Biomedical Engineering Reference
In-Depth Information
nanostructures, and the mechanics (e.g., adhesion force, elasticity) of mammalian cells at a nanoscale
resolution under physiological or near-physiological conditions. An atomic force microscope can be
used to study the mechanics of cells under the influence of nanoparticles. Wu et al. (2012) applied
atomic force microscopy to reveal insights on the toxic effects of diesel exhaust particles on vas-
cular endothelial cells at the single-cell level to understand the biophysical properties of the cells.
Atomic force microscopy was utilized in two different strategies in this experiment: (1) to measure
the mechanical properties of the cell, such as Young's modulus and adhesion force in the growth
medium and (2) for topography and membrane visualization, cells were fixed and imaged.
5.4
BIOSENSORS FOR NANOTOXICITY BIOMARKER DETECTION
5.4.1 B
ackgrouNd
The rapid growth of the nanotechnology industry has led to a large-scale production and applica-
tion of engineered nanomaterials, which are used not only in medicine and industry, but also in
various consumer products such as food products, textiles, sunscreens, and cosmetics (Pujalte
et al. 2011). While, on the other hand, the increased utilization of nanomaterials could affect
human health and the environment due to increased exposures (Colvin 2003; Chow et al. 2005;
Owen and Depledge 2005). The current knowledge is limited to the potential health effects caused
by nanomaterials; however, it shows that they may cause adverse effects at the routes of exposure
such as the skin, gastrointestinal tract, and lungs (Chow et al. 2005; Xia et al. 2009). Furthermore,
some nanomaterials made of certain metals may have genotoxic or carcinogenic effects. One of the
most discussed mechanisms behind the health effects induced by nanomaterials is their ability to
enhance the generation of reactive oxygen species (ROS), causing oxidative stress, DNA damage
(MacNee and Donaldson 2003; Valko et al. 2005, 2006; Durocher et al. 2009; Jia et al. 2009; Jones
and Grainger 2009; Landsiedel et al. 2009; Moller et al. 2010; Singh et al. 2009), and unregulated
cell signaling, which eventually leads to changes in cell motility, apoptosis, and carcinogenesis
(Kasai et al. 2001; Kasai 2002; Song et al. 2012). Therefore, there is a great need for setting up
reliable methods to assess the potential toxicity of the nanomaterials with short deadlines and rea-
sonable costs, ensuring their compatibility for medical applications and for the safety of the envi-
ronment. While most reliable methods for toxicity evaluation rely on costly,
in vivo
experiments,
in vitro
assays present a promising screening method. Cell cultures offer a useful prescreening
method to assess the toxicity of various external agents on cells.
5.4.2 c
oMMoN
M
ethods
for
N
aNotoxIcIty
a
ssessMeNt
An assortment of assays is used to assess the toxic effects of nanomaterials
in vitro
. These assays
can be generally classified into three groups based on their objects of measurement, that is, cell
viability/proliferation, direct/indirect intracellular ROS levels, and genomic markers.
5.4.2.1 Cell Viability/Proliferation Assay
Traditional
in vitro
cell viability/proliferation or cytotoxicity assays, for the measurement of cellu-
lar viability and proliferation, are used in the current nanotoxicity studies. These assays include the
Alamar Blue assay, which incorporates a fluorometric/colorimetric growth indicator based on the
detection of metabolic activity (Fahmy and Cormier 2009; Jones and Grainger 2009; Poonam et al.
2011); the Trypan Blue assay, where cells with an intact membrane are able to exclude the Trypan
Blue dye (Karlsson et al. 2008; Bhattacharya et al. 2009; Jones and Grainger 2009; Hillegass et al.
2010; Poonam et al. 2011); the Neutral Red assay, based on the ability of viable cells to incorporate
and bind the supravital dye, neutral red, in the lysosomes (Pujalte et al. 2011; Saquib et al. 2012);
formazan-based assays (MTT, MTS, and WST), which are used for the detection of various stages
in the apoptosis process of cells (Lai et al. 2008; Jones and Grainger 2009; Napierska et al. 2009;
