Effect on growth and osteoblast mineralization of hydroxyapatite-zirconia (HA-ZrO2) obtained by a new low temperature system

Ceramics and bioceramics, as hydroxyapatite and zirconium, are used in bone tissue engineering. Hydroxyapatite has chemical properties similar to the bone while zirconium offers suitable mechanical properties. The aim of this article is to evaluate the ability to support cellular growth and osteoblastic mineralization of hydroxyapatite-zirconium obtained by a new system based on different low temperatures, as 873°K (HZ600), 923°K (HZ650) and 973°K (HZ700). Hydroxyapatite-zirconia obtained by this new system was examined in terms of thermogravimetric features and X-ray diffractograms. Furthermore, the ability for supporting osteoblast growth and mineralization were analyzed. By x-ray diffraction analysis, we clearly demonstrated that no high-temperature processing was required. Moreover, it is possible to form tetragonal-zirconium at 650°C. Proliferation assay showed that osteoblast growth was not influenced by any of the composite evaluated. Regarding osteogenic marker Col1, a 2 fold increase in expression was observed for HZ650 compared to HZ600 and HZ700. Interestingly, osteoblasts grown on HZ650 showed globular accretions covered with collagen bundles and calcium-rich extracellular matrix whereas HZ600 and HZ700 showed no phosphate or calcium deposits. This study demonstrated that at 650°C is possible to generate stable tetragonal-zirconium and the resulting HZ650 composite is able to promote a suitable osteoblast mineralization process.