Aged TiO2-based nanocomposite used in sunscreens produces singlet oxygen under long-wave UV and sensitizes Escherichia coli to cadmium.
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.
CEA, IBEB , Laboratory of Microbial Ecology of the Rhizosphere and Extreme Environments, Saint-Paul-lez-Durance, F-13108, France.
Catherine
C
Santaella
Bruno
B
Allainmat
France
F
Simonet
Corinne
C
Chanéac
Jérome
J
Labille
Mélanie
M
Auffan
Jérome
J
Rose
Wafa
W
Achouak
D002104:Cadmium / Q000633:toxicity*; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects*; D017665:Hydroxyl Radical / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism; D026082:Singlet Oxygen / Q000737:chemistry*; D013473:Sunscreening Agents / Q000737:chemistry*; D014025:Titanium / Q000737:chemistry*; D014466:Ultraviolet Rays
D017382:Reactive Oxygen Species; D013473:Sunscreening Agents; D002104:Cadmium; C009495:titanium dioxide; D026082:Singlet Oxygen; D017665:Hydroxyl Radical; D014025:Titanium