A composite coating suture and method of making the same

Abstract

The application provides a composite coating suture and a preparation method thereof, and the method comprises the following steps: immersing a suture substrate into a Tris-HCl buffer solution containing dopamine hydrochloride, and performing reaction under oscillation and in dark to form a polydopamine adhesion layer; adding a silver nanoparticle dispersion liquid with polyvinylpyrrolidone modified surface into the buffer solution reaction system, so that the final mass concentration of the silver nanoparticles in the reaction system is 1.0-2.0 wt%, and the oscillation reaction is continued for 8-12 hours, so that the silver nanoparticles are embedded into the polydopamine matrix through chelation to obtain a suture with a polydopamine-silver nanoparticle composite coating, and then the suture is immersed into a polytetrafluoroethylene dispersion liquid and subjected to ultrasonic treatment for 3-10 minutes; after being taken out, the suture is vertically hung and dried; and then the suture is subjected to heat treatment for 0.5-2 hours to form a polydopamine-silver nanoparticle / polytetrafluoroethylene composite coating suture. The application can simultaneously realize long-lasting lubrication, high-efficiency antibiosis, high interface bonding strength and excellent wear resistance, so that tissue drag is significantly reduced and postoperative infection is effectively inhibited.

Description

Technical Field

[0001] This invention belongs to the field of suture technology, specifically relating to a composite coated suture and its preparation method. Background Technology

[0002] Existing sutures can be classified into three types based on their structure: twisted, braided, and monofilament. Twisted and braided sutures, due to their prominent grooves and burrs, generate significant friction when passing through tissue, easily causing tissue dragging and deformation. Simultaneously, these grooved structures can trap blood, tissue fluid, and bacteria due to capillary action, increasing the risk of postoperative infection. To address this issue, monofilament sutures, with their relatively smooth surface, are widely used, reducing friction and bacterial retention to some extent. However, monofilament sutures cannot be processed to be too thick; otherwise, difficulties in bending and loose knots will arise in clinical use, limiting their application.

[0003] In recent years, barbed sutures have been developed and used clinically. These sutures achieve knotless fixation by creating barbs on the surface of the monofilament, thus simplifying surgical procedures and reducing knot-related complications. However, the barbing process weakens the overall tensile strength of the suture; simultaneously, the barbed edges still increase tissue resistance, and bacterial accumulation at the base of the barbs cannot be prevented, thus limiting their clinical application.

[0004] In terms of antibacterial modification, existing technologies mainly adopt the following three strategies:

[0005] (1) Physical incorporation of silver nanoparticles. For example, Chinese patent CN106835688A discloses an antibacterial suture in which silver nanoparticles are directly incorporated into the suture and its preparation method. Although this method can endow the suture with broad-spectrum antibacterial activity, the exposed silver nanoparticles significantly increase the surface roughness of the suture, leading to an increase in the coefficient of friction, which in turn aggravates tissue damage; moreover, the silver particles are easy to detach, posing a potential risk of cytotoxicity.

[0006] (2) Surface coating with chitosan. For example, Chinese patent CN111514366A proposes coating the surface of sutures with a chitosan antibacterial layer. The antibacterial activity of chitosan is closely related to its concentration: at low concentrations, the antibacterial effect is insufficient, and the degradation products of chitosan may even promote bacterial growth by providing nutrients for bacteria; at high concentrations, the mechanical properties of the sutures are significantly reduced, making it clinically impractical.

[0007] (3) Loading small molecule antibacterial drugs. For example, Chinese patent CN117062634A discloses a technical solution for loading antibacterial drugs into sutures by impregnation or coating. However, the burst release and long-term use of antibacterial drugs can easily lead to the emergence of drug-resistant strains, and drug residues may cause local tissue toxicity, making it difficult to guarantee safety.

[0008] In view of this, the present invention proposes a composite coated suture and its preparation method, which can simultaneously achieve long-lasting lubrication, efficient antibacterial properties, high interfacial bonding strength and excellent wear resistance, thereby significantly reducing tissue drag and effectively inhibiting postoperative infection. Summary of the Invention

[0009] To address the problems of excessively high surface friction coefficient of existing sutures leading to tissue dragging damage, easy bacterial retention and infection caused by groove structures, and mechanical performance degradation / drug resistance / toxicity of existing antibacterial coatings, this invention provides a composite coated suture and its preparation method to solve the above-mentioned technical defects.

