94 is preferably formed by an ion vapor deposition method. Furthermore, the DLC layer 94 is more preferably formed by a chemical vapor deposition method (CVD method) or a physical vapor deposition method (PVD method). The DLC layer 94 formed by the CVD method or the PVD method is less likely to peel off from the stent 10 according to the present disclosure compared to a configuration formed by a method other than the CVD method or the PVD method. The details of the CVD method and the PVD method are described below.

[0047] Examples of the CVD method include plasma enhanced chemical vapor deposition (PE-CVD method) and thermal chemical vapor deposition. Thin films containing F, Si, and C can be formed by thin film synthesis using the PE-CVD method.

[0048] The PE-CVD method is a type of chemical vapor deposition (CVD) method that uses gas as the raw material, in which the raw material gas is introduced into a vacuum chamber and plasma is generated to cause a chemical reaction to deposit a film. The CVD method is a general term for methods that use chemical reactions to deposit a film on a substrate.

[0049] Heat, plasma, laser, etc. are used as energy sources for chemical reactions. In the CVD method, gas is used as the raw material. Therefore, the quality of the film that can be formed can be freely changed by selecting the raw material gas, and various elements can be added as desired.

[0050] In the PE-CVD method, a hydrocarbon gas or a gas containing the element to be added is flowed as a raw material gas into a vacuum chamber, and plasma is generated to cause a chemical reaction to deposit a film. DC power, high frequency, microwaves, and other AC power are preferably used to generate the plasma. The PE-CVD method uses plasma to make it possible to react highly activated chemical species, and the reaction can be carried out at a low temperature.

[0051] The DLC layer in the present disclosure can be formed using an inductively coupled plasma chemical vapor deposition (ICP-CVD) apparatus using high frequency waves. As the ICP-CVD apparatus, for example, YH-100NX manufactured by Onward Giken Co., Ltd. can be used. In an ICP-CVD device, a plasma is generated between ring-shaped electrodes by high-frequency discharge, and a bias voltage is applied to a jig on which a substrate is placed, which causes the ionized or excited chemical species to be adsorbed and a film is deposited. As film formation conditions, parameters such as processing time, high-frequency output, bias voltage, source gas flow rate, high-frequency pulse amplitude, bias pulse amplitude, high-frequency voltage at the time of plasma ignition, bias voltage, and source gas flow rate can be controlled.

[0052] Examples of the PVD method include a plasma ion implantation method, a vacuum deposition method, and a sputtering method.

[0053] As the raw material, a mixed raw material obtained by mixing a silane compound and a fluorine-containing aliphatic hydrocarbon is used.

[0054] The silane compound is preferably a carbon-containing organosilicon compound, such as the compound represented by the following formula S: SiR x H 4-x :Formula S In formula S, R represents an alkyl group having 1 to 4 carbon atoms, and x represents an integer of 1 to 4.

[0055] Examples of the compound represented by formula S include tetramethylsilane, tetraethylsilane, trimethylsilane, diethylsilane, methyldiethylsilane, and diethyldimethylsilane.

[0056] The fluorine-containing aliphatic hydrocarbon is preferably a fluorine-containing aliphatic hydrocarbon having 1 to 4 carbon atoms, and more preferably a perfluorohydrocarbon having 1 to 4 carbon atoms. Examples of the fluorine-containing aliphatic hydrocarbon include tetrafluoromethane (CF4), hexafluoroethane (C2F6), octafluoropropane, and perfluorobutane (C4F 10 ) etc.

[0057] Hydrocarbons may also be used as the feedstock. In the case of the CVD method, as the hydrocarbon, a saturated hydrocarbon (for example, methane (CH4), ethane (C2H6), etc.), an unsaturated hydrocarbon (for example, acetylene (C2H2), benzene (C6H6), etc.), etc. can be used. In the case of the PVD method, solid carbon can be used as the hydrocarbon.

[0058] In the DLC layer forming process, the silane compound is vaporized, and the vaporized silane compound and fluorinated aliphatic hydrocarbon (unsaturated hydrocarbon may be added) are introduced into the chamber to form a film. At this time, it is preferable to control and gradually change the partial pressure of the silane compound and the fluorinated aliphatic hydrocarbon. The mixed raw material of the silane compound and the fluorinated aliphatic hydrocarbon can be formed by mixing the silane compound and the fluorinated aliphatic hydrocarbon at an arbitrary ratio to form the DLC layer in the present disclosure. For example, it can be performed as follows. That is, a silane compound and a fluorine-containing aliphatic hydrocarbon are first supplied to the surface of a metal layer at a mixing ratio of the silane compound ≧ the mixing ratio of the fluorine-containing aliphatic hydrocarbon, and are adsorbed and deposited. At the start of film formation, only the silane compound may be used without using the mixed material. Subsequently, the mixing ratio of the silane compound is decreased (preferably gradually decreased) and the mixing ratio of the fluorine-containing aliphatic hydrocarbon is increased (preferably gradually increased) to continuously form a film by adsorption and deposition.

