Magnesium alloy porous anorectal drainage tube and preparation method thereof

Abstract

The invention discloses a magnesium alloy porous anorectal drainage tube and a preparation method thereof. The chemical expression general formula of the magnesium alloy porous anorectal drainage tube is Mg-xLi-yM, wherein M represents one of Ca, Zn, Ti and Sr; x and y represent the mass fractions of Li and M: x is more than or equal to 4 and less than or equal to 20, and y is more than or equal to 1 and less than or equal to 10; according to the drainage tube, a magnesium alloy cast ingot is prepared through vacuum electric arc melting, then a bar with the diameter of 2-10 mm is obtained through hot extrusion, a wire with the diameter of 0.2-1 mm is prepared through multi-pass drawing annealing, then the wire is woven into a perforated tube, and finally the drainage tube is obtained through laser treatment forming. According to the magnesium alloy porous anorectal drainage tube, through the gradient tissue design of different tissue structures of the surface layer and the inner layer, the effects that the outer layer is degraded preferentially to release a healing space and the inner layer is degraded slowly to maintain supporting are achieved, and degradation products can promote wound healing and inhibit inflammatory response.

Description

Technical Field

[0001] This invention belongs to the field of medical material preparation and relates to a magnesium alloy porous anorectal drainage tube and its preparation method. Background Technology

[0002] With the increasing prevalence of anorectal surgeries (such as hemorrhoidectomy, anal fistula repair, and radical resection of rectal cancer), postoperative drainage has become a crucial step in preventing infection and promoting wound healing. The unique anatomical features of the anorectal region make it highly susceptible to postoperative problems such as fluid accumulation, infection, and delayed healing, thus naturally necessitating drainage intervention. The anorectal region contains multiple loose connective tissue spaces, and postoperative wounds are often lacunar or complex wounds (such as the fistula tract of anal fistula or the abscess cavity of perianal abscess). Blood, pus, and exudate are difficult to drain naturally by gravity and tend to accumulate in the cavities, leading to infection. At the same time, the surgical site is close to the anus, and feces and bacteria can easily contaminate the wound during defecation. If the accumulated fluid and pus cannot be drained in time, bacteria will multiply in large numbers, directly causing wound infection, suppuration, and even the spread of inflammation. In addition, the blood supply to the distal anorectal region comes from the inferior rectal artery, where blood flow is slow and nutrient supply is relatively insufficient. If the wound is soaked in fluid or stimulated by infection for a long time, it can cause edema and necrosis of granulation tissue, significantly prolonging the healing period. In severe cases, it may also lead to intractable complications such as chronic ulcers and anastomotic leakage.

[0003] Traditional rectal drainage tubes are mostly made of inert materials such as silicone, polyvinyl chloride (PVC), or rubber. While they offer some drainage, they have several drawbacks. These materials are typically non-degradable, requiring secondary surgery or instrument removal, increasing patient suffering and medical costs. Furthermore, the limited biocompatibility of inert materials like silicone, PVC, or rubber can easily lead to local inflammation or tissue adhesions with prolonged placement. In recent years, biodegradable medical materials (such as polylactic-co-glycolic acid copolymer, PLGA) have been increasingly used in drainage tube fabrication, but their insufficient mechanical strength and excessively acidic degradation products limit their clinical application. Currently, commercially available metal drainage tubes are mainly divided into two categories: non-degradable stainless steel / titanium alloy drainage tubes and biodegradable magnesium alloy urethral / vascular stents. Non-degradable metal drainage tubes have excessive support and are non-degradable. After implantation in the anorectal region, they are prone to compressing the mucosa and causing necrosis. They also require a second surgery to remove them, resulting in a high risk of complications. Degradable magnesium alloy stents are designed for the urethral / vascular environment. In the variable environment of the anorectal region (pH=6.0-9.0), the degradation rate becomes uncontrolled, the support is lost prematurely, and the structure has no drainage or anti-blockage function, which cannot meet the needs of anorectal surgery.

[0004] Existing techniques for draining anorectal abscesses also have significant shortcomings. Application No. 202220214701.5 discloses a drainage tube for treating perianal abscesses. While this tube conforms to anatomical structures and can accommodate multiple abscess cavities, it only has a single drainage function, is not biodegradable, requires secondary surgery for removal, and is difficult to promote wound healing or reduce complications. Chinese invention patent application No. 201410331301.2 discloses a multifunctional anorectal drainage tube. Although this multifunctional anorectal drainage tube has structures such as an anti-dislodgement elastic balloon, its sealing effect is poor. The literature "Annals of Medicine and Surgery" 11(2016) 42e46 discloses a study evaluating corrugated rubber drainage after perianal abscess surgery. Although the corrugated rubber drainage tube used in this literature can achieve drainage through pressure difference and gravity, its rubber material can trigger a strong tissue reaction, prolonging the healing time of the drainage path. Furthermore, the open drainage opening can easily become an entry point for pathogens, and improper care can easily induce perianal abscesses, cellulitis, and other problems. The aforementioned products and related technologies are unsuitable for rectal drainage scenarios because their materials, structures, and performance are incompatible with the core requirements of the anorectal environment. Magnesium alloys, as an emerging biodegradable biomaterial, possess excellent biocompatibility and degradability. However, the rapid degradation of conventional magnesium alloys in the anorectal environment (affected by intestinal fluid) and their insufficient surface bioactivity still limit their application in anorectal drainage tubes. Therefore, this invention aims to prepare a porous magnesium alloy anorectal drainage tube by optimizing the alloy composition and product structure, significantly improving its corrosion resistance and bioactivity, ensuring stable and controllable degradation of the drainage tube during the effective drainage period, while promoting wound healing and reducing the occurrence of complications. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention aims to provide a magnesium alloy porous anorectal drainage tube and its preparation method. Its chemical formula is: Mg-xLi-yM; where M represents one of Ca, Zn, Ti, and Sr; x and y represent the mass fractions of Li and M: 4≤x≤20, 1≤y≤10, with the balance being Mg. The drainage tube is prepared by vacuum arc melting to obtain a magnesium alloy ingot, followed by hot extrusion to obtain rods with a diameter of 2–10 mm. These rods are then drawn and annealed through multiple passes to produce 0.2–1 mm wire, which is then woven into a porous tube and finally laser-treated to form the final product. This magnesium alloy porous anorectal drainage tube, through a gradient tissue design with different structures in the outer and inner layers, achieves the effect of preferential degradation of the outer layer to release healing space, while the inner layer slowly degrades to maintain support. Its degradation products can promote wound healing and inhibit inflammatory responses.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A porous magnesium alloy anorectal drainage tube has the following chemical composition: Mg-xLi-yM; where M represents one of Ca, Zn, Ti, and Sr; x and y represent the mass fractions of Li and M: 4≤x≤20, 1≤y≤10, and the balance is Mg; the porous magnesium alloy anorectal drainage tube has a double-layer structure, with an outer layer having a coarse-grained structure and an inner layer having a fine-grained structure, and the ratio of coarse to fine grains being 1:1, 3:2, or 3:7; the diameter of the porous magnesium alloy anorectal drainage tube is 0.5~2.0 cm, the length is 8~15 cm, and the mesh diameter is 100~300 μm.

