Self-healing polyurethane elastomer in liquid environment and preparation method and application thereof

Abstract

The application belongs to the field of polyurethane elastomers, and discloses a self-healing polyurethane elastomer in a liquid environment, and a preparation method and application thereof. The main chain structure of the self-healing polyurethane elastomer is polyurethane-urea with polydimethylsiloxane (PDMS) as a soft segment, diisocyanate and 3,3'-dithiodipropionyl hydrazine (DPH) as hard segments. The hydrophobic PDMS soft segment in the main chain not only provides high elasticity and realizes efficient closure, but also prevents water molecules from penetrating into the polymer network, thereby accelerating the synergistic self-healing process of the dynamic covalent bond (-S-S-) and high-density hydrogen bonds in the hard segment. The self-healing polyurethane elastomer has excellent mechanical properties, biocompatibility and self-repairing ability in a wet environment in vivo, and is particularly suitable for the rapid closure and functional recovery of frequently punctured or damaged parts in biological medical devices such as hemodialysis, artificial blood vessels, heart stents and heart valves.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of polyurethane elastomers, and relates to a self-healing polyurethane elastomer in a liquid environment and a preparation method and application thereof. BACKGROUND

[0002] Polyurethane is known as one of the six synthetic materials in the world. The hard segment in the structure of polyurethane is rich in urethane bonds, and the significant difference between the soft segment and the hard segment in chemical structure and physical properties promotes the formation of a typical microphase separation structure, thereby endowing the material with excellent elasticity, wear resistance and mechanical strength. By regulating the composition and properties of the soft segment, the overall performance of polyurethane can be precisely adjusted. With the above advantages, polyurethane has been widely used in the field of biomedical polymers and has become one of the commonly used functional matrix materials. However, compared with the ability of the living body to automatically repair after injury, traditional polyurethane materials often irreversibly lose structural integrity and function after injury, lacking self-healing ability, which limits their further application in long-term service and intelligent medical devices.

[0003] Self-healing polyurethane provides an innovative solution for the repair of blood vessel damage caused by frequent puncture in hemodialysis, micro-cracks generated by heart stents under pulsatile load, and self-repair of material fatigue and surface damage of heart valves in high-frequency circulation through the multi-level repair mechanism of dynamic reversible chemical bonds and non-covalent interactions. Its self-healing strategy is divided into external self-repair (microcapsule / microtube network triggered release of repair agent) and internal self-repair (construction of self-repairing materials based on dynamic covalent bonds and non-covalent interactions). Given that blood-contacting materials such as artificial blood vessels, heart stents and heart valves have high requirements for biological safety, the release of repair agents poses a potential risk of immunization or blood clotting, and therefore the internal self-repair strategy with integrated structure has a better research and application prospect.

[0004] However, unlike the traditional in vitro self-healing process, the dynamic healing of self-healing polyurethane in the blood-tissue fluid biphasic environment faces the problem of water molecule interference. The main optimization strategies include: (1) introducing dynamic bonds that can be regulated by water molecules, such as catechol-boric acid ester, but the hydrolysis stability needs to be improved; (2) using water molecules as plasticizers to accelerate hydrogen bond reconstruction; (3) using dynamic bonds that are not easily affected by water, such as C-F bond dipole-dipole interaction; (4) enhancing the hydrophobicity of the polymer to reduce water molecule penetration. Although the first two strategies can use the water environment to promote healing, they will weaken the mechanical properties of the elastomer and the self-healing ability under anhydrous conditions. In contrast, increasing the hydrophobicity of the polymer is a more promising research direction. However, increasing the hydrophobicity can improve the mechanical strength and self-healing efficiency, but it can easily lead to the risk of thrombosis and bacterial infection. In addition, the existing materials have a slow repair speed at 37℃, which is difficult to meet the clinical needs of hemodialysis artificial blood vessels within seconds to minutes. Therefore, developing self-healing polyurethane elastomers with high self-healing ability in the body and good biocompatibility is still a key research direction. SUMMARY

[0005] Therefore, in view of the low self-healing efficiency, insufficient biocompatibility, and potential risks of blood clotting and infection in the existing self-healing polyurethane elastomers in liquid environments, the present application aims to design the molecular structure of polyurethane elastomers to prepare self-healing polyurethane elastomers with rapid self-healing ability in blood-tissue fluid biphasic media, which have excellent mechanical properties, biocompatibility, and self-repairing ability in wet environments in the body, and are particularly suitable for use in biological medical devices such as hemodialysis, artificial blood vessels, heart stents, and heart valves for rapid sealing and functional recovery of frequently punctured or damaged parts.

[0006] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0007] The first technical object of the present application is to provide a self-healing polyurethane elastomer, which is a polyurethane-urea with polydimethylsiloxane (PDMS) as the soft segment, and diisocyanate and 3,3'-dithiodipropionyl hydrazine (DPH) as the hard segment.

[0008] Further, the diisocyanate is selected from one or more of isophorone diisocyanate (IPDI), 1,6-hexane diisocyanate (HDI), 4,4'-methylenebis(phenyl isocyanate) (MDI), 2,6-toluene diisocyanate (2,6-TDI), 2,4-toluene diisocyanate (2,4-TDI), and 4,4'-dicyclohexylmethane diisocyanate (HMDI).

[0009] Further, the molar ratio of the polydimethylsiloxane (PDMS), diisocyanate and 3,3'-dithiodipropionohydrazide (DPH) is 1:0.4-2:0.2-1.

