Biology Reference
In-Depth Information
5.2 Catalysis Induced by Gold Nanoparticles
Gold nanoparticles (Au-NPs) and silver nanoparticles (Ag-NPs) are
of particular interest in DNA sensors and immunosensors due
to their advantageous properties, such as hydrophilicity, standard
fabrication methods, excellent biocompatibility, unique character-
istics in the conjugation with biological recognition elements, and
multiplex capacity for signal transducer. Therefore, a large number
ofpublishedmethodsuseAu-orAg-NPsinDNA[16, 17, 18]protein
[19] and even cell [20] electrochemical detection besides optical
detections like ICP-MS[21] or their use asELISA enhancer [22].
Metallic gold was thought to be very stable and useless for some
catalyticsystems,butbythereductionofsizetothenanoscalerange,
gold has been proved to be a very reactive element and it has been
extensively used in sensing and biosensing systems as a catalyst
for some interesting electroanalytical applications. For instance, a
sensitive NO sensor was developed through the modification of
a platinum microelectrode by Au-NPs in which they catalyze the
electrochemical oxidation of NO with an overpotential decrease of
about 250 mV [15]. An SO
2
gas sensor was also developed using
Au-NPs to catalyze the electrochemical oxidation of SO
2
when the
gas diffusesthrough the pores of the working electrode [23].
Based on the selective catalysis of Au-NPs, selective electro-
chemical analysis could also be achieved as, for example, in the
dopamine electrochemical detection in presence of ascorbic acid.
In this case, Au-NPs can be used as selective catalysts since their
presence induces the decreasing of ascorbic acid overpotential and
the effective separation of the oxidation potentials of ascorbic acid
and dopamine [13].
5.2.1
Electrocatalytic Activity of Gold Nanoparticle Labels
on Silver Deposition
Wang
et al.
[24]firstreportedaDNAhybridizationdetectionmethod
based on the precipitation of silver on Au-NP tags and subsequent
electrochemical stripping detection of the dissolved silver. The
assay employed a sandwich-like protocol with streptavidin-Au-NPs
labeling the biotinylated-breast cancer gene (BRCA1) sequences.
