Biology Reference
In-Depth Information
a thiol group. Large specific surface Au-NPs-modified electrodes
can enhance the amount of DNA immobilized onto the electrode
leading to an improvement of the biosensor performance. Many of
the examples reported in the literature imply a previous chemical
preparation of Au-NPs, with a subsequent modification of the
electrode surface through physical adsorption or chemical linking.
Nanomaterial-based platforms suitable to construct biosensors
are fabricated in this way. Alternatively, direct electrochemical
deposition of Au-NPs onto the electrode surface constitutes a rapid,
clean,andversatilemodetocreatenanomaterialplatforms
in situ
for
the construction of DNA biosensors. The next sections revise some
illustrative examples of several designs employed to prepare such
platforms.
4.2.1
Au-Thiol Binding
Gold electrode substrates have attracted special attention for
the preparation of electrochemical DNA biosensors since DNA
can be strongly bound at the surface of gold through Au-thiol
binding. Thiolated DNA can be monolayered on gold in a self-
assembly manner, which provides stable and structurally well-
defined electrochemical interfaces. However, one major drawback
of the gold electrode is attributed to the cleaning step; in order
to obtain reproducible results, the gold electrode needs to be
mechanically polished and then electrochemically etched in acid
solutions. This time-consuming process determines a quality of
electrochemical DNA biosensors.
Various recent interesting configurations of genosensors take
advantage of the Au-thiol binding strategy with gold nanoparticles,
for example, gold nanoparticles were electrodeposited on screen-
printed electrodes which were subsequently modified with a self-
assembledmonolayerofthiol-cappedsingle-strandedDNA(capture
probe) (Fig. 4.3). This immobilization strategy was employed to
construct a genosensor for the detection of the rfbE gene, which is
specific to
E. coli
O157 [12].
A similar immobilization methodology has been used to develop
a DNA-sensing platform for
Helicobacter pylori
[13]. Rigid conduct-
inggoldnanocompositeshavebeenalsomodifiedwiththisstrategy.