[0059] From the viewpoint of the use of the stent 10, the thickness of the DLC layer 94 is preferably thin, for example, in the range of 10 nm or more and less than 1000 nm, more preferably in the range of 100 nm to 500 nm, and further preferably in the range of 150 nm to 250 nm.

[0060] (Drug-eluting coating layer) The drug-eluting coating layer 96 is a polymer formed in a layer on the surface of the DLC layer 94, and has a function of being able to store a drug therein. The drug-eluting coating layer 96 has a function of eluting the stored drug when the stent 10 is placed in a biological organ having a tubular structure such as a blood vessel. The method of storing the drug in the drug-eluting coating layer 96 according to the present disclosure is not particularly limited, and a known method can be used. For example, the drug-eluting coating layer 96 according to the present disclosure may apply a method of storing a drug or a biodegradable polymer containing a drug in grooves or holes formed in the drug-eluting coating layer 96 as a method of storing a drug. In addition, the drug-eluting coating layer 96 according to the present disclosure may apply a method of forming the drug-eluting coating layer 96 with a biodegradable polymer containing a drug and having biodegradability or a drug as a method of storing a drug. The polymer forming the drug-eluting coating layer 96 may include silicone rubber, urethane rubber, fluororesin, polybutyl acrylate, polybutyl methacrylate, acrylic rubber, natural rubber, ethylene-vinyl acetate copolymer, styrene-butadiene block copolymer, styrene-isoprene block copolymer, styrene-isobutylene block copolymer, etc. Furthermore, the biodegradable polymer forming the drug-eluting coating layer 96 may include polylactic acid, poly-β-hydroxybutyric acid, polyglycolic acid, lactic acid-glycolic acid copolymer, polycaprolactone, lactic acid-caprolactone copolymer, glycolic acid-caprolactone copolymer, poly-γ-glutamic acid, glycolic acid-trimethylene carbonate copolymer, etc.

[0061] From the viewpoint of the use of the stent 10, the thickness of the drug-eluting coating layer 96 is preferably thin, for example, in the range of 1 μm or more and less than 20 μm, and more preferably in the range of 1 μm or more and less than 10 μm.

[0062] <Action and Effects> Next, the operation and effects of the present disclosure will be described. In this description, when describing a comparative embodiment of the present embodiment, the same components as those of the stent 10 of the embodiment will be described using the same reference numerals and names as they are. When the stent 10 is placed in a biological organ having a tubular structure such as a blood vessel (hereinafter, the example of "blood vessel" will be described), the stent 10 in a contracted state is set in an indwelling device such as a delivery catheter. When the stent 10 is ejected from the indwelling device at a predetermined position in the blood vessel, it expands in diameter in the blood vessel and adheres closely to the inner wall of the blood vessel, and is placed in the blood vessel. The stent 10 made of a shape memory alloy has good ability to follow the deformation of the blood vessel. A drug is eluted from the drug-eluting coating layer 96 of the stent 10 placed in the blood vessel.

[0063] Here, in the stent 10 of the embodiment, the link 70 connecting the crest 32a of one strut 30 to the crest 34a of the other strut 30 of two axially adjacent struts 30 is configured to include an extension 44, an extension 54, and a bridging portion 72. The stent 10 of the embodiment will be compared with a stent 110 of a comparative embodiment shown below.

[0064] 4, the stent 110 of the comparative embodiment does not have the extensions 44, 54 of the stent 10 of the embodiment. In addition, in the stent 110, the peak 32a of one strut 130 and the peak 34a of the other strut 130 of two struts 130 adjacent to each other in the axial direction are integrally connected by a link 170. The link 170 is connected to the peak 32a of the strut 130 that is the connection target with respect to the bisector D1. 32a From the side part to the mountain part 32a In contrast, the link 170 extends toward the peak portion of the link to be connected to the bisector D2. 34a From the side part to the mountain part 34a3. That is, in the stent 110 of the comparative embodiment, the link 170 extends from one side of the bisector of each of the peaks 32a or 34a (that is, it is located only between the bisectors D1 and D2 in the circumferential direction). In addition, the edge portion 174 of the link 170 is formed in a straight line at both ends. That is, when viewed from the radial direction, the edge portion 174 of the link 170 does not form a common tangent with the edge of the peak portion 32a at the boundary with the peak portion 32a at one end on the peak portion 32a side. In addition, when viewed from the radial direction, the edge portion 174 of the link 170 does not form a common tangent with the edge of the peak portion 34a at the boundary with the peak portion 34a at the other end on the peak portion 34a side. Other than the above, the stent 110 of the comparative embodiment has the same configuration as the stent 10 of the embodiment.

