Three-dimensional printing akermanite porous scaffolds for load-bearing bone defect repair: An investigation of osteogenic capability and mechanical evolution

Some Ca-Mg-silicate ceramics have been widely investigated to be highly bioactive and biodegradable, whereas their osteogenic potential and especially biomechanical response in the early stage in vivo are scarcely demonstrated. Herein, the osteogenesis capacity and mechanical evolution of the akermanite (Ca2MgSi2O7) porous materials manufactured by ceramic ink writing three-dimensional printing technique were investigated systematically in a critical size femur defect model, in comparison with the clinically available -tricalcium phosphate porous bioceramic. Such three-dimensional printed akermanite scaffolds possess fully interconnected pores of approximate to 280x280 mu m in size and over 50% porosity with appreciable compressive strength (approximate to 71MPa), that is 7-fold higher than that of the -tricalcium phosphate porous bioceramics (approximate to 10MPa). After 6 weeks and 12 weeks of implantation, the percentage of newly formed bone and more new bone was observed in the akermanite group as compared with the -tricalcium phosphate group (p<0.01). Moreover, significant higher mRNA expressions of osteogenic genes were detected in the akermanite group by PCR analysis (p<0.01). The in vivo mechanical strength decreased during the process of implantation, but maintained a relative high level (approximate to 14MPa) which was still higher than that of the host cancellous bone (5-10MPa) at 12 weeks post-implantation. On the contrary, the -tricalcium phosphate scaffold always exhibited a very low mechanical strength (approximate to 8MPa). These results suggest that the three-dimensional printed akermanite scaffolds are promising for the bone tissue regeneration and repair of load-bearing bone defects.