A degradable zinc alloy wire for small ear deformity correction and a preparation method thereof

Abstract

This invention discloses a biodegradable zinc alloy wire for microtia correction surgery and its preparation method, belonging to the field of biomedical materials. The biodegradable zinc alloy wire for microtia correction surgery is characterized in that it is a Zn-Cu-Mn-Fe zinc alloy, with the alloy element composition by mass percentage as follows: 0 < Cu ≤ 3 wt.%, 0 < Mn ≤ 1 wt.%, 0 < Fe ≤ 1 wt.%, and the remainder being Zn. This alloy wire is prepared through processes including melting, casting, reverse extrusion, cold drawing combined with hot drawing, and heat treatment. The Zn-Cu-Mn-Fe quaternary alloy wire obtained by this invention has a tensile strength of 100–150 MPa, a yield strength of 80–120 MPa, and an elongation greater than 58%. It possesses the excellent plasticity, suitable tensile strength, and yield strength required for suture materials in microtia correction surgery. It can maintain the required mechanical properties in the early stages of implantation and gradually degrades completely under the influence of implant tissue fluid in the later stages.

Description

Technical Field

[0001] This invention belongs to the field of medical biomaterials, and specifically relates to a biodegradable zinc alloy wire for microtia correction surgery and its preparation method. Background Technology

[0002] Biomaterials are materials used to integrate with biological systems to treat or enhance tissues, organs, or functions within the body. They can be divided into two categories: bioinert and biodegradable. Biodegradable materials are those that decompose within a certain time after implantation. Biodegradable materials provide specific applications within the body and degrade within a given timeframe once their implantation purpose is achieved. Degradation is influenced by various variables, including the form, composition, and manufacturing process of the material used, as well as the implantation site. Many materials have been developed as biodegradable materials, such as metals, polymers, and ceramics. Sutures, as irreplaceable medical devices in traditional surgery, have been extensively studied. However, the metal sutures used clinically are often bioinert materials such as steel wire, titanium, or titanium alloys. These sutures remain in the body for extended periods after surgery. Removing them requires a second surgery, which can be painful. Leaving them in place can lead to movement during daily activities, and the tips may cause accidents during dislodgement, posing safety hazards. The development and use of biodegradable sutures avoids the need for secondary surgery and improves the effectiveness and safety of sutures as medical devices.

[0003] Congenital microtia is a common congenital disease, and its treatment primarily involves external ear reconstruction. Currently, the most commonly used material for the auricular framework is autologous rib cartilage. The fabrication of the auricular framework requires assembling rib cartilage strips into a multi-layered structure, with some areas requiring bending and shaping. To maintain the shape of the auricular framework, steel wire, titanium alloy sutures, or synthetic absorbable sutures are often used to splice and fix the rib cartilage strips to obtain a stable three-dimensional structure. Currently, titanium alloy is the most commonly used metal suture. Patent CN214549489U invented a titanium-nickel shape memory alloy medical suture, which solves the problem of sutures easily slipping out of the suture hole after insertion by creating different grooves and connecting blocks on the metal wire, and achieves analgesia by storing medication in the grooves. However, long-term placement of metal sutures in the body increases the risk of implant-related infections. Titanium alloy sutures can also shift during daily activities, and their tips can easily puncture the skin, leading to exposure of the titanium wire and cartilage, increasing the risk of postoperative infection. Biodegradable polymer sutures are also widely used in surgical procedures. Patent CN117684394A discloses a method for preparing antibacterial, anti-inflammatory, and high-toughness nylon sutures. It involves pretreating nylon monofibrils and then immersing them in an aldehyde-based phenylboronic acid solution and a polyphenol solution to obtain anti-inflammatory, high-toughness nylon monofibrils. These monofibrils are then woven into nylon sutures, which are then immersed in an aqueous solution containing a cationic polymer and silver ion compounds to obtain antibacterial, anti-inflammatory, and high-toughness nylon sutures. Patent CN117482275A discloses an absorbable medical polymer suture and its preparation method. In the presence of a catalyst, a PLGA-Upy polymer is obtained, which is then immersed in an extracellular matrix solution. EDC / NHS is added for crosslinking to obtain an ECM-PLGA-Upy composite material, which is then processed into absorbable sutures. Further reactions and compounding with various solutions yield sutures with excellent properties such as antibacterial activity, controllable degradation rate, good biocompatibility, and mechanical strength. However, synthetic polymers accumulate toxic residual monomers, wear debris, and acidic intermediate degradation products, which can lead to pathological bone resorption. Furthermore, if the surface of synthetic polymer materials is scratched by the suture needle during suturing, the surface complex is easily detached, leading to material failure. The potential risks of sutures tangling, slipping, and tearing tissue after wound closure remain unresolved. Poor mechanical properties also limit their further clinical application. Artificial absorbable sutures have poor stress strength, cannot continuously fix cartilage morphology, have poor stability, and the cartilage framework may gradually deform. Moreover, artificial absorbable sutures degrade slowly, producing acidic metabolites during degradation, causing cartilage resorption and surrounding inflammatory reactions. Therefore, it is necessary to develop a biodegradable suture with suitable mechanical properties to meet the requirements of microtia surgery.

