Retractable self-expansion covered stent-mediated drug loading system

Abstract

The utility model discloses a drug delivery system mediated by a retractable self-expanding covered stent, which comprises a self-expanding stent, a balloon and a tearable tube, the balloon, the self-expanding stent and the tearable tube are sequentially sleeved from inside to outside, the self-expanding stent can be actively or passively expanded and compressed along the radial direction of the self-expanding stent, the self-expanding stent is coated with drugs, and the tearable tube is coated with the drugs. The tearable tube comprises a flexible part and a rigid part which are cylindrical and are coaxially connected, the flexible part can be torn, the flexible part is connected outside the self-expanding stent in a sleeving manner, and the tearable tube enables the flexible part to be torn to release the self-expanding stent through the expansion of the balloon. The tearable tube surrounds the self-expanding stent, so that a medicine coating on the self-expanding stent can be better protected, scratching between the self-expanding stent and an instrument is reduced, and conveying loss is reduced; the washing of the self-expanding stent drug coating in blood can be reduced, and the vascular drug absorption efficiency is improved. The regular circulating design of the net structure of the bare stent enhances the radial force, and ensures that the stent can be reliably expanded in the blood vessel and has enough supporting force.

Description

Technical Field

[0001] The utility model belongs to the technical field of medical devices, and in particular relates to a drug-carrying system mediated by a retractable self-expandable coated stent. Background Art

[0002] Coronary artery atherosclerosis is a common cardiovascular disease that seriously affects people's health. Unstable angina or myocardial infarction is an important cause of death from ischemic heart disease. Percutaneous coronary intervention stent implantation and the more recent drug-assisted balloon therapy are one of the effective treatments for coronary heart disease.

[0003] The permanent implant stent system is mainly a balloon-expandable stent system, which includes a stent and a delivery system. The stent is compressed and loaded on the delivery system balloon. When the stent is delivered to the lesion site, the balloon is pressurized and expanded to release the stent, and the stent remains permanently in the human body. There are many complications of permanent stent implantation, such as late stent thrombosis, late stent poor adhesion, late catch-up phenomenon, restenosis, stent fatigue fracture, and long-term poor endothelial coverage. Covering an ultra-long blood vessel segment with a stent will also affect the endothelial function of the vessel.

[0004] Drug-coated stents are conventional bare metal stents on which drugs are coated by appropriate methods. The drugs are released under blood flushing and exert their effects locally. Chinese invention patent application CN113599032A discloses a retractable drug-coated stent, comprising: an inner tube, a middle tube and an outer tube, wherein the proximal ends of the inner tube, the middle tube and the outer tube are connected with a pushing device; the distal end of the inner tube has a tip; a self-expanding stent, the surface of which has spikes, the surface of which is provided with a drug coating, and the self-expanding stent is connected to the distal end of the middle tube; the self-expanding stent has a retracted state, and the self-expanding stent also has an expanded state. However, when such self-expanding stent spikes penetrate calcified lesions, if the hardness of the spikes is too large, the blood vessels are easily scratched when the stent is released and withdrawn; if the hardness of the spikes is not enough, it is difficult to penetrate the calcified lesions and the vascular endothelium, enter the vascular tunica media and endothelium, and perform deep drug delivery. The direction of the spikes on the stent surface is perpendicular to the length of the stent. During the release of the stent along the length direction, if the target blood vessel is severely calcified, it is difficult for the spikes to penetrate the calcified lesions, and there is even a risk of the spikes falling off. In addition, the spike structure has the risk of scratching the blood vessels, so it is not suitable for the treatment of coronary artery stenosis. Its structure limits the application of this stent.

[0005] It is not difficult to see from the above that the interventional medical devices required for clinical drug treatment of coronary heart disease need to achieve the following effects: (1) Ensure that the drug delivery system enters the guide catheter and blood vessels along the guidewire, and the guidewire can be retained in the central cavity of the drug delivery system continuously; (2) The self-expanding stent structure and material design ensure safe release and recovery; (3) The self-expanding stent structure and material design ensure appropriate radial support force; (4) The stent coating is safe and reliable and will not fall off or break during operation; (5) The coated drug coating adheres reliably, does not fall off, and does not adhere to the outer tube; (6) The coated drug has appropriate tissue affinity, which is conducive to release and absorption and reduces loss; (7) After the coated stent is released, the central cavity can enter the intracavitary imaging catheter along the guidewire; (8) In special cases, after the coated stent is released, other types of balloons or stents can enter the cavity to treat distal lesions. Utility Model Content

[0006] In view of the above problems existing in the prior art, the purpose of the utility model is to provide a drug-carrying system mediated by a retractable self-expanding coated stent. The tearable tube surrounds the self-expanding stent, which can better protect the drug coating on the self-expanding stent, reduce the scratching between the self-expanding stent and the device, and reduce the delivery loss; the flexible part and the rigid part of the tearable tube are a unified overall structure, which is convenient for the use of the device; the scouring of the drug coating of the self-expanding stent in the blood can be reduced, and the vascular drug absorption efficiency can be improved. The bare stent is a porous structure, which strengthens the radial force, ensures that the stent can be reliably expanded in the blood vessel and has sufficient support force, so that the stent has better wall adhesion performance in the blood vessel.

