Biomedical Engineering Reference
In-Depth Information
Bulk solution
Catalase
H
2
O
2
H
2
O O
2
Pesticide
GOD
Glucose
Electrode surface
Glucono-
lactone
O
2
GOD
Glucose
Pesticide
Pesticide
H
2
O
H
2
O
2
Antibody
Antibody
HRP
(ox)
HRP
(red)
e
FIGURE 2.11
Schematic diagram of the separation-free immunosensor principle for pesticides (H
2
O
2
detected at
50 mV vs Ag/AgCl via direct enzymatic reduction of HRP) (adapted from [98]).
channeling via the HRP electrode. The linear detection range was 0.01-1.0 ng mL
1
(Fig. 2.11). By employing the above working principle, another amperometric immu-
nosensor for chlorosulfuron has been reported [99]. The linear detection of chlorosul-
furon was 0.01-1 ng mL
1
. The recombinant single-chain antibody (scAb) fragments
were also used as a recognition receptor in the development of the atrazine immuno-
sensor using SPE [96]. This real-time and separation-free FIA system was capable of
measuring atrazine with a detection limit of 0.1 ng mL
1
. Some other recent reports on
pesticide biosensors could be found in a review [9] and Table 2.1.
2.4.3 Regeneration of pesticide immunosensors
Immunoaffi nity-based biosensor performance for repeated pesticide detection is
dependent on the binding effi ciency of the immobilized antibody. The mild and effec-
tive dissociation method can retain the antibody affi nity for longer. For the regenera-
tion either highly acidic (pH 1.8 to 3.8) or basic (pH 9.5-11) buffers or buffers along
with organic solvents or enzymes such as pepsin (2 mg mL
1
, pH 1.9 solution) was
used. In a report by Fránek
et al.
[118] 0.04 M NaOH, 0.1 M glycine/HCl and 0.1 M
NaOH were suitable dissociation buffers for effective regeneration of atrazine, 2,4-D,
and simazine, respectively. One percent DMSO in pH 2.3 Gly-HCl buffer showed 97%
dissociation and the immobilized antibody retained binding affi nity to carry out 14
reproducible assays for ethyl parathion [13]. Some of the reports used diluted HCl for
the dissociation of immunocomplexes [91]. 0.04 M HCl showed effi cient dissociation
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