Aged TiO2‑Based Nanocomposite Used in Sunscreens Produces Singlet Oxygen under Long-Wave UV and Sensitizes Escherichia coli to Cadmium

• Published in: Environmental science & technology Vol. 48; no. 9; pp. 5245 - 5253
• Main Authors: Santaella, Catherine, Allainmat, Bruno, Simonet, France, Chanéac, Corinne, Labille, Jérome, Auffan, Mélanie, Rose, Jérome, Achouak, Wafa
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 06-05-2014
• Subjects: Animal, plant and microbial ecology; Biological and medical sciences; Cadmium - toxicity; Catalysis; Chemical Sciences; Electron Spin Resonance Spectroscopy; Environment and Society; Environmental Sciences; Escherichia coli - drug effects; Escherichia coli - metabolism; Escherichia coli - radiation effects; Fundamental and applied biological sciences. Psychology; Hydroxyl Radical - chemistry; Microbial ecology; Microscopy, Electron, Scanning; Nanocomposites; Oxidative Stress; Reactive Oxygen Species - metabolism; Singlet Oxygen - chemistry; Soil; Sunscreening Agents - chemistry; Titanium - chemistry; Ultraviolet Rays; Cosmetic; Titanium IV Oxides; Cadmium; Oxygen; Pollutant behavior; Escherichia coli; Transition metal; Heavy metal; Trace element; Ultraviolet radiation; Pathogenic; Bacteria; Poison; Nanocomposite; Sunscreen product; Titanium oxide; Solar radiation; Singlet; Nanostructured materials; Organic compounds; Enterobacteriaceae; Gram negative bacteria
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es500216t

TiO2-based nanocomposite (NC) are widely used as invisible UV protectant in cosmetics. These nanomaterials (NMs) end in the environment as altered materials. We have investigated the properties of T-Lite SF, a TiO2–NC used as sunscreen, after weathering in water and under light. We have examined the formation of ROS and their consequences on cell physiology of Escherichia coli. Our results show that aged-T-Lite SF produced singlet oxygen under low intensity long wave UV and formed hydroxyl radicals at high intensity. Despite the production of these ROS, T-Lite SF had neither effect on the viability of E. coli nor on mutant impaired in oxidative stress, did not induce mutagenesis and did not impair the integrity of membrane lipids, thus seemed safe to bacteria. However, when pre-exposed to T-Lite SF under low intensity UV, cells turned out to be more sensitive to cadmium, a priority pollutant widely disseminated in soil and surface waters. This effect was not a Trojan horse: sensitization of cells was dependent on the formation of singlet oxygen. These results provide a basis for caution, especially on NMs that have no straight environmental toxicity. It is crucial to anticipate indirect and combined effects of environmental pollutants and NMs.