Assessment of cobalt substitution on the structural, physico-mechanical, and in vitro degradation of akermanite ceramic

The effects of cobalt (Co) substitution on the structural, physico-mechanical properties, as well as the in vitro bioactivity and biodegradability of akermanite (Ca2MgSi2O7) are studied. The XRD patterns showed that the Co substitution did not change the Ca2MgSi2O7 phase. The FESEM micrographs revealed that the partial substitution of Co increased the shrinkage and density of Ca2MgSi2O7 and reduced the grain size. The Co substitution showing the highest mechanical response was 2 mol%. However, the mechanical properties decreased beyond 2 mol% due to the larger grain size. The in vitro degradation test showed that Co substitution altered the degradation profile of Ca2MgSi2O7. However, the degradation rate of Co-substituted Ca2MgSi2O7 was found to be low (1.2%) compared to that of Ca2MgSi2O7 (18%) and led to an alkaline microenvironment. Additionally, an in vitro bioactivity assessment supported the apatite-forming ability of Co-substituted Ca2MgSi2O7 disks after soaking in a SBF solution for 7 and 14 days. Finally, the concentration of Co2+ ions released from the 2 mol% disks was found to be in the non-toxic range. However, a further in vitro and in vivo test needs to be conducted.