Amorphous and crystalline cerium(IV) phosphates: biocompatible ROS-scavenging sunscreens.

This paper reports on a comprehensive study of the UV-shielding properties (namely, the sun protection factor and the factor of protection against UV-A radiation) and cytotoxicity (including photocytotoxicity) of amorphous and crystalline cerium(IV) phosphates. It has been shown that cerium(IV) phosphate NH4Ce2(PO4)3 is characterised by UV-shielding properties that are comparable to those of nanocrystalline TiO2 and CeO2. Moreover, cerium(IV) phosphates did not show toxicity towards cell cultures of NCTC L929 line mouse fibroblasts and human mesenchymal stem cells, in a wide range of concentrations, and even enhanced the proliferative activity of the latter. In a model study of the photoprotective properties of cerium(IV) phosphates on human mesenchymal stem cells, the pronounced protective effect of NH4Ce2(PO4)3 was observed, which was comparable to the shielding action of nanocrystalline CeO2. The results have shown that tetravalent cerium phosphates can be considered as promising UV-filters for sunscreen applications.