Development and characterization of anti-bacterial and corrosion resistance surface treatments on medical grade Ti grade 2 and Ti grade 5

Titanium alloys are widely used materials in orthopedic implants due to their superior mechanical and chemical compatibility, and their ability to osseointegrate in host bone, when compared with other commonly used alloys, namely, 316 L stainless steel and Co-Cr alloys. Nevertheless, these materials still face several challenges, and the focus of development has progressively shifted to an even more improved biocompatibility, in terms of bioactivity, reduced toxicity and fast osteointegration, as well as a decreased susceptibility to microbial colonization. In this aspect, infection around titanium implants continues to be a concern in the medical field. Implants provide niche environments, with decreased host-defenses where microorganisms such as bacteria can adhere and form biofilms, sessile communities that protect these microorganisms from the action of antibiotics or the host immune system, allowing them to replicate and propagate into various locations in the human body. Thus, the occurrence of infection results in the necessity of further antibiotic therapy and eventual removal of the device, with an increased hospitalization time and healthcare cost, posing a threat to the patient’s life. In this aspect, surface modification of Titanium-based alloys through the production TiO2 nanotubes on their surface, has been widely regarded both as surface treatment that provides it with an increased bioactivity, but also as reservoirs and carriers for local delivery of antimicrobial agents. In this work, production of TiO2 nanotubes on the surface of the most common medical grade titanium alloys, Cp-Ti and Ti6Al4V has been achieved through electrochemical anodization. It was shown that, by successfully controlling specific process parameters, namely, electrolyte composition, applied potential difference and process time, well-defined nanotubular structures with target inner diameters of 70-100 nm can be obtained on both alloys. Moreover, post-anodizing heat treatments were preformed that successfully converted the produced amorphous anodic oxide into a crystalline anatase phase, which confers to these nanotubular structures an increased stability. This surface treatments were evaluated in terms of corrosion resistance through potentiodynamic polarization measurements and have been shown to lead to an overall improve of the corrosion resistance in the potential range of the human body. Lastly, when decorated, through electroless and electrochemical deposition processes, with inorganic antimicrobial agents (Ag,Cu and Zn) they have been shown to drastically decrease the viability of one of the most common implant infections pathogens, Staphilococcus edpidermidis.