Biomedical Engineering Reference
In-Depth Information
cult using micromachined technology, and it gives us a sensitive and selective
DNA chip sensor.
The Detection of DNA Amplification Using an Electrochemical Me-
thod.
In this subsection, the principles and advantages of DNA biosensing
using electrochemical methods are illustrated by examples. Figure 4.14 shows
the principle of electrochemical detection. Hoechst 33258 is a DNA minor
groove binder and an electrochemically active dye [10]. Before PCR, Hoechst
33258 hardly binds to DNA, because the concentrations of target DNA are
low. On the other hand, After PCR the DNA concentration is high, and
therefore this dye will almost bind to DNA.
Figure 4.15 shows linear sweep voltammograms of Hoechst 33258 on DNA.
By using an electrochemical method after PCR, DNA amplification was de-
tected. The target DNA is HBV, its length is 1 kbp, and the amplified area
was a selected high preserve sequence. The electrochemical measurements
were carried out using an electrochemical analyzer (BAS-50W). The electro-
chemical signals of 50
μ
M Hoechst 33258 were measured. The anodic current
of Hoechst 33258 after PCR is smaller than that before PCR. The reason for
this may be that a lot of Hoechst 33258 is bound to amplified DNA and so
the electrochemical response is decreased compared to that before PCR. In
fact, this result means that electrochemical response of intercalated Hoechst
Before
PCR
After PCR
= Hoechst 33258
( no intercalation)
= intercalated Hoechst
>
Electrochemical
detection
electrode
Fig. 4.14.
The method of electrochemical gene detection
-1.5
before PCR with
Hoechst 33258
-2.0
-1.0
-0.5
after PCR with
Hoechst 33258
0
300 350 400 450 500 550 600
E (mV)
Fig. 4.15.
Linear sweep voltammograms of Hoechst 33258 on HBV
