Auxetic material, absorbable intravascular stent and preparation method

Abstract

The invention provides an auxetic material, an absorbable intravascular stent and a preparation method, and belongs to the field of medical instruments.The auxetic material is composed of unit cell structures arrayed in the x-axis direction, the y-axis direction and the y = x straight line direction, each unit cell structure comprises a center supporting component, and four telescopic components are sequentially connected to the center supporting component; the telescopic parts are formed by twisting two isosceles sides of an isosceles triangle in one direction, the distance between the intersection point of the two isosceles sides and the center point of the center supporting part is shortened, and the unit cell structures adjacent to the array are connected with one another, namely the telescopic parts of the unit cell structures are connected with one another; in the auxetic state, the telescopic components form an isosceles triangle isosceles structure, a stable abutting structure is formed, the structure is more stable, better supporting is provided, and in the auxetic process, failures are reduced.

Description

Technical Field

[0001] This invention belongs to the field of medical devices, specifically relating to an expansion material, an absorbable vascular stent, and a method for its preparation. Background Technology

[0002] The primary clinical treatment for severe vascular stenosis is the implantation of vascular stents to maintain vascular patency. Common types include metallic stents and biodegradable stents (bioresorbable stents). However, metallic stents, as permanent implants, can impair the normal vasodilation and vasoconstriction functions of blood vessels, and are prone to problems such as elastic recoil, intimal damage, stent thrombosis, and intimal and smooth muscle hyperplasia in later stages. Biodegradable stents are generally made of biodegradable polymer materials. Compared to metallic stents, the biggest drawback of biodegradable stents is their mechanical properties, namely poor support strength and a tendency for early elastic recoil. Therefore, to maximize the mechanical performance of biodegradable stents, current biodegradable stents have a much thicker wall than metallic stents. This leads to several problems, such as a slower endothelialization process, a higher risk of inflammation and thrombosis in the early stages of implantation, and limitations on their application in severely stenotic vessels and small blood vessels. Summary of the Invention

[0003] Our project team has developed a technology, for which a Chinese invention patent application has been filed (2025116143516), disclosing a porous cell expandable material, an absorbable vascular stent, a preparation device, and a preparation method. The porous cells contain dumbbell-shaped pores, which are alternately arranged horizontally and vertically along both the long and short axes, forming an alternating array of dumbbell-shaped pores. The short axis of each dumbbell-shaped pore is equipped with an anti-rebound insertion and abutment support structure to maintain the shape of the expandable material during expansion and prevent contraction under axial compression, providing lasting support. However, during the expansion process, approximately 5% of the anti-rebound insertion and abutment support structures in the vascular stent formed from this porous cell expandable material fail, meaning the V-shaped plug cannot be accurately inserted into the slot, affecting the support force. To reduce the technical problem of failure during expansion, this invention provides an expandable material, an absorbable vascular stent, and a preparation method.

[0004] This invention is implemented in the following manner: An expandable material is provided, comprising an array of unit cell structures along the x-axis, y-axis, and the y=x line. Each unit cell structure includes a central support component, on which four telescopic components are sequentially connected. Each telescopic component is an isosceles triangle whose two isosceles sides are twisted in one direction, shortening the distance from the intersection of the two isosceles sides to the center point of the central support component. The interconnection of adjacent unit cell structures refers to their interconnection through the telescopic components of the unit cell structures. In the expanded state, the telescopic components form an isosceles triangular structure.

[0005] Furthermore, the central support component is a circular or square ring structure.

[0006] The absorbable vascular stent prepared from the above-mentioned tensile material is tubular, with the central support component and the telescopic component both located on the tubular surface, forming a tubular single-cell structure vascular stent. The material of the vascular stent is a bioabsorbable polymer.

[0007] Furthermore, the bioabsorbable polymer includes one or more of the following materials: polylactic acid, poly-L-lactic acid, polyglycolic acid, polylactic acid / glycolic acid copolymer, polycaprolactone, polylactic acid-caprolactone copolymer, polytrimethylene carbonate, polybutylene succinate, polyhydroxybutyrate, polyacetylglucan, polyoxoester, and polyesteramide.