[0007] In order to achieve the above purpose, the technical solution adopted by the utility model is:

[0008] A drug-carrying system mediated by a retractable self-expandable coated stent comprises a self-expandable stent, a balloon and a tearable tube, wherein the balloon, the self-expandable stent and the tearable tube are sequentially sleeved from the inside to the outside, the self-expandable stent can actively or passively expand and compress along its radial direction, the self-expandable stent is coated with drugs, the tearable tube comprises a flexible part and a rigid part both of which are cylindrical and coaxially connected, the flexible part can be torn, the flexible part is sleeved outside the self-expandable stent, and the tearable tube causes the flexible part to be torn to release the self-expandable stent through the expansion of the balloon.

[0009] As a further improvement of the above technical solution:

[0010] The flexible portion is provided with two tearable indentation lines, which are symmetrically arranged on the flexible portion, and the length direction of the indentation lines is parallel to the axial direction of the flexible portion.

[0011] The indentation line is composed of a plurality of holes arranged along a straight line and penetrating the side wall of the flexible part. The holes constituting the indentation line include a middle hole, a proximal hole and a distal hole. The middle hole is provided with one, and the proximal holes and the distal holes are each provided with a plurality. The middle hole is located between the proximal hole and the distal hole. The length of the middle hole is greater than the length of the proximal hole and the distal hole. The length directions of the middle hole, the proximal hole and the distal hole are all parallel to the length direction of the flexible part.

[0012] The self-expanding stent includes a bare stent, an inner coating, an outer coating and a drug coating. The bare stent is a cylindrical structure with hollow side walls. The inner surface of the bare stent is connected to the inner coating, and the outer surface is connected to the outer coating. The outer surface of the outer coating is coated with drugs to form a drug coating.

[0013] The bare stent includes a plurality of mesh units, which are connected in sequence to form a cylindrical structure with hollow side walls. The bare stent can actively or passively expand and compress along its radial direction.

[0014] The self-expanding stent also includes a stent distal end display and a stent proximal end display, and the stent distal end display and the stent proximal end display are respectively installed at two ends of the bare stent.

[0015] When in use, the drug-carrying system cooperates with the outer tube, and the balloon, the self-expanding stent, the tearable tube and the outer tube are sleeved in sequence from the inside to the outside.

[0016] The beneficial effects of the utility model are:

[0017] (1) The tearable tube surrounds the self-expanding stent, which can better protect the drug coating on the self-expanding stent, reduce the scratching between the self-expanding stent and the device, and reduce the delivery loss; the flexible part and the rigid part of the tearable tube are a unified overall structure, which is convenient for the use of the device; it can reduce the scouring of the drug coating of the self-expanding stent in the blood and improve the vascular drug absorption efficiency; the tearable tube can be torn in vivo.

[0018] (2) The bare stent has a porous structure, and the porous surface serves as a carrier for the drug coating. The two are combined to obtain a drug-eluting stent. The drug-eluting system can be recovered after use. The stent has sufficient radial force to reliably fit the blood vessel, and at the same time has good delivery performance, and can smoothly enter and exit the outer tube without damaging the blood vessel; a smaller rod width, wall thickness and mesh unit area can be achieved, which is beneficial to improving the flexibility and pushability of the stent; and the contact area between the bare stent and the polymer film (inner coating and outer coating) can be increased. Reducing the wall thickness of the bare stent can reduce the extreme difference between the rod width and the polymer film thickness, making the polymer film closer to the outer surface of the stent, so that the drug coating on the polymer film is better in contact with the blood vessel, thereby improving the drug absorption rate of the target blood vessel; the mesh units are arranged in sequence, which can effectively reduce the friction between the devices, help to improve the conductivity of the stent in the blood vessel, and the flexibility when passing through curved blood vessels; the drug-eluting system can be used for coronary arteries and can also be applied to peripheral blood vessels.

[0019] (3) The multiple mesh units of the main body form a coaxial structure in the length direction and the circumferential direction. The regular cyclic design of the mesh structure strengthens the radial force, ensuring that the stent can be reliably expanded in the blood vessel and has sufficient supporting force. The mesh units of the main body are arranged more evenly, making the inner coating and outer coating on the surface of the bare stent smoother and reducing the defect of the polymer film invagination. The mesh units of the main body are mesh structures with uniform area, which can provide uniform radial force in the circumferential direction, so that the stent has better wall adhesion performance in the blood vessel, thereby making the drug coating on the stent better adhere to the blood vessel. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the coordination structure of the drug carrying system, outer tube and Y valve of the utility model.

[0021] Figure 2 It is a structural schematic diagram of the tearable tube of the utility model.

[0022] Figure 3 It is a structural schematic diagram of the flexible portion of the tearable tube of the utility model.

[0023] Figure 4 It is a schematic diagram of the end surface structure of the self-expanding stent of the utility model.

[0024] Figure 5 It is a schematic diagram of the connection structure of the self-expanding bracket and the pushing rod when the mesh units of the utility model are arranged without dislocation.

[0025] Figure 6 The utility model is a schematic diagram of the cross-sectional structure of the self-expanding stent passing through the keel.

[0026] Figure 7 It is a schematic diagram of the bare stent, stent distal end development and stent proximal end development structure when the mesh units of the utility model are arranged without dislocation.