[0065] In the comparative stent 110, the links 170 extend from one side of the bisector of the peaks 32a or 34a, and therefore stress is likely to concentrate on the links 170 and their surrounding areas as the stent transitions from one of the contracted or expanded states to the other. In particular, in a stent in which the circumferential position of the peaks 32a of one strut 130 is offset from the peaks 34a of the other strut 130, the comparative stent 110 is likely to have stress concentrate on the links 170 and their surrounding areas. This stress concentration may deteriorate the shape precision of the stent 110 after it is expanded.

[0066] On the other hand, in the stent 10 of the embodiment, the extensions 44, 54 of one strut 30 are arranged on both sides of the bisector D1, D2 that bisects the peaks 32a, 34a toward the other strut 30. 、D24. The stent 10 of the embodiment has the extensions 44, 54 bridged over the bridge portion 72. As a result, in the stent 10 of the embodiment, stress is less likely to concentrate on the links 70 and their surrounding areas when the stent 10 transitions from the contracted or expanded state to the expanded or contracted state, compared to the stent 110 of the comparative embodiment. Therefore, in the stent 10 of the embodiment, in which the crest 32a of one strut 30 is misaligned in the circumferential direction with respect to the crest 34a of the other strut 30, the shape precision of the stent 10 after expansion is improved, compared to the stent 110 of the comparative embodiment.

[0067] Furthermore, the stent 10 of the embodiment has a configuration in which the thickness of the bridging portion 72 is equal to and uniform with the thickness of the extension portion 44 and the extension portion 54. As a result, in the stent 10 of the embodiment, stress is less likely to concentrate on the link 70 and its surrounding areas compared to a configuration in which the thickness of the bridging portion 72 is smaller than the thickness of the extension portion 44 or the extension portion 54. Therefore, in the stent 10 of the embodiment, the shape precision of the stent 10 is improved compared to a configuration in which the thickness of the bridging portion 72 is smaller than the thickness of the extension portion 44 or the extension portion 54.

[0068] In addition, the stent 10 of the embodiment has a configuration in which the extension portion 44 is elliptical with the bisector D1 as the major axis, and the extension portion 54 is elliptical with the bisector D2 as the major axis. As a result, the stent 10 of the embodiment is less susceptible to stress concentration on the link 70 and its surrounding areas compared to a configuration in which the extension portions 44, 54 extend in the axial direction in a rectangular shape as viewed from the radial direction. Therefore, the stent 10 of the embodiment has improved shape accuracy of the stent 10 compared to a configuration in which the extension portions 44, 54 are rectangular as viewed from the radial direction.

[0069] In addition, the stent 10 of the embodiment has a configuration in which one end of the edge 74 of the bridging portion 72 on the extension portion 44 side forms a common tangent with the edge of the extension portion 44 at the boundary with the extension portion 44 when viewed from the radial direction. In addition, the stent 10 of the embodiment has a configuration in which the other end of the edge 74 of the bridging portion 72 on the extension portion 54 side forms a common tangent with the edge of the extension portion 54 at the boundary with the extension portion 54 when viewed from the radial direction. As a result, in the stent 10 of the embodiment, stress is less likely to concentrate on the link 70 and its surrounding areas compared to a configuration in which the edge 74 of the bridging portion 72 is linear. Therefore, in the stent 10 of the embodiment, the shape precision of the stent 10 is improved compared to a configuration in which the edge 74 of the bridging portion 72 is linear.

[0070] Moreover, the stent 10 of the embodiment is formed of a shape memory alloy. Therefore, the stent 10 of the embodiment is a stent formed of a shape memory alloy, and the shape precision of the stent 10 is improved compared to the stent 110 of the comparative embodiment.

[0071] Moreover, the stent 10 of the embodiment has a coating layer 92 on its surface. The stent 10 of the embodiment has improved shape accuracy compared to the comparative stent 110, and therefore the coating layer 92 is less likely to be distorted. Therefore, the coating layer 92 of the stent 10 of the embodiment is less likely to peel off due to distortion of the stent 10 compared to the comparative stent 110.

