Crystalline phase modulates the potency of nanometric TiO₂ to adhere to and perturb the stratum corneum of porcine skin under indoor light

Chem Res Toxicol. 2013 Oct 21;26(10):1579-90. doi: 10.1021/tx400285j. Epub 2013 Sep 27.

Abstract

Nanometric TiO₂ is largely employed in cosmetics, but in vitro toxic effects have been reported when nano-TiO₂ is exposed to UV light. The photoreactivity of TiO₂ largely depends on its crystal phase, namely, anatase and rutile. Surface acidity, which is also dependent on crystal structure, may impart a positive or negative charge to the nanomaterial surface and ultimately modulate particle adhesion to tissues. Three nanometric TiO₂ powders with a different crystal lattice and surface charge (anatase, rutile, and anatase/rutile) have been employed here to investigate their interaction with the skin and to examine the molecular mechanisms of the TiO₂-induced oxidative damage. The strength of the interaction of nano-TiO₂ with skin has been revealed by chemiometric mapping (μ-XRF and SEM-EDS) after tissue washing. Positively charged anatase and anatase/rutile, but not negatively charged rutile, were strongly held on the skin surface and were able to promote a structural rearrangement of the lipid bilayer in the stratum corneum (DSC and Raman) under controlled indoor illumination (UVA < 1 mW/m²). Under the same conditions, cell-free reactivity tests (ROS-mediated free-radical release and lipoperoxidation) indicated that anatase and anatase/rutile are more reactive than rutile, suggesting a ROS-mediated oxidative mechanism that may alter the structure of the stratum corneum. Both the higher oxidative potential and the stronger adhesion to skin of anatase and anatase/rutile TiO₂ may explain the stronger disorganization induced by these two samples and suggests the use of rutile to produce safer TiO₂-based cosmetic and pharmaceutical products.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calorimetry, Differential Scanning
  • Crystallization
  • Epidermis / drug effects*
  • Epidermis / radiation effects
  • Lipid Bilayers / chemistry
  • Lipid Bilayers / metabolism
  • Lipid Peroxidation / drug effects
  • Metal Nanoparticles / chemistry
  • Metal Nanoparticles / toxicity*
  • Particle Size
  • Reactive Oxygen Species / metabolism
  • Spectrum Analysis, Raman
  • Surface Properties
  • Swine
  • Titanium / chemistry*
  • Ultraviolet Rays*

Substances

  • Lipid Bilayers
  • Reactive Oxygen Species
  • titanium dioxide
  • Titanium