A medical degradable stent fiber and a preparation method thereof

Abstract

The application provides a kind of medical degradable stent fiber and its preparation method, it is related to medical biomaterials technical field, including, the core layer is made of stereocomplex polylactic acid, the stereocomplex polylactic acid is formed by poly L-lactic acid and poly D-lactic acid melt blending, the mass ratio of poly L-lactic acid and poly D-lactic acid is 45:55-55:45, the application is by constructing core sheath coaxial structure, introduce stereocomplex polylactic acid in core layer and form high content stereocomplex crystal region, set up degradable copolymer containing carbonate unit in sheath layer and disperse buffer neutralizing component, realize the synergistic control of mechanical property and degradation performance.The stereocomplex crystalline structure of core layer improves the radial support strength and dimensional stability of stent fiber;Carbonate unit in sheath layer adjusts the degradation rate of material, the acidic substances generated by buffer neutralizing component are neutralized, improve local microenvironment, delay mechanical property attenuation, improve overall use stability and safety.

Description

Technical Field

[0001] This invention relates to the field of medical biomaterials technology, specifically to a biodegradable medical scaffold fiber and its preparation method. Background Technology

[0002] In existing technologies, medical stents are used for the support and shaping of blood vessels or other cavities. Traditional metal stents are mature technologies with high radial support force and structural stability. To reduce the foreign body burden caused by long-term placement, biodegradable stents are gradually being developed. Commonly used materials include biodegradable polymers such as polylactic acid, polyglycolic acid, and polycaprolactone. Some designs use fibers as basic components, forming a mesh stent structure through weaving, winding, or knitting to achieve better flexibility, compressibility, and shape adaptability. The support and degradation behavior of the stent can be controlled by parameters such as fiber diameter, orientation, crystallinity, and heat treatment.

[0003] The aforementioned biodegradable scaffold fibers still have shortcomings: the degradation rate is difficult to match with the support maintenance time, the decrease in molecular weight during degradation causes a sudden drop in mechanical strength, the local acidification of degradation products increases the risk of irritation, and it is difficult to guarantee stability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a biodegradable medical stent fiber and its preparation method. The technical problem this invention aims to solve is: how to construct a coaxial core-sheath structure of a stereocomposite polylactic acid core layer and a copolymer sheath layer containing sustained-release neutralizing particles, and then perform composite spinning and stretching processes to solve the problems of mismatch between degradation rate and support maintenance time, sudden mechanical drop, and high risk of degradation and acidification in biodegradable stents.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a biodegradable medical scaffold fiber, comprising a core layer and a sheath layer coaxially arranged: The core layer is composed of stereocomposite polylactic acid, which is formed by melt blending poly-L-lactic acid and poly-D-lactic acid, and the mass ratio of poly-L-lactic acid to poly-D-lactic acid is 45:55-55:45. The sheath is composed of a biodegradable copolymer containing carbonate units, wherein the biodegradable copolymer is poly(lactic acid-trimethylene carbonate); A buffering and neutralizing component is dispersed within the sheath layer. The buffering and neutralizing component is a coated alkaline inorganic particle, which is composed of magnesium hydroxide and calcium carbonate. The coating layer of the coated alkaline inorganic particle is a biodegradable polymer. The mass fraction of the buffering and neutralizing component in the scaffold fiber is 0.3%-5.0%. The diameter of the core layer accounts for 70%-85% of the diameter of the scaffold fiber; the diameter of the scaffold fiber is 120μm-300μm.

[0006] The present invention is further configured such that the coating layer is polycaprolactone, the thickness of the coating layer is 50nm-500nm, and the D50 particle size of the coated alkaline inorganic particles is 0.2μm-5.0μm.

[0007] The present invention is further configured such that the content of the stereocomposite crystal region in the core layer is 30%-70%; and the weight-average molecular weight of the core layer is 150k-350k.

