Multifunctional intracranial stent for time sequence drug controlled release and preparation method thereof

Abstract

The application provides a time-sequential drug controlled-release multifunctional intracranial stent and a preparation method, relates to the technical field of vascular stents, and comprises a stent base made of a Fe-based metal material; and, from inside to outside on the surface of the stent base, a bottom coating layer composed of iron oxide nanotubes, wherein the surface of the iron oxide nanotubes is modified by polydopamine and loaded with rapamycin; a middle coating layer formed by the complex of beta-rich silk fibroin and sodium heparin; and a surface coating layer formed by the complex of silk fibroin and edaravone; wherein the setting positions of the surface coating layer, the middle coating layer and the bottom coating layer correspond to the time sequence of drug release in each coating layer, so that the corresponding drugs are released at different stages after the stent base is placed in a blood vessel, so as to adapt to the pathological evolution process in the blood vessel repair process. The application solves the problems of cerebral ischemia-reperfusion injury and vascular restenosis after the current vascular stent is placed in a cerebral blood vessel.

Description

Technical Field

[0001] This application relates to the field of vascular stent technology, and in particular to a time-controlled drug release multifunctional intracranial stent and its preparation method. Background Technology

[0002] With the development of neurointerventional techniques, vascular stents are increasingly being used to treat cerebrovascular diseases such as carotid artery, vertebral artery, and intracranial vascular stenosis. However, after a stent is placed in a cerebral vessel, restenosis may occur during the blood flow restoration process, and rapid reperfusion may also cause cerebral ischemia-reperfusion injury, thus affecting the treatment outcome. Drug-eluting stents are currently an important device in interventional treatment of vascular stenosis. By loading and releasing anti-proliferative drugs on the stent surface, the risk of restenosis can be reduced. These drug-eluting stents are mainly used in cardiovascular fields such as coronary arteries and have achieved good clinical results.

[0003] However, cerebrovascular and cardiovascular vessels differ significantly in anatomical structure and pathophysiological characteristics. Existing drug-eluting stents are mostly designed specifically for cardiovascular applications, focusing only on the two major complications of restenosis and late-stage thrombosis, neglecting the issue of cerebral ischemia-reperfusion injury after recanalization. Furthermore, the drug components loaded onto the stents are singular, and their drug release behavior cannot match the pathological process of restenosis, failing to consider the specific temporal functional requirements of the stent during diseased vessel repair and endothelial tissue regeneration. Summary of the Invention

[0004] To address the aforementioned problems, one objective of this invention is to provide a time-controlled drug-release multifunctional intracranial stent to solve the issues of cerebral ischemia-reperfusion injury and restenosis that commonly occur after implantation of current vascular stents used in cerebrovascular interventions. A second objective of this invention is to provide a method for preparing a time-controlled drug-release multifunctional intracranial stent. A third objective of this invention is to provide an application of this time-controlled drug-release multifunctional intracranial stent.

[0005] To achieve one of its objectives, in a first aspect, the present invention provides a time-controlled drug release multifunctional intracranial stent, the technical solution of which is: A time-controlled drug release multifunctional intracranial stent, comprising: The scaffold matrix is ​​made of a biodegradable material, which includes at least an Fe-based metal material; And the following coatings are applied sequentially from the inside to the outside on the surface of the support substrate: The bottom coating is composed of iron oxide nanotubes, the surface of which is modified with polydopamine and loaded with rapamycin. The middle coating is formed by a complex of β-structure-rich silk fibroin and sodium heparin. The surface coating is formed by a complex of silk fibroin and edaravone. The positions of the top coating, the middle coating, and the bottom coating correspond to the drug release sequence in each coating, so that the corresponding drugs are released at different stages after the stent matrix is ​​placed into the blood vessel, in order to adapt to the pathological evolution process during the vascular repair process.

[0006] As one preferred embodiment, the iron oxide nanotubes are prepared by anodizing, the preparation method including: The Fe-based metal material is placed in an electrolyte; the electrolyte comprises NH4F, water, and ethylene glycol. The scaffold substrate is anodized using the electrolyte to form iron oxide nanotubes on the outer surface of the scaffold substrate. During the anodizing process, the voltage is 100V-220V, the treatment temperature is 20℃-50℃, and the treatment time is 1h-3h.

[0007] As one preferred embodiment, the rapamycin in the underlying coating is loaded onto the iron oxide nanotubes by the following method: Rapamycin solution was prepared by dissolving the rapamycin in acetone; the concentration of rapamycin in the rapamycin solution was 1 mg / mL-5 mg / mL. The scaffold matrix on which the iron oxide nanotubes are formed is placed in a vacuum environment, and the rapamycin solution is dropped onto the iron oxide nanotubes so that the rapamycin is uniformly loaded on the surface of the iron oxide nanotubes; during the vacuum dropping process, the dropping time is 0.5h-1h.

[0008] As one of the preferred solutions, the intermediate coating is prepared by the following method: The silk fibroin solution was degummed and purified by dialysis, and the β-structure content was adjusted to make the silk fibroin solution rich in β-structure. A plasticizer is added to the silk fibroin solution and mixed with an aqueous heparin sodium solution to form a composite sol; The composite sol is coated onto the surface of the bottom layer using the sol-gel method, and then crosslinked in an ethanol-water mixed solution, followed by drying to form the middle layer coating.

[0009] As one preferred embodiment, the plasticizer comprises 5%-10% glycerol.

[0010] As one of the preferred embodiments, the surface coating is prepared by the following method: A silk fibroin solution is mixed with an edaravone solution; wherein the silk fibroin solution contains 2wt%-4wt% of silk fibroin and the edaravone solution contains 0.5mg / mL-2mg / mL of edaravone. The resulting mixed solution was coated onto the surface of the intermediate coating using the sol-gel method and dried at 40℃-60℃ for 2h-4h to form the bottom coating.

[0011] As one of the preferred embodiments, the thicknesses of the bottom coating, the middle coating, and the top coating are 10μm-100μm, respectively.

[0012] As one of the preferred options, the strength of the support matrix is ​​700MPa-1000MPa.

[0013] To achieve the second objective, the present invention provides a method for preparing a time-controlled drug release multifunctional intracranial scaffold, the technical solution of which is: A method for preparing a time-controlled drug release multifunctional intracranial stent according to a first aspect of the present invention includes the following steps: S1. Select Fe-based metal material as the scaffold matrix, and grow iron oxide nanotubes on the surface of the scaffold matrix by anodizing. S2. The iron oxide nanotubes are modified with polydopamine, and rapamycin is loaded onto the iron oxide nanotubes by vacuum drop addition to form an underlayer coating on the surface of the scaffold matrix. S3. Prepare a composite sol composed of β-rich silk fibroin and sodium heparin, coat the composite sol onto the surface of the bottom coating, crosslink and dry to form a middle coating on the bottom coating. S4. Prepare a silk fibroin / edaravone composite solution, coat the silk fibroin / edaravone composite solution onto the surface of the intermediate coating layer, and after drying, form a top coating layer on the intermediate coating layer.

[0014] To achieve the third objective, the present invention provides the application of the time-controlled drug release multifunctional intracranial stent as provided in the first aspect of the present invention in the treatment of cerebral vascular stenosis, so as to reduce cerebral restenosis and cerebral ischemia-reperfusion injury.

[0015] Compared with the prior art, this application has the following advantages: This implementation involves applying three different drug coatings—a surface layer, a middle layer, and a bottom layer—to the stent matrix from the outside in. Edaravone, heparin sodium, and rapamycin are released in an approximately sequential order after stent placement. The surface layer releases edaravone rapidly during the acute phase to reduce the risk of cerebral ischemia-reperfusion injury; the middle layer releases heparin sodium continuously during the subacute phase to reduce the risk of thrombosis; and the bottom layer releases rapamycin slowly during the chronic phase to reduce the risk of restenosis. This approach matches the drug release sequence with the cerebrovascular injury and repair process, enabling targeted treatment using neurointerventional techniques.

