LU503086B1 - Tubular ptfe covered stent and preparation method thereof - Google Patents

Abstract

The invention provides a preparation method of tubular PTFE covered stent, characterized by comprising: S1, preparing tubular PTFE/PEO fibre film by electrospinning method with a braided tube sheathed with a metal mandrel as a receiving device; S2, drying the tubular PTFE/PEO fibre film, and sintering at 360 - 400℃ for 5-15min; S3, providing a metal stent, brushing TPU adhesive on the surface of the metal stent, then sheathing the sintered tubular PTFE fibre film on the metal stent, and putting it into water to remove DMF in the adhesive; secondly, taking out the metal stent, drying, covering the tubular PTFE fibre film with a heat-shrinkable tube, and heating the shrinkable tube to shrink the tubular PTFE fibre film to be more tightly combined with the metal stent, so as to obtain the tubular PTFE covered stent. The tubular PTFE covered stent of the invention has good mechanical properties, water permeability and blood compatibility, the haemolysis rate is lower than 5%, and it can support the adhesion and proliferation of human umbilical vein endothelial cells (HUVECs) without cytotoxicity.

Description

TUBULAR PTFE COVERED STENT AND PREPARATION METHOD 7509086

THEREOF

TECHNICAL FIELD The invention relates to the technical field of vascular covered stents, in particular to a tubular PTFE covered stent and a preparation method thereof.

BACKGROUND Arterial dilating diseases such as pseudoaneurysm caused by trauma, infection, surgery, immune diseases, hypertension, atherosclerosis and other reasons seriously threaten human health. If not treated in time, the thinning blood vessel wall or the tumour wall lacking muscle layer and elastic layer is easy to rupture, and the mortality rate is as high as 78%-95%. The traditional treatment of this kind of disease is open surgery, which has disadvantages such as high risk, great trauma and complicated operation. With the progress of material science, engineering technology and surgical technology, a new type of endoluminal stent-graft isolation was invented. In this technique, the covered stent is used to completely isolate the tumour-bearing artery from the cavity of pseudoaneurysm, and the blood flow through the covered stent cannot enter the cavity. Endovascular stent-graft exclusion has the advantages of less trauma, faster recovery and fewer complications, and is widely used in the treatment of aneurysm and other diseases. The covered stent for endoluminal isolation is a combination of metal stent and covered stent, which not only retains the function of metal stent, but also has the characteristics of covered stent. At present, most covered stents are made of polyester woven fabric, ePTFE, polyurethane, etc. The covered stents made of these materials have defects in blood compatibility, structural stability, etc., which are easy to cause thrombosis or intimal hyperplasia.

Electrospinning technology is a simple and general process, which can prepare fibres with diameters ranging from several nanometres to several micrometres. It has high specific surface area and porosity, is easy to imitate the composition and structure of extracellular matrix, and is conducive to cell growth and proliferation.

However, there is little research on the preparation of vascular covered stent by 7509086 electrospinning technology.

SUMMARY The technical problem to be solved in this invention is to provide a tubular PTFE covered stent prepared by electrospinning method. The covered stent has good mechanical properties and water permeability, the haemolysis rate is lower than 5%, the blood compatibility is good, the adhesion and proliferation of HUVECs cells can be supported, and there is no cytotoxicity, which provides a reference for its later application in endovascular isolation.

To solve the above technical problems, the present invention provides the following technical solutions: À preparation method of tubular PTFE covered stent comprises the following steps: S1, preparing tubular PTFE/PEO fibre film by electrospinning method with a braided tube sheathed with a metal mandrel as a receiving device; S2, drying the tubular PTFE/PEO fibre film, and sintering at 360 - 400°C for 5-15min; S3, providing a metal stent, brushing TPU adhesive on the surface of the metal stent, then sheathing the sintered tubular PTFE fibre film on the metal stent, and putting it into water to remove DMF in the adhesive; secondly, taking out the metal stent, drying, covering the tubular PTFE fibre film with a heat-shrinkable tube, and heating the shrinkable tube to shrink the tubular PTFE fibre film to be more tightly combined with the metal stent, so as to obtain the tubular PTFE covered stent; or taking the metal stent as the receiving device and receiving the tubular TPU electro spun film on the metal stent by electrospinning; then, covering the sintered tubular PTFE fibre film outside the TPU electro spun film, then covering the tubular PTFE fibre film with a heat-shrinkable tube, and heating the heat-shrinkable tube to melt the TPU electro spun film, so that the tubular PTFE fibre film is bonded with the metal stent, thus obtaining the tubular PTFE covered stent.

