Imaging of zinc oxide nanoparticle penetration in human skin in vitro and in vivo

Andrei V. Zvyagin*, Xin Zhao, Audrey Gierden, Washington Sanchez, Justin A. Ross, Michael S. Roberts

*Corresponding author for this work

Research output: Contribution to journalArticle

223 Citations (Scopus)
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Abstract

Zinc oxide (ZnO-nano) and titanium dioxide nanoparticles (20 to 30 nm) are widely used in several topical skin care products, such as sunscreens. However, relatively few studies have addressed the subdermal absorption of these nanoparticles in vivo. We report on investigation of the distribution of topically applied ZnO in excised and in vivo human skin, using multiphoton microscopy (MPM) imaging with a combination of scanning electron microscopy (SEM) and an energy-dispersive x-ray (EDX) technique to determine the level of penetration of nanoparticles into the sub-dermal layers of the skin. The good visualization of ZnO in skin achieved appeared to result from two factors. First, the ZnO principal photoluminescence at 385 nm is in the "quiet" spectral band of skin autofluorescence dominated by the endogenous skin fluorophores, i.e., NAD[P]H and FAD. Second, the two-photon action cross section of ZnO-nano [σ ZnO (TPEF) σ 0.26 GM; diameter, 18 nm] is high: σ500-fold of that inferred from its bulk third-order nonlinear susceptibility [Imχ Zn O (3)], and is favorably compared to that of NAD[P]H and FAD. The overall outcome from MPM, SEM, and EDX studies was that, in humans in vivo, ZnO nanoparticles stayed in the stratum corneum (SC) and accumulated into skin folds and/or hair follicle roots of human skin. Given the lack of penetration of these nanoparticles past the SC and that the outermost layers of SC have a good turnover rate, these data suggest that the form of ZnO-nano studied here is unlikely to result in safety concerns.

Original languageEnglish
Article number064031
Pages (from-to)1-9
Number of pages9
JournalJournal of Biomedical Optics
Volume13
Issue number6
DOIs
Publication statusPublished - 2008

Bibliographical note

Copyright 2008 Society of Photo Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.

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