Study On Mechanical Properties And Corrosion Properties Of Mg-Gd Series Alloys For Esophageal Stent Materials

In recent years,Unhealthy eating habits also contribute to the increasing number of patients with advanced esophageal cancer,which threatens people's health and life safety.Stent implantation is an important method for the treatment of esophageal cancer at present.However,traditional scaffold implantation materials such as stainless steel are non-degradable and need to be removed by a second operation.Moreover,they have adhesion and proliferation effects on cancer cells,fibroblasts,epithelial cells and other pathological cells,which will affect the effectiveness of scaffold and cause esophageal restenosis.Therefore,it is urgent to explore a biodegradable esophageal scaffold material with inhibitory effect on pathological cells,and magnesium alloy has become the only choice due to its series of matching advantages.In this paper,two magnesium compounds Mg-2Gd-0.5Zr(abbreviated as Mg-Gd-Zr)and Mg-5Gd-3Y-0.5Zn-0.5Zr(abbreviated as Mg-Gd-Y-Zn-Zr)were selected to study the corrosion degradation of PBS simulated body fluids which simulated esophagus environment,and the alloy materials with strong corrosion resistance and inhibitory ability to pathological cells were screened out.The next step was the preparation of wire materials.It provides a new possibility for the selection of magnesium alloy esophageal stent materials.Electrochemical experiments show that the corrosion current densities of Mg-Gd-Zr and Mg-Gd-Y-Zn-Zr alloys in PBS simulated body fluids are 1.72×10^-5 A/cm² and2.15×10^-5 A/cm²,respectively.Electrochemical impedance spectroscopy(EIS)fitting shows that the impedance modulus of Mg-Gd-Zr alloy is higher;Tensile tests show that the elongation of Mg-Gd-Zr alloy is about 40%,and the tensile strength of Mg-Gd-Y-Zn-Zr alloy is about 300MPa.In vitro corrosion experiments showed that Mg-Gd-Zr alloy had stronger corrosion resistance than Mg-Gd-Y-Zn-Zr alloy in PBS simulated body fluids,and the average corrosion rate of Mg-Gd-Zr alloy was 0.23mm/a after 14 days of immersion.Biocompatibility experiments showed that compared with Mg-Gd-Y-Zn-Zr alloy and pure magnesium extract,esophageal cancer cell EC109 had the lowest relative activity in the Mg-Gd-Zr alloy extract.;In the experiment of direct contact material culture of esophageal cancer cells(EC109),the survival rate of cells cultured on Mg-Gd-Zr alloy was the lowest.The above results indicate that Mg-Gd-Zr alloy has the strongest inhibitory effect on the proliferation of esophageal associated pathological cells.In view of the application prospect of braid method for preparing esophageal stents,and considering the degradation properties,biological properties and mechanical properties of the materials,Mg-Gd-Zr alloy was selected for wire drawing experiments;The results show that with the drawing process,the texture of the samples is dominated by the fiber texture,and the base plane texture with the direction of<1010>//ED is formed after the drawing.The texture strength weakens after annealing.After soaking in PBS simulated body fluid for 7 days,the corrosion resistance increased with the decrease of the diameter of the wire.