Biomedical Engineering Reference
In-Depth Information
60
20
40
20
0
(i)
18
(iv)
16
(iii)
20
20
(ii)
14
50
60
70
Time/s
0
150
300
450
600
600
400
200
0
200
(a)
E
/mv
(b)
Time/s
FIGURE 16.5
(a) Cyclic voltammograms of HRP enzyme electrode in (i) 0.02 M pH 7.0 PBS, (ii) (i)
1.0 mM catehol, (iii) (ii)
0.3 mM H
2
O
2
, and (iv) (ii)
1.0 mM H
2
O
2
at 100 mV s
1
and (b) typical cur-
rent-time curve for the sensor upon successive addition of 0.08 mM H
2
O
2
to 0.02 M pH 7.0 PBS containing
1.0 mM catehol at an applied potential of
150 mV. Inset: a magnifi cation of the second addition of H
2
O
2
(adapted from [35]).
H
2
O
2
to the solution, the reduction peak current increases dramatically and the oxida-
tion peak current decreases dramatically (curves (iii) and (iv) in Fig. 16.5a), due to the
effi cient electrocatalytic reduction of catechol to H
2
O
2
at the enzyme electrode. Figure
16.5b shows the typical time response curve of the titania sol-gel-based hydrogen per-
oxide biosensor. Another titania sol-gel-based H
2
O
2
biosensor was also presented by
immobilizing Hb as a catalyst in titania sol-gel matrix [107]. This H
2
O
2
sensor exhib-
ited a fast response (less than 5 s) and sensitivity as high as 1.29 mA mM
1
cm
2
. The
linear range for H
2
O
2
determination was from 5.0
10
7
to 5.4
10
4
M with a
10
7
M. Narang
et al.
[80] reported a glucose biosensor by
immobilizing GOD between two sol-gel layers (sandwich). Using the advantages of
ormosils Pandey
et al.
[28] reported a glucose biosensor based on the immobilization
of GOD in sol-gel glasses derived from 3-aminopropyltrimethoxy silane and 2-(3,4-
epoxycyclohexyl)-ethyltrimethoxy silane. An organophosphorus pesticide amperomet-
ric biosensor has been reported by immobilizing the AChE in TEOS [108]. Similarly
in recent years several amperometric biosensors have been reported based on sol-gel-
modifi ed surfaces, which can be found in reviews [3, 16, 22, 69, 98].
Electrochemical biosensors can be divided into mediated and non-mediated biosen-
sors. Biosensors that do not require the participation of redox molecules with reversible
electrochemistry are referred to as non-mediated biosensors, whereas the participation
of redox mediators in signal transduction generates a category of mediated biosensors.
detection limit of 1.2
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