Biomedical Engineering Reference
In-Depth Information
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FIGURE 1.54
Most potent representatives of the quinone subtypes found effective against the melanoma and leukemia cancer
cell lines in Figure 1.53 are shown. (A) Internal quinone NSC 670762, effective against melanoma; (B) external
quinone NSC648147, effective against leukemia. The quinone ring portion is highlighted by the shaded region in
each compound. Reprinted from McCarthy, J.F., Marx, K.A., Hoffman, P.E., Gee, A.G., O'Neil, P., Ujwal, M.L.,
Hotchkiss, J. (2004). Applications of Machine Learning and High-Dimensional Visualization in Cancer Detection,
Diagnosis and Mangement. In: Umar, A., Kapetanovic, I., Khan, J., eds.
The Applications of Bioinformatics in Cancer
Detection, Ann. N.Y. Acad. Sci.
1020:239-262.
process will also result in an increased precision of processing and component separations,
increased device sensitivity to the analyte, increased overall speed, and lowered cost of the
analysis. Going beyond MEMS to the nanoscale, so-called NEMS devices are being pro-
posed based upon current research characterizing various nanoscale biosensor systems. For
nanoscale structures, exploiting the novel properties exhibited by materials components on
this size scale promises to provide unique sensing mechanisms as well as enhanced sensi-
tivity and robustness of the components. As an example, biosensors using Si nanowire sig-
nal transduction elements have been shown to selectively detect individual virus particles
in solution (183). Figure 1.55a shows schematically how this biosensor works based upon
virus-specific antibodies bound to the Si nanowire surface. Significant and measurable con-
ductance changes occur when a single virus is bound to the nanowire-immobilized anti-
bodies. In panel (b) are shown examples of the biosensor output that demonstrate viral
detection specificity for two antibodies, one specific to influenza type A and the other to
adenovirus, placed on two different Si nanowires. Detection events of average duration 16
s before release of the virus from a given Si nanowire can be seen in the output examples.
Only the correct virus type is bound by its recognition antibody on the appropriate Si
nanowire and is recorded by the biosensor. Single virus detection sensitivity has also been
reported using an antibody biosensor that measures the acoustic energy associated with the
rupture of the virus-antibody complex from the surface of the biosensor platform. This
technique has been termed rupture event scanning and is based upon a novel energy scan-
ning variant of the QCM technique discussed previously (184). The Si nanowire biosensor
system discussed above was also shown to be capable of sensitive DNA detection. By
immobilizing a 12-mer single-stranded recognition probe on the Si nanowire, hybridization
of the complementary strand could be detected from a 25 pM DNA solution and single base
mismatched hybridizations with the 12-mer sequence could also be discriminated (185).
Another example of nanoscale enhancement of biosensor detection sensitivity is in glucose
sensing using carbon nanotubes. Single semiconducting carbon nanotubes exhibit strong
luminescence in the near infrared. Electroactive mediators, such as Fe(CN)
6
3
, irreversibly
bind to the nanotubes and quench the light emission after photoexcitation. When Fe(CN)
6
3
is
