A degradable magnesium alloy in-situ composite anamosticstaple and preparation method therefof

Abstract

A degradable magnesium alloy in-situ composite staple and a preparation method therefor, relating to the technical field of biomedical materials. The staple is made of a composite structural material

Description

degradable anastomotic staples. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an SEM micrograph of the magnesium matrix composites. Wherein, layer 2 is the in-situ composite MgF2, layer 3 is the magnesium alloy matrix, and layer 1 is the epoxy resin required to prepare the sample. DETAILED DESCRIPTION In the detailed description of the preferred embodiment, the present disclosure provides a degradable anastomotic staple with a high biosafety level, good mechanical properties and plasticity, and excellent corrosion resistance through alloying combined with drawing and in-situ synthesis. The embodiments of the present disclosure will be further described in detail as follows with reference to the drawings. The embodiments are implemented based on the technical solution of the disclosure with the specific implementation method and procedures given. However, the protection scope of the disclosure is not limited to the following embodiments. In this embodiment, the anastomotic staples are prepared in the following way: melt pure magnesium, 1% Zn and 1% Nd into liquid based on weight percentage; cast the liquid metal into ingots and remove their surface defects and impurities; homogenize the ingots at 400°C for 4 h and make magnesium alloy bars with a diameter of 10 mm (extrusion ratio of 70:1) by hot extrusion at 430°C; cold-draw the bars to make wires with a diameter of 0.3 mm and anneal the wires at 300°C for 60 min. Make U-shaped anastomotic staples out of magnesium alloy wires with an elliptical bending part, a total length of 10-15 mm, a height of 3-6 mm, and an end face diameter of 0.20-0.35 mm. Electropolish the anastomotic staples for 5 min under a voltage of 15 V to remove surface defects and impurities with a mixture of 2-ethoxyethanol, absolute ethanol, and phosphoric acid at a volume ratio of 1:2:2 (the weight concentration of phosphoric acid being 85%). Then ultrasonically clean and dry the anastomotic staples, and immerse them into hydrofluoric acid with a weight concentration of 35% for in-situ synthesis with magnesium fluoride at room temperature for 6 h. Finally, ultrasonically clean, dry and vacuum-seal the anastomotic staples. Mechanical properties and cytotoxicity data of the anastomotic staples in this embodiment are presented in Table 1 and corrosion resistance data is provided in Table 2. In this embodiment, the anastomotic staples are prepared in the following way: melt pure magnesium, 1.73% Zn and 0.68% Nd into liquid based on weight percentage; cast the liquid metal into ingots and remove their surface defects and impurities; homogenize the ingots at 380°C for 6 h and make magnesium alloy bars with a diameter of 10 mm (extrusion ratio of 60:1) by hot extrusion at 420°C; cold-draw the bars to make wires with a diameter of 0.3 mm and anneal the wires at 280°C for 120 min. Make U-shaped anastomotic staples out of magnesium alloy wires with an elliptical bending part, a total length of 10-15 mm, a height of 3-6 mm, and an end face diameter of 0.20-0.35 mm. Electropolish the anastomotic staples for 3 min under a voltage of 20 V to remove surface defects and impurities with a mixture of 2-ethoxyethanol, absolute ethanol, and phosphoric acid at a volume ratio is 1:2:2 (the weight concentration of phosphoric acid being 85%). Then ultrasonically clean and dry the anastomotic staples, and immerse them into hydrofluoric acid with a weight concentration of 40% for in-situ synthesis with magnesium fluoride at room temperature for 7 h. Finally, ultrasonically clean, dry, and vacuum-seal the anastomotic staples. Mechanical properties and cytotoxicity data of the anastomotic staples in this embodiment are presented in Table 1 and corrosion resistance data is provided in Table 2. In this embodiment, the anastomotic staples are prepared in the following way: melt pure magnesium, 1.6% Zn and 0.7% Nd into liquid based on weight percentage; cast the liquid metal into ingots and remove their surface defects and impurities; homogenize the ingots at 420°C for 5 h and make magnesium alloy bars with a diameter of 10 mm (extrusion ratio of 80:1) by hot extrusion at 410°C; cold-draw the bars to make wires with a diameter of 0.3 mm and anneal the wires at 320°C for 30 min. Make U-shaped anastomotic staples out of magnesium alloy wires with an elliptical bending part, a total length of 10-15 mm, a height of 3-6 mm, and an end face diameter of 0.20-0.35 mm. The anastomotic staples are electropolished to remove surface defects and impurities. The electropolishing solution used is a mixture with the volume ratio of 2-ethoxyethanol: absolute ethanol: phosphoric acid = 1:2:2 and the weight concentration of phosphoric acid of 85%. The electropolishing lasts for 6 min under a voltage of 10 V. Then the anastomotic staples are ultrasonically cleaned, dried and immersed into hydrofluoric acid with a weight concentration of 45% for in-situ synthesis with magnesium fluoride at room temperature for 8 h. Finally, the anastomotic staples are ultrasonically cleaned, dried and vacuum-sealed. Mechanical properties and cytotoxicity data of the anastomotic staples in this embodiment are presented in Table 1 and corrosion resistance data is provided in Table 2. TABLE 1 MECHANICAL PROPERTIES AND CYTOTOXICITY OF ANASTOMOTIC STAPLES Tensile Strength (MPa) Yield Strength (MPa) Elongation (%) Cytotoxicity EMBODIMENT 1 310.2 236.2 25 Grade 0 EMBODIMENT 2 296.4 221.6 27 Grade 0 EMBODIMENT 3 314.2 239.7 29 Grade 0 TABLE 2 CORROSION RESISTANCE OF ANASTOMOTIC STAPLES Eo (V) Ic (A / cm2) Rp (Q / cm2) EMBODIMENT 1 -1.56 5.23x1 O’7 3.65xl05 EMBODIMENT 2 -1.53 6.59xl0-8 5.3xl05 EMBODIMENT 3 -1.49 3.59X10-8 6.8xl05 From Table 1 and Table 2, it can be concluded that the anastomotic staples 5 of the present disclosure have high tensile strength and excellent plasticity that meet the requirements for mechanical properties, and that the cytotoxicity of the anastomotic staples is Grade 0, indicating that the anastomotic staples have high cytocompatibility. As shown in FIG. 1, it can be seen from the SEM micrograph of io magnesium matrix composites that there is no obvious delamination between the matrix of the composites and in-situ composite MgF2, which is different from conventional coatings. The in-situ composite MgF2 layer ensures the structural and property stability of the material, and improves the corrosion resistance of the alloy. 15 The embodiment results show that the magnesium alloy composite anastomotic staple provided by the present disclosure has good plastic deformation ability and mechanical strength, a low degradation rate, and a high biosafety level, which can meet the requirements of in vivo implantation. In addition, it can gradually degrade in vivo after achieving the medical effects in vivo, avoiding a second operation for removal.