[0008] The present invention is further configured such that the molar fraction of the trimethylene carbonate unit in the poly(lactic acid-trimethylene carbonate) is 15%-55%; and the thickness of the sheath is 10μm-80μm.

[0009] A method for preparing biodegradable medical scaffold fibers, comprising: S1. Poly-L-lactic acid and poly-D-lactic acid are dried and then melt-blended to obtain a core layer melt; S2. Using magnesium hydroxide particles and calcium carbonate particles as the core, a biodegradable polymer is used to form a coating layer to obtain coated alkaline inorganic particles. The coated alkaline inorganic particles are melt-blended with poly(lactic acid-trimethylene carbonate) to obtain a sheath melt. S3. The core melt and the sheath melt are fed into the coaxial composite spinneret assembly respectively, and the nascent fibers with a core-sheath coaxial structure are extruded simultaneously. S4. The nascent fibers are subjected to stretching and orientation treatment, and the stretched and oriented nascent fibers are subjected to heat treatment to shape them, so that the core layer forms a crystalline structure containing stereocomplex crystal regions, and thus a shaped fiber is obtained. S5. Cool and wind up the shaped fiber to obtain medical biodegradable scaffold fiber.

[0010] The present invention is further configured such that the poly-L-lactic acid and the poly-D-lactic acid are respectively vacuum dried before melt blending, and dried to a water content of not more than 200 ppm; the mass ratio of the poly-L-lactic acid to the poly-D-lactic acid is 45:55-55:45.

[0011] The present invention is further configured such that the biodegradable polymer is polycaprolactone; the coating layer thickness is 50nm-500nm; and the D50 particle size of the coated alkaline inorganic particles is 0.2μm-5.0μm.

[0012] The present invention is further configured such that the coated alkaline inorganic particles and the poly(lactic acid-trimethylene carbonate) are melt-blended using a twin-screw extruder to uniformly disperse the coated alkaline inorganic particles in the sheath melt; the mass fraction of the coated alkaline inorganic particles in the medical biodegradable scaffold fiber is 0.3%-5.0%.

[0013] The present invention is further configured such that the core melt and the sheath melt are respectively metered and delivered to the coaxial composite spinneret by independent metering pumps; by setting the rotation speed of the core metering pump and the sheath metering pump, the volumetric flow rate ratio of the core layer to the sheath layer is 1.0-2.6, so that the core layer diameter accounts for 70%-85% of the scaffold fiber diameter; the scaffold fiber diameter is measured by an online diameter measuring device, and the traction speed is adjusted so that the scaffold fiber diameter is 120μm-300μm.

[0014] The present invention is further configured such that the total draw ratio of the drawing and orientation treatment is 2.0-6.0; the heat treatment and shaping temperature is 110℃-160℃; after the heat treatment and shaping, the stereocomposite crystal region content of the core layer is 30%-70%; after cooling, it is wound with a constant winding tension to fix the orientation structure and crystal structure of the shaped fiber.

[0015] The beneficial effects of this invention are as follows: By constructing a core-sheath coaxial structure, this invention introduces stereocomposite polylactic acid into the core layer to form a high-content stereocomposite crystalline region, and sets a biodegradable copolymer containing carbonate units in the sheath layer and disperses buffering and neutralizing components, thereby achieving synergistic regulation of mechanical properties and degradation performance. The stereocomposite crystalline structure of the core layer improves the radial support strength and dimensional stability of the scaffold fibers; the carbonate units in the sheath layer regulate the material degradation rate, and the buffering and neutralizing components neutralize the acidic substances generated during degradation, improving the local microenvironment, delaying the decay of mechanical properties, and enhancing the overall stability and safety of use.

