Biomedical Engineering Reference
In-Depth Information
compared with the single Au NPs. They further add that their Au NPs aggregates are sensi-
tive enough to discriminate single mismatches. They were also able to confirm the presence
of cross-linked Au aggregates using light-scattering spectroscopy (
Du et al., 2006
).
Finally,
Li et al. (2009)
affirm that their aggregate Au NP optical detection method exhibits
high sensitivity, and that their diagnostic device has the potential to be effective, especially
for small clinics in developing countries where resources are inherently limited.
5.3 High-Performance Multiplexed Determination of Proteins:
Determinations of Cancer Biomarkers in Serum and Saliva
Using QD Bioconjugate Labels (
Jokerst et al., 2009
)
Jokerst et al. (2009)
have recently developed a multiplexed biosensor for detecting the
three cancer biomarkers, carcinoembryonic antigen (CEA), cancer antigen 125 (CA125), and
Her-2/Neu (C-erb-2). They integrated semiconductor nanoparticle QDs into a molecular
microfluidic biosensor. They were able to use this biosensor for both serum and whole saliva
specimens. Their nano biochips used a fluorescence transduction signal with QDs-labeled
detecting antibody in combination with antigen capture by a microporous agarose bead array.
They used a sandwich type immunoassay. The authors report that their QD biosensor yields (a)
a signal amplification by a factor of 30 when compared with standard molecular fluorophores,
and (b) a decrease in the limit of detection (LOD) by approximately two orders of magnitude
(0.02 ng/ml; 0.11 pM CEA) relative to ELISA (enzyme-linked immunosorbent assay).
Jokerst et al. (2009)
point out that the detection of cancer (protein) biomarkers exhibits prom-
ise in the screening, treatment, metastasis evaluation, and determining the response to phar-
macologic intervention (
Lee et al., 2008
).
ACS (2008)
reports that tests such as PAP smear
and PSA are efficient screening tools for cancer detection in asymptomatic individuals.
Sofer
et al. (2006)
mention that breast cancer detection tests based on Her-2/Neu and alpha-fetoprotein
tests for testicular cancer have also been developed.
Das and Bast (2008)
report the devel-
opment of protein biomarkers to monitor colon (by CEA, carcinoembryonic antigen) and
ovarian cancer (by cancer antigen 125 (CA125).
Harris et al. (2007)
are of the opinion that identifying at-risk individuals for cancer frequently
requires four or more biomarkers. ELISA-based methods are not easily multiplexed. Further-
more,
Bhasin et al. (2008)
report that the current LOD values for cancer biomarker detection
during cancer in its nascency and diagnostic decision values are close to each other;
Jokerst
et al. (2009)
remark that this makes it difficult to help evaluate patients during the early
stages of cancer development. The authors also point out that POC (point-of-care) systems
further facilitate early, routine and frequent access to diagnostic test results. They further
report that POC methods have started using saliva as a diagnostic medium (
Wong, 2008
).