[0008] The above-mentioned method for preparing absorbable vascular stents employs an injection molding device. The injection molding device includes a sliding base, on which a fixed mold is mounted. The fixed mold has three concave molds circumferentially arranged, each with a concave surface that mates with the surface of the fixed mold. A female mold for forming tensile material is provided on the inner surface of the concave molds. The concave molds are slidably mounted on the sliding base via radial guide rails, such that the three concave molds and the fixed mold form a closed mold. The interior of the mold is a cavity for forming tensile material. The concave molds are provided with an injection port and an injection channel. The preparation method includes the following steps: 1) Mold closing: The mold clamping mechanism of the injection molding device pushes the concave mold to slide radially along the guide rail pair, so that the concave mold and the fixed mold are tightly closed, and the inside of the mold is a cavity for forming the tensile material; 2) Injection and holding pressure: The molten bioabsorbable polymer is pushed through the injection port and injection channel on the concave mold at high speed and high pressure and fills the entire cavity of the mold. 3) Cooling and solidification: After the pressure holding is completed, the injected material is cooled in the mold cavity by the cooling device inside the mold until it is completely solidified; 4) Mold opening and ejection: After the product cools and solidifies, the mold locking mechanism drives the concave mold to retract, the mold opens, and the tubular push rod moves forward under hydraulic or mechanical action, automatically ejecting the formed product from the mold cavity or core. 5) Post-processing: Trim the sprue material and disinfect it to obtain absorbable vascular stents.

[0009] Compared to existing technologies, this invention uses a unit cell structure of a central support component and a telescopic component as the basic unit of the expansion material. The telescopic component is an isosceles triangle whose two isosceles sides are twisted in the same direction, shortening the distance from the intersection of the two isosceles sides to the center point of the central support component. The array of adjacent unit cell structures are interconnected. In the expansion state, the twisted isosceles sides straighten, forming an isosceles structure of two isosceles sides of the isosceles triangle, which constitutes a stable top support structure. The structure is more stable, provides better support, and reduces failure during the expansion process. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the structure of an absorbable vascular stent.

[0011] Figure 2 This is a schematic diagram of the unfolded absorbable vascular stent.

[0012] Figure 3 yes Figure 2 Schematic diagram of the middle unit cell structure.

[0013] Figure 4 This is a schematic diagram of the structure of an absorbable vascular stent in its expanded state.

[0014] Figure 5 This is a schematic diagram of the expansion of an absorbable vascular stent.

[0015] Figure 6 yes Figure 5 Schematic diagram of the middle unit cell structure.

[0016] Figure 7 This is a schematic diagram of another implementation of the single-cell structure.

[0017] Figure 8 This is a schematic diagram of a single-cell structure in an expanded state during another implementation.

[0018] Figure 9 This is a 3D view of an injection molding device.

[0019] Figure 10 This is a cross-sectional view of the injection molding device.

[0020] Figure 11 This is a schematic diagram of the internal concave mold.

[0021] Figure 12This is an enlarged view of the female mold inside a concave mold.

[0022] Figure 13 This is a schematic diagram of the injection molding device in the mold-closed state.

[0023] Among them, 1 is the tensile material; 2 is the unit cell structure; 3 is the central support component; 4 is the telescopic component; 5 is the injection molding device; 51 is the sliding base; 52 is the fixed mold; 53 is the concave mold; 54 is the tubular push rod; 55 is the injection port; 56 is the injection channel; 57 is the female mold; 6 is the absorbable vascular stent; 7 is the bioabsorbable polymer. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, unless otherwise specified, the specific experimental methods involved in the following embodiments are conventional methods or implemented according to the conditions recommended in the manufacturer's instructions.

[0025] See Figures 1-13 An expandable material 1 is described, comprising unit cell structures 2 arrayed along the x-axis, y-axis, and the y=x line. Each unit cell structure 2 includes a central support component 3, on which four telescopic components 4 are sequentially connected. Each telescopic component 4 is an isosceles triangle whose two isosceles sides are twisted in one direction, shortening the distance from the intersection of the two isosceles sides to the center point of the central support component 3. The array of adjacent unit cell structures 2 is interconnected through the telescopic components. In the expanded state, the telescopic components 4 form an isosceles triangular structure. The greater the degree of twisting of the two isosceles sides of the isosceles triangle in the telescopic components, the greater the range of expansion and contraction, and the larger the expanded volume.

[0026] The basic unit of the expandable material is a unit cell structure consisting of a central support component and a telescopic component. The telescopic component is an isosceles triangle whose two isosceles sides are twisted in the same direction, shortening the distance from the intersection of the two isosceles sides to the center point of the central support component. Adjacent unit cells in the array are interconnected. In the expanded state, the twisted isosceles sides straighten, forming an isosceles structure with two isosceles sides of the isosceles triangle, creating a stable top support structure. This structure is more stable, provides better support, and reduces failure during the expanded state. The top support structure maintains the shape of the expanded material during expansion, preventing contraction under axial compression and providing sustained support.

