Biology Reference
In-Depth Information
Figure 5.2.
Schematic diagram of the silver chemical deposition on Au-
NP labels applied for the electrochemical detection of DNA hybridization.
Voltammograms correspond to DPV responses of the Au-NP-labeled
oligonucleotide probes in presence of (A) complementary, (B) single-base
mismatch, and (C) non-complementary oligonucleotides (adapted from
Ref. 25 with permission). See also ColorInsert.
After the silver precipitation on the gold, the silver was dissolved
and detected at a disposable thick film carbon electrode using
potentiometric stripping. This method coupled the inherent signal
amplification of nanoparticle-promoted silver precipitation and the
stripping metal analysis with effective discrimination against non-
hybridized DNA. Cai
et al.
[25] reported a similar assay based on
the silver deposition onto Au-NP-labeled oligonucleotides and sub-
sequent electrochemical detection of Ag ions anchored onto Au-NPs
connected to hybrids through differential pulse voltammetry using
a glassy carbon electrode (Fig. 5.2). With this assay they obtained a
detection limitof 50 pM of complementary oligonucleotides.
Later on, Lee
et al.
[26] reported the electrocatalytic effect of
Au-NPs on silver electrodeposition upon ITO-based electrodes
(Fig. 5.3), in absence of pre-oxidation steps, and its successful
application to the DNA hybridization detection obtaining a signal-
to-noise ratio of 20 that presented a great improvement in relation
to their previous works under similarconditions.
5.2.2
Electrocatalytic Activity of Gold Nanoparticle Labels
on Other Reactions
The specific binding of highly electrocatalytic labels to a biosensing
layer immobilized on poor electrocatalytic electrode enhances the
electrocatalytic current signal. If these labels are arranged in a
low coverage level, the induced change in background current will
be small which results in a large change in signal along with
