In vitro properties of bioceramic coatings produced on zirconium by plasma electrolytic oxidation

The bioceramic coatings were formed on zirconium (Zr) at different treatment times such as 5, 10 and 15 min in a calcium acetate and β-calcium glycerophosphate-based electrolyte by a single-step plasma electrolytic oxidation (PEO). The XRD and FTIR confirmed a presence of highly crystalline cubic-ZrO2, perovskite-CaZrO3 and HAP on the surface of Zr. The surface of the coatings was porous and rough due to the existence of micro-sparks through the PEO process. The surface of the coatings produced at long treatment times exhibited a hydrophilic surface compared to the uncoated Zr substrate. The elements of Ca, P and O were homogeneously distributed through on the coated surface. The amount of secondary apatite formed on coated surface after immersion in simulated body fluid (SBF) up to 28 days increased with increasing time. The bioactivity of the coatings was greater than that of the uncoated Zr. The bacterial adhesion to the coated surface decreased considerably compared to the uncoated Zr. MTT analysis showed that a cell viability, a cell attachment and a cell growth for PEO coatings were greater than for the uncoated Zr. As a result, the biological test results show that PEO coatings with different treatment time improve the biocompatibility of the surfaces.