[0016] This invention employs coated alkaline inorganic particles as a buffer and neutralizing component, and uses a biodegradable polymer to form a coating layer. This allows the alkaline particles to be uniformly dispersed within the sheath and released in a controlled manner, reducing the risk of interface defects or stress concentration caused by direct particle exposure. A coaxial composite extrusion process combined with stretching orientation and heat treatment shaping is used to form a stable stereocomposite crystalline structure in the core layer, improving crystallinity and mechanical strength while maintaining the integrity of the fiber structure. This results in a biodegradable medical scaffold fiber that possesses both high initial support performance and controllable degradation behavior. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0018] Figure 2 This is a schematic diagram of the core layer microstructure of the present invention.

[0019] Figure 3 This is a schematic diagram of the particle structure of the buffer neutralizing component of the present invention.

[0020] Figure 4 This is a schematic diagram of the fiber size relationship of the present invention.

[0021] Figure 5This is a process flow diagram of the preparation method of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0023] Please see Figures 1-5 The present invention relates to a biodegradable medical scaffold fiber, comprising a core layer and a sheath layer arranged coaxially: The core layer is composed of stereocomposite polylactic acid, which is formed by melt blending poly(L-lactic acid) and poly(D-lactic acid) in a mass ratio of 45:55. The stereocomposite crystalline region content of the core layer is 30%. The weight-average molecular weight of the core layer is 150kJ.

[0024] The sheath is composed of a biodegradable copolymer containing carbonate units, specifically poly(lactic acid-trimethylene carbonate). The molar fraction of the trimethylene carbonate units in the poly(lactic acid-trimethylene carbonate) is 15%. The thickness of the sheath is 10 μm.

[0025] A buffering and neutralizing component, consisting of coated alkaline inorganic particles (magnesium hydroxide and calcium carbonate), is dispersed within the sheath. The coating layer of these particles is a biodegradable polymer. The mass fraction of the buffering and neutralizing component in the scaffold fibers ranges from 0.3% to 5.0%. The coating layer is made of polycaprolactone and has a thickness of 50 nm. The D50 particle size of the coated alkaline inorganic particles is 0.2 μm.

[0026] The core layer has a diameter that is 70% of the scaffold fiber diameter. The scaffold fiber diameter is 120 μm.

[0027] A method for preparing biodegradable medical scaffold fibers, comprising: S1. Poly-L-lactic acid and poly-D-lactic acid are dried and then melt-blended to obtain a core layer melt. Poly-L-lactic acid and poly-D-lactic acid are separately vacuum-dried before melt blending until the moisture content does not exceed 200 ppm. The mass ratio of poly-L-lactic acid to poly-D-lactic acid is 45:55.

[0028] S2. Using magnesium hydroxide and calcium carbonate particles as the core, a biodegradable polymer is used to form a coating layer to obtain coated basic inorganic particles. These coated basic inorganic particles are then melt-blended with poly(lactic acid-trimethylene carbonate) to obtain a sheath melt. The biodegradable polymer is polycaprolactone. The coating layer thickness is 50 nm. The D50 particle size of the coated basic inorganic particles is 0.2 μm. The coated basic inorganic particles and poly(lactic acid-trimethylene carbonate) are melt-blended using a twin-screw extruder to ensure uniform dispersion of the coated basic inorganic particles in the sheath melt. The mass fraction of the coated basic inorganic particles in the medical biodegradable scaffold fiber is 0.3%.

[0029] S3. The core melt and sheath melt are fed into the coaxial composite spinneret assembly separately, and simultaneously extruded to form nascent fibers with a core-sheath coaxial structure. The core melt and sheath melt are metered and delivered to the coaxial composite spinneret assembly by independent metering pumps. By setting the rotational speeds of the core metering pump and the sheath metering pump, the volumetric flow rate ratio of the core to the sheath is made 1.0, so that the core diameter accounts for 70% of the scaffold fiber diameter. The scaffold fiber diameter is measured by an online diameter measuring device, and the traction speed is adjusted to make the scaffold fiber diameter 120μm.

