title: Broad-spectrum antimicrobial photocatalysis mediated by titanium dioxide and UVA is potentiated by addition of bromide ion via formation of hypobromite.
abstract: Antimicrobial photocatalysis involves the UVA excitation of titanium dioxide (TiO2) nanoparticles (particularly the anatase form) to produce reactive oxygen species (ROS) that kill microbial cells. For the first time we report that the addition of sodium bromide to photoactivated TiO2 (P25) potentiates the killing of Gram-positive, Gram-negative bacteria and fungi by up to three logs. The potentiation increased with increasing bromide concentration in the range of 0-10mM. The mechanism of potentiation is probably due to generation of both short and long-lived oxidized bromine species including hypobromite as shown by the following observations. There is some antimicrobial activity remaining in solution after switching off the light, that lasts for 30min but not 2h, and oxidizes 3,3',5,5'-tetramethylbenzidine. N-acetyl tyrosine ethyl ester was brominated in a light dose-dependent manner, however no bromine or tribromide ion could be detected by spectrophotometry or LC-MS. The mechanism appears to have elements in common with the antimicrobial system (myeloperoxidase+hydrogen peroxide+bromide).
authors.affiliation: Department of Emergency, First Affiliated College & Hospital, Guangxi Medical University, Nanning 530021, China; Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Dermatology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Ximing
authors.initials: X
authors.lastname: Wu
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Dermatology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Ying-Ying
authors.initials: YY
authors.lastname: Huang
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA 02114, USA; Graduate School of Pharmaceutical Science, University of Tokyo, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Kushida
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Dermatology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Brijesh
authors.initials: B
authors.lastname: Bhayana
authors.affiliation: Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, MA 02114, USA; Department of Dermatology, Harvard Medical School, Boston, MA 02115, USA; Harvard-MIT Division of Health Sciences and Technology, Cambridge, MA 02139, USA. Electronic address: hamblin@helix.mgh.harvard.edu.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hamblin
mesh_terms: D000890:Anti-Infective Agents / Q000378:metabolism; D001419:Bacteria / Q000187:drug effects / Q000528:radiation effects; D001965:Bromides / Q000737:chemistry / Q000378:metabolism*; D005658:Fungi / Q000187:drug effects / Q000528:radiation effects; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism; D008027:Light; D053768:Metal Nanoparticles / Q000737:chemistry; D010084:Oxidation-Reduction / Q000528:radiation effects*; D017382:Reactive Oxygen Species / Q000378:metabolism* / Q000528:radiation effects; D017670:Sodium Compounds / Q000737:chemistry / Q000378:metabolism*; D014025:Titanium / Q000737:chemistry / Q000378:metabolism*; D014466:Ultraviolet Rays
chemical_list: D000890:Anti-Infective Agents; D001965:Bromides; D017382:Reactive Oxygen Species; D017670:Sodium Compounds; C009495:titanium dioxide; D006861:Hydrogen Peroxide; D014025:Titanium; C027938:sodium bromide
keywords: Antimicrobial photocatalysis; Bacteria; Hypobromite; Reactive oxygen species; Sodium bromide; Titanium dioxide; Ultraviolet A