Biology Reference
In-Depth Information
Figure 2.4.
SchemeoftheanalyticalprocedurebasedontheuseofPt-NPs
for the analysis of thrombin.
The high sensitivity of such measurements is based on the pre-
concentration step, during which the metals are electrodeposited
onto the working electrode [26]. It is important for the minimiza-
tion of the non-specific adsorption and for the corresponding back-
ground signal. For this reason, surface blocking steps should be
employedtoavoidtheamplificationofthebackgroundsignal.More-
over,thecontrolofthecoverageallowstoensureagoodaccessibility
and stabilityofthe surface boundprobe.
The first electrochemical aptasensor using NPs was reported by
Polsky [27] for the detection of thrombin. A sandwich configura-
tionwasdesignedandforthispurposethiolatedaptamermolecules
wereimmobilizedongold-coveredslide,thentheaptamer-modified
surface was incubated first with thrombin and at the end with
aptamer-modified Pt-NPs (aptamer-Pt-NPs) (Fig. 2.4). The Pt-NP
labels associated with the thrombin were then used as sites for the
electrocatalytic reduction of H
2
O
2
that was added to the working
medium before analysis and linear sweep voltammetry was used as
electrochemicaltechnique.Thereductionofhydrogenperoxidegave
risetoacathodiccurrentwhichdirectlyrelatedtotheconcentration
of thrombin. The detection limit found using this method was 1 nM
of thrombin.
Another example of electrochemical aptasensor based on Au-
NPs as labels for the detection of thrombin is reported by Zheng
et al.
[28]. The assay was based on a sandwich format, in which the
aptamerI (15-mer DNA aptamer with an amino group at its 5' end)
wasimmobilizedontocarboxylfunctionalizedmagneticbeads.Such
aptamer-coated magnetic beads were used for capturing and sepa-
ration. Thrombin and Au-NP-labeled aptamerII were then added to