[0007] This invention also provides a method for preparing a magnesium alloy porous anorectal drainage tube, which is carried out in the following order: S1. Weigh different masses of raw materials according to the proportion, place pure magnesium in a vacuum electric arc melting furnace, ignite the electric arc under a vacuum or high-purity argon protective atmosphere, so that pure magnesium melts to form a stable molten pool, and then add Li and M in batches and use electric arc stirring to achieve composition homogenization, and obtain magnesium alloy ingots. S2. The magnesium alloy ingot is machined to remove the oxide scale on the surface and at both ends, and then hot extruded to obtain magnesium alloy rods with a diameter of 2 to 10 mm. S3. Perform multiple cold drawing processes on magnesium alloy bars, and perform annealing treatment between each adjacent processing pass to obtain magnesium alloy wire with a diameter of 0.2 to 1 mm. S4. The magnesium alloy wire is woven into a dense porous tube, and then annealed and shaped under vacuum or high-purity argon to obtain a magnesium alloy porous tube. S5. Fix the magnesium alloy porous tube on the platform and perform laser treatment, making the laser beam scan in a straight line along the axial direction of the wire, repeating multiple times to obtain the magnesium alloy porous drainage tube.

[0008] As a limitation of the preparation method of the present invention, in step S1, the vacuum degree during vacuum arc melting is 10. - 3 Pa or 10 -4 Pa, voltage 25-35 V, current 100-200 A, arc heating time 3-10 min.

[0009] As another limitation of the preparation method of the present invention, in step S2, the temperature of the hot extrusion is 200~500 ℃ and the speed is 0.2~1 mm / min.

[0010] As a third limitation of the preparation method of the present invention, in step S3, the deformation amount per pass during the multi-pass cold drawing is 5~20%.

[0011] As a fourth limitation of the preparation method of the present invention, in step S3, the annealing temperature is 200~500 ℃ and the time is 5~20 min.

[0012] As a fifth limitation of the preparation method of the present invention, in step S4, the annealing and shaping temperature is 200~400℃ and the time is 10~60 min.

[0013] As a sixth limitation of the preparation method of the present invention, in step S5, during the laser treatment, the diameter of the laser spot is 0.2~0.8 mm, and the surface temperature of the magnesium alloy porous tube is 300~500℃.

[0014] In this invention, the surface temperature of the alloy during laser treatment affects the grain size and crystal orientation. When the temperature is less than 300°C, an effective gradient structure cannot be formed in the wire, causing the product performance to revert to a homogeneous fine-grained state, thus failing to achieve the design goal of controllable degradation of the outer coarse grains in this invention. When the temperature is greater than 500°C, abnormal grain growth occurs, with some forming coarse equiaxed crystals, leading to deterioration of mechanical properties and uneven pitting, making the degradation behavior of the product completely uncontrollable.

[0015] As a seventh limitation of the preparation method of the present invention, in step S5, the scanning speed of the laser beam when scanning linearly along the axial direction of the wire is 100~300 mm / s, and after a single axial scan, the wire is rotated 90°. ° The scanning process is repeated 4 to 10 times in total.

[0016] The magnesium alloy porous anorectal drainage tube prepared by this invention exhibits a dense porous structure. The outer layer of the drainage tube has coarser grains, making it easily corroded and degraded, which can assist wound healing by slowing down the degradation rate of the healing microenvironment. Simultaneously, the inner layer of the drainage tube has finer grains, resulting in a slower degradation rate and providing stable support and drainage. The woven porous structure allows inflammatory fluid, pus, anorectal wound exudate, and small amounts of blood to flow naturally along the woven lines of the drainage tube, and due to surface tension, it does not seep into the wound through the surface micropores.

[0017] The synergistic effect of magnesium and methyl methacrylate (M) elements enhances the corrosion resistance of the alloy. The anorectal environment is complex and variable, with significant pH fluctuations (pH=6.0-9.0). Current magnesium alloy products can only provide single-mode protection against acidic or alkaline environments. The porous magnesium alloy anorectal drainage tube prepared in this invention, after implantation into the anorectal environment, undergoes a weak anodic oxidation reaction in its inner fine-grained portion. In addition to generating MgO, an amorphous film containing Mg and M is deposited in situ. In the initial implantation stage, the amorphous film slowly forms in the inner layer of the drainage tube, blocking the diffusion channels of corrosive media and greatly inhibiting the transport of substances in the corrosion reaction, thereby improving the corrosion resistance of the drainage tube. As time progresses, the M element is gradually consumed, the formation rate of the amorphous film slows down, and fine pores begin to appear on the film surface. The drainage tube then gradually degrades until it is completely degraded. Therefore, this invention can effectively control the service life of the porous magnesium alloy anorectal drainage tube, solving the problem of premature collapse and failure.

