KR101976074B1 - Method for manufacturing biodegradable stent - Google Patents

Abstract

The present invention relates to a biodegradable stent and a method for manufacturing the biodegradable stent. The biodegradable stent is manufactured by bending a wire containing magnesium to produce a body of the stent; And a stress removing step of reducing a bending stress generated at a bending portion of the wire for the stent, so that even if the wire of magnesium is bent, the wire is not easily broken, The technology that enables the manufacture of magnesium stents and the manufacturing process is simplified compared to the existing laser cutting stent manufacturing process.
According to the present invention, mechanical strength is superior to other biocompatible polymers and biodegradable polymers, and since the stent according to the present invention is naturally biodegraded and absorbed after a certain period of time in the body, it contributes to maintaining a constant magnesium concentration in the body .
In addition, the present invention has an effect that the mechanical properties of the stent body can be changed by various changes as needed, and the manufacturing process is simplified compared to the conventional laser cutting stent manufacturing method.

Description

[0001] METHOD FOR MANUFACTURING BIODEGRADABLE STENT [0002]

The present invention relates to a biodegradable stent and a method of manufacturing the same.

Generally, a stent is a medical device that is inserted into a stenotic region in the body to expand the stenosed lumen. Conventional stents made of metallic materials have sufficient mechanical strength to prevent stenosis, but they can cause a foreign body sensation during the period of stay in the patient's body and cause inflammation or restenosis in the stenotic area.

In recent years, biodegradable stent technology, which is decomposed naturally when a certain period of time elapses in the body, has been developed to solve the problems of the conventional metallic stent. For example, Korean Patent Laid-Open Publication No. 2017-0019803 discloses biodegradable stent technology.

Meanwhile, commercially available biodegradable stent products can be divided into several product groups depending on the type of biodegradable polymer forming the scaffold of the stent. Among them, a stent made of magnesium has better mechanical properties than other polymers, and magnesium is absorbed as a beneficial mineral in the body when it is biodegraded in the body.

However, when manufacturing a stent made of magnesium by bending the wire to make the body of the stent, the brittleness of magnesium itself is large, so that the wire may be easily broken during bending of the wire, did.

Conventionally, in order to manufacture a magnesium stent, a magnesium material is first prepared in the form of a tube having a predetermined diameter, and then the surface of the tube is subjected to laser cutting to form a laser cutting type Stent S was prepared.

However, since the conventional laser cutting type stent manufacturing method irradiates a high temperature laser to the surface of a tube, a burr occurs on the surface of the stent during laser processing, and burrs cause inflammation and restenosis in the body It is necessary to perform a post-treatment step such as a surface treatment using a chemical agent or an electrolytic polishing step in order to remove burrs.

It is an object of the present invention to provide a technique for manufacturing a magnesium stent by bending since a wire is not easily broken even when a magnesium wire is bent.

Another object of the present invention is to provide a technique in which the manufacturing process is simplified compared to the conventional laser cutting stent manufacturing process.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an apparatus and method for controlling the same.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, a method of manufacturing a biodegradable stent includes bodily manufacturing a stent body by bending a magnesium-containing wire; And a stress removing step of reducing a bending stress generated at a bending portion of the wire for the stent.

The method of manufacturing a biodegradable stent further includes a step of preparing a wire for the stent before the step of manufacturing the body. In the step of preparing the material, the magnesium alloy is heat-treated at 250 to 300 ° C, A wire drawing process can be performed.

In addition, the biodegradable stent manufacturing method may further include a wire coating step of coating the surface of the stent wire, and the biodegradable polymer coating layer may be formed on the surface of the wire in the wire coating step.

In the body manufacturing step, the body may be formed by bending the wire for stent at the outer circumferential surface of the jig provided with the detachable projecting pin.

In addition, in the stress removing step, the body may be heat-treated at 250 to 300 ° C to prevent breakage of the wire for stent by residual stress.

In the stress relieving step, the body is heat-treated in a state of being coupled with the jig, and the heat treatment time can be set at a rate of 0.5 to 2 minutes per 1 mm of the diameter of the jig.

