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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] 8
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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