[0018] In magnesium alloy porous rectal drainage tubes, Mg and M are essential trace elements for the human body. 2+ With M n+ After compounding, it achieves a targeted and synergistic promotion of anorectal healing through three core mechanisms: cross-regulation of signaling pathways, optimization of the cellular microenvironment, and synergistic interaction between materials and cells. Mg 2+ As an activator of DNA / RNA synthetases and protein kinases, it can upregulate the expression of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), induce endothelial cell migration and tubular structure formation, and accelerate angiogenesis into the wound (especially suitable for deep anorectal wounds and ischemic wounds); Meanwhile, Mg... 2+ It can regulate vascular smooth muscle tension, improve local blood circulation, deliver sufficient oxygen and nutrients to the wound, and effectively prevent ischemic healing delay. n+ It can reduce reactive oxygen species (ROS) levels, alleviate oxidative stress damage to repair cells, and create a stable microenvironment conducive to healing. The combined effect of these two factors can promote the proliferation and differentiation of anorectal cells, helping to shorten the wound healing cycle. Furthermore, M... n+ With Mg 2+ In combination, it can cover the entire chain of anorectal repair (proliferation → migration → angiogenesis → tissue repair), promote the synthesis of core extracellular matrix (ECM) components such as type I / III collagen and fibronectin (FN) by fibroblasts; at the same time, it regulates the balance between matrix metalloproteinases (MMPs) and tissue inhibitors (TIMPs), avoids excessive degradation of ECM, enhances the mechanical strength and barrier function of granulation tissue, and provides solid structural support for mucosal repair.

[0019] Mg 2+ With M n+ In the middle, Mg 2+As a core regulatory factor, it inhibits macrophage polarization towards the pro-inflammatory M1 type and reduces the secretion of pro-inflammatory factors such as TNF-α and IL-6; while M n+ This further amplifies the effect, M n+ It can induce macrophages to transform into the anti-inflammatory M2 type, secreting anti-inflammatory factors such as IL-10 and TGF-β, and blocking the cascade amplification of inflammatory signals by inhibiting the NF-κB pathway. Together, they inhibit the proliferation of anaerobic bacteria / Escherichia coli on the surface of the magnesium alloy porous anorectal drainage tube, reducing the risk of inflammation and infection.

[0020] The above-mentioned technical solution of the present invention is a whole in which each step is closely related and mutually influential, and together they determine the morphological characteristics and performance of the product.

[0021] The above technical solution has the following advantages or beneficial effects: 1. The magnesium alloy porous anorectal drainage tube prepared by the present invention solves the core contradiction of medical magnesium alloy instruments that the outer layer needs to degrade early to release space and the inner layer needs to degrade slowly to maintain the structure through a gradient tissue design with different tissue structures in the outer and inner layers. 2. The magnesium alloy porous anorectal drainage tube prepared by this invention allows for controlled degradation rate during the healing process, and the ions generated during degradation are beneficial for wound healing; moreover, it has good biocompatibility, and the Mg produced during the degradation of the drainage tube... 2+ It can prevent inflammation from occurring; 3. The magnesium alloy porous anorectal drainage tube prepared by this invention can be degraded in the body, eliminating the need for a second surgery after the operation, thus reducing patient suffering and medical costs. 4. The preparation method of this invention is simple, the process is easy to control, and it is suitable for large-scale industrial production.

[0022] This invention is applicable to the preparation of magnesium alloy porous anorectal drainage tubes. The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0023] Figure 1 The images show the metallographic morphology and grain size statistics of the magnesium alloy porous anorectal drainage tubes prepared in Examples 1-3 of this invention, wherein: a and d are the metallographic morphology and grain size statistics of Example 1, b and e are the metallographic morphology and grain size statistics of Example 2, and c and f are the metallographic morphology and grain size statistics of Example 3. Figure 2 The X-ray diffraction patterns of the inner and outer layers of the magnesium alloy porous anorectal drainage tube prepared in Example 1 of this invention are shown below. Figure 3The graph shows a comparison of the degradation rates of the anorectal drainage tubes prepared in Examples 1, 1, 3 and 6-8 of the present invention in simulated intestinal fluid (SIF) with different pH levels, where: a is an alkaline environment with pH=9 and b is an acidic environment with pH=6. Figure 4 The X-ray diffraction patterns of the anorectal drainage tubes prepared in Comparative Examples 7 and 8 of the present invention after being immersed in simulated intestinal fluid (SIF) for 24 h are shown, where: a is Comparative Example 7 and b is Comparative Example 8. Figure 5 The bending fatigue curves of the anorectal drainage tubes prepared in Embodiment 1 and Comparative Examples 3-5 of the present invention are shown. Figure 6 The images show the proliferation morphology of human anorectal mucosal fibroblasts on the surface of the anorectal drainage tubes prepared in Embodiment 2, Comparative Examples 1-2 and Comparative Example 6 of the present invention, where: a is Comparative Example 6, b is Comparative Example 1, c is Comparative Example 2 and d is Embodiment 2. Figure 7 This is a statistical graph showing the proliferation rate of human anorectal mucosal fibroblasts on the extract of the anorectal drainage tubes prepared in Example 2 and Comparative Examples 1-3 of the present invention. Figure 8 The diagram shows the antibacterial effect of the anorectal drainage tubes prepared in Examples 1-3 and Comparative Examples 1-2 of the present invention on Escherichia coli. Figure 9 The images show the metallographic structures of the anorectal drainage tubes prepared in Comparative Examples 9, 10 and 11 of this invention, where: a is Comparative Example 9, b is Comparative Example 10 and c is Comparative Example 11. Detailed Implementation

