| Magnesium alloy has been widely researched and used in health-care field as a medical bio-metal.To solve the clinical security and artifacts problems go with the use of titanium clip and overcome these drawbacks of the polymer clip,such as complex structure and lower strength.In this work,clips were designed by changing the composition and structure of the alloy,fabricated by combined the servies condition with the good biodegradability and mechanical properties of magnesium.The microstructure,mechanical properties,in vitro degradation behavior and biocompatibility of hemostatic clips was studied.The effects of structure and composition on properties of hemostatic clips were discussed.The existing deficiencies were solved and the clinical application of magnesium-based hemostatic clips were promoted.These results suggest that:1.By contrasting the microstructure evolution of Mg-2Zn-0.2Ca and Mg-4Zn-0.2Ca alloys shows that the content and the morphology of second phase changed with the increase of Zn content in as-cast Mg-Zn-Ca alloy.Extruded Mg-Zn-Ca alloy plate has the unrecrystallized characteristics.The hemostatic clip obtained by blanking has the same microstructure as the plate.The as-blanked Mg-Zn-Ca clip has a strong basal texture with the intensity of 19.639.The microstructure of the hemostatic clip after solution treatment at 380°C for 2h was fine and uniform.Some of the grains were overgrown after solution treatment at 380°C for 12 h and the phenomenon more obvious with the increase of Zn content.The texture was significantly weakened and decreased to 6.810 after solution treatment.2.The extruded plate has the highest yield strength and tensile strength,the strength of the plate decreased after heat treatment,and the elongation shown a rule that increased first and then decreased with the prolongation of solution time.The mechanical properties of 380°C-2h solution-treated Mg-Zn-Ca plate were measured after immersion for different periods and it can maintained certain strength and ductility within two weeks.3.As-blanked clips have visible cracks or fracture after clamped.Solution-treated clips can avoid the appearance of visible cracks.The texture type and intensity at the top part of clip was changed after the Mg-Zn-Ca clip clamped.The clip blanked along the extrusion direction has better deformability compared with the clip blanked perpendicular to the extrusion direction.The clamped ‘R' shape clip can effectively reduce the stress concentration phenomenon with less twins generated,shown a better room temperature deformability than ‘V' shape clip.The number and size of twins in clamped clips raised significiantly with the increase of Zn contene.The closure performance of Mg-Zn-Ca clips with different solution treatment were tested,all of them can maintain 300 mmHg pressure.4.Solution treatment can slow down the corrosion of clip.With the increase of Zn content,the corrosion rate of clip is accelerated.The effective pressure maintenance period of 380°C-2h solution-treated ‘R' shape clip was more than 4 weeks,and ‘V' shape clip was about 3 weeks.With the prolongation of solution time,the pressure maintenance periods of clips become shorter.The clip blanked along the extrusion direction has better corrosion uniformity and pressure maintenance effect.The ‘R' shape clip shows better pressure maintenance effect and corrosion resistance than ‘V' shape clip.5.The left common carotid of rats can be successfully closed by hemostatic clips,none of the rats was death.Blood biological test and histological analysis shown that there is no significant impact on health of mice,indicating good biocompatibility of Mg-Zn-Ca clip. |
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