Development of CeO2 nanodot encrusted TiO2 nanoparticles with reduced photocatalytic activity and increased biocompatibility towards a human keratinocyte cell line

Abstract

The cytotoxic and genotoxic effects of titanium dioxide (TiO₂) 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 (CeO₂) nanoparticles have been demonstrated to display biocompatible properties and antioxidant activity due to redox cycling of the Ce³⁺/Ce⁴⁺ oxidation states. In this work, CeO₂/TiO₂ 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 TiO₂ nanoparticles and improve biocompatibility. The UV absorptive properties of the nanocomposite samples revealed excellent absorbance across the UV region as compared to pristine TiO₂ and CeO₂. 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 TiO₂. An optimal CeO₂ 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 TiO₂ 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 CeO₂ nanodots in improving biocompatibility and its potential as a coating material for active inorganic UV filters.