Biomedical Engineering Reference
In-Depth Information
Figure 13.7c
and
Table 13.5
show the increase in the binding rate coefficient
k
with an
increase in the fractal dimension
D
f
. For the data shown in
Figure 13.7c
, the binding rate
coefficient
k
is given by:
D
4
:
753
0
:
5339
k
¼ð
0
:
4638
0
:
1646
Þ
ð
13
:
5c
Þ
f
The fit is good. Only four data points are available. The availability of more data points
would lead to a more reliable fit. The binding rate coefficient
k
is very sensitive to the fractal
dimension
D
f
or the degree of heterogeneity that exists on the sensing surface as noted by the
higher than four and a half (equal to 4.753) order exhibited.
Tang et al (2006)
have developed and analyzed a nonregeneration protocol for surface
plasmon resonance biosensors. They studied the high-affinity interaction with high-density
biosensors. They report the “optimum” amount of regeneration involved in SPR biosensor
applications, which has been around as a real-time, nonlabel technique for the analysis of
biological interaction since the early 1990s (
Karlsson et al., 1991; Jonsson and Malmquist,
1992
). The essence of regeneration is to remove the bound analytes and still maintain the bio-
activity of the ligand (receptor). Also, as
Tang et al. (2006)
report, the surface density of the
ligand should be the same for each analyte injection to permit data analysis. The discovery or
development of an acceptable regeneration protocol is not easy (
Tang et al., 2006
). To cir-
cumvent this, these authors have developed a nonregeneration protocol between successive
analyte injections. This is especially useful for high-affinity antigen-antibody interactions.
In essence, the nonregeneration protocol needs a relatively high ligand density on the biosen-
sor surface so that more data points can be obtained before surface saturation. As a model
system
Tang et al. (2006)
used rabbit IgG as the analyte and engineered recombinant anti-
body A10B ScFv as the ligand.
Figure 13.8a
shows the binding and dissociation of 1.3
m
M rabbit IgG in solution to
engineered recombinant A10B ScFv immobilized on a high-density biosensor. A dual-fractal
analysis is required to adequately describe the binding kinetics. A single-fractal analysis is
adequate to 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 binding rate coefficients
k
1
and
k
2
and the fractal dimensions
D
f1
and
D
f2
for a dual-fractal analysis, and (c) the dis-
sociation rate coefficient
k
d
and the fractal dimension for dissociation
D
fd
for a single-fractal
analysis are given in
Tables 13.6
and
13.7
.
Figure 13.8b
shows the binding and dissociation of 0.53
m
M rabbit IgG in solution to
engineered recombinant A10B ScFv immobilized on a high-density biosensor. Once again,
a dual-fractal analysis is required to adequately describe the binding kinetics. A single-fractal
analysis is adequate to 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 binding rate
