Biomedical Engineering Reference
In-Depth Information
tail is analyzed to quantify the induced DNA fragmentation. In this method, Dulbecco's modified
Eagle medium (DMEM) is used as negative control and methyl methane sulfonate (MMS) is used
as alkalyting agent and serves as a reliable positive control [186].
19.9.4.5 DNA Damage
DNA damage in cells is detected using γ-H2AX, a phosphorylated form of H2AX, which forms at
the sites of DNA double-strand breaks [188].
19.9.5 h
Igh
-t
hroughput
s
creeNINg
M
ethod
Recent advances in cell-based assays allow for toxicity and/or efficacy screening of multiple nano-
materials at multiple concentrations with multiple cell lines, simultaneously. This expansion of the
experimental design is practically enabled through the miniaturization and multiplexing of the
experimental apparatus and method by utilization of either ultrasmall 384-well cell culture plates
or nanodrop sample chambers on a chip. The nanodrop assay setup allows for different assays with
suitable detection features (e.g., fluorescence, and luminescence) to be performed in a fraction of
the volume without the cell activation or photometric effects of the culture plate since the cell cul-
ture is performed in a self-contained drop [189]. However, since cells are typically microns in size,
nanodrops do not necessarily capture cells themselves, only fluidic cellular exudates for assay and
analysis. By assaying numerous material types/functionalizations and material concentrations on
numerous cell types, all in parallel, complex interactions between materials and cells may be ascer-
tained through complex data analysis that correlates phenotypes with multiwell plates, cell culture,
detection schemes, and recognition schemes [190].
19.9.6 d
ose
-r
espoNse
a
ssessMeNt
From the preceding section, it becomes obvious that without the use of standard operation proce-
dures (SOPs), results from different studies will be difficult to compare. Dose indication for dose-
response studies presents another problem. Dose-response relationships (relationship between dose,
or level of exposure to a substance, and the incidence and severity of an effect) are more difficult
to assess for NPs because mass per milliliter, which is commonly used for chemicals, may not be
a suitable measure for NPs. It has been suggested to use either surface area or particle number
because toxicity is correlated better with these parameters [191]. None of these measures proved to
be ideal for all NP types and therefore, most studies use mass per volume for dosing. The correlation
of dose and biological response is complicated by the fact that increases in the mass dose do neither
increase the effect observed with lower concentrations nor do they act in the same way. Inhalation
of low doses of TiO
2
NPs affects metabolites in the urine, whereas higher doses cause local effects
in the lung [192].
19.10
APPLICATION OF COMPUTATIONAL APPROACH FOR RISK ASSESSMENT
19.10.1 M
olecular
M
odelINg
M
ethods
The current computational methods show a great potential to predict properties, reactivity, and mech-
anisms of actions for various molecular systems, from small molecules up to large biomolecules.
Quantum chemical calculations and molecular dynamics (MD) simulations can be useful to address
the potential risks associated with nanomaterials. Results from such theoretical calculations might
provide suggestions to experimentalists working in this research field. The knowledge gained from
computational studies involving interactions of NPs with biological systems will be helpful to con-
struct algorithms for assessing the likelihood of toxicity in a variety of natural environments [193].
Computer simulations could be valuable by examining the structure of surfaces and identifing even the
