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 NH 4 Ce 2 (PO 4 ) 3 is characterised by UV-shielding properties that are comparable to those of nanocrystalline TiO 2 and CeO 2 . 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 NH 4 Ce 2 (PO 4 ) 3 was observed, which was comparable to the shielding action of nanocrystalline CeO 2 . The results have shown that tetravalent cerium phosphates can be considered as promising UV-filters for sunscreen applications.