Controlled Delivery of Reactive Oxygen Species by Functionalized Catalytic Plasma Coatings for Antimicrobial Applications

Increasing complications due to bacterial and viral infections require novel antimicrobial approaches. One emerging strategy is that based on catalysts able to selectively deliver reactive oxygen species (ROS) without leaching of other substances. In particular, metal oxide thin films activated by daylight can produce ROS by simply catalyzing oxygen and water molecules. This study examines plasma technology, combining deposition and oxidation processes, as well as plasma polymerization, to obtain functionalized AgOx-doped titanium oxide (TiOx) catalytic materials. The high-energy conditions in the reactive, ionized gas enable the intrinsic formation of a large number of reactive sites at defects and interfaces between the metal oxide nanostructures. Furthermore, plasma functionalization with nanoporous SiOx films (up to 100 nm thick) allows to precisely control the ROS delivery as well as unravel ROS formation mechanism at the metal oxide interface. Combining fluorescence spectroscopy and electron paramagnetic resonance, the controlled delivery of superoxide anion and singlet oxygen has been tuned based on the thickness of the nanoporous functional layer. ROS delivery by functionalized catalytic plasma coating has been related to excellent antimicrobial activity against E. coli bacteria as well as murine hepatitis virus, while avoiding cytotoxic and sensitization effects.