Biomedical Engineering Reference
In-Depth Information
Bai et al.
(
2008
) have recently developed a Pt-Pb NAE for enzyme-free glucose detection.
These authors point out that there is an inherent instability of enzymatic sensors for glucose
detection as well as the interfering effects of some other electro-oxidizable species (
Wilson
and Turner, 1992; Shoji and Freund, 2001
; Park et al., 2006). Pt-Pb alloy electrodes exhibited
stable, reproducible, and larger responses compared to Pt electrodes alone (
Sun et al., 2001
).
Furthermore, mesoporous platinum (Park et al., 2005) with high surface roughness (higher
fractal dimension) provided not only a better amperometric response but also an effectively
lower interference effect from other electrostatic species. This indicated to
Bai et al.
(2008)
that both the component as well as the surface structure significantly affects the cata-
lytic oxidation of glucose.
Figure 7.6a
shows the binding and dissociation of 1 mM glucose in 0.1 M PBS in solution to
the pt-Pb NAE (
Bai et al., 2008
). A single-fractal analysis is adequate to describe the binding
kinetics. A dual-fractal analysis is required to adequately describe the dissociation kinetics.
The values of (a) the binding rate coefficient,
k
, and the fractal dimension,
D
f
, for a single-
fractal analysis, (b) the dissociation rate coefficient,
k
d
, and the fractal dimension,
D
fd
, for
a single-fractal analysis, and (c) the dissociation rate coefficients,
k
d1
and
k
d2
, and the fractal
dimensions,
D
fd1
and
D
fd2
, for a dual-fractal analysis are given in
Tables 7.4
and
7.5
.
It is of interest to note that as the fractal dimension for dissociation increases by a factor of
1.88 from a value of
D
fd1
equal to 1.5932 to D
fd2
equal to 3.0 (the maximum value), the dis-
sociation rate coefficient increases by a factor of 6.0 from a value of
k
d1
equal to 0.001 to
k
d2
equal to 0.006. It is seen that an increase in the degree of heterogeneity or the fractal dimen-
sion on the biosensor surface in the dissociation phase leads to an increase in the dissociation
rate coefficient. This is consistent with the statement of
Bai et al. (2008)
that the surface
structure significantly affects the catalytic oxidation of glucose. Besides, this result indicates
that the dissociation rate coefficient is sensitive to the degree of heterogeneity on the biosen-
sor surface. The affinity,
K
1
(
¼
k
/
k
d1
) and
K
2
(
¼
k
/
k
d2
), values are equal to 5.2 and 0.867,
respectively.
Figure 7.6b
shows the binding and dissociation of 1 mM glucose in 0.1 M PBS to the
Pt-PbNAE (
Bai et al., 2008
). A single-fractal analysis is adequate to describe the binding
and the dissociation kinetics. The values of (a) the binding rate coefficient,
k
, and the fractal
dimension,
D
f
, for a single-fractal analysis, and (b) the dissociation rate coefficient,
k
d
,
and the fractal dimension for dissociation,
D
fd
, for a single-fractal analysis are given in
Tables 7.4
and
7.5
. In this the affinity,
K
(
¼
k
/
k
d
), value is equal to 29.3.
Figure 7.6c
shows the binding and dissociation of 1 mM glucose in 0.1 M PBS to the
Pt-PbNAE (
Bai et al., 2008
). A single-fractal analysis is once again adequate to describe
the binding and the dissociation kinetics. The values of (a) the binding rate coefficient,
k
,
and the fractal dimension,
D
f
, for a single-fractal analysis, and (b) the dissociation rate
