THRUST AREA: NanoEnvironment
Nanomaterials in the Environment
Team: Tara Sabo-Attwood, Thomas Chandler, Lee Ferguson, John
Ferry, Gene Feigley, Alan Decho, Lee Newman, Shosaku Kashiwada
Although the use of nanomaterials may allow for significant advances in
science and technology, assessment of potential negative health and
environmental impacts on humans, non-human biota, and ecosystems is
imperative. The same properties that make these particles desirable, may
also contribute to their toxic potential. This focus group is studying
the potential toxic effects that various nanoparticles have on humans,
microbial communities, and aquatic ecosystems. This is an
interdisciplinary effort which requires alliances between chemists,
physicists, biologists, toxicologists, and microbial ecologists, among
others. The focus of our research efforts are described below.
Subproject #1: Pulmonary toxicity of nanomaterials
Project leaders: Tara Sabo-Attwood and Gene Feigley
In humans, the dominant route of exposure is suspected to occur via
direct inhalation, both in the workplace where these particles are
manufactured and used, and from the environment contaminated with
particles released from anthropogenic and natural sources.
Health-effects studies of air exposure to nanomaterials will require
design of novel inhalation toxicology facilities and filtration
technologies not available presently in the United States. Our group is
uniquely qualified to design, build and test a small-scale prototype
facility to assess aerosol generation, fate and transport. Construction
of this prototype will lead to the development of inhalation exposure
protocols for relevant animal models to assess the toxicological impacts
of nanoparticles. In addition, we have already establishd complimentary
in vitro studies that reveal toxic effects of SWCNT in human lung cells,
and are currently exploring the molecular mechanisms responsible for
this toxicity.
(picture coming)
Subproject #2: Environmental fate, transport and toxicity of
nanomaterials in aqueous systems
Project leaders: Tom Chandler, Lee Ferguson, Shosaku Kashiwada
Project Focus:
Synthesis of unique radioisotope-labeled nanomaterials for
toxicological, fate and environmental transformation studies
SWNT fate in aquatic/sedimentary systems is still largely
under-explored. The USEPA and NIEHS have expressed high interest in USC
developing a repository of pure, radio-labeled carbonaceous
nanomaterials for national environmental toxicology and chemistry uses.
With our collaborator Research Triangle Institute, Inc. we have custom
synthesized single- and multi- walled carbon nanotubes, fullerenes, and
various inorganic materials. We are using these materials to perform
experiments aimed at uptake/bioaccumulation and linked acute/chronic
toxicity of SWNTs in at least two model invertebrate systems, fish and
marine invertebrates (copepods). The 14C-SWNT materials will also be
used to study particulate sorption, transport in porous media, and bio/phototransformation
in a laboratory setting. The 14C-SWNT materials will be used to study
particulate sorption, transport in porous media, and bio/phototransformation
in a laboratory setting.
Images (C) and (D) show light level and false color confocal
microscopic images of an adult copepod with multiple ingested pure SWNT
aggregates traveling through its gut. Images (E) and (F) show
light-level and false-color confocal microscopic images of adult copepod
fecal pellets with compacted pure SWNT bundles. Copepod fecal pellets
are a significant portion of the estuarine sediment fabric.
Subproject #3:
Microbial applications and degradation of nanomaterials
Project leaders: Alan Decho, Sean Norman, John Ferry
Biofilms consist of bacteria cells attached to a surface that produce a
large network of extracellular polymeric secretions (EPS). In doing so,
bacterial cells are able to protect themselves against antimicrobial
agents, and manipulate their local environment. Biofilms commonly occur
in natural and engineered environments. However, their presence often
incurs multibilllion dollar costs for hospitals (e.g. most
hospital-acquired infections are biofilms), industry (e.g. cause metal
corrosion and biofouling, reduce heat transfer efficiency), potable
water system maintenance (i.e. protect pathogenic bacteria against
chlorination), as well as being important in natural environments. Our
research focuses on using nannoparticles to detect and monitor biofilms,
study how the nanoparticles are captured and sequestered, and determine
if the bacteria degrade these particles in various settings.
We have three foci
to our studies:
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Biofilm
Nanosensors: Understanding biofilm processes, and controlling their
costly effects is important has important economic, health, and
environmental implications. The development of specific Nanosensors
for monitoring bacterial processes within biofilms is an important
step in the in-situ detection and monitoring of biofilm processes.
Our studies will strive to develop specific sensors that can be
‘captured’ by a biofilm, then provide important
physical/chemical/metabolic information regarding processes
occurring within the biofilm.
