Shape memory intravascular stent with body temperature recovery function and preparation method

Abstract

The invention discloses a shape memory intravascular stent capable of body temperature recovery and a preparation method thereof, and the preparation method comprises the following steps: drying polylactic acid granules, adding PEG for toughening, carrying out melt blending, adding polylactic acid fibers as a reinforcing phase, and carrying out screw extrusion to obtain a composite material. The toughness of the shape memory material is improved, the shape recovery temperature of the shape memory material is reduced, and shape recovery under the human body temperature is achieved. The intravascular stent is prepared through 3D printing, and the prepared shape memory intravascular stent has good recovery rate and fixation rate, lower recovery temperature and good biocompatibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of intelligent response materials, and relates to a shape memory material and a preparation method and application thereof, and in particular to a shape memory vascular stent capable of recovering to body temperature and a preparation method thereof. Background Art

[0002] Shape memory polymers can be given a temporary shape after applying appropriate stimuli, such as heat, electricity, magnetism, light, water, or pH changes. After the external stimulus is removed, the shape memory polymer is fixed in the temporary shape. When the polymer is stimulated again, the fixed temporary shape spontaneously returns to its original shape without the action of external forces. This process is the macroscopic shape memory effect. This shape memory polymer has shown great application potential in biomedicine, engineering machinery, flexible robots, wearable devices and other fields, and is one of the new materials with broad application prospects in the future. Polylactic acid, as a shape memory polymer, has good biocompatibility, but PLA shape memory materials currently have problems such as high shape recovery temperature, low shape recovery rate, and slow shape recovery speed, which cannot meet the application requirements of vascular stents. Summary of the Invention

[0003] In order to improve the shape memory performance of polylactic acid shape memory materials and reduce the shape memory temperature, the present application provides a PLA / PEG / polylactic acid fiber shape memory material and a preparation method, and prepares a shape memory vascular stent by 3D printing.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] A method for preparing a shape-memory vascular stent that can recover to body temperature comprises the following steps: drying PLA, melt-blending it with PEG, then adding polylactic acid fiber as a reinforcing phase and melt-blending it, and using screw extrusion to obtain a filament for 3D printing, and using 3D printing to obtain a vascular stent that can achieve shape memory at "human body temperature".

[0006] Preferably, the mass fractions of PLA, PEG, and polylactic acid fiber are 90-100 parts, 3-10 parts, and 0-10 parts, respectively;

[0007] Preferably, the molecular weight of the polyethylene glycol is 400 to 1000, the length of the polylactic acid fiber is 30 to 50 mm, and the diameter is 0.001 to 0.003 mm;

[0008] Preferably, the polylactic acid pellets are dried in an oven at 60-80° C. for 6-8 hours; PLA is melt-blended for 2-3 minutes, PEG is added and melt-blended for 2-3 minutes, and polylactic acid fibers are added and melt-blended for 1-2 minutes. The processing temperature is 180-200° C., the speed during melt blending is 60-80 rpm, and the time is 5-8 minutes to obtain the shape memory material.

[0009] Preferably, the blend after melt blending and kneading is added to a single screw extruder at a temperature of 170 to 180° C. and is pulled at a constant speed to obtain a 3D printing wire with a diameter of 1.7 to 1.8 mm.

[0010] The present invention provides a method for printing a vascular stent, comprising the following steps:

[0011] Drawing a three-dimensional model of the vascular stent on software such as Solidworks, and printing the vascular stent model using the extruded wire;

[0012] Preferably, the hot bed temperature is 50-60° C., the printing temperature is 180-200° C., and the printing speed is 80-100 mm / min.

[0013] The beneficial effects of the present invention are:

[0014] The present invention effectively lowers the glass transition temperature of PLA by adding PEG, thereby reducing the material's shape memory recovery temperature to human body temperature while simultaneously increasing its shape recovery rate. Furthermore, the addition of polylactic acid fiber as a reinforcement effectively increases the material's shape retention rate, thereby enhancing the material's overall shape memory properties. The material also exhibits good biocompatibility, facilitating its application. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 DSC curves of Examples 1 to 6 and Comparative Example 1;

[0016] Figure 2 The storage modulus curves of Examples 1 to 6 and Comparative Example 1;

[0017] Figure 3 The relative cell viability of Examples 1 to 6 and Comparative Example 1;

[0018] Figure 4 The shape fixation rate and shape recovery rate of Examples 1 to 6 and Comparative Example 1;

[0019] Figure 5 This is the shape memory process of the shape memory 3D printed vascular stent in Example 4. DETAILED DESCRIPTION

[0020] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments so as to fully understand the purpose, characteristics and effects of the present invention.

