Continuous glucose monitoring using enzyme-immobilized platinized diamond microfiber electrodes

Article abstract of DOI:10.1016/j.electacta.2003.10.026

A sensitive and stable glucose biosensor for in vivo monitoring has been developed using boron-doped diamond microfiber (BDDMF) electrodes. The electrodes were modified with platinum nano-particles to detect H ₂O₂, which was enzymatically produced by glucose oxidase (GOx) immobilized on the electrode surface. The platinum-modified BDDMF (Pt-BDDMF) electrodes exhibited much higher sensitivity compared to Pt-microfiber electrodes, Pt electrodes and Pt-modified diamond thin film electrodes. Deposition conditions for Pt nano-particles on the BDDMF electrodes and immobilization of GOx were optimized. GOx/overoxidized polypyrrole (OPPy)/Pt-modified BDDMF electrodes were applied for continuous interference-free glucose monitoring. Amperometric measurements of glucose showed a linear response in the range of 1-70 mM, with an R.S.D. of 3.7% for five injections of 100 μM glucose. The electrodes exhibited good stability over 3 months with no detected anodic current for ascorbic acid (AA), which is an interfering compound.

Full text of DOI:10.1016/j.electacta.2003.10.026

Electrochimica Acta 49 (2004) 2069–2076
Continuous glucose monitoring using enzyme-immobilized platinized
diamond microfiber electrodes
a
a
b
c,∗,1
H. Olivia , B.V. Sarada , K. Honda , A. Fujishima
a
Department of Applied Chemistry, The University of Tokyo, 113-8656 Tokyo, Japan
b
Department of Chemistry and Earth Science, Yamaguchi University, 753-8512 Yamaguchi, Japan
c
Kanagawa Advanced Science and Technology (KAST), KSP Bldg. West 614, 3-2-1 Sakado, Takatsu-ku, Kawasaki-shi, 213-0023 Kanagawa, Japan
Received 7 July 2003; received in revised form 6 October 2003; accepted 28 October 2003
Abstract
A sensitive and stable glucose biosensor for in vivo monitoring has been developed using boron-doped diamond microfiber (BDDMF)
electrodes. The electrodes were modified with platinum nano-particles to detect H , which was enzymatically produced by glucose oxidase
GOx) immobilized on the electrode surface. The platinum-modified BDDMF (Pt-BDDMF) electrodes exhibited much higher sensitivity
2
O
2
(
compared to Pt-microfiber electrodes, Pt electrodes and Pt-modified diamond thin film electrodes. Deposition conditions for Pt nano-particles
ontheBDDMFelectrodesandimmobilizationofGOxwereoptimized. GOx/overoxidizedpolypyrrole(OPPy)/Pt-modifiedBDDMFelectrodes
were applied for continuous interference-free glucose monitoring. Amperometric measurements of glucose showed a linear response in the
range of 1–70 mM, with an R.S.D. of 3.7% for five injections of 100 ␮M glucose. The electrodes exhibited good stability over 3 months with
no detected anodic current for ascorbic acid (AA), which is an interfering compound.
©
2003 Elsevier Ltd. All rights reserved.
Keywords: Diamond; Microfiber electrode; Platinized; Glucose; Enzymatic; H2O2
1
. Introduction
Boron-doped diamond electrodes outperform metal elec-
trodes in terms of stability, chemical inertness, wide poten-
tial window and low background current [6–8]. Combining
the superior properties of diamonds with the merits of
using microelectrodes, such as low current, small sample
volume, low noise level and fast response [9–12], diamond
microfiber electrodes are very promising for continuous
analysis.
Despite the several superior properties of diamond elec-
trodes mentioned above, they have several limitations com-
pared to metal electrodes such as slow kinetics for reactions
involving adsorption and multi-electron transfer processes,
including hydrogen and oxygen evolution reactions. How-
ever, since the slow rate of hydrogen and oxygen evolution
reactions result in a wide potential window [13,14], this can
be considered an advantage for using diamond electrodes,
especially in aqueous media.
Glucose, a ready source of energy, plays an important role
in energizing the human body since it is instantly oxidized
to release energy. Normal concentrations of glucose in blood
are less than 6.1 mM and a large excess of blood glucose
(higher than 7.0 mM) is generally diagnosed as a symptom
of diabetes [1]. Therefore, continuous and fast monitoring of
glucose has become a major concern throughout the world
[2,3], especially for the control and treatment of diabetes.
Electrochemical sensors have dominated over other de-
tectors used for daily glucose monitoring due to their high
accuracy, low cost, rapidity, simplicity and better detection
limits. The majority of commercial sensors available are
platinum-printed electrode-based sensors [4,5] and most are
for single-use, possibly due to adsorption problems on the
platinum surface.
Oxidation and reduction reactions of H2O2, a main prod-
uct of enzymatic glucose decomposition with glucose oxi-
dase (GOx), are also multi-electron transfer processes.
∗
Corresponding author. Tel.: +81-44-819-2020;
fax: +81-44-819-2038.
GOx
E-mail address: fujishima@kast.or.jp (A. Fujishima).
glucose + O2 + H2O −→ gluconic acid + H2O2
1
ISE member.
0
013-4686/$ – see front matter © 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.electacta.2003.10.026

