Page 473 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

450 Potential Impacts of Nanomaterials

to a chemical suggests the chemical has antimicrobial activity. Growth
inhibition tests use plating methods or spectrophotometric methods to
determine the amount of growth in a culture. Some environmental con-
taminants can be mutagenic and cause changes in the genetic code of
receptor organisms. These include carcinogens that affect somatic cells,
such as benzene, and teratogens that affect germ cells, such as
thalidomide.
To examine a compound’s potential mutagenicity, several assays deter-
mine the compound’s ability to damage microbial DNA. Most of the tests,
such as the Ames test and Mutatox test, look at the frequency of muta-
tions caused by the chemical that restore some previously damaged func-
tion to the microbe. Table 12.2 summarizes some of the more popular
mutagenicity tests available, along with other common microbial assays
that are used to assess the general toxicity of a compound. However,
only a few of these assays have been applied to nanomaterials [24].
Developmental toxicity tests for eukaryotic, multicellular organisms
are also commonly used to identify xenobiotics that may alter ecosys-
tems. These tests analyze impacts on the embryonic development of
higher order organisms. Full life cycle chronic toxicity tests that expose
all life stages of an organism to a toxicant can be quite long and costly.
Short-term acute developmental toxicity tests, however, can be used to
predict chronic effects with far less time and cost, allowing for broader
evaluation of factors that influence toxicity. Furthermore, due to the
higher sensitivity of organisms in their embryonic stage than during

TABLE 12.2 Selected Bacterial Toxicity Assays
Test type Test name Test principle Reference
Enzyme MetPAD & Colorimetric assay for 25
MetPLATE -galactosidase activity
MitoScan Monitor electron transfer 26
inhibition by NADH
production or consumption in
submitochondrial particles
Growth Pseudomonas Monitor turbidity of cell 27
inhibition putida culture
Bioluminescent Microtox Monitor luminescence of www.azurenv.com
Vibrio fischeri
Mutagen Ames Look for reversion of 28, 29
mutations in Salmonella
typhimurium restoring ability
to produce histidine
Mutatox Look for V. fischeri with www.azurenv.com
increased luminescence