Zn doped β-tricalcium phosphate addition into apatite cement further enhance the differentiation of osteoblasts

Apatite cement (AC) set to form apatite and thus shows good osteoconductivity. We have previously reported that AC enhanced the differentiation of osteoblastic cells when compared with sintered apatite. We also reported that proliferation of the osteoblastic cells on the surface of apatite cement (AC) can be further enhanced by adding 5% Zn doped TCP (ZnTCP) in the AC. In the present investigation, effects of ZnTCP addition into AC on osteoconductivity were studied with respect to the differentiation of osteoblastic cells. Osteoblastic cells were incubated on the surface of AC containing various amount of ZnTCP, and type I collagen production (PICP), ALP activity and osteocalcin production were measured as an indexes of the differentiation of osteoblastic cells at initial, mid-term and late-term period. We found AC containing 5% ZnTCP showed higher PICP value than ZnTCP free AC. However, AC containing 10% ZnTCP showed lower PICP value than ZnTCP free AC. The effects were smaller with respect to ALP and nothing with respect to osteocalcin production. We concluded, therefore, that addition of ZnTCP has a good potential value to enhance the osteoconductivity of AC if we can regulate the release of Zn ion from ZnTCP.