[0021] The molecular weight of the polyethylene glycol used in the embodiments of the present invention is 400-1000, the length of the polylactic acid fiber is 30-50 mm, and the diameter is 0.001-0.003 mm. In the present invention, the glass transition temperature of the composite material is lowered by using low-molecular-weight polyethylene glycol, thereby achieving shape recovery through "human body temperature." In addition, experiments have found that the lower the molecular weight of the polyethylene glycol, the better the compatibility, the increased toughness of the composite material, the faster the molecular chain flow rate, the improved shape recovery rate, and the only slight decrease in the shape fixation rate (<4%); adding a polylactic acid fiber reinforcement phase can further improve the shape memory fixation rate of the PLA / PEG composite material, and can achieve a fixation rate that is basically the same as that of pure polylactic acid.

[0022] Example 1

[0023] 97 parts by weight of polylactic acid pellets were dried in an oven at 80°C for 8 hours, added to an internal mixer, and mixed for 3 minutes. 3 parts of polyethylene glycol were added and mixed for 2 minutes at a temperature of 180°C and a speed of 80 rph to obtain a shape memory blend.

[0024] The mixed blend was added to a single-screw extruder at 175°C, 180°C, and 165°C, respectively, and a 1.75mm diameter 3D printing filament was obtained by pulling at a constant speed.

[0025] A three-dimensional model of the vascular stent was drawn on Solidworks software, and the obtained wire was used to 3D print the vascular stent model at a temperature of 180° C. and a printing speed of 100 mm / min to obtain the shape-memory vascular stent.

[0026] Example 2

[0027] 95 parts by weight of polylactic acid pellets were dried in an oven at 80°C for 8 hours, added to an internal mixer, and mixed for 3 minutes. 5 parts of polyethylene glycol were added and mixed for 2 minutes at a temperature of 180°C and a rotation speed of 80 rph to obtain a shape memory blend.

[0028] The mixed blend was added to a single-screw extruder at 175°C, 180°C, and 165°C, respectively, and a 1.75mm diameter 3D printing filament was obtained by pulling at a constant speed.

[0029] A three-dimensional model of the vascular stent was drawn on Solidworks software, and the obtained wire was used to 3D print the vascular stent model at a temperature of 180° C. and a printing speed of 100 mm / min to obtain the shape-memory vascular stent.

[0030] Example 3

[0031] 93 parts by weight of polylactic acid pellets were dried in an oven at 80°C for 8 hours, added to an internal mixer, and mixed for 3 minutes. 7 parts of polyethylene glycol were added and mixed for 2 minutes at a temperature of 180°C and a rotation speed of 80 rph to obtain a shape memory blend.

[0032] The mixed blend was added to a single-screw extruder at 175°C, 180°C, and 165°C, respectively, and a 1.75mm diameter 3D printing filament was obtained by pulling at a constant speed.

[0033] A three-dimensional model of the vascular stent was drawn on Solidworks software, and the obtained wire was used to 3D print the vascular stent model at a temperature of 180° C. and a printing speed of 100 mm / min to obtain the shape-memory vascular stent.

[0034] Example 3

[0035] 90 parts by weight of polylactic acid pellets were dried in an oven at 80°C for 8 hours, added to an internal mixer, and mixed for 3 minutes. 10 parts of polyethylene glycol were added and mixed for 2 minutes at a temperature of 180°C and a rotation speed of 80 rph to obtain a shape memory blend.

[0036] The mixed blend was added to a single-screw extruder at 175°C, 180°C, and 165°C, respectively, and a 1.75mm diameter 3D printing filament was obtained by pulling at a constant speed.

[0037] A three-dimensional model of the vascular stent was drawn on Solidworks software, and the obtained wire was used to 3D print the vascular stent model at a temperature of 180° C. and a printing speed of 100 mm / min to obtain the shape-memory vascular stent.

[0038] Example 5

[0039] 90 parts by weight of polylactic acid pellets were dried in an oven at 80°C for 8 hours, added to an internal mixer, and mixed for 3 minutes. 10 parts of polyethylene glycol were added and mixed for 2 minutes. 3 parts of polylactic acid fibers were added and mixed for 1 minute at a temperature of 180°C and a rotation speed of 80 rph to obtain a shape memory blend.

