Bioactivity and cytocompatibility of zirconia (ZrO2) films fabricated by cathodic arc deposition

Zirconium oxide thin films were fabricated on silicon wafers using a filtered cathodic arc system in concert with oxygen plasma. The structure and phase composition of the zirconium oxide thin films were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), and transmission electron microscopy (TEM). The bioactivity was assessed by investigating the formation of apatite on the film surface after soaking in simulated body fluids. Bone marrow mesenchymal stem cells (BMMSC) were used to further evaluate the cytocompatibility of the materials. The results indicate that the films are composed of stoichiometric ZrO2 and the composition is quite uniform throughout the thickness. Bone-like apatite can be formed on the surface of the ZrO2 thin film in our SBF immersion experiments, suggesting that the surface is bioactive. The outermost layer of the ZrO2 thin film comprises nano-sized particles that can be identified by AFM images taken on the thin film surface and TEM micrographs obtained from the interface between the ZrO2 thin film and apatite layer. The nanostructured surface is believed to be the key factor that apatite is induced to precipitate on the surface. Bone marrow mesenchymal stem cells are observed to grow and proliferate in good states on the film surface. Our results show that ZrO2 thin films fabricated by cathodic arc deposition exhibit favorable bioactivity and cytocompatibility.