[0016] The method and application described herein have the same advantages as the aforementioned stent over the prior art, and will not be repeated here. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this application, the drawings used in the description of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a SEM image of iron oxide nanotubes grown on a Fe-based metal surface according to an embodiment of this application; wherein, a is a local detail image at a magnification of 1um, b is a local detail image at a magnification of 400nm, and c is a pore size identification image of the iron oxide nanotubes when b is further magnified to 100nm. Figure 2 This is an SEM image provided by an embodiment of the present application after a middle layer coating and a top layer coating are sequentially coated on a bottom layer coating; wherein, a is a local detail image at a magnification of 10um after coating the middle layer coating, b is a local detail image when a is further magnified to 5um, c is a local detail image at a magnification of 10um after coating the top layer coating, d is a local detail image when c is further magnified to 500nm, and e is a pore size identification image of iron oxide nanotubes when d is further magnified to 200nm; Figure 3 These are photographs showing the activity of nerve cells on the bottom layer, middle layer, and top layer coating, respectively, according to an embodiment of this application. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] Before providing a detailed description of the time-controlled drug release multifunctional intracranial stent, its preparation method, and its applications provided by this invention, it is necessary to explain the relevant technologies as follows.

[0021] Stroke is the leading cause of death and disability, and has become one of the major killers threatening human health. Ischemic stroke accounts for 60% to 70% of all strokes, and approximately 70% of ischemic stroke patients also have varying degrees of carotid atherosclerotic stenosis and occlusion. The traditional standard treatment for carotid artery stenosis is carotid endarterectomy (CEA). With the development of endovascular interventional techniques, carotid angioplasty and stenting (CAS) has become another key and effective technique for secondary prevention of acute ischemic stroke after CEA, which can reduce the risk of ischemic stroke in patients with symptomatic and asymptomatic cerebrovascular stenosis. Compared with CEA, CAS is simpler to perform, does not require general anesthesia, has a shorter postoperative recovery time, and avoids complications such as nerve damage, wound infection, and neck hematoma associated with carotid artery incision.

[0022] With the development of endovascular interventional techniques, cerebral vascular stents (such as carotid artery stents, vertebral artery stents, and intracranial vascular stents) have been widely used in the treatment of cerebral vascular stenosis. However, clinical practice shows that even if stent placement successfully restores blood flow, patients still face the challenge of various postoperative complications. Among the more prominent issues are cerebral ischemia-reperfusion injury caused by blood flow restoration and restenosis following stent placement.

[0023] To address the problem of restenosis, drug-eluting stents have been developed. However, current drug-eluting stents used in cerebrovascular fields are largely based on cardiovascular stent systems in terms of design concepts and technology. These stents primarily function to inhibit restenosis and prevent late-stage thrombosis, without addressing the issue of cerebral ischemia-reperfusion injury after recanalization. Furthermore, existing stents use a very limited variety of drugs, and their drug release behavior (mostly short-term rapid release or long-term uniform sustained release) is difficult to match with the development of restenosis, nor does it adequately consider the temporal demands of stent function during vascular repair and endothelial regeneration.

[0024] Therefore, designing a multifunctional intracranial vascular stent capable of targeted drug release at different stages, which can reduce the risk of cerebral ischemia-reperfusion injury after cerebral vascular stent placement, effectively inhibit vascular restenosis, and match the drug release process with the vascular repair and endothelial regeneration process, is of urgent and important significance for comprehensively improving the safety, effectiveness and long-term efficacy of neurointerventional therapy.

[0025] This application aims to design a novel drug-coated stent suitable for cerebrovascular stenosis, thereby addressing many problems raised in the background art. This invention provides a time-controlled drug-release multifunctional intracranial stent, comprising: The scaffold matrix is ​​made of Fe-based biodegradable metal material; The bottom coating consists of iron oxide nanotubes with polydopamine-modified surfaces and loaded with rapamycin, which are then coated onto the surface of the scaffold substrate. The middle coating, composed of β-structure-rich silk fibroin and sodium heparin, is applied to the surface of the bottom coating. The surface coating is composed of silk fibroin and edaravone and is applied to the surface of the middle coating. The placement and release sequence of the top, middle, and bottom coatings correspond to each other, allowing them to be released at different stages after the stent matrix is ​​placed into the blood vessel, thereby matching the pathological process of restenosis and cerebral ischemia-reperfusion injury.

[0026] Specifically, the stent matrix is ​​made of Fe-based biodegradable metallic material. Biodegradable metallic materials undergo slow corrosion and degradation in the human physiological environment, thus maintaining early mechanical support of the blood vessel while gradually degrading in later stages, which is beneficial for the recovery of vascular structure and physiological function. This invention constructs a surface-middle-bottom gradient coating structure on the stent matrix. In this gradient coating structure, the drug selection, carrier design, and placement of each layer are highly matched to the pathophysiological evolution (acute phase, subacute phase, chronic phase) after cerebral vascular stent placement.

[0027] Specifically, the surface coating includes edaravone. At the moment of cerebral recanalization, the most pressing threat to brain tissue is ischemia-reperfusion injury. Edaravone, as a free radical scavenger, must rapidly reach an effective concentration within hours post-procedure. Therefore, loading edaravone onto the outermost layer of the scaffold matrix allows it to be the first to contact and release from the intravascular blood environment after scaffold placement, thus rapidly exerting its free radical scavenging and neuroprotective effects in the acute phase after cerebral recanalization, providing immediate protection for brain tissue. Furthermore, because the surface coating is located on the outermost side of the scaffold, the drug release process is not hindered by other coating structures, particularly by the obstruction and degradation lag of the silk fibroin β-sheet conformation in the middle coating. This ensures that the release rate of edaravone responds rapidly within the "golden time" for brain tissue rescue, effectively reducing the risk of cerebral ischemia-reperfusion injury and preventing irreversible damage to nerve cells.

[0028] Specifically, the middle coating includes sodium heparin. After cerebral vascular stent placement, the vascular endothelium has not yet fully repaired within days to weeks following the acute phase, at which time thrombosis is the primary clinical risk. Sodium heparin has anticoagulant and antithrombotic effects, maintaining a local anticoagulant environment during the subacute phase. Therefore, by loading sodium heparin into a middle coating composed of β-rich silk fibroin, a balanced barrier can be formed with the β-sheet structure of silk fibroin, allowing sodium heparin to be gradually released during the mid-stage after stent placement. This allows edaravone to be released during the acute phase and then continue to exert its anticoagulant and antithrombotic effects during the critical subacute phase. Furthermore, since the middle coating is also exposed to the vascular environment after the surface coating has been released, the release activity of sodium heparin is not shielded by other undegraded coating structures; that is, it is not limited by the dense nanotube structure in the bottom coating, nor by the nearly fully released surface coating, allowing the release rate of sodium heparin to respond rapidly to antithrombotic effects.

[0029] Specifically, the bottom coating consists of iron oxide nanotubes modified with polydopamine and loaded with rapamycin. Restenosis typically occurs several months post-procedure due to excessive smooth muscle cell proliferation. Rapamycin, a potent anti-proliferative drug, delays endothelial repair. Therefore, rapamycin is loaded onto the innermost layer of the stent matrix, utilizing the high specific surface area and tubular structure of iron oxide nanotubes for drug loading. Simultaneously, polydopamine modification enhances the binding stability between rapamycin and iron oxide nanotubes, allowing for slow release of rapamycin over a longer period. This sustained inhibition of abnormal smooth muscle cell proliferation during the chronic phase after stent placement reduces the probability of restenosis. Furthermore, the middle and top coatings act as barriers in the early and mid-stages, preventing premature release that could interfere with endothelial cell climbing and coverage, thus preventing long-term endothelialization of the stent surface and increasing the risk of late-stage thrombosis.

