Development of CeO nanodot encrusted TiO nanoparticles with reduced photocatalytic activity and increased biocompatibility towards a human keratinocyte cell line

The cytotoxic and genotoxic effects of titanium dioxide (TiO 2 ) nanoparticles when exposed to ultraviolet (UV) radiation, particularly wavelengths between 320-400 nm, has raised concern over their safe use in health and cosmetic related products such as sunscreens. Cerium dioxide (CeO 2 ) nanoparticles have been demonstrated to display biocompatible properties and antioxidant activity due to redox cycling of the Ce 3+ /Ce 4+ oxidation states. In this work, CeO 2 /TiO 2 nanocomposites were prepared through a standard precipitation method at atomic concentrations (at%) of Ce relative to Ti of 2.5, 5 and 10 at%, with the aim of reducing the photocatalytic activity of the core TiO 2 nanoparticles and improve biocompatibility. The UV absorptive properties of the nanocomposite samples revealed excellent absorbance across the UV region as compared to pristine TiO 2 and CeO 2 . Furthermore, a drastic reduction in the photocatalysed decomposition of crystal violet, when in the presence of the nanocomposite samples, under both UV and solar simulated light was observed compared to the highly photoactive pristine TiO 2 . An optimal CeO 2 nanodot loading, displaying both high UV attenuation and low photocatalytic performance was determined at 5 at% and further in vitro biological testing revealed minimal impact on the cell viability of the human keratinocyte cell line (HaCaT) over a 24 h period with and without prior exposure to UV irradiation. In contrast, pristine TiO 2 nanoparticles induced toxicity to HaCaT cells with prior UV exposure before incubation, particularly at a dosage of 100 mg L −1 . Our findings demonstrate the effectiveness of CeO 2 nanodots in improving biocompatibility and its potential as a coating material for active inorganic UV filters. Low photocatalytic CeO 2 /TiO 2 nanocomposite particles with high UV attenuation and reduced ROS generation for application in sunscreen products.