According to another aspect of the present invention, there is provided a stent produced by the above-described manufacturing method, comprising: a body having a plurality of peak portions and a valley portion formed by bending a stent wire a plurality of times; And the valley portion are hooked and connected to each other in the form of a ring, and the wire for the stent may contain magnesium.

Further, a biodegradable polymer coating layer may be formed on the surface of the stent wire.

The solution of the above-mentioned problems is merely illustrative and should not be construed as limiting the present invention. In addition to the exemplary embodiments described above, there may be additional embodiments described in the drawings and the detailed description of the invention.

As described above, the present invention has the following effects.

First, the stent according to the present invention is made of a magnesium material and has excellent mechanical strength as compared with other biocompatible polymers and biodegradable polymers.

Secondly, since the stent according to the present invention is biodegraded and absorbed naturally after a certain period of time in the body, the stent contributes to maintaining the concentration of magnesium in the body constant.

Thirdly, since the wire is not easily broken during the process of bending the magnesium-containing wire, it is possible to manufacture the body of the stent by bending the wire, and the workability is improved.

Further, the present invention has an effect that it is possible to manufacture the stent by varying the mechanical properties of the body of the stent by varying the number of bending times in manufacturing the stent.

Fourth, since a stent can be manufactured without using a laser processing method in manufacturing a magnesium stent, burrs on the surface of the stent are not generated by the laser.

In addition, since the post-treatment process for removing burrs can be omitted, the present invention has the effect of simplifying the manufacturing process compared to the conventional laser cutting stent manufacturing method.

The effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the description of the claims.

FIG. 1 schematically shows an example of a conventional laser cutting type stent.
2 is a flowchart illustrating a method of manufacturing a biodegradable stent according to an embodiment of the present invention.
Figure 3 illustrates a biodegradable stent made in accordance with an embodiment of the present invention.
4 schematically shows a structure of a jig used in an embodiment of the present invention.
5 is a schematic view illustrating a stent being manufactured in a jig according to an embodiment of the present invention.
FIG. 6 shows the results of evaluating the mechanical properties of the biodegradable stent according to an embodiment of the present invention.
7 is a photograph of a surface of a biodegradable stent without a stress removal step taken by a scanning electron microscope as a comparative example.
FIG. 8 is a photograph of a surface of a biodegradable stent manufactured according to an embodiment of the present invention, taken with a scanning electron microscope.

The preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings, in which the technical parts already known will be omitted or compressed for simplicity of explanation.

A method of manufacturing a biodegradable stent according to an embodiment of the present invention will be described with reference to the flowchart shown in FIG. 2 and will be described with reference to the drawings shown in FIGS. 3 to 8 for convenience.

1. Material preparation step <S101>

In this step, a process of preparing the wire W for the stent may be performed. In one embodiment, this step can be subdivided into a heat treatment step of heat-treating the magnesium alloy, which is a material of the biodegradable stent, at a predetermined temperature, and a fresh working step after the heat treatment step.

The magnesium alloy used in one embodiment comprises 2.7 wt% aluminum, 0.8 wt% zinc, 0.4 wt% manganese, 0.09 wt% silicon, 0.004 wt% copper, 0.01 wt% iron, 0.01 wt% calcium, 0.002 wt% nickel, 1.9% by weight of neodymium, 2.5% by weight of neodymium, 1.0% by weight of zirconium, 4.3% by weight of yttrium, magnesium of the balance and other inevitable impurities. However, Other metal components may be added.

In the heat treatment process according to an embodiment, the magnesium alloy ingot may be put into a heating furnace and heat-treated at 250 to 300 ° C for a predetermined time. If the magnesium alloy is subjected to a heat treatment at a temperature of less than 250 占 폚 during the heat treatment process, it is difficult to secure the strength of the magnesium alloy, and the reduction of the inherent brittleness of the magnesium alloy is limited.

In addition, when the magnesium alloy is heat-treated at a temperature higher than 300 ° C, the metal elements in the magnesium alloy may be activated and oxidized, and a carbonized layer may be formed on the surface of the magnesium alloy to cause deformation of the magnesium alloy. .