[0030] S4. The nascent fibers are drawn and oriented, and then heat-treated to set the shape, causing the core layer to form a crystalline structure containing stereocomplex crystalline regions, thus obtaining the shaped fiber. The total draw ratio for the drawing and orientation treatment is 2.0. The heat treatment temperature is 110℃. After heat treatment, the stereocomplex crystalline region content of the core layer is 30%. After cooling, the fiber is wound up with a constant winding tension to fix the orientation and crystalline structure of the shaped fiber.

[0031] S5. Cool and wind up the shaped fiber to obtain medical biodegradable scaffold fiber.

[0032] Under the conditions specified in this embodiment, the biodegradable medical scaffold fiber of the present invention forms a structural system characterized by rapid degradation response through a combination of a core structure with a low content of stereocomplex crystalline regions, a relatively thin sheath structure, and a low content of buffering and neutralizing components. The biodegradable medical scaffold fiber of the present invention exhibits a rapid decline in mechanical properties and a rapid overall degradation process during in vivo use. Therefore, the biodegradable medical scaffold fiber of the present invention is more suitable for applications requiring short-term tissue support and where early material absorption and replacement are desirable. Example 2

[0033] Please see Figures 1-5 Based on Example 1, a biodegradable medical scaffold fiber includes a core layer and a sheath layer arranged coaxially: The core layer is composed of stereocomposite polylactic acid, which is formed by melt blending poly(L-lactic acid) and poly(D-lactic acid) in a mass ratio of 50:50. The stereocomposite crystalline region content of the core layer is 50%. The weight-average molecular weight of the core layer is 250kJ.

[0034] The sheath is composed of a biodegradable copolymer containing carbonate units, specifically poly(lactic acid-trimethylene carbonate). The molar fraction of the trimethylene carbonate units in the poly(lactic acid-trimethylene carbonate) is 35%. The thickness of the sheath is 45 μm.

[0035] A buffering and neutralizing component, consisting of coated alkaline inorganic particles (magnesium hydroxide and calcium carbonate), is dispersed within the sheath. The coating layer of these particles is a biodegradable polymer, and the buffering and neutralizing component constitutes 2.65% of the scaffold fibers by mass. The coating layer is made of polycaprolactone and has a thickness of 275 nm. The D50 particle size of the coated alkaline inorganic particles is 2.6 μm.

[0036] The core layer's diameter accounts for 77.5% of the scaffold fiber's diameter. The scaffold fiber's diameter is 210 μm.

[0037] A method for preparing biodegradable medical scaffold fibers, comprising: S1. Poly-L-lactic acid and poly-D-lactic acid are dried and then melt-blended to obtain a core layer melt. Poly-L-lactic acid and poly-D-lactic acid are separately vacuum-dried before melt blending until the moisture content does not exceed 200 ppm. The mass ratio of poly-L-lactic acid to poly-D-lactic acid is 50:50.

[0038] S2. Using magnesium hydroxide and calcium carbonate particles as the core, a biodegradable polymer is used to form a coating layer to obtain coated basic inorganic particles. These coated basic inorganic particles are then melt-blended with poly(lactic acid-trimethylene carbonate) to obtain a sheath melt. The biodegradable polymer is polycaprolactone. The coating layer thickness is 275 nm. The D50 particle size of the coated basic inorganic particles is 2.6 μm. The coated basic inorganic particles and poly(lactic acid-trimethylene carbonate) are melt-blended using a twin-screw extruder to ensure uniform dispersion of the coated basic inorganic particles in the sheath melt. The mass fraction of the coated basic inorganic particles in the medical biodegradable scaffold fiber is 2.65%.

[0039] S3. The core melt and sheath melt are fed into the coaxial composite spinneret assembly separately, and simultaneously extruded to form nascent fibers with a core-sheath coaxial structure. The core melt and sheath melt are metered and delivered to the coaxial composite spinneret assembly by independent metering pumps. By setting the rotational speeds of the core metering pump and the sheath metering pump, the volumetric flow rate ratio of the core to the sheath is made 1.8, so that the core diameter accounts for 77.5% of the scaffold fiber diameter. The scaffold fiber diameter is measured by an online diameter measuring device, and the traction speed is adjusted to make the scaffold fiber diameter 210 μm.