In PTFE/PEO tubular fibre film, PEO only acts as a weak adhesive to connect 7509086 PTFE particles, but has no effect on tensile force, so PEO needs to be removed. In the invention, the PTFE/PEO tubular fibre film is sintered, the purpose of which is to remove PEO from the fibre film, and at the same time, the PTFE particles are melted to fill the gaps existing in PEO, and finally a complete, continuous and strong PTFE fibre film is obtained.

Further, in S1, the spinning solution used is PTFE/PEO electrospinning solution, and the mass ratio of PTFE to PEO in the spinning solution is 99:1-97:3, preferably 97:3.

Further, in S1, the parameters of electrospinning are: voltage 12-20 kV, injection speed 6-15 ul/min, receiving distance 15-22 cm, rotating speed of receiving device 200-600 r/min, the relative humidity (35+5)-(455)% and the temperature (18+3)-(2543)C.

Further, in S2, the sintering temperature is 360-400°C, preferably 380°C and the sintering time is 5-15 min, preferably 10 min.

Further, in S3, the metal stent is a NiTi alloy stent.

Further, in S3, the TPU adhesive is obtained by dissolving TPU powder in DMF, and its concentration is 18%-25%, preferably 20wt%.

Further, in S3, the temperature of the shrink tube is increased to 140°C-160°C.

The invention also provides a tubular PTFE covered stent prepared by the above method.

Further, the thickness of the tubular PTFE covered stent 1s 0.08-0.14 mm.

The invention also provides an application of the tubular PTFE covered stent as a vascular stent.

Compared with the prior art, the invention has the advantages that: The tubular PTFE covered stent of the invention has good mechanical properties and water permeability, the haemolysis rate is lower than 5%, and the blood compatibility is good. In vitro cell experiments show that tubular PTFE covered scaffold can support the adhesion and proliferation of HUVECs cells without cytotoxicity. The tubular PTFE covered scaffold has potential application value in the 705086 field of tissue engineering.

BRIEF DESCRIPTION OF THE FIGURES Fig. 1 is a flow chart of preparation of tubular PTFE covered stent; Fig. 2 is the morphology of PTFE/PEO precursor film: (a): PTFF:PEO=99:1; (b): PTFF:PEO=98:2; (c): PTFF:PEO=97:3; Fig. 3 is a thermal analysis diagram: (a): DSC curve of PTFE particles; (b): TG curves of PTFE particles, PEO powder, PTFE/PEO precursor film and film after sintering at 380°C; Fig. 4 is the infrared spectrum of PTFE/PEO precursor film before sintering and PTFE film after sintering at 380°C; Fig. 5 is stress and strain of PTFE film at different sintering temperatures and different sintering times, (a): stress, (b): strain; Fig. 6 is the MTT diagram of HUVECs proliferation after 1, 3 and 7 days of culture on each group of materials; Fig. 7 is a confocal image of HUVECs laser cultured on each group of materials for 1, 3 and 7 days; Fig. 8 is the SEM image of HUVECs cultured on each group of materials for 1, 3 and 7 days.

DESCRIPTION OF THE INVENTION The invention will be further explained with reference to the following drawings and specific examples, so that those skilled in the art can better understand the invention and implement it. However, the cited examples should not be taken as a limitation of the invention.

Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the technical field of the present invention. The terminology used in this specification of the present invention is only for the purpose of describing specific embodiments, and is not intended to limit the present invention. As used herein, the term "and/or" includes any and all 7509086 combinations of one or more related listed items.

The experimental methods used in the following examples are conventional unless otherwise specified, and the materials and reagents used can be obtained from 5 commercial sources unless otherwise specified.

In the following examples, the test materials used are as follows: Teflon dispersion emulsion (PTFE, solid content 60%, Suzhou Ketong Biomedical Technology Co., Ltd.), polyethylene oxide (PEO, Mw=5,000,000Da, Suzhou Gretel Medical Technology Co., Ltd.), elastic polyurethane (TPU, BASF, Germany), N, N-dimethylformamide (DMF, Suzhou Ketong Biomedical Technology Co., Ltd), glutaraldehyde (CsHgO,, Shanghai Sinopharm Chemical Reagents Co., Ltd.), fetal bovine serum (FBS, Gibco Company, USA), phosphate buffer solution (PBS, Coring Company, USA), dimethyl sulfoxide (DMSO, Sigma Company, USA), trypsin (EDTA, Gibco Company, USA), fluorescein diacetate (FDA, Sigma Company, USA), double antibody (Streptomycin, Gibco Company, USA), human umbilical vein endothelial cells (HUVECs), thiazole blue (MTT, Shanghai Ruji Biotechnology Development Co., Ltd.), DMEM medium (Corning Company, USA) and 75% ethanol disinfectant (Anhui Ante Food Co., Ltd.).

