Effect of Ag and Cu doping on the properties of ZnO magnetron sputtered thin films for biomedical applications

Hospital-acquired infections are a major challenge for the healthcare system. The development of antibacterial surfaces for medical devices and non-critical surfaces in healthcare facilities is gaining attention as a promising strategy to prevent them. In this study, the properties of biodegradable magnetron-sputtered ZnO thin films doped with Ag and Cu were compared. In addition, biomimetic deposition of calcium phosphates (CaPs) on these surfaces was explored. The investigated thin films doped were prepared by co-deposition in a multi-source magnetron sputtering system. X-ray diffraction of the prepared thin films revealed the formation of wurtzite in all cases. Grazing incidence small-angle X-ray scattering showed the formation of nanoparticles whose lateral-to-vertical diameter decreased with increasing Ag content and increased with increasing Cu content. The opposite influence of increasing Ag and Cu content in the thin films on grain size and water contact angle were also observed. The biomimetic deposition of calcium phosphates (CaP) resulted in partial coverage of the surface of all thin films investigated with apatitic phase. CaP deposition resulted in a reduced WCA as well as a slightly reduced release of Cu and an increased release of Ag ions, while the release of Zn remained unaffected. Even though the tested surfaces exhibited cytotoxicity, CaP deposition enhanced MG-63 cell viability, especially for Ag-doped ZnO thin films, and improved the prevention of S. aureus and P. aeruginosa biofilm formation. The results confirmed the potential of magnetron sputtering to coat materials for biomedical antibacterial applications and pointed to a viable strategy for preparing biocompatible surfaces.