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H. Olivia et al. / Electrochimica Acta 49 (2004) 2069–2076
+
−
trode surface resulting in an inhomogeneous coverage which
H2O2 → O2 + 2H + 2e
degrades the reproducibility, sensitivity and selectivity [21].
We have previously reported the use of overoxi-
dized polypyrrole (OPPy) modified BDDMF electrodes
for interference-free dopamine detection [22]. Oxidized
polypyrrole is a positively charged conducting polymer
and overoxidation of this film results in an increase in
carbonyl and carboxylic functional groups that reject an-
ions such as ascorbate at physiological pH. OPPy-modified
diamond microelectrodes show high selectivity and good
stability for long-term dopamine detection. In this study, a
GOx/OPPy/Pt-modified BDDMF electrode is demonstrated
for the selective detection of glucose and is free from
ascorbic acid interference.
+
−
H2O2 + 2H + 2e → 2H2O
Since diamond is inactive for these reactions, some im-
provements are necessary for utilizing diamond microfibers
for enzyme-based biosensors. Tatsuma et al. [15] reported
the use of a heme peptide and horseradish peroxidase
(
a redox enzyme) based on a direct electron transfer
mechanism between a diamond electrode and redox en-
zyme. Another promising approach is the deposition of
metal nano-particles that have catalytic activity for H2O2
oxidation-reduction reactions. The use of platinized carbon
microelectrodes was previously reported by Reynolds and
Yacynych [16]. Pt particles were loaded on the electrode
surface to increase the electroactive area thereby increas-
ing the signal-to-background ratio (S/B), and to lower the
H2O2 detection potential so that the electrode fouling prob-
lem could be largely eliminated [17]. However, the linear
range of the calibration curve obtained from amperometric
measurements for glucose using these electrodes in a batch
system was limited to the low mM range [16,18] and did
not cover higher glucose concentrations (ca. 10 mM), which
are typical of blood glucose levels in diabetic patients.
In the present work, we report for the first time the use of
boron-doped diamond microfiber (BDDMF) electrodes for
the continuous monitoring of glucose. However, we have
not performed any in vivo detection using real sample, and
this work focuses on the electrode preparation and opti-
mization of measurement conditions for glucose monitoring.
Microfiber was chosen as the microelectrode geometry be-
cause of its simple fabrication (compared to microarray or
microband electrodes) and relatively high current response
2. Experimental
2.1. Diamond deposition
Conductive polycrystalline diamond was deposited using
a microwave plasma chemical vapor deposition (MPCVD)
system (ASTeX Corp., Woburn, MA) at a microwave power
of 3000 W for 3 h on pre-etched and pre-nucleated tungsten
fibers (∅ 30 ␮m), as previously described [22]. The dia-
mond fiber was then sealed in a glass capillary using low
viscosity epoxy. Ohmic contact to the microelectrode was
given using mercury and copper wire. The electrodes were
firstly cleaned by potential cycling between −0.1 and 1.5 V
in 0.1 M phosphate buffer solution (PBS) to remove any im-
purities that may have been deposited on the surface of the
diamond during the fabrication process.
BDD microfiber electrodes were characterized using
Scanning Electron Microscopy (SEM), Raman spectroscopy
and cyclic voltammetry. SEM images were taken using a
JEOL JSM-5400 microscope. Raman measurements were
(
compared to microdisc electrodes). Moreover, the use of
microfiber electrodes can minimize sample volume, or can
be directly injected into the body, which is impossible with
plate microarray electrodes.
+
performed using a Renishaw 2000 System with Ar laser
Here, we will mainly discuss the modification of a BD-
DMF electrode with platinum nano-particles and its use for
detection of enzymatically produced H2O2. For compari-
son, a series of experiments were also performed using a
Pt-microfiber, a Pt-deposited diamond thin film and a bulk
polycrystalline Pt. Pt-deposited diamond microfiber elec-
trodes exhibit significantly higher sensitivity and stability
and therefore are very promising as enzymatical biosensors
that involve H2O2 reactions.
In vivo detection of glucose generally suffers from some
interference problems, especially due to the presence of
ascorbic acid (AA), which exists at significant concentra-
tions and has similar oxidation potentials as that of enzy-
matically produced H2O2. To overcome this interference
problem, electropolymerization of polymers on the electrode
surface has been widely investigated [19,20]. This method
has been shown to be a promising approach for achieving
higher quality sensing using microfiber electrodes, rather
than Nafion membranes that are dip-coated onto the elec-
excitation (514.5 nm).
2.2. Platinum loading
Platinum deposition on the diamond microelectrodes was
performed electrochemically in 0.1 M H2SO4 containing
100 ␮M K2PtCl (Wako) by cycling between the potentials
6
−
1
of −0.2 and 1.2 V at 50 mV s under nitrogen bubbling con-
ditions. The electrode was then cycled between the same po-
tentials in H2SO4 until a stable voltammogram was achieved,
indicating the complete cleaning of the Pt active area.
2.3. Modification with OPPy
Polymerization of pyrrole was then performed on the
Pt-BDDMF electrodes by fixing a potential of 0.7 V for
15 min in 10 mM KCl containing 20 mM pyrrole (TCI). The
polypyrrole layer was overoxidized at 0.7 V for 1 h. The
electrode was stored in 0.1 M PBS for 2 days in order to