[0030] In summary, this approach employs three drug-eluting coatings with distinct functions—top, middle, and bottom layers—and releases edaravone, heparin sodium, and rapamycin sequentially at different stages after stent placement, almost in a sequential order. The top layer releases edaravone rapidly during the acute phase to reduce the risk of cerebral ischemia-reperfusion injury; the middle layer releases heparin sodium continuously during the subacute phase to reduce the risk of thrombosis; and the bottom layer releases rapamycin slowly during the chronic phase to reduce the risk of restenosis. This ensures that the drug release sequence matches the cerebrovascular injury and repair process, achieving targeted treatment through neurointerventional techniques. Because the Fe-based material gradually releases iron ions during degradation, it helps promote local tissue metabolism and repair. Furthermore, its relatively slow degradation rate provides stable mechanical support throughout different stages of vascular repair. Additionally, the Fe-based material readily allows for the formation of iron oxide nanotube structures on its surface and can be modified with polydopamine, ensuring the bonding stability between the bottom layer coating and the stent matrix. Therefore, combining Fe-based biodegradable metal scaffold matrix with multilayer drug-eluting structure enables the scaffold to exert synergistic effects of structural support and drug therapy in multiple stages after implantation, thereby further improving the safety and long-term efficacy of cerebrovascular stent interventional therapy.

[0031] It is understood that the drug release kinetics time-series curve of the surface-middle-bottom gradient coating structure provided in this embodiment of the invention highly overlaps with the pathological evolution process after the stent matrix is ​​placed into the blood vessel. Different drugs in the surface, middle, and bottom coatings have different primary release phases over time, but the release of the next layer does not begin only after the previous layer's drug release or after the previous layer's release is complete. Instead, it exhibits a phased release characteristic with a temporal gradient. For example, the drug release processes between different layers overlap to some extent in time, but overall, the outermost layers, dominated from the outside in, have a higher release rate and preferentially reach effective concentrations, while the drugs in the innermost layers gradually enter the primary release phase.

[0032] For example, the drug release kinetic time-series curve can be specifically represented as follows: First time period: Postoperative acute phase (0-24 hours) Matching mechanism: Within minutes to hours after stent placement and blood flow restoration, brain tissue faces a peak of ischemia-reperfusion injury. At this time, a large number of free radicals are produced, and nerve cells face necrosis caused by oxidative stress.

[0033] Release sequence: The outermost surface coating (silk fibroin / edaravone) is released preferentially, reaching 40%-50% within 6 hours post-surgery and over 70% within 24 hours. At this time, the middle and bottom coatings are in an "induction period" with low-level release due to the influence of the high β-sheet structure and nanotube physical barrier.

[0034] Release characteristics: Utilizing a low concentration of silk fibroin with a mass fraction of 2wt%-4wt% and a rapid hydration rate, edaravone is ensured to reach an effective therapeutic concentration in the early stages of injury, minimizing cerebral edema and neurological deficits.

[0035] Second time period: Postoperative subacute period (1-14 days) Matching mechanism: During the time period after stent placement, the vascular endothelium is in the inflammatory response phase after damage, and the adsorption of proteins on the stent surface can easily induce acute or subacute thrombosis.

[0036] Release sequence: The middle coating layer (beta-rich silk fibroin / heparin sodium) located in the middle position enters a stable release period. Heparin sodium is released cumulatively by about 45%-50% within 3 days after surgery, and the total release reaches 80% around day 14. At this time, the bottom coating layer is still in the "induction period" with low-level release due to the influence of the physical barrier of nanotubes.

[0037] Release characteristics: The degradation rate of silk fibroin is controlled by a moderate amount (about 45%-55%) of β-sheet structure, which allows heparin sodium to act continuously on the blood vessel wall, prevent thrombus adhesion caused by endothelial loss, and smoothly transition to the initial endothelial coverage period.

[0038] The third time period: the postoperative chronic period (14 days to more than 6 months). Matching mechanism: Starting 2 weeks post-surgery, vascular smooth muscle cells (VSMCs) begin to proliferate excessively and migrate toward the intima, which is the root cause of restenosis.

[0039] Release timing: The bottom layer coating (iron oxide nanotubes / rapamycin) achieves "deep sustained release" under the combined constraint of polydopamine (PDA) and the upper residual structure.

[0040] Release sequence: Rapamycin releases only about 40% in the first 24 hours after surgery (drug accumulates at the tube opening), about 60% in the third day after surgery, and then enters a very slow release phase, continuing to release for 28 days or even longer.

[0041] Release characteristics: Rapamycin's "late-stage release" pattern avoids interference with early endothelial repair, ensuring that during the peak of smooth muscle proliferation (chronic remodeling period), there is still a sufficient concentration of rapamycin locally to inhibit the division of VSMCs, thereby reducing the restenosis rate in the later postoperative period.

[0042] As a further illustration of this embodiment, iron oxide nanotubes are prepared by anodizing. The preparation method includes: placing Fe-based metal material into an electrolyte; the electrolyte consists of NH4F, water, and ethylene glycol; anodizing the scaffold substrate with the electrolyte to form iron oxide nanotubes on the outer surface of the scaffold substrate; during the anodizing process, the voltage is 100V-220V, the treatment temperature is 20℃-50℃, and the treatment time is 1-3h.

[0043] In this embodiment, iron oxide nanotubes are prepared by anodizing. Specifically, a scaffold substrate made of Fe-based biodegradable metal material is placed in an electrolyte as the anode electrode, and an inert metal electrode is set as the cathode electrode. The electrolyte is a mixed solution composed of NH4F, water, and ethylene glycol. During the anodizing process, a voltage of 100V-220V, preferably 150V-170V, is applied to the scaffold substrate, and the reaction system temperature is controlled within the range of 20℃-50℃ for 1h-3h. Under these conditions, an ordered iron oxide nanotube structure gradually forms on the surface of the Fe-based material under the synergistic effect of electrochemical oxidation and fluoride ion etching. The formed iron oxide nanotubes have a large specific surface area and good surface roughness, which is beneficial for subsequent polydopamine modification and rapamycin loading, thereby improving the bonding stability between the underlying coating and the scaffold substrate and providing effective storage space for rapamycin.

[0044] Furthermore, by adjusting the anodizing voltage, processing time, and reaction temperature, the diameter, length, and packing density of the iron oxide nanotubes can be controlled. This anodizing process enables the construction of stable iron oxide nanotube structures on the surface of Fe-based scaffolds.

[0045] As a further illustration of this embodiment, rapamycin in the bottom coating is loaded onto iron oxide nanotubes by the following method: Rapamycin solution was prepared by dissolving rapamycin in acetone; the concentration of rapamycin in the rapamycin solution was 1 mg / mL-5 mg / mL; the scaffold matrix with iron oxide nanotubes was placed in a vacuum environment, and the rapamycin solution was dropped onto the iron oxide nanotubes to uniformly load rapamycin on the surface of the iron oxide nanotubes; the dropping time during the vacuum dropping process was 0.5 h-1 h.

[0046] In this embodiment, rapamycin in the undercoat is loaded onto the surface of the iron oxide nanotube structure via a vacuum drop method. Specifically, rapamycin is first dissolved in acetone to prepare a rapamycin solution with a concentration of 1 mg / mL to 5 mg / mL. Acetone has good volatility and solubility, which allows rapamycin to dissolve fully and form a uniform and stable solution, thus facilitating the uniform distribution of the drug on the nanostructure surface. Subsequently, the scaffold substrate with the iron oxide nanotube structure formed on its surface is placed in a vacuum environment, and the rapamycin solution is slowly added dropwise to the surface of the iron oxide nanotube structure over a time controlled between 30 and 60 minutes. Under the negative pressure created by the vacuum environment, the rapamycin solution can penetrate more fully into the internal pores and surface structure of the nanotubes during the dropwise process, thereby improving the drug loading efficiency and uniformity. As the acetone solvent gradually evaporates, rapamycin is deposited and fixed in the inner wall and surface microstructure of the iron oxide nanotubes, thus obtaining a stable undercoat layer attached to the innermost layer of the scaffold substrate.

