Biomedical Engineering Reference
In-Depth Information
(a)
(b)
(3)
(3)
(2)
(2)
1μA
1μA
(1)
(
1)
0
0
100 200 300 400 500 600
100 200 300 400 500 600
(c)
(d)
(5)
(4)
(7)
(6)
(5)
2μA
4μA
(4)
(1)
(1)
0
0
100 200 300 400 500 600
E (mV vs. Ag/AgCl)
100 200 300 400 500 600
E (mV vs. Ag/AgCl)
Fig. 4.19.
the catalytic electrochemistry of the enzyme electrode with redox po-
lymer: the effect of redox polymer content. Cyclic voltammetry was carried out in
a deoxygenated phosphate buffer containing (1) 0, (2) 1, (3) 2, (4) 6, (5) 10, (6)
15, and (7) 20 mM glucose. The enzyme electrode was prepared by loading with a
2.0
l (BL suspension of a polymer-protein mixture. The ratios of the mixture for
immobilization were redox polymer : GOx : BSA = (
a
) and (
c
) 200 : 50 : 150, (
b
)
and (
d
) 50 : 50 : 150 (mg/ml). The scan rate was 1 mV/s
μ
typical catalytic current with a sigmoidal shape was observed at low redox
polymer content, as shown in Fig. 4.19d. However, peaks were still observed
at high redox polymer content in Fig. 4.19c.
The appearance of these prepeaks can be explained by cyclic voltammetric
simulation. A cyclic voltammetric simulation for the electrochemically me-
diated enzyme reaction has been reported by our group [34]. In this chapter,
the digitally simulated cyclic voltammogram demonstrates that a prepeak is
observed at low substrate concentration, high mediator concentration, and
high enzyme activity. This electrochemical behavior can be elucidated from
the calculated concentration profiles of the mediator and the substrate. The
appearance of the prepeak is due to the depletion of the substrate concentra-
tion in the vicinity of the electrode surface. Hence, the recycling rate of the
redox site is reduced, and the catalytic current increase is suppressed. The
concentration profiles can also elucidate whether the catalytic currents show
a sigmoidal shape or a peak at high glucose concentration.
The observation of such prepeaks has also been reported by Coury and
co-workers in the enzyme electrochemistry of sulfite oxidase mediated by