[0010] The technical solution adopted by this invention to solve its technical problem is as follows:

[0011] In a first aspect, the present invention provides a method for preparing a composite coated suture, the method comprising the following steps:

[0012] S1. Immerse the suture matrix in Tris-HCl buffer containing dopamine hydrochloride and react under shaking conditions in the dark for 1-3 hours to form a polydopamine adhesion layer; add a dispersion of silver nanoparticles modified with polyvinylpyrrolidone to the buffer reaction system to make the final mass concentration of silver nanoparticles in the reaction system 1.0-2.0 wt%, and continue shaking for 8-12 hours to allow the silver nanoparticles to embed into the polydopamine matrix through chelation, thereby obtaining a suture with a polydopamine-silver nanoparticle composite coating;

[0013] S2. Immerse the suture with the polydopamine-silver nanoparticle composite coating obtained in step S1 into a polytetrafluoroethylene dispersion and sonicate it for 3-10 minutes. After removal, hang it vertically to dry for 24-48 hours in an environment of 25-30℃ and relative humidity <50%. Then heat it to 300-340℃ at 4-6℃ / min and keep it at that temperature for 0.5-2 hours to form a polydopamine-silver nanoparticle / polytetrafluoroethylene composite coated suture.

[0014] Preferably, before step S1, a pretreatment step of the suture substrate is included: placing the suture substrate in anhydrous ethanol, ultrasonically cleaning it at a frequency of 40-60 kHz for 5-15 minutes, and then vacuum drying it at 40-60°C for 1-2 hours.

[0015] Preferably, in step S1, the concentration of the Tris-HCl buffer is 8-12 mM, the pH value is 8.2-8.8, and the pH value is adjusted using 0.1-1 M NaOH solution.

[0016] Preferably, in step S1, the concentration of dopamine hydrochloride in the buffer solution is 1.5-2.5 mg / mL, and it is dissolved by magnetic stirring at 20-30°C for 10-30 minutes until completely dissolved.

[0017] Preferably, in step S1, the oscillation reaction is carried out in a constant temperature oscillator at a temperature of 35-39°C and a rotation speed of 120-180 rpm, and the light-proof condition is achieved by wrapping the reaction vessel with aluminum foil.

[0018] Preferably, in step S1, after the reaction is completed, the suture with the polydopamine-silver nanoparticle composite coating is cleaned, including the following three stages: first, rinsing with deionized water for 30-60 seconds, then rinsing with ultrapure water under 40kHz ultrasonic conditions for 1-2 minutes, and finally rinsing with anhydrous ethanol for 10-20 seconds.

[0019] Preferably, in step S2, the polytetrafluoroethylene dispersion is pretreated before use: first, it is ultrasonically dispersed in a water bath at 25-35°C for 5-15 minutes, and then filtered through a 200-400 mesh sieve to remove agglomerates.

[0020] Preferably, in step S2, the heat treatment is carried out in a muffle furnace, the oxygen concentration in the furnace is controlled at 18-22%, and after the heat treatment is completed, the furnace is cooled to below 50°C and the product is removed.

[0021] Preferably, after step S2, a post-processing step is included: the obtained composite coated suture is irradiated under a UV lamp for 15-30 minutes for surface sterilization, and then vacuum sealed.

[0022] In a second aspect, the present invention proposes a composite coated suture, which is prepared by any of the above preparation methods. The surface of the composite coated suture has a polydopamine-silver nanoparticle / polytetrafluoroethylene composite coating. The composite coating includes a polydopamine-silver nanoparticle intermediate layer bonded to the suture substrate and a polytetrafluoroethylene outer layer covering thereon.

[0023] In summary, compared with the prior art, the composite coated suture and its preparation method provided by the present invention have the following beneficial effects:

[0024] (1) Significantly improved lubrication performance: The outer polytetrafluoroethylene layer provides the suture with a durable low-friction surface, which greatly reduces resistance during tissue passage and effectively reduces tissue drag and damage.

