11 research outputs found
Bioaccumulation of Multiwall Carbon Nanotubes in <i>Tetrahymena thermophila</i> by Direct Feeding or Trophic Transfer
Consumer
goods contain multiwall carbon nanotubes (MWCNTs) that
could be released during product life cycles into the environment,
where their effects are uncertain. Here, we assessed MWCNT bioaccumulation
in the protozoan <i>Tetrahymena thermophila</i> via trophic
transfer from bacterial prey (<i>Pseudomonas aeruginosa</i>) versus direct uptake from growth media. The experiments were conducted
using <sup>14</sup>C-labeled MWCNT (<sup>14</sup>C-MWCNT) doses at
or below 1 mg/L, which proved subtoxic since there were no adverse
effects on the growth of the test organisms. A novel contribution
of this study was the demonstration of the ability to quantify MWCNT
bioaccumulation at low (sub μg/kg) concentrations accomplished
by employing accelerator mass spectrometry (AMS). After the treatments
with MWCNTs at nominal concentrations of 0.01 mg/L and 1 mg/L, <i>P. aeruginosa</i> adsorbed considerable amounts of MWCNTs: (0.18
± 0.04) μg/mg and (21.9 ± 4.2) μg/mg bacterial
dry mass, respectively. At the administered MWCNT dose of 0.3 mg/L, <i>T. thermophila</i> accumulated up to (0.86 ± 0.3) μg/mg
and (3.4 ± 1.1) μg/mg dry mass by trophic transfer and
direct uptake, respectively. Although MWCNTs did not biomagnify in
the microbial food chain, MWCNTs bioaccumulated in the protozoan populations
regardless of the feeding regime, which could make MWCNTs bioavailable
for organisms at higher trophic levels
Biological Uptake and Depuration of Radio-labeled Graphene by <i>Daphnia magna</i>
Graphene
layers are potential candidates in a large number of applications.
However, little is known about their ecotoxicological risks largely
as a result of a lack of quantification techniques in complex environmental
matrices. In this study, graphene was synthesized by means of graphitization
and exfoliation of sandwich-like FePO<sub>4</sub>/dodecylamine hybrid
nanosheets, and <sup>14</sup>C was incorporated in the synthesis. <sup>14</sup>C-labeled graphene was spiked to artificial freshwater and
the uptake and depuration of graphene by <i>Daphnia magna</i> were assessed. After exposure for 24 h to a 250 μg/L solution
of graphene, the graphene concentration in the organism was nearly
1% of the organism dry mass. These organisms excreted the graphene
to clean artificial freshwater and achieved roughly constant body
burdens after 24 h depuration periods regardless of the initial graphene
exposure concentration. Addition of algae and humic acid to water
during the depuration period resulted in release of a significant
fraction (>90%) of the accumulated graphene, but some still remained
in the organism. Accumulated graphene in adult <i>Daphnia</i> was likely transferred to the neonates. The uptake and elimination
results provided here support the environmental risk assessment of
graphene and the graphene quantification method is a powerful tool
for additional studies
Detection and Quantification of Graphene-Family Nanomaterials in the Environment
An increase in production
of commercial products containing graphene-family
nanomaterials (GFNs) has led to concern over their release into the
environment. The fate and potential ecotoxicological effects of GFNs
in the environment are currently unclear, partially due to the limited
analytical methods for GFN measurements. In this review, the unique
properties of GFNs that are useful for their detection and quantification
are discussed. The capacity of several classes of techniques to identify
and/or quantify GFNs in different environmental matrices (water, soil,
sediment, and organisms), after environmental transformations, and
after release from a polymer matrix of a product is evaluated. Extraction
and strategies to combine methods for more accurate discrimination
of GFNs from environmental interferences as well as from other carbonaceous
nanomaterials are recommended. Overall, a comprehensive review of
the techniques available to detect and quantify GFNs are systematically
presented to inform the state of the science, guide researchers in
their selection of the best technique for the system under investigation,
and enable further development of GFN metrology in environmental matrices.
