Saccharomyces cerevisiae strains as bioindicators for titanium dioxide sunscreen photoprotective and photomutagenic assessment.

Although several short-term assays are available for cosmetic photosafety assessment, cell models are usually highly sensitive to UV radiation, tending to overestimate both phototoxic and photomutagenic risks. In addition, these assays are performed with UV doses/fluences that do not correspond to actual environmental conditions. In this sense, Saccharomyces cerevisiae has already proved to be an interesting tool to predict photomutagenic potential of several compounds, including sunscreens. Yeast can support environmental UVB doses compatible with human daily sunlight exposure, allowing the use of irradiation sources to faithfully mimic the external conditions of ambient sunlight. Herein, we used a set of S. cerevisiae mutant strains sensitive to UVA, UVB and Solar Simulated Light sources in order to evaluate their potential as bioindicators for sunscreen development. The bioindicator potential of the strains was tested with the widely-used titanium dioxide inorganic sunscreen. The AWP001 (yno1) and LPW002 (ogg1yno1) strains obtained in this study stood out as promising experimental tools for the validation of this assay. Overall, our results evidenced a set of S. cerevisiae strains particularly useful for evaluating both photoprotective (efficacy) and photo/antiphotomutagenic (safety) potential of UV filters, meeting the industries and regulatory agencies demand for robust and efficient in vitro screening tests.

Titanium dioxide-montmorillonite nanocomposite as photoprotective agent against ultraviolet B radiation-induced mutagenesis in Saccharomyces cerevisiae: a potential candidate for safer sunscreens.

Photoprotective potential and biological consequences (mutagenic potential) of octyl-dimethyl-PABA (ODP), titanium dioxide (TiO2 ), and montmorillonite (MMT) upon ultraviolet B (UVB) irradiation, alone and in different associations [physical mixtures (PMs)], were evaluated using a Saccharomyces cerevisiae ogg1 mutant (deficient) strain. In addition, we developed and characterized a delaminated TiO2-pillared MMT, called the TiO2 -MMT nanocomposite (NC), which was also investigated in terms of its photoprotective and mutagenic potential. Overall, our results revealed an interesting TiO2 -MMT NC endowed with antimutagenic activity that can be associated to organic sunscreen molecule (ODP) and still maintain its positive effect, whereas its respective PM is unable to grant antimutagenic protection against UVB.