[0027] Figure 8 It is a schematic diagram of the structure of the self-expanding stent when the mesh units of the utility model are arranged without dislocation and the keel length and the proximal end length are the same.

[0028] Fig. 9 It is a schematic diagram of the structure of the self-expanding stent when the mesh units of the utility model are arranged without dislocation and the keel length is greater than the proximal end length.

[0029] Fig.10 and Fig.11 It is a schematic diagram of the state of the bare stent after being unfolded when the mesh units of the utility model are staggered arranged mesh units.

[0030] Fig.12It is a schematic structural diagram of three adjacent mesh units when the mesh units of the utility model are staggered arrangement mesh units.

[0031] Fig.13 It is a schematic diagram of the structure of mesh units in which the mesh units of the utility model are arranged without dislocation. DETAILED DESCRIPTION

[0032] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0033] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0034] A retractable self-expandable covered stent-mediated drug delivery system, such as Figures 1 to 12 As shown, it includes a self-expanding stent 1, a balloon 6, a tearable tube 8 and a push rod 4. The balloon 6, the self-expanding stent 1 and the tearable tube 8 are sequentially sleeved from the inside to the outside, and the self-expanding stent 1 and the push rod 4 are connected.

[0035] The self-expanding stent 1 can be actively or passively expanded and compressed along its radial direction, and the self-expanding stent 1 is coated with drugs.

[0036] The tearable tube 8 includes a flexible portion 81 and a rigid portion 82. Both the flexible portion 81 and the rigid portion 82 are tubular structures. The flexible portion 81 is flexible and tearable, and is used for pre-installing the self-expanding stent 1. The rigid portion 82 is rigid and cannot be torn, and is used to achieve device support. The flexible portion 81 and the rigid portion 82 are coaxially connected, and the tearable tube 8 as a whole can be transported and withdrawn. The tearable tube 8 can tear the flexible portion 81 to release the self-expanding stent 1 through the expansion effect of the balloon 6. The flexible portion 81 and the rigid portion 82 are connected as a unified whole by welding or hot melting process.

[0037] Both the flexible portion 81 and the rigid portion 82 are composed of a single layer of plastic. Two tearable indentation lines 8-1 are provided on the flexible portion 81. The two indentation lines 8-1 are symmetrically arranged on the flexible portion 81. Specifically, the length direction of the indentation lines 8-1 is parallel to the axial direction of the flexible portion 81, and the plane where the two indentation lines 8-1 are located passes through the center line of the flexible portion 81. The indentation line 8-1 is composed of a plurality of holes arranged along a straight line and penetrating the side wall of the flexible portion 81. Specifically, the holes constituting the indentation line 8-1 include a middle hole 811, a proximal hole 812, and a distal hole 813. The middle hole 811 is provided with one, and the proximal hole 812 and the distal hole 813 are provided with multiple holes. The middle hole 811 is located between the proximal hole 812 and the distal hole 813, that is, one side of the middle hole 811 is a plurality of proximal holes 812, and the other side is a plurality of distal holes 813. The proximal hole 812 is closer to the rigid portion 82 than the distal hole 813. The length of the proximal hole 812 is equal to or similar to the length of the distal hole 813, and the length of the middle hole 811 is greater than the length of the proximal hole 812 and the distal hole 813. Preferably, the length of the middle hole 811 is multiple times the length of the proximal hole 812 or the distal hole 813, which is conducive to the tearing of the flexible portion 81 in the body. The length directions of the middle hole 811, the proximal hole 812 and the distal hole 813 are all parallel to the length direction of the flexible portion 81.

[0038] In this embodiment, the minimum intracavity diameter of the flexible portion 81 is 1.32 mm, and the maximum intracavity diameter is 2.64 mm.

[0039] The self-expanding stent 1 comprises a bare stent 11, an inner coating 13, an outer coating 14 and a drug coating 15. The bare stent 11 is a cylindrical structure with a hollow side wall. The inner coating 13 is connected to the inner surface of the bare stent 11, and the outer coating 14 is connected to the outer surface. The outer surface of the outer coating 14 is coated with drugs to form the drug coating 15.

[0040] The bare stent 11 includes a plurality of mesh units 111, which are sequentially connected to form a hollow side wall of the bare stent 11. The bare stent 11 can be actively or passively expanded and compressed along its radial direction, and the radial direction of the bare stent 11 is perpendicular to the length direction or axial direction of the bare stent 11. Due to the expandability and compression of the bare stent 11, when the bare stent 11 expands along its radial direction, the circumference of the bare stent 11 increases, and the cross-sectional area formed by the circumference increases, and the self-expanding stent 1 can expand to the target blood vessel and adhere to the blood vessel wall, so that the drug in the drug coating 15 on the self-expanding stent 1 is released into the blood vessel wall; when the self-expanding stent 1 contracts along its radial direction, the circumference of the self-expanding stent 1 decreases, and the cross-sectional area formed by the circumference decreases, and the self-expanding stent 1 can contract to break away from the contact with the blood vessel, so as to smoothly remove the self-expanding stent 1 from the blood vessel.

[0041] The self-expanding stent 1 may be symmetrical or asymmetrical, and the length of the self-expanding stent 1 is greater than the diameter of the self-expanding stent 1. In other words, the length of the self-expanding stent 1 is greater than the length perpendicular to the length of the self-expanding stent 1. It should be noted that the length of the self-expanding stent 1 is the length of the bare stent 11.

