Biomedical Engineering Reference
In-Depth Information
transfer via radial diffusion (
Pletcher, 1991; Amatore, 1995
). This is due to one dimension
being less than 50
m
m in size. This increase in mass transfer, the authors claim, permits
steady-state current responses, and allows determination in quiescent sample conditions.
Besides, continuous monitoring applications are now feasible.
Pemberton et al. (2009)
report that ultramicroband electrodes using the SPCE method have
been used by
Chang and Zen (2006a)
. Because of the low ohmic drop for these electrodes,
Chang and Zen (2006b)
used these electrodes for the voltametric determination of trace
nitrite ions in low ionic strength solutions.
Pemberton et al. (2009)
wanted to analyze water-based COPG/GOD-containing carbon ink
formulation to see the possibility of fabricating glucose microband biosensors possessing
microelectrode-type behavior. They also wanted to optimize the performance of their
resulting biosensors. The authors report that their devices operate by producing H
2
O
2
(hydro-
gen peroxide) from glucose. This H
2
O
2
is then electrocatalytically oxidized via the CoPC
mediator. The authors report that they were careful to select and apply a potential of
þ
0.4 V potential is suffi-
ciently positive to permit the electrocatalytic oxidation of H
2
O
2
. It is also sufficiently low to
avoid any loss of sensitivity that is observed at higher potentials. Also, the enhanced mass
transport owing to the small size of the microbands (sufficiently small size in at least one
dimension) yields an enhanced current density. This leads to better signal-to-noise ratios.
0.4 V for the operation of their devices. They emphasize that the
þ
Pemberton et al. (2009)
report that their biosensors may simply be dipped in solution, which
leads them to believe that their biosensor may be used as a versatile portable device. Further-
more, owing to the ability of their biosensors to attain steady-state responses at low current,
their microband biosensor may be used in continuous process-monitoring applications. These
authors indicate that the single screen-printing step used in their biosensor fabrication process
is relatively low cost, and could be used at a mass production scale. Finally,
Pemberton et al.
(2009)
point out that SPCE-based biosensors may be used to detect analytes other than glu-
cose (
Hart et al., 2007
).
3.2.9 Fabrication of a Highly Sensitive Glucose Sensor Using Immobilized Enzymes
(
Lu et al., 2007
)
Lu et al. (2007)
have recently fabricated a highly sensitive glucose biosensor using enzymes
immobilized in exfoliated graphite nanoparticles Nafion membrane. These authors emphasize
that nanotechnology provides the opportunity to increase the sensitivity, selectivity, and
response speed of biosensors. Because of their unique chemical, physical, and optoelectronic
properties nanomaterials have been used in different biosensor applications (
Luo et al.,
2006
).
Lu et al. (2007)
report that the incorporation of CNTs and fullerenes in biosensor
applications have substantially increased their sensitivity and response speed owing to their