[0024] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0026] Example 1 This embodiment prepares a magnesium alloy porous anorectal drainage tube with the chemical formula: Mg-10Ca-4Li (by mass percentage: Mg: 86 wt.%, Ca: 10 wt.%, Li: 4 wt.%). The preparation process and steps are as follows: S1. Weigh 86 g of Mg, 4 g of Li, and 10 g of Ca. Place the Mg in a vacuum arc melting furnace and set the vacuum level to 10. - 3 Pa, then ignited the electric arc, set the voltage to 25 V and the current to 200 A, so that pure magnesium melts to form a stable molten pool, then Li and Ca are added in batches and heated with electric arc stirring for 10 min to achieve composition homogenization, and magnesium alloy ingot is obtained. S2. The magnesium alloy ingot is machined to remove the oxide scale on the surface and at both ends, and then hot-extruded at 200 °C at a speed of 0.2 mm / min until the diameter of the magnesium alloy rod is 2 mm. S3. The magnesium alloy bar is cold-drawn in multiple passes with a deformation of 5% per pass. Annealing is performed between each adjacent processing pass at a temperature of 400℃ for 10 minutes to obtain a magnesium alloy wire with a diameter of 0.2 mm. S4. The magnesium alloy wire is woven into a dense porous tube with a diameter of 0.8 cm, a length of 15 cm, and a mesh diameter of 300 μm. Then, it is annealed and shaped at 200 °C for 30 min under high-purity argon to obtain the magnesium alloy porous tube. S5. Fix the magnesium alloy porous tube on the platform for laser selective annealing. Set the laser spot diameter to 0.2 mm and the surface temperature of the magnesium alloy porous tube to 500 ℃. The laser beam performs a linear scan along the wire axis at a speed of 300 mm / s. After a single axial scan, rotate the wire 90 degrees. ° The scanning process was repeated four times to obtain a Mg-10Ca-4Li magnesium alloy porous anorectal drainage tube.

[0027] Example 2 This embodiment prepares a magnesium alloy porous anorectal drainage tube with the chemical formula: Mg-8Li-1Zn (by mass percentage: Mg: 91 wt.%, Li: 8 wt.%, Zn: 1 wt.%). The preparation process and steps are as follows: S1. Weigh 91 g of Mg, 8 g of Li, and 1 g of Zn. Place the Mg in a vacuum arc melting furnace and set the vacuum level to 10. -3 Pa, then ignited the electric arc, set the voltage to 30 V and the current to 150 A, so that pure magnesium melts to form a stable molten pool, then Li and Zn are added in batches and heated with electric arc stirring for 6 min to achieve composition homogenization, and magnesium alloy ingot is obtained. S2. The magnesium alloy ingot is machined to remove the oxide scale on the surface and at both ends, and then hot-extruded at 400 ℃ at a speed of 0.5 mm / min until the diameter of the magnesium alloy rod is 10 mm. S3. The magnesium alloy bar is cold-drawn in multiple passes with a deformation of 15% per pass. Annealing is performed between each adjacent processing pass at a temperature of 200℃ for 20 minutes to obtain a magnesium alloy wire with a diameter of 0.5 mm. S4. The magnesium alloy wire is woven into a dense porous tube with a diameter of 0.5 cm, a length of 8 cm, and a mesh diameter of 100 μm. Then, it is annealed and shaped at 250 ℃ for 60 min under high-purity argon to obtain the magnesium alloy porous tube. S5. Fix the magnesium alloy porous tube on the platform for laser selective annealing. Set the laser spot diameter to 0.8 mm and the surface temperature of the magnesium alloy porous tube to 300 ℃. The laser beam performs a linear scan along the wire axis at a speed of 100 mm / s. After a single axial scan, rotate the wire 90 degrees. ° The scanning process was repeated 10 times to obtain a Mg-8Li-1Zn magnesium alloy porous anorectal drainage tube.

[0028] Example 3 This embodiment prepares a magnesium alloy porous anorectal drainage tube with the chemical formula: Mg-20Li-5Sr (by mass percentage: Mg: 75 wt.%, Li: 20 wt.%, Sr: 5 wt.%). The preparation process and steps are as follows: S1. Weigh 75 g of Mg, 20 g of Li, and 5 g of Sr. Place the Mg in a vacuum arc melting furnace and set the vacuum level to 10. - 4 Pa, then ignited the electric arc, set the voltage to 35 V and the current to 100 A, so that pure magnesium melts to form a stable molten pool, then Li and Sr are added in batches and heated with electric arc stirring for 3 min to achieve composition homogenization, and magnesium alloy ingot is obtained. S2. The magnesium alloy ingot is machined to remove the oxide scale on the surface and at both ends, and then hot-extruded at 500 ℃ at a speed of 1 mm / min until the diameter of the magnesium alloy rod is 5 mm. S3. The magnesium alloy bar is cold-drawn in multiple passes with a deformation of 20% per pass. Annealing is performed between each adjacent processing pass at 500°C for 5 minutes to obtain a magnesium alloy wire with a diameter of 1 mm. S4. The magnesium alloy wire is woven into a dense porous tube with a diameter of 2 cm, a length of 10 cm, and a mesh diameter of 250 μm. Then, it is annealed and shaped at 400 °C for 10 min under high-purity argon to obtain the magnesium alloy porous tube. S5. Fix the magnesium alloy porous tube on the platform for laser selective annealing. Set the laser spot diameter to 0.5 mm and the surface temperature of the magnesium alloy porous tube to 400 ℃. The laser beam performs a linear scan along the wire axis at a speed of 200 mm / s. After a single axial scan, rotate the wire 90 degrees. ° The scanning process was repeated 7 times to obtain a Mg-20Li-5Sr magnesium alloy porous anorectal drainage tube.