[0042] The inner coating 13 and the outer coating 14 may have multiple layers, preferably, the inner coating 13 has 1 to 10 layers, and the outer coating 14 has 2 to 12 layers. It should be noted that the drug coating 15 is only coated on the outer surface of the outermost outer coating 14 .

[0043] The drug coating 15 can be one or more layers, and the drug coating 15 includes a drug carrier and a drug that inhibits endothelial hyperplasia. The drug coating 15 is coated on the outer surface of the outer coating film 14 after the carrier and the drug are combined by physical and chemical methods. Due to diffusion, penetration and other effects in the body, the drug coating 15 is continuously and stably released at an appropriate concentration, ultimately allowing the drug to exert its maximum efficacy. The scheme of combining the carrier and the drug by physical and chemical methods can adopt existing technologies and will not be repeated here. Preferably, the drug loading density is (1-7) mg / mm 2 The drug coating 15 is a rapid release type. During the expansion of the self-expanding stent 1, the drug quickly penetrates into the diseased blood vessel and dissolves in the blood, so that the drug directly contacts the diseased blood vessel and is absorbed, achieving the purpose of rapid treatment. In addition to preventing thrombosis and restenosis in the stent, medical urea also has the function of a drug carrier, which can smoothly carry the drug to the diseased site and reduce the drug loss during the drug delivery process.

[0044] The self-expanding stent 1 is open at both ends and has an oblique opening. In other words, the bare stent 11 can be divided into three parts along its length direction, namely, the proximal end 1-1, the distal end 1-2 and the main body 1-3, wherein the main body 1-3 is located between the proximal end 1-1 and the distal end 1-2, the proximal end 1-1 is closer to the push rod 4 than the distal end 1-2, and the proximal end 1-1 is connected to the push rod 4. The proximal end 1-1 and the distal end 1-2 are eccentrically obliquely designed or concentrically designed relative to the main body 1-3. The eccentric oblique opening design refers to the end opening being in an inclined state, rather than the conventional form in which the end face is perpendicular to the axial direction.

[0045] The mesh units 111 may be in various shapes and connected in various ways. In this embodiment, the mesh units 111 include mesh units with staggered arrangement and mesh units with non-staggered arrangement.

[0046] For staggered arrangement of mesh units, each mesh unit 111 includes a plurality of unit rods 1111, such as Figures 10-12As shown, specifically, each mesh unit 111 is surrounded by a plurality of unit rods 1111. In this embodiment, each mesh unit 111 is surrounded by four unit rods 1111 connected end to end in sequence to form a quadrilateral. The unit rods 1111 of adjacent mesh units 111 are tightly fitted and connected, which can provide axial tension during the radial compression process of the self-expanding stent 1, so as to smoothly enter the inner cavity of the outer tube 5 and reduce the friction with the outer tube 5.

[0047] In this embodiment, the unit rod 1111 can be a straight rod or a non-straight rod, and the shape of the mesh unit 111 is a parallelogram or a parallelogram-like shape. The four unit rods 1111 that form a mesh unit 111 include two types, such as Fig.12 As shown, they are respectively a first unit rod 11111 and a second unit rod 11112, the length of the first unit rod 11111 is greater than the length of the second unit rod 11112, the two first unit rods 11111 are two opposite sides of the parallelogram, and the two second unit rods 11112 are the other two opposite sides of the parallelogram. In the main body 1-3, the angle A between the first unit rod 11111 and the second unit rod 11112 of a mesh unit 111 is in the range of 40° to 60°, the angle B between the first unit rod 11111 and the other second unit rod 11112 is in the range of 120° to 140°, and the length X of the first unit rod 11111 is 2 to 6 mm.

[0048] Different from the cross or Y-shaped intersection of the existing mesh, in the main body 1-3, the intersection of adjacent mesh units 111 of the present application is in a T-shape. Fig.10 and 11 As shown, after deployment, the multiple mesh units 111 of the main body 1-3 are arranged in multiple rows and columns. The dotted line in the figure is the center line of the bare stent 11, and the arrangement direction of the multiple mesh units 111 in the same row is parallel to the direction of the center line of the main body 1-3. Fig.11 The multiple mesh units 111 filled with the middle cross-section line are in the same row and are adjacent to each other in sequence. Fig.10 The plurality of mesh units 111 filled with black are in the same column and are adjacent to each other in sequence. The arrangement direction of the mesh units 111 in one column is not perpendicular to the center line direction of the main body 1 - 3 .

[0049] The multiple mesh units 111 in each column are connected in sequence, and the mesh units 111 in two adjacent columns are arranged in a staggered manner. Specifically, in the multiple mesh units 111 in each column, two adjacent mesh units 111 are connected by their respective second unit rods 11112, that is, the second unit rod 11112 of each mesh unit 111 is connected to the second unit rod 11112 of the mesh unit 111 adjacent to the mesh unit 111, and the two second unit rods 11112 connected to each other are arranged in parallel and are flush end to end. The mesh units 111 in two adjacent columns are connected by their respective first unit rods 11111. Specifically, the connection between two adjacent mesh units 111 in a column of mesh units 111 is aligned with the middle of a first unit rod 11111 of a mesh unit 111 in the adjacent column. The alignment is as shown in FIG. Fig.12 At O shown in the figure, the alignment is equivalent to dividing a first unit rod 11111 into two sections, wherein the length of one section accounts for 50-80% of the length of the entire first unit rod 11111, and the alignment is taken as the vertex, and the two sections are the two sides forming an angle, then the angle C of the angle ranges from 170° to 180°. That is, the first unit rod 11111 of a mesh unit 111 connects the first unit rods 11111 of two mesh units 111 in an adjacent row.

