title: Protein Corona Prevents TiO2 Phototoxicity.
abstract: OBJECTIVE
  TiO2 nanoparticles have generally low toxicity in the in vitro systems although some toxicity is expected to originate in the TiO2-associated photo-generated radical production, which can however be modulated by the radical trapping ability of the serum proteins. To explore the role of serum proteins in the phototoxicity of the TiO2 nanoparticles we measure viability of the exposed cells depending on the nanoparticle and serum protein concentrations.
  
  
  RESULTS
  Fluorescence and spin trapping EPR spectroscopy reveal that the ratio between the nanoparticle and protein concentrations determines the amount of the nanoparticles' surface which is not covered by the serum proteins and is proportional to the amount of photo-induced radicals. Phototoxicity thus becomes substantial only at the protein concentration being too low to completely coat the nanotubes' surface.
  
  
  CONCLUSIONS
  These results imply that TiO2 nanoparticles should be applied with ligands such as proteins when phototoxic effects are not desired - for example in cosmetics industry. On the other hand, the nanoparticles should be used in serum free medium or any other ligand free medium, when phototoxic effects are desired - as for efficient photodynamic cancer therapy.
authors.affiliation: Jožef Stefan Institute, Ljubljana, Slovenia; Jožef Stefan International Postgraduate School, Ljubljana, Slovenia.
authors.forename: Maja
authors.initials: M
authors.lastname: Garvas
authors.affiliation: NAMASTE Center of Excellence, Ljubljana, Slovenia.
authors.forename: Anze
authors.initials: A
authors.lastname: Testen
authors.affiliation: Jožef Stefan Institute, Ljubljana, Slovenia; NAMASTE Center of Excellence, Ljubljana, Slovenia.
authors.forename: Polona
authors.initials: P
authors.lastname: Umek
authors.affiliation: Laboratoire de Physique des Solides, Université Paris Sud, CNRS UMR 8502, F-91405, Orsay, France.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Gloter
authors.affiliation: Jožef Stefan Institute, Ljubljana, Slovenia; NAMASTE Center of Excellence, Ljubljana, Slovenia.
authors.forename: Tilen
authors.initials: T
authors.lastname: Koklic
authors.affiliation: Jožef Stefan Institute, Ljubljana, Slovenia; NAMASTE Center of Excellence, Ljubljana, Slovenia.
authors.forename: Janez
authors.initials: J
authors.lastname: Strancar
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000378:metabolism; D002417:Cattle; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006801:Humans; D053758:Nanoparticles / Q000378:metabolism / Q000633:toxicity* / Q000648:ultrastructure; D055668:Photochemical Processes; D000066970:Protein Corona / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014025:Titanium / Q000378:metabolism / Q000633:toxicity*; D014466:Ultraviolet Rays
chemical_list: D001798:Blood Proteins; D000066970:Protein Corona; D017382:Reactive Oxygen Species; C009495:titanium dioxide; D014025:Titanium