Biomedical Engineering Reference
In-Depth Information
state that their biosensor is sensitive enough to quantify these PSP toxins in the European regu-
latory range limit of 80
m
g/100 g of shellfish meat.
Fonfria et al. (2007)
report that more than 24 compounds have been identified as PSP toxins
(
Schantz et al., 1975; Shimuzu et al., 1981; Yasumoto and Murata, 1993; Oshima et al., 1995;
Negri et al., 2003
).
Fonfria et al. (2007)
point out that all of these compounds differ in the
combinations of hydroxyl and sulfate substitutions located at four sites of a 3,4,6-trialkyl tet-
rahydropurine backbone. The mechanism of action of all of these compounds is the same: the
inhibition of the voltage-gated sodium channels in excitable cells (Kao, 1966;
Catterall,
1980
). Gessner and Middaugh (1995) and Rodriguez et al. (1990) report that neurological
symptoms in humans are induced by the blockage of neuronal transmission. These symptoms
include perioral paresthesia, dizziness, paralysis, and even respiratory illness and death. Par-
esthesia is an abnormal sensation of the skin. This may include numbness, tingling, burning,
or creeping on the skin with no specific cause. Basically, it is an abnormal feeling.
Fonfria et al. (2007)
have used a GT13-A-STX chip to detect PSP toxins in an inhibition
assay using a SPR biosensor. These authors detected STX in solution by competition for
binding to the GT13A-antibody also in solution with the STX immobilized to the chip sur-
face. The
y
report that the presence of STX in solution previously mixed with the GT13-A
antibody inhibited the binding of the antibody to the STX chip surface.
Figure 14.10a
shows the binding of the antibody control (0 ng/mL) to the STX sensor chip in
a Biacore Q biosensor. 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
Tables 14.6
and
14.7
.Itis
of interest to note that, once again, as the fractal dimension increases by a factor of 3.13 from
a value of
D
f1
equal to 0.9576 to
D
f2
equal to 3.0 (maximum value), the binding rate coeffi-
cient increases by a factor of 63.34 from a value of
k
1
equal to 9.473 to
k
2
equal to 600. An
increase in the fractal dimension or the degree of heterogeneity on the biosensor surface leads
to an increase in the binding rate coefficient.
Figure 14.10b
shows the binding of the antibody control (5 ng/mL) to the STX sensor chip in
a Biacore Q biosensor. A dual-fractal analysis is, once again, required to adequately describe
the binding kinetics. The values of (a) the binding rate coefficient,
k
, and the fractal dimen-
sion,
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 14.8
.Itisof
interest to note that, once again, that as the fractal dimension increases by a factor of 2.87
from a value of
D
f1
equal to 1.0446 to
D
f2
equal to 3.0 (maximum value), the binding rate
coefficient increases by a factor of 54.99 from a value of
k
1
equal to 8.183 to
k
2
equal to
450. Once again, an increase in the fractal dimension or the degree of heterogeneity on the
biosensor surface leads to an increase in the binding rate coefficient.
