Biomedical Engineering Reference
In-Depth Information
Biosensors are classified according to the bioreceptor used or biological process
involved such as biocatalytic (enzyme-based)
104,126-133
immunologic (Ab-antigen
based)
126,127,
132-137
or DNA (nucleic acid-based)
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sensors. Biosensors that
use NMs are called nanosensors.
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Nanosensors are designed in various novel
ways using the enhancement of performance through the various properties of
the NMs employed.
148,151,152
Recent advances in materials science and synthetic
chemistry have made it possible to produce high-quality NMs in the form of NPs
(nanotubes, nanorods, nanospheres, nanowires, nanoarrays, and their compos-
ites)
153,154
that have been used for the development of biosensors
140,141,148,150,155-159
because of their significant advantages over microscale and bulk materials that
include (a) size-tunable properties, (b) large surface-volume ratio, (c) shape-
dependent properties, (d) lower energy consumption, (e) miniaturized bisensors,
and (f) low cost. These nanosensors are discussed in greater detail in Chapter 4.
3.3.2 Covalent Conjugation of Biomolecules to NPs
Covalent attachment of a biorecognition moiety to a functionalized NM is one
of the more widely used strategies for converting an NM for a specific applica-
tion.
139-151,160
For example, tumor cells that are circulating in the blood can be
tagged and diagnosed using this approach. Aguilar et al.
161-164
exhibited specific
targeting of breast cancer cell lines SK-BR3 using QDs that were functional-
ized with Abs against human endothelial receptors (AbHER2) forming QD-Ab.
HER2 is a surface coating protein that is overexpressed in breast cancer cells.
SK-BR3 breast cancer cells that were exposed to QD-Ab, appeared fluorescent
under a UV illuminated microscope (
Figure 3.5
) making the imaging of the
cells under a microscope a lot easier. Furthermore, cells that are specifically
stained with biomolecule-functionalized QDs offer advantages over those that
FIGURE 3.5
Digital photograph of SK-BR3 cells exposed to QD-anti-EpCAM. The QDs were
~8 nm in diameter emitting at 620 nm.
Courtesy of Ocean NanoTech (For color version of this
figure, the reader is referred to the online version of this topic)
