Characterization and investigation of in vitro properties of antibacterial copper deposited on bioactive ZrO2 coatings on zirconium

Highlights: • The copper (Cu)-based ZrO₂/CaZrO₃ bioceramic surfaces were fabricated on zirconium. • The Cu/ZrO₂/CaZrO₃ exhibited superhydrophobic character to plain bioceramic surface. • The apatite on the Cu/ZrO₂/CaZrO₃ was more homogeneous to plain bioceramic surface. • Bioactivity of the Cu/ZrO₂/CaZrO₃ was improved respect to plain bioceramic coatings. • Microbial adhesion of the Cu/ZrO₂/CaZrO₃ was reduced to plain bioceramic coatings. -- Abstract: In this study, porous and rough bioceramic structures were coated on commercial pure Zr by PEO (plasma electrolytic oxidation). Then, Cu was deposited onto the PEO surfaces without any morphological changing by TE (thermal evaporation). Mainly, meta-stable Ca_0.15Zr_0.85O_1.85 (calcium zirconium oxide), cubic-ZrO₂ (zirconia) and perovskite-CaZrO₃ (calcium zirconate) were observed on the surfaces by powder-XRD (powder X-ray diffraction) and TF-XRD (thin film XRD) analyses as the phases of Zr and Cu₂(P₂O₇) (copper pyrophosphate) were detected as a trace amount on the Cu-deposited PEO surface. The average thicknesses of the PEO coating and TE layer were measured as approximately 21.8 ± 2.4 μm and 20 nm, respectively. The Cu-deposited PEO surfaces indicated superhydrophobic character while the PEO surface exhibited hydrophilic behavior. The apatite-forming abilities on both coatings were evaluated by surface and cross-sectional SEM (scanning electron microscopy) and surface EDS (energy dispersive X-ray spectroscopy)-mapping analyses at post-soaking in SBF (simulated body fluid) up to 10 days. However, apatite formed on the Cu-deposited PEO surfaces was thicker and more homogenous than the PEO surface. Thus, in vitro bioactivity was considerably improved by Cu-deposition on the PEO. In vitro microbial adhesion test of both surfaces was investigated by bacterial adhesions for Gram positive and Gram negative bacteria. The bacterial adhesions on the Cu-deposited PEO surfaces were lower compared to the PEO surfaces for all bacteria types.