Biology Reference
In-Depth Information
by Gorodetsky
et al.
who utilized duplex DNA functionalized with
pyrene to fabricate DNA-modified electrodes on highly oriented
pyrolytic graphite (HOPG) [41]. As expected, the reduction of the
intercalator was attenuated in the presence of the single-base
mismatches, CA and GT, independent of the sequence composition
of the oligonucleotide. Furthermore, the extended potential range
affordedbytheHOPGsurfacehasallowedtheauthorstoinvestigate
theelectrochemistryofpreviouslyinaccessiblemetallointercalators,
[Ru(bpy)
2
dppz]
2
+
and [Os(phen)
2
dppz]
2
+
, at the DNA-modified
HOPG surface. These results support the application of DNA-
modified HOPG as a convenient and reproducible surface for elec-
trochemicalDNAsensorsusingDNA-mediatedchargetransport.MB
was also used in practical sensor design utilizing a CeO
2
/chitosan
composite matrix to increase the loading of the ss-DNA probe and
to enhance the biosensor's response performance [47]. The use
of an interesting ruthenium complex as a sensitive and selective
electrochemical indicator in DNA sensing was reported by Garcia
et al.
[48] The ruthenium complex, Ru(NH
3
)
5
-[3-(2-phenanthren-9-
yl-vinyl)-pyridine] generated
in situ
incorporates dual functionali-
ties. The Ru center provides a redox probe and the ligand provides
a fluorescent tag. The presence of the aromatic groups in the
ligand endows the complex with an intercalative character and
makes it able to bind to ds-DNA more e
ciently than to ss-DNA.
Combinationofspectroscopicandelectrochemicalstudiesindicated
fundamentally intercalative interactions between the complex and
ds-DNA. The ligand-based fluorescence allows the characterization
of the complex formation and monitoring of duplex melting.
The metal-based redox center is employed as an electrochemical
indicator to detect the hybridization event in a DNA biosensor.
The sensing surface was prepared by incubation a Au electrode
with a thiolated ss-DNA based on a short DNA sequence from
Helicobacter pylori
. With the use of this approach, complementary
target sequences of
H.pylori
can be quantified with a detection limit
of 92 pmol. In addition, this approach allows the detection of not
only a single mismatch but also its position in a specific sequence
of
H. pylori
, due to the selective interaction of this bifunctional
ruthenium complex with ds-DNA. A new electroactive intercalator,
Cd(II)-morin,(Scheme 7.2) wasreported by Niu
et al.
[49].
