Biomedical Engineering Reference
In-Depth Information
were electroplated into the pores of an alumina template. The template was then subjected to
treatment by a strong base. This released the nanoparticles with dimensions of 6 nm 250 nm.
Sha et al. (2007) report that their Cy5-terminated HCV oligo probes emitted a strong SERS spec-
trumwhen assembled on the nanobarcodes. The SERS spectrum emitted from a pure Cy5 is simi-
lar to that emitted from a Cy5-HCV probe. The authors report that upon binding to the target
sequence a significant decrease in the SERS signal is measured. When a target is present, the
SERS signal is relatively unchanged. These authors were careful to note that the SERS signal
was not due to other causes. For example, the authors confirmed that the oligo remained attached
to the NBC, and the dye-labeled oligo was not stripped from the surface of the particle.
Sha et al. (2007) point out that the dual-modality of their technique is that when the HCV
target is present (a) the SERS signal decreases, and (b) the fluorescence signal increases. This
dual-modality, the authors report, could serve as a built-in control for rapid diagnostic tests.
Also, their NBC substrates could be used in multiplex testing, wherein different analytes
(targets) may be detected simultaneously.
The authors have demonstrated the strong inverse correlations between their SERS and fluo-
rescence detection mechanisms by adding different concentrations of the target to the NBC-
SERS beacon. The authors conclude that their technique clearly shows the possibility of
developing a multiplexed SERS beacon using a Raman microscope with reflectance and fluo-
rescence capabilities. Their assay should be able to detect pathogens, and be useful in moni-
toring (a) the environment, (b) health-care, and (c) bio- and chemical terrorism. Additional
advantages are that their method possesses multiplexing capabilities and is label-free.
5.8 Nanotube-Based Biosensor for the Detection of Disease-Specific
Autoantibodies in Human Serum ( Drouvalakis et al., 2008 )
Drouvalakis et al. (2008) have recently developed a peptide-coated nanotube biosensor for
the detection of rheumatoid arthritis (RA)-specific autoantibodies. The authors immobilized
an RA-specific citrulline-containing peptide to functionalized SWCNT (single-walled carbon
nanotubes) on a QCM (quartz crystal microbalance) sensing crystal. Using QCM sensing, the
authors detected the antibody binding from RA patients' serum using their nanotube-based
biosensor. They report that their nanosensor is sensitive enough to detect in the femtomol
range. Besides, their nanosensor is more sensitive than standard ELISA and current micro-
array assay methods. For example, they were able to detect 30% more (34.4 and 37.5) of
anti-citrullinated peptide from RA-patients using ELISA and microarrays, respectively. The
authors report that their nanosensor may be used for both diagnostic and research purposes.
Drouvalakis et al. (2008) report that SWCNTs (single-walled carbon nanotubes) exhibit elec-
tronic, mechanical, and optical properties ( Kroto et al., 1985 ; Lijima, 1991; Ebbesen and
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