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Journal of Biomedical Optics

Imaging of zinc oxide nanoparticle penetration in human skin in vitro and in vivo
Author(s): Andrei V. Zvyagin; Xin Zhao; A. Gierden; Washington Sanchez; Justin Ross; Michael S. Roberts
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Paper 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 [σZnO(TPEF)< ~0.26 GM; diameter, 18 nm] is high: ~500-fold of that inferred from its bulk third-order nonlinear susceptibility [Im χZnO(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.

Paper Details

Date Published: 1 November 2008
PDF: 9 pages
J. Biomed. Opt. 13(6) 064031 doi: 10.1117/1.3041492
Published in: Journal of Biomedical Optics Volume 13, Issue 6
Show Author Affiliations
Andrei V. Zvyagin, Macquarie Univ. (Australia)
Xin Zhao, Macquarie Univ. (Australia)
A. Gierden, Univ. Claude Bernard Lyon 1 (France)
Washington Sanchez, The Univ. of Queensland (Australia)
Justin Ross, The Univ. of Queensland (Australia)
Michael S. Roberts, The Univ. of Queensland (Australia)

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