[0025] (2) Long-lasting and efficient antibacterial activity: The polydopamine-silver nanoparticle intermediate layer can continuously release antibacterial factors during clinical use, maintaining broad-spectrum and efficient inhibition of common pathogens, and significantly reducing the risk of postoperative infection.

[0026] (3) Significantly improved interfacial bonding strength: Polydopamine is used as a "molecular glue" to firmly anchor polytetrafluoroethylene to the substrate, the coating is tightly bonded to the substrate, and there is no risk of falling off during the stitching and knotting process.

[0027] (4) Significantly enhanced wear resistance: The composite structure effectively inhibits the propagation of microcracks in polytetrafluoroethylene, ensuring that the coating remains intact after repeated friction and extending the effective service life of the stitching.

[0028] (5) Excellent biocompatibility: All materials used are medical grade, and the silver nanoparticles are stably encapsulated by polydopamine, with no release of free particles; no small molecule drugs are used, avoiding cytotoxicity and drug resistance issues.

[0029] (6) Strong process compatibility: The preparation conditions are mild and suitable for a variety of absorbable and non-absorbable suture substrates. The process steps are simple and easy to scale up production and clinical application. Attached Figure Description

[0030] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0031] Figure 1 This is a flowchart of the method for preparing composite coated sutures according to the present invention;

[0032] Figure 2 This is a scanning electron microscope image of the PDA and PTFE film on a suture substrate according to the present invention. Detailed Implementation

[0033] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, only the parts relevant to the invention are shown in the accompanying drawings.

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] Figure 1 A flowchart illustrating the preparation method of the composite coated suture of the present invention is shown, as follows: Figure 1 As shown, the method for preparing the composite coated suture of the present invention includes the following steps:

[0036] S1. Immerse the suture matrix in a Tris-HCl buffer solution containing dopamine hydrochloride and react under shaking conditions in the dark for 1-3 hours to form a polydopamine adhesion layer. Add a dispersion of silver nanoparticles with polyvinylpyrrolidone modified on the surface (preferably with a particle size of 15-30 nm) to the buffer reaction system to make the final mass concentration of silver nanoparticles in the reaction system 1.0-2.0 wt%. Continue shaking reaction for 8-12 hours to allow the silver nanoparticles to embed into the matrix through the chelation effect of the catechol groups of polydopamine, thereby obtaining a suture with a polydopamine-silver nanoparticle composite coating.

[0037] Before step S1, a pretreatment step for the suture substrate is also included: the suture substrate is placed in anhydrous ethanol, ultrasonically cleaned at a frequency of 40-60 kHz for 5-15 minutes, and then vacuum dried at 40-60℃ for 1-2 hours.

[0038] In step S1, the suture matrix is ​​one of polyglycolic acid, polylactic acid, polydioxanone, polypropylene, or filament. The concentration of the Tris-HCl buffer is 8-12 mM, and the pH value is 8.2-8.8. The pH value is adjusted using 0.1-1 M NaOH solution. The concentration of dopamine hydrochloride in the buffer is 1.5-2.5 mg / mL. During dissolution, the solution is magnetically stirred at 20-30°C for 10-30 minutes until completely dissolved. The shaking reaction is carried out in a constant temperature shaker at 35-39°C and a rotation speed of 120-180 rpm. The light-protected conditions are achieved by wrapping the reaction vessel with aluminum foil. After the reaction, the suture with the polydopamine-silver nanoparticle composite coating is cleaned, including the following three stages: first, rinsing with deionized water for 30-60 seconds; then, rinsing with ultrapure water under 40 kHz ultrasonic conditions for 1-2 minutes; and finally, rinsing with anhydrous ethanol for 10-20 seconds to rapidly dehydrate and promote drying.

[0039] S2. Immerse the suture with the polydopamine-silver nanoparticle composite coating obtained in step S1 into a polytetrafluoroethylene dispersion and sonicate it for 3-10 minutes. After removal, hang it vertically to dry for 24-48 hours in an environment of 25-30℃ and relative humidity <50%. Then heat it to 300-340℃ at 4-6℃ / min and keep it at that temperature for 0.5-2 hours to form a polydopamine-silver nanoparticle / polytetrafluoroethylene composite coated suture.

