Civil Engineering Reference
In-Depth Information
While many assays are available for toxicity screening of small organic
molecules, it remains to be seen whether all possible toxicology paradigms
can be covered with already existing assays as ENM-triggered toxicity has
the potential to follow different paradigms than small molecule toxicity.
Another argument in favor of custom development of novel assays is their
usability for testing the hypothesis of the mode of action of ENM toxicity.
To accomplish this, novel assay platforms are needed for the evaluation of
ENMs in environmentally relevant systems such as, e.g., algae or other
aquatic species, which will require tailoring of assays to ENM toxicity. The
strength of plate reader based assays is their speed. HCS-based assays can
be slow to read on the imaging systems, so at times a balance between
information required and the needed acquisition speed has to be found.
Importantly, it has to be noted that each assay has its artifacts and other
liabilities. This is especially true for nanotoxicology where it is very common
for, e.g., dyes used in an assay to interact with a given MNM leading to
unreliable or even false results. Table 7.4 gives an overview of MNM toxicity
paradigms, corresponding assays/readouts as well as possible interference
of the MNM with the assay readout. Typically, it is advisable to confi rm
results on toxic MNMs with another assay, which uses a different readout
paradigm in order to exclude artifacts.
While, for example, some toxicity assays rely on cell-free systems such as
detection of ROS generation (Gabriel
et al.
, 1997) by the MNM using a
fl uorescent dye or co-incubation of an MNM with an enzyme and sub-
sequent measurement of enzymatic activity, it is the cell-based assays which
offer the most insight into MNM toxicity as a living cell contains all poten-
tial targets for MNM toxicity (Damoiseaux
et al.
, 2011).
As the lowest functional unit of an organism, cells represent the ultimate
target for an intruding MNM and from a biochemical perspective the cells
respond to foreign materials in essentially similar ways to that of the whole
organism. Although primary cell lines are ideal candidates for toxicity
screening, the cells are frequently not available in suffi cient quantities for
use in HTS, hence cell lines are used. A cell-based assay in the context of
nanotoxicity can be regarded as an analytical procedure that assesses the
biological outcome resulting from the interaction of nanomaterials with a
given cell. However, the manifestation of biological outcome is generally
faster in a cell-based
in vitro
system (often in the order of minutes to hours)
than
in vivo
, thus providing a rapid readout of MNM toxicity. In order to
achieve the true toxicological signifi cance of a cellular injury response, it is
necessary to correctly pick the cell line type and
in vitro
end point/readout
in order to generate high quality information about the potential impact of
the nanomaterial.
The toxicity profi le of NMs may vary from one cell type to another
because of the possible difference in the cellular uptake and processing of
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