Synergistic Bacterial Stress Results from Exposure to Nano-Ag and

Feb 2, 2018 - Due to their widespread use and subsequent release, engineered nanomaterials (ENMs) will create complex mixtures and emergent systems in...
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Synergistic bacterial stress results from exposure to nanoAg and nano-TiO mixtures under light in environmental media 2

Carolyn M Wilke, Bettina Wunderlich, Jean-François Gaillard, and Kimberly A Gray Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b05629 • Publication Date (Web): 02 Feb 2018 Downloaded from http://pubs.acs.org on February 9, 2018

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Environmental Science & Technology

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Synergistic bacterial stress results from exposure to nano-Ag

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and nano-TiO2 mixtures under light in environmental media

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Carolyn M. Wilke, Bettina Wunderlich, Jean-François Gaillard*, and Kimberly A. Gray*

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Department of Civil and Environmental Engineering, Northwestern University, 2145

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Sheridan Road, Evanston, IL, 60208

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*Corresponding authors: Kimberly A. Gray and Jean-François Gaillard

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Email: [email protected], [email protected]

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Phone: (847)-467-4252, (847)-467-1376

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Fax: (847)-491-4011, (847)-491-4011

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Abstract

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Due to their widespread use and subsequent release, engineered nanomaterials

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(ENMs) will create complex mixtures and emergent systems in the natural environment

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where their chemical interactions may cause toxic stress to microorganisms. We

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previously showed that under dark conditions n-TiO2 attenuated bacterial stress caused

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by low concentrations of n-Ag ( 400 nm O2 ee-

O2



(2) Electrons injected into n-TiO2 conduction band

e-

O2

en-Ag e-

(1) High energy electrons activated by light near surface plasmon resonance wavelength

CB

n-TiO2

e-

e-

O2



H2O2

(3) Electrons swept by oxygen to form ROS

VB

Figure 6: Mechanism for photoactivity of n-Ag/n-TiO2 and ROS production (A) under ultraviolet radiation 58, 63, 68 and (B) under visible light 67.

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B

mg/L 0 mg L-1Anatase Anatase 1 mg L-1Anatase Anatase mg/L 10 mg L-1Anatase Anatase mg/L

1.2

*

Luminescence, relative to control

Luminescence, relative to control

A

*

0.8

* *

0.6

* *

0.4 0.2 0

1

* *

0.8 0.6 0.4 0.2

Green/red fluorescence ratio, rel. to control

L-1Anatase Anatase 0 mg mg/L Anatase L-1Anatase 1 mg mg/L L-1Anatase Anatase 10 mg mg/L

1.2

0 20 Concentration of n-Ag added (µg L-1)

D

C Green/red fluorescence ratio, rel. to control

0 mg mg/L L-1Rutile Rutile L-1Rutile Rutile 1 mg mg/L L-1Rutile Rutile 10 mg mg/L

1.2

0 0 20 Concentration of n-Ag added (µg L-1)

1

* 0.8

* 0.6 0.4

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* *

0.2 0

0 mg/L mg L-1Rutile Rutile Rutile mg L-1Rutile 1 mg/L 10 mg mg/L L-1Rutile Rutile

1.2 1 0.8 0.6 0.4 0.2 0

0 20 Concentration of n-Ag added (µg L-1)

0 20 Concentration of n-Ag added (µg L-1)

Figure 7: Stress caused by mixtures of n-Ag and (A) anatase and (B) rutile n-TiO2 mixtures to E. coli bacteria under SSI measured by surveying bacterial ATP. Stress caused by mixtures of n-Ag and (C) anatase and (D) rutile n-TiO2 mixtures to E. coli bacteria under SSI measured by surveying membrane integrity. Statistical significance (p < 0.05) for values compared with control and with same concentration of P25 is indicated by black and red asterisks, respectively.

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Environmental Science & Technology

TOC/Abstract Art: Under solar irradiation Engineered n-Ag

Ag+

adsorption Onto environmental surfaces Bacteria

n-Ag

O2

Oxidative dissolution

Enhanced ROS production

Ag+

hv

Natural nanoscale surfaces (e.g. iron oxides, clays)

n-TiO2

H2O, O2 Reactive oxygen species

Formation and photoactivation of new nanohybrids

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