A porous self-expanding hydrogel vascular stent and a preparation method thereof

Abstract

This invention belongs to the field of medical device technology and discloses a porous self-expanding hydrogel vascular scaffold and its preparation method. The preparation method includes the following steps: Step 1: Coating a hydrogel solution onto the outer wall of a hollow inner tube of a mold; the hydrogel solution is obtained by dissolving hydrogel material in a solvent, and the volume concentration of the hydrogel material in the solvent is 10%~20%; Step 2: Injecting liquid nitrogen into the hollow structure of the inner tube, the liquid nitrogen creates a temperature gradient (lower inside, higher outside) on the hydrogel solution coated on the outer wall of the inner tube for directional freezing, followed by thawing and repeated freeze-thaw treatment; Step 3: Immersing the frozen inner tube in a salt solution for salting out, then immersing it in water, and finally demolding the hydrogel from the inner tube to obtain the porous self-expanding hydrogel vascular scaffold. The hydrogel vascular scaffold prepared by this method can maintain the necessary material exchange capacity while preventing cell infiltration and excessive growth of tissue inside the scaffold.

Description

Technical Field

[0001] This invention belongs to the field of medical device technology, specifically relating to a porous self-expanding hydrogel vascular stent and its preparation method. Background Technology

[0002] Currently, surgical intervention is a common and effective treatment for cardiovascular diseases, with percutaneous coronary intervention (PCI) being widely used in the treatment of coronary heart disease, myocardial infarction, and cardiovascular stenosis. Currently, vascular stents (especially drug-eluting stents or bare-metal stents) generally employ a mesh structure to facilitate stent compression, delivery, and expansion. However, this mesh structure has inherent structural defects: the pores in the mesh stent allow for the migration and excessive proliferation of vascular smooth muscle cells, easily leading to intimal hyperplasia within the stent, which in turn causes restenosis; in addition, the mesh structure can cause stress concentration, damaging the vessel wall and further contributing to restenosis. Although drug coatings can partially inhibit cell proliferation, in the long term, the mesh structure remains a significant structural factor inducing restenosis.

[0003] The applicant previously disclosed a hydrogel vascular stent (application number 202510643936.4), which employs a closed, non-porous tubular structure to physically prevent cell migration across the vessel wall, inhibit smooth muscle cell proliferation, and simultaneously distribute the stent's supporting force evenly across the vessel wall, thereby more effectively inhibiting in-stent restenosis. However, the applicant further discovered that a completely closed hydrogel stent can sever the small blood vessels (such as microvascular networks) that originally existed around the stent wall, leading to ischemia and hypoxia in the vessel wall tissue covered by the stent, interruption of nutrient supply, and ultimately inducing tissue necrosis or delayed healing. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a porous self-expanding hydrogel vascular stent, which can produce a self-expanding porous vascular stent. The special porous structure of the stent wall can, on the one hand, form a physical barrier to the trans-wall migration of host cells, and on the other hand, nourish the stent wall and the microvessels around the blood vessel, reducing the risk of restenosis.

[0005] This invention provides a method for preparing a porous self-expanding hydrogel vascular stent, the method comprising the following steps:

[0006] Step 1: Apply the hydrogel solution to the outer wall of the hollow inner tube of the mold; the hydrogel solution is obtained by dissolving the hydrogel material in a solvent, and the volume concentration of the hydrogel material in the solvent is 10%~20%;

[0007] Step 2: Inject liquid nitrogen into the hollow structure of the inner tube. The liquid nitrogen creates a temperature gradient with a lower temperature inside and a higher temperature outside on the hydrogel solution coated on the outer wall of the inner tube, causing directional freezing. Then, the tube is thawed and the freeze-thaw process is repeated.

[0008] Step 3: Soak the frozen inner tube in a saline solution for salting out, then soak it in water, and finally demold the hydrogel from the inner tube to obtain a porous self-expanding hydrogel vascular stent.

[0009] In some embodiments, the volume concentration of the hydrogel material in the solvent is 10% to 18%, preferably 10% to 16%, more preferably 13% to 16%, even more preferably 14% to 16%, and more preferably 14.5% to 15.5%.

[0010] In some embodiments, the hydrogel material comprises polyvinyl alcohol.

[0011] In some embodiments, the hydrogel material further includes polyethylene glycol, wherein the volume concentration of polyethylene glycol in the solvent is 10% to 15%.

[0012] In some embodiments, the solvent is PBS buffer.

[0013] In some embodiments, in step 3, the salt solution is at least one of sodium citrate solution, ammonium sulfate solution, sodium dihydrogen phosphate solution, sodium sulfate solution, aluminum chloride solution, aluminum sulfate solution, and magnesium chloride solution at a concentration of 1-10% v / v; preferably, the salt solution is a sodium citrate solution at a concentration of 2%-4% v / v.

