The effect of formulation on the penetration of coated and uncoated zinc oxide nanoparticles into the viable epidermis of human skin in vivo

Eur J Pharm Biopharm. 2013 Jun;84(2):297-308. doi: 10.1016/j.ejpb.2013.01.020. Epub 2013 Feb 28.


The use of nanoparticulate zinc oxide (ZnO-NP) in sunscreens and other cosmetic products has raised public health concerns. The two key issues are the extent of exposure to ZnO-NP and the likely hazard after the application of ZnO-NP in sunscreen and cosmetic products to humans in vivo. Our aims were to assess exposure by the extent of ZnO-NP penetration into the viable epidermis and hazard by changes in the viable epidermal redox state for a number of topical products. Of particular interest is the role of the particle coating, formulation used, and the presence of any enhancers. Multiphoton tomography with fluorescence lifetime imaging microscopy (MPT-FLIM) was used to simultaneously observe ZnO-NP penetration and potential metabolic changes within the viable epidermis of human volunteers after topical application of various ZnO-NP products. Coated and uncoated ZnO-NP remained in the superficial layers of the SC and in the skin furrows. We observed limited penetration of coated ZnO-NP dispersed in a water-in-oil emulsion formulation, which was predominantly localized adjacent to the skin furrow. However, the presence of ZnO-NP in the viable epidermis did not alter the metabolic state or morphology of the cells. In summary, our data suggest that some limited penetration of coated and uncoated ZnO-NP may occur into viable stratum granulosum epidermis adjacent to furrows, but that the extent is not sufficient to affect the redox state of those viable cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cosmetics
  • Drug Carriers
  • Drug Delivery Systems
  • Epidermis / drug effects*
  • Female
  • Humans
  • Male
  • Metal Nanoparticles
  • Microscopy, Electron, Transmission
  • Microscopy, Fluorescence
  • Middle Aged
  • Nanoparticles / chemistry*
  • Oxidation-Reduction
  • Skin / drug effects*
  • Skin Absorption*
  • Sunscreening Agents / chemistry*
  • Sunscreening Agents / pharmacokinetics
  • Young Adult
  • Zinc Oxide / chemistry*
  • Zinc Oxide / pharmacokinetics


  • Cosmetics
  • Drug Carriers
  • Sunscreening Agents
  • Zinc Oxide