Hanson1, K.M., Gratton2, E., Bardeen1, C.J. 1Department of Chemistry, University of California at Riverside, Riverside, CA 92506, USA. 2Laboratory for Fluorescence Dynamics, Department of Bioengineering, University of California at Irvine, Irvine, CA 92697, USA.

This study by scientists at UC Riverside and UC Irvine demonstrated that two-photon fluorescence microscopy can be successfully used to image UV-induced ROS generation in both ex vivo skin and the EpiDerm human skin tissue equivalent. Both types of tissues gave identical results for the experimental protocol used, but the EpiDerm tissues provide the added advantage of reduced variability between samples as pigmentation, age, and body-site differences were nonexistent. For those reasons, the researchers used the EpiDerm tissues for the experiments in this paper. The number of UV-induced (20 mJ cm-2) reactive oxygen species (ROS) generated in nucleated epidermis is dependent upon the length of time the UV filter octocrylene, octylmethoxycinnamate, or benzophenone-3 remains on the skin surface. Two-photon fluorescence images acquired immediately after application of each formulation (2 mg cm-2) to the skin surface show that the number of ROS produced is dramatically reduced relative to the skin−UV filter control. After each UV filter remains on the skin surface for t=20 min, the number of ROS generated increases, although it remains below the number generated in the control. By t=60 min, the filters generate ROS above the control. The data show that when all three of the UV filters penetrate into the nucleated layers, the level of ROS increases above that produced naturally by epidermal chromophores under UV illumination.


EpiDerm, ROS, Reactive oxygen, Reactive oxygen species, Solar simulator, Sunscreen, Two-photon fluorescence, UV filter

Materials Tested

Benzophenone-3, Dihydrorhodamine (DHR), Finsolv solvent 5%, Methylparaben 0.1%, Octocrylene, Octymethoxycinnamate, Sepigel-305 3%, UVA, UVB

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