Example 1

1. Preparation of PTFE/PEO precursor film Using Adventurer electronic balance (Changzhou Aohaus Instrument Co., Ltd.) to weigh appropriate amount of PEO powder, adding it into deionized water, and stirring it with 84-1 magnetic stirrer (Shanghai Meiyingpu Instrument Manufacturing Co, Ltd.) until it is completely dissolved, thus obtaining 4wt% PEO aqueous solution; weighing PTFE dispersion emulsion, mixing PEO aqueous solution with deionized water, and continuously stirring until uniform, so as to obtain electrospinning solution of PTFE/PEO in different proportions, introducing the spinning solution into a 5 mL syringe, and using a mandrel (diameter 4mm) wrapped with braided tube as a receiving device for electrospinning (JDS02 electrospinning machine, Changsha Nayi

Instrument Technology Co., Ltd.); the electrospinning parameters are set as follows: 705086 voltage 15 kV, injection speed 8 ul/min, receiving distance 20 cm, rotating speed of receiving device 400 r/min, relative humidity (40+5)% and temperature (23+3)"C.

2. Preparation of PTFE covered film After electrospinning, putting the mandrel covered with PTFE/PEO fibre film sample into a vacuum oven (DZF-6020B, Tianjin Gongxing Laboratory Instrument Co., Ltd.), and vacuum drying it at 60°C for 10 hours to remove the moisture in the fibre film; after drying, immediately transferring the sample to a box furnace (MF-1200C, Anhui Beiyike Equipment Technology Co., Ltd.) and sintering it at different sintering temperatures and different sintering times, so as to explore the influence of different sintering conditions on the preparation of covered film; after sintering, taking the covered film down from the mandrel, which is the tubular PTFE covered film.

3. Preparation of covered stent The covered stent is prepared by TPU solution brushing method, and the specific operation is as follows: firstly, weighing a proper amount of TPU powder with an electronic balance, adding it into DMF and stirring until it is completely dissolved, so as to obtain 20wt% TPU solution, namely TPU adhesive; after that, as shown in Fig. 1, the TPU adhesive is brushed outside the metal stent, then the tubular PTFE film is sheathed outside the TPU adhesive, put in deionized water to remove DMF from the adhesive, and then put in WGLL-125BE electrothermal constant temperature blast drying oven (Tianjin Tester Instrument Co., Ltd.) for drying for 10 min. After taking it out of the oven, cover the PTFE film on the mandrel, and heat shrink the tube on the PTFE film, adjust the hot air gun (DH-HG2-2000, Delixi Electric Co., Ltd.) to 150°C to heat up the shrink tube, so that the PTFE film and the metal stent contract more tightly, and get the PTFE film stent.

Example 2 LU503086 The difference between Example 2 and Example 1 is that the covered stent is prepared by TPU electrospinning, and the specific operation 1s as follows: A proper amount of TPU powder is dissolved in DMF and stirred until it is completely dissolved to obtain 30wt% TPU electrospinning solution. The electrospinning parameters are set as follows: the voltage is 16-17 kV, the mandrel wrapped with a metal stent is used as a receiving device, the receiving distance is 15 cm, and the flow rate is 13.33 ul/min. After electrospinning for a certain time, the tubular TPU electro spun film is obtained. Then, the sintered tubular PTFE film is sheathed outside the TPU electro spun film, and then a heat-shrinkable tube is added to the outermost layer; the temperature of the hot air gun is raised to heat the heat-shrinkable tube to melt the TPU electro spun film, so that the PTFE film is bonded with the metal stent, and the contraction tube makes the combination of the two more tightly under the action of high temperature, thus obtaining the PTFE covered stent. Testing and characterization

1. Morphology analysis Fig. 2 shows the micro-morphology of electrospinning precursor films with different PTFE:PEO ratios. In spinning solution, PEO is used as a bonding component, which enables PTFE particles to be bonded together under electrostatic spraying to form continuous fibres. It can be seen from Fig. 2 that when the content of PEO in spinning solution is small, continuous fibres cannot be formed; when PTFF:PEO is 99:1, the fibre breaks obviously (Fig. 2a); when the PEO content gradually increases and the PTFF:PEO ratio is 98:2, the fibre breaking point decreases (Fig. 2b); under the condition of keeping the total solid content of spinning solution constant, when the ratio of PTFF to PEO rises to 97:3, continuous unbroken fibre is formed (Fig. 2c).

