Disposition and measured toxicity of zinc oxide nanoparticles and zinc ions against keratinocytes in cell culture and viable human epidermis

Abstract

Suspensions of the UV filter, zinc oxide nanoparticles (ZnO NP), are widely used in sunscreen products. This paper compared the relative disposition and local cytotoxicity of ZnO NP, and zinc ions formed on its dissolution, against keratinocyte cultures and in the human epidermis (ex vivo) after application of suspensions of ZnO NP. HaCaT keratinocyte cytotoxicities were found to be related to labile intra-cellular zinc but also total zinc and extra-cellular concentrations in cell culture media and to a degree ameliorated by the presence of a zinc chelating agent. Secondly, the zinc species were then dosed onto exposed ex vivo viable human epidermis and it was found that an increase in labile zinc level correlated with a shift in the metabolic state of the viable epidermis. This study highlights that excised viable skin acts as a more relevant model for determining cutaneous toxicity over keratinocyte monolayers in vitro.

Keywords:

• Zinc oxide nanoparticles
• zinc ion species
• sunscreens
• toxicity

Acknowledgments

We acknowledge the help given by our colleagues Dr Tetyana Shandala and Dr Zhen Song in assisting in the conduct of the cell culture studies and Dr Michael N. Pastore in aiding the data acquisition of the skin images and data presentation. The authors would like to acknowledge Ms Zahra Khabir and Associate Professor Andrei Zvyagin for their gift of the ⁶⁷ZnO NP and Dr Louise Smith for providing the HaCaT cell line.

Disclosure statement

A.H and L.M received partial salary support from Quality Medication Care Pty Ltd.

Additional information

Funding

This study was supported by an Australian National Health & Medical Research Council (NHMRC) Program Grant (1055176), by a NHMRC Fellowship to MR (1002611) and by Quality Medication Care Pty Ltd (AH, LM).