[0014] And / or, in step 3, the salting-out treatment time is 12h~24h;

[0015] And / or, in step 3, the water soaking treatment time is 12h~24h;

[0016] And / or, in step 2, repeat the freeze-thaw process 2 to 4 times;

[0017] And / or, in step 2, the freezing time of the liquid nitrogen is 8 min to 15 min.

[0018] In some embodiments, the mold includes a base, an inner tube, and a protective sleeve;

[0019] The inner tube is detachably inserted into the base, and the protective sleeve is fitted onto the inner tube and detachably connected to the base, with a gap between the outer wall of the inner tube and the inner wall of the protective sleeve; the inner tube is made of a heat-conducting material and has a hollow structure, and the top of the protective sleeve has an injection port communicating with the hollow structure;

[0020] Preferably, the gap width between the inner tube and the protective sleeve is 0.3mm to 1.0mm;

[0021] And / or, the inner tube is a copper tube;

[0022] And / or, the base is a polytetrafluoroethylene base;

[0023] And / or, the protective sleeve is a polytetrafluoroethylene sleeve;

[0024] And / or, the upper end of the base is provided with a first positioning part, and the lower end of the protective sleeve is provided with a second positioning part, and the protective sleeve is connected to the base through the positioning cooperation of the second positioning part and the first positioning part.

[0025] This invention also provides a mold for preparing porous self-expanding hydrogel vascular stents, the mold comprising a base, an inner tube, and a protective sleeve;

[0026] The inner tube is detachably inserted into the base, and the protective sleeve is fitted onto the inner tube and detachably connected to the base, with a gap between the outer wall of the inner tube and the inner wall of the protective sleeve; the inner tube is made of a heat-conducting material and has a hollow structure, and the top of the protective sleeve has an injection port communicating with the hollow structure.

[0027] This invention also provides a porous self-expanding hydrogel vascular stent prepared by the method described above.

[0028] In some embodiments, the porous self-expanding hydrogel vascular stent is a hollow tube, the tube wall of which forms pores penetrating the inner and outer walls, and the pore diameter is 4μm~6μm.

[0029] In this invention, the method for preparing a hydrogel vascular scaffold using hydrogel materials involves a specific liquid nitrogen freezing treatment combined with a specific concentration of hydrogel material. Specifically, a hydrogel solution of a specific concentration is coated onto the outer wall of the inner tube of a mold, and liquid nitrogen is injected into the hollow structure of the inner tube. This creates a temperature gradient between the inner and outer sides of the hydrogel solution coated on the outer wall of the inner tube, achieving directional freezing. This process yields a hollow-tube hydrogel vascular scaffold with pores of 4μm to 6μm in diameter penetrating both the inner and outer walls. These pores are continuous channels that do not allow cells to pass through, effectively preventing transmembrane cell migration and allowing only small molecule nutrients such as oxygen, glucose, and amino acids, as well as metabolic waste, to diffuse freely. Therefore, the prepared hydrogel vascular scaffold can prevent cell infiltration and excessive tissue growth within the scaffold while maintaining necessary material exchange capacity, ensuring normal metabolism and survival of the blood vessels surrounding the scaffold after implantation, and providing excellent mechanical support. Attached Figure Description

[0030] Figure 1 This is a diagram of the mold structure and a flowchart of the preparation process using the mold, according to Embodiment 1 of the present invention.

[0031] Figure 2 This is a compression force diagram of hydrogel vascular stents prepared with different PVA concentrations in Example 1 of the present invention when the compression deformation reaches 70%.

[0032] Figure 3 This is a scanning electron microscope image of hydrogel vascular stents prepared with different PVA concentrations in Example 1 of the present invention (the samples were freeze-dried and fractured before being photographed; magnification 3k times).

[0033] Figure 4 These are fluorescence microscopy images of parallel sections of hydrogel vascular stents from the experimental and control groups.

[0034] Figure 5 These are scanning electron microscope (SEM) images of the surface and parallel plane of the hydrogel vascular stent in the experimental group.

[0035] Figure 6 The shape and diameter of the hydrogel vascular stent in the experimental group before and after swelling.

[0036] Figure 7 These are the compression curves and compressive forces of hydrogel vascular stents in different treatment groups when they are compressed to 70%.

[0037] Figure 8 This is a graph showing the results of 200 cycles of 70% compression experiments on the PVA-oriented / Salt group.

[0038] Figure 9 These are the results of compliance tests on blood vessels, drug-eluting stents, and various experimental groups.

[0039] Figure 10 The cell survival of HUVEC cells after culturing the extract for 1 and 3 days.

[0040] Figure 11 This represents the hemolysis rate of hydrogel vascular stents in different treatment groups.

[0041] Figure 12 These are HE staining results of vascular tissue after treatment with drug-eluting scaffolds and gel vascular scaffolds, respectively.

[0042] Figure 13 This is a picture of the finished hydrogel vascular stent prepared in Example 2.

