Understanding the interactions of nanoparticles (NPs) with skin is important from a\nconsumer and occupational health and safety perspective, as well as for the design of effective\nNP-based transdermal therapeutics. Despite intense efforts to elucidate the conditions that permit\nNP penetration, there remains a lack of translatable results from animal models to human skin.\nThe objectives of this study are to investigate the impact of common skin lotions on NP penetration\nand to quantify penetration differences of quantum dot (QD) NPs between freshly excised human\nand mouse skin. QDs were mixed in seven different vehicles, including five commercial skin lotions.\nThese were topically applied to skin using two exposure methods; a petri dish protocol and a Franz\ndiffusion cell protocol. QD presence in the skin was quantified using Confocal Laser Scanning\nMicroscopy. Results show that the commercial vehicles can significantly impact QD penetration\nin both mouse and human skin. Lotions that contain alpha hydroxyl acids (AHA) facilitated NP\npenetration. Lower QD signal was observed in skin studied using a Franz cell. Freshly excised human\nskin was also studied immediately after the sub-cutaneous fat removal process, then after 24 h rest\nex vivo. Resting human skin 24 h prior to QD exposure significantly reduced epidermal presence.\nThis study exemplifies how application vehicles, skin processing and the exposure protocol can affect\nQD penetration results and the conclusions that maybe drawn between skin models.
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