title: Oxidative damage to nucleic acids photosensitized by titanium dioxide.
abstract: The semiconductor TiO2 is known to have photobiological activity in prokaryotic and eukaryotic cells. Applications of this photobiological activity have been suggested including sterilization of waste water and phototherapy of malignant cells. Here, several model and cellular systems were used to study the mechanism of photocatalysis by TiO2. Treatment of TiO2 (anatase, 0.45 microns), suspended in water containing a spin trap 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), with UV radiation (320 nm) resulted in an electron spin resonance (ESR) signal characteristic of the hydroxyl radical. Irradiation of solutions containing calf thymus DNA and TiO2 with UVA (320-400 nm) radiation resulted in hydroxylation of guanine bases. The degree of hydroxylation was dependent on both UVA fluence and amount of TiO2 in suspension. Human skin fibroblasts, preincubated 18 h with 10 micrograms/cm2 TiO2 and then UVA-irradiated (0-58 KJ/m2), showed dose dependent photocytoxicity. RNA, isolated from similarly treated fibroblasts, contained significant levels of photooxidation, measured as hydroxylation of guanine bases. However, no oxidative damage was detectable in cellular DNA. These results suggest that nucleic acids are a potential target for photooxidative damage sensitized by TiO2, and support the view that TiO2 photocatalyzes free radical formation.
authors.affiliation: Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Washington, DC 20204, USA. WGW@FDACF.SSW.DHHS.GOV
authors.forename: W G
authors.initials: WG
authors.lastname: Wamer
authors.forename: J J
authors.initials: JJ
authors.lastname: Yin
authors.forename: R R
authors.initials: RR
authors.lastname: Wei
mesh_terms: D000818:Animals; D002417:Cattle; D002460:Cell Line; D003497:Cyclic N-Oxides; D004247:DNA / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D003848:Deoxyguanine Nucleotides / Q000378:metabolism / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004578:Electron Spin Resonance Spectroscopy; D005347:Fibroblasts / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D009696:Nucleic Acids / Q000187:drug effects* / Q000528:radiation effects; D018384:Oxidative Stress / Q000187:drug effects* / Q000528:radiation effects; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000528:radiation effects / Q000633:toxicity*; D012313:RNA / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D012867:Skin; D013113:Spin Labels; D013535:Suspensions; D014025:Titanium / Q000528:radiation effects / Q000633:toxicity*; D014466:Ultraviolet Rays
chemical_list: D003497:Cyclic N-Oxides; D003848:Deoxyguanine Nucleotides; D009696:Nucleic Acids; D017319:Photosensitizing Agents; D013113:Spin Labels; D013535:Suspensions; C078206:8-oxodeoxyguanosine triphosphate; C009495:titanium dioxide; D012313:RNA; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D004247:DNA; D014025:Titanium