[0004] Biodegradable metals exhibiting "biocorrosion" have attracted significant research interest. Compared to traditional metal implants, biodegradable metals release metal ions during degradation, promoting the repair of surrounding tissues. Compared to synthetic polymers or bioceramics, biodegradable metals possess superior mechanical properties, including Young's modulus, yield strength, tensile strength, and toughness. Currently, only magnesium, zinc, iron, and their alloys have been reported as biodegradable implant metals. Magnesium-based implants, in particular, have garnered attention due to their widely accepted biocompatibility. Magnesium alloys, with their excellent biocompatibility and biodegradability, are increasingly being studied as biodegradable suture materials. Their natural degradation products can be absorbed or excreted by the body. Magnesium ions are also essential elements in human metabolism and bone tissue, participating in various biochemical reactions and possessing multiple biomedical functions, including promoting osteoogenesis, vascularization, and antibacterial infection. Patent CN117026040A discloses a high-strength, high-toughness Mg-Zn-Zr-Ca magnesium alloy wire with a diameter of 0.6 mm, exhibiting a tensile strength of 350 MPa, a yield strength of 263 MPa, and an elongation of 30%. Patent CN116099031A discloses a 0.3 mm diameter Mg-Y-Nd-Gd-Zr biodegradable magnesium alloy wire for use as a suture material, with a tensile strength ≥340 MPa, a yield strength ≥292 MPa, and an elongation ≥20%. However, existing biodegradable magnesium alloy wires have low elongation, making them prone to breakage during suture application and knotting when used as surgical sutures. Furthermore, the healing time for microtia surgery wounds is >6 months, and the rapid degradation rate of magnesium alloys cannot provide sufficient mechanical support for this period. Iron and its alloys possess good formability and stability, along with high strength, making them ideal candidate materials for high-load tissue implants. However, the biocompatibility of iron corrosion products is controversial. The human body's tolerance limit for Fe is much lower than that for Zn and Mg (Fe is 10-17 mg / day; Zn is 100-150 mg / day; Mg is 375-500 mg / day). The standard electrode potentials for magnesium, zinc, and iron are -2.372, -0.7618, and -0.447 V, respectively. The high corrosion rate of magnesium and its alloys makes them unsuitable for the high load-bearing capacity required for tissue healing. Iron degrades too slowly, making complete degradation in vivo difficult, and degradation products may remain at the implantation site, which also does not meet the degradation time requirements for biodegradable sutures. The standard electrode potential of zinc is between that of magnesium and iron, which is more suitable and holds promise for meeting the degradation time requirements for sutures.

[0005] Zinc is an essential trace element for the human body, participating in almost all physiological metabolic processes and influencing the activity of various enzymes. Compared to magnesium, zinc and its alloys do not produce hydrogen gas during degradation, thus avoiding inflammation, tissue necrosis, and hindering bone growth and recovery. Zinc is a basic mineral required for normal bone development and bone homeostasis. Furthermore, zinc has been shown to promote bone recovery. Cu, Mn, and Fe are also essential trace elements for the human body. Cu plays an important role in maintaining normal hematopoietic function, promoting connective tissue formation, and maintaining the health of the central nervous system; Cu also has antibacterial properties. Mn promotes bone growth and development and bone synthesis. Fe participates in hemoglobin synthesis and oxygen transport. Therefore, researching the use of biodegradable zinc alloy sutures to replace traditional steel and titanium wires in external ear reconstruction surgery not only shows promising clinical application prospects but also breaks the market monopoly of foreign companies on titanium alloy sutures and synthetic absorbable sutures. On the other hand, when applied to external ear reconstruction surgery, considering the composition and performance requirements of biodegradable suture metal materials, the biodegradable zinc alloy filaments need to be designed not only to control the corrosion rate to match the needs of the wound healing cycle, but also to meet the requirements of low strength and high plasticity of the sutures in the external ear reconstruction surgery suturing process. Summary of the Invention

[0006] The purpose of this invention is to overcome the non-degradability problem of existing inert metal sutures such as steel wire, titanium, and titanium alloy wire used in clinical practice, and to overcome the shortcomings of reported biodegradable sutures, such as low biocompatibility, high strength, and low plasticity. This invention provides a biodegradable and absorbable zinc alloy suture with suitable strength and high plasticity, meeting the requirements of surgical sutures. It breaks through the technical prejudice that biodegradable zinc alloy wire is unsuitable for use as a surgical suture, and innovatively provides a biodegradable zinc alloy suture with good application prospects and antibacterial effects, along with its preparation method and application. After implantation, this suture slowly degrades and is absorbed by the body, disappearing spontaneously after the surgical wound heals. Simultaneously, its excellent antibacterial effect reduces the risk of surgical infection. The zinc alloy suture has a simple preparation process, strong suture force, suitable degradation rate, and good antibacterial effect, making it a suitable replacement for titanium and titanium alloy sutures currently used in clinical applications, achieving better clinical application results.

[0007] One objective of this invention is to provide a biodegradable zinc alloy wire for microtia correction surgery, characterized in that the biodegradable zinc alloy wire is a Zn-Cu-Mn-Fe zinc alloy, and its alloy element composition by mass percentage is: 0<Cu≤3wt.%, 0<Mn≤1wt.%, 0<Fe≤1wt.%, with the remainder being Zn.

[0008] The biodegradable zinc alloy wire has a tensile strength of 100-150 MPa, a yield strength of 80-120 MPa, and an elongation of greater than 58%, preferably greater than 70%, for example, greater than 70% and less than 99%. After immersion in simulated body fluid (SBF) solution at 37.5°C for 7 days, its corrosion rate is calculated to be >0.85 mm / y, and after immersion in SBF for 14 days, its corrosion rate is calculated to be >0.4 mm / y.

[0009] The biodegradable zinc alloy wire is Zn97.6Cu2Mn0.2Fe0.2, Zn97.4Cu2Mn0.2Fe0.4, or Zn97.4Cu2Mn0.4Fe0.2; preferably, the biodegradable zinc alloy wire is Zn97.6Cu2Mn0.2Fe0.2. Further, when prepared into a suture with a diameter of 0.2 mm, its tensile strength is 125.2 MPa and its elongation is 78.7%.

[0010] The second objective of this invention is to provide a method for preparing a biodegradable zinc alloy wire, characterized in that the biodegradable zinc alloy wire is a Zn-Cu-Mn-Fe zinc alloy, and its alloy element composition by mass percentage is: 0 < Cu ≤ 3 wt.%, 0 < Mn ≤ 1 wt.%, 0 < Fe ≤ 1 wt.%, with the remainder being Zn; the preparation method includes the following steps:

[0011] (1) Weigh high-purity raw materials of Zn, Cu, Mn and Fe, melt them under vacuum and protective atmosphere, cast them and cool them naturally to obtain zinc alloy ingots;

[0012] (2) After homogenizing the zinc alloy ingot, reverse extrusion is performed to obtain zinc alloy rods;

[0013] (3) The zinc alloy bar is subjected to room temperature cold drawing combined with online annealing hot drawing to obtain zinc alloy wire.