Two case studies are described to provide practical examples of choosing
which techniques to utilize for detection or quantification of GFNs
in specific scenarios. Because the available quantitative techniques
are somewhat limited, more research is required to distinguish GFNs
from other carbonaceous materials and improve the accuracy and detection
limits of GFNs at more environmentally relevant concentrations
Biological Uptake, Distribution, and Depuration of Radio-Labeled Graphene in Adult Zebrafish: Effects of Graphene Size and Natural Organic Matter
The
exciting commercial application potential of graphene materials
may inevitably lead to their increasing release into the environment
where they may pose ecological risks. This study focused on using
carbon-14-labeled few-layer graphene (FLG) to determine whether the
size of graphene plays a role in its uptake, depuration, and biodistribution
in adult zebrafish. After 48 h exposure to larger FLG (L-FLG) at 250
μg/L, the amount of graphene in the organism was close to 48
mg/kg fish dry mass, which was more than 170-fold greater than the
body burden of those exposed to the same concentration of smaller
FLG (S-FLG). The amount of uptake for both L-FLG and S-FLG increased
by a factor of 2.5 and 16, respectively, when natural organic matter
(NOM) was added in the exposure suspension. While the L-FLG mainly
accumulated in the gut of adult zebrafish, the S-FLG was found in
both the gut and liver after exposure with or without NOM. Strikingly,
the S-FLG was able to pass through the intestinal wall and enter the
intestinal epithelial cells and blood. The presence of NOM increased
the quantity of S-FLG in these cells. Exposure to L-FLG or S-FLG also
had a significantly different impact on the intestinal microbial community
structure
Multiple Method Analysis of TiO<sub>2</sub> Nanoparticle Uptake in Rice (<i>Oryza sativa</i> L.) Plants
Understanding the translocation of
nanoparticles (NPs) into plants
is challenging because qualitative and quantitative methods are still
being developed and the comparability of results among different methods
is unclear. In this study, uptake of titanium dioxide NPs and larger
bulk particles (BPs) in rice plant (<i>Oryza sativa L</i>.) tissues was evaluated using three orthogonal techniques: electron
microscopy, single-particle inductively coupled plasma mass spectroscopy
(spICP-MS) with two different plant digestion approaches, and total
elemental analysis using ICP optical emission spectroscopy. In agreement
with electron microscopy results, total elemental analysis of plants
exposed to TiO<sub>2</sub> NPs and BPs at 5 and 50 mg/L concentrations
revealed that TiO<sub>2</sub> NPs penetrated into the plant root and
resulted in Ti accumulation in above ground tissues at a higher level
compared to BPs. spICP-MS analyses revealed that the size distributions
of internalized particles differed between the NPs and BPs with the
NPs showing a distribution with smaller particles. Acid digestion
resulted in higher particle numbers and the detection of a broader
range of particle sizes than the enzymatic digestion approach, highlighting
the need for development of robust plant digestion procedures for
NP analysis. Overall, there was agreement among the three techniques
regarding NP and BP penetration into rice plant roots and spICP-MS
showed its unique contribution to provide size distribution information
Correction to Copper Oxide Nanoparticle Mediated DNA Damage in Terrestrial Plant Models
Correction
to Copper Oxide Nanoparticle Mediated DNA
Damage in Terrestrial Plant Model
Quantification of Carbon Nanotubes in Environmental Matrices: Current Capabilities, Case Studies, and Future Prospects
Carbon
nanotubes (CNTs) have numerous exciting potential applications
and some that have reached commercialization. As such, quantitative
measurements of CNTs in key environmental matrices (water, soil, sediment,
and biological tissues) are needed to address concerns about their
potential environmental and human health risks and to inform application
development. However, standard methods for CNT quantification are
not yet available. We systematically and critically review each component
of the current methods for CNT quantification including CNT extraction
approaches, potential biases, limits of detection, and potential for
standardization. This review reveals that many of the techniques with
the lowest detection limits require uncommon equipment or expertise,
and thus, they are not frequently accessible. Additionally, changes
to the CNTs (e.g., agglomeration) after environmental release and
matrix effects can cause biases for many of the techniques, and biasing
factors vary among the techniques. Five case studies are provided
to illustrate how to use this information to inform responses to real-world
scenarios such as monitoring potential CNT discharge into a river
or ecotoxicity testing by a testing laboratory. Overall, substantial
progress has been made in improving CNT quantification during the
past ten years, but additional work is needed for standardization,
development of extraction techniques from complex matrices, and multimethod