H. Olivia et al. / Electrochimica Acta 49 (2004) 2069–2076
2071
increase the porosity and stability of the OPPy layer. The
responses toward 1 mM H2O2 and 1 mM AA were checked
before and after polymerization.
2
.4. Immobilization of glucose oxidase
Glucose oxidase was deposited on the OPPy/Pt/BDD elec-
trode by immersing the electrode for 45 s in 2 ml of 25 mM
PBS containing 20 mg bovine serum albumine (BSA), an
appropriate amount of GOx (the optimization process is de-
tailed in Section 3) and 100 ␮l of 5% glutaraldehyde (GA)
as a cross-linker. The electrode was then stored in 0.1 M
PBS over-night to remove any excess.
Amperometric measurements were performed in a batch
system with the solution volume of 10 ml, at a fixed potential
of 0.475 V in 0.1 M PBS (pH 7.2) under stirring conditions.
The platinum electrode and Standard Calomel Electrode
Fig. 2. Cyclic voltammogram for 0.1 M H2SO4 at Pt-BDDMF electrode.
−
1
Sweep rate: 50 mV s
.
Pt-modified BDDMF). When a glucose molecule approaches
the vicinity of the electrode, it is firstly decomposed by GOx
to produce H2O2, which, in turn, penetrates into the OPPy
layer and reaches the surface of the Pt nano-particles where
the oxidation and reduction reactions of H2O2 take place.
(SCE) served as counter and reference electrodes, respec-
tively. Deionized water, which was further purified via a
Milli-Q unit was employed to make all solutions. H2O2 and
AA (Wako) solutions were freshly prepared prior to each
set of measurements. d-(+)-Glucose (TCI) was stored in
3.1. Optimization of Pt loading
◦
0
.1 M PBS at 4 C for 24 h in order to allow mutarotation.
BSA was purchased from Sigma and GOx was purchased
Fig. 2 shows the cyclic voltammogram obtained for 0.1 M
−
1
from Toyobo (activity of 148 U mg ). All electrochemical
−1
H2SO4 with Pt-BDDMF at a scan rate of 50 mV s . This
voltammogram exhibited a typical feature similar to that ob-
tained for the bare Pt microelectrode (data not shown). After
cleaning by sweeping between the potentials of −0.1 and
◦
measurements were performed at room temperature (25 C)
in 0.1 M PBS using a potentiostat and function generator
(Hokuto-Denko HA-150 and HB-III, respectively) and an
X–Y recorder (Riken Denshi F-5C).
1
.2 V for ca. 100 cycles in 0.1 M H2SO4, the voltammetric
responses became stable, indicating the complete cleaning
of the Pt surface and the strong adherence of the platinum
particles on the diamond surface.
3
. Results and discussion
Fig. 1 shows the configuration of the electrode devel-
oped in this present study for glucose detection (GOx/OPPy/
The real surface area for the exposed Pt atoms was esti-
mated from the charge density of the hydrogen desorption
Fig. 1. Illustration of the configuration of glucose detector: GOx/OPPy/Pt-BDDMF.