[0014] According to one embodiment, step (1) includes: preparing raw materials according to the composition and content of the zinc alloy, placing the raw materials in a crucible, melting and refining them fully in a vacuum induction furnace under an argon protective atmosphere, and then casting them, with the melting and casting temperature being 500-600°C.

[0015] According to one embodiment, step (2) includes: placing the ingot obtained in step (1) in a medium-temperature furnace and holding it at 200-400°C for 24-48 hours to homogenize it; then preheating both the ingot and the mold to 180-300°C and holding it for 30-60 minutes; performing reverse extrusion at a speed of 1-5 mm / s and an extrusion ratio of 50-100, preferably 70-90, to obtain zinc alloy bars with a diameter of 4-10 mm.

[0016] According to one embodiment, step (3) includes: when the diameter of the bar obtained in step (2) is greater than 1 mm, it is cold-drawn at a speed of 1-10 mm / s, preferably 1-5 mm / s, with a single-pass deformation of 8-20%; when the diameter is less than 1 mm, it is hot-drawn at a speed of 1-10 mm / s, preferably 1-5 mm / s, with a single-pass deformation of 5-15%, and a temperature of 200-300℃; preferably, the cold drawing also includes annealing at 300-330℃ for 20-40 min when the cumulative deformation is 45-100%.

[0017] According to one embodiment, the diameter of the zinc alloy wire in step (3) ranges from 0.1 to 0.6 mm, preferably from 0.2 to 0.3 mm. In another embodiment, the diameter of the zinc alloy wire ranges from 0.1 mm, 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, or 0.6 mm.

[0018] The third objective of this invention is to obtain biodegradable zinc alloy wire by the aforementioned preparation method.

[0019] The fourth objective of this invention is to provide the use of the aforementioned biodegradable zinc alloy wire in the manufacture of medical sutures; preferably, the medical sutures are used in surgeries and sutures of intradermal soft tissues in plastic surgery, urology, pediatrics, dentistry, otolaryngology, orthopedics, sports medicine, etc., especially in microtia correction surgery.

[0020] The fifth objective of this invention is to provide a finished suture, comprising a suture and a suture needle, wherein the suture is made of the aforementioned biodegradable zinc alloy wire.

[0021] Beneficial effects:

[0022] (1) This invention employs a reverse extrusion method with a large extrusion ratio to effectively improve the mechanical properties of zinc alloy wire. Compared with direct extrusion, there is no friction between the ingot and the extrusion cylinder in reverse extrusion, and the required extrusion pressure is much smaller than that in direct extrusion. Moreover, compared with direct extrusion, the extruded bar obtained by reverse extrusion can effectively refine the grains, balance the material flowability, eliminate defects such as porosity and looseness in the microstructure, and improve the mechanical properties and corrosion uniformity of the material. By using a larger extrusion ratio, the grains are refined better, internal defects are eliminated, and the degree of internal grain refinement can be controlled by adjusting the extrusion ratio to refine it to a certain size to meet the material requirements for subsequent hot and cold drawing.

[0023] (2) This invention relates to a process of cold drawing followed by hot drawing for alloy wires of different diameters. When the bar diameter is large, minor defects have a smaller impact on the drawing process, and the bar length is also short. It is difficult to directly hot draw the wire after heating it in a tube furnace. The thicker bars require a longer annealing time. By annealing to remove stress before cold drawing, the drawing time can be shortened. When the wire diameter is less than 1 mm, defects have a greater impact on the material properties. With the initial drawing, the wire length can pass through the tube furnace. Real-time annealing at a lower temperature can eliminate some internal stress, homogenize the structure, improve the wire properties, and reduce the occurrence of wire breakage during the drawing process. Hot drawing can also reduce the time for removing the material for annealing, improve the efficiency of the drawing process, and the alloy wire prepared by hot drawing has better surface quality and higher elongation, resulting in better corrosion resistance and knotting performance. The drawing process of combining cold drawing with hot drawing can effectively reduce the risk of microcracks during the drawing process and improve work efficiency.

[0024] (3) The medical zinc alloy suture prepared by this invention employs a unique composition design. Medical materials require high biocompatibility, and Cu, Mn, and Fe are all elements with high safety. Cu can enhance the plasticity and antibacterial properties of zinc alloy wire, exhibiting good biocompatibility and cell compatibility, effectively preventing sutures from being infected by bacteria during application and thus avoiding unnecessary consequences. Mn can significantly improve the plasticity of zinc alloys, and Mn can promote the proliferation, adhesion, and diffusion of osteoblasts, exhibiting good biocompatibility. The addition of Mn is expected to optimize material properties and improve the biocompatibility of Zn alloys. Fe is an essential nutrient element in the human body and a component of hemoglobin. Pure iron has been proven to have good biocompatibility, and the addition of iron can promote uniform corrosion of zinc alloys, reducing the possibility of local preferential fracture during corrosion and premature suture failure. The alloy wire prepared by this alloy composition forms CuZn4 and (Mn,Fe)Zn13 phases due to the addition of Cu, Fe and Mn elements. The CuZn4 phase is elongated and broken during the large deformation of the multi-pass drawing process and is evenly distributed along the drawing direction, which promotes uniform corrosion. The (Mn,Fe)Zn13 is a hard phase. Although it is fragmented to some extent along the drawing direction during the drawing process, it still retains a relatively large size. This phase has a large potential difference with the matrix, which promotes rapid corrosion. Moreover, this phase is widely distributed throughout the alloy wire. In summary, this alloy wire has a high corrosion rate and a relatively uniform corrosion morphology.

[0025] (4) The medical zinc alloy suture prepared by the present invention has a higher elongation rate than other existing zinc alloy wires.