[0047] Furthermore, by controlling the concentration of the rapamycin solution and the dropping time, the loading amount of rapamycin in the iron oxide nanotube structure can be adjusted. This vacuum dropping loading method allows rapamycin to be uniformly distributed within the iron oxide nanotube structure, further ensuring the slow release of rapamycin during the chronic phase to reduce the risk of restenosis.

[0048] As a further illustration of this embodiment, the silk fibroin / heparin sodium intermediate coating is prepared by the following method: First, the silk fibroin is degummed and purified by dialysis to obtain a silk fibroin solution, and the treatment conditions are adjusted to make the silk fibroin solution rich in β-structure; then, glycerol is added to the silk fibroin solution as a plasticizer, with the glycerol content being 5%-10% based on the mass of the silk fibroin solution, and mixed with heparin sodium aqueous solution to form a composite sol; the composite sol is coated onto the surface of the bottom coating using the sol-gel method, and cross-linked in an ethanol-water mixed solution, followed by drying to form a silk fibroin / heparin sodium composite coating rich in β-structure.

[0049] In this embodiment, the intermediate coating is a silk fibroin / heparin sodium composite coating, which is constructed on the surface of the underlying coating via a sol-gel method. Specifically, the natural silk fibroin is first degummed to remove impurities such as sericin. The degummed silk fibroin is further purified by dialysis to remove small molecule impurities and residual salts, thereby obtaining a purified silk fibroin solution. Subsequently, by adjusting the solution treatment conditions, the content of β-sheet structures in the silk fibroin molecular structure is increased, thereby forming a β-structure-rich silk fibroin solution. β-structure-rich silk fibroin has better structural stability and film-forming properties, which is beneficial for forming a dense and stable coating structure, and can also balance the release rate and timing of the subsequently added heparin sodium.

[0050] Subsequently, glycerol was added to the silk fibroin solution. Glycerol can improve the flexibility of the silk fibroin coating, reduce the risk of cracking during stent expansion or vascular deformation, and thus improve the mechanical stability of the coating. Heparin sodium aqueous solution was then added and mixed to ensure uniform dispersion of heparin sodium in the silk fibroin sol system, thereby forming a silk fibroin / heparin sodium composite sol. Heparin sodium, as an anticoagulant, can be continuously released during the mid-stage after stent placement to exert anticoagulant and antithrombotic effects.

[0051] Next, the silk fibroin / heparin sodium composite sol was coated onto the surface of the scaffold substrate with the pre-formed undercoat using a sol-gel method. The composite sol gradually gelled on the surface of the undercoat. Subsequently, the scaffold coated with the intermediate layer was placed in an ethanol-water mixture for cross-linking treatment, thereby forming a uniformly covered intermediate layer. After cross-linking, the scaffold was dried to remove residual solvent and further stabilize the coating structure, thus forming a stable silk fibroin / heparin sodium composite coating. This intermediate layer can also act as a diffusion barrier to some extent, regulating the release rate of rapamycin from the underlying layer, thereby further realizing the time-sequential release function of the multilayer drug coating.

[0052] As a further illustration of this embodiment, the silk fibroin / edaravone surface coating is prepared by the following method: a silk fibroin solution and an edaravone solution are mixed, wherein the mass fraction of silk fibroin in the silk fibroin solution is 2wt%-4wt%, and the concentration of edaravone in the edaravone solution is 0.5mg / mL-2mg / mL; the resulting mixed solution is coated onto the surface of the intermediate coating using the sol-gel method, and dried at 40℃-60℃ for 2h-4h to form a silk fibroin / edaravone composite coating.

[0053] In this embodiment, the surface coating is a silk fibroin / edaravone composite coating, which is constructed on the surface of the intermediate coating using a sol-gel method. Specifically, a silk fibroin solution is first prepared, wherein the mass fraction of silk fibroin in the solution is controlled between 2wt% and 4wt%. Within this mass percentage range, the silk fibroin solution exhibits good flowability and film-forming properties, enabling the formation of a continuous and uniform coating without excessively high viscosity affecting coating uniformity due to excessive concentration. Subsequently, edaravone is dissolved in a suitable solvent to form an edaravone solution, which is then mixed with the silk fibroin solution to uniformly disperse edaravone in the silk fibroin sol system. The concentration of edaravone is controlled within the range of 0.5 mg / mL to 2 mg / mL. Within this concentration range, sufficient drug content in the surface coating is ensured. Glycerin can be added as a plasticizer during the mixing process to obtain a composite sol, which is then coated onto the surface of the scaffold with the intermediate coating formed using a sol-gel method, ensuring that the composite sol uniformly covers the outer side of the intermediate coating. Subsequently, the coated stent was dried at 40℃-60℃ for 2-4 hours. Under these conditions, the solvent in the sol-gel system gradually evaporates, thereby immobilizing edaravone within the silk fibroin matrix and forming a stable surface coating. Since the surface coating is located on the outermost side of the stent, it is the first to come into contact with the blood environment after stent placement, allowing for rapid release of edaravone in the early stages. This helps to eliminate free radicals generated during ischemia-reperfusion, reduce oxidative stress damage to brain tissue, and exert an acute-phase neuroprotective effect. Simultaneously, this surface coating does not significantly hinder the subsequent release of drugs from the middle and bottom layers, thus forming a multilayer drug coating system with sequential release characteristics together with the middle layer heparin sodium and the bottom layer rapamycin.

[0054] As a further explanation of this embodiment, the thicknesses of the undercoat, intermediate coating, and topcoat are 10 μm-100 μm, respectively. By controlling the thicknesses of the undercoat, intermediate coating, and topcoat within the range of 10 μm-100 μm, not only can a uniform and stable coverage structure be formed on the scaffold surface by each coating layer, but sufficient drug loading space can also be provided, and the diffusion rate of the drug in each coating layer can be regulated to a certain extent, thereby facilitating the sequential release of edaravone, heparin sodium, and rapamycin. In addition, within this thickness range, each coating layer can still maintain good flexibility and adhesion stability, thereby adapting to the deformation requirements of the scaffold during placement and expansion, thus improving the reliability of the overall coating structure.

[0055] The coating thickness can be controlled by adjusting corresponding process parameters, including drug solution concentration, number of coating passes, and coating time. This embodiment does not limit this aspect.

[0056] As a further explanation of this embodiment, the strength of the stent matrix is ​​700MPa-1000MPa. By controlling the strength of the stent matrix within the range of 700MPa-1000MPa, the stent can possess both good radial support performance and maintain appropriate flexibility and expandability after placement, thereby better adapting to the physiological environment of cerebral blood vessels. Furthermore, within this strength range, the degradation rate of the Fe-based material in vivo is well-matched with the vascular tissue repair process, which is beneficial for the gradual degradation and absorption of the stent after the vascular endothelium gradually recovers, thus reducing the potential risks associated with long-term foreign body residue.

[0057] In summary, the time-sequential multifunctional gradient drug controlled-release coating structure constructed in the embodiments of the present invention has the following advantages: It can controllably release different drug molecules in stages, effectively reducing postoperative cerebral ischemia-reperfusion injury and lowering the in-stent restenosis rate.

[0058] By regulating the size (diameter and length) of the matrix micro-nano structure, the structural composition of silk fibroin, and the content of drug molecules, a phased and time-controlled release of different drug molecules that match the pathological process at the site of action can be achieved, thus achieving both neuroprotective effects and reducing the rate of cerebral restenosis.