[0050] When the self-expanding stent 1 is in a natural state (not subjected to radial compression force and radial expansion force), Fig.12 As shown, the acute angle D between the length direction of the first unit rod 11111 of the mesh unit 111 of the main body 1-3 and the straight line direction parallel to the center line of the main body 1-3 is 20°~60°, and the dotted line in the figure is a straight line parallel to the center line of the main body 1-3.

[0051] Arrange mesh units without misalignment Fig.13 As shown, it includes four unit rods 1111 and four connecting rods 1112, the unit rods 1111 are straight rod-shaped structures, and the connecting rods 1112 are U-shaped rod-shaped structures. The four unit rods 1111 are arranged in a rhombus structure, the four unit rods 1111 are respectively located on the four sides of the rhombus, and the four connecting rods 1112 are respectively located on the four vertices of the rhombus. In other words, each unit rod 1111 is connected to a connecting rod 1112 at both ends, and each connecting rod 1112 connects two adjacent unit rods 1111 of the same mesh unit 111.

[0052] Furthermore, adjacent mesh units 111 share a connecting rod 1112. For the mesh units 111 in the middle of the bare stent 11 that are not at the edge, each connecting rod 1112 is shared by four mesh units 111 that are adjacent in sequence. These four mesh units 111 form a rhombus-like structure, and the shared connecting rod 1112 is located at the center of the rhombus. Specifically, the "U"-shaped opening direction of the connecting rod 1112 is consistent with the circumference of the self-expanding stent 1, and the "U"-shaped opening directions of all connecting rods 1112 are consistent. For the connecting rods 1112 in the middle of the bare stent 11 that are not at the edge, each connecting rod 1112 connects eight unit rods 1111, and the connection points of these eight unit rods 1111 and the connecting rod 1112 are symmetrically arranged on the connecting rod 1112, specifically, with the center line of the connecting rod 1112 (i.e., the center line of the "U"-shaped opening) as the symmetry axis.

[0053] The line connecting two opposite vertices of a rhombus where a mesh unit 111 is located is parallel to the length direction of the self-expanding stent 1, and the other two opposite vertices are on the same circumference line of the self-expanding stent 1. The line connecting two acute angles of the rhombus where each mesh unit 111 of the main body 1-3 is located is parallel to the length direction of the self-expanding stent 1. The regular cyclic design of the mesh structure of the bare stent 11 formed in this way strengthens the radial force, ensuring that the self-expanding stent 1 can be reliably expanded in the blood vessel and has sufficient supporting force.

[0054] The area of ​​the rhombus formed by one mesh unit 111 is 1.5-8.0 mm 2 .like Fig.13 As shown, the rod bending angle α is 20°~70°, that is, the acute angle between two adjacent unit rods 1111 of a mesh unit 111 is 20°~70°.

[0055] The connecting rod 1112 can provide axial tension during the expansion of the self-expanding stent 1 to compensate for the shortening of the mesh unit 111 during the expansion of the self-expanding stent 1. In other words, the reduction in the axial length of the rhombus can be compensated during the expansion of the self-expanding stent 1.

[0056] The design of the mesh unit 111 itself and the interconnected relationship makes the self-expanding stent 1 easier to compress, more adaptable to small blood vessels, and easier to be received in the outer tube 5. It is conducive to the uniform distribution of the mesh wires (i.e., unit rods 1111) in each section of the bare stent 11 and on the periphery of its cross section, so as to provide uniform support force and better expansion effect. Compared with the ordinary quadrilateral structure, such a structure can make the stent mesh unit 111 form a coaxial structure in the length direction and the circumferential direction. Thereby, the mesh arrangement of the main body 1-3 of the stent is flatter, and at the same time, the polymer film on the surface of the bare stent 11 can be flatter, reducing the defect of the polymer film sinking.

[0057] In addition, due to process limitations, if the mesh unit 111 is set to a common quadrilateral (such as a rectangle), the stability of the bare stent 11 is poor, and a larger rod width and wall thickness of the bare stent 11 are required (the rod width of the bare stent 11 refers to the length of the unit rod 1111, and the wall thickness of the bare stent 11 refers to the diameter of the unit rod 1111) to improve stability, that is, the unit rod 1111 needs to be longer and have a larger diameter. Since the rod width of the stent is increased, the area of ​​the mesh unit is also increased. For small stents suitable for coronary arteries, excessively large mesh unit areas lead to poor radial expandability of the bare stent 11. In other words, the same expansion amplitude requires a greater radial force. The design of the structure of the present application can achieve a small rod width and a small stent wall thickness, or even a smaller mesh structure, which is beneficial to improving the flexibility and pushability of the stent.

