Magnesium-PLA composite degradable intravascular stent and preparation method thereof

Abstract

The invention relates to a composite stent used in the field of vascular interventional therapy, in particular to a magnesium-PLA composite degradable intravascular stent and a preparation method thereof.The stent comprises a plurality of stent single rings and a plurality of inter-ring connecting pieces, the stent single rings are placed in a casting mold, and the inter-ring connecting pieces are placed in the casting mold; and the inter-ring connecting pieces are subjected to injection molding by means of a casting mold, so that the adjacent bracket single rings are connected by the inter-ring connecting pieces. The preparation method comprises the following steps: S1, laying the bracket and smearing the demolding powder; s2, injection molding is conducted; and S3, demolding. According to the invention, the stress concentration at the joint between the stent single ring and the inter-ring connecting piece in the stent compression and expansion process is reduced, and meanwhile, the PLA material has a longer degradation period compared with a magnesium alloy material, so that the condition that the inter-ring connecting part loses a supporting effect due to rapid degradation is avoided.

Description

Technical Field

[0001] The present application relates to a composite stent used in the field of vascular interventional treatment, and in particular to a magnesium-PLA composite degradable vascular stent and a preparation method thereof. Background Art

[0002] The incidence of cardiovascular disease has increased year by year and has become one of the three major diseases that endanger human life and health. Vascular stenosis is a common disease that causes serious consequences such as heart failure and stroke. For the treatment of cardiovascular and cerebrovascular stenosis, the existing treatment methods mainly include drugs, surgery and stent angioplasty. Among them, drugs can reduce the relative risk of ischemic stroke by 13%, but the treatment effect is not very obvious. The incidence of surgical complications is high and there is a certain degree of risk. Interventional treatment has become the most effective way to treat ischemic stroke in recent years because of its low trauma, good efficacy and high success rate, and is widely accepted by doctors and patients.

[0003] At present, there are many types of stents used clinically, but most of the stents are made of metals such as nickel-titanium alloy or cobalt-chromium alloy. These metal stents cannot be degraded in the body and will remain in the body after vascular reconstruction, which can easily cause intimal hyperplasia, inflammatory response, etc. In order to solve the limitations of traditional metal stents, the use of degradable vascular stents can well solve the above-mentioned problems of traditional metal stents. Magnesium alloys have become the preferred material for degradable stents because of their good mechanical properties, biocompatibility, and ability to effectively inhibit inflammation. Another preferred material is PLA (polylactic acid), which has biodegradability and biocompatibility and has a long degradation cycle.

[0004] However, the above two materials also have their own disadvantages. The vascular stent support effect of PLA material is poor, and problems such as stent breakage and incomplete expansion may occur during the compression and expansion process; magnesium alloy material has problems such as too fast degradation speed and stress concentration at the connection between rings during the expansion and compression process of the stent;

[0005] The configurations of related degradable vascular stents at home and abroad include: for example, patent (CN202321923510.7) discloses a magnesium alloy vascular stent, which arranges the single rings of the vascular stent in the same direction of the wave crests, and the inter-ring connectors are arranged on the side walls of the single rings of the stent, avoiding stress concentration at the crests and troughs, but the inter-ring connectors and the vascular stent are still an integral structure. During the expansion of the vascular stent, there is still stress concentration at the connection between the inter-ring connectors and the single rings of the vascular stent. The vascular stent with this structure may lose its supporting capacity during service due to the breakage of the inter-ring connectors.

[0006] Therefore, in order to ensure that the vascular stent has good supporting performance and that the connection between the single ring of the vascular stent and the connecting piece between the rings does not break during the process of opening the blood vessel, it is very necessary to invent a degradable vascular stent made of magnesium-PLA composite material. Summary of the invention

[0007] In order to solve the defect that the stress concentration at the inter-ring connection during the expansion of the existing magnesium alloy degradable vascular stent leads to the fracture of the inter-ring connection piece, the purpose of the present invention is to provide a magnesium-PLA composite degradable vascular stent and a preparation method to overcome the above defects. The inter-ring connection piece made of PLA material is used to replace the inter-ring connection piece of the traditional metal stent, which can effectively reduce compression and stress concentration. The forming process of the degradable vascular stent is completed by laser cutting and injection molding.

