Efficient inorganic UV shields, mostly based on refracting TiO2 particles, have dramatically changed the sun exposure habits. Unfortunately, health concerns have emerged from the pro-oxidant photocatalytic effect of UV-irradiated TiO2, which mediates toxic effects on cells. Therefore, improvements in cosmetic solar shield technology are a strong priority. CeO2 nanoparticles are not only UV refractors but also potent biological antioxidants due to the surface 3+/4+ valency switch, which confers anti-inflammatory, anti-ageing and therapeutic properties. Herein, UV irradiation protocols were set up, allowing selective study of the extra-shielding effects of CeO2vs. TiO2 nanoparticles on reporter cells. TiO2 irradiated with UV (especially UVA) exerted strong photocatalytic effects, superimposing their pro-oxidant, cell-damaging and mutagenic action when induced by UV, thereby worsening the UV toxicity. On the contrary, irradiated CeO2 nanoparticles, via their Ce3+/Ce4+ redox couple, exerted impressive protection on UV-treated cells, by buffering oxidation, preserving viability and proliferation, reducing DNA damage and accelerating repair; strikingly, they almost eliminated mutagenesis, thus acting as an important tool to prevent skin cancer. Interestingly, CeO2 nanoparticles also protect cells from the damage induced by irradiated TiO2, suggesting that these two particles may also complement their effects in solar lotions. CeO2 nanoparticles, which intrinsically couple UV shielding with biological and genetic protection, appear to be ideal candidates for next-generation sun shields. © The Royal Society of Chemistry 2015.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledgements: F.C. and M.D.N. are recipient of fellowships from the PhD school in Materials for Health, Energy and Environment, Universita di Roma Tor Vergata. We wish to thank Dr Vittoria Maresca, Ospedale S. Gallicano (Roma, Italy), and Prof. Giampiero Gualandi, Universita La Tuscia (Viterbo, Italy) for invaluable support. Thanks are due to Prof. Francesco Stellacci and Dr Marta Mameli, Ecole Polytechnique Federal de Lausanne (EPFL, Lausanne, Switzerland), for invaluable discussions and support. We thank Dr Dalaver H. Anjum, King Abdullah University of Science and Technology (KAUST, Thuwal, Saudi Arabia) for assistance in TEM observations; Ms Marianeve Polimeno and Ms Monica Maio (Dipartimento di Biologia, Universita di Roma Tor Vergata) are acknowledged for the experiments with HaCat cells.