Detection of Gases on Biosensor Surfaces - Biosensors and Biosensor Kinetics - page 288

Table 10.10: Binding and dissociation rate coefficients for different methanol concentrations to a
polyimide thin layer biosensor ( Manera et al., 2006 ).

Methanol
Concentration
(ppm) k k 1 k 2 k d

3320 0.004354 0.000648 na na 0.006427 0.000327

3320 0.001535 0.000131 na na 0.01363 0.00133

4980 0.02389 0.00117 na na 0.005807 0.000173

4980 0.007511 0.0014 0.005371 0.00132 0.01690 0.00023 0.007229 0.000492

Table 10.11: Fractal dimensions for the binding and dissociation phase for different methanol
concentrations to a polyimide thin layer biosensor ( Manera et al., 2006 ).

Methanol
Concentration
(ppm) D f D f1 D f2 D fd

3320 2.3352 0.1164 na na 2.4418 0.09514

3320 1.6418 0.08864 na na 2.7084 0.1336

4980 2.6894 0.05266 na na 2.1872 0.05014

4980 2.3242 0.1596 1.7776 0.4490 0.01690 0.00023 2.9855 0.05412

Figure 10.15b shows a repeatability run. In other words, it shows the binding and dissociation
of 3320 ppm methanol in air (once again) to a polyimide thin layer biosensor ( Manera et al.,
2007 ). Once again, a single-fractal analysis is required to adequately describe the binding and
dissociation 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 dissociation rate coefficient, k d , and the frac-
tal dimension for the dissociation phase, D fd , are given in Tables 10.10 and 10.11 . In this
case, the affinity, K ( ¼ k / k d ) value is 0.113.

The affinity, K values for the two repeatability runs are very different, 0.677 and 0.113,
respectively. They differ by a factor of 6.0. As expected, and in accord with the affinity
values, the dissociation rate coefficient values (0.004351; 0.00154) for the first and the
repeatability runs are also different. They are presented in brackets above.

Figure 10.16a shows the binding and dissociation of 4980 ppm methanol in air to a polyimide
thin layer biosensor ( Manera et al., 2007 ). A single-fractal analysis is adequate to describe
the binding and 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 coeffi-
cient, k d , and the fractal dimension for the dissociation phase, D fd , are given in Tables 10.10
and 10.11 . In this case the affinity, K ( ¼

k / k d ) is equal to 4.11.