[0059] Silk fibroin exhibits good biocompatibility and low immunogenicity, and is an FDA-approved non-toxic and non-irritating material. It demonstrates good drug loading stability, allowing for stable drug loading through covalent bonding, physical adsorption, and encapsulation. Its degradation rate is controllable, adjustable by regulating the content of the Silk II structure (antiparallel β-sheet conformation). The degradation products are safe and non-toxic, avoiding inflammatory reactions caused by existing polymer carriers. It is highly processable, capable of being formulated into microspheres, microcapsules, membranes, fibers, and other shapes. Furthermore, it possesses excellent mechanical properties, with an ultimate tensile strength up to 500 MPa and an elastic modulus of 5 GPa-12 GPa.

[0060] It can effectively reduce or lower the complications associated with stent intervention in patients with symptomatic and asymptomatic cerebral vascular stenosis, and further reduce the risk of ischemic stroke.

[0061] Based on traditional polymeric drug sustained-release systems, neuroprotective drug molecules are introduced to reduce intravascular restenosis rates. Combined with a time-dependent coating that closely approximates the pathological process at the site of action, this reduces cerebral ischemia-reperfusion injury, further improving the safety and efficacy of stent placement for the treatment of acute ischemic cerebrovascular disease.

[0062] Correspondingly, in a second aspect, the present invention also provides a method for preparing a time-controlled drug release multifunctional intracranial stent, used to prepare the time-controlled drug release multifunctional intracranial stent provided in the first aspect of the present invention, the method comprising the following steps: S1. The Fe-based metal scaffold substrate was cleaned, and iron oxide nanotubes were grown on its surface using anodizing. Iron-based alloys were selected as experimental materials, and were ultrasonically cleaned and dried with acetone and ethanol before use. Anodizing was performed using a mixed electrolyte solution of NH4F, water, and ethylene glycol. During the anodizing process, the voltage was controlled at 150V-170V, the adjustment time was 1h-3h, and the temperature was 20℃-50℃. Iron oxide nanotubes with specific structures and properties were then prepared on the scaffold substrate.

[0063] S2. The surface of iron oxide nanotubes was modified with polydopamine, and rapamycin was loaded onto the nanotubes using a vacuum drop method to obtain the bottom coating. The surface of iron oxide nanotubes was modified with polydopamine, and then rapamycin was dissolved in acetone. The concentration of rapamycin was controlled at 1 mg / mL-5 mg / mL. The rapamycin solution was added to the surface of the modified iron oxide nanotubes by vacuum drop method. During the drop process, an appropriate amount of solution was added first, and after the solvent was completely evaporated, the drop was continued. The drop time was 30 min-60 min until the required drug loading was achieved.

[0064] S3. Prepare a β-structure-rich composite sol, coat it onto the surface of the bottom coating layer, crosslink it, and dry it to obtain the middle coating layer. Degumme the silk fibroin and dialysis it. The size of the silk fibroin nanofibers is controlled by adjusting the degumming temperature (60℃-80℃) and time (30min-120min), the molecular weight cutoff of the dialysis membrane, the subsequent concentration time, and the reaction temperature and time to prepare a β-structure-rich silk fibroin solution. Add an appropriate amount of glycerol as a plasticizer, with the amount of glycerol added being 5%-10% based on the mass of the β-structure-rich silk fibroin solution. Mix the heparin sodium aqueous solution with the silk fibroin solution evenly to obtain a composite sol. Apply the composite sol to the surface of the scaffold treated in step S2 using the solvogel method, and then immerse it in an ethanol aqueous solution for crosslinking for several minutes. After crosslinking, dry it in an oven.

[0065] S4. Prepare a silk fibroin / edaravone composite solution, coat it onto the surface of the intermediate coating layer, and dry it to form a time-gradient drug-controlled release coating. Prepare a silk fibroin solution, adding an appropriate amount of glycerol as a plasticizer, and mix the edaravone aqueous solution with the silk fibroin solution evenly. Apply the silk fibroin / edaravone solution to the surface of the scaffold loaded with rapamycin / heparin sodium after step S3 using the sol-gel method, and dry it in a room temperature oven after coating. Silk fibroin and edaravone co-drug delivery system: Using the sol-gel method, the mass fraction of silk fibroin is controlled at 2wt%-4wt%, and the concentration of edaravone is 0.5mg / mL-2mg / mL. After coating, dry it in a room temperature oven at 40℃-60℃ for 2h-4h.

[0066] To enable those skilled in the art to more clearly understand the present invention, the following embodiments will be used to describe in detail the preparation method of a time-controlled drug release multifunctional intracranial stent provided by the present invention.

[0067] Example 1-1: A method for fabricating a time-controlled drug release multifunctional intracranial scaffold includes preparing an underlayer coating on a scaffold substrate, specifically comprising the following steps: S11. Iron-based alloys were selected as experimental materials and ultrasonically cleaned with acetone and ethanol before drying. The iron-based alloys were placed in an electrolyte consisting of a mixed solution of 0.3wt% NH4F and 2% ethylene glycol-water, and the voltage was controlled at 100V, the electrolysis time at 3h, and the temperature at 30℃ to prepare iron oxide nanotubes on a scaffold substrate.

[0068] S21. The surface of iron oxide nanotubes was modified with polydopamine (PDA) at a concentration of 2 mg / mL (Tris-HCl buffer, pH 8.5, reaction time 2 h). Rapamycin was dissolved in acetone, and the concentration was controlled at 1 mg / mL. The rapamycin solution was added dropwise to the surface of the iron oxide nanotubes in three portions under vacuum, with 10-minute intervals between each addition, for a total addition time of 60 minutes. The drug loading of rapamycin was approximately 0.8 μg / cm³ as measured by UV-Vis. 2 Finally, an underlayer coating was prepared on the scaffold substrate.

[0069] In the bottom coating prepared by steps S11 and S21, the iron oxide nanotubes are relatively short (approximately 600 nm) and have a low drug loading efficiency (approximately 65%). In vitro release: approximately 40% release occurs after 24 hours, indicating a moderate sustained-release effect. This suggests that under low voltage, the nanotube structure is relatively loose, resulting in lower drug loading, but the release is more stable.

[0070] Examples 1-2: A method for fabricating a time-controlled drug release multifunctional intracranial scaffold includes preparing an underlayer coating on a scaffold substrate, specifically comprising the following steps: S12. Iron-based alloys were selected as experimental materials and ultrasonically cleaned with acetone and ethanol before drying. The iron-based alloys were placed in an electrolyte consisting of a mixed solution of 0.3wt% NH4F and 2% ethylene glycol-water, and the voltage was controlled at 160V, the electrolysis time at 2h, and the temperature at 40℃ to prepare iron oxide nanotubes on a scaffold substrate.

[0071] S22. The surface of iron oxide nanotubes was modified with polydopamine (PDA) at a concentration of 2 mg / mL (Tris-HCl buffer, pH 8.5, reaction time 2 h). Rapamycin was dissolved in acetone, and the concentration was controlled at 3 mg / mL. The rapamycin solution was added dropwise to the surface of the iron oxide nanotubes in four portions under vacuum, with 5-minute intervals between each addition, for a total addition time of 45 minutes. The drug loading of rapamycin was approximately 2.5 μg / cm³ as measured by UV-Vis. 2 .

[0072] like Figure 1 As shown, in the bottom coating prepared by steps S12 and S22 in this embodiment, the iron oxide nanotubes have uniform length (approximately 1.2 μm), intact walls, and high drug loading efficiency (≈85%). In vitro release: approximately 60% release in 24 hours and 90% release in 72 hours, meeting the requirements for sustained release. It can be seen that the nanotube structure at 160V is optimal, with the best drug loading and release performance.