[0072] Furthermore, in the stent 10 of the embodiment, the coating layer 92 includes a DLC layer 94 containing fluorine and silicon. As a result, the DLC layer 94 of the stent 10 of the embodiment is less likely to peel off due to distortion of the stent 10 compared to the comparative stent 110. Therefore, the stent 10 of the embodiment is less susceptible to deterioration over time than the comparative stent 110.

[0073] Furthermore, in the stent 10 of the embodiment, the coating layer 92 includes a drug-eluting coating layer 96. As a result, the drug-eluting coating layer 96 of the stent 10 of the embodiment is less likely to peel off due to distortion of the stent 10 compared to the comparative stent 110. Therefore, the drug-eluting effect of the stent 10 of the embodiment lasts for a longer period of time compared to the comparative stent 110.

[0074] In addition, in the stent 10 of the embodiment, the thickness T of the strut 30 is in the range of 0.6 times or more and B or less than the minimum width B of the strut 30. Therefore, the stent 10 of the embodiment has a larger inner diameter than a configuration having the same outer diameter as the stent 10 that is substantially cylindrical and the thickness of the strut 30 exceeds the minimum width B of the strut 30. Therefore, when the stent 10 of the embodiment is placed inside a blood vessel, it protrudes less into the lumen of the blood vessel and has a smaller effect on the blood flow of the blood vessel than a configuration having the same outer diameter as the stent 10 and the thickness of the strut 30 exceeds the minimum width B of the strut 30. As a result, the stent 10 of the embodiment can suppress poor blood circulation in the blood vessel compared to a configuration having the same outer diameter as the stent 10 and the thickness of the strut 30 exceeds the minimum width B of the strut 30. Furthermore, the stent 10 of the embodiment has a greater thickness than a configuration in which the thickness of the struts 30 is less than 0.6 times the minimum width B of the struts 30, making the stent 10 less susceptible to distortion. Therefore, the stent 10 of the embodiment has improved shape accuracy compared to a configuration in which the thickness of the struts 30 is less than 0.6 times the minimum width B of the struts 30.

[0075] As described above, a specific embodiment has been described in detail, but the present disclosure is not limited to the above embodiment, and various modifications, changes, and improvements are possible within the scope of the technical idea of ​​the present disclosure.

[0076] For example, in the stent 10 of the embodiment, the edge of the straight portion 26 of the end strut 20 forms a common tangent to the edges of two peaks that sandwich the center line CT of the wave of the end strut 20 in the axial direction. However, the straight portion 26 of the end strut 20 according to the present disclosure is not limited to this. For example, as shown in Figures 5 and 6, the straight portion according to the present disclosure may have a configuration in which it extends from one end of the arc-shaped peaks 232, 234 with a central angle exceeding 180° along the wavy line of the stent toward the peak on the opposite side to the peak with respect to the center line of the wavy line. Even in this configuration, it is desirable that the pair of straight portions 36 connected to one peak 232, 234 narrow the distance from each other as they move away from one peak in the reduced diameter state (the angle α is negative).

[0077] In addition, the stent 10 of the embodiment has a bridging portion 72 that is formed between the extension portion 44 and the extension portion 54 and has a substantially rectangular shape when viewed from the radial direction. However, the bridging portion 72 according to the present disclosure is not limited to this. For example, the bridging portion according to the present disclosure may have a configuration in which it is bridged between a first extension portion extending from a first crest and a second extension portion extending from a second crest so as to contact each other. A stent 210, which is an example of a stent having a bridging portion having a configuration in which it is bridged between a first extension portion extending from a first crest and a second extension portion extending from a second crest so as to contact each other, will be described below. 6, the stent 210 has an extension 244 extending in an elliptical shape along the axial direction from the peak 232a of one strut 230. The stent 210 also has an extension 254 extending in an elliptical shape along the axial direction from the peak 234a of the other strut 230 so as to contact the extension 244. The stent 210 also has bridging portions 272 that bridge the extension 244 and the extension 254 on both sides of the contact portion between the extension 244 and the extension 254.

[0078] Moreover, the stent 10 of the embodiment has a coating layer 92 on its surface, which includes a DLC layer 94 and a drug-eluting coating layer 96. However, the coating layer 92 according to the present disclosure may have only either the DLC layer 94 or the drug-eluting coating layer 96. Moreover, the stent 10 according to the present disclosure may not have a coating layer 92.

[0079] In addition, the extensions 44, 54 in the embodiment are elliptical. However, the extensions 44, 54 according to the present disclosure may have a shape other than elliptical. For example, the extensions 44, 54 according to the present disclosure may be formed in a parabolic shape or an isosceles triangle shape. Furthermore, the extensions 44, 54 according to the present disclosure may be formed in an isosceles trapezoid shape.

