Biomedical Engineering Reference
In-Depth Information
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
.
Shin and Liu (2007)
have recently developed a screen-printed cholesterol biosensor. These
authors compared the performance of gold (Au) and platinum (Pt) as the working electrode
material. A self-assembly approach was used to fabricate the biosensor. These authors indi-
cate that both the gold and the platinum would detect the cholesterol in solution through
the electrochemical oxidation of H
2
O
2
. However, the authors selected gold as the working
electrode material as it exhibited a higher response current and better sensitivity. The enzyme
cholesterol oxidase (Chox, E.C. 1.1.3.6) was immobilized on the Au working electrode by
using a self-assembly approach. The authors report that their thick-film screen-printed cho-
lesterol biosensor comprises three electrodes on an alumina-substrate. 3-mercaptopropionic
acid (MPA) was self-assembled onto the gold working electrode and formed a thin organic
layer. This thin layer of MPA served as an anchor for enzyme immobilization.
Figure 15.4a
shows the binding of 20 mg/dl cholesterol in solution to the cholesterol biosen-
sor. 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
are given in
Table 15.2
.
Figure 15.4b
shows the binding of 100 mg/dl cholesterol in solution to the cholesterol biosen-
sor. A dual-fractal analysis is required to adequately describe the binding kinetics. The values
of (a) the binding rate coefficient k and the fractal dimension
D
f
for a single-fractal analysis,
and (b) the binding rate coefficients
k
1
and
k
2
and the fractal dimensions
D
f1
and
D
f2
for a
dual-fractal analysis are given in
Table 15.2
.
0.35
0.25
0.3
0.2
0.25
0.15
0.2
0.15
0.1
0.1
0.05
0.05
0
0
0
10
20
Time (min)
30
40
0
10
20
Time (min)
30
40
B
A
Figure 15.4
Binding of different concentrations of cholesterol (in mg/dl) to a cholesterol biosensor
(
Shin and Liu, 2007
): (a) 20
Continued