Flexible conductive extravenous stent based on functional electrical stimulation

Abstract

The invention relates to a flexible conductive intravenous stent based on functional electrical stimulation. The invention belongs to the fields of biomedical engineering and the like. The PCL-Gr extravascular stent is prepared by utilizing an electrostatic spinning technology, and the PCL-Gr extravascular stent wraps the periphery of the transplanted vein to provide necessary mechanical support for the transplanted vein so as to maintain the structural stability of the transplanted vein, so that the risk of restenosis caused by hemodynamic change is reduced. And meanwhile, functional electrical stimulation is accurately applied to transplanted veins by utilizing conductivity, so that double mechanisms of promoting endothelialization and inhibiting smooth muscle cell proliferation are achieved, and the risk of intimal hyperplasia is effectively reduced.

Description

Technical Field

[0001] The present invention relates to a flexible conductive venous external stent based on functional electrical stimulation and belongs to the field of biomedical engineering and the like. Background Art

[0002] Coronary artery bypass grafting (CABG) is a common therapeutic surgical procedure. Compliance plays a crucial role in maintaining blood pressure. Poor venous compliance can alter preexisting hemodynamics, leading to intimal hyperplasia and graft failure. During this process, excessive proliferation of vascular smooth muscle cells leads to narrowing of the vascular pathway, which in turn impedes blood flow. Restenosis after venous grafting due to differences in arteriovenous mechanics is a major cause of venous graft and hemodialysis access failure.

[0003] Extravascular support structures are composed of biocompatible biomaterials and can take the form of external stents or coatings. Their primary function is to provide necessary support for the vein and help maintain the integrity of the vascular endothelium. Restenosis can reduce the function of the graft and, in turn, affect the long-term success of the graft. The use of these support structures can effectively prevent restenosis.

[0004] Polycaprolactone (PCL) is a versatile synthetic polymer with biodegradability and excellent biocompatibility. PCL molecular chains gradually degrade into harmless metabolites in the body without causing a severe immune response, making PCL ideal for the preparation of absorbable medical devices such as sutures. PCL's low melting point makes it easy to process at relatively low temperatures, facilitating the use of electrospinning technology to prepare medical materials with complex structures. These properties make PCL an ideal material for the preparation of extravascular stents.

[0005] Graphene (Gr) is a multifunctional biomedical material with a unique two-dimensional structure, excellent electrical conductivity, mechanical strength, thermal conductivity and biocompatibility. Gr materials have a high specific surface area, providing a broad space for cell attachment and growth. The tensile modulus of Gr far exceeds that of traditional materials, which can enhance the mechanical properties of composite materials and is suitable for bone tissue engineering and cardiovascular tissue engineering. In addition, Gr has high electron mobility and has important application value in electrical stimulation regulation and nerve regeneration. Therefore, as a multifunctional biomedical material, Gr has significant potential and value in promoting tissue repair, improving the mechanical properties of scaffolds and constructing electroactive biomaterials.

[0006] Therefore, to address the problem of vein graft restenosis, the present invention first utilizes electrospinning technology to prepare and screen Gr-loaded PCL extravascular stents with excellent mechanical properties. The PCL-Gr extravascular stents are then wrapped around autologous vein material and transplanted into rat carotid arteries. This invention not only prepares a flexible, conductive extravascular stent based on functional electrical stimulation, achieving the therapeutic effect of inhibiting intimal hyperplasia of the vein graft through bioelectrical intervention, but also establishes an autologous vein graft rat model to enable in vivo evaluation of the extravascular stent. Furthermore, this method can be used to explore the regulatory mechanisms of electrical stimulation on cellular signaling pathways and its impact on extracellular matrix remodeling, providing theoretical and methodological support for optimizing electrical stimulation parameters and developing novel stent materials. Summary of the Invention

[0007] The present invention successfully developed a new type of extravascular stent, which achieves multiple functions by loading graphene. First, the stent is made of PCL nanofiber material, which provides the necessary mechanical support. Secondly, the introduction of graphene not only enhances the biological activity of the stent, but also gives the stent electrical conductivity. The introduction of electrical stimulation intervention effectively inhibits the proliferation of smooth muscle cells and promotes their phenotypic transformation, thereby inhibiting the proliferation of the vascular endothelium. A rat model was used to evaluate the in vivo patency. The Gr-loaded extravascular stent combined with a specific electrical stimulation signal showed significant advantages in maintaining long-term patency, which is of great significance for preventing restenosis of blood vessels after transplantation.

