Development of bioactive and antibacterial surfaces is one of the goals for implantable surfaces. Infections, biofilm formation on the implants and bacterial resistance to antibiotics are still serious complications in dental and orthopaedic fields. In this research work, surfaces suitable to improve osseointegration and to reduce bacterial contamination have been investigated. This research is also aimed at defining characterization techniques suitable to compare a wide range of bioactive and antibacterial materials, because there is a high variability in the characterization techniques reported in literature.
The materials considered were a silica-based bioactive glass (SBA2) and a titanium alloy Ti6Al4V made bioactive and antibacterial with different chemical treatments. Silver was selected as antibacterial agent because it is a well-known broad spectrum antibacterial element, which limits the development of bacterial resistance. Regarding the glass samples, they were doped with Ag ions by means of an ion-exchange process in aqueous solutions, while two chemical treatments of the Ti6Al4V were compared. The first one allows to obtain a nano-textured topography enriched with hydroxyls groups and Ag nanoparticles, in situ reduced from a Ag precursor introduced at different steps of the chemical treatment. The second one, induces the formation of a surface layer with a nano-scale roughness, containing Sr (that is released in contact with solutions and it is able to increase osteoblast activity) and Ag-containing calcium titanate, rutile and anatase. Both the treated Ti6Al4V surfaces become negatively charged in a simulated body fluid and are able to form apatite, even if through different mechanisms, as well as to release Ag ions with antibacterial activity. Bioactivity kinetic was investigated up to 28 days by soaking samples in SBF solution. FESEM-EDS, XRD, FTIR, zeta-potential titration curves and XPS analyses were performed before and after SBF soaking. Moreover, ion release in SBF was monitored by means of ICP. The antibacterial properties were evaluated by means of the Kirby Bauer test and evaluation of biofilm and planktonic cells of Staphylococcus aureus showing the ability of the samples to inhibit biofilm production by bacteria. The antibacterial action and mechanism through silver nanoparticles vs ions is compared.
MAECI is acknowledged for supporting GLOBAL project within bilateral Italy-Japan joint research projects.