Claims

1. A degradable magnesium alloy in-situ composite anastomotic staple, comprising an internal part and an external part; wherein the internal part is a wire made of Mg-Zn-Nd magnesium alloy, and the Mg-Zn-Nd magnesium alloy consists of the following components in weight percentage: 1,0%-3.0% of Zn, 0.2%-l .0% of Nd, and the rest is Mg, characterized in thatthe external part is corrosion-resistant MgF2, the corrosion-resistant MgF2 is in-situ synthesized onto an outer layer of the Mg-Zn-Nd magnesium alloy.

2. The degradable magnesium alloy in-situ composite anastomotic staple according to Claim 1, wherein technical indicators of the degradable magnesium alloy in-situ composite anastomotic staple are described as follows: a tensile strength range of 260-320 MPa, a yield strength range of 170-240 MPa and an elongation of 20-33%.

3. The degradable magnesium alloy in-situ composite anastomotic staple according to Claim 1, wherein a thickness of the corrosion-resistant MgF2 on the outer layer is 1.0 pm-3.3 pm.

4. A preparation method of the degradable magnesium alloy in-situ composite anastomotic staple according to any one of Claims 1 to 3, characterized in that it includes the following operating steps:(1) melting pure Mg, Zn and Nd in proportion into magnesium alloy, casting it into ingots and homogenize the ingots at 300-450°C for 3-7h;(2) removing surface defects and impurities of the magnesium alloy ingots from Step (1), and extruding them into bars with a diameter of 8-10 mm as per an extrusion ratio of 60-80:1 at a temperature of 390-470°C;(3) cold-drawing the magnesium alloy bars from Step (2) into wires with a diameter of 0.2-0.6 mm, and anneal them at a temperature of 280-330°C for 30 min-120 min;(4) making U-shaped anastomotic staples out of the magnesium alloy wires from Step (3);(5) electropolishing the magnesium alloy anastomotic staples from Step (4) to remove surface defects, and then ultrasonically cleaning and drying them;(6) immersing the magnesium alloy anastomotic staples from Step (5) into the hydrofluoric acid with a weight concentration of 20%-60% for in-situ synthesis with MgF2 at 20-35°C 5 for 3h-200h;(7) ultrasonically cleaning and drying the in-situ composite magnesium alloy anastomotic staples from Step (6), and vacuum-seal them.

5. The preparation method according to Claim 4, characterized in that in Step (4), the U-shaped anastomotic staple is 10-15 mm long and 3-6 mm high with an elliptical bending 10 part and an end face diameter of 0.20-0.35 mm.

6. The preparation method according to Claim 4, characterized in that in Step (5), fine electropolishing is carried out with the polishing solution, a mixture with the volume ratio of 2-ethoxy ethanol: absolute ethanol: phosphoric acid = 1:2:2, and the weight concentration of phosphoric acid of 85% for 1-10 min under the voltage of 10-20 V.

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