Grain boundary corrosion in TiO2 bone scaffolds doped with group II cations

A pH drop during the inflammatory phase during bone regeneration can cause corrosion in TiO2 bone scaffolds and the loss of compressive strength. Corrosion as ion leaching and dissolution is confined to grain boundaries. Cationic doping of TiO2 showed to increase the compressive strength but increased the amount of impurities in grain boundaries as well. Therefore, this study showed the different grain boundary formation for Ca, Sr and Mg doped scaffolds and their corrosion behavior. After corrosion, the amorphous phase in grain boundaries was dissolved in all doped scaffolds. Differences occurred due to the formation of an additional crystalline phase in Sr doped scaffolds. The presence of an amorphous and crystalline phase led to an inhomogeneous dissolution in grain boundaries and a significant decrease in compressive strength already after 4 h in contact with an acidic environment. Released ions did not show any cytotoxic effect on hASCs. Mg doped TiO2 scaffolds led to significant increased osteogenic differentiation.