[0040] S4. The nascent fibers are drawn and oriented, and then heat-treated to set the shape, causing the core layer to form a crystalline structure containing stereocomplex crystalline regions, thus obtaining the shaped fiber. The total draw ratio for the drawing and orientation treatment is 4.0. The heat treatment temperature is 135℃. After heat treatment, the stereocomplex crystalline region content of the core layer is 50%. After cooling, the fiber is wound up with a constant winding tension to fix the orientation and crystalline structure of the shaped fiber.

[0041] S5. Cool and wind up the shaped fiber to obtain medical biodegradable scaffold fiber.

[0042] The biodegradable medical scaffold fiber of this embodiment achieves a balance between mechanical properties and degradation rate through a synergistic design of a core structure with a moderate content of stereocomplex crystalline regions, a sheath structure of moderate thickness, and a suitable proportion of buffering and neutralizing components. The biodegradable medical scaffold fiber of this invention can maintain structural stability in vivo for a certain period, while simultaneously achieving a relatively balanced degradation and acid neutralization process. Therefore, the biodegradable medical scaffold fiber of this invention is suitable for clinical applications requiring both long-term support and controlled degradation. Example 3

[0043] Please see Figures 1-5 Based on Examples 1 and 2, a biodegradable medical scaffold fiber includes a core layer and a sheath layer arranged coaxially: The core layer is composed of stereocomposite polylactic acid, which is formed by melt blending poly(L-lactic acid) and poly(D-lactic acid) in a mass ratio of 55:45. The stereocomposite crystalline region content of the core layer is 70%. The weight-average molecular weight of the core layer is 350kJ.

[0044] The sheath is composed of a biodegradable copolymer containing carbonate units, specifically poly(lactic acid-trimethylene carbonate). The molar fraction of the trimethylene carbonate units in the poly(lactic acid-trimethylene carbonate) is 55%. The thickness of the sheath is 80 μm.

[0045] A buffering and neutralizing component, consisting of coated alkaline inorganic particles (magnesium hydroxide and calcium carbonate), is dispersed within the sheath. The coating layer of these particles is a biodegradable polymer, and the buffering and neutralizing component constitutes 5.0% of the scaffold fibers by mass. The coating layer is made of polycaprolactone and has a thickness of 500 nm. The D50 particle size of the coated alkaline inorganic particles is 5.0 μm.

[0046] The core layer has a diameter that is 85% of the scaffold fiber diameter. The scaffold fiber diameter is 300 μm.

[0047] A method for preparing biodegradable medical scaffold fibers, comprising: S1. Poly-L-lactic acid and poly-D-lactic acid are dried and then melt-blended to obtain a core layer melt. Poly-L-lactic acid and poly-D-lactic acid are separately vacuum-dried before melt blending until the moisture content does not exceed 200 ppm. The mass ratio of poly-L-lactic acid to poly-D-lactic acid is 55:45.

[0048] S2. Using magnesium hydroxide and calcium carbonate particles as the core, a biodegradable polymer is used to form a coating layer to obtain coated basic inorganic particles. These coated basic inorganic particles are then melt-blended with poly(lactic acid-trimethylene carbonate) to obtain a sheath melt. The biodegradable polymer is polycaprolactone. The coating layer thickness is 500 nm. The D50 particle size of the coated basic inorganic particles is 5.0 μm. The coated basic inorganic particles and poly(lactic acid-trimethylene carbonate) are melt-blended using a twin-screw extruder to ensure uniform dispersion of the coated basic inorganic particles in the sheath melt. The mass fraction of the coated basic inorganic particles in the medical biodegradable scaffold fiber is 5.0%.