[0008] The present invention provides a technical solution for inhibiting intimal hyperplasia of venous grafts using a flexible conductive external venous stent based on functional electrical stimulation, which specifically includes:

[0009] (1) Preparation of Gr-loaded PCL extravascular stents by electrospinning;

[0010] (2) Screening of PCL-Gr extravascular stents suitable for transplantation;

[0011] (3) The PCL-Gr extravascular stent was implanted into rats with autologous vein grafts to evaluate the vascular patency under functional electrical stimulation.

[0012] Beneficial effects of the present invention: The present invention prepares a flexible, conductive extravenous stent based on functional electrical stimulation, which can inhibit the intimal hyperplasia of venous grafts. Not only can the PCL-Gr extravascular stent be wrapped around the graft vein to provide the graft vein with the necessary mechanical support to maintain the structural stability of the graft vein, thereby reducing the risk of restenosis caused by hemodynamic changes. It can also use the conductive properties to accurately apply functional electrical stimulation to the graft vein, achieving a dual mechanism of promoting endothelialization and inhibiting smooth muscle cell proliferation, effectively reducing the risk of intimal hyperplasia. In addition, animal experiments on autologous vein transplantation in rats were conducted. Through these experiments, the actual performance of the stent in vivo can be evaluated, including its effect on the patency of the graft vein and its ability to maintain endothelial integrity. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the overall experimental process of the present invention;

[0014] Figure 2 This is the tensile test diagram of the PCL-Gr extravascular stent;

[0015] Figure 3 This is the morphological diagram of the PCL-Gr extravascular stent;

[0016] Figure 4 Diagram of vascular transplantation for animal surgery;

[0017] Figure 5 For vascular patency analysis. DETAILED DESCRIPTION

[0018] In order to make the features of the present invention more obvious, the specific implementation process of the present invention is described below in conjunction with specific embodiments.

[0019] Example 1

[0020] like Figure 1 The overall schematic diagram shown shows the whole process of preparing the extravascular stent and transplanting the extravascular stent into the rat carotid artery.

[0021] (1) Fabrication of electrospun PCL-Gr extravascular stents 1.5 g PCL was mixed with 0.01 g, 0.02 g, 0.05 g, 0.08 g, and 0.1 g Gr, respectively, in hexafluoroisopropanol (HFIP) and stirred with a magnetic stirrer at room temperature (RT) for 12 h to prepare PCL-Gr solutions containing 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.8 wt%, and 1 wt%. 2. Pour the PCL-Gr solution into a 10 mL syringe. 3. Replace the syringe needle with a 21-G needle. 4. Place the tungsten steel rod core shaft (1.6mm diameter, 20cm long) on the receiver. 5. The electrospinning parameters were a working distance of 16 cm from the needle tip to the collector, a feed rate of 0.0032 mm / s, and a voltage of 10 kV. A PCL-Gr extravascular stent with a thickness of 250 μm was produced. 6. Place the extravascular stent obtained above in a vacuum device for 72 hours to remove the residual solvent.

[0022] (2) Screening of PCL-Gr extravascular stents suitable for transplantation 1. Microscopic observation of 250 μm thick 0.1% Gr, 0.2% Gr, 0.5% Gr, 0.8% Gr, and 1% Gr extravascular stents. Mechanical properties of the stents were tested using a universal tensile testing machine (n = 3). Origin software was then used to generate graphs and conduct comparative analysis to identify PCL-Gr extravascular stents with excellent mechanical properties and suitability for transplantation. 2. Gr loading: Based on scanning electron microscopy (SEM) images, the microstructure of the fibers was characterized by SEM and the Gr particles in the fibers were identified.

[0023] The mechanical test results show that Figure 2 As shown in Figure 2, the elastic modulus is most suitable when Gr concentration is 0.2%. Therefore, PCL-Gr extravascular stent with a concentration of 0.2% was selected as the appropriate graft stent. Figure 3 As shown in the figure, the surface of the PCL fiber is evenly distributed with numerous fine white particles. Based on the expected particle size of these particles, they are presumed to be nano-sized Gr particles.

