62 research outputs found
Aquatic Ecotoxicity of Microplastics and Nanoplastics: Lessons Learned from Engineered Nanomaterials
Early-stage precipitation kinetics of zinc sulfide nanoclusters forming in the presence of cysteine
International audienceNanoparticulate metal sulfides such as ZnS are important for the speciation of pollutant metals in sediments, wastewater effluent, and other sulfidic environments. In these settings, particles of ZnS are formed in the presence of natural organic acids such as humic substances, proteins and other biomolecules that will interfere with cluster growth and aggregation kinetics. Thiol-containing organics such as cysteine are capable of adsorbing to clusters and nanoparticles of metal sulfides as they precipitate from solution. The thiols induce electrostatic repulsive forces at particle interfaces resulting in slow aggregation rates. The aim of this work was to investigate how cysteine influences the nucleation and growth rate of ZnS during early stages (less than one day) of precipitation. Results from time-resolved small angle X-ray scattering and dynamic light scattering confirmed that cysteine altered the ZnS precipitation process by decreasing aggregation rates of polynuclear ZnS clusters (smallest size <1 nm). Furthermore, with decreased aggregation between clusters induced by cysteine, the growth rates of the nanoclusters appeared to increase. Characterization of the precipitation products by Zn extended X-ray absorption spectroscopy also indicated that an excess of cysteine relative to ZnS resulted in larger subunits compared to mixtures with equimolar quantities of cysteine and ZnS. Overall these results provide clues toward the mechanism by which natural organic ligands interfere with the ZnS precipitation process in sediments and enable nanoscale clusters or particles to persist. (c) 2011 Elsevier B.V. All rights reserved
CTD data profiling to assess the natural hazard of active submarine vent fields: the case of Santorini Island
A poster presented at the Geological Society of Greece Annual Conference, held in Athens, 22-24 May 201
Biotic and Abiotic Interactions in Aquatic Microcosms Determine Fate and Toxicity of Ag Nanoparticles. Part 1. Aggregation and Dissolution
To better understand their fate and toxicity in aquatic
environments,
we compared the aggregation and dissolution behavior of gum arabic
(GA) and polyvinylpyrrolidone (PVP) coated Ag nanoparticles (NPs)
in aquatic microcosms. There were four microcosm types: surface water;
water and sediment; water and aquatic plants; or water, sediment,
and aquatic plants. Dissolution and aggregation behavior of AgNPs
were examined using ultracentrifugation, ultrafiltration, and asymmetrical
flow field flow fractionation coupled to ultraviolet–visible
spectroscopy, dynamic and static laser light scattering, and inductively
coupled plasma mass spectrometry. Plants released dissolved organic
matter (DOM) into the water column either through active or passive
processes in response to Ag exposure. This organic matter fraction
readily bound Ag ions. The plant-derived DOM had the effect of stabilizing
PVP-AgNPs as primary particles, but caused GA-AgNPs to be removed
from the water column, likely by dissolution and binding of released
Ag ions on sediment and plant surfaces. The destabilization of the
GA-AgNPs also corresponded with X-ray absorption near edge spectroscopy
results which suggest that 22–28% of the particulate Ag was
associated with thiols and 5–14% was present as oxides. The
results highlight the potential complexities of nanomaterial behavior
in response to biotic and abiotic modifications in ecosystems, and
may help to explain differences in toxicity of Ag observed in realistic
exposure media compared to simplified laboratory exposures
Mechanism of Silver Nanoparticle Toxicity Is Dependent on Dissolved Silver and Surface Coating in Caenorhabditis elegans
International audienceThe rapidly increasing use of silver nanoparticles (Ag NPs) in consumer products and medical applications has raised ecological and human health concerns. A key question for addressing these concerns is whether Ag NP toxicity is mechanistically unique to nanoparticulate silver, or if it is a result of the release of silver ions. Furthermore, since Ag NPs are produced in a large variety of monomer sizes and coatings, and since their physicochemical behavior depends on the media composition, it is important to understand how these variables modulate toxicity. We found that a lower ionic strength medium resulted in greater toxicity (measured as growth inhibition) of all tested Ag NPs to Caenorhabditis elegans and that both dissolved silver and coating influenced Ag NP toxicity. We found a linear correlation between Ag NP toxicity and dissolved silver, but no correlation between size and toxicity. We used three independent and complementary approaches to investigate the mechanisms of toxicity of differentially coated and sized Ag NPs: pharmacological (rescue with trolox and N-acetylcysteine), genetic (analysis of metal-sensitive and oxidative stress-sensitive mutants), and physicochemical (including analysis of dissolution of Ag NPs). Oxidative dissolution was limited in our experimental conditions (maximally 15% in 24 h) yet was key to the toxicity of most Ag NPs, highlighting a critical role for dissolved silver complexed with thiols in the toxicity of all tested Ag NPs. Some Ag NPs (typically less soluble due to size or coating) also acted via oxidative stress, an effect specific to nanoparticulate silver. However, in no case studied here was the toxicity of a Ag NP greater than would be predicted by complete dissolution of the same mass of silver as silver ions
Release of TiO<sub>2</sub> Nanoparticles from Sunscreens into Surface Waters: A One-Year Survey at the Old Danube Recreational Lake
Monitoring data are
necessary for the future production of engineered
nanomaterials and the development of regulations for nanomaterials.
