Biocompatible Bi(OH)3nanoparticles with reduced photocatalytic activityas possible ultraviolet filter in sunscreens

In this study we investigate readily synthesised Bi(OH)3nanoparticles as a novel, multifunctional ultraviolet filter for sunscreen. The absorbance of Bi(OH)3NPs in the ultraviolet region is comparable to that of both ZnO and TiO2NPs used in commercial sunscreens. In vitro photoprotection results show that the combination of TiO2/Bi(OH)3is more efficient than TiO2/ZnO over the whole UV range, with an increase in sun protection factor of 28%. The emulsions show rheological properties comparable to those of commercial sunscreens. The combination of TiO2/Bi(OH)3led to insignificant damage on pre-painted steel panels after exterior exposure for twelve weeks. We also demonstrate that the addition of Bi(OH)3NPs reduces the degradation of crystal violet by photocatalytically active TiO2or ZnO NPs under ultraviolet exposure. Finally, assessment of the biocompatibility of Bi(OH)3with HaCaT keratinocytes and Madin-Darby Canine Kidney (MDCK) cells in vitro is described.