[0010] Here, taking diisocyanate IPDI as an example, the preparation process of the self-healing polyurethane elastomer is as follows:

[0011] .

[0012] The self-healing polyurethane endows the material with excellent mechanical strength, toughness and puncture resistance. Among them, the hydrophobic PDMS soft segment in the main chain not only provides high elasticity and realizes efficient closure, but also prevents water molecules from penetrating into the polymer network, thereby accelerating the synergistic self-healing process of the dynamic covalent bond (-S-S-) and high-density hydrogen bond in the hard segment. The self-healing mechanism is shown as follows:

[0013] .

[0014] The second technical object of the present application is to provide a preparation method of the self-healing polyurethane elastomer as described above, which specifically comprises the following steps:

[0015] First, 10 g of 3,3'-dithiopropionic acid methyl ester is dissolved in 100 mL of anhydrous methanol, then 16.18 g of 80% mass fraction hydrazine hydrate solution is slowly added to the above solution, and after reacting at room temperature for 24 h, the suspension is centrifuged to obtain a white product. After the product is washed and dried with anhydrous methanol, a white powder 3, 3-dithiodipropionohydrazide (DPH) is obtained; then a linear self-healing poly (urethane-urea) elastomer (SHPU) is prepared by taking polydimethylsiloxane (PDMS-2000) as a soft segment, isophorone diisocyanate (IPDI) and 3, 3'-dithiodipropionohydrazide (DPH) as a hard segment.

[0016] The third technical object of the present application is to provide an application of the self-healing polyurethane elastomer as described above in a self-healing and puncture type artificial blood vessel.

[0017] The tube wall of the self-healing and puncture type artificial blood vessel has a three-layer composite structure, the middle layer is the self-healing polyurethane elastomer (SHPU) as described above; the inner layer of the tube wall is an anticoagulant hydrogel layer (SBMA-IL), and the outer layer is an antibacterial hydrogel layer (SBMA@PVP-OL).

[0018] The self-healing polyurethane elastomer is prepared into a self-healing polyurethane pipeline by extrusion molding, 3D printing and mold method, wherein the inner diameter of the pipeline is 1.5-30 mm, the thickness of the pipeline wall is 50-2000 µm, and the shape of the pipeline includes straight cylinder, cone, bifurcation and step.

[0019] Optionally, the anticoagulant hydrogel layer is formed by grafting and crosslinking polymerization of the zwitterionic monomer and the water-soluble crosslinking agent in a water solution on the surface of the intermediate polyurethane substrate which is pre-activated by the surface initiator; the water solution contains the zwitterionic monomer, the water-soluble crosslinking agent and the water-soluble initiator;

[0020] wherein the polymer coating has a friction coefficient < 0.005 in water medium and a surface Young's modulus of 10-60 kPa; the zwitterionic monomer is at least one or more of methacryloyl ethyl sulfobetaine, 2-methacryloyloxyethyl phosphocholine, and carboxybetaine methacrylate; the water-soluble crosslinking agent is a combination of a chemical crosslinking agent and a physical crosslinking agent; the chemical crosslinking agent is at least one or more of N, N-methylenebisacrylamide, N, N-bis(acryloyl)cystamine, ethylene glycol dimethacrylate, and carboxybetaine dimethacrylate; the physical crosslinking agent is selected from N-acryloylglycine amide; the surface initiator is one of benzophenone, 4-methylbenzophenone, isopropyl thioxanthone, benzoyl peroxide, or azobisisobutyronitrile; and the water-soluble initiator is a photo initiator or a thermal initiator selected from one of Irgacure-2959, α-ketoglutaric acid, ammonium persulfate, or potassium persulfate.

[0021] Optionally, the preparation process of the antibacterial hydrogel layer on the polyurethane substrate surface is as follows:

[0022] the antibacterial hydrogel layer is formed by grafting and crosslinking polymerization of N-vinylpyrrolidone (NVP), the physical crosslinking agent N-acryloylglycine amide (NAGA), the zwitterionic monomer, and the chemical crosslinking agent in a water solution on the surface of the intermediate polyurethane substrate which is pre-activated by the surface initiator; and after polymerization, the outer surface coating is immersed in an iodine-ethanol solution to obtain an outer surface antibacterial coating through complexation of NVP and iodine ions.

[0023] the zwitterionic monomer is at least one or more of methacryloyl ethyl sulfobetaine, 2-methacryloyloxyethyl phosphocholine, and carboxybetaine methacrylate;

[0024] the chemical crosslinking agent is at least one or more of N, N-methylenebisacrylamide (MBA), N, N-bis(acryloyl)cystamine (MSBA), ethylene glycol dimethacrylate (EBA), and carboxybetaine dimethacrylate (CBBA).

[0025] Further, the concentration of the zwitterionic monomer in the raw material of the antibacterial hydrogel layer is 5 wt%-10 wt%, the concentration of the vinyl pyrrolidone is 5 wt%-40 wt%, the chemical crosslinking agent accounts for 0 wt%-20 wt% of the mass of the vinyl pyrrolidone monomer, the physical crosslinking agent N-acryloyl glycine amide accounts for 0 wt%-50 wt% of the mass of the vinyl pyrrolidone monomer, and the water-soluble initiator accounts for 0.5 wt%-20 wt% of the mass of the vinyl pyrrolidone monomer; and the water-soluble initiator Irgacu-2959 accounts for 8 wt% of the mass of the vinyl pyrrolidone monomer.