2. Thermal analysis The PTFE/PEO precursor film prepared by electrospinning is fluffy, with poor mechanical properties, and contains PEO, so it is necessary to sinter it and remove

PEO to obtain PTFE film with certain mechanical strength. Therefore, it is necessary 7509086 to find a suitable sintering temperature by DSC and TG tests of the samples. It can be seen from the DSC curve of Fig. 3(a) that the melting point of PTFE particles is 335.5°C; it can be seen from the TG curve of Fig. 3(b) that PTFE particles begin to decompose at 480°C; pure PEO powder began to decompose at 210°C and completely decomposed at 400°C. TG curve of PTFE/PEO precursor film shows two steps of mass loss, which correspond to the decomposition of PEO and PTFE respectively, and the thermal decomposition temperature of PEO component is the same as that of pure PEO powder. Therefore, the sintering temperature can be selected from 335.5°C to 480°C. In this temperature range, PEO is thermally decomposed, and PTFE can be melted to fill the gap left by the decomposition of PEO, so as to be connected into a complete PTFE fibre.

3. Fourier transform infrared spectroscopy (FTIR) analysis Fourier transform infrared spectroscopy proved that water and PEO are basically removed from PTFE film after sintering, and the results are shown in Fig. 4. It can be seen from the figure that the precursor film before sintering has obvious PEO characteristic peak: There are bands at 962 cm”! and 1105 cm”!, which are attributed to the asymmetric CO stretching vibration of PEO. The bands at 1350 cm“ and 1467 em”! correspond to the CH2 vibration of PEO, and the band at 2880 em”! corresponds to the CH extension of PEO. There is no PEO characteristic peak in the sintered film, but the maximum peaks can be observed at 1201 cm”! and 1145 cm”! in both the precursor film and the sintered film, which corresponds to the asymmetric stretching and symmetric stretching of CF2 in polytetrafluoroethylene, which indicates that PEO in the precursor film has been removed, at least not detectable by FTIR measurement.

4. Analysis of mechanical properties The covered part of the covered stent for endoluminal isolation should also have good mechanical properties. In the PTFE/PEO precursor film, PEO only acts as a connecting component of PTFE particles, but has no effect on bearing tensile force. Therefore, PEO needs to be removed to make the PTFE particles melt to fill the gaps existing in PEO, and finally a complete, continuous and strong PTFE fibre film can be obtained. Therefore, after the range of sintering temperature was determined by DSC 7509086 and TG tests, the effects of sintering temperature and sintering time on the mechanical properties of PTFE covered film are further explored, and different sintering temperatures are set: 360°C, 380°C and 400°C; and different sintering time: 5 min, 10 min and 15 min.

Fig. 5(a) is the stress histogram of the materials manufactured at different sintering times and temperatures, and Fig. 5(b) is the strain histogram of the materials manufactured at different sintering times and temperatures. It can be seen from the figure that the stress and strain of PTFE film at the sintering temperature of 360°C are all smaller than those at the sintering temperature of 380°C, and the sintering time is shorter (5 min) or longer (15 min), and the stress and strain of the film is smaller than that at the sintering time of 10 min. The reason is that the low sintering temperature or short sintering time leads to incomplete melting of PTFE, which can't enter the nanocavity generated after the decomposition of PEO components, so the fibre is incomplete and its mechanical properties are poor; however, too long sintering time will lead to fibre shrinkage and poor mechanical properties. When the sintering temperature is 380°C, the stress and strain of PTFE film are better. When the sintering temperature rises to 400°C, the stress and strain of PTFE film decreases obviously. The reason is that the sintering temperature is too high, which leads to severe shrinkage and fracture of the fibre, and thus the mechanical properties decrease. Therefore, the best tensile mechanical properties are obtained when the sintering temperature is 380°C and the sintering time is 10 min.

