Biology Reference
In-Depth Information
Figure4.3.
SchemedisplayingtheDNAimmobilizationstrategyinvolving
thiol binding [12] (adapted with permission of the American Chemical
Society).
For example, using Au-NPs-graphite epoxy composites, islands of
chemisorbing material ( Au-NPs) surrounded by nonreactive, rigid,
andconductinggraphiteepoxycompositesareachievedtoavoidthe
stringent control of surface coverage parameters required during
immobilization of thiolated oligonucleotides in continuous gold
surfaces [14]. The spatial resolution of the immobilized thiolated
DNA can be easily controlled by merely varying the percentage of
gold nanoparticles in the composite.
Impedimetric genosensors were also constructed by making
use of gold nanoparticles electrodeposited on the surface of a
gold electrode, and subsequent immobilization of probe DNA
on the surface of gold nanoparticles through a 5'-thiol-linker
[15]. Electrochemical impedance spectroscopy (EIS) was used to
investigateprobeDNAimmobilizationandhybridization.Compared
to the bare gold electrode, the gold nanoparticle-modified electrode
improved greatly the density of probe DNA attachment and the
sensitivityofDNA sensor.
Shen
et al.
[16] have recently reported the development of an
electrochemicalDNAzymebiosensorbasedonDNA-Aubio-barcode
amplification, which provides a platform for fabrication of sensors
for analysis of many small molecules, especially for metal ions. For
example, a specific DNAzyme for Pb
2
+
was immobilized onto an
Au electrode surface via a thiol-Au interaction, taking advantage of
catalytic reactions of a DNAzyme upon its binding to Pb
2
+
and the
use of DNA-Au bio-bar codes to achieve signal enhancement [16].
The presence of gold nanoparticles, enhancing the active surface
