Although the current market for nanomaterials is small and their concentration may not
be high enough in the environment to cause human health or environmental problems,
this market is increasing rapidly and the discharge of nanomaterials into the environment
in the near future could be significant as manufacturing costs decrease and new
applications are discovered. The accumulation of nanomaterials in cells may have
significant environmental and human impacts. At present, however, very little is known
about the fate, transport, transformation, and toxicity of these man-made nanomaterials in
the environment. The objectives of this research project are to: characterize the
fundamental properties of nanomaterials in aquatic environments; examine the
interactions between nanomaterials and toxic organic pollutants and pathogens (viruses);
evaluate the removal efficiency of nanomaterials by drinking water unit processes;
and, test the toxicity of nanomaterials in drinking water using the cell culture model
system of the epithelium. This study considers the physical, chemical, and biological
implications of nanomaterial fate and toxicity in systems that will provide insight into the
potential for nanomaterials to be present and to cause health concern in treated drinking
water.
Characterization of commercial metal oxide nanoparticles (powder or liquid suspensions)
by scanning electron microscopy or by dynamic light scatter after placing these particles
in water indicates that these nanomaterials are aggregated when purchased and remain
aggregated in solution. Attempts to disaggregate the nanomaterials in water using
sonication, pH adjustment, solvent addition, or surfactant addition had minimal effect on
mean particle sizes. As a consequence, the metal oxide nanoparticle aggregates range in
size from 500 to 10,000 nm in diameter at concentrations of 10 mg/L of nanoparticles.
Thus fate and transport of metal oxide nanoparticles may actually depend more on
aggregation kinetics than behavior of discrete nanoparticles in water. To address the fate
of discrete nanoparticles our team has synthesized metal oxides with mean particle
diameters of ~ 10 nm, which are not initially aggregated and will be used in future tests.
Experiments have been conducted that simulate drinking water treatment (jar tests with
coagulation, flocculation, sedimentation, and filtration). Both metal coagulants (alum,
ferric) and salt (MgCl<sub>2</sub>) have been used to destabilize or otherwise aggregate metal oxide
nanoparticles. Experiments have included titanium, iron, and aluminum oxide
nanoparticles, and cadmium quantum dots. Overall, coagulation and sedimentation alone
remove 40 to 60 percent of these nanoparticles, and filtration (0.45 µm or 3 µm pore
diameter) removes an additional 50 to 80 percent. Ten to 30 percent of some initial
nanoparticles remain, however, after this simulated water treatment test.
Trans-Epithelial Electrical Resistance (TEER) measurements have been made using
Caco2 BBe (human intestinal cells) grown and maintained with Dulbecco's Modified
Eagle Medium (DMEM) media supplemented with 10 percent fetal bovine serum,
penicillin/ streptomycin/ fungizone, and transferrin. Extensive optimization of growth
conditions were undertaken. Preliminary experiments indicate a decrease of 10 to 50
percent in TEER within 1 hour after application of metal oxide nanoparticles.
Spectroscopic investigations of the cells are underway to determine the mechanism for
change in TEER. Includes 57 references, figure.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 320 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 8 |
| Published : | 06/01/2006 |
