Zirconia Reinforced Trace Element Co-doped Hydroxyapatite Coating

Zirconia is a kind of prospective hard tissue implant materials, which possesses superior mechanical properties and excellent biocompatibilities. To promote the stable osseointegration between Zirconia implants and tissue, zirconia-toughened trace Sr-, Si- and F- co-doped hydroxyapatite (ZrO2-DHA) was coated by plasma spraying on zirconia. The phase composition and structure of coatings were characterized, and the mechanical properties and in vitro biological properties were investigated. The results show that co-doping of trace Sr, Si and F enhances the biological properties of coatings on adhesion and differentiation of osteoblasts through the signal transduction pathway of osteogenic differentiation. All of ZrO2-DHA coatings promote the cell viability and gene expression in osteogenic differentiation of MC3T3-E1. On the 7th day of cell culture, the relative expression levels of Alp and Col-I in the ZrO2-DHA coating containing 70% DHA (7DHA) were about 2.8 times and 2.3 times higher than those in the ZrO2 substrate group, respectively. Mechanical properties of ZrO2-DHA coatings are improved with the increment of zirconia ratio. Hardness of DHA coating and 7DHA coating are 250.8 and 313.8HV respectively and their bond strength are 25.1 and 31.8 MPa, respectively. 7DHA coatings with network structure possess both excellent mechanical and biological performance for the implant coating application.