[0026] After the outer surface coating is formed, the concentration of the impregnated iodine-ethanol solution is 1 wt%-10 wt%, and the soaking time is 1-8 hours.

[0027] The self-healing mechanism of the inner and outer coatings is as follows:

[0028] .

[0029] A fourth technical object of the present application is to provide an application of the self-healing polyurethane elastomer as described above in a valve leaflet of a prosthetic heart valve.

[0030] The valve leaflet of the prosthetic heart valve has a three-layer composite structure, the middle layer is the self-healing polyurethane elastomer (SHPU) as described above, and the inner and outer layers are both anticoagulant hydrogel layers;

[0031] The material composition and surface modification process of the anticoagulant hydrogel layer are the same as above.

[0032] Compared with the prior art, the present application has the following beneficial effects:

[0033] (1) Excellent liquid environment self-healing performance

[0034] The material of the present application can realize fast and reliable self-repairing in liquid environments such as blood and tissue fluid, breaking through the problem of weak self-healing performance and low efficiency of existing polyurethane in body fluids, and significantly improving the sealing performance and safety of implanted devices under conditions such as puncture and damage.

[0035] (2) Intrinsic self-healing mechanism, high safety

[0036] The material does not need external repair agents or stimulating conditions, relies on the reversible action between molecular chains to realize spontaneous repair at room temperature, avoids the risk of repair agent leakage, and is more suitable for long-term implantation and high-safety medical device applications.

[0037] (3) Multifunctional integration, strong adaptability

[0038] Through the design of layered structure, the material has multiple properties such as anticoagulation, antibiosis and lubrication, meets multiple requirements in complex physiological environment, and has good mechanical strength and processing adaptability, and is suitable for large-scale preparation of multiple types of instruments such as artificial blood vessels and artificial heart valves. BRIEF DESCRIPTION OF DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by the drawings provided by the person skilled in the art without creative labor.

[0040] Figure 1 Self-healing polyurethane elastomer prepared in Example 1 1 H-NMR.

[0041] Figure 2 Stress-strain curves of samples with different PDMS-2000, IPDI, DPH ratios (P:I:D).

[0042] Figure 3 Compliance and burst pressure of the self-healing polyurethane pipeline prepared in Example 1.

[0043] Figure 4 Self-healing process of the self-healing polyurethane elastomer prepared in Example 1 in PBS solution.

[0044] Figure 5 SEM images of the self-healing process of the self-healing polyurethane elastomer prepared in Example 1 in PBS solution after puncture and scratch.

[0045] Figure 6 SEM images of the cross section of the self-healing polyurethane pipeline after coating modification.

[0046] Figure 7 Iodine ion cumulative release curve of the outer layer antibacterial hydrogel coating over time.

[0047] Figure 8 Comparison chart of continuous sterilization performance of the pipeline surface before and after antibacterial coating modification.

[0048] Figure 9 SEM images of the hydrogel coating on the inner and outer surfaces at different times after puncture.

[0049] Figure 10 Analysis of the patency performance of the artificial blood vessel prepared in Example 1 implanted in the pig carotid artery for 9 months.

[0050] Figure 11Cross-sectional SEM image of a prosthetic heart valve leaflet prepared for Example 11. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0052] Herein, the term "embodiment" is used as "exemplary" to explain any embodiment, which is not necessarily construed as superior or better than other embodiments. In the performance index test of the embodiments of the present application, unless otherwise specified, the conventional test method in the art is adopted. It should be understood that the terms described in the present application are only for describing the specific embodiments, and are not used to limit the disclosure of the present application.

[0053] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by a person of ordinary skill in the art to which the present application belongs; and the test methods and technical means not specially noted in the present application refer to the test methods and technical means commonly used by a person of ordinary skill in the art.

[0054] In order to better illustrate the content of the present application, a large number of specific details are given in the specific embodiments below. A person of ordinary skill in the art should understand that the present application can also be implemented without some specific details. In the embodiments, some methods, means, instruments, devices and the like which are well known to a person of ordinary skill in the art are not described in detail, in order to highlight the main idea of the present application.

[0055] The technical features disclosed in the embodiments of the present application can be combined in any way without conflict, and the technical solutions obtained by the combination belong to the disclosure of the embodiments of the present application.

[0056] The present application discloses a preparation method of self-healing polyurethane elastomer in liquid environment and its application in self-healing and instant type artificial blood vessels and artificial heart valves.

[0057] In order to better understand the present application, the present application will be further specifically described by the following embodiments, but it should not be understood as a limitation of the present application. Some non-essential improvements and adjustments made by a person of ordinary skill in the art based on the above disclosure are also regarded as falling within the protection scope of the present application.

[0058] Example 1

[0059] Preparation of self-healing polyurethane elastomer:

[0060] Preparation of self-healing polyurethane elastomer: 10 g of 3,3'-dimethylthiopropionate was first dissolved in 100 mL of anhydrous methanol, and then 16.18 g of an 80% mass fraction hydrazine hydrate solution was slowly added dropwise to the above solution. After reacting at room temperature for 24 h, the suspension was centrifuged to obtain a white product. The product was washed and dried with anhydrous methanol to obtain a white powder, 3,3-dithiodipropionyl hydrazine (DPH). Then, a linear self-healing poly (urethane-urea) elastomer (SHPU) was prepared using polydimethylsiloxane (PDMS-2000) as the soft segment, isophorone diisocyanate (IPDI) and 3, 3'-dithiodipropionyl hydrazine (DPH) as the hard segment.

