Time-correlated single photon counting for simultaneous monitoring of zinc oxide nanoparticles and NAD(P)H in intact and barrier-disrupted volunteer skin.

Purpose There is a lack of relevant, non-animal alternatives for assessing exposure and toxicity of nanoparticle-containing cosmetics, e.g. sunscreens. Our goal was to evaluate timecorrelated single photon counting (TCSPC) for simultaneous monitoring of zinc oxide nanoparticles (ZnO-NP) and the metabolic state of volunteer skin.