2
072
H. Olivia et al. / Electrochimica Acta 49 (2004) 2069–2076
from the background CV. Since the average distance be-
tween each particle (estimated to be 1.12 ␮m from N )
1
h
was getting too close, the reactant diffusion layers were
assumed to overlap, resulting in decreased electrochemical
activity.
In comparison, after 20 min deposition, the amount
1
3
of Pt loaded on the BDDMF was less (3.22 × 10
−
2
Pt atoms cm ) with D
= 400 nm and N
=
20 min
20 min
6
−2
6
.0×10 particles cm . The average distance between each
particle for this electrode (4.09 ␮m from N20 min) was 3.7
times wider than for the 1 h deposition and was considered
to be closer to the optimum value [25], allowing an ideal
spherical diffusion to occur in the vicinity of each particle.
In this case, the electrode can be considered as a microarray
of platinum particles that are uniformly distributed on the
diamond microfiber electrode.
2
Fig. 3. Plots of Pt real surface area (cm ) exposed on the surface of
2
Pt nano-particles in unit BDDMF electrode area (1 cm ), as a function
of Pt deposition time. Pt real surface area was electrocatalytically ac-
tive real surface area on Pt nano-particles, that was calculated from the
charge density of hydrogen desorption reaction using standard value of
−2
2
10 ␮C cm for polycrystalline Pt in 0.1 M H2SO4.
Comparison experiments were performed using a bare Pt
microelectrode with a 50 ␮m diameter, a Pt nano-particle
deposited diamond macroelectrode, and a polycrystalline
Pt macroelectrode with 1 mM H2O2 in 0.1 M phosphate
buffer. The S/B values calculated from the CVs are sum-
marized in Fig. 6. The Pt-BDDMF microelectrodes and
Pt-microfiber electrodes had higher S/B values than the
Pt-modified diamond thin film electrode and bare Pt
macroelectrode, respectively. The superiority of these two
electrodes can be attributed to the intrinsic properties
of the fiber-shaped microelectrodes, including the non-
planar diffusion profile, low background current and high
sensitivity.
reaction between 0 and −0.2 V in background CV, using
−
2
a standard value of 210 ␮C cm which corresponded to a
15
−2
calculated value of 1.30×10 atoms cm for the polycrys-
talline Pt electrode [23,24]. It was observed that the real sur-
face area of the Pt nano-particles increased linearly with de-
position time (Fig. 3). Background current also increased as
the amount of Pt deposition increased. Therefore, in order to
optimize the loading amount, the ratios of signal current for
H2O2 oxidation to background (S/B) were examined. The
S/B values obtained at 0.6 V achieved its maximum value
with a deposition time of 20 min (Fig. 4), indicating that it
was the optimum Pt deposition time.
Interestingly, in Fig. 6, the Pt-deposited diamond electrode
gave a higher sensitivity than the polycrystalline Pt electrode
for both the micro and macroelectrode. In order to verify the
effect of the catalysis-shape, the specific activities for H2O2
oxidation were examined.
Fig. 5A and B show the SEM images of the Pt-modified
diamond microfiber electrodes after 1 h and 20 min depo-
sition, respectively. It can be seen from both images that
the Pt nano-particles were distributed uniformly on the
diamond surface. From Fig. 5A, after 1 h deposition, the
amount of Pt loading was large with an average diameter
Specific activities for H2O2 oxidation were calculated
from the current density of H2O2 at 0.6 V (exposed surface
Pt atoms area basis). The values were calculated as 1701,
(
D ) of 500 nm and the number of Pt particles deposited
1h
7
−2
−2
per unit real area (N ) was ca. 8.0 × 10 particles cm
703, 695, and 19 ␮A cm for Pt-modified BDDMF, Pt mi-
1h
(concerning the roughness factor of the diamond microfiber
croelectrode, Pt-modified diamond thin film and polycrys-
talline Pt film electrodes, respectively. These values indicate
that the catalytic activity of the Pt nano-particles was ca.
electrode [22] (ca. 2.34)). The number of exposed surface
14
−2
Pt atoms was estimated to be 5.82 × 10 Pt atoms cm
40 times higher than for bulk Pt metal and was in the same
range as the enhancement due to the effect of the microelec-
trode. For the Pt-modified BDDMF, by combining both ef-
fects, catalytic activity two orders of magnitude higher was
achieved.
Therefore, by depositing the optimum amount of elec-
trocatalytic particles on the microelectrodes, the sensitivity
for H2O2 oxidation (sensitivity for signal current) was en-
hanced due to the particle size effect, including the higher
specific activity of the nano-particle itself [26,27] and the
effect of the microdisc array [28]. Moreover, the low back-
ground current of the conductive diamond, which has previ-
ously been reported as a stable supporting material for metal
deposition [29], and the intrinsic properties of the micro-
electrodes, further enhance the sensitivity and overwhelm-
Fig. 4. Plots of S/B value at 0.6 V as a function of Pt deposition time,
calculated from the cyclic voltammogram for 1 mM H2O2 at Pt-BDDMF
electrode.

