Biomedical Engineering Reference
In-Depth Information
Fig. 5.11 a
Schematic analysis of a target DNA by a sandwich-type nucleic acid assay on the
CdS QDs-BSA conjugate associated with an electrode using the hemin/G-quadruplex as a cat-
alytic label for the CRET-stimulated generation of photocurrents.
b
Time-dependent photocur-
rent intensities upon analyzing different concentrations of the analyte DNA, 4, using the CdS
QDs/BSA-3 as the sensing interface and the hemin/G-quadrplex as a catalytic label for the gen-
eration of chemiluminescence and CRET-stimulated generation of photocurrents. Concentrations
of 4 correspond to (
a
) 0 nM, (
b
) 1 nM, (
c
) 5 nM, (
d
) 10 nM, (
e
) 100 nM, and (
f
) 1,000 nM.
c
Derived calibration curve corresponding to the photocurrent intensities generated by different
concentration of 4 after a time interval of 1 min. Error bars were derived from a set of
N
=
3
experiments. Inset: the linear part of the calibration curve.
d
Photocurrent intensities upon ana-
lyzing (
a
) the target, 4, 1
μ
M; (
b
) the single-base mismatched nucleic acid 4a, 1
μ
M; and (
c
) the
two-base mismatched nucleic acid 4b, 1
μ
M, using CdS QD-BSA-3 sensing interface and 5 as
a catalytic label. In all experiments, a 10 mM HEPES buffer solution, pH
=
9.0, that included
20 mM KNO
3
, 200 mM NaNO
3
, 1
μ
M hemin, 0.1
μ
M 5, 0.57 mM luminol, 0.5 mM H
2
O
2
, and
20 mM triethanolamine (TEOA) was used as the analysis reaction medium. Reproduced with
permission from Ref. [
59
]. Copyright 2012, American Chemical Society
Since the surface coverage of the hemin/G-quadruplex on the electrode is con-
trolled by the concentration of the analyte, the resulting photocurrent intensities
depend on the concentration of the analyte and provide a quantitative measure
for the DNA analyte, 4. Figure
5.11
b shows the photocurrent intensities gener-
ated by the system in the presence of different concentrations of the analyte DNA.
Figure
5.11
c shows the resulting calibration curve, implying that the analyte DNA
could be detected with a detection limit that corresponds to 2 nM.
