An in-vitro study: The effect of surface properties on bioactivity of the oxide layer fabricated on Zr substrate by PEO

Surface properties can affect cell attachment and growth ability on the biomaterials. In this work, the effect of the morphology and chemical composition of the surface coatings synthesized on zirconium (Zr) substrates on bioactivity was studied. The surface of pure Zr was modified via a plasma electrolytic oxidation process to obtain oxide-based coatings with different surface chemical compositions and pore sizes by changing the process parameters in the same electrolyte. The characterization of the coatings was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle goniometry (CAG) and energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). The results showed that the coatings comprised t-ZrO₂ and Ca_0.134Zr_0.86O_1.86 phases. During the oxidation of Zr substrates, applying an anode current with different densities and frequencies altered the surface roughness Ra of the samples. The relationship between the surface morphology, chemical composition, and bioproperties was investigated by simulated body fluid (SBF) and cell culture tests. The coated samples were immersed into SBF solution and the formation of hydroxyapatite (HA) structure on the surface was detected after 7 days of immersion. A close relationship between the development of HA, the size of the porosity and chemical composition of the coating surface was observed. Additionally, the cell attachment and cell growth on the surface were found to be dependent on the chemistry and topography of coated surfaces. The cell culture test revealed that the growth of the cells was improved with increasing pore sizes on the coating surface.