[0043] Figure 14 The figures show the compression curves and compressive forces of hydrogel vascular stents prepared with 10% PVA and 15% PVA by volume when compressed to 70%.

[0044] Figure 15 This is a picture of the finished hydrogel vascular stent prepared in Example 3.

[0045] Figure 16 This is a structural schematic diagram of the mold in the assembled state according to an embodiment of the present invention.

[0046] Figure 17 This is a structural schematic diagram of the mold in its disassembled state according to an embodiment of the present invention.

[0047] Figure 18 This is a physical structural diagram of the mold for the comparative group of Example 1.

[0048] Explanation of reference numerals in the attached figures:

[0049] 100. Mold;

[0050] 1. Base; 11. First positioning part; 2. Inner tube; 21. Hollow structure; 3. Protective tube; 31. Injection port. Detailed Implementation

[0051] To facilitate understanding of the present invention, a more complete description will be provided below. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0052] Unless otherwise specified, experimental methods in the following examples are generally performed under standard conditions or as recommended by the manufacturer. All commonly used chemical reagents used in the examples are commercially available products.

[0053] Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used in this invention includes any and all combinations of one or more of the associated listed items.

[0054] This invention provides a method for preparing a porous self-expanding hydrogel vascular stent, the method comprising the following steps:

[0055] Step 1: Apply the hydrogel solution to the outer wall of the hollow inner tube of the mold; the hydrogel solution is obtained by dissolving the hydrogel material in a solvent, and the volume concentration of the hydrogel material in the solvent is 10%~20%;

[0056] Step 2: Inject liquid nitrogen into the hollow structure of the inner tube. The liquid nitrogen creates a temperature gradient with a lower temperature inside and a higher temperature outside on the hydrogel solution coated on the outer wall of the inner tube, causing directional freezing. Then, the tube is thawed and the freeze-thaw process is repeated.

[0057] Step 3: After repeated freeze-thaw cycles, the hydrogel is soaked in a salt solution for salting out, then soaked in water, and finally demolded from the inner tube to obtain the hydrogel tube.

[0058] In this invention, during the preparation method of hydrogel vascular stents using hydrogel materials, the inventors unexpectedly discovered that by using a specific liquid nitrogen freezing treatment method, combined with a specific concentration of hydrogel material—specifically, coating the outer wall of the inner tube 2 of the mold 100 with a hydrogel solution of a specific concentration, and injecting liquid nitrogen into the hollow structure 21 of the inner tube 2—a temperature gradient with a lower inner temperature and a higher outer temperature is formed on the hydrogel solution coated on the outer wall of the inner tube 2, achieving directional freezing, a hollow tube hydrogel vascular stent can be prepared. The hollow tube wall has pores with a diameter of 4μm~6μm penetrating both the inner and outer walls. These pores are continuous channels that do not allow cells to pass through, effectively preventing transmembrane cell migration and allowing only small molecule nutrients such as oxygen, glucose, and amino acids, as well as metabolic waste, to diffuse freely. Therefore, the prepared hydrogel vascular stent can maintain the necessary material exchange capacity while preventing cell infiltration and excessive growth of tissue inside the stent, ensuring normal metabolism and survival of the blood vessels around the stent after implantation, and possessing good mechanical support function.

[0059] This invention also provides a mold 100 for preparing porous self-expanding hydrogel vascular stents, such as... Figure 16 and Figure 17 As shown, the mold 100 includes a base 1, an inner tube 2, and a protective sleeve 3;

[0060] The inner tube 2 is detachably inserted into the base 1, and the protective sleeve 3 is fitted onto the inner tube 2 and detachably connected to the base 1, with a gap between the outer wall of the inner tube 2 and the inner wall of the protective sleeve 3. The inner tube 2 is made of a thermally conductive material and has a hollow structure 21, i.e., the inner tube 2 is a hollow tube. The top of the protective sleeve 3 is provided with an injection port 31 communicating with the hollow structure 21. When the mold 100 is used to prepare a porous self-expanding hydrogel vascular stent, after the hydrogel solution is coated on the outer wall of the inner tube 2, the inner tube 2 is assembled with the base 1 and the protective sleeve 3 to obtain a complete mold, and liquid nitrogen is injected into the hollow structure 21 of the inner tube 2 through the injection port 31 of the protective sleeve 3 for freezing treatment.

[0061] In some embodiments, the upper end of the base 1 is provided with a first positioning part 11, and the lower end of the protective sleeve 3 is provided with a second positioning part (not shown). The protective sleeve 3 is connected to the base 1 through the positioning engagement of the second positioning part and the first positioning part 11. The first positioning part 11 is an annular flange protruding upward from the upper end of the base 1, and the second positioning part is an annular groove formed by the recess at the lower end of the protective sleeve 3. The protective sleeve 3 is engaged with the flange through the groove for accurate positioning and connection to the base 1. Of course, the first positioning part 11 can also be a groove, and the second positioning part can also be a flange; no particular limitation is made here. In other embodiments, the first positioning part 11 and the second positioning part can also be other shaped mating structures, as long as the protective sleeve 3 can be accurately positioned and connected to the base 1; no particular limitation is made here.

