Biomedical Engineering Reference
In-Depth Information
Mandel (1993) and Malamud (2006)
both report that saliva contains biomarkers that offer
information about both oral and systemic disease.
Jokerst et al. (2009)
further affirm that use-
ful genetic and proteomic profile information is also available in the saliva (
Hu et al., 2007;
Oppenheim et al., 2007
).
Hu et al. (2007) and Tan et al. (2008)
concur that saliva testing
minimizes testing antipathy and promotes frequent testing.
Streckfus et al. (2006)
caution,
however, that saliva is more heterogeneous than serum and is not without problems whilst
testing for biomarkers. Furthermore, the expression levels for these disease-related
biomarkers may be expressed at several orders of magnitude less than those expressed in
serum; hence the need for efficient sensing systems which can distinguish between back-
ground noise and target-specific signals.
Jokerst et al. (2009)
report that QD fluorophores exhibit the potential to help minimize or
eliminate these types of problems (
Liu et al., 2008a
).
Sofer et al. (2006)
have listed the
difficulties in linking QDs to bioligands for POC cancer diagnostics. Furthermore,
Resch-
Genger et al. (2008)
point out that the integration of QDs as quantitative imaging tools, espe-
cially with small analyzer platforms, is yet to be demonstrated.
In order that these types of problems may be mitigated new systems are under development
for the early detection of neoplastic diseases (
Ali et al., 2003; Christodoulides et al., 2007;
Weigum et al., 2007
). The
Jokerst et al. (2009)
analysis presents the incorporation of
QDs as detection elements in the NBC biosensors for the quantitative measurement of the
well-characterized cancer biomarkers, CA125, CEA, and Her-2/Neu (C-erB-2).
Jokerst et al. (2009)
claim that a MEMS (micro-electromechanical systems) platform that
includes microfluidics elements and bead containers supports their integrated NBC assay.
The authors used QDs as a detection moiety in their NBC, and their QD-based platform
includes all the components of a sandwich immunoassay, with agarose as a solid phase sup-
port. The capture and detection bodies comprise different clones of monoclonal antibody.
The authors mention that the beads are layered within their NBCs between precision cut
layers of laminate adhesive which facilitate reagent delivery. Their fluorophore conjugated
detection antibody yields the signal that is recorded by a CCD camera. They report that
the fluorescence signal relates directly to the antigen present in a sample.
Jokerst et al. (2009)
explain that for using the QDs in their immunoassay, care was taken to retain
their optical properties, hydrophilicity, and the recognition moiety specificity by linking them to a
recognition element such as an antibody by different covalent and noncovalent strategies. The
QDs were characterized based on background, signal, and nonspecific signal (noise).
Jokerst et al. (2009)
compared the performance of their QDs to traditional fluorophores. They
used Alexa Fluor 488 (AF 488), one of the brightest fluorophores available for this compari-
son. The authors concluded from their experiments that the QDs provide 25 times more
signal compared to that provided by AF 488 at isomolar concentrations.
