Reliable and fast sensor for in vitro evaluation of solar protection factor based on the photobleaching kinetics of a nanocrystalline TiO2/dye UV-dosimeter

A reliable and fast sensor for in vitro evaluation of solar protection factors (SPFs) of cosmetic products, based on the photobleaching kinetics of a nanocrystalline TiO2/dye UV-dosimeter, has been devised. The accuracy, robustness and suitability of the new device was demonstrated by the excellent matching of the predicted and the in vivo results up to SPF 70, for four standard samples analyzed in blind. These results strongly suggest that our device can be useful for routine SPF evaluation in laboratories devoted to the development or production of cosmetic formulations, since the conventional in vitro methods tend to exhibit unacceptably high errors above SPF ∼30 and the conventional in vivo methods tend to be expensive and exceedingly time consuming.