[0062] Based on this mold, the preparation method of the porous self-expanding hydrogel vascular stent according to the present invention specifically includes the following steps:

[0063] Step 1: After applying the hydrogel solution to the outer wall of the inner tube 2, assemble the inner tube 2 with the base 1 and the protective sleeve 3 to obtain a complete mold 100;

[0064] Step 2: Inject liquid nitrogen into the hollow structure 21 of the inner tube 2 for freezing treatment, then thaw, and after repeated freeze-thaw cycles, remove the protective sleeve 3 from the mold 100 which is in a frozen state.

[0065] Step 3: Soak the mold 100 with the protective sleeve 3 removed in a salt solution for salting out, then soak it in water, and finally demold the hydrogel from the inner tube 2 to obtain the hydrogel tube.

[0066] The present invention will be described below with reference to specific embodiments.

[0067] Example 1

[0068] This embodiment provides a mold, such as Figure 16 and Figure 17 As shown, the mold 100 includes the following structure:

[0069] The mold 100 includes a base 1, an inner tube 2, and a protective sleeve 3. The inner tube 2 is a hollow copper tube, the base 1 is a polytetrafluoroethylene (PTFE) base, and the protective sleeve 3 is a PTFE sleeve. The inner tube 2 is detachably inserted into the base 1, and the protective sleeve 3 is fitted onto the inner tube 2 and detachably connected to the base 1, with a gap between the outer wall of the inner tube 2 and the inner wall of the protective sleeve 1. The inner tube 2 has a hollow structure 21, and the top of the protective sleeve 3 is provided with an injection port 31 communicating with the hollow structure 21.

[0070] This embodiment provides a method for preparing a porous self-expanding hydrogel vascular stent, using the aforementioned mold. Please refer to [reference needed]. Figure 1 Specifically, it includes the following steps:

[0071] Step 1: Dissolve polyvinyl alcohol (PVA) in PBS buffer at three concentrations of 5%, 15%, and 25% by volume, and stir at 80°C for 12 hours until fully dissolved to obtain a hydrogel solution.

[0072] Step 2: After applying the above hydrogel solution to the outer wall of the copper tube, assemble the inner tube with the base and protective sleeve to obtain a complete mold (the outer diameter of the copper rod is 2.5 mm, the inner diameter of the outer polytetrafluoroethylene sleeve is 3.1 mm, that is, the thickness of the vascular stent is 300 μm).

[0073] Step 3: Inject liquid nitrogen into the hollow structure of the inner tube for freezing treatment for 10 minutes, then thaw it at room temperature. Repeat the freeze-thaw cycle 3 times, and then remove the protective cover from the frozen mold.

[0074] Step 4: Immerse the mold, after removing the protective sleeve, in a 3% v / v sodium citrate solution for 12 hours. To visualize the pore structure, after soaking in sodium citrate, continue soaking in pure water containing rhodamine for another 12 hours, enabling it to emit stable orange-red fluorescence under excitation at a wavelength of 530-580 nm, facilitating subsequent fluorescence microscopy observation. Demold the hydrogel from the inner tube to obtain the hydrogel tube, which is the porous self-expanding hydrogel vascular stent (referred to as a hydrogel vascular stent).

[0075] The prepared hydrogel vascular scaffold was subjected to scanning electron microscopy (SEM) and mechanical tests. The pore structure of the hydrogel was observed using an SEM; its supporting force under 70% compression was tested using a universal tensile testing machine (MTS-C43.104). Figure 2 and Figure 3It is evident that when the PVA concentration is 5%, the pore size observed under a scanning electron microscope (SEM) (lyophilized and fractured before imaging; magnification 3kx) is too large, resulting in low supporting force when the compression deformation reaches 70%, and weak mechanical properties of the hydrogel vascular stent. While the mechanical properties are good when the PVA concentration is increased to 25 wt%, the high solution viscosity significantly inhibits polymer chain diffusion, hinders ice crystal growth, and makes it difficult to form continuous, regular through-channels during directional freezing. The pores often exhibit irregular, blocked, or branched defects, resulting in a sparse and irregular porous structure under the SEM. At a PVA concentration of 15%, the solution viscosity is moderate, allowing ice crystals to grow orderly and stably along the temperature gradient, forming uniform (approximately 5 μm) and regularly oriented through-channels with good mechanical properties. Therefore, considering both mechanical properties and the formation of porous structures, a PVA concentration of 15% is preferred.