[0049] S3. The core melt and sheath melt are fed into the coaxial composite spinneret assembly separately, and simultaneously extruded to form nascent fibers with a core-sheath coaxial structure. The core melt and sheath melt are metered and delivered to the coaxial composite spinneret assembly by independent metering pumps. By setting the rotational speeds of the core metering pump and the sheath metering pump, the volumetric flow rate ratio of the core to the sheath is made 2.6, so that the core diameter accounts for 85% of the scaffold fiber diameter. The scaffold fiber diameter is measured by an online diameter measuring device, and the traction speed is adjusted to make the scaffold fiber diameter 300μm.

[0050] S4. The nascent fibers are drawn and oriented, and then heat-treated to set the shape, causing the core layer to form a crystalline structure containing stereocomplex crystalline regions, thus obtaining the shaped fiber. The total draw ratio for the drawing and orientation treatment is 6.0. The heat treatment temperature is 160℃. After heat treatment, the stereocomplex crystalline region content of the core layer is 70%. After cooling, the fiber is wound up with a constant winding tension to fix the orientation and crystalline structure of the shaped fiber.

[0051] S5. Cool and wind up the shaped fiber to obtain medical biodegradable scaffold fiber.

[0052] The biodegradable medical scaffold fiber of this embodiment forms a structural system characterized by strong mechanical integrity and a long degradation period through a core structure with a high content of stereocomplex crystalline regions, a thick sheath structure, and a high proportion of buffering and neutralizing components. The biodegradable medical scaffold fiber of this invention can maintain structural integrity in vivo for a long time and provides continuous acidic environment regulation during degradation. Therefore, the biodegradable medical scaffold fiber of this invention is more suitable for medical applications requiring long-term support and delayed degradation. Example 4

[0053] Please see Figures 1-5 Based on Examples 1, 2 and 3, this example aims to optimize the preparation process of medical biodegradable scaffold fibers by adjusting the formula and process parameters, so as to achieve precise control over the core layer ratio, fiber diameter, rigidity and crystal structure.

[0054] 1. Core layer blending stage The production line completes three formulations sequentially on the same extrusion equipment.

[0055] First, the materials were fed into the extruder according to the parameters of Experiment A. Poly-L-lactic acid and poly-D-lactic acid were added at a ratio of 45:55. After the materials melted, the screw load was in a stable range, the melt flowed smoothly, and the extrusion pressure remained at a low level. The extruded strip was flexible, and the blade resistance was low during pelletizing.

[0056] Subsequently, the mix ratio was switched to 50:50 for Experiment B. With the original temperature setting unchanged, the equipment load increased significantly. To maintain stable output, the operator appropriately reduced the feeding rate. The extruded strip stiffness increased, and the tension in the cooling section increased slightly.

[0057] When the ratio was further adjusted to 55:45 as in Experiment C and a higher molecular weight raw material was used, the screw torque continued to increase within the same temperature range. To avoid fluctuations, the residence time in the melt section was appropriately extended. The extruded strip exhibited greater rigidity, and the pelletizing sound became brittle.

[0058] 2. Sheath layer mixing stage After the core layer raw materials were prepared, the preparation of the sheath melt began.

[0059] When using the particle system of Experiment A, the particle size is small and the addition ratio is low, and the material is quickly coated by the resin after entering the twin-screw extruder. The mixing process is stable, the extruded strip has a continuous appearance, and there is no obvious particle outline.

[0060] When switching to Experiment B formulation, the particle size increased and the addition ratio increased. The load in the mixing section increased, and the melt showed a slight grainy texture. To ensure dispersion, the screw shear zone filling rate was appropriately increased. The surface of the discharge strip began to show a uniform, fine texture.

[0061] Under experimental condition C, the mixing resistance further increased after large-diameter particles with a high addition ratio entered the system. With the equipment rotation speed remaining constant, the current value was significantly higher than the previous two groups. The melt exhibited a more pronounced particle presence. The surface roughness of the discharge strip increased, but the overall continuity was maintained.

[0062] The three situations occur sequentially in the same equipment, with the processing load and melt state changing in a stepwise manner.