[0040] The mixed blend was added to a single-screw extruder at 175°C, 180°C, and 165°C, respectively, and a 1.75mm diameter 3D printing filament was obtained by pulling at a constant speed.

[0041] A three-dimensional model of the vascular stent was drawn on Solidworks software, and the obtained wire was used to 3D print the vascular stent model at a temperature of 180° C. and a printing speed of 100 mm / min to obtain the shape-memory vascular stent.

[0042] Example 6

[0043] 90 parts of polylactic acid pellets, by weight, were dried in an oven at 80°C for 8 hours, added to an internal mixer, and mixed for 3 minutes. 10 parts of polyethylene glycol were added and mixed for 2 minutes. 10 parts of polylactic acid fibers were added and mixed for 1 minute at a temperature of 180°C and a rotation speed of 80 rph to obtain a shape memory blend.

[0044] The mixed blend was added to a single-screw extruder at 175°C, 180°C, and 165°C, respectively, and a 1.75mm diameter 3D printing filament was obtained by pulling at a constant speed.

[0045] A three-dimensional model of the vascular stent was drawn on Solidworks software, and the obtained wire was used to 3D print the vascular stent model at a temperature of 180° C. and a printing speed of 100 mm / min to obtain the shape-memory vascular stent.

[0046] Comparative Example 1

[0047] 100 parts by weight of polylactic acid pellets were dried in an oven at 80° C. for 8 h, added to an internal mixer, and mixed for 5 min at a temperature of 180° C. and a rotation speed of 80 rph to obtain a polylactic acid shape memory material.

[0048] The mixed blend was added to a single-screw extruder at 175°C, 180°C, and 165°C, respectively, and a 1.75mm diameter 3D printing filament was obtained by pulling at a constant speed.

[0049] A three-dimensional model of the vascular stent was drawn on Solidworks software, and the obtained wire was used to 3D print the vascular stent model at a temperature of 180° C. and a printing speed of 100 mm / min to obtain the shape-memory vascular stent.

[0050] Table 1 T of different composite materials g and T m

[0051] sample <![CDATA[T g ]]> <![CDATA[T m ]]> Example 1 54.50 167.77 Example 2 48.41 168.33 Example 3 41.27 165.66 Example 4 39.98 166.14 Example 5 39.51 166.38 Example 6 37.55 165.29 Comparative Example 1 61.53 166.76

[0052] Table 1 shows the T of different composite materials g and T m ,Depend on Figure 1 As can be seen, the melting temperature of the shape memory composite material remains unchanged at around 168°C, while the glass transition temperature gradually decreases with increasing PEG content, reaching a minimum of 39.98°C with 10% PEG and further decreasing to 37.55°C with the addition of 10% polylactic acid fiber. Therefore, the shape recovery temperature also decreases with increasing PEG content.

[0053] Depend on Figure 2 It can be seen that all blends experience a decrease in storage modulus of about one order of magnitude, indicating that the materials have certain shape memory properties. The storage modulus of pure PLA is much higher than that of PLA / PEG blends because the stiffness of PLA is reduced by blending with PEG. As the PEG content increases, the T g It shows a downward trend, indicating that the compatibility of PLA / PEG is improved, the toughness is improved, and the content of flexible segments of the molecular chain increases with the increase of PEG content. Their possible plasticizing effect will also lead to the T g of reduction.

[0054] Figure 3 For CCK8 cytotoxicity testing of PLA / PEG composites, relative cell viability was measured at 1, 4, and 7 days, and the overall cell viability of the composites was approximately 80%. Increasing the PEG content from 3% to 10% resulted in a slight decrease in cell viability because PEG may form steric hindrance on the cell surface or between cell-associated biomolecules (such as proteins) within a short period of time. This steric hindrance may hinder normal cell interactions with external substances, thereby affecting cell metabolism and function, leading to decreased cell viability. Over time, cell viability increased in most composites because this effect is transient and reversible, and cells gradually recover and enhance their activity through their own adaptive mechanisms. The addition of polylactic acid fibers slightly increased relative cell viability. The fiber structure mimics the microenvironment of the extracellular matrix, providing cells with growth conditions closer to physiological conditions and better support. It also increases the material's porosity and specific surface area, facilitating cell adhesion and nutrient exchange, creating growth conditions closer to physiological conditions.

