Biomedical Engineering Reference
In-Depth Information
Fig. 5.10 a
Schematic mechanism of the operating PEC system.
b
Photocurrent intensity in
0.10 M PBS containing 0.10 M ascorbic acid of (
a
) PDDA/CdS-modified ITO electrode, (
b
)
modified with 20
μ
L, 1
μ
M capture DNA and blocked by MEA, and (
c
) hybridized with Ag
NPs-labeled target DNA. The oligonucleotide sequences of 12 base pairs were used here, and
their concentration was 1.0
×
10
−
6
M. The working potential was 0.0 V, and the excitation wave-
length was 420 nm.
c
Effect of different concentrations of target DNA on the differential photo-
current responses (
Δ
I
=
I
0
−
I
,
I
0 and
I
are the photocurrents of capture DNA/CdS/ITO electrode
before and after hybridization).
Insert
the corresponding calibration curve. The used DNA was
36 bases, and the photocurrent measurement was carried out in 0.10 M PBS containing 0.10 M
ascorbic acid (AA). The working potential was 0.0 V, and the light wavelength was 420 nm.
Reproduced with permission from Ref. [
58
]. Copyright 2012, American Chemical Society
solution also contained the catalytic DNA label, 5, composed of the G-quadruplex
sequence and a nucleic acid residue that can hybridize with the free 3′-end of
the analyte, 4. Thus, the analyte serves as a bridging unit for the assembly of the
hemin/G-quadruplex label on the electrode. Accordingly, in the presence of the
analyte, the hemin/G-quadruplex catalytic label is positioned in close proximity to
the CdS QDs associated with the electrode. As a result, the hemin/G-quadruplex-
catalyzed oxidation of luminol by H
2
O
2
and the resulting chemiluminescence
may stimulate the CRET process and lead to the generation of the photocurrent.