Therefore, it is necessary to develop methods that reliably detect
and quantify nanomaterials in real-world systems at expectedly low
concentrations. In this work we tested several methodological approaches
to detect titanium dioxide nanomaterials released from sunscreen products
into the Old Danube Lake (Vienna, Austria), which is heavily used
for recreational activities like bathing and water sports during the
summer season. During a 12-month period suspended particulate matter
(SPM) was collected from the lake and analyzed using a combination
of complementary techniques. By sampling at a location approximately
50 m from the nearest bathing area and at one meter depth from the
water surface, we focused on the potentially mobile fraction of the
released nanoparticles. We were able to identify titanium dioxide
nanoparticles stemming from sunscreens in the suspended matter of
the lake using electron microscopy. Bulk analysis of SPM clearly shows
an increase of Ti-containing particles during the summer season. These
analyses, however, are not able to distinguish sunscreen nanoparticles
from natural Ti-bearing nanoparticles. Therefore, Elemental ratios
of Ti with Al, V, Ga, Y, Nb, Eu, Ho, Er, Tm, Yb, and Ta as determined
by ICPMS and ICPOES, in combination with single particle ICPMS analysis
were applied to establish local background values. The observed mild
increase of Ti elemental ratios, compared to spring background values
indicates that the residence time of released nanomaterials in the
water column is rather short. Overall, the advantages and disadvantages
of the methods used to detect and characterize the nanomaterials are
discussed
Mechanism of Silver Nanoparticle Toxicity Is Dependent on Dissolved Silver and Surface Coating in <i>Caenorhabditis elegans</i>
The rapidly increasing use of silver nanoparticles (Ag
NPs) in consumer products and medical applications has raised ecological
and human health concerns. A key question for addressing these concerns
is whether Ag NP toxicity is mechanistically unique to nanoparticulate
silver, or if it is a result of the release of silver ions. Furthermore,
since Ag NPs are produced in a large variety of monomer sizes and
coatings, and since their physicochemical behavior depends on the
media composition, it is important to understand how these variables
modulate toxicity. We found that a lower ionic strength medium resulted
in greater toxicity (measured as growth inhibition) of all tested
Ag NPs to <i>Caenorhabditis elegans</i> and that both dissolved
silver and coating influenced Ag NP toxicity. We found a linear correlation
between Ag NP toxicity and dissolved silver, but no correlation between
size and toxicity. We used three independent and complementary approaches
to investigate the mechanisms of toxicity of differentially coated
and sized Ag NPs: pharmacological (rescue with trolox and N-acetylcysteine),
genetic (analysis of metal-sensitive and oxidative stress-sensitive
mutants), and physicochemical (including analysis of dissolution of
Ag NPs). Oxidative dissolution was limited in our experimental conditions
(maximally 15% in 24 h) yet was key to the toxicity of most Ag NPs,
highlighting a critical role for dissolved silver complexed with thiols
in the toxicity of all tested Ag NPs. Some Ag NPs (typically less
soluble due to size or coating) also acted via oxidative stress, an
effect specific to nanoparticulate silver. However, in no case studied
here was the toxicity of a Ag NP greater than would be predicted by
complete dissolution of the same mass of silver as silver ions
Cysteine-Induced Modifications of Zero-valent Silver Nanomaterials: Implications for Particle Surface Chemistry, Aggregation, Dissolution, and Silver Speciation
The persistence of silver nanoparticles in aquatic environments
and their subsequent impact on organisms depends on key transformation
processes, which include aggregation, dissolution, and surface modifications
by metal-complexing ligands. Here, we studied how cysteine, an amino
acid representative of thiol ligands that bind monovalent silver,
can alter the surface chemistry, aggregation, and dissolution of zero-valent
silver nanoparticles. We compared nanoparticles synthesized with two
coatings, citrate and polyvinylpirrolidone (PVP), and prepared nanoparticle
suspensions (approximately 8 μM total Ag) containing an excess
of cysteine (400 μM). Within 48 h, up to 47% of the silver had
dissolved, as indicated by filtration of the samples with a 0.025-μm
filter. Initial dissolution rates were calculated from the increase
of dissolved silver concentration when particles were exposed to cysteine
and normalized to the available surface area of nanoparticles in solution.
