Biomedical Engineering Reference
In-Depth Information
coefficient,
k
, and the fractal dimension for a single-fractal analysis, and (b) the dissociation
rate coefficient,
k
d
, and the fractal dimension
D
fd
, for a single-fractal analysis are given in
Table 12.2
.
Boecker et al. (2007)
recently pointed out that the SPR (surface plasmon resonance) detection
of analytes in solution has been an important means for the detection of biomolecules ever
since the first application when this instrument was used (
Leidberg et al., 1995
). However,
Boecker et al. (2007)
report that for high throughput and for the detection of biomolecules
at low detection limits, the SPR instrument poses challenges. These authors describe a differ-
ential imaging that reduces factors which interogate the detection of single-wavelength imag-
ing methods. These authors used an additional second laser with a different wavelength for
differential image processing. This allowed them to obtain low detection limits in relatively
small spots. They used a CCD camera for the simultaneous processing of two images at the
different wavelengths provided by the two laser diodes.
Boecker et al. (2007)
explain that the SPR imaging technique is based on intensity
measurements at a fixed reflection angle. The surface is illuminated by a collimated mono-
chromatic beam which is slightly shifted from the SPR resonance angle. Any shift of the res-
onance causes a change in the reflected intensity. These intensity variations due to molecular
binding may be observed simultaneously by means of a CCD matrix (
Shumaker-Parry and
Campbell, 2004
).
Boecker et al. (2007)
point out that the technique is affected by possible
changes of the resonance curve owing to modification of the surface roughness or to light
absorption.
Zybin et al. (2005)
recently applied two widened, collimated laser beams of dif-
ferent wavelengths combined in one beam irradiating the metal surface of the SPR device.
Boecker et al. (2007)
analyzed the hybridization (binding) of different DNA to their comple-
mentary DNA by their differential surface plasmon resonance imaging technique.
Figure 12.6a
shows the binding of 1
m
M DNA RS1 in solution to RS1-c immobilized on
the sensing surface. A dual-fractal analysis is required to adequately describe the hybrid-
ization (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 12.3
.
It is of interest to note that as the fractal dimension increases by a factor of 2.438 from a
value of
D
f1
equal to 1.0566 to
D
f2
equal to 2.5766, the binding rate coefficient increases
by a factor of 1.62 from a value of
k
1
equal to 1.073 to
k
2
equal to 1.742. Changes in the
degree of heterogeneity on the sensing surface or the fractal dimension and in the binding
rate coefficient are in the same direction.
Figure 12.6b
shows the binding of 1
m
M DNA RS2 in solution to RS2-c immobilized on the
sensing surface. A dual-fractal analysis is required to adequately describe the hybridization
(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 12.3
.