[0026] The high elongation of the alloy wire is primarily attributed to the combined effect of several key factors. First, the large deformation during the drawing process optimizes the material's microstructure. This significant plastic deformation leads to a substantial reduction in grain size, resulting in a fine and uniform grain structure. This fine grain structure not only contributes to increased material strength but also, with its increased grain boundaries, inhibits crack propagation, increases crack propagation paths, and benefits the material's plasticity. Second, the combined use of cold and hot drawing processes plays a crucial role in the production of alloy wire. In cold drawing, the material is stretched at room temperature, which helps achieve higher strength and hardness. Hot drawing, conducted above the material's recrystallization temperature, helps release and reduce internal stress, preventing hardening and embrittlement. This temperature-varying process not only promotes recrystallization within the material but also contributes to finer and more uniform grains while reducing internal stress caused by work hardening. Finally, the second phase in the alloy wire is distributed in a fine and uniform manner within the matrix, avoiding stress concentration and thus maintaining the material's good plasticity and toughness.

[0027] In summary, the high elongation of this alloy wire is the result of the combined effects of grain refinement during the drawing process, stress control in the hot and cold drawing processes, and the uniform distribution of the second-phase particles.

[0028] (5) The medical zinc alloy suture prepared by this invention exhibits a more uniform corrosion rate compared to other existing zinc alloy wires. A significant drawback of existing zinc alloy wires as sutures is their slow degradation rate. Compared to Zn-Cu-Mn alloys, this study, by adding an appropriate amount of the nutrient element Fe, developed a Zn-Cu-Mn-Fe alloy wire with a more uniform corrosion morphology and a higher corrosion rate. The addition of Fe promotes the precipitation of bulk Fe-rich phases. These phases have a large potential difference with the matrix, promoting galvanic corrosion and increasing the degradation rate. Furthermore, the Fe-rich phases are widely distributed along the drawing direction, which means that galvanic corrosion occurs simultaneously throughout the entire alloy wire, thus promoting uniform corrosion. Moreover, observation of the microstructure in the extruded state reveals that the addition of Fe refines the size of the precipitated phases and promotes their uniform distribution. Attached Figure Description

[0029] Figure 1 It is a Zn-2Cu-0.2Mn-0.2Fe alloy suture.

[0030] Figure 2 The stress-strain curve of the prepared Zn-2Cu-XMn-XFe alloy suture is shown.

[0031] Figure 3 A schematic diagram showing the Zn-2Cu-0.2Mn-0.2Fe alloy suture after needle insertion.

[0032] Figure 4 The polarization curves of the prepared Zn-2Cu-0.2Mn-0.2Fe alloy suture in simulated body fluid (SBF).

[0033] Figure 5 The microstructure of the prepared Zn-2Cu-0.2Mn-0.2Fe alloy suture is shown, in which two uniform and dense precipitates are distributed in the alloy wire.

[0034] Figure 6 This is a comparison chart showing the corrosion rates of the zinc alloy wire from Example 1 and the zinc alloy wire from the comparative example after immersion in SBF solution for different times.

[0035] Figure 7 The images show the surface morphology of the zinc alloy wire from Example 1 and the zinc alloy wire from the comparative example after immersion in SBF solution for 14 days to remove corrosion products. (a) shows the surface morphology of the Zn-2Cu-0.2Mn-0.2Fe alloy wire after immersion in SBF solution for 14 days to remove corrosion products; (b) shows the surface morphology of the Zn-2Cu-0.2Mn alloy wire after immersion in SBF solution for 14 days to remove corrosion products.

[0036] Figure 8 The results of the cytotoxicity test of the Zn-2Cu-0.2Mn-0.2Fe alloy suture in Example 1 are shown.

[0037] Figure 9 This is a blood compatibility test of the Zn-2Cu-0.2Mn-0.2Fe alloy suture used in Example 1.

[0038] Figure 10 The results of the antibacterial performance test of the Zn-2Cu-0.2Mn-0.2Fe alloy suture in Example 1 are shown. Detailed Implementation

[0039] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0040] The technical solutions and problems solved by the embodiments of the present invention will be described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Several adjustments and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of patent protection of the present invention.

[0041] This invention provides a biodegradable zinc alloy wire, particularly for microtia correction surgery. The biodegradable zinc alloy wire is a Zn-Cu-Mn-Fe zinc alloy, and its alloy element composition by mass percentage is: 0 < Cu ≤ 3 wt.%, 0 < Mn ≤ 1 wt.%, 0 < Fe ≤ 1 wt.%, with the remainder being Zn.

[0042] The biodegradable zinc alloy wire has a tensile strength of 100-150 MPa, a yield strength of 80-120 MPa, and an elongation greater than 58%, preferably greater than 75%. After immersion in SBF solution at 37.5°C for 7 days, its corrosion rate is >0.85 mm / y; after immersion in SBF solution for 14 days, its corrosion rate is >0.4 mm / y. The Zn-Cu-Mn-Fe quaternary alloy wire of this invention possesses the excellent plasticity, suitable tensile strength, and yield strength required for sutures used in microtia correction surgery. It can maintain the required mechanical properties in the early stages of implantation and gradually achieves complete degradation under the action of implant tissue fluid in the later stages.

[0043] The biodegradable zinc alloy wire is Zn97.6Cu2Mn0.2Fe0.2, Zn97.4Cu2Mn0.2Fe0.4, or Zn97.4Cu2Mn0.4Fe0.2; preferably, the biodegradable zinc alloy wire is Zn97.6Cu2Mn0.2Fe0.2. Further, when prepared into a suture with a diameter of 0.2 mm, its tensile strength is 125.2 MPa and its elongation is 78.7%.

[0044] This invention provides a method for preparing a biodegradable zinc alloy wire, particularly for use in microtia correction surgery, comprising the following steps:

[0045] (1) Pure zinc ingots and master alloys are vacuum induction melted under an inert atmosphere. The master alloys are Cu-Zn master alloy, Zn-Mn master alloy, and Zn-Fe master alloy. After being fully melted, they are cast under a protective atmosphere to obtain zinc alloy ingots. The zinc alloy ingots are Zn-Cu-Mn-Fe quaternary alloys, wherein the mass percentage of each element is: Cu content is 0% to 3 wt.%, Mn content is 0% to 1 wt.%, Fe content is 0% to 1 wt.%, and the remainder is Zn.

[0046] (2) The zinc alloy ingot is subjected to homogenization annealing to ensure uniform structure and provide a guarantee for subsequent large deformation.

