Biomedical Engineering Reference
In-Depth Information
the electro-reduction of H
2
O
2
, and allowed the construction of an ampero-
metric choline biosensor immobilizing ChlOx on the PB-FePO
4
nano-
structures. h e biosensor exhibited a rapid response (ca. 2 s), low detection
limit (0.4 μM), wide linear range (2 μM to 3.2 mM), high sensitivity (
75
μA mM
−1
cm
−2
), as well as good stability and repeatability. Also, the com-
mon interfering species, such as ascorbic acid, uric acid and 4-acetamido-
phenol did not cause observable interference.
During recent decades, organophosphorus (OP) compounds have been
received much attention due to their harmful ef ects on human health.
h erefore, the development of fast and sensitive detection methods has
become more urgent. In 2009, Sajjadi
et al.
[61], developed a PB-modii ed
SPEs coupled with ChlOx for detection of paraoxon as inhibitor. h e con-
centration of H
2
O
2
produced by ChlOx was electrochemically determined
by the PB-modii ed electrode poised at −50 mV versus the internal screen-
printed Ag pseudo-reference electrode. h e decrease in current caused by
the addition of inhibitor was used for evaluation of paraoxon concentra-
tion. For an incubation time of 5 min, the biosensor response was linear
from 0.1 to 1 μM of paraoxon with a detection limit of 0.1 μM.
∼
12.4.1.8
Acetilcholinesterase and Butyrylcholinesterase
Acetylcholinesterase (AChE, EC 3.1.1.7) is a serine protease that hydro-
lyzes the neurotransmitter acetylcholine, and belongs to the carboxyles-
terase family. h e active site of AChE comprises two subsites - the anionic
site and the esteratic subsite. h e structure and mechanism of action of
AChE have been elucidated from the crystal structure of the enzyme.
AChE is found at mainly neuromuscular junctions and cholinergic brain
synapses, where its activity serves to terminate synaptic transmission.
Butyrylcholinesterase (BuChE, EC 3.1.1.8) is a non-specii c cholinester-
ase enzyme that hydrolyses many dif erent choline esters. In humans, it is
found primarily in the liver and is encoded by the BCHE gene. It is very
similar to the neuronal acetylcholinesterase. Recently, biosensor tech-
niques based on the inhibition of AChE and BChE activity by OPs and
toxins have gained considerable attention due to the advantages of sim-
plicity, rapidity, reliability and low cost devices. In addition, the challenges
of biohazards and bioterrorism, especially the need for early detection of
nerve agents have contributed to the use of such approaches.
In 2010, Sun and Wang [62] developed a novel acetylcholinesterase
AChE biosensor based on dual-layer membranes (a Chi membrane and
a PB membrane) modifying a GCE. Before biosensor operation, the Chi
enzyme membrane was quickly i xed on the surface of PB/GCE with an
