Biomedical Engineering Reference
In-Depth Information
reduction peak current and the H
2
O
2
concentration behave in a linear relationship.
The linear regression equation is I (
2.29 with a correlation
coeffi cient of 0.9972. When the concentration of H
2
O
2
is higher than 7.0
µ
A)
6.60[H
2
O
2
] (
µ
M)
10
4
M,
a response plateau is observed, showing the characteristics of the Michaelis-Menten
kinetic mechanism. The
K
m
app
value was found to be 8.98
10
4
M for the Hb/sol-
gel fi lm-modifi ed CPE.
Direct electron transfer of haemoglobin can also be achieved in Hb/montmorillo-
nite (MMT)/polyvinyl alcohol multi-assembly at a pyrolytic graphite (PG) electrode.
Accordingly, a novel nitric oxide (NO) biosensor is proposed [238]. A pair of well-
defi ned peaks can be observed for the CV response of Hb in an MMT/PVA multi-
assembly at a PG electrode surface at pH 5.5 (anodic peak at
0.382 V and cathodic
peak at
0.333 V). In the presence of NO, a new peak appears at the potential of
783 mV, in the negative direction of the redox pair of Hb. Notably, no corresponding
signal is visible at a bare electrode or an electrode modifi ed with MMT alone under
the same condition. Thus, this peak can be attributed to the reduction of NO catalyzed
by the heme of Hb. Moreover, the peak current apparently increases along with NO
concentrations which will be employed in the following NO measurements. The peak
current of NO reduction is observed to be linearly proportional to the NO concentra-
tion in the range from 1.0
10
6
to 2.5
10
4
M. The detection limit is estimated to
10
7
M, defi ned from a signal-to-noise ratio of 3. The
K
app
is estimated to be
be 5.0
81.4
M.
Gold nanoparticles are the most intensively studied and applied metal nanoparticles
in electrochemistry owing to their stable physical and chemical properties, useful cata-
lytic activities, and small dimensional size. A novel Hb-based H
2
O
2
sensor has been
constructed on a gold nanoparticles-modifi ed ITO [239]. Although the direct electro-
chemical response of Hb can be observed on some electrodes, no characteristic peak
for Hb appears in the cyclic voltammogram recorded with the Hb/Au/ITO electrode
in a PBS solution at pH 7.0. While 2 mM H
2
O
2
was present in the solution, noticeable
cathodic currents could be observed starting at
µ
0.10 V, indicating the reduction of
H
2
O
2
on this electrode. Gold nanoparticles can improve electron transfer kinetics of
Hb and enhance the reduction current for H
2
O
2
because of its larger conductive area,
good biocompatibility, and useful catalytic activities. The catalytic current is linearly
proportional to H
2
O
2
concentration from 1
10
3
M with a correlation
coeffi cient of 0.9995. The linear regression equation is expressed as
I
(A)
10
5
to 7
0.2977
[H
2
O
2
] (mM)
0.0642. The detection limit (S/N
3) on the Hb/Au/ITO electrode
10
6
M. Besides gold nanoparticles, Hb can also be absorbed
by a compound composited with gold nanoparticles and other materials. Haemoglobin
has been adsorbed onto a chitosan-stabilized gold nanoparticles (Chit-Aus)-modifi ed
Au electrode via a molecule bridge like cysteine. The resultant electrode displayed an
excellent electrocatalytic response to the reduction of H
2
O
2
, long-term stability, and
good reproducibility [240]. The Hb/Chit-Aus/Cys/Au electrode showed increasing
amperometric responses to H
2
O
2
with a linear range from 13 to 0.74 mM. The
K
m
app
value for Hb activity of the Hb/Chit-Aus/Cys/Au electrode to H
2
O
2
was determined
to be about 1.4 mM. Besides these, metal oxide nanoparticles are also usually used to
is estimated to be 4.5
Search WWH ::
Custom Search