Biomedical Engineering Reference
In-Depth Information
2-propanol using the
Pesika et al. (2002)
method. They performed the amperometric
measurements using a three electrode cell. They used an enzyme working electrode, a plati-
num wire counter electrode, and a Ag/AgCl reference electrode. Measurements were made at
35
C and at a fixed potential of 0.4 V. The SEM (scanning electron microscope) indicated
that the surface of their ZnO particles was rough, and consisted of smaller particles. These
primary small nanoparticles were interconnected with each other and formed larger second-
ary particles. This indicates the fractal nature of these ZnO nanoparticles. An additional
advantage of this rough or fractal nature of these ZnO nanoparticles provides for a larger
ratio of surface to volume ratio, thereby making it more feasible to immobilize the GO
x
.
Ren et al. (2009)
also evaluated the influence of pH in the 4.0-9.0 range on the biosensor per-
formance. They obtained the pH optimum at 6.8, which is also close to the pH optimum for
free GO
x
. Thus, a pH of 6.8 for the phosphate buffer was selected.
These authors also analyzed the influence of temperature (in the 10-70
C range) on their bio-
sensor performance for the 2.8 mmol/L concentration of glucose solution. An optimum tem-
perature of 45
C was noted; at higher temperatures GO
x
was denatured.
Ren et al. (2009)
selected a temperature of 35
C in order to keep it compatible with the human body
temperature.
Ren et al. (2009)
also noted an interesting photovoltaic effect of the ZnO nanoparticles on
their biosensor performance. On irradiating their biosensor with UV light, a maximum cur-
rent response was obtained after 2 h when compared with results with normal light. However,
after 2 h the current declined presumably, according to these authors, due to enzyme (GO
x
)
denaturation.
Finally, the authors conclude that they have achieved a simple and effective method for bio-
sensor fabrication. The structure of the glucose oxidase is maintained after conjugation with
the ZnO nanoparticles. This is confirmed by the UV-spectrum and CD analysis. The enzyme
electrode with the ZnO particles showed a significant improvement in their biosensor perfor-
mance when compared with the enzyme electrode without the ZnO particles. Also, the pho-
tovoltaic effect of ZnO nanoparticles enhances the catalytic activity of the glucose oxidase
enzyme, leading to an improvement of their enzyme electrode performance, and subsequently
to an improvement in their biosensor performance.
3.2.11 Fabrication of a Highly Sensitive Glucose Biosensor Using an Osmium Complex
and Glucose Oxidase (
Salimi et al., 2009
)
Salimi et al. (2009)
have recently used a novel osmium complex as an electrocatalyst for the
electroreduction of oxygen and H
2
O
2
at relevant physiological conditions (pH). These
authors used single-walled carbon nanotubes (SWCNTs), and reversibly adsorbed 1,4,8,12-
tetraazacyclotetradecane osmium (III) chloride (Os(III)Cl
2
)ClO
4
on the SWCNTs using