[0029] Comparative Example To investigate the effects of different parameters or alloying elements on the performance of the product during the preparation process of this invention, the following comparative experiments were conducted. Different anorectal drainage tubes were prepared according to the following comparative examples: Comparative Example 1 This comparative example prepares an anorectal drainage tube. The preparation process is similar to that of Example 2, except that Zn is not added in step S1, resulting in a Mg-8Li anorectal drainage tube.

[0030] Comparative Example 2 This comparative example prepares an anorectal drainage tube. The preparation process is similar to that of Example 2, except that Mg is not added in step S1, resulting in a Zn-8Li anorectal drainage tube.

[0031] Comparative Example 3 This comparative example prepares an anorectal drainage tube. The preparation process is similar to that of Example 2, except that in step S1, Li is not added, resulting in a Mg-1Zn anorectal drainage tube.

[0032] Comparative Example 4 This comparative example prepares an anorectal drainage tube. The preparation process is similar to that of Example 1, except that in step S4, the mesh diameter is 50 μm.

[0033] Comparative Example 5 This comparative example prepares an anorectal drainage tube. The preparation process is similar to that of Example 1, except that in step S4, the diameter of the woven mesh is 400 μm.

[0034] Comparative Example 6 This comparative example uses a commonly used medical rubber drainage tube as the drainage tube.

[0035] Comparative Example 7 This comparative example prepares an anorectal drainage tube. The preparation process is similar to that of Example 2, except that step S5 is not performed and laser selective annealing is not performed, resulting in a magnesium alloy anorectal drainage tube with fine grains.

[0036] Comparative Example 8 This comparative example prepares an anorectal drainage tube. The preparation process is similar to that of Example 2, except that instead of laser selective annealing, a muffle furnace calcination annealing process is used to obtain a magnesium alloy anorectal drainage tube with coarse grains.

[0037] Comparative Example 9 This comparative example prepares an anorectal drainage tube. The preparation process is similar to that of Example 2, except that step S3 is not performed, that is, the magnesium alloy ingot is directly extruded into magnesium alloy wire with a diameter of 0.5 mm by hot extrusion, and then further processed.

[0038] Comparative Example 10 This comparative example prepares an anorectal drainage tube. The preparation process is similar to that of Example 2, except that in step S5, the alloy surface temperature is 200°C during laser selective annealing.

[0039] Comparative Example 11 This comparative example prepares an anorectal drainage tube. The preparation process is similar to that of Example 2, except that in step S5, the alloy surface temperature is 600°C during laser selective annealing.

[0040] Performance testing The anorectal drainage tubes prepared in Examples 1-3 and Comparative Examples 1-11 of this invention were subjected to a series of structural and performance tests. The test methods for the relevant performance tests are as follows: 1. Preparation of extract: According to the standard "Biological evaluation of medical devices - Part 1: Evaluation and testing in the risk management process" (GB / T16886.1-2022 / ISO 10993-1) implemented on May 1, 2023, the sample was placed in a 6-well plate and soaked in 2 mL of serum-free culture medium for 72 h. The extract was then collected to treat the cells. 2. Co-culture method: (1) Place each group of samples under a UV lamp and expose both sides for 30 min to kill bacteria on the sample surface. After exposure, place the samples in a 24-well plate with 5 parallel samples per group. (2) Add a fibroblast suspension with a density of 5×105 cell / L and a volume of 1 mL to each well and let it stand for 5 min; then place it in a constant temperature incubator at 37 ℃ (the proportion of CO2 in the incubator is 5%) for 24 h. (3) After 24 h, discard the cell culture medium in the well plate, add 600 μL of serum-free 1640 medium containing 10% (v / v) CCK8 to any 3 wells, and incubate in a constant temperature incubator for 4 h; after 4 h, take 100 μL of the liquid and place it under a microplate reader at a wavelength of 450 nm to measure the absorbance of each group, and calculate the relative growth rate (RGR) of cells: Among them, OD 实 The absorbance of the experimental group; OD 对 The absorbance is for the control group (cells and culture medium only). 3. Immunofluorescence staining assay: Human anorectal fibroblasts (HCF) were induced to differentiate in vitro for 6 days in 6-well plates. The immunofluorescence staining was performed according to the traditional method. Pcna was used for staining in this experiment. After setting up 3 biological replicates, the cells were photographed under an inverted fluorescence microscope to obtain images. 4. Pick a single colony and inoculate it into nutrient broth. Incubate at 37 ℃ and 180 rpm for 12 h on a shaker. Adjust the bacterial concentration to 1×10⁻⁶ with sterile physiological saline. 6 CFU / mL, using a sterile cotton swab to collect bacterial suspension, spread evenly on the surface of an LB agar plate three times, rotating the plate 60 degrees each time. ° Finally, spread the antibacterial agent around the edge of the plate, let it stand at room temperature for 5 minutes to dry, and incubate at 37 ℃ for 48 h. Measure the diameter of the transparent inhibition zone around each sample with calipers.

