title: Ultraviolet radiation and nanoparticle induced intracellular free radicals generation measured in human keratinocytes by electron paramagnetic resonance spectroscopy.
abstract: BACKGROUND
  Several nanoparticle-based formulations used in cosmetics and dermatology are exposed to sunlight once applied to the skin. Therefore, it is important to study possible synergistic effects of nanoparticles and ultraviolet radiation.
  
  
  METHODS
  Electron paramagnetic resonance spectroscopy (EPR) was used to detect intracellular free radicals induced by ultraviolet B (UVB) radiation and amorphous silica nanoparticle and to evaluate the influence of nanoparticle surface chemistry on particle cytotoxicity toward HaCaT cells. Uncoated titanium dioxide nanoparticles served as positive control. In addition, particle intracellular uptake, viability, and induction of interleukin-6 were measured.
  
  
  RESULTS
  We found that photo-activated titanium dioxide particles induced a significant amount of intracellular free radicals. On the contrary, no intracellular free radicals were generated by the investigated silica nanoparticles in the dark as well as under UVB radiation. However, under UVB exposure, the non-functionalized silica nanoparticles altered the release of IL-6. At the same concentrations, the amino-functionalized silica nanoparticles had no influence on UVB-induced IL-6 release.
  
  
  CONCLUSIONS
  EPR spectroscopy is a useful technique to measure nanoparticle-induced intracellular free radicals. Non-toxic concentrations of silica particles enhanced the toxicity of UVB radiation. This synergistic effect was not mediated by particle-generated free radicals and correlated with particle surface charge and intracellular distribution.
authors.affiliation: Department of Dermatology and Allergy, Clinical Research Center for Hair and Skin Science, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Rancan
authors.forename: B
authors.initials: B
authors.lastname: Nazemi
authors.forename: S
authors.initials: S
authors.lastname: Rautenberg
authors.forename: M
authors.initials: M
authors.lastname: Ryll
authors.forename: S
authors.initials: S
authors.lastname: Hadam
authors.forename: Q
authors.initials: Q
authors.lastname: Gao
authors.forename: S
authors.initials: S
authors.lastname: Hackbarth
authors.forename: S F
authors.initials: SF
authors.lastname: Haag
authors.forename: C
authors.initials: C
authors.lastname: Graf
authors.forename: E
authors.initials: E
authors.lastname: Rühl
authors.forename: U
authors.initials: U
authors.lastname: Blume-Peytavi
authors.forename: J
authors.initials: J
authors.lastname: Lademann
authors.forename: A
authors.initials: A
authors.lastname: Vogt
authors.forename: M C
authors.initials: MC
authors.lastname: Meinke
mesh_terms: D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods*; D005609:Free Radicals / Q000378:metabolism*; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism*; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D053758:Nanoparticles / Q000633:toxicity* / Q000648:ultrastructure; D010316:Particle Size; D011829:Radiation Dosage; D012822:Silicon Dioxide / Q000633:toxicity*; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D005609:Free Radicals; D015850:Interleukin-6; D012822:Silicon Dioxide
keywords: IL-6; amorphous silica nanoparticles; surface functionalization; titanium dioxide nanoparticles