[0047] (3) A cylindrical billet is cut from the zinc alloy ingot and subjected to reverse extrusion processing with a large extrusion ratio to obtain a zinc alloy bar with fine and uniform grains. The diameter of the bar is 4 to 10 mm.

[0048] (4) The zinc alloy rod is drawn to obtain the biodegradable zinc alloy wire. The biodegradable zinc alloy wire has low strength, high toughness, is easy to sew and deform, and has a certain mechanical stability.

[0049] Preferably, in step (1), the smelting process is as follows: high-purity zinc and intermediate alloy ingots are added to a melting furnace, vacuumed to below 0.1 Pa, then argon gas is introduced as a protective gas, the temperature is raised to 500-650℃, held for 15-30 minutes, then cooled to 300-400℃ and held for 20 minutes before casting. The final casting rod has a diameter of 80 mm and a height of 200 mm.

[0050] Preferably, in step (2), the homogenization process is as follows: the temperature of the medium-temperature furnace is raised to 200-400℃, the casting rod from step (1) is placed in, and after holding at the temperature for 24-48 hours, the casting rod is taken out and air-cooled to room temperature.

[0051] Preferably, in step (3), the extrusion process is as follows: the casting rod is processed into a cylinder with a diameter of 35-40 mm and a height of 15-30 mm, kept at 180-300℃ for 30-60 minutes, and back-extruded at a speed of 1-5 mm / s with an extrusion ratio of 20-100 to produce a rod with a diameter of 4-10 mm.

[0052] Preferably, in step (4), the room temperature drawing process is as follows: the alloy rod obtained by reverse extrusion in step (3) is machined to make the alloy rod straight and smooth. After annealing at an annealing temperature of 200-400℃ for 30-60 minutes, it is cooled in the furnace and then cold-drawn at room temperature. The drawing speed is 1-10 m / min, preferably 1-5 mm / s, and the deformation per pass is 8%-20%. When the cumulative deformation is 45%-100%, intermediate annealing is performed at an annealing temperature of 200-400℃. This process is repeated until the diameter of the alloy rod is 1 mm. To prevent wire breakage below 1 mm in diameter, hot drawing is then performed at a drawing temperature of 200-300℃ and a drawing speed of 1-10 m / min. A deformation of 5%-15% per pass is used. The alloy wire is passed through a tubular heating furnace. The temperature inside the heating furnace is set to 200-400℃, and the temperature inside the furnace is monitored in real time by a thermocouple.

[0053] A finished suture includes a suture and a suture needle, said suture being made of the aforementioned biodegradable zinc alloy wire.

[0054] The preparation process of the finished suture is as follows: A high-strength, stainless steel suture needle is selected, with a tiny hole at the needle tail. The diameter of the hole is slightly larger than the diameter of the suture, for example, 0.3 mm, and the hole is circular. The zinc alloy suture undergoes ultraviolet sterilization to ensure sterility. A high-precision crimping device is used, equipped with a CNC system to precisely control the crimping position and force. The device includes a high-strength crimping head and a positioning device to ensure the accuracy of the crimping process. The crimping device integrates a real-time quality monitoring system, which can detect pressure, position, and time parameters during the crimping process to ensure the stability and consistency of each crimp. First, positioning is performed by inserting one end of the suture into the hole at the needle tail to a depth of 1 mm. A high-magnification magnifying glass is used to ensure the suture is horizontally aligned with the hole. Preliminary fixation is then performed to prevent movement or deviation during insertion. Next, crimping is performed. The robotic arm of the crimping device precisely positions the suture needle below the crimping head, ensuring complete alignment of the hole at the needle tail with the crimping head. Crimping parameters are set, including pressure, time, and the shape of the crimping head. The crimping connector used is cylindrical. The crimping equipment is started, and the crimping connector crimps the needle tail at the set pressure and time. The crimping connector is made of a high-hardness alloy, applying uniform pressure within a very small area to ensure plastic deformation of the suture and the metal of the needle tail, achieving a strong mechanical connection. Finally, a quality inspection is performed. The crimped area is visually inspected using a microscope to ensure a firm connection between the suture and the needle tail, without obvious damage or loosening. A tensile test is conducted, with the testing equipment applying gradually increasing tension until a tensile force of 15N is reached, ensuring the suture will not detach during surgery. Metallographic analysis is then performed on the crimped area to observe the bonding between the suture and the needle tail metal, ensuring there are no microscopic cracks or defects. The finished product is aseptically packaged in sterile paper bags to ensure no contamination during transportation and storage. The packaged suture needles undergo a secondary X-ray sterilization treatment.

[0055] The aforementioned biodegradable absorbable zinc alloy sutures are used in surgeries and intradermal soft tissue suturing, including those in plastic surgery, urology, pediatrics, dentistry, otolaryngology, orthopedics, and sports medicine, and are especially used for suturing in external ear reconstruction surgery.

[0056] Example 1: Zn-2Cu-0.2Mn-0.2Fe

[0057] (1) Weigh the required alloy composition according to the weight percentage of 2wt.% Cu, 0.2wt.% Mn, 0.2wt.% Fe, and the balance being Zn, wherein the purity of the zinc raw material is greater than or equal to 99.99%, the purity of the Cu-30Zn master alloy is greater than or equal to 99.99%, the purity of the Zn-20Mn master alloy is greater than or equal to 99.99%, and the purity of the Zn-2Fe master alloy is greater than or equal to 99.99%.

[0058] (2) After the surface of the raw material is cleaned, the high-purity metal is placed in the crucible of a vacuum melting furnace, the vacuum is drawn to 0.1 Pa, and then 10000 Pa of argon gas is introduced. The furnace is heated until the metal is completely melted, and after 20 minutes of thorough refining, it is cast into an ingot of the specified size. The melting and casting temperature is 500-600℃. After cooling, the ingot is removed from the furnace for later use. The final ingot size is 80 mm in diameter and 200 mm in height.

[0059] (3) The ingot was then placed in a medium-temperature furnace for homogenization treatment. The holding temperature was 400℃ and the holding time was 36h. After holding, it was air-cooled to room temperature.