[0076] A hydrogel vascular stent prepared using the preparation method of Example 1 with a PVA concentration of 15% was used as the experimental group. For comparison, a PVA concentration of 15% was coated onto a mold (a solid polytetrafluoroethylene rod structure) using a coating method. Figure 18 The hydrogel vascular stent was prepared as a control group after undergoing three freeze-thaw cycles at -80℃ and demolding.

[0077] The results were observed using an inverted fluorescence microscope on parallel sections (10 μm) of the hydrogel vascular stents from the experimental and control groups. Figure 4 As shown in the figure. The results show that the hydrogel vascular stent in the control group is disordered and isotropic, without a through-type orientation; while the hydrogel vascular stent in the experimental group has a clear directional arrangement on the parallel surfaces, with the channels regularly oriented along the freezing direction and the pores continuous. In addition, the inventors tried to coat 15% PVA onto the outer wall of a hollow copper rod and directly place the hollow copper rod in a liquid nitrogen environment for three freeze-thaw cycles. They found that the liquid nitrogen temperature was too low, and when it came into direct contact with the hydrogel, it would freeze rapidly to form large, sharp ice crystals, destroying the hydrogel structure and deteriorating its mechanical properties and structure, making it unsuitable for preparing hydrogel vascular stents.

[0078] Therefore, in the control group, even with the optimal 15% v / v PVA concentration, the conventional solid rod mold used for preparing hydrogel vascular stents prevented the formation of a temperature gradient (lower inside, higher outside) in the hydrogel solution, resulting in a non-directional porous structure. The internal structure of the hydrogel vascular stent was disordered and isotropic, lacking a through-hole orientation. Therefore, when preparing hydrogel vascular stents with the optimal 15% v / v PVA concentration, it is necessary to combine this specific mold structure with the directional introduction of liquid nitrogen into the hollow structure of the inner tube. This creates a temperature gradient (lower inside, higher outside) on the hydrogel solution coated on the outer wall of the inner tube, achieving directional freezing. Only then can a stent with pores penetrating both the inner and outer walls be prepared, resulting in a hydrogel vascular stent with a clearly directional arrangement of parallel planes, regular orientation of pores along the freezing direction, and continuous pores.

[0079] To further clarify the pore size, the hydrogel vascular stent in the experimental group was freeze-dried and then fractured in liquid nitrogen. Scanning electron microscopy (SEM) was performed at 3kx magnification. The results are as follows: Figure 5 As shown in the figure. The results indicate that the surface of the directional freezing group exhibits a porous structure of about 5 μm, while the parallel surfaces show a continuous structure arranged longitudinally, further demonstrating the successful construction of the porous structure.

[0080] To demonstrate that the hydrogel vascular stent in the experimental group could be delivered in a small size in a dry state and could support the blood vessel after swelling, the dimensions of the hydrogel vascular stent were measured before and after swelling. The dimensions of the hydrogel vascular stent were measured after drying, which is the size before swelling; the dimensions were measured after immersion in physiological saline until the weight remained constant, which is the size after swelling. The measurement results are as follows: Figure 6 As shown, the size of the dry hydrogel vascular stent is about 2.2 mm, which is relatively small and can be delivered to the target site through intervention. After swelling, the size of the vascular stent is about 3.5 mm, with a significantly increased diameter, which can provide support for the blood vessel.

[0081] To demonstrate the good mechanical properties of the hydrogel vascular stents in the experimental group, hydrogel vascular stents prepared by the non-directional PVA method (i.e., freeze-thawing with a solid rod mold at -80℃) (PVA group), hydrogel vascular stents prepared by the experimental group only through liquid nitrogen freeze-thaw treatment (PVA-directional group), and hydrogel vascular stents prepared by the experimental group through liquid nitrogen freeze-thaw treatment followed by sodium citrate treatment (PVA-directional / Salt group) were swelled to equilibrium. The compression curves and compressive forces of the vascular stents at 70% compression were measured using a universal testing machine at a compression rate of 1 mm / min. The results are as follows: Figure 7 As shown, Figure 7The results showed that, compared with the PVA group, the porous structure of the PVA-oriented group had no difference in supporting mechanical properties of the hydrogel, both reaching about 1.6 N; while the PVA-oriented / Salt group could enhance the mechanical properties of the hydrogel, reaching about 2.1 N.

[0082] To demonstrate the good fatigue resistance of this implementation, the PVA-oriented / Salt group was subjected to 200 cycles of 70% compression at a compression rate of 1 mm / min. The results are as follows: Figure 8 As shown, the results indicate that the compression curve of the hydrogel vascular stent did not decrease significantly within 200 cycles, indicating that the mechanical properties of the hydrogel vascular stent did not decrease significantly, proving that the hydrogel vascular stent in the PVA-directional / Salt group has good anti-fatigue properties.

