Study On The Fabrication And Properties Of Biodegradable Mg-Zn-Ca Alloy Hemostatic Clip For Laparoscopic Surgery

Titanium alloy clip is a conventional hemostatic clip used in laparoscopic surgery at present,but its permanent remaining in body brings some problems such as ion dissolution inflammation,image interference.Polymer hemostatic clip can biodegrade in body,there are still much more technical requirements for operators and higher cost for patients due to its complex structure.The development of new type biodegradable magnesium alloy hemostatic clip for laparoscopic surgery has important practical significance to solve the current limitations of conventional hemostatic clips fabricated by titanium alloy or polymer.A new preparation process for hemostatic clips was developed using Mg-3Zn-0.2Ca alloy.The evolution of the microstructure during fabrication process mechanical properties and degradation performance in vitro,biological evaluation in vivo were studied in this paper.The following conclusions can be drawn from the investigation :1.The gain size of as-extrude Mg-3Zn-0.2Ca alloy sheet is significantly refined due to dynamic recrystallization.The base plane texture paralleled to the extrusion direction was formed after extrusion.After blanking forming,the characteristic of the texture is(0001)basal texture paralleled to the extrusion normal surface.After stress relieving annealing,the microstructure became more uniform,and the grain size became larger with increasing the annealing temperature and annealing time.After annealing at 300 ? for 120 min,the texture type remained same,while the texture density and the intensity reduced.2.The finite element simulation result obtained by ANSYS 14.0 shows that the maximum strain is 0.247,distributed on the top middle of the clip.After annealing,the strength of magnesium alloy sheets is decreased,elongation is increased and the actual occlusion performance of clip is improved.The optimised route of annealing is annealed at300 ? for 120 min.By this way,magnesium alloy clips acquire good mechanical property.3.Mg-3Zn-0.2Ca alloy hemostatic clip was immersed in vitro for 48 h,the pH and weightlessness are increased with the extension of immersion time,The clamping performance of hemostatic clip is gradually declined with the degradation of Mg-3Zn-0.2Ca alloy.The hemostatic clips are not ruptured during immersed 48 h in vitro.4.Mg-3Zn-0.2Ca alloy shows no cytotoxicity to L929 cells.After hemostatic clamp implanted in rats for 1~4 weeks,the vital signs are normal;blood biochemical index are normal either;tissue reaction are qualified.Magnesium alloy hemostatic clip can completely clamp the left kidney blood vessels of rats without bleeding.The rats are alive without blood exudation after two weeks.The structure of the hemostatic clips are integrated but the surface of the hemostatic clips is degraded.