[0060] (4) The homogenized ingot is processed into a cylindrical ingot with a diameter of 40 mm and a length of 20 mm. It is kept at 180-300℃ for 30-60 minutes and then subjected to reverse extrusion processing. The extrusion temperature is 300℃, the extrusion speed is 5 mm / s, and the extrusion ratio is 80. The bar with a diameter of 4.5 mm is extruded. After the sample surface is polished by machining, it is drawn.

[0061] (5) Anneal at 300℃ for 30 min before drawing. The drawing speed is 2 m / min and the drawing temperature is room temperature. The deformation per pass is 10%. When the cumulative deformation is about 50%, anneal at 300℃ for 30 min is performed. Repeat this process until the wire diameter is 1 mm. Pass the wire through a tube furnace. Set the furnace temperature to 300℃. After holding the wire in the furnace for 10 min, perform hot drawing at a drawing speed of 2 m / min and a deformation per pass of 10% until the wire diameter is 0.2 mm. Figure 1 This image shows a macroscopic view of a 0.2 mm diameter Zn-2Cu-0.2Mn-0.2Fe biodegradable absorbable magnesium alloy suture for biomedical use. Testing of the Zn-2Cu-0.2Mn-0.2Fe alloy obtained in the above steps revealed a room temperature tensile strength ≥100 MPa (e.g., a tensile strength of 125.2 MPa), a yield strength ≥80 MPa, and an elongation ≥75% (e.g., an elongation of 78.7%). Figure 2 As shown, the material properties meet the requirements for medical suture fabrication. Figure 3 As shown, alloy wire is sutured with needles to produce a finished suture.

[0062] Corrosion performance was tested. Figure 4 The polarization curves of the prepared Zn-2Cu-0.2Mn-0.2Fe wire in SBF simulated body fluid at 37.5℃ are shown. The corrosion potential Ecorr of the alloy wire is -1.14V, and the corrosion current Icorr is 5.15×10⁻⁶. -5The alloy wire was immersed in SBF simulated body fluid, and its corrosion rate was 0.42 mm / y, with uniform corrosion. Its microstructure is as follows: Figure 5 As shown, the left image is the microstructure under a light microscope, and the right image is the microstructure under a scanning electron microscope.

[0063] Biological assessment of Zn-2Cu-0.2Mn-0.2Fe

[0064] A. Cytotoxicity assessment

[0065] Before preparing the extract, the silk materials were ultrasonically cleaned with anhydrous ethanol, disinfected with 75% alcohol, and then washed with culture medium to remove residual ethanol. A 0.2 g / ml extract was then prepared using complete culture medium and incubated for 24 hours. Cells were then cultured at 5 × 10⁻⁶ cells / ml. 3 Cells were seeded at a density of 100 cells / well in 48-well plates and allowed to adhere for 24 hours. The culture medium was then replaced with an extract made from silk fibers (concentrations of 10%, 40%, 50%, and 100%). The control group received normal culture medium. All cells were incubated for 24 hours. Then, complete culture medium containing 10% CCK-8 solution was added to each well, and the plates were incubated for 2 hours at 37°C and 5% CO2. Finally, 100 μL of culture medium was transferred to each well in a 96-well plate, and the absorbance was measured using a microplate reader at 450 nm emission wavelength. Figure 8 As shown, the results indicate that the absorbance values ​​of different concentrations of extracts were not significantly different from those of the control group, proving that the silk material has good biocompatibility with cells.

[0066] Hemolysis test assessment

[0067] Take 500 μl of whole blood, add 5 ml of PBS solution, centrifuge at 5000 rpm for 5 min, collect the precipitate, add PBS solution to 10 ml, centrifuge at 5000 rpm for 5 min, collect the precipitate again, add PBS solution to 10 ml, centrifuge at 5000 rpm for 5 min until the supernatant is clear, then resuspend the viable cells in 10 ml of PBS solution. Positive control group: take 200 μl of red blood cell suspension + 800 μl of ddH2O; negative control group: take 200 μl of red blood cell suspension + 800 μl of PBS solution; experimental group: take 200 μl of red blood cell suspension + 800 μl of PBS extraction solutions of different concentrations (10%, 40%, 50%, 70%, 100%), incubate at 37℃ for 1 h, then centrifuge at 5000 rpm for 5 min, and observe and compare the hemolytic reaction. The observation results show ( Figure 9 The hemolysis of red blood cells treated with different concentrations of silk extract was significantly lower than that in the pure water treatment group. Even with 100% concentration extract, no obvious hemolysis was observed, proving that the silk can avoid hemolysis.

[0068] Antibacterial activity assessment

[0069] Staphylococcus aureus colonies were collected and diluted with PBS to a McFarland turbidity of 0.3. 5 ml of the bacterial suspension was then taken. For the experimental group, mycelial material was added at a ratio of 10 mg / ml to PBS. The control group received no treatment. The mixture was incubated at 37°C for 24 hours on a shaker at 125 rpm. Then, 40 μl of the bacterial suspension was spread onto an agar plate containing bacterial culture medium, and the plate was incubated at 37°C for 24 hours. The bacterial colony growth was observed. Antibacterial results showed (…). Figure 10 In the co-incubation group with the silk material, the number of bacterial colonies on the CFU-coated plate was significantly less than that in the control group, proving that the silk material of the present invention has antibacterial advantages.

[0070] Example 2: Zn-2Cu-0.2Mn-0.4Fe

[0071] (1) Weigh the required alloy composition according to the weight percentage of 2wt.% Cu, 0.2wt.% Mn, 0.4wt.% Fe, and the balance being Zn, wherein the purity of the zinc raw material is greater than or equal to 99.99%, the purity of the Cu-30Zn master alloy is greater than or equal to 99.99%, the purity of the Zn-20Mn master alloy is greater than or equal to 99.99%, and the purity of the Zn-2Fe master alloy is greater than or equal to 99.99%.

