Biomedical Engineering Reference
In-Depth Information
more easily dissociated from dsDNA-modified gold electrode in the presence of
CdTe QDs. In relatively low ionic strength, the dissociation coefficient constant
of Co(phen)
3
3
+
/2
+
in the presence of CdTe QDs was 3.1 times higher than that
in the absence of CdTe QDs. This value reduced to 1.32 times in relatively high
ionic strength. This indicated that the binding site of CdTe QDs on dsDNA was
probably at major groove of dsDNA. This demonstration offers a new approach to
illustrate the QDs cytotoxicity mechanism. Based on this research, Jiao et al. [
23
]
developed an electrochemical biosensing for dsDNA damage induced by PbSe
QDs under UV irradiation. In this research, the damage of dsDNA was fulfilled
by immersing the sensing membrane electrode in PbSe QDs suspension and illu-
minating it with an UV lamp. Cyclic voltammetry was utilized to detect dsDNA
damage with Co(phen)
3
3
+
as the electroactive probe. The synergistic effect among
the UV irradiation, Pb
2
+
ions liberated from the PbSe QDs under the UV irradia-
tion, and the reactive oxygen species (ROS) generated in the presence of the PbSe
QDs dramatically enhanced the damage of dsDNA. This electrochemical sensor
provided a simple method for detecting DNA damage and may be used for investi-
gating the DNA damage induced by other QDs.
Using CdSe/ZnS as label, a relatively simple, time-saving, and multiapproach
biosensor for the DNA detection was fabricated in our group [
24
]. By detect-
ing the cadmium content in the bond QDs, the target DNA could be indirectly
detected through the SWASV assay. Based on the hairpin probe and site-specific
DNA cleavage of restriction endonuclease, Chen et al. [
25
] fabricated an electro-
chemical DNA biosensor. This biosensor was used to detect DNA species related
to cymbidium mosaic virus. The stripping voltammetric measurements of the dis-
solved Cd
2
+
were successfully performed to indirectly determine the sequence-
selective discrimination between perfectly matched and mismatched target DNAs
including a single-base mismatched target DNA, and the limit detection could
reach as low as 3.3
×
10
−
14
M for complementary target DNA. Given the simplic-
ity in design of the proposed electrochemical sensor, it is fairly easy to generalize
this strategy to detect a spectrum of targets and might have a promising future for
the investigation of DNA hybridization, also would play the potential predomi-
nance in diagnosis of virus or diseases.
What is more, based on the fact that different metal components of different
QD nanocrystal tracers yield different well-resolved and highly sensitive strip-
ping voltammetric signals, the multitarget electrochemical biosensor could be
fabricated via the utilization of different QD codes. This new multielectrochemi-
cal coding technology opens new opportunities for DNA diagnostics and for
bioanalysis.
In 2003, Wang et al. [
26
] first employed this strategy for the simultaneous
detection of multiple DNA targets based on QD tags with diverse redox potentials
(Fig.
5.3
). Such encoding QDs offered a voltammetric signature with distinct elec-
trical hybridization signals for the corresponding DNA targets. Via the utilization
of different inorganic colloid QD nanocrystal tracers, whose metal components
yield well-resolved highly sensitive stripping voltammetric signals for the corre-
sponding targets, three encoding QDs (ZnS, CdS, and PbS) have thus been used