[0040] In step S2, the polytetrafluoroethylene dispersion undergoes pretreatment before use: it is first ultrasonically dispersed in a water bath at 25-35℃ for 5-15 minutes, and then filtered through a 200-400 mesh sieve to remove agglomerates. Heat treatment is carried out in a muffle furnace, with the oxygen concentration controlled at 18-22%. After heat treatment, the suture is cooled to below 50℃ and removed. Following step S2, a post-treatment step is also included: the obtained composite-coated suture is irradiated under ultraviolet light for 15-30 minutes for surface sterilization, and then vacuum-sealed.

[0041] The present invention also proposes a composite coated suture, which is prepared by any of the above preparation methods. The surface of the composite coated suture has a polydopamine-silver nanoparticle / polytetrafluoroethylene composite coating. The composite coating includes a polydopamine-silver nanoparticle intermediate layer bonded to the suture matrix and a polytetrafluoroethylene outer layer covering thereon.

[0042] The thickness of the polydopamine-silver nanoparticle interlayer is 80-150 nm, and the silver nanoparticles are uniformly distributed in the polydopamine matrix with a distribution density of 500-2000 particles / μm. 2 The outer layer of polytetrafluoroethylene has a thickness of 0.5-2 μm, a surface roughness Ra < 0.1 μm, and a bonding strength with the intermediate layer ≥ 5 MPa.

[0043] Example 1

[0044] This embodiment provides a method for preparing a composite coated suture, the specific steps of which are as follows:

[0045] S1. Take 5-0 PGA absorbable monofilament suture (0.15mm diameter) as the matrix and pre-treat it: place it in anhydrous ethanol and ultrasonically clean it at a frequency of 40kHz for 10 minutes, and then vacuum dry it at 50℃ for 1.5 hours.

[0046] A 10 mM Tris-HCl buffer solution with pH 8.5 was prepared, and dopamine hydrochloride was added to achieve a concentration of 2 mg / mL. The solution was magnetically stirred at 25°C for 20 minutes until completely dissolved. The pretreated sutures were immersed in this solution and placed in a constant-temperature shaker. The reaction was carried out at 37°C and 150 rpm in the dark for 2 hours. Subsequently, a PVP-modified silver nanoparticle dispersion (concentration 3.2 mg / mL, particle size 20 ± 5 nm) was added dropwise to bring the AgNPs concentration in the system to 1.0%. The reaction was continued under the same conditions for 10 hours. After the reaction, the sutures were rinsed sequentially with deionized water for 45 seconds, ultrasonically cleaned with ultrapure water (40 kHz) for 1.5 minutes, rinsed with anhydrous ethanol for 15 seconds, and finally air-dried in clean air at 25°C for 12 hours to obtain PDA-AgNPs-coated sutures.

[0047] S2. Immerse the above suture in a 10wt% PTFE dispersion (preferably DuPont). TM DISP 30 (pre-treated by ultrasonication in a 30℃ water bath for 10 minutes and passing through a 300-mesh sieve) was then ultrasonicated for 5 minutes at 100W power and 40kHz frequency. After removal, it was vertically suspended and dried in an environment of 25℃ and 45% relative humidity for 24 hours. Then, it was transferred to a muffle furnace and heated to 300℃ at a rate of 5℃ / min, held at that temperature for 1 hour, and then cooled to room temperature with the furnace. Finally, the resulting composite-coated suture was sterilized by irradiation under a UV lamp for 20 minutes and vacuum-sealed.

[0048] Performance testing was performed on the product of this embodiment:

[0049] 1. Abrasion resistance test: Using a YG(B)401E fiber friction and wear tester, the composite-coated suture was wound with a certain tension onto a 5mm diameter stainless steel friction column. A radial load of 2N was applied, and reciprocating friction was performed at a frequency of 200 times / minute. The number of cycles before the composite-coated suture broke was recorded. The results showed that the number of cycles before breakage was 3520.

[0050] 2. Lubricity Test: Using a UMT-TriboLab friction and wear tester, the composite coated suture sample was fixed, and a standard medical silicone rubber sheet (Shore A hardness 50) was used to press the sample firmly with a force of 2.5N. The suture was then vertically pulled at a speed of 500mm / min, and the dynamic friction force was recorded and the average coefficient of friction was calculated. The results showed that the coefficient of friction was 0.13.

