Etude de différentes méthodes de biofonctionnalisation pour la ...

IV. Réalisation de membranes enzymatiques épaisses pour microcapteurs ENFETs
70
60
(b)
50
C(buffer)=lmM
r°
30
20
C(b u ife r)= 10m M
r-D
10
C(buffer)=50
o 5 lO 15 20 25 30
C(BuChCI) (mM)
Fig. 3. Response of the butyryicholinesterase biosensor versus buffer
concentration. (a)for BuChE-BSA FET: C (bufjèr) =1mM; C (buffer)
=5mM; C (buffer) =10mM; (b) for BuChE-PVA/SbQ FET: C
(buffer) =1mM;
C (buffer) =10mM; AC (buffer) =50mM
Figures 2, represents the sensitivity of two different type ENFETs vs. the pH of the 1 mM
phosphate buffer. Higher sensitivity is obtained at pH equal to 8-8.5 whatever the membrane used. The
same tendency was obtained for acetyicholinesterase based sensors [8, 9],
Figures 3a and 3b represent the sensitivity of ENFETs vs. the concentration of the phosphate
buffer. lt was found firstly that the response of ENFETs could be changed by varying the concentration
of the buffer and secondly that the both enzymatic membranes were more sensitive in 1 mM buffer
(lower concentration tested). lt is noteworthy that a lower concentration would not allow to maintain a
constant ionic strength during liberation of H, which takes place during the enzymatic reaction. In this
context, the pH and the ionic strength selected for further experiments were phosphate buffer of
concentration 1mM at pH=8.O.
3.2. Biosensor calibration
The biosensor calibration curves were presented following two basic methods : first, the steadystate
sensor response was registered (Fig. 4a and 5a) and secondly, the kinetìc response (Fig. 4b and
5b). Fig. 4a and 5a show that the dynamic ranges for both membranes are very similar. In addition, a
very low standard deviation is obtained for the both curves (less than 1%). On opposite, the curves
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