[0024] like Figure 4 As shown, the process of establishing the rat surgical model

[0025] (3) Rat carotid artery transplantation 1. Intraperitoneal injection of anesthetic, place the rat on the operating table, fix the limbs and keep the abdomen facing up; 2. Cut the midline of the neck, separate the jugular vein, ligate it with an electric coagulation knife, and cut off the vein; 3. Peel off the salivary glands, expose the surgical site, and separate the carotid artery; 4. Fix the carotid artery with an artery clamp and cut the middle part of the carotid artery; 5. Anastomose one end of the graft vein to the proximal artery and the other end to the distal artery, using 8 11-0 sutures. 6. Wrap the extravascular stent around the graft vein and connect it with 9-0 sutures; 7. After completion, remove the proximal artery clamp first, then the distal artery clamp, flush with heparinized saline, and observe the patency of the blood vessels; 8. The neck skin was sutured with 3-0 sutures, disinfected with iodine, and the rat was placed in a 37°C incubator until it woke up.

[0026] like Figure 5 As shown, 30 days after implantation, the implanted vessels were removed. Stereomicroscopy and histological staining were used to assess vascular wall thickness and vascular patency at 30 days. Stereomicroscopy and H&E staining results demonstrated that the veins wrapped with the Gr-loaded extravascular stent integrated well with the host arteries, maintaining vascular patency. Electron microscopy revealed that the vessels were patency, with no significant thrombosis, smooth vessels, and no significant vascular proliferation. Electron microscopy and CD31 immunofluorescence staining revealed that endothelial cells were arranged in a regular cobblestone shape, along the direction of blood flow, exhibiting a high cell aspect ratio and complete coverage.

[0027] 5. Summary

[0028] This invention describes a Gr-loaded extravascular stent. The design involves screening for a suitable PCL-Gr extravascular stent, wrapping the PCL-Gr stent around a venous graft, and then implanting it in the rat carotid artery for biological evaluation. This invention demonstrates the feasibility of this technology by preparing a flexible, conductive extravascular stent based on functional electrical stimulation. This electrical stimulation inhibits vascular smooth muscle cell proliferation and promotes phenotypic transformation, further facilitating the maintenance of endothelial integrity. This also enables in vivo evaluation of the stent and explores the inflammatory mechanisms of intimal hyperplasia, providing theoretical and methodological support for the inhibition of intimal hyperplasia by Gr-loaded extravascular stents.

Claims

1. A flexible, conductive, external venous stent based on functional electrical stimulation, characterized by: Combining functional electrical stimulation with conductive biomaterial technology, a flexible, conductive extravenous stent is used to inhibit the proliferation of vascular smooth muscle cells and promote their phenotypic transformation. Specifically, this includes the use of electrospinning technology to prepare PCL-Gr extravascular stents and fiber membranes, electrical stimulation intervention plans and parameter control methods, the construction of an autologous vein transplant rat model, and in vivo transplantation and vascular patency evaluation methods.

2. The method for preparing PCL-Gr extravascular stent and fiber membrane by electrospinning technology according to claim 1, characterized in that: The electrospinning process parameters are: 15% PCL-0.2% Gr solution, 21G needle, 10KV high voltage, 0.0032mm / s propulsion rate, 500r / min rotation speed, 13-16cm distance between needle and receiver, and 0.7mm thickness of receiver tungsten steel rod.

3. The electrical stimulation intervention program and parameter control method according to claim 1, characterized in that: The stimulation mode is an AC signal with a frequency of 100 Hz and an output current intensity of 1 mA. Electrical stimulation is applied once a day, each lasting 20 minutes.

4. The construction of the autologous vein transplantation rat model according to claim 1, characterized in that: SD rats were selected and a carotid artery vascular in situ transplantation model was established. During the operation, the jugular vein segment was removed and anastomosed to the carotid artery defect using 11-0 sutures. After the operation, the grafted vein was wrapped with a stent and fixed with 9-0 sutures.

5. The in vivo transplantation and vascular patency analysis method according to claim 1, characterized in that: The grafted vein was removed 30 days after the transplantation, and the effect of electrical stimulation on the patency of the vein after transplantation was evaluated using a stereomicroscope and HE staining, Masson staining, VVG staining and calcification staining. The results showed that the electrical stimulation extravascular stent can effectively inhibit the excessive proliferation of the intima after vein transplantation in rats and improve the patency of blood vessels.

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