[0083] Due to the excellent elasticity and deformation recovery ability of hydrogels, hydrogel vascular stents can adapt to the regular pulsation of blood vessels, thus exhibiting a certain degree of compliance. The hydrogel stent was fitted onto the tubing of a compliance testing instrument. The pressure was controlled at a low pressure of 80 mmHg and a high pressure of 120 mmHg by adjusting the peristaltic pump to simulate human blood pressure. Changes in the outer diameter of the vascular stent were recorded at both low and high pressure levels, and the hydrogel compliance was calculated. Three parallel samples were used in each group. The compliance calculation formula is as follows:

[0084]

[0085] Where: P1 is the low pressure value; P2 is the high pressure value; R P1 It is the inner diameter at low pressure; R P2 It is the inner diameter under high pressure.

[0086] The experiment used a pressure control system of 120 mmHg (high pressure) and 80 mmHg (low pressure) to simulate human blood pressure and characterize the compliance of vascular stents in the human body. Ideally, the compliance of a vascular stent should closely resemble that of a normal blood vessel. However, in practical applications, compliance is often sacrificed to achieve the supporting function of the stent. The compliance test results for the blood vessel, the drug-eluting stent (Abbott ABT-1120350), and each experimental group are shown below. Figure 9 The results show that, in this experiment, the normal blood vessel was the rabbit abdominal aorta, and its compliance was about 8.5% / 100 mmHg. The experimental group was lower than this, but it had a significant advantage compared with the drug-eluting stent.

[0087] Cell compatibility of hydrogel vascular scaffolds was assessed using a cell viability staining assay. Based on GB / T 16886.12-2023 "Biological Evaluation of Medical Devices Part 12: Sample Preparation and Reference Materials", the treated hydrogels were lyophilized and added to DMEM complete medium at a solid-liquid ratio of 0.2 g / mL. The mixture was then incubated at 37°C for 24 h with shaking during the incubation. After extraction, particulate matter was removed by filtration through a 0.22 μm filter to obtain the hydrogel extract. Endothelial cells (HUVECs) were seeded at a density of 15,000 cells / well in 24-well plates and cultured in DMEM complete medium. After cell attachment, the normal medium was removed, and the cells were cultured in the hydrogel extract for 1 and 3 days. Calcein / PI working solution was prepared and stored in the dark. The medium was removed, the cells were washed once with PBS, and 300 μL of Calcein / PI working solution was added to each well. The cells were incubated for 20 min, and the working solution was removed after incubation. Finally, the images were observed and photographed using an inverted fluorescence microscope. Each group had three replicates, and the operation was carried out in the dark. Figure 10 The image shows the cell viability of HUVEC cells after culturing in the extract for 1 and 3 days. Live cells exhibit green fluorescence, while dead cells show red fluorescence. HUVEC cells exhibit distinct morphological characteristics under in vitro culture conditions: in the early stages of adherent growth, cells are round or oval; as cells proliferate, they gradually extend into short spindle-shaped or polygonal forms; when cells contact each other and connect into sheets, they exhibit a "cobblestone" appearance, with cells closely packed together. At day 1 of culture, both the control group and the extract group showed short spindle-shaped cells; at day 3 of culture, both the control group and the extract group showed a cobblestone-like appearance, indicating normal cell morphology. Furthermore, the extract group showed less red fluorescence (i.e., fewer dead cells), indicating that the growth and proliferation of HUVEC cells were not affected.

[0088] The hemocompatibility of the hydrogel was tested using a hemolysis test. The experimental method was as follows: Fresh rabbit blood was placed in an anticoagulant tube containing sodium heparin, centrifuged at 1000 rpm for 10 min to separate red blood cells, washed with PBS, centrifuged again, and the process was repeated three times to obtain a 5% red blood cell volume fraction solution. Following GB / T 14233.1-2008 "Specific Operation of Hemolysis Test", the hydrogel vascular stent was immersed in the red blood cell solution at a solid-liquid ratio of 0.2 g / mL. Triton X-100 was used as a positive control, and PBS as a negative control. The experiment was incubated at 37℃ with shaking for 1 hour. After incubation, the sample was centrifuged at 1000 rpm for 10 min, and the supernatant was added to a 96-well plate. The absorbance at 540 nm was measured, and the hemolysis rate was calculated. Three parallel samples were set up for each experimental group. The calculation basis for the hemolysis rate is as follows:

[0089]

[0090] Among them, A s It is the absorbance of the experimental group; A t This is the absorbance of the positive control; A b This is the absorbance of the negative control.

[0091] The absorbance was measured using an ELISA reader, and the hemolysis rate of the hydrogel was calculated. The results are as follows: Figure 11 As shown, the hemolysis rate of each group of hydrogels is less than 5%, which meets the standard of GB / T 16886.4-2022 "Biological evaluation of medical devices - Part 4: Selection of blood interaction tests", indicating that the hydrogel vascular stent has good blood compatibility and can be safely used in relevant biomedical applications.

