Biology Reference
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Figure 2.9. General scheme of an aptasensor based on target-induced
strand displacement.
complementary single-stranded DNA was fixed onto a gold elec-
trode. [Fe(CN) 6 ] 3 / 4 was then used as a redox couple to monitor
the change in electron transfer at the electrode upon binding of the
targetmolecule,lysozyme.Inthepresenceoflysozyme,theaptamer
was displaced from the duplex and the electron-transfer resistance
was decreased. This decrease could be monitored by FIS in a con-
centrationrangebetween0.2and4nMandwithadetectionlimitof
0.07 nM.
Inanotherwork[49],thethrombinaptamerwashybridizedwith
a ferrocene-labeled DNA oligonucleotide and immobilized onto a
gold electrode. The binding of thrombin to the aptamer causes the
displacement of the complementary oligonucleotide resulting in a
decrease of current recorded at the electrode by differential pulse
voltammetry (DPV). A linear range for the detection of thrombin
between 0 and10 nMwasobtained.
Another aptasensor based on the displacement of a complemen-
tarystrandfromanaptamerwasdevelopedforthedetectionofATP
by coupling this approach to signal amplification by Au-NPs [50]. In
this work the hybrid was formed by a reporter DNA labeled with
Au-NPs,athiol-modifiedDNAanchoredtoanelectrodeandatarget-
responsive DNA (the aptamer) (Fig. 2.10). Moreover, [Ru(NH 3 ) 6 ] 3 +
 
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