[0080] Furthermore, the struts 30 of the embodiment are configured such that two struts 30 adjacent to each other in the axial direction are arranged such that the wave phases in the circumferential direction are shifted. However, the struts 30 according to the present disclosure may be arranged side by side in the axial direction such that the wave phases in the circumferential direction of each strut are the same, as shown in Fig. 9. In this case, the peaks 32a and 34a connected by the link 70 are positioned with a shift of half the wavelength of the waves in the two adjacent struts 30, and one peak is convex toward the other side.

[0081] Furthermore, the strut 30 of the embodiment has nine peaks each of 32 and 34. However, the number of peaks of the strut of the stent according to the present disclosure is not particularly limited, and can be set according to the size of the biological organ having a luminal structure in which the stent is to be placed.

[0082] In addition, in the embodiment, two adjacent struts 30 are connected by three links 70 arranged at equal intervals in the circumferential direction. However, the arrangement and number of links according to the present disclosure are not particularly limited, and can be set according to the size of a biological organ having a tubular structure in which a stent is to be placed.

Claims

1. A first strut is arranged along a cylindrical surface and has a wave shape with an amplitude direction in an axial direction of the cylindrical surface; a second strut that is disposed along the cylindrical surface, that is wavy with an amplitude direction in the axial direction, and that is adjacent to the first strut in the axial direction; a first extension portion formed on a first peak portion which is a portion of a plurality of peak portions of the first strut that are convex toward the second strut side, the first extension portion extending from both sides of a first bisector that bisects the first peak portion toward the second strut side along the first bisector; a second extension portion formed on a second peak portion of the second strut that is shifted in the circumferential direction from the first peak portion among a plurality of peak portions of the second strut that are convex toward the first strut side, the second extension portion extending from both sides of a second bisector that bisects the second peak portion toward the first strut side along the second bisector; a bridge portion spanning the first extension portion and the second extension portion; having The first extension portion and the second extension portion between which the bridging portion is bridged are disposed at an interval in the axial direction, A stent, wherein the bridging portion extends in a direction inclined with respect to the first bisector and is formed along an extension direction extending from the first peak portion to the second peak portion.

2. The stent according to claim 1 , wherein the thickness of the bridging portion is equal to and uniform with the thickness of the first extension portion or the second extension portion.

3. The first extension portion has an elliptical shape with the first bisector as a major axis, The stent according to claim 1 or 2, wherein the second extension portion has an elliptical shape with the second bisector as its major axis.

4. A stent as described in any one of claims 1 to 3, wherein, when viewed from the radial direction of the cylindrical surface, one end of the edge of the bridging portion on the side of the first extension portion is curved to form a common tangent with the edge of the first extension portion at the boundary with the first extension portion, and the other end of the edge of the bridging portion on the side of the second extension portion is curved to form a common tangent with the edge of the second extension portion at the boundary with the second extension portion.

5. A first strut arranged along a cylindrical surface and forming a wave shape with an amplitude direction in the axial direction of the cylindrical surface; a second strut that is disposed along the cylindrical surface, that is wavy with an amplitude direction in the axial direction, and that is adjacent to the first strut in the axial direction; a first extension portion formed on a first peak portion which is a portion of a plurality of peak portions of the first strut that are convex toward the second strut side, the first extension portion extending from both sides of a first bisector that bisects the first peak portion toward the second strut side along the first bisector; a second extension portion formed on a second peak portion of the second strut that is shifted in the circumferential direction from the first peak portion among a plurality of peak portions of the second strut that are convex toward the first strut side, the second extension portion extending from both sides of a second bisector that bisects the second peak portion toward the first strut side along the second bisector; a bridge portion spanning the first extension portion and the second extension portion; having the first extension portion extends from the first peak portion in an elliptical shape along the axial direction, and the second extension portion extends from the second peak portion in an elliptical shape along the axial direction to have a contact portion that contacts the first extension portion, A stent, wherein the bridging portion spans both sides of the contact portion.

6. The stent according to any one of claims 1 to 5, which is formed from a shape memory alloy.

7. The stent according to any one of claims 1 to 6, which has a coating layer on its surface.

8. The stent of claim 7 , wherein the coating layer comprises a ceramic layer.

9. The stent of claim 7 or claim 8, wherein the coating layer comprises a drug-eluting coating layer.

10. 10. The stent according to claim 1, wherein a thickness of the first strut and the second strut is in a range of 0.6 times or more and not more than a minimum width B of the first strut and the second strut in the direction along the cylindrical surface.

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