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Brian Peebles |
Education
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Current Areas of Research
In collaboration with the Waldman group in the Department of Pathology, we are determining the physical and chemical basis of the pulmonary toxicity of manufactured nanoparticles. Since people employed in the nanotechnology industry are exposed to nanoparticles on a daily basis, it is important to address the toxicity of nanoparticles from the perspective of industrial hygiene.
Current regulations generally set a TLV, or threshold limit value for nuisance dust in the workplace at 3.5 milligrams per cubic meter of air. Particles 2.5 micrometers in diameter or smaller are considered one category of particles, "inhalable." The category only accounts for the fact that particles 2.5 microns in diameter or smaller are easily inhaled. It does not account for the dramatic increase in specific surface area, or surface area per gram of particles, that can make nanoparticles more toxic than micron-sized particles since the surface contains reactive functional groups.
Particles
are examined physically by BET surface area measurement, scanning
electron microscopy and dynamic light scattering, to determine primary
particle size and aggregation and agglomeration characteristics. Below
are scanning electron micrographs of Degussa Flammruss 101
and
Printex 90 carbon black, Zeolyst CBV100 sodium zeolite Y, and Degussa
Aeroxide P25 titanium dioxide, from left to right.
Chemical
properties of particle surfaces are being examined by X-ray
photoelectron spectroscopy (XPS), diffuse reflectance infrared Fourier
transform spectroscopy (DRIFTS), and electron paramagnetic resonance
spectroscopy (EPR). Results will show the presence of free
radicals and reactive oxygen-containing functional groups of biological
relevance. Below is an EPR spectrum showing trapped hydroxyl
free
radicals resulting from Fenton chemistry, which is redox chemistry of
iron ions in the presence of hydrogen peroxide. The Fenton reaction
causes oxidative stress in cells, and can happen at the surfaces of
particles that contain iron or in biological media that contains iron
ions extracted from particle surfaces.
Chemical
properties of nanoparticles are being correlated with their toxicity in
human monocyte-derived peripheral blood macrophages, measured by
oxidative stress assays. As phagocytosis occurs, reactive
oxygen
species are released. The degree of oxidative stress is
measured
by assaying oxidative stress indicators like tumor necrosis factor
alpha and intercellular adhesion molecule 1, among many others.
Gene arrays can be used to determine whether oxidative stress
has
damaged DNA. The pictures below are phase contrast micrographs of
chemically
treated carbon particles and coal fly ash being digested by human
monocyte derived macrophages.
Reference
for the picture above: Robert Kristovich, Deborah A. Knight,
John
F. Long, Marshall V. Williams, Prabir K. Dutta, and W. James Waldman.
Chem. Res.
Toxicol. 2004,
17,
1303-1312.
Publications
Peebles, Brian C.; Setter, Michael P. "Investigation of a new Chelation Ion Chromatography Procedure to Determine the Surface Composition of Powdered Metal Oxides in the Solid State." Journal of Chromatography A 2004, 1039, 13-21.
Recent
Presentations
Peebles,
Brian C. "Investigation
of a new Chelation Ion
Chromatography Procedure to Determine the Surface Composition of
Powdered Metal Oxides in the Solid State." International Ion
Chromatography Symposium, San Diego, CA. September, 2003.
Peebles, Brian C.; Nagy, Amber; Dutta, Prabir K.; Waldman, W. James. "Pulmonary Toxicity of Manufactured Nanoparticles from the Perspective of Industrial Hygiene." The Ohio Nanotechnology Summit, Akron, Ohio, April 24-25, 2007.
Peebles, Brian C.; Nagy, Amber; Dutta, Prabir K.; Waldman, W. James. "Pulmonary Toxicity of Manufactured Nanoparticles from the Perspective of Industrial Hygiene." The Ohio Nanotechnology Summit, Akron, Ohio, April 24-25, 2007.
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