[0061] By adjusting the molar ratio of PDMS-2000, IPDI and DPH, different self-healing polyurethanes were prepared, wherein the molar ratio of PDMS-2000, IPDI and DPH in the self-healing polyurethane prepared in this embodiment was 1:1.4:0.4, and the specific preparation method was as follows:

[0062] 5 g of PDMS was added to a three-necked flask, and nitrogen was introduced three times to remove air. The flask was heated to 100°C under vacuum and stirred for 2 h to remove moisture. Then, the temperature was lowered to 80°C, 0.796 g of IPDI and 0.04 g of catalyst dibutyltin dilaurate (DBTDL) were dissolved in 5 mL of toluene, and the mixture was slowly added dropwise to the three-necked flask under nitrogen. After 3 h of reaction, 0.238 g of DPH was dissolved in a mixture of 35 mL of N,N-dimethylacetamide (DMAc) and 30 mL of toluene, and the mixture was added dropwise to the above reaction system under nitrogen. The reaction was stirred for 4 h. After the reaction was completed, a certain viscosity and colorless transparent polymer solution was obtained. After the reaction system was cooled to room temperature, the polymer solution was poured into a surface dish and dried in a 70°C oven for 12 h to remove the toluene and DMAc solvents, and a colorless transparent self-healing polyurethane elastomer was obtained.

[0063] Preparation of self-healing polyurethane pipeline: self-healing polyurethane elastomers can be prepared into self-healing polyurethane pipelines by extrusion molding, 3D printing and mold method. The following takes 3D printing as an example.

[0064] The synthesized self-healing polyurethane elastomer samples were first cut into blocks, and then processed into 1.75 mm diameter wires using a micro-extruder for fused deposition modeling (FDM) 3D printing. The nozzle temperature of the micro-extruder was set to 140 °C, and the extrusion speed was 10 rpm. Using a computer design system, a FDM printer with a nozzle diameter of 0.4 mm was used to print a self-healing polyurethane elastomer pipeline with a diameter of 5 mm and a wall thickness of 200 µm to meet the needs of different indications scenarios. The chemical composition, mechanical properties, and self-healing properties of the prepared self-healing polyurethane elastomer pipeline are shown in Table 1 and Table 2. Figures 1-5 and Table 1:

[0065] Table 1 Performance of self-healing polyurethane pipeline prepared in Example 1

[0066]

[0067] Self-healing efficiency: ratio of original sample fracture strain after 2 minutes of repair after complete cutting in a 37 °C PBS solution

[0068] Preparation of internal surface anti-coagulation coating: according to the applicant's previously granted patent (CN116003692B), the prepared self-healing polyurethane elastomer pipeline was washed and completely dried using nitrogen flow. Then, one end of the pipeline was closed, and a benzophenone ethanol solution was poured into the other end, and soaked at 25 °C for 3 minutes. Then, the excess benzophenone and ethanol solution was recovered, washed, and dried using nitrogen.

[0069] Then, a zwitterionic polymer precursor solution was prepared. The specific steps were to dissolve methacrylic acid sulfobetaine (SBMA), N-acryloyl glycine amide (NAGA), chemical crosslinker carboxybetaine dimethyl acrylate (CBMAX), and photoinitiator Irgacure 2959 in deionized water. In the precursor solution, the SBMA content was 20wt%, the physical crosslinker NAGA accounted for 20% of the mass percentage of zwitterions; the chemical crosslinker CBMAX accounted for 10% of the mass percentage of zwitterions, and the photoinitiator Irgacure 2959 accounted for 10% of the mass percentage of zwitterions. Finally, one end of the pipeline with a benzophenone-activated surface was closed, and a zwitterionic polymer precursor solution was injected into the lumen of the pipeline from the other end, and a wavelength of 365 nm ultraviolet light was uniformly irradiated on the pipeline. Then, the adsorbate on the inner surface of the self-healing polyurethane elastomer pipeline was repeatedly washed with a large amount of deionized water to prepare SBMA-IL on the inner surface of the self-healing polyurethane elastomer pipeline. The treated sample was dried with nitrogen at room temperature.

[0070] Preparation of the outer surface antibacterial coating: After the outer surface of the tube was cleaned, it was dried with a nitrogen stream. Then the tube was sealed at both ends with clamps and immersed in a solution of benzophenone in ethanol for 5 min. The sample was then rinsed with deionized water and alcohol to remove unreacted benzophenone, and dried with N2. Then the tube was immersed in a prepolymer solution composed of N-vinyl pyrrolidone (NVP), NAGA, SBMA, N, N’ -methylene bisacrylamide (MBA) and a photoinitiator (Irgacu-2959) and polymerized under 365 nm ultraviolet light to form a hydrogel polymer on the surface of the tube. The concentration of the zwitterionic monomer in the prepolymer solution was 8 wt %, the concentration of vinyl pyrrolidone was 20 wt %, the chemical crosslinking agent accounted for 7 wt % of the mass of the vinyl pyrrolidone monomer, the physical crosslinking agent N-acryloyl glycine amide accounted for 25 wt % of the mass of the vinyl pyrrolidone monomer, and the water-soluble initiator accounted for 8 wt % of the mass of the vinyl pyrrolidone monomer. After the outer surface coating was formed, the tube with the above-mentioned outer surface hydrogel coating was immersed in a 5 wt % iodine ethanol solution for 6 h, wherein I2 existed in the form of H + I3 - and was complexed and stably attached to the surface of the hydrogel coating by forming hydrogen bonds with the amide groups in the hydrogel coating. To remove free iodine on the substrate, it was first washed with ethanol 3 times, then immersed in n-heptane for 24 h, and continuously washed until the washing liquid was colorless and no free iodine was detected by ultraviolet-visible spectroscopy (UV-Vis). SBMA@PVP-OL was prepared on the outer surface of the self-healing polyurethane elastomer tube. Then the prepared SH-ECG was dried under a nitrogen stream and sterilized by H2O2 low temperature plasma, and finally packaged.

