A Research On Preparation And Properties Of Magnesium Alloys Scaffolds For Bone Repairing

In recent years,the magnesium alloy has been regarded as a potential scaffold material for bone tissue engineering(BTE)due to its excellent biodegradability,biocompatibility and suitable mechanical property similar to the human bone.However,it is difficult to meet the high porosity and ideal mechanical properties at the same time for magnesium alloy scaffolds fabrication,and the corrosion rate of magnesium scaffolds will be accelerated due to the larger specific surface area,which greatly hinders the application of the porous magnesium alloy as BTE scaffolds in the future.In response to the problems above,this research prepares porous magnesium alloys(Mg-1.5Zn-0.2Ca)scaffolds with different porous structures,using spherical and square Na Cl templates for pore-making by negative pressure infiltration casting,to discuss the effects of different pore shapes on the porous structure and compressive mechanical properties of magnesium alloy scaffolds.The degradation behavior and antibacterial performance of the porous magnesium alloy scaffolds were also evaluated based on different surface treatments.Due to the results of this research,it could provide necessary data support and theoretical guidance for the application of porous magnesium alloy scaffolds in BTE.The main findings of this article are as follows:(1)The magnesium alloy scaffolds with spherical pores,50%square pores and 50%spherical pores were separately fabricated by the negative pressure infiltration casting method.The porous structure and compressive mechanical property of the two kinds of scaffolds fulfill the requirements of the BTE's clinical application.The porosity of the magnesium alloy scaffold with spherical pores is 74.97%,the specific surface area is 8.36mm²/mm³,the size of main pore is 450?600?m,the size of connected pore is 150?200?m,the compressive yield strength is 4.035MPa,and the compressive elastic modulus is 0.229GPa;while the porosity of the magnesium alloy scaffold with 50%square pores and 50%spherical pores is 68.60%,the specific surface area is 8.09mm²/mm³,the size of main pore is 450?600?m,the size of connecting pore is 36?260?m,the compressive yield strength is 4.22MPa,and the compressive elastic modulus is 0.318GPa.The two kinds of scaffolds match highly with human cancellous bone in terms of structure.In addition,the permeability simulation results show that magnesium alloy scaffolds with spherical pores have a higher degree of opening.(2)The two kinds of porous magnesium alloy scaffolds were completely degraded in 50hours.The magnesium alloy scaffolds were separately treated with Mg F₂,fluoapatite and phytin,by which all the scaffolds'resistance were improved greatly.All scaffolds treated with Mg F₂ or fluoapatite still perform well after 300 hours'immersion,with little degradation products on the surface,while part of the scaffolds treated with phytin dissolved at the edge with the pores blocked up with degradation products.The corrosion resistance of scaffolds with spherical pores is slightly weaker than that of scaffolds with 50%square pores for the larger specific surface area.(3)The antibacterial test results show that all scaffolds'antibacterial rate improves with time,and the scaffolds with Mg F₂ have a weaker antibacterial performance until extracting for72h while other scaffolds'antibacterial rate reach quickly to 90%in 24h.