Visible light-induced antibacterial activity of metaloxide nanoparticles

Objective: The purpose of this article was to review studies that use visible light instead of dangerous ultraviolet (UV) radiation, for inducing antibacterial properties in metal oxide nanoparticles (NPs). Background data: Metal oxide NPs such as ZnO, CuO, and TiO₂ are frequently studied for their antibacterial effects, based on their capability to generate reactive oxygen species (ROS) in their water suspensions, following UV light absorption. Methods: Research articles on shifting metal oxide NPs absorption into the visible light region, published up to 2011, were retrieved from library sources, as well as PubMed and MEDLINE^® databases. Results: The studies indicated that doping metaloxide NPs with transition metals ions, or attaching the metal oxide nanoparticles to an organic molecule, enhanced their activity in the visible and near infrared (NIR) range. Moreover, ZnO and TiO₂ nanoparticles were found to have an absorption peak in UV-A, with a marked absorption in the blue region. Conclusions: It is possible to extend the absorption region of metal oxide NPs to the red/NIR, increasing their antibacterial activity without inducing damage to tissues and cells.