H. Olivia et al. / Electrochimica Acta 49 (2004) 2069–2076
2073
Fig. 5. SEM images of Pt-BDDMF electrodes for (A) 1 h and (B) 20 min Pt deposition time.
ingly outperform the platinum microelectrodes in terms of
the S/B ratio.
formed by fixing the potential at 0.7 V. The OPPy coat-
ing made it possible to suppress the anodic current for
AA oxidation and selectively detect H2O2 in a complex
medium.
3
.2. OPPy modification
Cyclic voltammograms obtained for 1 mM H2O2 and
1 mM AA with Pt-modified BDDMF before and after OPPy
modification are given in Fig. 7. The decrease in current
response for H2O2 (at 475 mV) after polymerization with
polypyrrole (ca. 20 times lower sensitivity for H2O2 oxida-
tion) was mainly due to the relatively thicker OPPy layer.
However, current suppression was more significant for ox-
idation of AA (ca. 1/700) than H2O2. The sensitivity for
H2O2 was still high enough to detect 100 ␮M H2O2. There-
fore, polymerization of the OPPy film at a fixed potential
We previously reported the polymerization of pyrrole on
a bare diamond surface by cycling between 0 and 1.1 V at a
−
1
scan rate of 500 mV s [22]. The film deposited using this
method was more compact and uniform than that obtained
at a fixed potential, resulting in an ultra-thin film. Similar
results were reported by Zhang et al. [27]. In this study
however, to avoid surface oxidation on the Pt nano-particles
(
oxidation of Pt to PtO2) leading to degradation of cat-
alytic activity, polymerization and overoxidation were per-

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H. Olivia et al. / Electrochimica Acta 49 (2004) 2069–2076
Fig. 8. Effect of pH to the sensitivity of the GOx/OPPy/Pt-BDDMF elec-
trodes. Experiments were performed in Britton Robinson buffer containing
0 mM glucose.
Fig. 6. Comparison of S/B values at 0.6 V calculated from cyclic voltam-
mogram for 1 mM H2O2 at Pt-BDD, Pt-microfiber electrodes, Pt-BDD,
and Pt macroelectrodes.
1
Therefore, it is expected that the optimization conditions ob-
tained for the bare Pt microelectrodes can be applied to the
Pt-deposited diamond microfiber electrodes.
(
0.7 V) offers a promising electrode modification method
for interference-free H2O2 detection.
Linear relations (data not shown) between current density
for 10 mM glucose and amount of GOx were obtained up-to
a GOx amount of 40 mg/2 ml immersion solution, indicat-
ing a catalytic limitation reaction. In comparison, for larger
amounts of GOx immobilization, the mass-transport limi-
tation of reactant to electrode surface controls the reaction
rate.
3
.3. Optimization of GOx amount
The amount of GOx immobilized was optimized for the
anodic current at 475 mV using polycrystalline Pt-microfiber
electrodes in a 10 mM glucose solution. Optimization of
deposition of GOx directly onto the Pt-deposited BDDMF
electrodes was not performed here because it was difficult
to obtain diamond films on tungsten fibers with the same
range of conductivity. Differences in conductivity result in
different amounts of Pt deposition, even when the same Pt
deposition conditions are used.
3.4. pH dependence
In order to examine the optimum pH value for the detec-
tion conditions, pH dependence studies were performed in
Britton Robinson buffer with 10 mM glucose. Plots of S/B
ratios calculated from cyclic voltammetric data at several
pHs are shown in Fig. 8. A maximum value was observed
with a physiological pH of 7.5, indicating the suitability of
the GOx/OPPy/Pt-modified BDDMF electrodes for in vivo
detection. At pHs lower than 7.5, the oxidation reaction of
H2O2 slightly shifted to the reactant side, leading to slower
Catalytic activity for H2O2 oxidation was mainly influ-
enced by the geometric structures of the electrocatalyst (both
the microelectrode shape and nano-particle array contribute
4
0-times to the enhancement), as described in the previ-
ous section. However, the increase in specific activity for
H2O2 oxidation of the Pt-modified BDDMF compared to the
Pt-microfiber electrode was relatively small (ca. 2.5 times).
Fig. 7. Cyclic voltammograms for 1 mM AA and 1 mM H2O2 in 0.1 M phosphate buffer (PBS) at (A) Pt-BDDMF electrode and (B) OPPy/Pt-BDDMF
−1
electrode. Sweep rate 10 mV s
.

