Independent cytotoxic and inflammatory responses to zinc oxide nanoparticles in human monocytes and macrophages

Abstract

Significant public and scientific concerns remain for the use of nanoparticles (NPs) in commercial products, particularly those applied topically for skin care. There are currently a range of metal oxides formulated into many sunscreens that are present at the nanoscale. In this study, we sought to determine the effect of the size and dispersion of one type of these NPs (zinc oxide) on immune cell function and cytotoxicity for human macrophages and monocytes, which are key cells for particle and debris clearance in the skin. We have found that particle size and coating, but surprisingly, not agglomeration, are key determinates of nanoparticle cytotoxicity in an in vitro culture system of human immune cells. Most importantly, we found that this nanoparticle-induced cellular immune signalling, can be decoupled from cytotoxicity and surface coating, so that at an equivalent cytotoxic load, smaller particles induce a greater cellular response.

Keywords::

• Nanoparticles
• nanotoxicology
• biocompatibility
• particle characterisation
• surface chemistry

Acknowledgements

The authors would like to thank Victoria Coleman and the National Measurement Institute (NMI) for assistance with disc centrifugation assay and the RMIT Flow Cytometry Facility for assistance with cytokines and apoptosis assays. Funding: Project was supported by National Health and Medical Research Council (NHMRC) project grant #616621, Advanced Manufacturing Cooperative Research Centre (AMCRC), The Victorian Centre for Advanced Materials Manufacturing Ltd (VCAMM), Micronisers Pty Ltd. and Baxter Laboratories Pty Ltd.