[0058] In addition, if the mesh unit 111 is smaller in area, the contact area between the bare stent 11 and the polymer film (the inner coating film 13 and the outer coating film 14) can be increased, and reducing the wall thickness of the bare stent 11 can reduce the range between the rod width and the polymer film thickness, so that the polymer film is closer to the outer surface of the stent, so that the drug coating on the polymer film is in better contact with the blood vessel, and the drug absorption rate of the target blood vessel is improved. Moreover, the mesh units 111 are arranged regularly in sequence, which can effectively reduce the friction between the devices, and help improve the conductivity of the self-expanding stent 1 in the blood vessel and the flexibility when passing through the curved blood vessel.

[0059] Each mesh unit 111 of the main body 1-3 is a mesh structure with uniform area, which can provide uniform radial force in the circumferential direction, so that the self-expanding stent 1 has better wall adhesion performance in the blood vessel, so that the drug coating 15 on the self-expanding stent 1 is better attached to the blood vessel. The mesh units 111 on the proximal portion 1-1 are mesh structures with different area sizes, and the mesh units 111 on the distal portion 1-2 are also mesh structures with different area sizes. The area of ​​the mesh units 111 of the proximal portion 1-1 and the distal portion 1-2 is smaller than the area of ​​the mesh units 111 of the main body 1-3, so the radial expansion force of the proximal portion 1-1 and the distal portion 1-2 is smaller than the radial expansion force of the main body 1-3. At the same time, since the proximal portion 1-1 and the distal portion 1-2 are designed with eccentric bevels, this shape makes it easier for the self-expanding stent 1 to enter the outer tube 5. In addition, the design that the area of ​​the mesh unit 111 of the proximal portion 1-1 and the distal portion 1-2 is smaller than the area of ​​the mesh unit 111 of the main portion 1-3 can reduce the "dog bone" effect of the self-expanding stent 1 during the pre-installation process and the expansion process.

[0060] The two ends of the bare stent 11 are also respectively installed with a stent distal end developer 2 and a stent proximal end developer 3. Specifically, the stent distal end developer 2 is installed at the end of the distal end 1-2 away from the main body 1-3, and the stent proximal end developer 3 is installed at the end of the proximal end 1-1 away from the main body 1-3. Obviously, the stent proximal end developer 3 is closer to the push rod 4 than the stent distal end developer 2. The stent distal end developer 2 and the stent proximal end developer 3 are not transparent to X-rays. When the clinician monitors the development that is not transparent to X-rays through vascular imaging equipment such as DSA (digital subtraction angiography), the position of the self-expanding stent 1 in the blood vessel and whether the self-expanding stent 1 is in an expanded or compressed state can be monitored and determined by checking the position of the development, because when the self-expanding stent 1 is in an expanded state, the distance between the stent distal end developer 2 and the stent proximal end developer 3 is less than the distance between the stent distal end developer 2 and the stent proximal end developer 3 when the self-expanding stent 1 is in a compressed state. Preferably, the stent distal end developer 2 is a spring-shaped developer filament, and the developer filament material is preferably platinum-tungsten alloy. The developing filament is wound into a spring shape and has elasticity, which can prevent one end of the self-expanding stent 1 from directly hitting the blood vessel wall and causing damage to the blood vessel due to misoperation when the self-expanding stent 1 is released. The stent proximal end developing 3 can be a spring shape wound by the developing filament or a precious metal developing point with strong developing property.

[0061] The self-expanding stent 1 may also be provided with a keel 12, which is connected to the bare stent 11. Specifically, the keel 12 is a rod-shaped structure. The length direction of the keel 12 is consistent with or parallel to the length direction of the bare stent 11. The cross-section of the keel 12 is preferably circular, and the diameter of the keel 12 is greater than the diameter of the unit rod 1111, that is, the keel 12 is thicker than the unit rod 1111. The two ends of the keel 12 do not exceed the two ends of the bare stent 11, and the length of the keel 12 can be equal to or less than the length of the bare stent 11. When the length of the keel 12 is less than the length of the bare stent 11, only one section of the length direction of the bare stent 11 is connected with the keel 12 instead of the entire length. Preferably, the keel 12 is connected to the proximal portion 1-1. This design can enhance the ability of the proximal portion 1-1 to resist deformation and improve the supporting force of the bare stent 11. Moreover, since the design of only a portion of the bare stent 11 having the keel 12 in the length direction will not affect the overall flexibility and wall adhesion of the bare stent 11. Preferably, the length of the keel 12 is the same as or similar to the length of the proximal portion 1-1, and the keel 12 is only connected to the proximal portion 1-1, so that the bare stent 11 still has good flexibility in the blood vessel, and enhances the support and rigidity of the proximal portion 1-1 of the stent to resist deformation, thereby enhancing the delivery performance of the self-expanding stent 1 in the outer tube 5 (the introduction of the outer tube 5 is described below).

[0062] When the proximal portion 1-1 and the distal portion 1-2 are designed as eccentric bevels relative to the main body 1-3, the cross-section of the self-expanding stent 1 is a trapezoid, and further, an isosceles trapezoid, in the cross-section passing through the straight line where the keel 12 is located and the center line of the main body 1-3. The main body 1-3 is cylindrical, and its outer surface is a cylindrical outer surface. In the cross-section, the main body 1-3 is a rectangle, and the proximal portion 1-1 and the distal portion 1-2 are both triangles. The length direction of the bare stent 11 is parallel to the center line direction of the main body 1-3.