[0071] Examples 2-5

[0072] The method of Example 1 was used, and the operation was the same as that of Example 1, except that the soft and hard segment ratio of the polyurethane used in the intermediate layer (PDMS-2000: IPDI: DPH, hereinafter referred to as P: I: D) was changed. The tensile strength, burst pressure, compliance, suture strength, and self-healing rate of the polyurethane with different soft and hard segment ratios and the natural blood vessels were measured. As shown in Table 2.

[0073] Table 2 Performance of self-healing polyurethane tubes prepared with different ratios of soft and hard segments in Examples 2-5

[0074]

[0075] As can be seen from Table 2, with the increase of the hard segment content, the tensile strength, burst pressure and suture strength of the material are all increased, but the compliance and self-healing rate are decreased. When PDMS-2000: IPDI: DPH = 1: 1.4: 0.4, the mechanical properties of the pipeline match the natural blood vessels, and the healing rate is 85% ± 7%, which meets the requirements of artificial blood vessels.

[0076] Examples 6-10

[0077] According to the method of Example 1, the operation is the same as Example 1, except that the type of diisocyanate is changed, and the physical and chemical properties of the self-healing polyurethane pipeline prepared by different types of diisocyanate are measured.

[0078] Table 3 Performance of self-healing polyurethane pipeline prepared by different types of diisocyanate prepared in Examples 6-10

[0079]

[0080] IPDI: isophorone diisocyanate; HDI: 1, 6-hexane diisocyanate; MDI: 4, 4'-methylene bis (phenyl isocyanate); 2, 6-TDI: 2, 6-toluene diisocyanate; 2, 4-TDI: 2, 4-toluene diisocyanate; HMDI: 4, 4'-dicyclohexyl methane diisocyanate

[0081] As can be seen from Table 3, with the introduction of benzene ring or the increase of steric hindrance effect in diisocyanate, the tensile strength, suture strength and burst pressure of the material are increased, the compliance is decreased, and the self-healing efficiency is decreased.

[0082] Example 11

[0083] According to the preparation method of self-healing polyurethane of Example 1, the operation is the same as Example 1, except that the polyurethane is molded in a mold to form a self-healing polyurethane elastomer sheet, and then the inner and outer surfaces are modified with an anticoagulant coating as described in Example 1 to prepare an artificial heart valve leaflet.

[0084] In addition, the self-healing polyurethane elastomer prepared by the present application and its application in artificial blood vessels and heart valve leaflets, and the characterization method thereof are disclosed, and the specific content is as follows:

[0085] (1) Tensile strength test: The tensile strength of the samples was evaluated using a universal testing machine (Instron, Norwood, MA, USA) equipped with a 2519-104 load cell. The test included ultimate tensile strength and radial loading-unloading behavior. During the test, the sample was mounted between two sets of parallel hooks made of stainless steel wire with a diameter of 1 mm in the radial direction. A 50 N load cell was used, and the loading rate was set to 2 mm / min until the sample broke.

[0086] (2) Self-healing efficiency: The self-healing polyurethane vascular graft sample was cut into a long strip with a size of 50 mm x 10 mm and immersed in a 37°C phosphate-buffered saline (PBS) solution for 10 minutes for pre-hydration. Then, the sample was broken along its width direction and quickly aligned the cutting interface to achieve initial closure. The sample was taken out after 2 minutes of immersion in PBS while keeping the interface in contact, and then the tensile performance test was performed to evaluate the self-healing ability of the material.

[0087] Needle puncture and scratch test: The sample was cut along the longitudinal direction and pre-treated in a 37°C phosphate-buffered saline (PBS) solution. Then, a syringe needle was used to create multiple holes and scratches on the surface of the sample to simulate mechanical damage. After the damage treatment, the sample was kept in the 37°C PBS solution and sampled at the set time points to observe its self-healing behavior. To prevent the self-healing process from continuing after sampling, the sample was immediately cooled to -20°C and freeze-dried after each sampling to effectively terminate the self-healing reaction. All samples treated at different time points were observed and analyzed under a scanning electron microscope (SEM) to evaluate the repair effect of scratches and holes and other damage.

[0088] (3) Compliance test: The compliance test device consists of a programmable syringe pump and a pressure monitoring table, which is used to control and record the deformation behavior of the lumen structure under different internal pressures. By adjusting the liquid injection and withdrawal rate of the syringe pump, the pressure in the closed fluid circuit can be accurately controlled. During the test, the diameter change of the sample was measured using a vernier caliper. The compliance was characterized by the relative radial expansion degree under a unit pressure difference, and the calculation formula was as follows:

[0089]

[0090] where P1 is the low pressure value and P2 is the high pressure value, both in mmHg. RP1 and RP2 represent the diameters at pressures P1 and P2, respectively. The compliance is expressed as the percentage of diameter change per 100 mmHg.

