Biomedical Engineering Reference
In-Depth Information
TABLE 14.5
Biosensors Prepared by AChE or AChE/ChOD for Organophosphorus Pesticide Detection
Signal
Transducers
Immobilization Method
of Enzyme
Enzymes
Type
Ref.
AChE
Screen-printed
carbon electrodes
AChE was immobilized on dialdehyde or
polyethyleneimine by physical adsorption
Amperometric
52
AChE
GCE
AChE is immobilized on the negatively charged
CNT surface by alternatively assembling a cationic
poly(diallyldimethylammonium chloride) (PDDA)
layer and an AChE layer
Amperometric
53
AChE
Spectrophotometer
AChE was immobilized on a sol-gel fi lm interfaced
with another chromoionophore (ETH5294) (CM)
doped sol-gel fi lm
Optical
54
AChE
pH-sensitive PVC
membrane electrode
AChE was immobilized on the pH-sensitive PVC
membrane with deposited plasma-polymerized fi lm
Potentiometric
55
AChE/ChOD
Oxygen electrode
AChE and ChOD were coimmobilized on pHEMA
membranes
Amperometric
56
AChE/ChOD
Pt electrode
AChE and poly(ethylene glycol)-modifi ed ChOD
were physically coimmobilized in a PVC cryogel
membrane
Amperometric
57
AChE/ChOD
Pt wire sealed
in glass
AChE and ChOD were codeposited with an
electropolymer
Amperometric
58
AChE/ChOD
Carbon ink printed
electrode
AChE and ChOD were immobilized on the CNTs by
carbodiimide chemistry using 1-ethyl-3-(3-dimethy
laminopropyl)carbodiimide (EDC) as the coupling
agent
Amperometric
59
AChE/ChOD
Ferrophthalocyanine
chemically
modifi ed carbon-
paste electrode
AChE and ChOD were coimmobilized onto the
surface of a dialysis membrane
Amperometric
60
14.1.1.4 Horseradish Peroxidase
HRP, donor H
2
O
2
oxidoreductase (E.C. 1.11.1.7), is extracted from the roots of horseradish. HRP
contains two different types of metal centers, iron(III) protoporphyrin IX (usually referred to
as “heme group”) and two calcium atoms (Figure 14.1). Both are essential for the structural
and functional integrity of the enzyme. Small molecules such as carbon monoxide, cyanide,
fl uoride, and azide bind to the heme iron atom at the distal site giving six-coordinate peroxidase
complexes [61].
As a peroxidase, HRP can catalyze the hydrogen peroxide-dependent one-electron oxidation of
a wide variety of substrates [62]. Furthermore, most reactions catalyzed by HRP can be expressed
in Reaction 14.15, in which AH
2
and AH·represent a reducing substrate and its radical product,
respectively. Typical reductive substrates include aromatic phenols, phenolic acids, indoles, amines,
and sulfonates [61].
HRP
2AH
.
H
2
O
2
+
2AH
2
2H
2
O
+
(14.15)
Based on this reaction, HRP can be used to prepare many biosensors for quantitative deter-
mination of aromatic phenols, phenolic acids, indoles, amines, sulfonates, and hydrogen peroxide.
Examples of such biosensors are listed in Table 14.6.