[0092] To characterize the biocompatibility and vascular patency of the hydrogel vascular stent in animals, in vivo vascular stent implantation experiments were conducted on healthy male New Zealand white rabbits (3 months old, weighing 2.5–3 kg). Rabbits were randomly divided into two groups (n=6 per group): a drug-eluting stent group (Abbott ABT-1120350) and a PVA-directed / Salt stent group, with the drug-eluting stent group serving as the control group. Before the experiment, the hydrogel vascular stent was immersed in 75% ethanol at 37°C and sterilized by UV irradiation for 12 hours. The hydrogel vascular stent was first adhered to an inflatable balloon using gelatin. Rabbits were given general anesthesia (25 mg / mL, 0.7 ml / kg) and injected with sodium pentobarbital via the ear vein. Subsequently, the femoral artery was isolated to an appropriate length (3 cm), and the hydrogel vascular stent was delivered from the femoral artery to the abdominal aorta via a balloon. The hydrogel vascular stent was delivered to the target vessel location via interventional procedures, and the balloon was inflated and held for 1 minute. Finally, the balloon was deflated and withdrawn after separation from the hydrogel vascular stent. After balloon withdrawal and artery ligation, animals received an intramuscular injection of ampicillin sodium solution (10 mg / mL, 1 ml / kg). Additionally, they were administered aspirin (100 mg / kg) and clopidogrel (3 mg / kg) for three consecutive days following stent implantation. One month after implantation, aortic tissue from the stent site was removed, and the rabbits were euthanized using an excess of pentobarbital sodium solution. The collected stent-treated aortic tissue was stained with hematoxylin and eosin (HE). Results are as follows. Figure 12 As shown, the results indicate that the vascular tissue in the drug-eluting stent group showed significant proliferation in the open areas of the mesh structure, while the vascular tissue in the hydrogel vascular stent group did not show significant proliferation. This suggests that the closed structure of the hydrogel vascular stent can prevent cell migration through physical barrier action, thereby inhibiting proliferation and reducing the risk of in-stent restenosis.

[0093] Example 2

[0094] This study prepared a self-expanding, closed hydrogel vascular stent with a porous structure using polyvinyl alcohol (PVA). The specific steps included are as follows:

[0095] Step 1: Dissolve 10% PVA in PBS buffer and stir at 80°C for 12 hours until fully dissolved to obtain a hydrogel solution;

[0096] Step 2: After applying the above hydrogel solution to the outer wall of the copper tube, assemble the inner tube with the base and protective sleeve to obtain a complete mold (the outer diameter of the copper rod is 2.5 mm, the inner diameter of the outer polytetrafluoroethylene sleeve is 3.1 mm, that is, the thickness of the vascular stent is 300 μm).

[0097] Step 3: Inject liquid nitrogen into the hollow structure of the inner tube for freezing treatment for 10 minutes, then thaw it at room temperature. Repeat the freeze-thaw cycle 3 times, and then remove the protective cover from the frozen mold.

[0098] Step 4: Soak the mold with the protective sleeve removed in a 3% v / v sodium citrate solution for 24 hours, then soak it in pure water for another 12 hours. Demold the hydrogel from the inner tube to obtain the hydrogel vascular stent.

[0099] The prepared hydrogel vascular stents, such as Figure 13 As shown in the left figure, a porous, self-expanding hydrogel vascular scaffold was successfully fabricated. To evaluate the toughness of the PVA hydrogel vascular scaffold, a torsion operation was performed on it. The results are as follows: Figure 13 The middle image shows that the hydrogel vascular scaffold exhibits excellent flexibility and maintains its integrity during torsion. Scanning electron microscopy was used to evaluate the pore structure of the PVA hydrogel vascular scaffold. The results are as follows: Figure 13 As shown in the right figure, the diameter of the hole is approximately 5 μm.

[0100] The hydrogel vascular stent prepared with a volume fraction of 10% PVA was further tested using a universal tensile testing machine (MTS-C43.104) with a deformation set to 70%. Its supporting force under 70% compression was measured. The results were compared with the mechanical properties of the hydrogel vascular stent prepared with a volume fraction of 15% PVA in Example 1. Figure 14 As shown, the hydrogel vascular stent prepared with 10% PVA has less supporting force and slightly weaker mechanical properties compared to the hydrogel vascular stent prepared with 15% PVA, but it still meets the mechanical requirements of hydrogel vascular stents.

[0101] Example 3

[0102] This study prepared a self-expanding, closed hydrogel vascular stent with a porous structure using polyvinyl alcohol (PVA) and polyethylene glycol (PEG). The specific steps included are as follows:

[0103] Step 1: Dissolve 15% PVA and 15% PEG in PBS buffer according to volume fraction, stir at 80°C for 12 hours until fully dissolved, and obtain hydrogel solution;

[0104] Step 2: After applying the above hydrogel solution to the outer wall of the copper tube, assemble the inner tube with the base and protective sleeve to obtain a complete mold (the outer diameter of the copper rod is 2.5 mm, the inner diameter of the outer polytetrafluoroethylene sleeve is 3.1 mm, that is, the thickness of the vascular stent is 300 μm).