[0072] (2) After the surface of the raw material is cleaned, the high-purity metal is placed in the crucible of a vacuum melting furnace, the vacuum is drawn to 0.1 Pa, and then 10000 Pa of argon gas is introduced. The furnace is heated until the metal is completely melted, and after 20 minutes of thorough refining, it is poured into an ingot of the specified size. After cooling, the ingot is removed from the furnace for later use. The final ingot size is 80 mm in diameter and 200 mm in height.

[0073] (3) The ingot was then homogenized, and the holding temperature was 380℃ for 36 hours. After holding, it was air-cooled to room temperature.

[0074] (4) The homogenized ingot is processed into a cylindrical ingot with a diameter of 40 mm and a length of 20 mm. It is kept at 180-300℃ for 30-60 minutes and then subjected to reverse extrusion processing. The extrusion temperature is 300℃, the extrusion speed is 4 mm / s, and the extrusion ratio is 64. The bar with a diameter of 5 mm is extruded. After the sample surface is polished by machining, it is drawn.

[0075] (5) Anneal at 320℃ for 30 min before drawing. The drawing speed is 2 m / min and the drawing temperature is room temperature. When the deformation per pass is 10% and the cumulative deformation is 45%, anneal at 320℃ for 30 min is performed. This process is repeated until the wire diameter is 1 mm. Pass the wire through a tube furnace with the furnace temperature set at 320℃. After holding the wire in the furnace for 10 min, perform hot drawing at a drawing speed of 2 m / min and a deformation per pass of 10% until the wire diameter is 0.2 mm.

[0076] The Zn-2Cu-0.2Mn-0.4Fe alloy obtained through the above steps was tested, yielding a room temperature tensile strength of 133 MPa and an elongation of 58.28%. Figure 2 As shown, the alloy wire was used to add needles to the suture, and the material properties also met the requirements for medical suture preparation.

[0077] (6) The corrosion performance was tested by immersing the alloy wire in SBF simulated body fluid. The alloy wire was uniformly corroded, and the corrosion rate was 0.65 mm / y.

[0078] Example 3: Zn-2Cu-0.4Mn-0.2Fe

[0079] (1) Weigh the required alloy composition according to the weight percentage of 2wt.% Cu, 0.4wt.% Mn, 0.2wt.% Fe, and the balance being Zn, wherein the purity of the zinc raw material is greater than or equal to 99.99%, the purity of the Cu-30Zn master alloy is greater than or equal to 99.99%, the purity of the Zn-20Mn master alloy is greater than or equal to 99.99%, and the purity of the Zn-2Fe master alloy is greater than or equal to 99.99%.

[0080] (2) After the surface of the raw material is cleaned, the high-purity metal is placed in the crucible of a vacuum melting furnace, the vacuum is drawn to 0.1 Pa, and then 10000 Pa of argon gas is introduced. The furnace is heated until the metal is completely melted, and after 25 minutes of thorough refining, it is poured into an ingot of the specified size. After cooling, the ingot is removed from the furnace for later use. The final ingot size is 80 mm in diameter and 200 mm in height.

[0081] (3) The ingot was then homogenized, and the holding temperature was 400℃ for 36 hours. After holding, it was air-cooled to room temperature.

[0082] (4) The homogenized ingot is processed into a cylindrical ingot with a diameter of 40 mm and a length of 20 mm. It is kept at 180-300℃ for 30-60 minutes and then subjected to reverse extrusion processing. The extrusion temperature is 300℃, the extrusion speed is 3 mm / s, and the extrusion ratio is 64. The bar with a diameter of 5 mm is extruded. After the sample surface is polished by machining, it is drawn.

[0083] (5) Anneal at 320℃ for 30 min before drawing. The drawing speed is 2 m / min and the drawing temperature is room temperature. When the deformation per pass is 10% and the cumulative deformation is 55%, anneal at 320℃ for 30 min is performed. This process is repeated until the wire diameter is 1 mm. Pass the wire through a tube furnace. The furnace temperature is set to 320℃. After holding the wire in the furnace for 10 min, hot drawing is performed at a drawing speed of 2 m / min and a deformation per pass of 10% until the wire diameter is 0.2 mm.

[0084] The Zn-2Cu-0.2Mn-0.4Fe alloy obtained through the above steps was tested, yielding a room temperature tensile strength of 129.08 MPa and an elongation of 93.1%. Figure 2 As shown, the alloy wire was used to add needles to the suture, and the material properties met the requirements for medical suture preparation.

[0085] (6) The corrosion performance was tested by immersing the alloy wire in SBF simulated body fluid. The alloy wire was uniformly corroded, and the corrosion rate was 0.58 mm / y.

[0086] Comparative example: Zn-2Cu-0.2Mn

[0087] (1) The required alloy composition was weighed according to the weight percentage of 2wt.% Cu, 0.2wt.% Mn, and the balance being Zn. The purity of the zinc raw material was greater than or equal to 99.99%, the purity of the Cu-30Zn master alloy was greater than or equal to 99.99%, and the purity of the Zn-20Mn master alloy was greater than or equal to 99.99%.

[0088] (2) After the surface of the raw material is cleaned, the high-purity metal is placed in the crucible of a vacuum melting furnace, the vacuum is drawn to 0.1 Pa, and then 10000 Pa of argon gas is introduced. The furnace is heated until the metal is completely melted, and after 20 minutes of thorough refining, it is poured into an ingot of the specified size. After cooling, the ingot is removed from the furnace for later use. The final ingot size is 80 mm in diameter and 200 mm in height.

[0089] (3) The ingot was then homogenized, and the holding temperature was 400℃ for 36 hours. After holding, it was air-cooled to room temperature.

[0090] (4) The homogenized ingot is processed into a cylindrical ingot with a diameter of 40 mm and a length of 20 mm. It is kept at 180-300℃ for 30-60 minutes and then subjected to reverse extrusion processing. The extrusion temperature is 300℃, the extrusion speed is 5 mm / s, and the extrusion ratio is 80. The bar with a diameter of 4.5 mm is extruded. After the sample surface is polished by machining, it is drawn.

