Hydrolysis and cytocompatibility of zinc-containing α-tricalcium phosphate powder

Zinc is an essential trace element with stimulatory effects on bone formation in vitro and in vivo. In order to apply zinc-containing α-tricalcium phosphate (αZnTCP) to αTCP-based calcium phosphate cement, αZnTCP powders containing various amounts of zinc were prepared and the optimum zinc content was examined from the viewpoints of hydrolysis property and cytocompatibility. Single-phase αZnTCP containing zinc from 0.00 to 1.26 wt.% was obtained by heating zinc-containing β-tricalcium phosphate at 1450 °C. At a zinc content of 0.11 wt.%, there was no significant difference in the amount of calcium-deficient low-crystalline apatite formed by hydrolysis between pure αTCP and αZnTCP. The hydrolysis of αZnTCP was significantly retarded by incorporating zinc at or more than 0.26 wt.% due to the inhibitory effect of zinc on the crystal growth of apatite. The MC3T3-E1 cell densities cultured with pure αTCP and 0.11 Zn wt.% αZnTCP powders showed no significant difference in the range of powder dose from 10 to 1000 μg mL−1. The result indicated that the cytocompatibility of pure αTCP powder was comparable to that of αZnTCP at the zinc content of 0.11 wt.%. Therefore, the optimum zinc content of αZnTCP powder is less than 0.26 wt.%, and preferably at or less than 0.11 wt.% to apply to an αTCP-based calcium phosphate cement.