[0027] In one embodiment, such as Figures 1-6 As shown, the central support component 3 is a ring; in another embodiment, as... Figure 7 , Figure 8 As shown, the central support component 3 has a square ring structure.

[0028] like Figure 1 , 4 As shown, the absorbable vascular stent 6 is prepared using the above-mentioned tensile material. The absorbable vascular stent 6 is tubular, and the central support component 3 and the telescopic component are both located on the tubular surface, forming a tubular single-cell structure 2 of the vascular stent. The material of the vascular stent is a bioabsorbable polymer 7.

[0029] This structure, when used to form a vascular stent, prevents the stent from contracting radially and axially when subjected to radial force due to vascular rebound, maintains the shape of the stent, provides reliable radial support, ensures vascular patency, improves the mechanical properties of bioresorbable stents, reduces the amount of bioresorbable polymer material used, and lowers the wall thickness.

[0030] Vascular stents are made of bioabsorbable polymer materials that degrade slowly, allowing blood vessels to adapt and remodel, regain elasticity, and avoid the complications associated with permanent metal stent implantation.

[0031] Preferably, the bioabsorbable polymer comprises one or more of the following materials: polylactic acid, poly-L-lactic acid, polyglycolic acid, polylactic acid / glycolic acid copolymer, polycaprolactone, polylactic acid-caprolactone copolymer, polytrimethylene carbonate, polybutylene succinate, polyhydroxybutyrate, polyacetylglucan, polyoxyethylene, and polyesteramide.

[0032] The absorbable vascular stent is placed in the blood vessel by means of a balloon. When the balloon expands the vascular stent, the stent will expand radially and extend axially at the same time, so that while the stent expands radially, its axial length is greater than its original length.

[0033] The above-mentioned method for preparing absorbable vascular stents, wherein the preparation method uses an injection molding device 5, such as... Figures 9-13 As shown, the injection molding device 5 includes a sliding base 51, on which a fixed mold 52 is mounted. The fixed mold 52 has three concave molds 53 arranged circumferentially around its surface, each with a concave surface that mates with the surface of the fixed mold 52. A female mold 57 for stretching material is disposed on the inner surface of each concave mold 53. Figure 12 As shown, the female mold has a groove on the inner surface of the concave mold 53. The concave mold 53 is slidably mounted on the sliding base 51 through a radial guide pair, so that the three concave molds and the fixed mold form a closed mold. The inside of the mold is a cavity for forming the tensile material. The concave mold 53 is provided with an injection port 55 and an injection channel 56. The preparation method includes the following steps: 1) Mold Closure: The mold clamping mechanism of the injection molding device pushes the concave mold to slide radially along the guide rail pair, so that the concave mold and the fixed mold are tightly closed. The inside of the mold is a cavity for forming the expansion material. The concave mold and the fixed mold are tightly closed, and a huge clamping force (tens of tons to thousands of tons) is applied to resist the cavity pressure generated during subsequent injection and prevent the mold from expanding and producing flash. The mold clamping mechanism is existing technology and will not be described in detail here.

[0034] 2. Injection and holding pressure: The molten bioabsorbable polymer 7 is pushed through the injection port 55 and injection channel 56 on the concave mold 53 at high speed and high pressure and fills the entire cavity of the mold. Specifically, during mold closing, bioabsorbable polymer particles from the hopper fall into the barrel. The barrel has a heating coil on the outside and a rotating screw inside. As the screw rotates and retracts, it conveys, compacts, and shears the bioabsorbable polymer particles forward, melting them into a homogeneous melt under the combined action of external heating and internal shear heat. The melt accumulates at the front end of the screw, pushing it back to the metering position.

[0035] After the mold is closed, the screw stops rotating and moves forward axially under the push of the high-pressure cylinder, like a syringe, injecting the molten bioabsorbable polymer stored at the front end of the screw into the mold cavity at a lower temperature at high speed and high pressure.

[0036] After the melt fills the cavity, the screw continues to advance slightly forward at a certain pressure (holding pressure), continuously replenishing the melt that has been reduced due to cooling and shrinkage, ensuring that the product is full and dense, and preventing shrinkage marks and depressions. This stage continues until the gate (the channel through which the melt enters the cavity) solidifies and seals.

