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      Broad-Spectrum Antimicrobial Effects of Photocatalysis Using Titanium Dioxide Nanoparticles Are Strongly Potentiated by Addition of Potassium Iodide


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          Photocatalysis describes the excitation of titanium dioxide nanoparticles (a wide-band gap semiconductor) by UVA light to produce reactive oxygen species (ROS) that can destroy many organic molecules. This photocatalysis process is used for environmental remediation, while antimicrobial photocatalysis can kill many classes of microorganisms and can be used to sterilize water and surfaces and possibly to treat infections. Here we show that addition of the nontoxic inorganic salt potassium iodide to TiO 2 (P25) excited by UVA potentiated the killing of Gram-positive bacteria, Gram-negative bacteria, and fungi by up to 6 logs. The microbial killing depended on the concentration of TiO 2, the fluence of UVA light, and the concentration of KI (the best effect was at 100 mM). There was formation of long-lived antimicrobial species (probably hypoiodite and iodine) in the reaction mixture (detected by adding bacteria after light), but short-lived antibacterial reactive species (bacteria present during light) produced more killing. Fluorescent probes for ROS (hydroxyl radical and singlet oxygen) were quenched by iodide. Tri-iodide (which has a peak at 350 nm and a blue product with starch) was produced by TiO 2-UVA-KI but was much reduced when methicillin-resistant Staphylococcus aureus (MRSA) cells were also present. The model tyrosine substrate N-acetyl tyrosine ethyl ester was iodinated in a light dose-dependent manner. We conclude that UVA-excited TiO 2 in the presence of iodide produces reactive iodine intermediates during illumination that kill microbial cells and long-lived oxidized iodine products that kill after light has ended.

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          Author and article information

          Antimicrob Agents Chemother
          Antimicrob. Agents Chemother
          Antimicrobial Agents and Chemotherapy
          American Society for Microbiology (1752 N St., N.W., Washington, DC )
          5 July 2016
          22 August 2016
          September 2016
          : 60
          : 9
          : 5445-5453
          [a ]Wellman Center for Photomedicine, Massachusetts General Hospital, Boston, Massachusetts, USA
          [b ]Department of Dermatology, Harvard Medical School, Boston, Massachusetts, USA
          [c ]Korean Advanced Institute of Science and Technology, Seoul, South Korea
          [d ]Graduate School of Pharmaceutical Science, University of Tokyo, Tokyo, Japan
          [e ]Center of Digital Dentistry, Peking University School and Hospital of Stomatology, Beijing, People's Republic of China
          [f ]Harvard-MIT Division of Health Sciences and Technology, Cambridge, Massachusetts, USA
          Author notes
          Address correspondence to Michael R. Hamblin, Hamblin@ 123456helix.mgh.harvard.edu .

          Citation Huang Y-Y, Choi H, Kushida Y, Bhayana B, Wang Y, Hamblin MR. 2016. Broad-spectrum antimicrobial effects of photocatalysis using titanium dioxide nanoparticles are strongly potentiated by addition of potassium iodide. Antimicrob Agents Chemother 60:5445–5453. doi: 10.1128/AAC.00980-16.

          Author information
          PMC4997851 PMC4997851 4997851 00980-16
          Copyright © 2016, American Society for Microbiology. All Rights Reserved.
          : 5 May 2016
          : 27 May 2016
          : 24 June 2016
          Page count
          Figures: 8, Tables: 0, Equations: 0, References: 41, Pages: 9, Words: 7419
          Funded by: HHS | NIH | National Institute of Allergy and Infectious Diseases (NIAID) http://dx.doi.org/10.13039/100000060
          Award ID: R01AI050875
          Award Recipient : Michael R. Hamblin
          Funded by: HHS | NIH | National Institute of Allergy and Infectious Diseases (NIAID) http://dx.doi.org/10.13039/100000060
          Award ID: R21AI121700
          Award Recipient : Michael R. Hamblin
          Funded by: National Science Foundation (NSF) http://dx.doi.org/10.13039/100000001
          Award ID: EEC-1358296
          Award Recipient : Hwanjun Choi Award Recipient : Yu Kushida
          Experimental Therapeutics


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