[0063] 3. Differences in structure formation during coaxial composite extrusion process When entering the composite spinning stage, Experiment A used a core-sheath flow ratio of 1.0. During the initial fiber formation, the interface between the core and sheath layers was distinct, the overall diameter was small, and the required traction tension in the cooling zone was low.

[0064] After changing to parameters B in experiment B, the core layer feed ratio was increased. The fiber expansion at the spinneret increased, and the cooling distance was correspondingly lengthened. The core layer area increased, and the sheath layer thickness increased significantly.

[0065] After further increasing the flow ratio to that of Experiment C, the material filling at the spinneret improved, and the core layer proportion increased significantly. Due to the increased overall diameter, the airflow in the cooling zone needed to be increased to maintain the spinneret shape.

[0066] In the coaxial composite extrusion process, the increase in the core layer ratio is not a static data change, but rather a change in material filling, cooling requirements, and traction control methods in the actual extrusion process.

[0067] 4. Structural evolution during the stretching stage Under Experiment A conditions, only a 2x stretch was applied. The increase in fiber length was limited, and the fiber surface maintained a certain degree of flexibility.

[0068] When switching to Experiment B, the draw ratio was increased to 4 times. During the draw process, the tension increased significantly, the fibers gradually became denser, and the surface smoothness improved.

[0069] Experiment C used a 6x draft. The increased draft zone length allowed the fibers to be fully straightened under high tension, resulting in a more regular axial structure. At this point, the winding tension needed to be adjusted synchronously; otherwise, shrinkage was likely to occur.

[0070] The three materials exhibited a progressively stronger orientation trend when placed in the same drawing device.

[0071] 5. Differences in crystal region formation during the heat setting stage Experiment A was heat-set at 110℃. The core layer formed a basic stereochemical composite crystalline region, and the structure tended to be stable.

[0072] Experiment B was increased to 135℃. Under the same time conditions, crystal regions formed more fully, and fiber rigidity increased.

[0073] Experiment C was shaped at 160℃. High temperature further improved the stereocomposite structure, making the internal structure of the fiber more compact.

[0074] As the temperature increases, the internal structure of the core layer changes from a relatively dispersed to a dense arrangement.

[0075] On the same production line, as the material parameters gradually transition from Experiment A to Experiment C, the processing load increases step by step, the melt state changes from a state with good fluidity to a state with high viscosity, the core layer ratio continues to expand, the tensile tension gradually increases, and the shaped structure gradually becomes denser.

[0076] By adjusting process parameters such as the mass ratio of poly-L-lactic acid to poly-D-lactic acid, molecular weight, particle size distribution, flow rate, and heat setting temperature, this embodiment achieves effective synergistic optimization of material properties and processing technology. With the increase of the core layer ratio, the increase of the draw ratio, and the increase of the heat treatment temperature, the mechanical properties, rigidity, and crystallinity of the fibers gradually improve, the shaped structure tends to be denser, and controllable degradation behavior is achieved. The above process adjustments provide an operable technical solution for the personalized customization of medical stents and have broad application potential.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A biodegradable medical scaffold fiber, characterized in that, Including a core layer and a sheath layer arranged coaxially: The core layer is composed of stereocomposite polylactic acid, which is formed by melt blending poly-L-lactic acid and poly-D-lactic acid, and the mass ratio of poly-L-lactic acid to poly-D-lactic acid is 45:55-55:

45. The sheath is composed of a biodegradable copolymer containing carbonate units, wherein the biodegradable copolymer is poly(lactic acid-trimethylene carbonate); A buffering and neutralizing component is dispersed within the sheath layer. The buffering and neutralizing component is a coated alkaline inorganic particle, which is composed of magnesium hydroxide and calcium carbonate. The coating layer of the coated alkaline inorganic particle is a biodegradable polymer. The mass fraction of the buffering and neutralizing component in the scaffold fiber is 0.3%-5.0%. The diameter of the core layer accounts for 70%-85% of the diameter of the scaffold fiber; the diameter of the scaffold fiber is 120μm-300μm.