[0091] (5) Anneal at 320℃ for 30 min before drawing. The drawing speed is 2 m / min and the drawing temperature is room temperature. The deformation per pass is 10%. When the cumulative deformation is about 50%, anneal at 300℃ for 30 min is performed. Repeat this process until the wire diameter is 1 mm. Pass the wire through a tube furnace. Set the furnace temperature to 300℃. After holding the wire in the furnace for 10 min, perform hot drawing at 2 m / min and 10% deformation per pass until the wire diameter is 0.2 mm.

[0092] The Zn-2Cu-0.2Mn alloy obtained through the above steps was tested and found to have a room temperature tensile strength of 190.27 MPa and an elongation of 87.15%. Figure 2 As shown.

[0093] (6) The corrosion performance was tested. The alloy wire was immersed in SBF simulated body fluid. The corrosion of the alloy wire was uneven, and the corrosion rate was 0.29 mm / y.

[0094] Comparison of corrosion rate and uniform corrosion degree

[0095] Corrosion rate tests were performed on the comparative examples and the embodiments, such as... Figure 6 The figure shows a comparison of the corrosion rates of Example 1 and the comparative example. The comparison shows that the zinc alloy suture prepared in the embodiment of the present invention has a faster corrosion rate. Figure 7 The images show the surface morphology of Example 1 and the comparative example after immersion in SBF solution for 14 days to remove corrosion products. Observation of the degradation morphology of the examples and the comparative example shows that the corrosion morphology of the example is more uniform, and the corrosion degree is more severe, better meeting the requirements of microtia surgery sutures for a faster corrosion rate and uniform corrosion degree. Simultaneously, biological evaluation indicates that it has good cell safety and anti-hemolytic reaction, and also has antibacterial advantages.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of patent protection of the present invention.

Claims

1. A biodegradable zinc alloy wire for microtia correction surgery, characterized in that, The biodegradable zinc alloy wire is a Zn-Cu-Mn-Fe zinc alloy, and its alloy element composition by mass percentage is: 0 < Cu ≤ 3 wt.%, 0 < Mn ≤ 1 wt.%, 0 < Fe ≤ 1 wt.%, with the remainder being Zn. The biodegradable zinc alloy wire has a tensile strength of 100–150 MPa, a yield strength of 80–120 MPa, and an elongation greater than 58%. After immersion in SBF solution at 37.5℃ for 7 days, its corrosion rate is >0.85 mm / y, and after immersion in SBF solution for 14 days, its corrosion rate is >0.4 mm / y.

2. The biodegradable zinc alloy wire according to claim 1, characterized in that, The elongation of the biodegradable zinc alloy wire is greater than 70%.

3. The biodegradable zinc alloy wire according to claim 1, characterized in that, The biodegradable zinc alloy wire is Zn97.6Cu2Mn0.2Fe0.2 or Zn97.4Cu2Mn0.2Fe0.4 or Zn97.4Cu2Mn0.4Fe0.

2.

4. The biodegradable zinc alloy wire according to claim 1, characterized in that, The biodegradable zinc alloy wire is Zn97.6Cu2Mn0.2Fe0.

2. When it is made into a suture with a diameter of 0.2 mm, its tensile strength is 125.2 MPa and its elongation is 78.7%.

5. The method for preparing the biodegradable zinc alloy wire according to claim 1 or 2, characterized in that, The biodegradable zinc alloy wire is a Zn-Cu-Mn-Fe zinc alloy, and its alloy element composition by mass percentage is: 0 < Cu ≤ 3 wt.%, 0 < Mn ≤ 1 wt.%, 0 < Fe ≤ 1 wt.%, with the remainder being Zn; the preparation method includes the following steps: (1) Weigh high-purity raw materials of Zn, Cu, Mn and Fe, melt them under vacuum and protective atmosphere, cast them and cool them naturally to obtain zinc alloy ingots; (2) After homogenizing the zinc alloy ingot, it is back-extruded to obtain zinc alloy rods; (3) The zinc alloy bar is subjected to room temperature cold drawing combined with online annealing hot drawing to obtain zinc alloy wire.

6. The method for preparing the biodegradable zinc alloy wire according to claim 5, characterized in that, The step (1) includes: preparing raw materials according to the composition and content of zinc alloy, placing the raw materials in a crucible, melting and refining them fully in a vacuum induction furnace under an argon protective atmosphere, and then casting them. The melting and casting temperature is 500-600℃. Step (2) includes: placing the ingot obtained in step (1) in a medium-temperature furnace and holding it at 200-400℃ for 24-48 hours to homogenize it; then preheating both the ingot and the mold to 180-300℃ and holding it for 30-60 minutes; performing reverse extrusion at a speed of 1-5 mm / s and an extrusion ratio of 50-100 to obtain zinc alloy bars with a diameter of 4-10 mm. Step (3) includes: when the diameter of the bar obtained in step (2) is greater than 1 mm, it is cold drawn at 1-10 mm / s with a single-pass deformation of 8-20%; when the diameter is less than 1 mm, it is hot drawn at 1-10 mm / s with a single-pass deformation of 5-15% and a temperature of 200-300℃; cold drawing also includes annealing at 300~330℃ for 20-40 min when the cumulative deformation is 45-100%.

7. The method for preparing the biodegradable zinc alloy wire according to claim 6, characterized in that, The extrusion ratio in step (2) is 70-90.

8. The method for preparing the biodegradable zinc alloy wire according to claim 5, characterized in that, The diameter of the zinc alloy wire in step (3) is in the range of 0.1-0.6 mm.

9. The method for preparing the biodegradable zinc alloy wire according to claim 5, characterized in that, The diameter of the zinc alloy wire in step (3) is in the range of 0.2-0.3 mm.

10. Use of the biodegradable zinc alloy wire according to any one of claims 1 to 4 in the manufacture of medical sutures.

11. The use according to claim 10, characterized in that, The medical sutures are used in surgeries and intradermal soft tissue suturing in plastic surgery, urology, pediatrics, dentistry, otolaryngology, orthopedics, and sports medicine.

12. The use according to claim 10, characterized in that, The medical sutures are used in microtia correction surgery.

13. A finished suture, comprising a suture and a suture needle, said suture being made of the biodegradable zinc alloy wire as described in any one of claims 1 to 4.

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