TY - JOUR
T1 - Photochemical interactions between n-Ag 2 S and n-TiO 2 amplify their bacterial stress response
AU - Wilke, Carolyn M.
AU - Petersen, Claire
AU - Alsina, Marco A.
AU - Gaillard, Jean François
AU - Gray, Kimberly A.
N1 - Funding Information:
Metal analysis was performed at the Northwestern University Quantitative Bio-element Imaging Center and was funded by the Chicago Biomedical Consortium with support from the Searle Funds at The Chicago Community Trust and supported by the Office of The Director, National Institutes of Health of the National Institutes of Health under Award Number S10OD020118. Thanks to Keith MacRenaris and Rebecca Sponenburg for assistance with ICP-MS. This work made use of the EPIC facility of Northwestern University's NUANCE Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-1542205); the MRSEC program (NSF DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. Portions of this work were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, E. I. DuPont de Nemours & Co., and The Dow Chemical Company. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. C. M. W. also acknowledges the support of the Northwestern University Presidential Fellowship.
Publisher Copyright:
© The Royal Society of Chemistry.
PY - 2019
Y1 - 2019
N2 - Under the reducing conditions of wetlands and anaerobic wastewater treatment processes, nanosilver (n-Ag) released from consumer products reacts with sulfide to form Ag 2 S, which is believed to be stable and practically benign. However, in the natural environment, these nanosized silver sulfide particles (n-Ag 2 S) may interact with light and other nanomaterials to create oxidizing conditions that may destabilize n-Ag 2 S, releasing Ag + and causing stress to microorganisms. We investigate this scenario by monitoring the ATP levels of E. coli exposed to mixtures of n-Ag 2 S and n-TiO 2 , another nanomaterial with high likelihood of environmental release. Under dark conditions, we find that sulfidation increases the threshold concentration for microbial stress relative to n-Ag. Under simulated solar irradiation (SSI), exposure to n-Ag 2 S alone does not depress bacterial ATP levels in the concentration range tested (≤1 mg L −1 as Ag). However in the presence of 1 mg L −1 n-TiO 2 and under SSI, n-Ag 2 S causes synergistic toxic stress and enhances the production of reactive oxygen species (ROS). Based on the photochemistry of these nanomaterials and our measurements of dissolved Ag, we propose that under environmental conditions the ROS produced by n-TiO 2 dissolves n-Ag 2 S, releasing Ag + that can then be photoreduced on the surface of n-TiO 2 to form a highly photoactive and phototoxic nanocomposite. This work reveals that under oxidizing conditions n-Ag 2 S is prone to transformations that cause microbial stress. Overall, we provide further evidence that chemical interactions between multiple nanomaterials under irradiation can dramatically change their toxic effects.
AB - Under the reducing conditions of wetlands and anaerobic wastewater treatment processes, nanosilver (n-Ag) released from consumer products reacts with sulfide to form Ag 2 S, which is believed to be stable and practically benign. However, in the natural environment, these nanosized silver sulfide particles (n-Ag 2 S) may interact with light and other nanomaterials to create oxidizing conditions that may destabilize n-Ag 2 S, releasing Ag + and causing stress to microorganisms. We investigate this scenario by monitoring the ATP levels of E. coli exposed to mixtures of n-Ag 2 S and n-TiO 2 , another nanomaterial with high likelihood of environmental release. Under dark conditions, we find that sulfidation increases the threshold concentration for microbial stress relative to n-Ag. Under simulated solar irradiation (SSI), exposure to n-Ag 2 S alone does not depress bacterial ATP levels in the concentration range tested (≤1 mg L −1 as Ag). However in the presence of 1 mg L −1 n-TiO 2 and under SSI, n-Ag 2 S causes synergistic toxic stress and enhances the production of reactive oxygen species (ROS). Based on the photochemistry of these nanomaterials and our measurements of dissolved Ag, we propose that under environmental conditions the ROS produced by n-TiO 2 dissolves n-Ag 2 S, releasing Ag + that can then be photoreduced on the surface of n-TiO 2 to form a highly photoactive and phototoxic nanocomposite. This work reveals that under oxidizing conditions n-Ag 2 S is prone to transformations that cause microbial stress. Overall, we provide further evidence that chemical interactions between multiple nanomaterials under irradiation can dramatically change their toxic effects.
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U2 - 10.1039/c8en01159a
DO - 10.1039/c8en01159a
M3 - Article
AN - SCOPUS:85060156481
VL - 6
SP - 115
EP - 126
JO - Environmental Science: Nano
JF - Environmental Science: Nano
SN - 2051-8153
IS - 1
ER -