[0051] 3. Interfacial Shear Strength Test: Using the microsphere debonding method, a single composite-coated suture was vertically embedded into an epoxy resin microsphere (approximately 3 mm in diameter) and cured. A diamond probe was used to push the fiber end at a rate of 0.5 mm / min, and the maximum debonding force F was recorded. The interfacial shear strength (IFSS) was calculated using the formula τ = F / (π × d × L) (where d is the diameter of the composite-coated suture and L is the length of the composite-coated suture embedded in the resin). The results showed that the interfacial shear strength was 5.8 MPa.

[0052] 4. Antibacterial Performance Test: According to GB / T 20944.3-2008 "Evaluation of Antibacterial Properties of Textiles - Part 3: Shaking Method", Staphylococcus aureus (ATCC 6538) and Escherichia coli (ATCC 25922) were used as test bacteria. 0.75g of the composite-coated suture sample was added to an Erlenmeyer flask containing 5mL of bacterial suspension (concentration 1.0×10^5~10^6 CFU / mL). After shaking at 150rpm for 4 hours at 37℃, the bacterial suspension was collected for viable cell counting. The results showed that the inhibition rate against both Staphylococcus aureus and Escherichia coli was >99.5%.

[0053] Example 2

[0054] The difference between this embodiment and Embodiment 1 is that the mass concentration of AgNPs in the system is 2.0%, the concentration of PTFE dispersion is 2 wt%, and the heat treatment temperature is 340℃. Specifically, in step S1, silver nanoparticle dispersion is added to achieve a mass concentration of 2.0%; in step S2, 2 wt% PTFE dispersion is used, and the heat treatment is performed by raising the temperature to 340℃ at a rate of 5℃ / min and holding for 1 hour. The remaining steps and parameters are the same as in Embodiment 1.

[0055] The product of this embodiment was subjected to performance testing using the same method as in Example 1. The results showed that the wear resistance test showed a wear breakage cycle of 8980 times; the coefficient of friction was 0.10; the coating interface shear strength was 6.5 MPa; and the inhibition rate against Staphylococcus aureus and Escherichia coli was >99.8%.

[0056] Example 3

[0057] The difference between this embodiment and Embodiment 1 is that the mass concentration of AgNPs in the system is 1.5%, the concentration of PTFE dispersion is 5 wt%, and the heat treatment temperature is 320℃. Specifically, in step S1, silver nanoparticle dispersion is added to achieve a mass concentration of 1.5%; in step S2, 5 wt% PTFE dispersion is used, and the heat treatment is performed by raising the temperature to 320℃ at a rate of 5℃ / min and holding for 1 hour. The remaining steps and parameters are the same as in Embodiment 1.

[0058] The product of this embodiment was subjected to performance testing using the same method as in Example 1. The results showed that the wear resistance test showed a wear breakage cycle of 6250 times; the coefficient of friction was 0.09; the coating interface shear strength was 6.2 MPa; and the antibacterial rate against both test bacteria was >99.6%.

[0059] Comparative Example 1

[0060] This comparative example provides a suture coated only with a PDA coating: except for the absence of AgNPs nanoparticles and the subsequent PTFE coating step, the remaining steps are the same as in Example 1. That is, only the PDA (dopamine solution) deposition in step S1 is performed for 2 hours, and the product is obtained after washing and drying after the reaction is completed.

[0061] The comparative product was subjected to performance testing using the same method as in Example 1. The results showed that the wear resistance test showed a wear breakage cycle of 3010 times; the coefficient of friction was 0.35; the coating interface shear strength was 2.8 MPa; and the inhibition rates against Staphylococcus aureus and Escherichia coli were 85.5% and 82.3%, respectively.

[0062] Comparative Example 2

[0063] This comparative example provides a suture coated only with PTFE: step S1 is omitted, and step S2 (PTFE coating, 10wt% concentration, heat treatment at 320°C) is applied directly to the pretreated suture substrate, with the remaining parameters the same as in Example 1.

[0064] The comparative product was subjected to performance testing using the same method as in Example 1. The results showed that the number of grinding cycles was 3500; the coefficient of friction was 0.12; the interfacial shear strength of the coating was 2.1 MPa; and the inhibition rate against both test bacteria was <10%.