comparisons of standard samples to reveal the comparability of techniques
Agglomeration of <i>Escherichia coli</i> with Positively Charged Nanoparticles Can Lead to Artifacts in a Standard <i>Caenorhabditis elegans</i> Toxicity Assay
The
increased use and incorporation of engineered nanoparticles
(ENPs) in consumer products requires a robust assessment of their
potential environmental implications. However, a lack of standardized
methods for nanotoxicity testing has yielded results that are sometimes
contradictory. Standard ecotoxicity assays may work appropriately
for some ENPs with minimal modification but produce artifactual results
for others. Therefore, understanding the robustness of assays for
a range of ENPs is critical. In this study, we evaluated the performance
of a standard <i>Caenorhabditis elegans</i> (<i>C. elegans</i>) toxicity assay containing an <i>Escherichia coli</i> (<i>E. coli</i>) food supply with silicon, polystyrene, and
gold ENPs with different charged coatings and sizes. Of all the ENPs
tested, only those with a positively charged coating caused growth
inhibition. However, the positively charged ENPs were observed to
heteroagglomerate with <i>E. coli</i> cells, suggesting
that the ENPs impacted the ability of nematodes to feed, leading to
a false positive toxic effect on <i>C. elegans</i> growth
and reproduction. When the ENPs were tested in two alternate <i>C. elegans</i> assays that did not contain <i>E. coli</i>, we found greatly reduced toxicity of ENPs. This study illustrates
a key unexpected artifact that may occur during nanotoxicity assays
Agglomeration of <i>Escherichia coli</i> with Positively Charged Nanoparticles Can Lead to Artifacts in a Standard <i>Caenorhabditis elegans</i> Toxicity Assay
The
increased use and incorporation of engineered nanoparticles
(ENPs) in consumer products requires a robust assessment of their
potential environmental implications. However, a lack of standardized
methods for nanotoxicity testing has yielded results that are sometimes
contradictory. Standard ecotoxicity assays may work appropriately
for some ENPs with minimal modification but produce artifactual results
for others. Therefore, understanding the robustness of assays for
a range of ENPs is critical. In this study, we evaluated the performance
of a standard <i>Caenorhabditis elegans</i> (<i>C. elegans</i>) toxicity assay containing an <i>Escherichia coli</i> (<i>E. coli</i>) food supply with silicon, polystyrene, and
gold ENPs with different charged coatings and sizes. Of all the ENPs
tested, only those with a positively charged coating caused growth
inhibition. However, the positively charged ENPs were observed to
heteroagglomerate with <i>E. coli</i> cells, suggesting
that the ENPs impacted the ability of nematodes to feed, leading to
a false positive toxic effect on <i>C. elegans</i> growth
and reproduction. When the ENPs were tested in two alternate <i>C. elegans</i> assays that did not contain <i>E. coli</i>, we found greatly reduced toxicity of ENPs. This study illustrates
a key unexpected artifact that may occur during nanotoxicity assays
Separation, Sizing, and Quantitation of Engineered Nanoparticles in an Organism Model Using Inductively Coupled Plasma Mass Spectrometry and Image Analysis
For
environmental studies assessing uptake of orally ingested engineered
nanoparticles (ENPs), a key step in ensuring accurate quantification
of ingested ENPs is efficient separation of the organism from ENPs
that are either nonspecifically adsorbed to the organism and/or suspended
in the dispersion following exposure. Here, we measure the uptake
of 30 and 60 nm gold nanoparticles (AuNPs) by the nematode, Caenorhabditis elegans, using a sucrose density gradient
centrifugation protocol to remove noningested AuNPs. Both conventional
inductively coupled plasma mass spectrometry (ICP-MS) and single particle
(sp)ICP-MS are utilized to measure the total mass and size distribution,
respectively, of ingested AuNPs. Scanning electron microscopy/energy-dispersive
X-ray spectroscopy (SEM/EDS) imaging confirmed that traditional nematode
washing procedures were ineffective at removing excess suspended and/or
adsorbed AuNPs after exposure. Water rinsing procedures had AuNP removal
efficiencies ranging from 57 to 97% and 22 to 83%, while the sucrose
density gradient procedure had removal efficiencies of 100 and 93
to 98%, respectively, for the 30 and 60 nm AuNP exposure conditions.
Quantification of total Au uptake was performed following acidic digestion
of nonexposed and Au-exposed nematodes, whereas an alkaline digestion
procedure was optimized for the liberation of ingested AuNPs for spICP-MS
characterization. Size distributions and particle number concentrations
were determined for AuNPs ingested by nematodes with corresponding
confirmation of nematode uptake <i>via</i> high-pressure
freezing/freeze substitution resin preparation and large-area SEM
imaging. Methods for the separation and <i>in vivo</i> quantification
of ENPs in multicellular organisms will facilitate robust studies
of ENP uptake, biotransformation, and hazard assessment in the environment