SYDNEY—The use of zinc oxide (ZnO) nanoparticles (NP) in sun-blocking cosmetic products has raised some safety concerns related to their potential transdermal penetration and resultant cytotoxicity. Therefore, Australian researchers—using a nonlinear optical microscopy that provides means for high-contrast imaging of ZnO NPs—were able to investigate, in vitro and in vivo, the nanoparticle uptake in skin (Biomed. Opt Express. 2011;2:3321-3333).
Two-photon action cross-section of a commercial product Zinclear, mean-sized 21 nm, measured by two techniques yielded consistent results. In order to demonstrate the quantitative imaging, nonlinear optical microscopy images of the excised human skin topically treated with Zinclear were acquired and processed ZnO values yielding nanoparticle concentration map in skin. Researchers reported accumulations of Zinclear ZnO nanoparticles were detected only on the skin surface and in skin folds reaching concentrations of 800 NPs/μm3.