2. The biodegradable medical scaffold fiber according to claim 1, characterized in that: The coating layer is polycaprolactone, and the thickness of the coating layer is 50nm-500nm; the D50 particle size of the coated alkaline inorganic particles is 0.2μm-5.0μm.

3. The biodegradable medical scaffold fiber according to claim 1, characterized in that: The content of the stereocomposite crystal region in the core layer is 30%-70%; the weight-average molecular weight of the core layer is 150k-350k.

4. The biodegradable medical scaffold fiber according to claim 1, characterized in that: The poly(lactic acid-trimethylene carbonate) contains 15%-55% molar fraction of trimethylene carbonate units; the sheath has a thickness of 10μm-80μm.

5. A method for preparing a biodegradable medical scaffold fiber, used to prepare a biodegradable medical scaffold fiber as described in any one of claims 1-4, characterized in that, include: S1. Poly-L-lactic acid and poly-D-lactic acid are dried and then melt-blended to obtain a core layer melt; S2. Using magnesium hydroxide particles and calcium carbonate particles as the core, a biodegradable polymer is used to form a coating layer to obtain coated alkaline inorganic particles. The coated alkaline inorganic particles are melt-blended with poly(lactic acid-trimethylene carbonate) to obtain a sheath melt. S3. The core melt and the sheath melt are fed into the coaxial composite spinneret assembly respectively, and the nascent fibers with a core-sheath coaxial structure are extruded simultaneously. S4. The nascent fibers are subjected to stretching and orientation treatment, and the stretched and oriented nascent fibers are subjected to heat treatment to shape them, so that the core layer forms a crystalline structure containing stereocomplex crystal regions, thereby obtaining shaped fibers. S5. Cool and wind up the shaped fiber to obtain medical biodegradable scaffold fiber.

6. The method for preparing a biodegradable medical scaffold fiber according to claim 5, characterized in that: The poly-L-lactic acid and the poly-D-lactic acid are vacuum dried separately before melt blending, until the water content is not higher than 200 ppm; the mass ratio of the poly-L-lactic acid to the poly-D-lactic acid is 45:55-55:

45.

7. The method for preparing a biodegradable medical scaffold fiber according to claim 5, characterized in that: The biodegradable polymer is polycaprolactone; the coating layer thickness is 50nm-500nm; and the D50 particle size of the coated alkaline inorganic particles is 0.2μm-5.0μm.

8. The method for preparing a biodegradable medical scaffold fiber according to claim 5, characterized in that: The coated alkaline inorganic particles and the poly(lactic acid-trimethylene carbonate) are melt-blended using a twin-screw extruder to uniformly disperse the coated alkaline inorganic particles in the sheath melt; the mass fraction of the coated alkaline inorganic particles in the medical biodegradable scaffold fiber is 0.3%-5.0%.

9. The method for preparing a biodegradable medical scaffold fiber according to claim 5, characterized in that: The core melt and the sheath melt are respectively metered and delivered to the coaxial composite spinneret by independent metering pumps; by setting the rotation speed of the core metering pump and the sheath metering pump, the volumetric flow rate ratio of the core and sheath is made to be 1.0-2.6, so that the core diameter accounts for 70%-85% of the scaffold fiber diameter; the scaffold fiber diameter is measured by an online diameter measuring device, and the traction speed is adjusted to make the scaffold fiber diameter 120μm-300μm.

10. The method for preparing a biodegradable medical scaffold fiber according to claim 5, characterized in that: The total draw ratio of the stretching and orientation treatment is 2.0-6.0; the heat treatment and shaping temperature is 110℃-160℃; after the heat treatment and shaping, the stereocomposite crystal region content of the core layer is 30%-70%; after cooling, it is wound with a constant winding tension to fix the orientation structure and crystal structure of the shaped fiber.

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