Photochemical interactions between n-Ag 2 S and n-TiO 2 amplify their bacterial stress response

Carolyn M. Wilke, Claire Petersen, Marco A. Alsina, Jean-Francois Gaillard*, Kimberly A Gray

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

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.

Original languageEnglish (US)
Pages (from-to)115-126
Number of pages12
JournalEnvironmental Science: Nano
Volume6
Issue number1
DOIs
StatePublished - Jan 1 2019

Fingerprint

Nanostructured materials
irradiation
Poisons
Adenosinetriphosphate
Irradiation
Reactive Oxygen Species
Adenosine Triphosphate
sulfide
Oxygen
Consumer products
Photochemical reactions
photochemistry
Sulfides
Wetlands
Wastewater treatment
Microorganisms
Escherichia coli
silver
Nanocomposites
Silver

ASJC Scopus subject areas

  • Materials Science (miscellaneous)
  • Environmental Science(all)

Cite this

@article{400c6e81ba724515b6505b67bfd00099,
title = "Photochemical interactions between n-Ag 2 S and n-TiO 2 amplify their bacterial stress response",
abstract = "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.",
author = "Wilke, {Carolyn M.} and Claire Petersen and Alsina, {Marco A.} and Jean-Francois Gaillard and Gray, {Kimberly A}",
year = "2019",
month = "1",
day = "1",
doi = "10.1039/c8en01159a",
language = "English (US)",
volume = "6",
pages = "115--126",
journal = "Environmental Science: Nano",
issn = "2051-8153",
publisher = "Royal Society of Chemistry",
number = "1",

}

Photochemical interactions between n-Ag 2 S and n-TiO 2 amplify their bacterial stress response . / Wilke, Carolyn M.; Petersen, Claire; Alsina, Marco A.; Gaillard, Jean-Francois; Gray, Kimberly A.

In: Environmental Science: Nano, Vol. 6, No. 1, 01.01.2019, p. 115-126.

Research output: Contribution to journalArticle

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-Francois

AU - Gray, Kimberly A

PY - 2019/1/1

Y1 - 2019/1/1

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.

UR - http://www.scopus.com/inward/record.url?scp=85060156481&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85060156481&partnerID=8YFLogxK

U2 - 10.1039/c8en01159a

DO - 10.1039/c8en01159a

M3 - Article

VL - 6

SP - 115

EP - 126

JO - Environmental Science: Nano

JF - Environmental Science: Nano

SN - 2051-8153

IS - 1

ER -