[0073] Examples 1-3: Unlike Examples 1-1, in step S11, the voltage was controlled at 220V, the electrolysis time at 1h, and the temperature at 25℃ during the anodic oxidation process. In step S21, the PDA concentration was 2mg / mL (reaction time 2h); the rapamycin loading concentration was 5mg / mL (acetone solution), the dropping time was 30min (continuous dropping), and the rapamycin loading was approximately 4.2μg / cm³ as measured by UV-Vis. 2 ; In the underlying coating prepared in this embodiment, the iron oxide nanotubes were too long (>2μm), resulting in partial structural collapse and a decrease in drug loading efficiency (≈70%). In vitro release: 80% release was observed after 24 hours, indicating a significant burst release effect. This demonstrates that high voltage leads to nanotube structural defects, poor drug loading stability, and a high risk of burst release.

[0074] Examples 1-4: The only difference from Example 1-1 is the drug loading concentration. Three groups of drug loading groups with different rapamycin concentrations were designed to obtain three types of undercoat coatings with controlled drug loading concentrations: Group 1: Rapamycin concentration was 1 mg / mL (drug loading ≈ 0.9 μg / cm³). 2 ); Group 2: Rapamycin concentration was 3 mg / mL (drug loading ≈ 2.5 μg / cm³). 2 ); Group 3: Rapamycin concentration was 5 mg / mL (drug loading ≈ 3.8 μg / cm³). 2 ).

[0075] In this embodiment, among the three types of undercoat prepared, the drug loading was positively correlated with the concentration, but at 5 mg / mL, some drug was adsorbed at the tube opening rather than inside the tube. The 3 mg / mL group had the most stable release curve, while the 5 mg / mL group showed a significant initial burst release. Therefore, 3 mg / mL is the optimal drug loading concentration, balancing both drug loading and sustained-release performance.

[0076] Examples 1-5: The only difference from Examples 1-2 is the electrolysis temperature. Two sets of different electrolysis temperatures were designed to obtain two different undercoat coatings controlled by the electrolysis temperature: Low-temperature group: Electrolysis temperature is 20℃; High-temperature group: electrolysis temperature is 50℃.

[0077] In this embodiment, among the two underlying coatings prepared, the nanotubes in the low-temperature group grew more slowly, with a drug loading of approximately 2.0 μg / cm³. 2 The high-temperature group showed accelerated nanotube growth, but some nanotube walls were porous, resulting in a drug loading capacity of approximately 2.3 μg / cm³. 2 The release was slightly faster. It can be seen that the anodizing at 40°C in Examples 1-2 balanced the growth rate and structural stability.

[0078] Example 2-1 (Low-temperature degumming + short time + low glycerin): A method for preparing a time-controlled drug release multifunctional intracranial scaffold includes preparing a bottom layer coating and a middle layer coating (a β-structure-rich silk fibroin / heparin sodium drug-loaded coating) on ​​a scaffold substrate. The preparation of the bottom layer coating is described in Examples 1-(1 / 2 / 3 / 4 / 5), and the preparation of the middle layer coating specifically includes the following steps: S31. The silk fibroin solution was degummed and purified by dialysis. The degumming temperature was 60℃ (lower limit of range) and the time was 30 min (lower limit of range). The dialysis conditions were: molecular weight cutoff of 10 kDa and dialysis time of 48 h. The concentration treatment was carried out for 24 h. Finally, a silk fibroin solution with a concentration of 4 wt% was obtained.

[0079] S32. Add 5% glycerol to a 4 wt% silk fibroin solution.

[0080] S33. Dissolve sodium heparin in deionized water to obtain a 1 mg / mL sodium heparin solution. Mix the silk fibroin solution and the sodium heparin solution at a ratio of 4:1 (v / v) to obtain a composite sol.

[0081] S34. The composite sol was dipped onto the surface of the bottom coating prepared in Examples 1-2 using the sol-gel method, crosslinked in 75% ethanol for 5 min, and then dried at 40°C for 2 h to finally obtain the middle coating.

[0082] In this embodiment, the intermediate coating prepared through steps S31-S34 has a β-sheet content of approximately 30% and a loose fiber structure. The heparin sodium loading efficiency is approximately 75% (toluidine blue method). Drug release is 60% after 24 hours and 95% after 72 hours. It is evident that low-temperature, short-term degumming leads to insufficient β-sheet structure, resulting in poor sustained-release performance of the coating.

[0083] Example 2-2 (Medium-temperature degumming + medium time + medium glycerin): Unlike Example 2-1, in step S31, the degumming temperature was 70°C (mid-range) and the time was 60 min (mid-range). In step S32, the glycerol content was 7.5% (mid-range). In step S33, the concentration of the heparin sodium solution was 1.5 mg / mL, and the mixing ratio was 3:1 (v / v).

[0084] like Figure 2 As shown in Figures a and b, the β-sheet content of the intermediate coating prepared in this embodiment is approximately 45%, and the fibers are uniform (diameter approximately 150 nm). The heparin sodium loading efficiency is approximately 85%, with 45% release at 24 h and 80% release at 72 h. It can be seen that degumming at 70℃ combined with 7.5% glycerol balances structural stability and drug sustained-release performance.

[0085] Examples 2-3 (High-temperature degumming + long duration + high glycerin): Unlike Example 2-1, in step S31, the degumming temperature is 80°C (upper limit) and the time is 120 min (upper limit). In step S32, the glycerol content is 10% (upper limit). In step S33, the concentration of the heparin sodium solution is 2 mg / mL, and the mixing ratio is 2:1 (v / v).

[0086] The intermediate coating prepared in this embodiment has a β-sheet content of approximately 55% and dense fibers (SEM). The heparin sodium loading efficiency is approximately 92%, with 30% release after 24 hours and 70% release after 7 days. This indicates that high-temperature, long-term degumming combined with 10% glycerol significantly improves the β-sheet structure and sustained-release performance, making it suitable for long-term drug loading.

[0087] Examples 2-4 (Cross-validation: High temperature for short time + low glycerol): Unlike Example 2-1, in step S31, the degumming temperature is 80°C (high temperature), the time is 30 min (short time), and the glycerol content is 5% (low glycerol).

[0088] In the intermediate coating prepared in this embodiment, the β-sheet content is approximately 40%, and the fibers are partially agglomerated. The heparin sodium loading efficiency is approximately 80%, and the release rate is between that of Examples 2-1 and 2-3. It can be seen that high temperature can partially compensate for the insufficiency of short-term degumming, but low glycerol leads to a decrease in coating flexibility.

[0089] Examples 2-5 (Cross-validation: Low temperature for a long time + high glycerol): Unlike Examples 2-4, in step S31, the degumming process is performed at 60°C (low temperature) for 120 min (long time), and the glycerol content is 10% (high glycerol).

[0090] In the intermediate coating prepared in this embodiment, the β-sheet content is approximately 35%, and the fiber structure is loose. The heparin sodium loading efficiency is approximately 78%, and the release rate is fast (65% released in 24 hours). It can be seen that extending the degumming time at low temperature has limited effect on improving the β-sheet structure, and high glycerol only improves flexibility.

[0091] Example 3-1 (Low silk fibroin + low edaravone + low temperature short-time drying): A method for preparing a time-controlled drug release multifunctional intracranial scaffold includes sequentially preparing a base layer coating, a middle layer coating, and a surface layer coating on a scaffold substrate. The preparation of the base layer coating is described in Examples 1-(1 / 2 / 3 / 4 / 5), the preparation of the middle layer coating is described in Examples 2-(1 / 2 / 3 / 4 / 5), and the preparation of the surface layer coating specifically includes the following steps: S41. Prepare a silk fibroin solution with a mass fraction of 2 wt% (lower limit of range) and add 5% glycerol (lower limit of range) to the solution; prepare an edaravone solution with a concentration of 0.5 mg / mL (lower limit of range); then mix the silk fibroin solution and the edaravone solution at a ratio of 5:1 (v / v).