[0065] Comparative Example 3

[0066] This comparative example provides a suture coated with a PDA-AgNPs composite coating (excluding the PTFE outer layer): its preparation steps are exactly the same as step S1 in Example 1, that is, the PTFE coating in step S2 is not performed.

[0067] The comparative product was subjected to performance testing using the same method as in Example 1. The results showed that the wear resistance test showed a wear breakage cycle of 2950 times; the coefficient of friction was 0.36; the coating interface shear strength was 3.0 MPa; and the inhibition rate against Staphylococcus aureus and Escherichia coli was >99.7%.

[0068] The table below summarizes the performance test results for each embodiment and comparative example (all results are the average of three independent tests):

[0069]

[0070] The test results of the above examples and comparative examples show that the composite coated suture preparation method provided by the present invention can obtain products with excellent lubricity, antibacterial properties, high bonding strength, and wear resistance by adjusting the process conditions within a wide range of parameters. Example 2 (AgNPs 2.0%, PTFE 2wt%, 340℃) exhibits the best comprehensive performance, with more than 2.5 times the wear resistance of the comparative example, a friction coefficient reduced to 0.10, an interfacial bonding strength of 6.5MPa, and an antibacterial rate exceeding 99.8%. The two extreme values ​​(Examples 1 and 2) and the intermediate value (Example 3) of the examples all show significantly better comprehensive performance than the comparative example, fully demonstrating the effectiveness and reliability of the method described in the present invention, providing a comprehensive performance improvement for sutures, and having significant clinical application value.

[0071] Figure 2 Scanning electron microscope (SEM) images of the composite coating of the present invention at different preparation stages and with different components are provided, which visually demonstrate the surface morphology, particle distribution, and interfacial bonding of the coating, as detailed below:

[0072] Figure 2(A) shows the morphology of the pure polydopamine (PDA) coating surface. It can be seen that PDA is deposited relatively uniformly on the suture surface in the form of dots, forming a continuous thin film. This structure provides a good foundation for the subsequent embedding of silver nanoparticles and the coating of PTFE.

[0073] Figure 2 (B) shows the surface of a PDA composite coating containing 2.0 wt% silver nanoparticles (AgNPs). (Compared to...) Figure 2 (A) In contrast, AgNPs (bright white particles) are uniformly embedded in the PDA matrix without obvious agglomeration, indicating that PDA effectively disperses and stabilizes AgNPs, and the two form a dense composite intermediate layer with antibacterial function.

[0074] Figure 2 (C) and Figure 2 (D) shows the cross-sectional structure at the interface between the PDA and the PTFE coating. Figure 2 (C) shows the interface between a pure PDA and PTFE, where a clear but tightly bonded interface exists between the two layers. Figure 2 (D) shows the interface between PDA and PTFE containing 2.0 wt% AgNPs. The presence of AgNPs further enhances the mechanical interlocking and bonding force between the PDA layer and PTFE. There is no cracking or peeling at the interface, indicating that the composite structure has good compatibility and stability.

[0075] Figure 2 (E) and Figure 2 (F) shows the surface morphology after PTFE is fully covered. Figure 2 (E) is a pure PDA surface covered with PTFE, which is a typical porous film that is continuous and intact; Figure 2 (F) shows the surface of the PDA+2.0wt%AgNPs composite coating covered by PTFE. The PTFE layer is denser and smoother, with no cracks or AgNPs exudation, indicating that the PTFE successfully encapsulates the intermediate layer, forming a lubricating surface with a low coefficient of friction.

[0076] These electron microscopy results also fully confirm that the present invention achieves uniformity, density and good interfacial bonding of the coating through the composite structure design of PDA-AgNPs intermediate layer and PTFE outer layer, giving the suture excellent lubricity, antibacterial properties and durability.

[0077] Pure PTFE, as a self-lubricating polymer, has a low coefficient of friction, but it exhibits high creep. During wear, the low shear strength between the lamellar crystals in the PTFE microstructure leads to crack propagation at internal interfaces, causing a delamination wear mechanism and resulting in poor wear performance. Furthermore, due to the chemical stability of PTFE, the adhesion strength between its film and the substrate surface is weak. Insufficient wear resistance and adhesion strength limit the application of thin PTFE films in numerous fields.

