Biodegradable magnesium alloy WE43 porous scaffolds fabricated by laser powder bed fusion for orthopedic applications:Process optimization,in vitro and in vivo investigation

Laser powder bed fusion(L-PBF)of magnesium(Mg)alloy porous scaffolds is expected to solve the dual challenges from customized structures and biodegradable functions required for repairing bone defects.However,one of the key technical difficulties lies in the poor L-PBF process performance of Mg,contributed by the high susceptibility to oxidation,vaporization,thermal expansion,and powder attachment etc.This work investigated the influence of L-PBF energy input and scanning strategy on the formation quality of porous scaffolds by using WE43 powder,and characterized the microstructure,mechanical properties,biocompatibility,biodegradation and osteogenic effect of the as-built WE43 porous scaffolds.With the customized energy input and scanning strategy,the relative density of struts reached over 99.5%,and the geometrical error between the designed and the fabricated porosity declined to below 10%.Massive secondary phases including intermetallic precipitates and oxides were observed.The compressive strength(4.37-23.49 MPa)and elastic modulus(154.40-873.02 MPa)were comparable to those of cancellous bone.Good biocompatibility was observed by in vitro cell viability and in vivo implantation.The biodegradation of as-built porous scaffolds promoted the osteogenic effect,but the structural integrity devastated after 12 h by the immersion tests in Hank’s solution and after 4 weeks by the implantation in rabbits’femur,indicating an excessively rapid degradation rate.