title: Attenuation of Microbial Stress Due to Nano-Ag and Nano-TiO2Interactions under Dark Conditions.
abstract: Engineered nanomaterials (ENMs) are incorporated into thousands of commercial products, and their release into environmental systems creates complex mixtures with unknown toxicological outcomes. To explore this scenario, we probe the chemical and toxicological interactions of nanosilver (n-Ag) and nanotitania (n-TiO2) in Lake Michigan water, a natural aqueous medium, under dark conditions. We find that the presence of n-Ag induces a stress response in Escherichia coli, as indicated by a decrease in ATP production observed at low concentrations (in the μg L-1range), with levels that are environmentally relevant. However, when n-Ag and n-TiO2are present together in a mixture, n-TiO2attenuates the toxicity of n-Ag at and below 20 μg L-1by adsorbing Ag+(aq). We observe, however, that toxic stress cannot be explained by dissolved silver concentrations alone and, therefore, must also depend on silver associated with the nanoscale fraction. Although the attenuating effect of n-TiO2on n-Ag's toxicity is limited, this study emphasizes the importance of probing the toxicity of ENM mixtures under environmental conditions to assess how chemical interactions between nanoparticles change the toxicological effects of single ENMs in unexpected ways.
authors.affiliation: Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Wilke
authors.affiliation: Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Tiezheng
authors.initials: T
authors.lastname: Tong
authors.affiliation: Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Gaillard
authors.affiliation: Department of Civil and Environmental Engineering, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208, United States.
authors.forename: Kimberly A
authors.initials: KA
authors.lastname: Gray