[0078] The addition of nano-silver improves the wear resistance of the PTFE coating, while the addition of polydopamine enhances the adhesion strength between PTFE and the suture substrate. Both nano-silver and polydopamine possess antibacterial properties, giving the suture an antibacterial effect. Furthermore, PTFE is a low-friction solid lubricant, reducing the drag force of the suture as it passes through tissue. Therefore, the composite coating provides the suture with both lubricating and antibacterial properties. The synergistic effect of these three elements not only improves the performance of the composite coating but also endows it with antibacterial properties.

[0079] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the above-described inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A method for preparing a composite coated suture, characterized in that, The preparation method includes the following steps: S1. Immerse the suture matrix in Tris-HCl buffer containing dopamine hydrochloride and react under shaking conditions in the dark for 1-3 hours to form a polydopamine adhesion layer; add a dispersion of silver nanoparticles modified with polyvinylpyrrolidone to the buffer reaction system to make the final mass concentration of silver nanoparticles in the reaction system 1.0-2.0 wt%, and continue shaking for 8-12 hours to allow the silver nanoparticles to embed into the polydopamine matrix through chelation, thereby obtaining a suture with a polydopamine-silver nanoparticle composite coating; S2. Immerse the suture with the polydopamine-silver nanoparticle composite coating obtained in step S1 into a polytetrafluoroethylene dispersion and sonicate it for 3-10 minutes. After removal, hang it vertically to dry for 24-48 hours in an environment of 25-30℃ and relative humidity <50%. Then heat it to 300-340℃ at a rate of 4-6℃ / min and keep it at that temperature for 0.5-2 hours to form a polydopamine-silver nanoparticle / polytetrafluoroethylene composite coated suture. Before step S1, a pretreatment step for the suture matrix is ​​also included: the suture matrix is ​​placed in anhydrous ethanol, ultrasonically cleaned at a frequency of 40-60 kHz for 5-15 minutes, and then vacuum dried at 40-60℃ for 1-2 hours. In step S1, the concentration of the Tris-HCl buffer solution is 8-12 mM, the pH value is 8.2-8.8, and the pH value is adjusted using 0.1-1 M NaOH solution; In step S1, the concentration of dopamine hydrochloride in the buffer solution is 1.5-2.5 mg / mL, and it is dissolved by magnetic stirring at 20-30°C for 10-30 minutes until completely dissolved. In step S2, the polytetrafluoroethylene dispersion is pretreated before use: first, it is ultrasonically dispersed in a water bath at 25-35℃ for 5-15 minutes, and then filtered through a 200-400 mesh sieve to remove agglomerates.

2. The method for preparing the composite coated suture according to claim 1, characterized in that, In step S1, the oscillation reaction is carried out in a constant temperature oscillator at a temperature of 35-39°C and a rotation speed of 120-180 rpm. The light-proof condition is achieved by wrapping the reaction vessel with aluminum foil.

3. The method for preparing the composite coated suture according to claim 1, characterized in that, In step S1, after the reaction is completed, the sutures with the polydopamine-silver nanoparticle composite coating are cleaned, including the following three stages: first, rinse with deionized water for 30-60 seconds, then rinse with ultrapure water under 40kHz ultrasonic conditions for 1-2 minutes, and finally rinse with anhydrous ethanol for 10-20 seconds.

4. The method for preparing the composite coated suture according to claim 1, characterized in that, In step S2, the heat treatment is carried out in a muffle furnace, with the oxygen concentration inside the furnace controlled at 18%-22%. After the heat treatment is completed, the furnace is cooled to below 50°C and the product is removed.

5. The method for preparing the composite coated suture according to claim 1, characterized in that, The process after step S2 includes a post-processing step: the obtained composite coated suture is irradiated with ultraviolet light for 15-30 minutes for surface sterilization, and then vacuum sealed.

6. A composite coated suture, characterized in that, The composite-coated suture is prepared by the preparation method according to any one of claims 1-5, and the surface of the suture has a polydopamine-silver nanoparticle / polytetrafluoroethylene composite coating, wherein the composite coating includes a polydopamine-silver nanoparticle intermediate layer bonded to the suture substrate and a polytetrafluoroethylene outer layer covering thereon.

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