[0091] (4) Burst pressure test: After the sample was fully swelled in phosphate buffered saline (PBS) to an equilibrium state, it was connected to a pressure loading device. Subsequently, PBS solution was injected into the sample lumen at a constant rate of 50 mmHg / s, so that the internal pressure continued to rise and tend to be stable. The internal pressure change was monitored in real time during the pressurization process, and when the sample ruptured, the corresponding instantaneous pressure value was recorded as the burst pressure of the material.

[0092] (5) Suture strength test: A suture with a type of 8-0 was used to penetrate the blood vessel wall from the end of the artificial blood vessel to form a fixed point 2 mm inward. Subsequently, a constant tensile load was applied to the suture at a rate of 50 mm / min until the suture completely penetrated the artificial blood vessel wall. The maximum tensile force required during this process was recorded, which was used as an indicator of the suture strength of the artificial blood vessel.

[0093] (6) Fatigue resistance test: To evaluate the fatigue resistance of the artificial blood vessel, a pulsatile accelerated fatigue test method was used. Under the condition of constant temperature 37℃, the artificial blood vessel sample was connected to a pulsatile fatigue test device (model: INVS-06, manufacturer: CARE Measurement & Control Co., Ltd), and physiological saline was injected into the lumen as the circulating medium. By the device, a periodic pulse load with a frequency of 50 Hz and a pressure range of 80-160 mmHg was applied to make the sample run continuously to 380 million cycles. The diameter and compliance of the sample were measured and compared before and after the test to determine its fatigue resistance under long-period dynamic loading.

[0094] (7) Analysis of coating surface morphology and thickness: Field emission scanning electron microscopy (model: HITACHI S-4800, manufacturer: Hitachi) was used to observe and characterize the surface morphology and cross-sectional thickness of the sample coating. To improve the electrical conductivity of the sample and obtain clear images, the sample surface was coated with metal for about 60 seconds under inert gas (argon) protection before scanning. Then, under the imaging parameters of accelerating voltage set to 3 kV and working distance controlled within 10-15 mm, high-resolution images of the coating surface and cross-section were obtained to evaluate the microstructure characteristics and thickness uniformity.

[0095] (8) Protein adhesion test: The determination of protein adsorption amount used BCA protein quantification method, and the reagent used was BCA protein detection kit. This method is based on the following principle: in an alkaline environment, the peptide bond in the protein can reduce Cu + to Cu + , and the generated Cu +Ions can form purple complex with two molecules of BCA (Bis-Cyclohexane Tetraacetic Acid). The complex has a strong absorption peak at 562 nm wavelength, and the absorbance value is linearly related to the protein concentration. The model protein used in this experiment is bovine serum albumin (BSA). According to the requirements of the kit instructions, prepare standard BSA solutions with different concentration gradients, the concentration range is 0, 2.5, 5, 10, 20, 40, 200 μg / mL, and measure the light absorption value of each standard solution at 562 nm. Draw the standard curve with absorbance as the abscissa and protein concentration as the ordinate for subsequent quantitative analysis of protein adsorption in samples.

[0096] (9) Surface Young's modulus test: The surface mechanical properties of the zwitterionic polymer coating modified on the substrate surface were determined by a desktop nanoindentation test equipment (model: PIUMA), and the specific test index was Young's modulus. During the test, a spherical indenter with a radius of 48.5 mm was selected, and the coating sample previously soaked in PBS solution was loaded for detection. The test area was 100 μm × 100 μm, and data acquisition was performed by 5 × 5 matrix method with a point spacing of 20 μm, so as to realize fine scanning and evaluation of the Young's modulus distribution in the area.

[0097] (10) Surface friction coefficient test: The friction coefficient of the sample surface was determined by a CSM friction and wear tester. Before testing, the sample was pre-soaked in deionized water at 25°C to ensure that it was in a stable wet state. During the test, a glass ball with a diameter of 3 mm was used as the loading probe, and it was moved on the sample surface at a sliding speed of 30 mm / min, and the sliding stroke was set to 20 mm. The friction coefficient was calculated by ratio of the real-time recorded friction force to the applied normal load (800 μN).

[0098] (11) Platelet adhesion test: Firstly, the peripheral blood was treated by using commercial platelet separation kit to separate the platelet-rich plasma (PRP) from the fresh whole blood collected from New Zealand white rabbits. The treated sample and PRP were co-incubated at 37°C for 2 hours to complete the process of platelet contacting with the material surface. Then, the sample was divided into non-washing group and PBS washing group, and was fixed in 2.5% glutaraldehyde solution for 2 hours. After fixation, the sample was dehydrated by gradient ethanol solution with concentrations of 50%, 60%, 70%, 80%, 90% and 100% for 30 minutes for each gradient. After dehydration, all samples were naturally dried at room temperature for 24 hours. The dried sample was observed by scanning electron microscope (SEM, model: HITACHI S-4800, Hitachi Company). By analyzing the morphology of platelets on the surface of the non-washing group, the influence of the material surface on platelet activation was evaluated. At the same time, the number of residual platelets in the washing group was observed to determine the anti-platelet adhesion performance of the coating.

