title: Penetration of titanium dioxide nanoparticles through slightly damaged skin in vitro and in vivo.
abstract: OBJECTIVE
  Titanium dioxide nanoparticles (TiO2-NPs) have been widely developed for versatile use, but the potential risk form their skin exposure is still unclear. To evaluate this risk, the skin penetration of TiO2-NPs is necessary to be understood first. The aims of this study are to investigated the penetration of TiO2-NPs through slightly damaged skin and intact skin in vitro and in vivo.
  
  
  METHODS
  TiO2-NPs with a diameter of 20 nm was labeled with 125I.The skin of rat was treated with 2% SLS solution and obtained as slightly damaged skin. The 125I labeled TiO2-NPs (125I-TiO2-NPs)solution and 0.9% PS solution were added into the donor chamber and receptor chamber of static diffusion cells which clamped the skin at the middle of two half-cells, respectively. During 24 hours, samples were extracted from the receptor chamber and counted for 1 min using γ-counter to detect the radioactivity. The skin penetration of TiO2-NPs in vitro was expressed as the percentage of radioactivity of receptor chamber solution compared with total radioactivity in the donor chamber. Thereafter, the 125I-TiO2-NPs was exposed to the rats. After 1 day and 3 days, the blood and tissues of rats were harvested, weighed and counted for 1 min using γ-counter to detect the tissue radioactivity. The skin penetration of TiO2-NPs in vivo was expressed as the percentage dose per gram tissue (% dose/g).
  
  
  RESULTS
  In the skin penetration experiment in vitro, the radioactivity of receptor chamber solution through damaged skin was higher than that of through intact skin and was about 2% radioactivity of donor chamber on 24 h. In the skin penetration experiment in vivo, the radioactivity of blood and tissues of rats after exposing to 125I-TiO2-NPs solution though damaged skin or intact skin were less than 0.05% dose/g on 1 d and quickly declined on 3 d. The skin penetration rates of TiO2-NPs through slightly damaged skin and intact skin in vitro and vivo were lower than the rate of free 125I in the TiO2-NPs solution.
  
  
  CONCLUSIONS
  The TiO2-NPs could not penetrate through the damaged skin or intact skin both in vitro and in vivo. It suggested that the TiO2-NPs should be safe when it was applied and contacted with skin.
authors.affiliation: Department of Stomatology, Shanghai East Hospital, Tongji University School of Medicine, Shanghai - China.
authors.forename: Guangping
authors.initials: G
authors.lastname: Xie
authors.affiliation: Department of Clinical Medicine, Medical School, Huzhou University, Huzhou - China.
authors.forename: Weixin
authors.initials: W
authors.lastname: Lu
authors.affiliation: Department of Clinical Medicine, Medical School, Huzhou University, Huzhou - China.
authors.forename: Dongmin
authors.initials: D
authors.lastname: Lu
mesh_terms: D000818:Animals; D007457:Iodine Radioisotopes / Q000737:chemistry / Q000378:metabolism; D008297:Male; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity* / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D012867:Skin / Q000187:drug effects* / Q000473:pathology; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry; D014025:Titanium / Q000737:chemistry*
chemical_list: D007457:Iodine Radioisotopes; C009495:titanium dioxide; D012967:Sodium Dodecyl Sulfate; D014025:Titanium