5. Water permeability analysis Water permeability is an important characterization index of covered stent for endovascular isolation, which reflects the blood permeability resistance of the tube wall after the stent is implanted in the body, so it is necessary to prepare covered stent with good permeability. Because the water permeability of plastic film is closely related to its thickness, the greater the thickness, the higher the degree of pore coverage, and the less the water permeability. In this invention, tubular PTFE covered scaffolds with different thicknesses are prepared, and the water osmotic pressure and the overall water flux are tested by self-built water permeable device, and the results are shown in Table 1. As can be seen from Table 1, when the thickness 1s about 0.1 mm, the osmotic pressure of water is about 0.012 MPa, which is slightly less than but close to 0.016 MPa of human blood pressure; and at 0.016 MPa, the whole water flux per unit time within 1, 2, 3, 4, 5, 7 and 10 minutes flowing through the effective length of blood vessel wall is 0.02-0.03 ml:em”-min”!, which is far less than the standard of 100 mL'em”-min”!. Therefore, after the covered stent is actually implanted into the human body, a large amount of blood leakage will not occur under normal blood pressure, and at the same time, a small amount of blood can permeate to ensure the growth of the inner film and the supply of nutrition of the outer film; when the thickness increases to about 0.14 mm, the osmotic pressure of water increases to 0.023 MPa, which is higher than the blood pressure of human body, so there will be no infiltration, and the overall water flux at each time point is 0 at 0.016 MPa, which is not conducive to the growth of intima. Therefore, when the thickness is about 0.1 mm, its water permeability meets the requirements. Table 1 Osmotic pressure and overall water penetration of tubular PTFE covered stents with different thickness Wat Thick- | PE osmotic Overall water flux ness . pressure (mLescm?emin™) (mm) (MPa) 1 Toe [ree [oon [oo [oon [oo [oom

0.100 0.0262 + 0.012 + + 0.0250 + | 0.0242 + | 0.0236 + | 0.0233 + | 0.0223 + | 0.0203 +

0.003 0.0024 0.0024 0.0023 0.0029 0.0036 0.0056

0.005 0.0016

0.140

0.023 + +

0.002

0.006

7. Analysis of haemolysis experiment 7903096 The haemolysis of the material can be judged by measuring the degree of red blood cell destruction during its contact with blood in vitro. If the blood compatibility of the material is poor, it is very likely that the red blood cells will rupture and haemolysis will occur. Haemolysis test is an important index to evaluate the blood compatibility of biomaterials. According to ISO 10993-4, the haemolysis rate of materials <5% is considered to meet the requirements of biomedical materials. As shown in Table 2, the haemolysis rate of tubular PTFE covered stent is 2.84%, less than 5%, indicating that the material is safe and will not cause haemolysis.

Table 2 Haemolysis test results of PTFE covered stent and tubular covered stent

6. Cytotoxicity analysis Materials should have good cell compatibility, that is, the adaptability between materials and cells' attachment and growth. The good cellular compatibility of the material can promote the adhesion and endothelialisation of vascular endothelial cells on the surface of the material, and form the vascular endothelial structure in a short time. In the invention, HUVECs cells are planted on the surface of the material, and the growth of endothelial cells is observed.

Fig. 6 is the MTT diagram of cell proliferation on different materials. It can be seen from the diagram that with the increase of culture time, the number of cells on tubular covered scaffold and blank control showed an increasing trend, and the growth rate of cells on tubular covered scaffold was faster. On the 7th day, the number of cells on the covered scaffold was more than that of the blank control, which proved that it had good cell compatibility.

The cell growth on the material was qualitatively characterized by laser confocal 7509086 and scanning electron microscope. As shown in Fig. 7, it can be seen that on the first day of cell inoculation, the cells were evenly distributed on the slide (Fig. 7d), while on the tubular covered stent (Fig. 7a), the cells near the metal stent adhered more than on the covered stent, which also proved that the TPU adhesive used in the present invention was cell compatible. On the 3rd day, similar to the results of MTT test, cell proliferation could be seen more obviously, and more cells were adhered to the covered part of tubular covered stent. On the 7th day (Fig. 7c,f), a large number of cells adhered to the surface of each material, showing a flaky adhesion phenomenon, indicating that endothelialisation began to appear.

