Preparation, solubility, and cytocompatibility of zinc-releasing calcium phosphate ceramics

Zinc is an essential trace element with stimulatory effects on bone formati on. Therefore, zinc was doped into beta-tricalcium phosphate to develop zin c-releasing biomaterials to promote bone formation. The zinc-doped beta-tri calcium phosphate, beta-tricalcium phosphate, and hydroxyapatite powders we re mixed at a (Ca+Zn)/P molar ratio of 1.60, followed by sintering into a d ense body at 1100 degrees C for 1 h. The sintered body was a composite cera mic consisting of zinc-doped beta-tricalcium phosphate and hydroxyapatite p hases. The composite ceramic contained zinc oxide when the zinc content was higher than 1.20 wt %. The composite ceramic released zinc under pseudophy siological conditions. However, the release of calcium and phosphate decrea sed with an increase in zinc content in a range higher than 0.12 wt t % owi ng to a decrease in solubility of the zinc-doped beta-tricalcium phosphate phase. Proliferation of osteoblastic MC3T3-E1 cells was significantly incre ased on the composite ceramic with a zinc content from 0.6 to 1.20 wt %, co mpared with those without zinc. When the zinc content was higher than 1.20 wt %, release of zinc from the zinc oxide caused cytotoxicity. Therefore, t he zinc content of the composite ceramic must be <1.20 wt %. (C) 2000 John Wiley & Sons, Inc.