[0092] S42. The obtained mixed solution is applied to the surface of the intermediate coating prepared in Example 2-2 by spin coating using the sol-gel method, and then dried at 40°C (low temperature) for 2 hours (short time) to finally obtain the surface coating.

[0093] In this embodiment, the drug loading in the surface coating prepared by steps S41 and S42 is approximately 0.4 μg / cm³. 2 The coating is relatively thin. Release curve: 70% release at 24h, 95% release at 48h (significant burst release). This indicates that the low-concentration combination results in low drug loading and rapid release, suitable for short-term drug release needs.

[0094] Example 3-2 (medium-strength silk fibroin + medium-strength edaravone + medium-temperature, medium-time drying): Unlike Example 3-1, in step S41, the silk fibroin mass fraction was 3 wt% (mid-range), and the amount of glycerol added was 7.5% (mid-range). The concentration of edaravone was 1 mg / mL (mid-range). The mixing ratio of the silk fibroin solution and the edaravone solution was 4:1 (v / v). In step S42, drying was carried out at 50°C (medium temperature) for 3 hours (medium time).

[0095] like Figure 2 As shown in Figures c, d, and e, the drug loading in the surface coating prepared in this embodiment is approximately 0.8 μg / cm³. 2 The coating is uniform. Release curve: 50% release at 24h, 85% release at 72h (improved sustained release). This indicates that the medium-concentration combination balances drug loading and release performance, making it suitable for most sustained-release applications.

[0096] Example 3-3 (High silk fibroin + high edaravone + high temperature and long time drying): Unlike Example 3-1, in step S41, the silk fibroin mass fraction was 4 wt% (upper limit), and the amount of glycerol added was 10% (upper limit). The concentration of edaravone was 2 mg / mL (upper limit). The mixing ratio of the silk fibroin solution and the edaravone solution was 3:1 (v / v). In step S42, drying was performed at 60°C (high temperature) for 4 hours (long time).

[0097] The drug loading in the surface coating prepared in this embodiment is approximately 1.5 μg / cm³. 2 However, localized drug crystallization occurred. Release curve: 40% release in 24 hours, 75% release in 7 days (optimal sustained release, but initial crystallization affects uniformity). It can be seen that the high-concentration combination has high drug loading and excellent sustained-release performance, but the drying process needs to be optimized to avoid crystallization.

[0098] Examples 3-4 (Cross-validation: Low silk fibroin + high edaravone + medium-temperature long-time drying): A method for fabricating a time-controlled drug release multifunctional intracranial scaffold, comprising the preparation of a surface coating: S41-1. Prepare a silk fibroin solution with a mass fraction of 2wt%, and add 10% glycerol to the solution; prepare an edaravone solution with a concentration of 2mg / mL; then mix the silk fibroin solution and the edaravone solution at a ratio of 5:1 (v / v).

[0099] S42-1. The mixed solution is coated onto the surface of the intermediate coating prepared in Example 2-2 by spin coating using the sol-gel method, and then dried at 50°C for 4 hours to finally obtain the surface coating.

[0100] The drug loading in the surface coating prepared in this embodiment is approximately 1.2 μg / cm³. 2 Microcracks appeared in the coating. Release curve: 60% release in 24 hours and 90% release in 5 days. It can be seen that low silk fibroin cannot effectively encapsulate high concentrations of edaravone, resulting in structural defects.

[0101] Examples 3-5 (Cross-validation: High silk fibroin + low edaravone + low-temperature long-term drying): Unlike Examples 3-4, the silk fibroin had a mass fraction of 4 wt%, the glycerol content was 5%, the edaravone concentration was 0.5 mg / mL, and the drying conditions were drying at 40°C for 4 hours.

[0102] In the surface coating prepared in this embodiment, the drug loading is approximately 0.3 μg / cm³. 2 The coating is dense and defect-free. Release curve: 30% release in 24 hours, 60% release in 7 days (excessive sustained release). This indicates that the high-silk fibroin encapsulation of low-concentration drugs leads to slow release, which may affect efficacy.

[0103] Comparative example: A method for fabricating a time-controlled drug release multifunctional intracranial scaffold includes directly fabricating a surface coating on a base coating: S101. Prepare a silk fibroin solution with a mass fraction of 3 wt%, and add 7.5% glycerol to the solution; prepare an edaravone solution with a concentration of 1 mg / mL; then mix the silk fibroin solution and the edaravone solution at a ratio of 4:1 (v / v).

[0104] S102. The mixed solution is coated onto the surface of the underlying coating prepared in Examples 1-2 by spin coating using the sol-gel method, and then dried at 50°C for 3 hours. Finally, a silk fibroin / edaravone drug-loaded coating is generated on the iron oxide nanotubes grown on the Fe-based metal surface.

[0105] Comparative experiment: The multifunctional scaffolds obtained from Examples 1-2 (where a base coating is formed on the surface of an Fe-based metal), Examples 2-2 (where a middle coating is applied on top of the base coating), and Examples 3-2 (where a top coating is applied on top of the middle coating) were subjected to scanning electron microscopy (SEM) experiments and activity tests, respectively, yielding the following results: Figure 1 , Figure 2 and Figure 3Cell compatibility tests were conducted on Examples 1-2, 2-2, and 3-2, as well as the comparative examples, according to ISO 10993. Samples were placed in culture medium containing 10% fetal bovine serum and extracted at 37°C for 24 hours to prepare extracts. Cells were seeded in 96-well plates, and after cell adhesion, the extracts were replaced and cultured for another day. After one day of culture, the absorbance (OD) of each well was measured using the CCK-8 assay, and the relative cell growth rate (RGR) was calculated to evaluate the effect of each coating gradient on cell proliferation. Simultaneously, the cell spreading morphology and viability status on the sample surface were observed under a fluorescence microscope using Calcein-AM / PI double staining. The cell compatibility data comparison table for each experimental example is shown in Table 1 below.

[0106] Table 1:

[0107] from Figures 1-3 As shown in Table 1, regarding structural compatibility, the use of a medium concentration of 3wt% silk fibroin (SF) combined with 7.5% glycerol not only ensured good interfacial bonding between the surface coating, middle coating, and bottom coating, preventing coating peeling in the complex intracranial environment, but also, the drying parameters of 50℃ / 3h promoted the moderate β-folding of SF molecular chains, constructing a dense and moderately cross-linked network. Regarding controlled-release behavior, compared to examples with low concentrations or high temperatures, group 3-2, through the synergistic effect of "medium concentration drug loading + medium-temperature curing," successfully controlled the 24h release to approximately 50% and increased the 72h cumulative release rate to 85%. This stepwise release mode effectively overcomes the drawbacks of excessively rapid initial release or incomplete release in the later stages, achieving a long-term, stable supply of edaravone to the lesion site. Example 3-2 achieved the best balance between processing performance and biosafety. 0.8μg / cm 2 The combination of high drug loading and uniform coating morphology ensures that the local drug concentration is sufficient to exert antioxidant and neuroprotective effects, while minimizing the cytotoxicity that may result from high drug loading, demonstrating excellent potential for clinical application.

