Biology Reference
In-Depth Information
to minimize the electrocatalytic oxidation of NaBH
4
by Au-NPs they
used magnetic beads as capture probe immobilization platforms
that acted also as spacers between Au-NPs and the ferrocene-
modified ITO electrode, achieving this effect only when the density
of Au-NPs at magnetic beads surface is low. The Au-NPs used as
labels, were modified with a monolayer of DNA detection probe,
without a significant loss in catalytic activity of Au-NPs for signal
amplification. By the conjugation of all the mentioned techniques
they achieved good signal amplification with low background
current and a detection limit of 1fM for DNA target with good target
discrimination.
Recently, Yang's group [7] reported a novel strategy for Au-NP-
based signal enhancement by the improvement of electrocatalytic
activityoflabels.TheDNAlayerontheAu-NPsdoesnotsignificantly
limit the mass transfer of small molecules and ions such as
p-hydroquinone and Ag
+
, or inhibits the catalytic reduction of
p-nitrophenol. However, the distance between the electrocatalytic
Au-NP label and the ITO electrode is too long and the enhancement
byelectrochemicaltreatmentrequiresextremelyappliedpotentials.
To overcome this problem, this same group applied a simple chem-
ical treatment of Au-NPs by using NaBH
4
instead of electrochemical
treatment(Fig.5.4).TheresultsshowedthatNaBH
4
treatmentcould
significantly enhance electrocatalytic activity of DNA-conjugated
Au-NPstowardthehydrazinecurrentontheITOelectrodes,without
damagingthebiosensinglayers.Thisresult,incombinationwiththe
electrode modification with Au-NPs, allowed a high signal current
Figure 5.4.
Schematic view of electrochemical DNA detection using
the enhanced electrocatalytic activity of Au-NP labels toward hydrazine
(NH
2
NH
2
) reduction on ITO electrodes (adapted from Ref. 7 with
permission). See also ColorInsert.