[0063] Preferably, the length of the keel 12 is 4 to 12 mm. The shape of the keel 12 can also be a quadrilateral cross section at one end and a circular cross section at the other end; or a quadrilateral cross section in the middle and a circular cross section at both ends. The portion with a quadrilateral cross section has a length of 0.2 mm to 0.6 mm and a width of 0.2 mm to 0.6 mm. The portion with a circular cross section can be a variable cross section, one end of which is smoothly connected to the portion with a quadrilateral cross section, and the diameter of the other end is 0.06 mm to 0.12 mm. It should be noted that the cross section of the keel 12 can be set to other shapes as needed.

[0064] The setting of the keel 12 improves the radial bearing capacity of the bare stent 11, and the maximum strain during the compression process is effectively reduced, thereby improving the compressibility of the bare stent 11. In addition, the proximal portion 1-1 is connected to the push rod 4. Because the proximal portion 1-1 is designed with an eccentric bevel, the excessive dispersion of force during the pushing process of the push rod 4 will cause the mesh unit 111 of the proximal portion 1-1 to deform greatly. Due to the setting of the keel 12, most of the pushing force of the push rod 4 is concentrated on the keel 12, reducing the deformation of the mesh unit 111 of the proximal portion 1-1. At the same time, the deformation of the proximal portion 1-1 is small, and the absorbed pushing force is small. The pushing force of the push rod 4 can be mostly used to overcome the friction force. Therefore, the setting of the keel 12 also reduces the requirement for the pushing force of the push rod 4.

[0065] The push rod 4 is rod-shaped. Preferably, the push rod 4 can be designed with a variable diameter, and the outer diameter of the push rod 4 increases from the end close to the self-expanding stent 1 to the end away from the self-expanding stent 1. The diameter of the end of the push rod 4 connected to the self-expanding stent 1 is small, ensuring that the end is soft enough and has a smaller curvature radius, so that it can better adapt to tortuous blood vessels. The end of the push rod 4 away from the self-expanding stent 1 has a large diameter, so that the end has a certain hardness, providing support strength when pushing in the outer tube 5. Preferably, the push rod 4 is stepped, that is, it includes multiple sections of straight rods with different diameters.

[0066] The material of the push rod 4 can be selected from 304V stainless steel wire or nickel-titanium alloy, which has good flexibility and resilience, and is convenient for pushing the self-expanding stent 1 to move in a curved blood vessel. Furthermore, the outer surface of the push rod 4 can be coated with a polymer material with a low friction coefficient, which is beneficial to reducing the friction of the push rod. The polymer material with a low friction coefficient includes but is not limited to one or more of polytetrafluoroethylene (PTFE) and polyethylene terephthalate (PET) plastics.

[0067] Furthermore, a support spring is sleeved on the outside of one end of the push rod 4 connected to the self-expanding stent 1, and both ends of the support spring are connected to the push rod 4. The support spring plays a role in strengthening the support strength of the end of the push rod 4 with a smaller diameter, thereby improving the delivery performance of the push rod 4. The material of the support spring can be selected from 304V stainless steel wire or a platinum-containing alloy. In addition, a twister can be designed at the end of the push rod 4 away from the self-expanding stent 1 to enable more flexible operation of the drug-carrying system during surgery.

[0068] Based on the above structure, the working process and principle of the utility model are as follows: when in use, the drug-carrying system cooperates with the outer tube 5, the guide wire 7 and the Y valve 9. The balloon 6 can be inflated. The balloon 6 is sleeved in the inner ring of the self-expanding stent 1, and the end of the balloon 6 close to the push rod 4 is also connected to the push rod 4. A guide wire cavity is provided in the center of the balloon 6 for the guide wire 7 to pass through, and the guide wire cavity is not connected to the inside of the balloon 6. The guide wire 7 is pre-installed in the guide wire cavity of the balloon 6, that is, the guide wire 7 passes through the guide wire cavity.

[0069] The self-expanding stent 1 is pre-installed in the tearable tube 8, and the self-expanding stent 1 is in a compressed state. The tearable tube 8 is sleeved in the outer tube 5. The outer tube 5 is a tubular structure. The outer tube 5, the tearable tube 8, the self-expanding stent 1, and the balloon 6 are fixedly connected by the Y valve 9 so that the devices do not move relative to each other. The principle and scheme of the Y valve 9 are prior art and will not be described in detail here.

[0070] In order to locate and monitor the relative positions of the outer tube 5 , the balloon 6 , the tearable tube 8 and the self-expanding stent 1 , the outer tube 5 , the balloon 6 and the tearable tube 8 may also be provided with a developer.

