Biomedical Engineering Reference
In-Depth Information
Tombelli et al., 2004, 2007
) and their use for biosensor application as recognition elements
have been suggested, very few, if any, practical applications have appeared in the literature.
Centi et al. (2008)
selected the aptamer (15-mer, GGTTGGTGTGGTTGG-3
0
) for the binding
of thrombin. They also report that the binding interaction between thrombin and the aptamer
has been considered a model system ever since the thrombin-binding aptamer G quartet was
established (
Macaya et al., 1993; Smirnov and Shafer, 2000
) and the binding site was
identified (
Paborsky et al., 1993
). This aptamer has been coupled to different transduction
platforms to demonstrate its wide applicability for biosensor applications as a bioreceptor
(
Baldrich et al., 2004; Bang et al., 2005; Gronewold et al. 2005; Hianik et al., 2005;
Ikebukoro et al., 2005; Radi et al., 2005; Cai et al., 2006; Mir et al., 2006; Radi et al.,
2006; Yoshida et al., 2006; Zhang et al., 2006; Le Floch et al., 2008
).
Centi et al. (2008)
examined different formats for aptamer-based electrochemical assay, and
demonstrated the different optimal assay conditions that may be used with different assay
formats for the binding of thrombin to the aptamer coupled to magnetic beads. They empha-
size that their technique may also be automated to decrease the assay time (
Rashkovetsky
et al., 1997
).
Figure 6.3a
shows the binding of 40 ppm antithrombin in solution to the biotinylated throm-
bin (aptamer) immobilized on a CMB chip surface (
Centi et al., 2008
). A single-fractal anal-
ysis is adequate to describe the binding and the dissociation kinetics. The values of the
binding rate coefficient,
k
, and the fractal dimension,
D
f
, for a single-fractal analysis are
given in
Table 6.2
.
Figure 6.3b
shows the binding of 20 nM antithrombin in solution to the biotinylated thrombin
aptamer immobilized on the surface of a CMB chip. Once again, a single-fractal analysis is
adequate to describe the binding kinetics. The values of the binding rate coefficient,
k
, and
the fractal dimension,
D
f
, for a single-fractal analysis are given in
Table 6.2
. Note that the
values of the binding rate coefficient,
k
, and the fractal dimension,
D
f
, for the binding of anti-
thrombin in solution to the thrombin aptamer immobilized on the CMB chip surface are
much lower than the corresponding values of binding rate coefficient,
k
, and the fractal
dimension,
D
f
, for the binding of thrombin in solution to the thrombin aptamer immobilized
on the CMB chip surface.
Li et al. (2008)
have recently developed an EIS biosensor for analyzing aptamer-thrombin
interfacial interactions. These authors have used a thrombin-binding aptamer as the recogni-
tion element. The aptamer was immobilized on a GCE platform. They achieved signal
enrichment by using GNPs. These GNPs were electrodeposited on the GCE. The interaction
of the thrombin was observed by a change in the interfacial electron transfer resistance of their
biosensor using a redox couple of [Fe(CN)
6
]
3-/4-
as the probe. The authors noted that the
increase in electron transfer resistance of the biosensor is linear in the thrombin concentration
in the range of 0.12-30 nM.