[0108] In summary, the silk fibroin used in this invention is a natural copolymer extracted from silkworms, mainly composed of glycine, alanine, serine, and tyrosine (accounting for more than 95% of the total). It has attracted widespread attention in the field of drug sustained release and has the following advantages: 1) Good biocompatibility: Silk fibroin has low immunogenicity and good biocompatibility, and is a non-toxic, non-irritating, and uniquely bioactive natural biomaterial approved by the FDA; 2) Good drug loading stability: Silk fibroin is an excellent drug carrier. Its water solubility and amphiphilic structure allow it to maintain stable loading without the need for other chemical reagents, through covalent bonding, physical adsorption, and encapsulation (self-organized nanoscale microenvironment). This is especially beneficial for maintaining the long-term stability of easily inactivated and degraded active polymers or small drug molecules such as enzymes, peptides, and growth factors; 3) Good controllability of degradation rate: By regulating the content of the Silk II structure (antiparallel β-sheet conformation), its degradation rate can be significantly controlled, which is beneficial for treatment based on thrombosis and proliferation. 4) The degradation products are safe and non-toxic. The degradation products of silk fibroin are neutral, avoiding the inflammatory reactions caused by existing degradable or non-degradable polymer carriers and the risk of inactivation of active substances due to the surrounding local acidity generated by the degradation products. A large number of in vitro / in vivo studies have shown that the biocompatibility of silk fibroin is better than that of PLA, PGA and some collagen. 5) It has strong processability and can be processed into drug sustained release systems in the shapes of microspheres, microcapsules, membranes, fibers and microtubules according to application requirements. 6) It has good mechanical properties. As a scaffold coating material, it is not easily damaged when the scaffold expands. The ultimate tensile strength of natural silk (containing sericin) is as high as 500 MPa and the elastic modulus is 5 GPa-12 GPa.

[0109] Correspondingly, in a third aspect, the present invention also provides the application of a time-sequential drug-controlled release multifunctional intracranial stent in the treatment of cerebral vascular stenosis, to reduce cerebral restenosis and cerebral ischemia-reperfusion injury. The time-sequential multifunctional gradient drug-controlled release coating developed in this invention is mainly applied in the field of cerebral vascular stents, and can effectively reduce or lower the complications related to stent intervention in patients with symptomatic and asymptomatic cerebral vascular stenosis, further reducing the risk of ischemic stroke. Based on traditional polymeric drug sustained-release systems, neuroprotective drug molecules are introduced, and while reducing the in-stent restenosis rate, a time-sequential coating that closely approximates the pathological process at the site of action is prepared, reducing ischemia-reperfusion injury and further improving the safety and effectiveness of stent placement for the treatment of acute ischemic cerebrovascular disease.

[0110] This invention combines neuroprotective drugs with cerebral vascular stents. Based on the pathogenesis of cerebral ischemia-reperfusion injury and the pathogenesis of intravascular stenosis after stent placement, a multifunctional gradient drug coating containing neuroprotective drugs for cerebral ischemia-reperfusion, antithrombotic drugs, and anti-vascular smooth muscle cell proliferation drugs is prepared on the surface of typical cerebral vascular stent materials using electrochemical and sol-gel methods. By regulating the silk fibroin structure, the micro-nano structure of the matrix material, the drug molecule content, and the membrane composition, the time-sequential, staged, and controllable release of different drug molecules is achieved, matching the pathological process at the site of action. This achieves both neuroprotective effects and a reduction in the rate of cerebral restenosis.

[0111] It should be noted that, for the method embodiments, the embodiments of this application are not limited to the described order of actions, because according to the embodiments of this application, some steps may be performed in other orders or simultaneously.

[0112] The above method embodiments are basically similar to the system embodiments, so the description is relatively simple. For relevant details, please refer to the description of the system embodiments.

[0113] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0114] It should also be noted that, in this document, the terms "inner," "outer," etc., indicating orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device.

Claims

1. A time-controlled drug release multifunctional intracranial stent, characterized in that, include: The scaffold matrix is ​​made of a biodegradable material, which includes at least an Fe-based metal material; And the following are arranged sequentially from the inside to the outside on the surface of the support base: The bottom coating is composed of iron oxide nanotubes, the surface of which is modified with polydopamine and loaded with rapamycin. The middle coating is formed by a complex of β-structure-rich silk fibroin and sodium heparin. The surface coating is formed by a complex of silk fibroin and edaravone. The positions of the top coating, the middle coating, and the bottom coating correspond to the drug release sequence contained in each coating, so that the corresponding drugs are released at different stages after the stent matrix is ​​placed into the blood vessel, in order to adapt to the pathological evolution process during the vascular repair process.

2. The time-controlled drug release multifunctional intracranial stent according to claim 1, characterized in that, The iron oxide nanotubes are prepared by anodizing, and the preparation method includes: The Fe-based metal material is placed in an electrolyte; the electrolyte comprises NH4F, water, and ethylene glycol. The scaffold substrate is anodized using the electrolyte to form iron oxide nanotubes on the outer surface of the scaffold substrate. During the anodizing process, the voltage is 100V-220V, the treatment temperature is 20℃-50℃, and the treatment time is 1h-3h.

3. A time-controlled drug release multifunctional intracranial stent according to claim 1 or 2, characterized in that, The rapamycin in the underlying coating is loaded onto the iron oxide nanotubes by the following method: Rapamycin solution was prepared by dissolving the rapamycin in acetone; the concentration of rapamycin in the rapamycin solution was 1 mg / mL-5 mg / mL. The scaffold matrix on which the iron oxide nanotubes are formed is placed in a vacuum environment, and the rapamycin solution is dropped onto the iron oxide nanotubes so that the rapamycin is uniformly loaded on the surface of the iron oxide nanotubes. During the vacuum dripping process, the dripping time is 0.5h-1h.

4. The time-controlled drug release multifunctional intracranial stent according to claim 1, characterized in that, The intermediate coating layer is prepared by the following method: The silk fibroin solution was degummed and purified by dialysis, and the β-structure content was adjusted to make the silk fibroin solution rich in β-structure. A plasticizer is added to the silk fibroin solution and mixed with an aqueous heparin sodium solution to form a composite sol; The composite sol is coated onto the surface of the bottom layer using the sol-gel method, and then crosslinked in an ethanol-water mixed solution, followed by drying to form the middle layer coating.

5. The time-controlled drug release multifunctional intracranial stent according to claim 4, characterized in that, The plasticizer includes 5%-10% glycerol.

6. The time-controlled drug release multifunctional intracranial stent according to claim 1, characterized in that, The surface coating is prepared by the following method: A silk fibroin solution is mixed with an edaravone solution; wherein the silk fibroin solution contains 2wt%-4wt% of silk fibroin and the edaravone solution contains 0.5mg / mL-2mg / mL of edaravone. The resulting mixed solution was coated onto the surface of the intermediate coating using the sol-gel method and dried at 40℃-60℃ for 2h-4h to form the bottom coating.

7. The time-controlled drug release multifunctional intracranial stent according to claim 1, characterized in that, The thicknesses of the bottom coating, the middle coating, and the top coating are 10 μm to 100 μm, respectively.

8. The time-controlled drug release multifunctional intracranial stent according to claim 1, characterized in that, The strength of the support matrix is ​​700MPa-1000MPa.

9. The method for preparing a time-controlled drug-release multifunctional intracranial scaffold according to any one of claims 1-8, characterized in that, Includes the following steps: S1. Select Fe-based metal material as the scaffold matrix, and grow iron oxide nanotubes on the surface of the scaffold matrix by anodizing. S2. The iron oxide nanotubes are modified with polydopamine, and rapamycin is loaded onto the iron oxide nanotubes by vacuum drop addition to form an underlayer coating on the surface of the scaffold matrix. S3. Prepare a composite sol composed of β-rich silk fibroin and sodium heparin, coat the composite sol onto the surface of the bottom coating, crosslink and dry to form a middle coating on the bottom coating. S4. Prepare a silk fibroin / edaravone composite solution, coat the silk fibroin / edaravone composite solution onto the surface of the intermediate coating layer, and after drying, form a top coating layer on the intermediate coating layer.

10. The method for preparing a time-controlled drug release multifunctional intracranial scaffold according to claim 9, characterized in that, In step S3, the silk fibroin solution is degelatinated and purified by dialysis to obtain a silk fibroin solution rich in β-structure. The silk fibroin solution rich in β-structure is then mixed with an aqueous solution of heparin sodium to prepare the composite sol.

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