Titanium dioxide and zinc oxide nanoparticles induce autophagy associated with toxicity effects in primary human keratinocytes : a dose relevance study

The application of nanomaterials in cosmetic, sunscreens, and topical products is growing rapidly, even as health concerns arise about the potential hazards to their use. This research work is centered on the toxicological effects of titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles, which are commonly used in sunscreens, in the interaction with primary human keratinocytes. Both TiO2 and ZnO nanoparticles are found to cause toxicity in vitro, such as cytotoxicity, oxidative stress, genotoxicity, and inflammasome activation in a concentration-dependent manner through conducting a dose relevance study. Furthermore, TiO2 and ZnO nanoparticles are capable of inducing autophagy within a low subtoxic dose range. This is the first study of autophagy induced in primary human keratinocytes by nano TiO2 and ZnO without other stimuli. The low triggering dose range of autophagy found in keratinocytes would be useful impetus for the research community to look more into the safety limits of nanomaterials applied to skin products.DOCTOR OF PHILOSOPHY (MSE