[0041] The experimental results obtained using the above experimental method are shown below: like Figure 1 The images show the metallographic structure and grain size statistics of the porous magnesium alloy anal drainage tubes prepared in Examples 1-3 of this invention. It can be observed that the outer layer grains significantly increased after laser selective annealing, while the inner layer maintained relatively fine grains. The ratio of coarse to fine grains was obtained by statistical analysis of the grain size using ImageJ software. Specifically, the ratio of coarse to fine grains in the porous magnesium alloy anal drainage tube prepared in Example 1 was 1:1. Figure 1 a and Figure 1 As shown in d), the ratio of coarse grains to fine grains in Example 2 is 3:2 ( Figure 1 b and Figure 1 As shown in e), the ratio of coarse grains to fine grains in Example 3 is 3:7 ( Figure 1 c and Figure 1(as shown in f). This invention utilizes laser selective annealing to precisely control laser energy, directionally inducing a non-equilibrium recrystallization process in magnesium alloy wire. First, strain-free new crystal nuclei form within the original fine-grained structure. During growth, these nuclei not only engulf the surrounding deformed matrix to achieve grain growth, but their growth direction is also guided by the direction of heat flow and the stress field, thus tending to form a new crystallographic orientation different from the original drawn texture. This process creates a "coarse outside, fine inside" grain size gradient and simultaneously achieves a "dispersed outside, woven inside" crystal orientation gradient, transforming the material from a passive homogeneous body into an active functional gradient body, thereby realizing the biological function of the drainage tube: "timed sacrificial degradation of the outer layer and durable stable support of the inner layer."

[0042] like Figure 2 The X-ray diffraction patterns of the inner and outer layers of the magnesium alloy porous anorectal drainage tube prepared in Example 1 of this invention are shown. From the relative diffraction peak intensities of different crystal planes, it can be seen that after laser selective annealing, the diffraction peaks of the (0002) crystal plane of the outer layer are significantly enhanced, indicating that the (0001) close-packed planes of a large number of grains are parallel to the surface; while the inner layer still maintains the texture characteristics with the [10-11] crystal orientation parallel to the axial direction of the wire.

[0043] The highly reactive crystal planes, such as (10-11), still exist in the coarse-grained outer layer, which rapidly dissolve and release Mg in the body fluid environment. 2+ and with Cl - PO4 3- Plasma and organic molecules combine to form a porous, loose amorphous corrosion product layer on the surface. This product layer has weak protective properties and is difficult to block Cl. - The corrosion continues to penetrate the material. At the same time, the coarse-grained structure has a low grain boundary density, making it difficult for corrosion to disperse. It tends to propagate deep into the material along a few active grain surfaces, thus enabling the outer layer to degrade rapidly in an acidic environment, releasing magnesium ions to inhibit bacteria, reduce inflammation, and promote healing.

[0044] The inner layer has a fine-grained structure with small grains, high grain boundary density, and a significant proportion of active crystal faces such as (10-11) in the crystal orientation. This structure results in highly uniform corrosion in the early stages, where released magnesium ions rapidly co-precipitate with abundant chloride ions, phosphate ions, carbonate ions, and organic molecules in the intestinal fluid. This process is extremely kinetic, and the various precipitates interfere with each other, making it difficult to form an ordered crystal structure. Consequently, a dense, complex amorphous protective film covers the inner surface, effectively delaying further corrosion and maintaining the mechanical support function of the drainage tube during the healing process.

[0045] like Figure 3This is a comparison of the degradation rates of the anorectal drainage tubes prepared in Examples 1, 1, 3, and 6-8 of this invention in simulated intestinal fluid (SIF) with different pH levels. The pH changes near the wound are mainly due to bacterial infection and metabolic acid production, tissue ischemia and anaerobic metabolism, poor drainage, and accumulation of acidic substances. Therefore, a pH of 9 was chosen. Figure 3 a) or 6 ( Figure 3 b) As an extreme environment of the anus and rectum, it can quickly and clearly reveal the failure tendency of materials under different corrosion driving forces. From Figure 3 As shown in Figure a, the degradation rate of the drainage tube is relatively fast in alkaline intestinal fluid, but the overall degradation trend is the same. In the early stages of degradation, Example 1 showed almost no mass loss; as time progressed, the mass of the drainage tube began to decrease, and the degradation rate accelerated, reaching zero mass after about 40 days, indicating that the drainage tube had completely degraded. This heterogeneous structure actively avoids the formation of an overly stable amorphous corrosion product film in the in vivo environment, ensuring the continuous and effective release of magnesium ions. The Mg-8Li rectal drainage tube of Comparative Example 1 and the Mg-1Zn rectal drainage tube of Comparative Example 3 showed high degradation rates in the early stages, reaching near-complete degradation after 18 days; while the rubber drainage tube of Comparative Example 6 showed almost... There was almost no loss of mass, which confirms its non-degradable nature, requiring a second surgery for removal; Comparative Example 7, due to its homogeneous fine crystal structure, easily forms a stable protective film, resulting in an excessively slow degradation rate, unable to meet the clinical requirement of approximately 4 weeks for degradation and excretion, and its slow ion release rate makes it difficult to effectively regulate wound healing with bioactivity; Comparative Example 8, due to its homogeneous coarse crystal structure, cannot form a dense film layer on its surface, is easily corroded in intestinal fluid, and has a faster degradation rate, failing to provide effective drainage support for wound healing. In acidic intestinal fluid ( Figure 3 (b) In Example 1, the mass of the drainage tube began to decrease over time, and the degradation rate accelerated. By about 35 days, the remaining mass was 0, indicating that the drainage tube had completely degraded. In Comparative Example 1, the degradation rate was extremely fast, and it lost its supporting drainage function in about 12 days. Comparative Example 3 also degraded completely in about 20 days. Comparative Example 6 showed almost no mass loss during the 45 days of the experiment. In Comparative Example 7, due to the effect of fine crystals, the degradation rate was extremely slow, and it could not release enough ions to promote wound healing. In Comparative Example 8, due to its coarse crystals throughout, the degradation rate was relatively fast, and it lost its supporting drainage function before the wound healed. Therefore, only when the pH value of Example 1 changed between 6 and 9 could the drainage support performance of the product be met during the wound healing period.

