Effect of Flexing and Massage on in Vivo Human Skin Penetration and Toxicity of Zinc Oxide Nanoparticles

Abstract

Aim: We assessed the effects of flexing and massage on human skin penetration and toxicity of topically applied coated and uncoated zinc oxide nanoparticles (~75 nm) in vivo. Materials & methods: Noninvasive multiphoton tomography with fluorescence lifetime imaging was used to evaluate the penetration of nanoparticles through the skin barrier and cellular apoptosis in the viable epidermis. Results: All nanoparticles applied to skin with flexing and massage were retained in the stratum corneum or skin furrows. No significant penetration into the viable epidermis was seen and no cellular toxicity was detected. Conclusion: Exposure of normal in vivo human skin to these nanoparticles under common in-use conditions of flexing or massage is not associated with significant adverse events.

Keywords::

• flexing
• human skin in vivo
• imaging
• massage
• nanoparticle penetration
• zinc oxide

Acknowledgements

We thank FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo), São Paulo for allowing Prof Leite-Silva to work with us at the University of Queensland. We also acknowledge C Hupple for his assistance in FLIM data analysis and Dr Washington H Sanchez for his initial pilot work in establishing the flexing methodology.

Financial & competing interests disclosure

This work was supported by the National Health & Medical Research Council of Australia. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state that they have obtained appropriate institutional review board approval or have followed the principles outlined in the Declaration of Helsinki for all human or animal experimental investigations. In addition, for investigations involving human subjects, informed consent has been obtained from the participants involved.

Additional information

Funding

This work was supported by the National Health & Medical Research Council of Australia. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed. No writing assistance was utilized in the production of this manuscript.