title: In vitro antibacterial properties and UV induced response from Staphylococcus epidermidis on Ag/Ti oxide thin films.
abstract: Implanted materials are susceptible to bacterial colonization and biofilm formation, which can result in severe infection and lost implant function. UV induced photocatalytic disinfection on TiO2 and release of Ag(+) ions are two promising strategies to combat such events, and can be combined for improved efficiency. In the current study, a combinatorial physical vapor deposition technique was utilized to construct a gradient coating between Ag and Ti oxide, and the coating was evaluated for antibacterial properties in darkness and under UV light against Staphylococcus epidermidis. The findings revealed a potent antibacterial effect in darkness due to Ag(+) release, with near full elimination (97%) of viable bacteria and visible cell lysis on Ag dominated surfaces. The photocatalytic activity, however, was demonstrated poor due to low TiO2 crystallinity, and UV light irradiation of the coating did not contribute to the antibacterial effect. On the contrary, bacterial viability was in several instances higher after UV illumination, proposing a UV induced SOS response from the bacteria that limited the reduction rate during Ag(+) exposure. Such secondary effects should thus be considered in the development of multifunctional coatings that rely on UV activation.
authors.affiliation: Division of Applied Materials Science, Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, Box 534, 751 21, Uppsala, Sweden. unosson.erik@gmail.com.
authors.forename: Erik
authors.initials: E
authors.lastname: Unosson
authors.affiliation: Division of Applied Materials Science, Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, Box 534, 751 21, Uppsala, Sweden.
authors.forename: Matthias
authors.initials: M
authors.lastname: Morgenstern
authors.affiliation: Division of Applied Materials Science, Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, Box 534, 751 21, Uppsala, Sweden.
authors.forename: Håkan
authors.initials: H
authors.lastname: Engqvist
authors.affiliation: Division of Nanotechnology and Functional Materials, Department of Engineering Sciences, The Ångström Laboratory, Uppsala University, Box 534, 751 21, Uppsala, Sweden.
authors.forename: Ken
authors.initials: K
authors.lastname: Welch
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D018441:Biofilms; D008422:Materials Testing; D008567:Membranes, Artificial; D012834:Silver / Q000737:chemistry*; D013212:Staphylococcus epidermidis / Q000187:drug effects* / Q000528:radiation effects* / Q000648:ultrastructure; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D000900:Anti-Bacterial Agents; D008567:Membranes, Artificial; C009495:titanium dioxide; D012834:Silver; D014025:Titanium