Biomedical Engineering Reference
In-Depth Information
enhance the direct electron-transfer rate of Hb. Samili [241] used a nickel oxide nano-
particle to immobilize Hb on a carbon electrode and used the modifi ed electrode to
catalyze H
2
O
2
and O
2
. Hb in the modifi ed electrode showed catalytic activity for the
reduction of H
2
O
2
with a
K
m
app
1.37 mM.
Some non-ionic surfactant, such as Triton X-100, is usually chosen to preserve the
functional state of proteins and to accelerate electron transfer in the supramolecular
complex. A third-generation biosensor for H
2
O
2
can be constructed based on the direct
electrochemistry of Hb by incorporating Hb with Triton-100 at the PG electrode sur-
face [242]. When an aliquot of H
2
O
2
was added into a buffer solution of 0.1 mol L
1
NaAc-HAc (pH 6.0), the current of cathodic peak increased gradually. The catalytic
peak currents were proportional to the concentration of H
2
O
2
in the range from 1.0
10
6
to 1.0
10
4
M. The linear regression equation was
I
(A)
38.59 [H
2
O
2
] (mM)
10
7
mol L
1
when the
signal-to-noise ratio is 3. The
K
m
app
was 4.27 mM for this biosensor.
Some biomembrane-like fi lms can provide a favorable microenvironment for proteins
and enhance direct electron transfer between proteins and electrodes. Poly-3-hydroxy-
butyrate (PHB), a linear polymer of betahydroxylate, is produced within bacterial cyto-
plasm as an energy reserve by a range of prokaryotic cells. Due to its good property of
biodegradability PHB has been widely used as degradable plastics, and has an extensive
application in medicine, membrane technology, and other biotechnologies. Thus, PBS
might be a suitable material to incorporate proteins. The Hb-PHB/PG electrode can show
direct, reversible electrochemistry for heme FeIII/FeII redox couples. The electrochemi-
cal catalytic reductions of hydrogen peroxide (H
2
O
2
), nitric oxide (NO), and trichloro-
acetic acid (TCA) have been observed, showing the potential applicability of the fi lms as
biosensor [243]. A linear dependence between the catalytic current and the concentration
of H
2
O
2
is obtained in the range 6.0
1.12,
r
0.999. The detection limit is estimated to be 3.0
10
7
to 8.0
10
4
M for Hb-PHB/PG electrode.
The linear regression equation is
y
5.95528
0.03541
x
, with a correlation coeffi -
10
7
M with sensitivity of 0.03541
M
1
cient of 0.999. Its detection limit is 2.0
µ
A
µ
H
2
O
2
. The
K
m
app
of Hb-PHB fi lm is calculated to be 1076
M for H
2
O
2
. Electrocatalytic
reduction of TCA can also be tested by the Hb in PHB fi lms. When TCA is added to a
pH 5.0 buffer, the HbFe(III) reduction peak of Hb-PHB fi lm electrodes at about
µ
0.28 V
increased in height, accompanied by a decrease of HbFe(II) oxidation peak. The reduc-
tion peak current is linearly proportional to the concentration of TCA. When the concen-
tration of TCA is larger than 0.04 M, a new reduction peak located at
0.45 V (vs SCE)
is observed, and the peak current increased with the concentration of TCA. Lu [244] also
developed a hydrogen peroxide by immobilizing Hb to a water-soluble polymer, poly-
α
,
β
N-(2-hydroxyethyl)-l-aspartamide] (PHEA) fi lm.
Direct electrochemistry of hemoglobin was observed in stable thin fi lm composed
of a natural lipid (egg-phosphatidylcholine) and hemoglobin on a PG electrode.
Hemoglobin in lipid fi lms shows thin layer electrochemistry behavior. Hemoglobin in
the lipid fi lm exhibited elegant catalytic activity for electrochemical reduction of H
2
O
2
,
from which a mediator-free biosensor for H
2
O
2
could be developed [245]. There was
a linear relation of the current with concentration of H
2
O
2
between 10 and 100
µ
M for
the biosensor. The detection limit is 3.9
µ
M with the signal-to-noise ratio of 3.
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