[0099] (12) Anti-bacterial performance / anti-bacterial adhesion performance test: Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus were selected as pathogenic bacteria models. The artificial blood vessels with the outer surface modified with the anti-bacterial coating were immersed in a 24-well plate containing 1 mL of Escherichia coli or Staphylococcus aureus suspension (1 × 10 8 CFU / mL) and incubated in a 37°C constant temperature incubator for 12 hours. After removing the bacterial solution, the surface was washed with PBS solution for 3 times to remove the bacteria not adhered to the surface, and then immersed in a PBS solution containing 4% glutaraldehyde and stored at 4°C overnight. Then, the sample was dehydrated by gradient ethanol with concentrations of 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% and 100% for 20 minutes for each gradient. Finally, the bacterial adhesion on the surface of the catheter was observed by scanning electron microscopy to determine the anti-bacterial adhesion effect of the coating.

[0100] In order to quantitatively evaluate the anti-bacterial adhesion effect of the coating, 1 mL of bacterial suspension (1 × 10 8 CFU / mL) was co-cultured with the artificial blood vessels after ultraviolet sterilization for 30 minutes at 37°C constant temperature incubator for 12 hours. Then, all the catheters were washed with sterile PBS for 3 times to remove the loosely adhered bacteria. Next, all the samples were treated with ultrasonic wave in 2 mL of sterile PBS solution to separate the firmly adhered bacteria on the surface of the sample. After repeating the above process 5 times, 10 mL of PBS containing bacteria was collected. After diluting the bacteria to an appropriate concentration, the bacteria were inoculated on LB agar plate and cultured in a 37°C constant temperature incubator for 12 hours. The number of bacterial colonies was determined by plate counting method to compare and evaluate the anti-bacterial adhesion effect of the coating.

[0101] Since the iodine ions in the coating are complexed by hydrogen bonds, the iodine element can be released in vivo to kill bacteria, so the bactericidal effect of the system in vitro is evaluated.

[0102] 100 μL of E. coli or S. aureus suspension (1 x 10 8 CFU / mL) was inoculated into LB agar medium, and then the sample subjected to ultraviolet sterilization for 30 min was placed on the medium and cultured in a 37°C constant temperature incubator for 12 h, and the formation of the inhibition zone was observed.

[0103] To quantitatively determine the bactericidal effect of the coating, the sample subjected to ultraviolet sterilization for 30 min was immersed in 1 mL of E. coli or S. aureus suspension (1 x 10 8 CFU / mL), and after 12 hours of culture in a 37°C constant temperature shaker, the sample was taken out, the co-cultured suspension was moderately diluted, inoculated onto LB agar plates, and cultured in a 37°C constant temperature incubator for 12 h, and the number of colonies formed was determined by plate counting to evaluate the in vitro bactericidal effect of the coating.

[0104] (13) Pig carotid artery end-to-end anastomosis experiment: 3-4 month-old male Bama pigs weighing 55-75 kg were selected as experimental animals. Induced anesthesia was performed by intramuscular injection of ketamine (dose: 20 mg / kg) and thiopental (dose: 2 mg / kg), and then fentanyl and propofol were injected through the ear vein to maintain general anesthesia. The animal was connected to a positive pressure ventilator for respiratory support during the operation, and the oxygen supply rate was set to 1.2 L / min.

[0105] During the operation, the skin of the neck was first incised and the target carotid artery was separated, then the proximal and distal segments were clamped with two hemostatic forceps, the middle segment was cut off, and the artificial blood vessel was end-to-end anastomosed with the cut end of the carotid artery using 6-0 monofilament suture. After the operation was completed, the muscle layer, subcutaneous tissue and skin were sutured layer by layer using absorbable monofilament suture. The material was taken out 9 months after the operation for histological analysis to evaluate the biological response of the implant.

[0106] After the implantation of the artificial blood vessel, non-invasive detection was performed using Doppler ultrasound imaging to evaluate the patency of the blood flow. The detection was performed using a veterinary digital color Doppler ultrasound diagnostic system (SIUI Apogee 3100V, China) in the superficial structure imaging mode. The implantation site of the artificial blood vessel was determined according to the anatomical location of the carotid artery and the synchronous pulse wave. The ultrasound examination obtained three-dimensional color flow images, pulse synchronous signals and real-time blood flow velocity data; among them, the red and blue colors in the Doppler flow spectrum indicate the antegrade and retrograde directions of blood flow, respectively.

[0107] Specifically, Figure 1The stress-strain curve of the self-healing polyurethane elastomer prepared in Example 1 1 H-NMR. The protons on the primary and secondary amines were observed at δ = 4.21 ppm and δ = 9.07 ppm, respectively, and two sets of methylene protons were observed at δ = 2.4 ppm and δ = 2.89 ppm. The area ratio of the four sets of peaks was 2:1:2:2. Analysis confirmed that the designed healing polyurethane elastomer was successfully prepared. Figure 1 The protons on the primary and secondary amines were observed at δ = 4.21 ppm and δ = 9.07 ppm, respectively, and two sets of methylene protons were observed at δ = 2.4 ppm and δ = 2.89 ppm. The area ratio of the four sets of peaks was 2:1:2:2. Analysis confirmed that the designed healing polyurethane elastomer was successfully prepared.

[0108] Figure 2 The stress-strain curves of samples with different PDMS-2000, IPDI, DPH ratios (P:I:D). The stress-strain curves of samples with different PDMS-2000, IPDI, DPH ratios (P:I:D). Figure 2 It can be seen that when PDMS-2000: IPDI: DPH = 1: 2: 1, the maximum breaking stress of the material can reach 10 Mpa, and the strain is close to 650%, indicating that it has high toughness and strength. With the decrease of hard segment content, the maximum breaking stress of the material decreases, but the toughness rises.