[0008] The present application provides a magnesium-PLA composite biodegradable vascular stent and a preparation method thereof using the following technical solutions:

[0009] On the one hand, the present invention provides a magnesium-PLA composite biodegradable vascular stent, which includes a plurality of stent single rings and a plurality of inter-ring connectors, wherein the stent single rings are placed in a casting mold, and the inter-ring connectors are injection molded by means of the casting mold so that the inter-ring connectors connect adjacent stent single rings; the inter-ring connectors are arranged circumferentially between each two adjacent stent single rings, and the phase angles of two adjacent inter-ring connectors in different layers differ by 30°, the thickness of the stent single ring is h1, the height of the connection of the inter-ring connector is h2, and the relationship between the thickness of the stent single ring and the height of the connection of the inter-ring connector is 2*h1. <h2。

[0010] Furthermore, the single ring of the bracket is made of magnesium alloy, and the connecting piece between the rings is made of PLA.

[0011] Furthermore, the single ring of the support is in surface contact with the inter-ring connecting piece, and the two can slide in the circumferential direction.

[0012] Furthermore, through holes are respectively provided at the upper and lower connecting parts of the inter-ring connecting member, and the through holes connect two adjacent single rings of the bracket.

[0013] Further, the casting mold includes an outer mold, a middle mold and an inner mold, the inner side wall of the outer mold is provided with a plurality of first grooves, the outer side wall of the inner mold is provided with a plurality of second grooves, the side wall of the middle mold is provided with a middle mold annular cavity and a plurality of rectangular through holes, the middle mold annular cavity is connected with the plurality of rectangular through holes, the first grooves, the second grooves and the rectangular through holes constitute an inter-ring connector cavity, and the inter-ring connector is injection molded in the inter-ring connector cavity;

[0014] An injection through hole is provided on the side wall of the outer layer mold; the injection through hole includes an outer runner injection hole, a runner cavity through hole and a molding liquid flow channel, the outer runner injection hole is provided on the outer side wall of the outer layer mold, and the outer runner injection hole is connected to the molding liquid flow channel; the molding liquid flow channel is arranged inside the outer mold, the runner cavity through hole is provided on the inner side wall of the outer layer mold, and the first end of the runner cavity through hole is connected to the molding liquid flow channel, and the second end of the runner cavity through hole is connected to the inter-ring connector cavity;

[0015] The inner layer mold is provided with an exhaust through hole, and the exhaust through hole is in communication with the cavity of the inter-ring connector.

[0016] Furthermore, the molding liquid flow channel is annular in shape and passes through the outer layer mold.

[0017] Furthermore, the outer runner injection hole is located on the side wall of the outer mold corresponding to the bottom end of the bottommost connector cavity; the exhaust hole is located on the side wall of the inner mold corresponding to the top end of the topmost connector cavity.

[0018] Furthermore, the middle-layer mold is provided with a middle-layer mold ring cavity, and the shape of the inner wall of the middle-layer mold ring cavity fits the outer contour of the single ring of the bracket.

[0019] On the other hand, the present invention provides a method for preparing a magnesium-PLA composite degradable vascular stent, the steps of which are as follows:

[0020] S1. After the stent single ring is expanded, it is sequentially inserted into the middle mold ring cavity in the middle mold, and the surface of the stent single ring where the inter-ring connector is required is coated with release powder;

[0021] S2. The outer mold is buckled with the middle mold, and the molten injection liquid is injected into the molding liquid flow channel through the outer runner injection hole, and injected into the middle mold ring cavity through the molding liquid flow channel and the flow channel mold cavity through hole to complete the injection molding;

[0022] S3. Demolding: dismantling the outer mold, trimming the excess parts formed in the molding liquid flow channel and the exhaust flow channel, and taking out the vascular stent after cooling.