[0046] like Figure 4 The images show the X-ray diffraction patterns of the rectal drainage tubes prepared in Comparative Examples 7 and 8 of this invention after being immersed in simulated intestinal fluid (SIF) at pH=6 for 24 h. Figure 4In Comparative Example 7 (a), the amorphous phase formed on the outer layer is clearly distinguishable. The amorphous phase has a more dense atomic packing, making it difficult for corrosive media (such as intestinal fluid) to penetrate. Simultaneously, it prevents grain boundaries and precipitates of the crystalline phase from becoming weak points for localized corrosion, thereby reducing localized dissolution and cracking during the degradation process, and thus lowering the corrosion rate of the magnesium alloy. This result is consistent with... Figure 3 The slow degradation rate of Comparative Example 7 is corroded. Comparative Example 8 showed surface corrosion, but no dense amorphous protective layer formed. This is because the highly reactive crystal planes (10-11) present in the coarse-grained structure rapidly dissolve and release Mg in the body fluid environment. 2+ and with Cl - PO4 3- Plasma and organic molecules combine to form a porous, loose amorphous corrosion product layer on the surface. This product layer has weak protective properties and is difficult to block Cl. - The continuous penetration of the corrosive material, coupled with the low density of grain boundaries in the coarse-grained structure, makes corrosion difficult to disperse and prone to propagate deep into the material along a few active grain surfaces.

[0047] like Figure 5 The diagram shows the bending fatigue curves of the rectal drainage tubes prepared in Embodiment 1 and Comparative Examples 3-5 of this invention. The bending deformation angle experienced by the rectal drainage tubes after implantation in the human body is approximately 10°. ° ~25 ° The maximum bending angle set in this experiment is 25 degrees. ° The experimental environment used was simulated intestinal fluid (SIF) at pH 6. As shown in the figure, Example 1 exhibited a mechanical performance decrease of approximately 20% after 5000 cycles, which is sufficient to meet the basic mobility needs of patients during treatment and recovery. Analysis of the drainage tube structure reveals that it is woven from metal wires; its mesh structure allows the wires to slide when the tube is bent, thus reducing its bending degree. Comparative Example 3, lacking Li, had a lower initial strength (approximately 240 MPa), and its performance significantly declined in subsequent fatigue tests, failing to maintain the basic strength requirements. Comparative Example 5, with a larger mesh area, achieved a higher strength at 1×10⁻⁶ MPa. 4 It retains high strength after several cycles, but the large mesh area causes large holes when it bends, making it easy for inflammatory fluid, pus, exudate from anorectal wounds, and small amounts of blood to seep into the wound and cause infection. In contrast, the mesh area of ​​Comparative Example 4 is too small. Although the risk of infection can be avoided, the sliding of the filament is hindered and the performance is significantly reduced. It breaks after about 6,000 cycles.

[0048] like Figure 6The figures show the proliferation morphology of human anorectal mucosal fibroblasts on the surface of the anorectal drainage tubes prepared in Examples 2, 1-2, and 6 of this invention. As can be seen from the figures, human anorectal mucosal fibroblasts are adhered to the surface of each drainage tube; among them, the anorectal drainage tube prepared in Example 2 (… Figure 6 d) The surface of the drainage tube showed the highest number of fibroblasts, which were concentrated and evenly distributed across the surface. In contrast, the other comparative examples showed fewer fibroblasts on the surface of their respective anorectal drainage tubes. This result is consistent with... Figure 7 The cell proliferation rates shown are consistent, compared to Example 6 ( Figure 6 a) Only a few fibroblasts adhere to the surface, the number is minimal, and the distribution is uneven.

[0049] like Figure 7 The figure shows a statistical graph illustrating the proliferation rate of human anorectal mucosal fibroblasts on the extracts of the anorectal drainage tubes prepared in Example 2 and Comparative Examples 1-3 of this invention (based on pure magnesium, where the cell proliferation rate is 100%). As shown in the figure, the cell proliferation rate of the extract in Example 2 reached 212.5%, and the cell proliferation rate of the extract in Comparative Example 3 was 198.3%, significantly higher than that of the Mg-8Li group (140.6%) and the Zn-8Li group (130.4%). This reflects the effect of Mg 2+ With Zn 2+ Synergism is achieved through cross-activation of the PI3K / Akt signaling pathway, Mg 2+ Direct activation of this pathway promotes cell proliferation and inhibits apoptosis, Zn 2+ As components of zinc finger proteins, they regulate the gene expression of growth factors such as VEGF and bFGF, amplifying pro-angiogenic signals. Simultaneously, both enhance the activity of DNA / RNA synthetases and alkaline phosphatase, improving cellular nucleic acid synthesis and energy metabolism efficiency, and accelerating fibroblast migration. Comparative Example 1 did not contain Zn, Mg... 2+ It can directly activate the PI3K / Akt signaling pathway, but the lack of growth factors such as VEGF and bFGF leads to slowed cell proliferation. Comparative Example 2 did not include Mg, which prevented the activation of the PI3K / Akt signaling pathway. Zn... 2+ The presence of [a specific substance] can activate alkaline phosphatase, carbonic anhydrase, etc., which can promote nucleic acid synthesis and energy metabolism in cells, accelerate cell differentiation, and prepare a large amount of raw materials for cell proliferation and differentiation. However, cell proliferation is inhibited by the PI3K / Akt signaling pathway. Therefore, Example 2 and Comparative Example 3 [were discussed in the context of Mg]. 2+ With Zn 2+ The combined effects of these substances promoted the proliferation and differentiation of human anorectal mucosal fibroblasts, with a cell proliferation rate higher than that of comparative examples 1 and 2.