[0055] Shape memory test

[0056] The shape memory performance of shape memory composites can be tested by the shape memory cycle method, using the shape fixation rate R f , shape recovery rate R rTwo parameters are used to characterize its shape memory performance. The sample with the size of 20mm×5mm×1mm is heated in a water bath. g +10℃) to give the sample an initial shape, and after cooling to room temperature, the temporary shape is obtained. Then the sample is heated to the deformation temperature (T g +10℃), observe and record the shape memory behavior of the samples.

[0057]

[0058] Where: θ0 is the sample temperature at programming temperature (i.e. T g +10℃) after being bent into a U shape and then cooled to room temperature under external force;

[0059] θ1 is the temporary shape angle obtained after removing the external force;

[0060] θ2 is the angle at which the material recovers its shape memory when it is reheated to the programmed temperature without external force.

[0061] Table 2 Shape fixation rate and shape recovery rate of different composite materials

[0062] sample Shape fixation rate % Shape recovery rate% Example 1 97.8 95 Example 2 96.9 96.8 Example 3 96 97.4 Example 4 95.9 99 Example 5 96.5 98.5 Example 6 98.4 98.6 Comparative Example 1 99 88

[0063] Table 2 shows the shape fixation rate and shape recovery rate of different composite materials. Figure 4 It can be seen that the overall shape fixation rate of the composite material is about 96%. Compared with pure polylactic acid, after toughening with PEG, the fixation rate gradually decreases, and the shape recovery rate increases to more than 90%. As the PEG content increases to 10%, the fixation rate is as low as 95.9% and the shape recovery rate is as high as 99%. When 10% polylactic acid fiber is added, the fixation rate increases to 98.4% and the shape recovery rate is 98.6%.

[0064] like Figure 5 It can be seen that a vascular stent model of 90% PLA / 10% PEG / 10% polylactic acid fiber shape memory composite material was prepared by fused deposition 3D printing, and the shape memory performance of the model was tested, which included four processes in sequence: initial shape, shape imparting, shape fixing, and shape recovery.

[0065] This specific embodiment is merely an explanation of the present invention and is not intended to limit the present invention. After reading this specification, those skilled in the art may make non-creative modifications to this embodiment as needed. However, as long as such modifications are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A method for preparing a shape memory vascular stent capable of recovering to body temperature, characterized in that: By weight, 90-100 parts of polylactic acid (PLA), 3-10 parts of polyethylene glycol (PEG) are used as raw materials, and 0-10 parts of polylactic acid fiber are added. After the PLA is dried, it is melt-blended with PEG, and then the polylactic acid fiber is added as a reinforcement phase for melt-blending. Screw extrusion is used to obtain the wire for 3D printing, and 3D printing is used to obtain a vascular stent that can achieve shape memory at "human body temperature".

2. The method for preparing a shape memory vascular stent capable of recovering to body temperature as claimed in claim 1, characterized in that: The molecular weight of the polyethylene glycol is 400-1000, the length of the polylactic acid fiber is 30-50 mm, and the diameter is 0.001-0.003 mm.

3. The method for preparing a shape memory vascular stent capable of recovering to body temperature as claimed in claim 1, characterized in that: PLA is melt-blended for 2 to 3 minutes, PEG is then added and melt-blended for 2 to 3 minutes, and polylactic acid fiber is then added and melt-blended for 1 to 2 minutes. The processing temperature is 180 to 200° C., the speed during melt-blending is 60 to 80 rpm, and the time is 5 to 8 minutes.

4. The method for preparing a shape memory vascular stent capable of recovering to body temperature as claimed in claim 1, wherein: The melt-blended blend is added to a single-screw extruder at a temperature of 170-180° C. and is pulled at a constant speed to obtain a 3D printing wire with a diameter of 1.7-1.8 mm.

5. The method for preparing a shape memory vascular stent capable of recovering to body temperature as claimed in claim 1, characterized in that: The prepared 3D printing filament is 3D printed according to the designed vascular stent three-dimensional model, with a hot bed temperature of 50-60°C, a printing temperature of 180-200°C, and a printing speed of 80-100 mm / s.

6. A shape memory vascular stent capable of recovering to body temperature, characterized in that: The method is prepared by the method according to any one of claims 1 to 5.

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