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Capture and
Sequestration of NanoParticles by Biofilms. Bacterial biofilm are an
efficient filter for particulates, colloids and dissolved molecules.
They are likely important in the capture and concentration of
nanoparticles under different Environmental conditions. We will
strive to: 1) understand how biofilms sequester nanoparticulates,
and 2) manipulate biofilms to enhance capture efficiency.
-
Biofilm Test Systems:
This phase involves the development of biofilm culture systems that
accurately mimic natural biofilm populations. Such systems will be
coupled to CSLM, Raman/CSLM, and other analysis instrumentation for
precise testing of antimicrobial approaches on living and engineered
nanosurfaces. Microbial interactions and degradation
This project will be directed at determining the influence of
nanomaterials on environmental microbial activity. Nanomaterials
have unique antimicrobial properties that may be exploited in
environmental disinfection and/or infection control. There are also
therapeutic applications for this research relative to artificial
implants, prostheses, etc.
Specific Goals: This exploratory research will be done in
conjunction with Prof. Alan Decho and Dr. Sean Norman from the
Department of Environmental Health Sciences. Particular attention
will be paid to questions such as: Do the materials in question
support or inhibit the formation of biofilm communities? Are
microbial communities capable of affecting the structure of
associated nanomaterials (i.e., metabolically transforming them)? Do
nanomaterials exert selective population pressure on microbial
communities (i.e. selectively targeting one particular type of
microbe vs another in mixtures)?
We will develop ‘nanoprobes’ (fluor-, SERS-based) for biofilm
investigations in environmental studies. We will also develop/build
biofilm flow-through cells and bioreactors for live culturing, and
observation, of biofilms in the presence/absence of nanomaterials
using our new confocal (CSLM) and Raman-confocal systems in ENHS.
 |
Upper Image: Confocal scanning laser
microscope (CSLM) image of a natural bacterial biofilm showing its
capability to capture very small particles of calcium carbonate
(CaCO3), ranging in size from several micrometers to less than 40 nm
(not visible). Capture of particles is related to the sticky matrix
of EPS (extracellular polymers).
Lower Image: The EPS consists of a fine mesh-like network of
polymeric molecules, shown in this atomic force microscopy (AFM)
image. Thus, the biofilms may be an efficient natural device for
the capture and concentration of nanoparticles in the environment |
Subproject #4
Photocatalysis
Project leaders: John Ferry, Tom Vogt
Project Focus:
Development of nanostructured materials with applications for
environmental modification or remediation is the focus of this project.
We are primarily interested in developing mixed metal oxide visible
light activated photocatalysts for effecting sunlight activated
oxidation in the aqueous phase. The materials focus will be active
catalysts (nanoparticulate metal oxides) that engage in direct electron
transfer with substrates and passive materials that may exhibit
catalytic properties by promoting close association (such as various
nanocarbons). We will monitor the degradation of catalytically active
nanomaterials in environmental matrices, using microscopic and molecular
techniques. We will assay the catalytic activity of the material during
degradation, which is an exploratory evaluation of the structure
activity relationship. We will assay the physico-chemical behavior of
the material upon exposure to environmental conditions (e.g.
aggregation, adsorption of "poisons" that affect catalyst activity,
etc). We will explore application venues for materials that are
effective photoactivated oxidants (drinking water and surface
disinfection, biomedical applications, etc).
Subproject #5
Plant Interactions with Nanoparticles
Project leaders; Lee Newman, Tara Sabo-Attwood, Jason Unrine, Cathy
Murphy
Project focus
Plant uptake and response to nanoparticles will have significance on
many levels. First and foremost is to understand the parameters of plant
uptake of the particles; what types (i.e., chemical composition) of
particles are taken up, is there a size limit or shape preference, do
the chemicals used to cap the particles impact uptake? Could plant
compounds affect the bioavailability of particles in a natural system?
In independent studies, we have already exposed the model plant,
Nictoianna xanthi, to several different sized gold nanosphere, gold
nanosheres with different capping chemicals, and silver nanospheres.
Through simple light microscopy we have identified spheres of 3-5nm
within the vascular tissue of the roots of the plants, and aggregation
of larger spheres on the outside of the roots. We have observed enhanced
precipitation of the particles when exposed to root exudates. We have
also had a plants analyzed by one the using the beam lines at Brookhaven
National Laboratory’s Synchrotron Light Source, and had XANES collected
for selected areas of the plants analyzed. We found that the particles
were retained as gold, and not gold salts within the plant, and that the
pattern of accumulation differed within the plant tissues. |