[0050] like Figure 8The figures show the antibacterial effect of the rectal drainage tubes prepared in Examples 1-3 and Comparative Examples 1-2 against *Escherichia coli*. As can be seen from the figures, the diameter of the inhibition zone in Examples 1-3 is approximately 35 mm, while the diameter of the inhibition zone in Comparative Example 1 is 27 mm and the diameter of the inhibition zone in Comparative Example 2 is 25 mm. The diameter of the inhibition zone in Examples 1-3 is 8-10 mm larger than that in Comparative Examples 1 and 2, demonstrating that Mg... 2+ With M n+ They exhibit significant synergistic antibacterial effects; when both are present together, their inhibitory effect on Escherichia coli is far superior to that of a single ion. M n+ By disrupting the phospholipid bilayer of the E. coli cell membrane, increasing cell membrane permeability, it leads to intracellular electrolyte imbalance and nutrient leakage; simultaneously, it competitively binds to the active sites of bacterial metabolic enzymes, inhibiting DNA / RNA synthetase function and hindering bacterial proliferation; while Mg 2+ To further amplify this effect, both M n+ It inhibits bacterial enzymes and enhances antibacterial stability by regulating the local microenvironment.

[0051] like Figure 9 The image shows the metallographic structure of the rectal drainage tubes prepared in Comparative Examples 9-11 of this invention. Figure 9 As can be seen in Comparative Example 9, the anal drainage tubes directly extruded from rods have larger grains. Subsequent experiments revealed that their mechanical and corrosion properties were poor, and they could not be obtained with heterogeneous structures through laser selective annealing. Figure 9 As can be seen in Comparative Example 10 (b), the microstructure of Comparative Example 10 is extremely similar to that of the untreated raw filament (Comparative Example 7), with no obvious grain size gradient observed from the surface to the core. The average grain size of the outer layer is only slightly different from that of the core, making it impossible to form an effective gradient structure in the filament. The product performance reverts to a homogeneous, fine-grained state, failing to achieve the design goal of controllable degradation of the outer coarse grains in this invention. Figure 9 As can be seen in Comparative Example 11 (c), abnormal grain growth occurred in the outer layer, with some forming coarse equiaxed grains that abruptly interfaced with the fine-grained structure in the core, disrupting the continuity of the structure and creating an abnormal structure that is inconsistent with the matrix. This structure is highly susceptible to inducing uneven pitting corrosion and localized accelerated degradation in corrosive environments, making the degradation behavior of the product completely uncontrollable. Furthermore, the abnormally grown grains lead to the deterioration of the mechanical properties of the outer layer.

[0052] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A magnesium alloy porous rectal drainage tube, characterized in that, The chemical composition of the magnesium alloy porous anorectal drainage tube is: Mg-xLi-yM; where M represents one of Ca, Zn, Ti, and Sr; x and y represent the mass fractions of Li and M: 4≤x≤20, 1≤y≤10, and the balance is Mg; the magnesium alloy porous anorectal drainage tube has a double-layer structure, with a coarse-grained outer layer and a fine-grained inner layer, and the ratio of coarse to fine grains is 1:1, 3:2, or 3:7; the diameter of the magnesium alloy porous anorectal drainage tube is 0.5~2.0 cm, the length is 8~15 cm, and the mesh diameter is 100~300 μm.

2. The method for preparing a magnesium alloy porous anal drainage tube according to claim 1, characterized in that, Follow these steps in sequence: S1. Weigh the raw materials according to the proportion, place the pure magnesium in a vacuum electric arc melting furnace, ignite the electric arc under a vacuum or high-purity argon protective atmosphere, melt the pure magnesium to form a stable molten pool, then add Li and M elements in batches and use electric arc stirring to achieve composition homogenization, and obtain magnesium alloy ingot. S2. The magnesium alloy ingot is machined to remove the oxide scale on the surface and at both ends, and then hot extruded to obtain magnesium alloy bars with a diameter of 2 to 10 mm. S3. Perform multiple cold drawing processes on magnesium alloy bars, and perform annealing treatment between each adjacent processing pass to obtain magnesium alloy wire with a diameter of 0.2 to 1 mm. S4. The magnesium alloy wire is woven into a dense porous tube, and then annealed and shaped under vacuum or high-purity argon to obtain a magnesium alloy porous tube. S5. Fix the magnesium alloy porous tube on the platform and perform laser treatment, making the laser beam scan in a straight line along the axial direction of the wire, repeating multiple times to obtain the magnesium alloy porous drainage tube.

3. The method for preparing a magnesium alloy porous anal drainage tube according to claim 2, characterized in that, In step S1, the vacuum degree is 10 during the vacuum arc melting process. -3 Pa or 10 -4 Pa, voltage 25-35 V, current 100-200 A, arc heating time 3-10 min.

4. The method for preparing a magnesium alloy porous anal drainage tube according to claim 2, characterized in that, In step S2, the temperature of the hot extrusion is 200~500 ℃ and the speed is 0.2~1 mm / min.

5. The method for preparing a magnesium alloy porous anal drainage tube according to claim 2, characterized in that, In step S3, during the multi-pass cold drawing, the deformation per pass is 5-20%.

6. The method for preparing a magnesium alloy porous anal drainage tube according to claim 2, characterized in that, In step S3, the annealing temperature is 200~500 ℃ and the time is 5~20 min.

7. The method for preparing a magnesium alloy porous anal drainage tube according to claim 2, characterized in that, In step S4, the annealing temperature is 200~400 ℃ and the time is 10~60 min.

8. The method for preparing a magnesium alloy porous anal drainage tube according to claim 2, characterized in that, In step S5, during the laser processing, the laser spot diameter is 0.2~0.8 mm, and the surface temperature of the magnesium alloy porous tube is 300~500℃.

9. The method for preparing a magnesium alloy porous anal drainage tube according to claim 2, characterized in that, In step S5, the scanning speed of the laser beam during linear scanning along the axial direction of the wire is 100~300 mm / s. After a single axial scan, the wire is rotated 90 degrees. ° The scanning process is repeated 4 to 10 times in total.

Images