Surface modification of titanium surfaces through a modified oxide layer and embedded silver nanoparticles: Effect of reducing/stabilizing agents on precipitation and properties of the nanoparticles

The final goal of this research is to produce a modified titanium surface simultaneously able to induce bone tissue integration in the case of critical bone quality and/or quantity (elderly population) and to prevent infections at the implant site and around it. A metallic antibacterial agent is used against bacteria colonization and biofilm formation, in agreement with the well-established strategy to reduce the use of antibiotics. A surface treatment able to induce the formation of a chemically modified and nanotextured surface oxide layer (with several functionalities suitable for fast and effective osseointegration), as well as the nucleation of silver nanoparticles on the surface was developed. The present paper aims to optimize the chemical process for the preparation of the modified surfaces. This paper describes the selection and dose of the required additives, such as reducing agents and nanoparticle stabilizers, in order to achieve a good control of the series of chemical reactions concurrently occurring during the surface chemical treatment. Surface topography (oxide nanotexture and nanoparticle precipitation) was investigated by means of Field Emission Scanning Electron Microscopy (FESEM) equipped with Energy Dispersive Spectroscopy (EDS) for semi-quantitative evaluation of the chemical composition. Silver release was measured in ultrapure water through a photometric method and surface ability to induce in vitro apatite precipitation was investigated by soaking in Simulated Body Fluid (SBF) followed by FESEM-EDS observations. Finally, a preliminary test of antibacterial activity of the modified titanium surfaces was carried out by means of both inhibition halo and adhesion assays against Staphylococcus aureus.