Biomedical Engineering Reference
In-Depth Information
40
35
30
25
20
HIV SK38
HIV SK39
HCV 1a
C
20
T
20
-SH
(complementary)
Probe DNA
Fig. 4.10.
Anodic peak current values of Hoechst 33258 on different probe-modified
electrodes. 100 nM probe DNA (HIV SK 38, HIV SK 39, HCV 1a, and C
20
T
20
-
SH) was immobilized on the gold electrodes by spotting with DNA arrayer. 10 nM
target DNA (HIV SK 39 target) was hybridized and reacted with Hoechst 33258
on the chip
of electrode. When we used the HIV SK 39 probe as the target DNA, the
electrode modified with complementary DNA against HIV SK 39 probe gave
the biggest anodic current (Fig. 4.10).
Calibration curves for target DNA were shown in Fig. 4.11. The anodic
current increased with the concentration of the target DNA from 0.01 to
100 nM. The control DNA also gave anodic current because Hoechst dye was
not completely specific to duplex DNA. If we have target DNA over 1 nM, we
can discriminate target DNA. When nontarget DNA was less than 0.01 nM,
the sensitivity improved up to 0.1 nM, because the background level was re-
duced. Each electrode may react with a sample solution of approximately 1 nl
volume.Onthisassumption,approximately10
5
molecules of target DNA can
be determined by each electrode. Figure 4.12 shows the results of detection of
a single base pair mismatch. When target or one base mismatched DNA was
used at 100 nM, they were detected using differential pulse voltammometry.
However, it was dicult to detect SNPs less than 10 nM. A PCR-amplified
sample is also acceptable in this case.
4.2.3
The Microfluidic PCR Chamber
and the Electrochemical Detector
The determination of a specific DNA sequence presented in biological sam-
ples such as blood, serum, tissues, and body fluid is of great significance in
the biomedical field. The results from such analyses can be used to detect
infelicitous diseases of bacterial and viral origin. Therefore, there has been
