In vitro biodegradation and mechanical characteristics of a novel biliary stent made of magnesium alloy / 中国组织工程研究

ABSTRACT

BACKGROUND: Numerous evidence has demonstrated that the magnesium aloy with excelent mechanical properties can degradein vivo, and can be used as vascular stent materials, bone fixation materials, porous materials for bone repair. But it is not reported in the biliary stent. OBJECTIVE:To observe the degradation procedures and evaluate the changes of mechanical characteristics of biliary stents made of magnesium aloy (AZ 31B) in human bilein vitro. METHODS:The baloon-expandable biliary stents were made of magnesium aloy with laser sculpture. Then, 15 stents treated with micro-arc oxidation on the surface served as experimental group and another 15 stents without micro-arc oxidation as control group. A dynamic numerical simulation system was establishedin vitro to simulate the internal environment of human biliary tract. Al of the biliary stents were placed into this system. Their shapes were observed, and their qualities and radical forces were measured every 20 days. At the same time, their surfaces were scanned by scanning electron microscope. RESULTS AND CONCLUSION:(1) The degradation speeds of the stents in the experimental group were obviously slower than those in the control group. The fracture of the connecting rods in control group and experimental group appeared 20 days and 40 days later, respectively. The peak time of degradation in the control group and experimental group were 30 days and 50 days, respectively. The stents were fuly biodegraded within 70 days in the control group while within 90 days in the experimental group. With time, the stent surface became more rough, and the density, area and depth of etch pits were al increased in the two groups. At the same stage, the degradation speed of the control group was more rapid than that in the experimental group. (2) The qualities and radical forces of the stents were gradualy reduced with time in both groups. However, the degradation speed of stents in the experimental group was much slower than that in the control group. In summary, the degradation speed of the biliary stents made of magnesium aloy treated with micro-arc oxidation is appropriate and can meet the clinical requirement for the degradation time of biliary stents. This novel material could potentialy be used for the preparation of biliary stents.