[0037] 3) Cooling and Shaping: After the holding pressure is completed, the injected material is cooled within the mold cavity by a cooling device inside the fixed mold until it is completely solidified, obtaining sufficient strength and rigidity for ejection. Cooling is achieved through cooling water channels (circulating cooling water or oil) designed inside the mold. Cooling time accounts for more than 70% of the entire molding cycle and is crucial to production efficiency. Cooling must be uniform; otherwise, it will lead to product deformation and internal stress concentration. The cooling device inside the fixed mold is existing technology and will not be described in detail here. It can be any existing technology (CN218053740U) or other existing technologies. The fixed mold in this invention is cylindrical.

[0038] 4) Mold opening and ejection: After the product cools and solidifies, the mold locking mechanism drives the concave mold to retreat, the mold opens, and the tubular push rod (54) moves forward under hydraulic or mechanical action, automatically ejecting the molded product from the mold cavity or core; After ejection, the ejection mechanism resets, preparing for the next mold closing. Sometimes, it is necessary to coordinate with a robotic arm or robot to automatically grip the product and place it in the designated position.

[0039] 5) Post-processing: Trim the sprue material and disinfect it to obtain absorbable vascular stent 1.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several changes and improvements without departing from the overall concept of the present invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A tensile material, characterized in that, The tensile material (1) is composed of unit cell structures (2) arranged in an array along the x-axis, y-axis and the y=x line. The unit cell structure (2) includes a central support component (3). Four telescopic components (4) are arranged sequentially on the central support component (3). The telescopic component (4) is an isosceles triangle whose two isosceles sides are twisted in one direction, shortening the distance from the intersection of the two isosceles sides to the center point of the central support component (3). The interconnection of adjacent unit cell structures (2) in the array means that they are interconnected through the telescopic components of the unit cell structure. In the tensile state, the telescopic components (4) form an isosceles triangle structure.

2. The tensile material as described in claim 1, characterized in that, The central support component (3) is a circular or square ring structure.

3. The absorbable vascular stent prepared from the tensile material as described in any one of claims 1 to 2, characterized in that, The absorbable vascular stent (6) is tubular, and the central support component (3) and the telescopic component are both located on the tubular surface, forming a tubular single-cell structure (2) of the vascular stent. The material of the vascular stent is a bioabsorbable polymer (7).

4. The absorbable vascular stent as described in claim 3, characterized in that, The bioabsorbable polymer includes one or more of the following materials: polylactic acid, poly-L-lactic acid, polyglycolic acid, polylactic acid / glycolic acid copolymer, polycaprolactone, polylactic acid-caprolactone copolymer, polytrimethylene carbonate, polybutylene succinate, polyhydroxybutyrate, polyacetylglucan, polyoxo-ester, and polyesteramide.

5. The method for preparing the absorbable vascular stent as described in claim 4, characterized in that, The preparation method uses an injection molding device (5), which includes a sliding base (51). A fixed mold (52) is mounted on the sliding base (51). The fixed mold (52) has three concave molds (53) with concave surfaces that cooperate with the surface of the fixed mold (52) around its circumference. A female mold (57) for stretching material is provided on the inner surface of the concave mold (53). The concave mold (53) is slidably mounted on the sliding base (51) through a radial guide pair, so that the three concave molds and the fixed mold form a closed mold. The inside of the mold is a cavity for forming the stretching material. The concave mold (53) is provided with an injection port (55) and an injection channel (56). The preparation method includes the following steps: 1) Mold closing: The mold clamping mechanism of the injection molding device pushes the concave mold to slide radially along the guide rail pair, so that the concave mold and the fixed mold are tightly closed, and the inside of the mold is a cavity for forming the tensile material; 2) Injection and holding pressure: The molten bioabsorbable polymer (7) is pushed through the injection port (55) and injection channel (56) on the concave mold (53) at high speed and high pressure and fills the entire cavity of the mold. 3) Cooling and solidification: After the pressure holding period, the injected material is cooled in the mold cavity by the cooling device inside the mold until it is completely solidified; 4) Mold opening and ejection: After the product cools and solidifies, the mold locking mechanism drives the concave mold to retreat, the mold opens, and the tubular push rod (54) moves forward under hydraulic or mechanical action, automatically ejecting the molded product from the mold cavity or core; 5) Post-processing: Trim the sprue material and disinfect it to obtain the absorbable vascular stent as described in claim 4.

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