In one embodiment, the magnesium alloy may be heat treated for 1 to 10 hours, but the heat treatment time may vary depending on the type and content of the metal component of the magnesium alloy.

Further, after the heat treatment process is performed for a predetermined time, the magnesium alloy can be cooled as it is in the heated furnace. That is, the magnesium alloy may be softened by furnace cooling in which the heated material is gradually cooled in the furnace to reduce the brittleness.

After the heat treatment process is completed, the magnesium alloy can be deformed into a wire W for stent through a wire drawing process. For example, by putting a magnesium alloy, which is a base material with reduced brittleness by a heat treatment process, on a drawing die and slowly pulling out one end of the magnesium alloy that has passed through the hole of the drawing die, Can be manufactured.

Generally, since the diameter of the wire constituting the stent has a diameter ranging from millimeter to micrometer, it is possible to manufacture a fine diameter wire such as a micrometer unit through the drawing process of one embodiment.

However, in the case of a method of processing a magnesium alloy as a base material in the form of a wire suitable for manufacturing a stent, in the case of an extrusion method in which a base material is pushed out at a high pressure or a rolling method using a roller, Is difficult.

For example, in the extrusion method, since a large pressure is required to push out the base material inside the die, the smaller the die hole is, the more the pressure pushing the base material outward is increased, Since the rolling method is a process of pressing the base material while passing the base material through the roller, it is not structurally suitable for making the length of the base material long or making it in the form of a wire.

Therefore, in one embodiment, it is preferable to apply a drawing process rather than a rolling or extrusion process to draw the magnesium alloy, which is a base material, in the form of a wire having a small diameter, and the diameter of the wire to be manufactured during the drawing process depends on the size of the stent And the like.

2. Body Manufacturing Step < S102 >

In this step, a process of manufacturing the stent body 100 by bending the wire W for stent containing magnesium may be performed. 4 schematically shows a structure of a jig 20 used in an embodiment of the present invention. 4, the jig 20 may include a plurality of protruding pins 21, 22, 23, 24 and a jig hole H. The wire W for stent may include a plurality of protruding pins 21, 22, 23, 24) as a starting point.

FIG. 5 is a schematic view of a stent being manufactured in the jig 20 according to an embodiment of the present invention. Referring to FIG. 5, in one embodiment, the stent body 100 may be formed by bending the wire W for stent at the outer circumferential surface of the jig 20 provided with the detachable projecting pin.

Specifically, in this step, the jig 20 provided with at least one projecting pin is used, and the stent wire W is passed through the jig 20 (Intersecting each other) or interwoven between the wires while bending and moving in the longitudinal direction of the wire (i.e., a space surrounded by the cell and the wire).

For example, the stent wire W is folded from the protruding pin 24 to form the peak portion 120 and the valley portion 150, and the formed peak portion 120 and the valley portion 150 are formed in a ring shape So that the body 100 of the stent 10 can be formed.

As a result, the stent wire W manufactured in step S101 constitutes the body 100 of the stent 10 as shown in FIG. 3 through this step. In the body 100 of the stent 10 manufactured in this step, there are a plurality of peak portions 110, 120 and 130 and valleys 140, 150 and 160 formed by bending the stent wire W a plurality of times .

3. Wire coating step < S103 >

In this step, the surface of the stent wire W may be coated. In one embodiment, the biodegradable polymer coating layer 170 can be formed by coating the biodegradable polymer on the surface of the wire. If there is no coating on the surface of the wire, it may be difficult to demonstrate the nature of the stent in which magnesium wires are biodegraded rapidly in the body to expand the stenotic region.

Accordingly, in one embodiment, the biodegradable polymer coating layer 170 controls the decomposition rate of the magnesium-based wire, thereby maintaining the stent 10 in the body for a predetermined period of time.

In one embodiment, the biodegradable polymer may be applied to at least one or more selected from the group consisting of polycaprolactone, polylactic acid, polyglycolic acid, and mixtures thereof, but is not limited to the above- It is also possible to use a polymer type.

In addition, coating methods applicable in one embodiment include, but are not limited to, dip coating, ultrasonic spray coating, spin coating, vapor deposition, and the like, A coating layer may be formed using a method.

