Study On The Preparation,Microstructure And Properties Of Novel Biodegradable Mg-Zn-Ca-Y Hemostatic Clips

Laparoscopic surgery has received more and more attention due to the minimization of tissue damage and more rapid postoperative recovery.In the course of surgery,hemostatic clip is usually used to ligature the ruptured blood vessels.The clinical hemostatic clips are titanium clips or polymer clips.However,the titanium clips need to be removed by secondary surgery,and the polymer clips corrode too fast.A new hemostatic clip that is capable of self-degradation and has good mechanical properties.Magnesium?Mg?alloys have received much attention due to their low density,low toxicity and good biocompatibility.In this paper,Mg-3Zn-0.2Ca-0.5Y alloy was studied,the microstructure changes of as-cast and extruded alloys and different annealing temperatures and time treatments,as well as the effects of different heat treatment processes on the mechanical properties of the sheets were investigated.The new hemostatic clip designed a"V"shape.The thickness of hemostatic clip's arm increased from the tail to the tip to ensure the safety of the internal clamping experiment.The in vitro degradation of Mg-3Zn-0.2Ca-0.5Y alloy sheet and hemostatic clip was investigated by electrochemical noise test and immersion test in SBF in vitro.The actual clamping experiment of carotid artery in SD rats explored the actual effect of the new hemostatic clip.The effect of clamping the blood vessel,the corrosion of the body and the effects of corrosion products on the physiological functions of the body.Based on the above research,the experimental results are as follows:?1?Compared with the as-cast state,the grain of the plate after extrusion is remarkably refined,and the size is reduced from the original 130?m to about 5?m.The mixed phases of MgZn and Mg₂₄Y₅ were distributed at the grain boundary of the extruded sheet,and the matrix was mainly?-Mg and Ca₂Mg₆Zn₃ phases.After extrusion,a large number of deformed grains existed in the plate.After annealing,the grains were completely recrystallized.Due to the presence of solute atoms such as Zn,Ca and Y,the recrystallization temperature was increased by nearly 100?compared with pure magnesium.Annealing at 310?for too short or too long was unfavorable for the sheet,recrystallization is incomplete?30 min?and annealed twin appeared?120 min?.?2?The finite element simulation of the new hemostatic clip structure found that the inner side of the tip of the clip is the region with the largest strain,the maximum strain reached 0.13,and the elongation of the extruded sheet was only about 12%.The elongation of the sheet after annealing at 310?for 90 min was increased to 21%,the tensile strength and yield strength were 225 MPa and 125 MPa,respectively.The bending and compression properties were good,and the compression elongation was 17.7%,which satisfied the requirement that the hemostatic clip completely clamped the blood vessel.?3?The Mg-3Zn-0.2Ca-0.5Y plate was dominated by uniform corrosion 2h before soaking in SBF.After two days of corrosion,the tendency of pitting corrosion appeared.The corrosion rate of the plate increased first and then decreased.The increase was mainly due to the occurrence of pitting,and the decrease was mainly due to the formation of a protective corrosion product on the surface.The open and closed hemostatic clips had different corrosion rates in SBF,and the closed state corrodes faster due to the large number of twins.?4?The new Mg-3Zn-0.2Ca-0.5Y hemostatic clip can completely clamp carotid artery of SD rats.The hemostatic clip can maintain the mechanical properties of the hemostasis during the complete healing period of the SD rat's vascular?about two weeks?.The degradation of the hemostatic clip in SD rats occurred preferentially at the arm where the hemostatic clip was in contact with the blood vessel.After one month,the hemostatic clip's arm was broken,and the period of degradation of the hemostatic clip in SD rats was about 5 months.The physiological indexes of SD rats were normal after operation.The degradation of hemostatic clips and corrosion products had no effect on the physiological functions of SD rats.