[0109] Figure 3 The compliance and burst pressure of the self-healing polyurethane pipeline prepared in Example 1.

[0110] Figure 5 The SEM images of the self-healing polyurethane elastomer prepared in Example 1 during the healing process after puncture and scratch in PBS solution. The SEM images of the self-healing polyurethane elastomer prepared in Example 1 during the healing process after puncture and scratch in PBS solution. Figure 5 It can be seen that in the PBS solution at 37℃, after being completely cut off, the SHPU has basically completed self-repairing after only 2 minutes, indicating that it has the characteristics of self-repairing in a liquid environment.

[0111] Figure 6 The SEM images of the cross-section of the self-healing polyurethane pipeline after coating modification. The SEM images of the cross-section of the self-healing polyurethane pipeline after coating modification. Figure 6 It can be seen that the SBMA-IL anticoagulant coating and the SBMA@PVP-OL antibacterial coating can uniformly modify the inner and outer surfaces of the polyurethane elastomer pipeline and form a tight bond with the substrate without gaps.

[0112] Figure 7 The curve of the cumulative release amount of iodine ions in the outer layer of the antibacterial hydrogel coating with time. The curve of the cumulative release amount of iodine ions in the outer layer of the antibacterial hydrogel coating with time. Figure 7 It can be seen that the outer layer of the antibacterial coating can maintain the release of iodine ions for more than a week, while early postoperative infection after artificial blood vessel arteriovenous fistula surgery usually occurs 5-7 days after surgery, which can meet the clinical anti-infection needs.

[0113] Figure 8 The comparison chart of the continuous sterilization performance of the pipeline surface before and after the modification of the antibacterial coating. The comparison chart of the continuous sterilization performance of the pipeline surface before and after the modification of the antibacterial coating. Figure 8 It can be seen that the outer layer of the antibacterial coating has good sterilization effect.

[0114] Figure 9SEM images of the inner and outer surface hydrogel coating at various times after puncture. From Figure 9 As can be seen, the inner and outer coating layers substantially self-heal within 20 minutes after puncture.

[0115] Figure 10 Analysis of the patency of the artificial blood vessel prepared in Example 1 implanted in the carotid artery of a pig for 9 months. From Figure 10 As can be seen, the artificial blood vessel maintains patency for a long period of time after implantation in the body.

[0116] The above description of disclosed embodiments enables one of ordinary skill in the art to make or use the application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. Use of a self-healing polyurethane elastomer for the preparation of a self- healing ready-to-use vascular prosthesis, characterized in that, The self-healing polyurethane elastomer is a polyurethane-urea with polydimethylsiloxane as soft segment, diisocyanate and 3,3'-dithiodipropionohydrazide as hard segment; The tube wall of the self-healing ready-to-use artificial blood vessel has a three-layer composite structure, and the middle layer is the self-healing polyurethane elastomer; The inner layer of the tube wall of the self-healing ready-to-use artificial blood vessel is an anticoagulant hydrogel layer, and the outer layer is an antibacterial hydrogel layer; The preparation process of the antibacterial hydrogel layer on the surface of the polyurethane base is as follows: vinylpyrrolidone, a physical crosslinking agent N-acryloyl glycine amide, a zwitterionic monomer, and a chemical crosslinking agent are simultaneously initiated on the surface of the pre-activated intermediate layer polyurethane base and in an aqueous solution to form a polymer, and after polymerization, the outer surface coating is immersed in an iodine-ethanol solution to obtain an antibacterial coating on the outer surface through the complexation of vinylpyrrolidone and iodine ions; the zwitterionic monomer is at least one or more of methacryloyl ethyl sulfobetaine, 2-methacryloyloxyethyl phosphocholine, and carboxybetaine methacrylate; and the chemical crosslinking agent is at least one or more of N,N-methylene bisacrylamide, N,N-bis(acryloyl) cystamine, ethylene glycol dimethacrylate, and carboxybetaine dimethacrylate.

2. Use of the self-healing polyurethane elastomer according to claim 1 for the preparation of self-healing ready-to-use artificial blood vessels, characterized in that, The preparation method of the self-healing polyurethane elastomer specifically comprises the following steps: first, 10 g of 3,3'-dithiopropionic acid methyl ester is dissolved in 100 mL of anhydrous methanol, then 16.18 g of an 80% mass fraction hydrazine hydrate solution is slowly added to the above solution, and after reacting at room temperature for 24 h, the suspension is centrifuged to obtain a white product, which is washed and dried with anhydrous methanol to obtain a white powder of 3,3-dithiodipropionohydrazide; then, a linear self-healing poly(urethane-urea) elastomer is prepared with polydimethylsiloxane as the soft segment, isophorone diisocyanate and 3,3'-dithiodipropionohydrazide as the hard segment.

3. Use of the self-healing polyurethane elastomer according to claim 1 for the preparation of self-healing ready-to-use artificial blood vessels, characterized in that, The diisocyanate is selected from one or more of isophorone diisocyanate, 1,6-hexane diisocyanate, 4,4'-methylenebis(phenyl isocyanate), 2,6-toluene diisocyanate, 2,4-toluene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

4. Use of the self-healing polyurethane elastomer according to claim 1 for the preparation of a self-healing ready-to-use artificial blood vessel, characterized in that, The molar ratio of the polydimethylsiloxane, diisocyanate, and 3,3'-dithiodipropionohydrazide is 1:0.4-2:0.2-1.

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