In general, the rates of dissolution were almost 3 times faster for
citrate-coated nanoparticles relative to PVP-coated nanoparticles.
Rates tended to be slower in solutions with higher ionic strength
in which the nanoparticles were aggregating. X-ray absorption spectroscopy
analysis of the particles suggested that cysteine adsorbed to silver
nanoparticles surfaces through the formation of Ag(+I)sulfhydryl
bonds. Overall, the results of this study highlight the importance
of modifications by sulfhydryl-containing ligands that can drastically
influence the long-term reactivity of silver nanoparticles in the
aquatic environment and their bioavailability to exposed organisms.
Our findings demonstrate the need to consider multiple interlinked
transformation processes when assessing the bioavailability, environmental
risks, and safety of nanoparticles, particularly in the presence of
metal-binding ligands
Mechanism of Silver Nanoparticle Toxicity Is Dependent on Dissolved Silver and Surface Coating in <i>Caenorhabditis elegans</i>
The rapidly increasing use of silver nanoparticles (Ag
NPs) in consumer products and medical applications has raised ecological
and human health concerns. A key question for addressing these concerns
is whether Ag NP toxicity is mechanistically unique to nanoparticulate
silver, or if it is a result of the release of silver ions. Furthermore,
since Ag NPs are produced in a large variety of monomer sizes and
coatings, and since their physicochemical behavior depends on the
media composition, it is important to understand how these variables
modulate toxicity. We found that a lower ionic strength medium resulted
in greater toxicity (measured as growth inhibition) of all tested
Ag NPs to <i>Caenorhabditis elegans</i> and that both dissolved
silver and coating influenced Ag NP toxicity. We found a linear correlation
between Ag NP toxicity and dissolved silver, but no correlation between
size and toxicity. We used three independent and complementary approaches
to investigate the mechanisms of toxicity of differentially coated
and sized Ag NPs: pharmacological (rescue with trolox and N-acetylcysteine),
genetic (analysis of metal-sensitive and oxidative stress-sensitive
mutants), and physicochemical (including analysis of dissolution of
Ag NPs). Oxidative dissolution was limited in our experimental conditions
(maximally 15% in 24 h) yet was key to the toxicity of most Ag NPs,
highlighting a critical role for dissolved silver complexed with thiols
in the toxicity of all tested Ag NPs. Some Ag NPs (typically less
soluble due to size or coating) also acted via oxidative stress, an
effect specific to nanoparticulate silver. However, in no case studied
here was the toxicity of a Ag NP greater than would be predicted by
complete dissolution of the same mass of silver as silver ions
Mechanism of Silver Nanoparticle Toxicity Is Dependent on Dissolved Silver and Surface Coating in <i>Caenorhabditis elegans</i>
The rapidly increasing use of silver nanoparticles (Ag
NPs) in consumer products and medical applications has raised ecological
and human health concerns. A key question for addressing these concerns
is whether Ag NP toxicity is mechanistically unique to nanoparticulate
silver, or if it is a result of the release of silver ions. Furthermore,
since Ag NPs are produced in a large variety of monomer sizes and
coatings, and since their physicochemical behavior depends on the
media composition, it is important to understand how these variables
modulate toxicity. We found that a lower ionic strength medium resulted
in greater toxicity (measured as growth inhibition) of all tested
Ag NPs to <i>Caenorhabditis elegans</i> and that both dissolved
silver and coating influenced Ag NP toxicity. We found a linear correlation
between Ag NP toxicity and dissolved silver, but no correlation between
size and toxicity. We used three independent and complementary approaches
to investigate the mechanisms of toxicity of differentially coated
and sized Ag NPs: pharmacological (rescue with trolox and N-acetylcysteine),
genetic (analysis of metal-sensitive and oxidative stress-sensitive
mutants), and physicochemical (including analysis of dissolution of
Ag NPs). Oxidative dissolution was limited in our experimental conditions
(maximally 15% in 24 h) yet was key to the toxicity of most Ag NPs,
highlighting a critical role for dissolved silver complexed with thiols
in the toxicity of all tested Ag NPs. Some Ag NPs (typically less
soluble due to size or coating) also acted via oxidative stress, an
effect specific to nanoparticulate silver. However, in no case studied
here was the toxicity of a Ag NP greater than would be predicted by
complete dissolution of the same mass of silver as silver ions
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