H. Olivia et al. / Electrochimica Acta 49 (2004) 2069–2076
2075
Fig. 9. Amperometric responses for successive injections of glucose at optimized GOx/OPPy/Pt-BDDMF electrode and the linear calibration plot (inset).
Applied potential 475 mV vs. Ag/AgCl. Cell volume: 10 ml. Injection volume varied from 10 to 70 ␮l of 1 and 10 M of glucose.
reactions and less sensitivity. At higher pHs, the decreased
response for H2O2 might be due to denaturalization of GOx.
Similar results have been reported by Campuzano et al. [30].
3
.5. Glucose detection using GOx/OPPy/Pt-modified
BDDMF electrodes
Amperometric measurements of glucose were performed
at 475 mV versus SCE using optimized GOx/OPPy/Pt-modified
diamond microfiber electrodes (20 min Pt deposition and
4
0 mg/2 ml GOx immobilization). The results are shown
in Fig. 9, where linear amperometric responses in the con-
2
centration range of 1–70 mM, with an r of 0.997 were
Fig. 10. Amperometric responses for glucose (1 mM) and AA (100 ␮M)
at GOx/OPPy/Pt-BDDMF electrodes. Applied potential 475 mV vs.
Ag/AgCl. Cell volume: 10 ml. Each injection volume: 10 ␮l of 1 M glu-
cose or 10 ␮l of 100 ␮M of AA.
obtained. This detection range covers the normal (6.1 mM)
to abnormal levels for diabetic patients (more than 10 mM).
The effect of AA as the interfering compound was also in-
vestigated (Fig. 10). The results showed perfect suppression
of physiological concentrations of AA (ca. 100 ␮M).
Reproducible amperometric responses were obtained
with an R.S.D. of 3.7% for five injections of 100 ␮M glu-
cose. The response decreased to 75% of the initial response
after 2 weeks, but maintained a similar level during a
These results indicate that the GOx/OPPy/Pt-modified
BDDMF electrode is a promising electrode for continuous
monitoring of glucose and offers high sensitivity and high
stability without interference from AA.
3
-month period thereafter with no change in efficiency of
AA rejection. The stability of these electrodes excelled the
GOx/OPPy/Pt-microfiber electrodes for which the R.S.D.
value was 13.5% for five injections of 100 ␮M glucose and
the current responses decreased to 50% only after 1 month
and to 33% after 2 months.
4. Conclusions
In this present study, the superiority of BDDMF elec-
trodes as stable supporting materials for metal catalysts
was demonstrated. The sensitivity to detect enzymat-

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H. Olivia et al. / Electrochimica Acta 49 (2004) 2069–2076
ically produced H2O2 was significantly enhanced by
deposition of Pt nano-particles on a BDDMF surface.
GOx/OPPy/Pt-deposited BDDMF electrodes outperformed
GOx/OPPy/Pt-microfiber electrodes in terms of stability
and sensitivity due to three factors, namely, the high specific
activity of nano-particles, the non-planar diffusion profile of
the microelectrodes and the low background current which
is an intrinsic property of diamonds. The current responses
for glucose were widely linear between 1 and 70 mM.
The electrodes exhibited good stability during 3 months of
measurements and had perfect suppression of AA.
Glucose detections with the real blood sample using this
newly developed GOx/OPPy/Pt-deposited BDDMF elec-
trodes are very critical to be performed in the near future.
The superior performance of this electrode may bring this
electrode as a future glucose detector in the medical field,
since its detection range can cover abnormal glucose con-
centrations in diabetic patients. The electrode, due to its high
stability, can be expected to replace the single-use glucose
sensor, which is commonly available at present. Moreover,
the needle shape of electrodes is considered to be suitable
for in vivo monitoring, as they can minimize the amount of
sample required without decreasing the current response.
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