Biomedical Engineering Reference
In-Depth Information
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 is given in
Table 15.1
.
Centi et al. (2008)
have recently developed an electrochemical aptamer-based assay coupled
to magnetic beads for the detection of thrombin. These authors indicate that aptamers are
nucleic acid ligands that can be generated against amino acids, drugs, proteins, and other
molecules.
SELEX (Systematic Evolution of Ligands by Exponential Enrichment) is used to isolate
aptamers from a random library of synthetic nucleic acids by an iterative process of binding,
separation, and amplification. Aptamers have been established recently as biorecognition
elements (
Ellington and Szoztak, 1990; Tuerk and Gold, 1990; Tombelli et al., 2007
).
Centi et al. (2007)
have reported the application of an aptamer-based electrochemical sand-
wich assay coupled with magnetic beads. They affirm that their assay demonstrated good
reproducibility. They also point out that the aptamer-based assay may be used in the follow-
ing formats: sandwich or competitive assay, and direct or indirect assay. The choice of the
format is primarily dependent on the analyte's molecular size and cost.
Figure 15.3a
shows the binding of 400 ppm IgG antithrombin in solution to immobilized
biotinylated thrombin (
Centi et al., 2008
). 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 15.1
.
Figure 15.3b
shows the binding of 200 nM-thrombin in solution to immobilized biotinylated
aptamer (
Centi et al., 2008
). A single-fractal analysis is, once again, adequate to describe the
1600
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200
0
800
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400
200
0
0
200
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600
Time (s)
800
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0
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Time (min)
600
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1000
A
B
Figure 15.3
(a) Binding of 400 ppm IgG antithrombin in solution to immobilized biotinylated thrombin
(
Centi et al., 2008
). (b) Binding of 200 nM thrombin in solution to immobilized biotinylated
aptamer (
Centi et al., 2008
).