[0071] Before the operation, the balloon 6, the self-expanding stent 1, the tearable tube 8 and the outer tube 5 are sequentially sleeved from the inside to the outside outside the human body and connected and fixed by the Y valve 9. During the operation, the guide wire 7 is first released to the target blood vessel position, and the balloon 6 can pass the guide wire 7, and the outer tube 5 is transported to the target blood vessel position along the position of the guide wire 7, and the Y valve 9 is released, and then the outer tube 5 is withdrawn, and the tearable tube 8 is placed in the blood vessel, and the flexible part 81 of the tearable tube 8 that wraps the self-expanding stent 1 is torn off by inflating the balloon 6, and the tearable tube 8 is withdrawn through the rigid part 82, and the self-expanding stent 1 is in an expanded state and adheres to the blood vessel wall. When the flexible part 81 is torn off, under the expansion effect of the balloon 6, the flexible part 81 starts to tear off from the middle hole 811, and then the tearing area gradually spreads to the proximal hole 812 and the distal hole 813 until the indentation line 8-1 is completely opened. After the drug on the self-expanding stent 1 is completely released, the self-expanding stent 1 is pulled back to the outer tube 5 by the pushing rod 4 and then withdrawn from the human body.

[0072] The self-expanding stent 1 is made of metal material, mainly medical grade stainless steel such as 316L, 304, 306 and other stainless steels, NITI memory alloy materials, Mg-based alloys, titanium-based alloys, CoCr-based alloy materials such as L605, MP35N, Phynox and the like.

[0073] The materials of the inner coating film 13 and the outer coating film 14 may also be selected from TPU, PU, ​​PTFE, ePTFE, Pebax, nylon, etc.

[0074] The carrier can also be liposome, butylated hydroxytoluene, polylactic acid-glycolic acid copolymer, polylactic acid, mineralized calcium phosphate, a mixture of polylactic acid, and a mixture of the above polymers.

[0075] The main choices of organic polymer materials are: polyethylene and its derivatives, polypropylene and its derivatives, polyfluorine derivatives, polylactic acid and its derivatives, mixtures of polyethylene, polypropylene, polylactic acid and their derivatives; also include biostable materials, biodegradable materials, bioabsorbable materials, etc.

[0076] The main choices of drug materials are: rapamycin and its derivatives, paclitaxel and other anti-proliferative and anti-inflammatory drugs or mixed preparations, etc.

[0077] Finally, it is necessary to explain here that the above embodiments are only used to further illustrate the technical solution of the utility model in detail and cannot be understood as limiting the protection scope of the utility model. Some non-essential improvements and adjustments made by technicians in this field based on the above content of the utility model belong to the protection scope of the utility model.

Claims

1. A retractable self-expandable stent graft-mediated drug delivery system, characterized in that: The invention comprises a self-expanding stent (1), a balloon (6) and a tearable tube (8), wherein the balloon (6), the self-expanding stent (1) and the tearable tube (8) are sequentially sleeved from the inside to the outside, the self-expanding stent (1) can actively or passively expand and compress along its radial direction, the self-expanding stent (1) is coated with drugs, the tearable tube (8) comprises a flexible part (81) and a rigid part (82) both of which are cylindrical and coaxially connected, the flexible part (81) can be torn, the flexible part (81) is sleeved outside the self-expanding stent (1), and the tearable tube (8) causes the flexible part (81) to tear and release the self-expanding stent (1) through the expansion of the balloon (6).

2. The drug delivery system according to claim 1, characterized in that: The flexible portion (81) is provided with two tearable indentation lines (8-1), the two indentation lines (8-1) are symmetrically arranged on the flexible portion (81), and the length direction of the indentation lines (8-1) is parallel to the axial direction of the flexible portion (81).

3. The drug delivery system according to claim 2, characterized in that: The indentation line (8-1) is composed of a plurality of holes arranged along a straight line and penetrating the side wall of the flexible portion (81). The holes constituting the indentation line (8-1) include a middle hole (811), a proximal hole (812) and a distal hole (813). The middle hole (811) is provided with one hole, and the proximal hole (812) and the distal hole (813) are provided with a plurality of holes respectively. The middle hole (811) is located between the proximal hole (812) and the distal hole (813). The length of the middle hole (811) is greater than the lengths of the proximal hole (812) and the distal hole (813). The length directions of the middle hole (811), the proximal hole (812) and the distal hole (813) are all parallel to the length direction of the flexible portion (81).

4. The drug delivery system according to any one of claims 1 to 3, characterized in that: The self-expanding stent (1) comprises a bare stent (11), an inner coating film (13), an outer coating film (14) and a drug coating (15); the bare stent (11) is a cylindrical structure with a hollow side wall; the inner surface of the bare stent (11) is connected to the inner coating film (13), and the outer surface of the bare stent (11) is connected to the outer coating film (14); and the outer surface of the outer coating film (14) is coated with drugs to form the drug coating (15).

5. The drug delivery system according to claim 4, characterized in that: The bare stent (11) comprises a plurality of mesh units (111), and the plurality of mesh units (111) are connected in sequence to form a cylindrical structure with hollow side walls. The bare stent (11) can actively or passively expand and compress along its radial direction.

6. The drug delivery system according to claim 4, characterized in that: The self-expanding stent (1) further comprises a stent distal end developer (2) and a stent proximal end developer (3), and the stent distal end developer (2) and the stent proximal end developer (3) are respectively installed at two ends of the bare stent (11).

7. The drug delivery system according to claim 1, characterized in that: When in use, the drug-carrying system cooperates with the outer tube (5), and the balloon (6), the self-expanding stent (1), the tearable tube (8) and the outer tube (5) are sequentially sleeved from the inside to the outside.

Images