[0105] Step 3: Inject liquid nitrogen into the hollow structure of the inner tube for freezing treatment for 10 minutes, then thaw it at room temperature. Repeat the freeze-thaw cycle 3 times, and then remove the protective cover from the frozen mold.

[0106] Step 4: Soak the mold with the protective sleeve removed in a 7% ammonium sulfate solution for 16 hours, then soak it in pure water for another 12 hours. Demold the hydrogel from the inner tube, and finally cut it to 5.5 mm to obtain the hydrogel vascular stent. Figure 15 ).

[0107] The results of Example 3 show that when using the optimal concentration of 15% PVA as the hydrogel material to prepare hydrogel vascular stents, auxiliary components such as polyethylene glycol can be added, and porous, self-expanding hydrogel vascular stents can still be successfully prepared. To evaluate the pore structure of the hydrogel vascular stent, scanning electron microscopy was used to image it. The results are as follows... Figure 15 As shown in the right figure, the diameter of the hole is approximately 5 μm.

[0108] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0109] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a porous self-expanding hydrogel vascular stent, characterized in that, The preparation method includes the following steps: Step 1: Apply the hydrogel solution to the outer wall of the hollow inner tube of the mold; the hydrogel solution is obtained by dissolving the hydrogel material in a solvent, and the volume concentration of the hydrogel material in the solvent is 10%~20%; Step 2: Inject liquid nitrogen into the hollow structure of the inner tube. The liquid nitrogen creates a temperature gradient with a lower temperature inside and a higher temperature outside on the hydrogel solution coated on the outer wall of the inner tube, causing directional freezing. Then, the tube is thawed and the freeze-thaw process is repeated. Step 3: Soak the frozen inner tube in a saline solution for salting out, then soak it in water, and finally demold the hydrogel from the inner tube to obtain a porous self-expanding hydrogel vascular stent.

2. The preparation method according to claim 1, characterized in that, The volume concentration of the hydrogel material in the solvent is 10% to 16%, preferably 14% to 16%.

3. The preparation method according to claim 2, characterized in that, The hydrogel material includes polyvinyl alcohol.

4. The preparation method according to claim 3, characterized in that, The hydrogel material also includes polyethylene glycol, wherein the volume concentration of polyethylene glycol in the solvent is 10% to 15%.

5. The preparation method according to any one of claims 1-4, characterized in that, The solvent is PBS buffer.

6. The preparation method according to any one of claims 1-4, characterized in that, In step 3, the salt solution is at least one of the following: sodium citrate solution, ammonium sulfate solution, sodium dihydrogen phosphate solution, sodium sulfate solution, aluminum chloride solution, aluminum sulfate solution, and magnesium chloride solution, at a concentration of 1-10% v / v. And / or, in step 3, the salting-out treatment time is 12h~24h; And / or, in step 3, the water soaking treatment time is 12h~24h; And / or, in step 2, repeat the freeze-thaw process 2 to 4 times; And / or, in step 2, the freezing time of the liquid nitrogen is 8 min to 15 min.

7. The preparation method according to any one of claims 1-4, characterized in that, The mold includes a base, an inner tube, and a protective sleeve; The inner tube is detachably inserted into the base, and the protective sleeve is fitted onto the inner tube and detachably connected to the base, with a gap between the outer wall of the inner tube and the inner wall of the protective sleeve; the inner tube is made of a heat-conducting material and has a hollow structure, and the top of the protective sleeve has an injection port communicating with the hollow structure; Preferably, the gap width between the inner tube and the protective sleeve is 0.3mm to 1.0mm; And / or, the inner tube is a copper tube; And / or, the base is a polytetrafluoroethylene base; And / or, the protective sleeve is a polytetrafluoroethylene sleeve; And / or, the upper end of the base is provided with a first positioning part, and the lower end of the protective sleeve is provided with a second positioning part, and the protective sleeve is connected to the base through the positioning cooperation of the second positioning part and the first positioning part.

8. A mold for preparing porous self-expanding hydrogel vascular stents, characterized in that, The mold includes a base, an inner tube, and a protective sleeve; The inner tube is detachably inserted into the base, and the protective sleeve is fitted onto the inner tube and detachably connected to the base, with a gap between the outer wall of the inner tube and the inner wall of the protective sleeve; the inner tube is made of thermally conductive material and has a hollow structure, and the top of the protective sleeve has an injection port communicating with the hollow structure.

9. The porous self-expanding hydrogel vascular stent prepared by the method of any one of claims 1-7.

10. The porous self-expanding hydrogel vascular stent as described in claim 9, characterized in that, The porous self-expanding hydrogel vascular stent is a hollow tube, and the tube wall forms pores that penetrate the inner and outer walls, with the pore diameter being 4μm~6μm.

Images