Fig. 8 is the SEM image of HUVECs cells growing on tubular covered scaffolds and slides. As can be seen from the figure, on the first day (Fig. 7a,d), the number of cells on the surface of each material is not much. It can be seen from the scanning electron microscope picture with magnification of 2000 that the cells have not spread out at this time. With the increase of culture time, by the 3rd day (Fig. 7b,e), the number of cells on the surface of each material increased, and many cells began to form cell clumps, fused together, and gradually formed cell monolayers to adhere to the fibre web and glass slide. After 7 days of culture (fig. 7c,f), HUVECs cells have spread all over the fibre web and cell slide, and it is very obvious that there is a single layer of cells covering the surface of the material. These results prove that tubular covered scaffolds have no toxicity to HUVECs cells and can support the adhesion and proliferation of endothelial cells.

To sum up, the PTFE:PEO electrospinning solution is prepared by stirring PTFE dispersion emulsion and PEO aqueous solution, and then the PTFE covered film obtained after electrospinning, vacuum drying and sintering can ensure that the PEO component in the PTFE covered film is basically removed, and has good mechanical properties. Then, the tubular PTFE film directly prepared was bonded and thermally shrunk to obtain tubular covered stent. The test proved that it had good water permeability, haemolysis rate lower than 5% and good blood compatibility. In vitro cell experiments showed that tubular PTFE covered scaffold supported HUVECs cell adhesion and proliferation without cytotoxicity.

The tubular PTFE covered stent has 7509086 potential application value in the field of vascular covered stent.

The above-mentioned embodiments are only preferred embodiments for fully explaining the present invention, and the scope of protection of the present invention is not limited thereto.

Equivalent substitutions or changes made by those skilled in the art on the basis of the present invention are within the scope of protection of the present invention.

The scope of protection of the invention is subject to the claims.

Claims (10)

CLAIMS LU503086

1. A preparation method of tubular PTFE covered stent, characterized by comprising: S1, preparing a tubular PTFE/PEO fibre film by electrospinning method with a braided tube sheathed with a metal mandrel as a receiving device; S2, drying the tubular PTFE/PEO fibre film, and sintering at 360 - 400°C for 5-15min; S3, providing a metal stent, brushing TPU adhesive on the surface of the metal stent, then sheathing the sintered tubular PTFE fibre film on the metal stent, and putting into water to remove DMF in the adhesive; secondly, taking out the metal stent, drying, covering the tubular PTFE fibre film with a heat-shrinkable tube, and heating the heat-shrinkable tube to shrink the tubular PTFE fibre film to combine more tightly with the metal stent, so as to obtain the tubular PTFE covered stent; or taking the metal stent as the receiving device and receiving the tubular TPU electro spun film on the metal stent by electrospinning; then, covering the sintered tubular PTFE fibre film outside the TPU electro spun film, covering the tubular PTFE fibre film with a heat-shrinkable tube, and heating the heat-shrinkable tube to melt the TPU electro spun film, so that the tubular PTFE fibre film is bonded with the metal stent, obtaining the tubular PTFE covered stent.

2. The preparation method of tubular PTFE covered stent according to claim 1, characterized in that in S1, the spinning solution used is PTFE/PEO electrospinning solution, and the mass ratio of PTFE to PEO in the spinning solution is 99:1-97:3.

3. The preparation method of tubular PTFE covered stent according to claim 1, characterized in that in S1, the parameters of electrospinning are: voltage 12-20 kV, injection speed 6-15 jl/min, receiving distance 15-22 cm, rotating speed of receiving device 200-600 r/min, relative humidity (35+5)-(45+5)% and temperature (18+3)-(2543)C.

4. The preparation method of tubular PTFE covered stent according to claim 1, characterized in that in S2, the sintering temperature is 380°C and the sintering time is 10 min.

5. The preparation method of tubular PTFE covered stent according to claim 1, 7509086 characterized in that in S3, the metal stent is a NiTi alloy stent.

6. The preparation method of tubular PTFE covered stent according to claim 1, characterized in that in S3, the TPU adhesive is obtained by dissolving TPU powder in DMF, and concentration is 18%-25%.

7. The preparation method of tubular PTFE covered stent according to claim 1, characterized in that in S3, the temperature on the heat-shrink tube is increased to 140°C-160°C.

8. A tubular PTFE covered stent prepared according to any one of claims 1 to 7.

9. The tubular PTFE covered stent according to claim 8, characterized in that the thickness of the tubular PTFE covered stent is 0.08-0.14 mm.

10. An application of the tubular PTFE covered stent of claim 9 as a vascular stent.