[0023] In summary, this application includes the following beneficial technical effects:

[0024] A magnesium-PLA composite biodegradable vascular stent uses PLA material connectors to connect single rings of a magnesium alloy vascular stent, thereby avoiding stress concentration at the junction of a single ring of the stent and a connector during compression and expansion of the metal vascular stent.

[0025] The longer degradation cycle of the PLA material can extend the service life of the connectors between the single rings of the vascular stent, thereby avoiding the loss of the support function of the vascular stent due to degradation of the connectors and extending the service life.

[0026] A method for preparing a magnesium-PLA composite degradable vascular stent is provided. The vascular stent inter-ring connector is manufactured by precision injection molding. The vascular stent has a simple structure, a simple injection mold, and is convenient for loading and unloading and manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1a and Figure 1b This is a front view of the magnesium-PLA composite degradable vascular stent casting mold of the present invention;

[0028] Figure 2 For the present invention Figure 1b Schematic diagram of the AA section;

[0029] Figure 3 For the present invention Figure 2 Schematic diagram of the cross-section of the middle BB section;

[0030] Figure 4 It is a structural front view of the magnesium-PLA composite degradable vascular stent of the present invention;

[0031] Figure 5 It is a top view of the structure of the magnesium-PLA composite degradable vascular stent of the present invention;

[0032] Figure 6a It is a schematic diagram of the connection between a single stent ring and a segment connector of the metal vascular stent of the present invention;

[0033] Figure 6b It is a schematic diagram of the connection between a single ring of the stent and a segment connector of the magnesium-PLA composite degradable vascular stent of the present invention.

[0034] Description of reference numerals:

[0035] 1. Casting mold; 2. Bracket single ring; 3. Inter-ring connector; 111. Outer mold; 112. Middle mold; 113. Inner mold; 11. Outer runner injection hole; 12. Runner cavity through hole; 13. Molding liquid flow channel; 14. Middle mold ring cavity; 15. Inter-ring connector cavity. DETAILED DESCRIPTION

[0036] The exemplary embodiments, features and aspects of the present invention will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0037] like Figure 1a-Figure 6bAs shown, the present invention provides a magnesium-PLA composite biodegradable vascular stent, which includes a plurality of stent single rings 2 and a plurality of inter-ring connectors 3. The stent single rings 2 are placed in a casting mold 1, and the inter-ring connectors 3 are injection molded by means of the casting mold 1 so that the inter-ring connectors 3 connect adjacent stent single rings 2; the inter-ring connectors 3 are circumferentially spaced between each two adjacent stent single rings 2, and the phase angles of two adjacent inter-ring connectors 3 in different layers differ by 30°. The thickness of the stent single ring 2 is h1, and the height of the connection of the inter-ring connector 3 is h2. The relationship between the thickness of the stent single ring 2 and the height of the connection of the inter-ring connector 3 is 2*h1. <h2。

[0038] The single ring 2 of the bracket is made of magnesium alloy, and the inter-ring connecting piece 3 is made of PLA.

[0039] The single ring 2 of the support and the inter-ring connecting piece 3 are in surface contact, and the two can slide in the circumferential direction.

[0040] The upper and lower connecting parts of the inter-ring connecting member 3 are respectively provided with through holes, and the through holes connect two adjacent single rings of the bracket 2 .

[0041] The casting mold 1 includes an outer mold 111, a middle mold 112 and an inner mold 113. The outer mold 111 is modularly designed to facilitate disassembly and assembly. The inner wall of the outer mold 111 is provided with a plurality of first grooves, the outer wall of the inner mold 113 is provided with a plurality of second grooves, the side wall of the middle mold 112 is provided with a middle mold ring cavity 14 and a plurality of rectangular through holes, the middle mold ring cavity 14 is connected with the plurality of rectangular through holes, the first grooves, the second grooves and the rectangular openings constitute an inter-ring connector mold cavity 15, and the inter-ring connector 3 is injection molded in the inter-ring connector mold cavity 15.