However, according to the embodiment of the present invention, it is possible to perform this step between the body preparing step (S102) and the body removing step (S104) Or after the stress relieving step (S104).

4. Stress removal step < S104 >

In this step, a process of reducing the bending stress occurring at the bending portion of the wire W for stent when the step S102 is performed can be performed.

If a bending moment is applied to the stent wire W through step S102, tensile stress is generated on one side of the wire and compressive stress is generated on the opposite side of the wire. That is, since the bending stress simultaneously generates tensile stress and compressive stress on the wire W for stent, the metal fatigue increases due to the generated stress, and when the external force is applied to the body 100 of the stent 10, It may break or break.

However, in this step, by removing the residual stress generated inside the wire W for stent by bending, the inherent brittleness of the magnesium alloy can be overcome and the durability of the stent 10 can be improved.

In this embodiment, the body 100 of the stent 10 may be thermally treated at 250 to 300 ° C to prevent damage to the stent wire W due to residual stress. If the heat treatment temperature is less than 250 ° C, the degree of decrease in the residual stress is insignificant, which may easily damage the wire. If the heat treatment temperature exceeds 300 ° C, the wire W for the stent is oxidized The durability of the stent 10 may be deteriorated, and therefore, it is preferable to be performed within the above-described range.

In particular, it is more preferable to apply a heat treatment temperature of 260 to 280 DEG C in view of reducing residual stress in the wire W for stent and preventing cutting and breakage of the magnesium wire.

The residual stress is generated in the body 100 of the stent 10 manufactured through step S102 due to the bending stress. Therefore, when the stent 10 is quickly removed from the jig 20, May be cut or broken.

Therefore, it is preferable to set the heat treatment time in consideration of the diameter of the jig 20, by putting the stent 10 into the heating furnace in a state of being coupled to the jig 20. [ In one embodiment, the heat treatment time can be set at a rate of 0.5 to 2 minutes per 1 mm of the diameter of the jig 20. [

If the heat treatment is performed for less than 0.5 minutes per 1 mm of the diameter of the jig 20, the heat transfer to the stent 10 is not smoothly performed, and the residual stress of the wire W for stent is reduced. ) When the heat treatment is performed for more than 2 minutes per 1 mm in diameter, the durability of the stent 10 may be lowered due to overheating of the wire W for stent.

For example, if the diameter of the jig 20 to which the stent 10 is fixed is 10 mm, the heat treatment can be performed for 5 minutes to 20 minutes. Here, the diameter of the jig 20 refers to the diameter of the center of the jig 20 with respect to the longitudinal direction of the jig 20, but the diameter of one end of the jig 20 may be applied in other embodiments .

On the other hand, after this step, a cooling step of lowering the temperature of the stent 10 can be further performed. A cooling method in which the stent 10 is gradually heated in the heating furnace or a quenching method in which the stent 10 is immersed in the cooling water for a short period of time can be applied in the cooling step or various known cooling methods can be applied.

3, the stent 10 manufactured according to the above-described embodiment includes a plurality of peak portions 110, 120, and 130 formed by bending a wire W for stent containing magnesium several times, The biodegradable polymer coating layer 170 may be formed on the surface of the wire W for stent.

6 is a graph showing a result of evaluating mechanical properties of a biodegradable stent according to an embodiment of the present invention. That is, the stent was pressed from the upper side to the lower side of the stent using a radial force meter, and the pressure until the diameter of the stent was reduced to half was measured and shown in FIG. Referring to FIG. 6, it can be seen that the biodegradable stent of magnesium has excellent mechanical properties as the diameter of the stent wire increases.

7 is a photograph of a biodegradable stent without a stress removal step taken by a scanning electron microscope (WD 15.0 mm, 15.0 kV) as a comparative example. FIG. 7A is a photograph of the bending portion of the stent wire at a magnification of 40 times, and FIG. 7B is a photograph of the bending portion of the wire for stent at a magnification of 100 times. Referring to FIG. 7, it can be seen that the bending portion of the wire for the stent is slightly cracked.

