Fabrication of microporous coatings on titanium implants with improved mechanical, antibacterial and cell-interactive properties.

The success of an orthopedic implant therapy depends on successful bone integration and the prevention of microbial infections. In this work, plasma electrolytic oxidation (PEO) was performed to deposit TiO2 coatings enriched with Ca, P and Ag on titanium to improve its surface properties and antibacterial efficacy while maintaining normal biological functions and thus to enhance the performance of orthopedic implants. After PEO treatment, the surface of Ti was converted to anatase and rutile TiO2, hydroxyapatite and calcium titanate phases. The presence of these crystalline phases was further increased with an increased Ag content in the coatings. The developed coatings also exhibited a more porous morphology with an improved surface wettability, roughness, microhardness and frictional coefficient. In vitro antibacterial assays indicated that the Ag doped coatings can significantly prevent the growth of both Staphylococcus aureus and Escherichia coli by releasing Ag+ ions and the ability to prevent these bacteria was enhanced by increasing the Ag content in the coatings resulting in a maximal 6-log reduction of E. coli and a maximal 5-log reduction of S. aureus after 24 hours of incubation. Moreover, the in vitro cytocompatibility evaluation of the coatings exhibited that the osteoblast (MC3T3) cell integration on the PEO-based coatings were greatly improved compared to untreated Ti and no notable impact on their cytocompatibility was observed on increasing the amount of Ag in the coating. In conclusion, the coating with favorable physico-chemical and mechanical properties along with controlled silver ion release can offer an excellent antibacterial performance and osteocompatibility and can thus become a prospective coating strategy to face current challenges in orthopedics.