[0042] An injection through hole is opened on the side wall of the outer layer mold 111; the injection through hole includes an outer runner injection hole 11, a runner cavity through hole 12 and a molding liquid flow channel 13, the outer runner injection hole 11 is opened on the outer side wall of the outer layer mold 111, and the outer runner injection hole 11 is connected with the molding liquid flow channel 13; the molding liquid flow channel 13 is arranged inside the outer mold, the runner cavity through hole 12 is opened on the inner side wall of the outer layer mold 111, and the first end of the runner cavity through hole 12 is connected with the molding liquid flow channel 13, and the second end of the runner cavity through hole 12 is connected with the inter-ring connector cavity 15.

[0043] The inner layer mold 113 is provided with an exhaust through hole, which is in communication with the inter-ring connector mold cavity 15 .

[0044] The molding liquid flow channel 13 is annular in shape and passes through the outer mold 111 .

[0045] The outer runner injection hole 11 is located on the side wall of the outer mold 111 corresponding to the bottom end of the bottom connector cavity; the exhaust hole is located on the side wall of the inner mold 113 corresponding to the top end of the top connector cavity.

[0046] The middle mold 112 is provided with a middle mold ring cavity 14 , and the inner wall shape of the middle mold ring cavity 14 fits the outer contour of the bracket single ring 2 .

[0047] like Figure 2-Figure 3 As shown, a plurality of cavities formed by connecting the outer mold 111, the middle mold 112 and the inner mold 113 are the inter-ring connector mold cavities 15, and a plurality of inter-ring connectors 3 are injection molded in the inter-ring connector mold cavities 15. The inter-ring connectors 3 are provided with two upper and lower through holes to connect and fix two adjacent magnesium alloy vascular stent single rings 2.

[0048] The outer mold 111 of the magnesium-PLA composite biodegradable stent casting mold 1 is provided with a plurality of molding liquid flow channels 13, which are annular and penetrate the outer mold 111. The outer mold 111 can be composed of three or more sets of arc plates, so that it is easy to cooperate with the middle mold 112.

[0049] like Figure 4 As shown, two adjacent stent single rings 2 are connected by a plurality of inter-ring connectors 3 to form the overall structure of the magnesium-PLA composite biodegradable vascular stent.

[0050] The thickness of the single ring 2 of the bracket is h1, and the height of the connection between the ring connectors 3 is h2. It should be ensured that h2>2*h1 to ensure that the connection of the connector is not too thin to avoid the connector breaking due to the connection being too thin.

[0051] like Figure 6a As shown, the single ring 2 of the stent and the link connector of the traditional metal vascular stent are an integral structure. During the expansion process, the deformation of the single ring 2 of the stent will cause stress concentration at the connection between the single ring 2 of the stent and the link connector (indicated by the arrow).

[0052] The present invention proposes a magnesium-PLA composite biodegradable vascular stent in which the stent single ring 2 and the link connector are split structures such as Figure 6b As shown, the inter-ring connector 3 is made of non-metallic material, which effectively avoids stress concentration.

[0053] The cavity 15 of the inter-ring connector can be U-shaped or S-shaped, and the shape of the inter-ring connector 3 formed by injection molding will also change accordingly.

[0054] The material of the inter-ring connector 3 is other degradable non-metallic materials, such as PLLA, PCL, etc.

[0055] A method for preparing a magnesium-PLA composite biodegradable vascular stent is divided into three steps, as follows:

[0056] S1. After the single ring 2 of the stent is expanded, it is sequentially inserted into the middle mold ring cavity 14 of the middle mold 112, and the surface of the single ring 2 of the stent where the inter-ring connector 3 is required is coated with demoulding powder.

[0057] S2. Snap the outer mold 111 and the middle mold 112 together, inject the molten injection liquid into the molding liquid flow channel 13 through the outer runner injection hole 11, and inject it into the middle mold ring cavity 14 through the molding liquid flow channel 13 and the runner cavity through hole 12 to complete the injection molding.

[0058] S3. Demolding, disassembling the outer mold 111, trimming the excess parts formed in the molding liquid flow channel 13 and the exhaust flow channel, and taking out the blood vessel stent after cooling.

[0059] Before using the stent, it needs to be subjected to routine medical sterilization and disinfection treatment to ensure that it is in a sterile state before use.