FIG. 8 is a photograph of a surface of a biodegradable stent manufactured according to an embodiment of the present invention, taken with a scanning electron microscope (WD 15.0 mm, 15.0 kV). 8 (a) is a photograph of a bending portion of a stent wire at a magnification of 40 times, and Fig. 8 (b) is a photograph of a bending portion of a stent wire at a magnification of 100 times. Referring to FIG. 8, it can be confirmed that no crack occurs in the bending portion of the wire for stent.

That is, since the bending stress generated in the bending portion of the wire for stent is removed through the stress removing step in Fig. 8, the brittleness of the wire for stent is reduced, so that the tensile force and flexibility of the wire for stent are increased as compared with the comparative example, It can be seen that the surface of the wire did not crack.

In the method of manufacturing a stent body by bending a magnesium-based wire, bending stress is generated on the wire during the bending process, so that the brittleness of the wire is increased and cracks may occur on the surface of the wire or the wire may be broken. Although the risk of breakage of the wire is increased when the diameter is enlarged, the present invention reduces the residual stress present in the wire for the stent, lowering the brittleness of the wire, and increasing the tensile force and flexibility. Therefore, the stent is bent by an external force, The crack does not occur even when it is expanded.

As a result, the stent according to the present invention is made of magnesium and has excellent mechanical strength as compared with other biocompatible polymers and biodegradable polymers. When the stent is biodegraded and absorbed naturally after a certain period of time in the body, the magnesium concentration in the body is kept constant There is an effect to contribute.

Further, since the wire is not easily broken during the process of bending the magnesium-containing wire, it is possible to manufacture the body of the stent by bending the wire, and the workability is improved.

Further, the present invention has an effect that it is possible to manufacture the stent by varying the mechanical properties of the body of the stent by varying the number of bending times in manufacturing the stent. For example, to manufacture a stent with a high mechanical strength, the radial force of the stent can be improved by increasing the number of bending of the stent.

In addition, since a stent can be manufactured without using a laser processing method in manufacturing a magnesium stent, burrs due to a laser do not occur on the surface of the stent. That is, since the post-treatment process for removing the bur can be omitted, the present invention has the effect of simplifying the manufacturing process compared to the conventional laser cutting stent manufacturing method.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. And the scope of the present invention should be understood as the scope of the following claims and their equivalents.

S: Conventional Laser Cutting Stent
10: stent
100: Body
110, 120, and 130:
140, 150, 160:
170: biodegradable polymer coating layer
W: Wire for stent
20: Jig
21, 22, 23, 24: projecting pin
H: Jig hole

Claims (8)

A body manufacturing step of bending a wire for a stent containing magnesium to produce a body of the stent; And
And a stress removing step of reducing bending stress generated at a bending portion of the wire for the stent,
In the body manufacturing step, the body is formed by bending the wire for stent at the outer circumferential surface of the jig provided with the detachable projecting pin,
Wherein the heat treatment time is set at a rate of 0.5 to 2 minutes per 1 mm of the diameter of the jig while the body is heat-treated in a state where the body is engaged with the jig.
A method for manufacturing a biodegradable stent. The method according to claim 1,
The biodegradable stent manufacturing method further includes preparing a wire for the stent before the body manufacturing step,
In the material preparation step, the magnesium alloy is heat-treated at a temperature of 250 to 300 ° C., and a drawing process is performed to transform the heat-treated magnesium alloy into a wire form
A method for manufacturing a biodegradable stent. 3. The method of claim 2,
The biodegradable stent manufacturing method further includes a wire coating step of coating a surface of the stent wire,
In the wire coating step, a biodegradable polymer coating layer is formed on the surface of the wire,
Wherein the wire coating step is performed between the body manufacturing step and the stress removing step, or between the material preparing step and the body manufacturing step, or after the stress removing step
A method for manufacturing a biodegradable stent. delete The method according to claim 1,
Wherein the body is subjected to heat treatment at 250 to 300 ° C to prevent breakage of the wire for stent due to residual stress in the stress relieving step
A method for manufacturing a biodegradable stent. delete delete delete

Images