[0060] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A magnesium-PLA composite degradable vascular stent, characterized in that: It comprises a plurality of support single rings and a plurality of inter-ring connecting members, wherein the support single rings are placed in a casting mold, and the inter-ring connecting members are injection molded by means of the casting mold so that the inter-ring connecting members connect adjacent support single rings; the inter-ring connecting members are arranged circumferentially between two adjacent support single rings, and the phase angles of two adjacent inter-ring connecting members in different layers differ by 30°, the thickness of the support single ring is h1, the height of the connection of the inter-ring connecting member is h2, and the relationship between the thickness of the support single ring and the height of the connection of the inter-ring connecting member is 2*h1 <h2。 2. The magnesium-PLA composite degradable vascular stent according to claim 1, characterized in that: The single ring of the bracket is made of magnesium alloy, and the connecting piece between the rings is made of PLA.

3. The magnesium-PLA composite degradable vascular stent according to claim 2, characterized in that: The single ring of the support is in surface contact with the inter-ring connecting piece, and the two can slide in the circumferential direction.

4. The magnesium-PLA composite degradable vascular stent according to claim 3, characterized in that: The upper and lower connecting parts of the inter-ring connecting member are respectively provided with through holes, and the through holes connect two adjacent single rings of the bracket.

5. The magnesium-PLA composite degradable vascular stent according to claim 3, characterized in that: The casting mold comprises an outer mold, a middle mold and an inner mold, the inner side wall of the outer mold is provided with a plurality of first grooves, the outer side wall of the inner mold is provided with a plurality of second grooves, the side wall of the middle mold is provided with a middle mold annular cavity and a plurality of rectangular through holes, the middle mold annular cavity is connected with the plurality of rectangular through holes, the first grooves, the second grooves and the rectangular through holes constitute an inter-ring connector cavity, and the inter-ring connector is injection molded in the inter-ring connector cavity; An injection through hole is provided on the side wall of the outer layer mold; the injection through hole includes an outer runner injection hole, a runner cavity through hole and a molding liquid flow channel, the outer runner injection hole is provided on the outer side wall of the outer layer mold, and the outer runner injection hole is connected to the molding liquid flow channel; the molding liquid flow channel is arranged inside the outer mold, the runner cavity through hole is provided on the inner side wall of the outer layer mold, and the first end of the runner cavity through hole is connected to the molding liquid flow channel, and the second end of the runner cavity through hole is connected to the inter-ring connector cavity; The inner layer mold is provided with an exhaust through hole, and the exhaust through hole is in communication with the cavity of the inter-ring connector.

6. The magnesium-PLA composite degradable vascular stent according to claim 5, characterized in that: The molding liquid flow channel is annular in shape and passes through the outer layer mold.

7. The magnesium-PLA composite degradable vascular stent according to claim 5, characterized in that: The outer runner injection hole is located on the side wall of the outer mold corresponding to the bottom end of the bottom connector mold cavity; the exhaust hole is located on the side wall of the inner mold corresponding to the top end of the top connector mold cavity.

8. The magnesium-PLA composite degradable vascular stent according to claim 5, characterized in that: The middle-layer mold is provided with a middle-layer mold ring cavity, and the inner wall shape of the middle-layer mold ring cavity fits the outer contour of the single ring of the bracket.

9. A method for preparing the magnesium-PLA composite degradable vascular stent according to any one of claims 1 to 8, characterized in that: include: S1. After the stent single ring is expanded, it is sequentially inserted into the middle mold ring cavity in the middle mold, and the release powder is applied to the surface of the stent single ring where the inter-ring connector is required; S2. The outer mold is buckled with the middle mold, and the molten injection liquid is injected into the molding liquid flow channel through the outer runner injection hole, and injected into the middle mold ring cavity through the molding liquid flow channel and the flow channel mold cavity through hole to complete the injection molding; S3. Demolding: dismantling the outer mold, trimming the excess parts formed in the molding liquid flow channel and the exhaust flow channel, and taking out the vascular stent after cooling.

Images