the Pt NPs was found to be highly beneficial for the electron transfer, as indicated
by the unusually high turnover rate of electrons of 2,580 e
À s
À1 that was measured.
In addition to Pt, several other metals have been studied as modifiers for
bioelectrodes, as, for example, Ag [104], Co [105], and Pd [106], but perhaps one
of the most interesting metals to study further is Fe, given its low toxicity, low cost,
and high availability. The group of Poo-arporn recently described a glucose/O 2 EBC
that was manufactured from a reduced graphene oxide electrode material, which
was only doped with superparamagnetic Fe 3 O 4 NPs [107]. Although the measured
maximum power density was modest (73.7 μW cm
À2 at 5 mM glucose), the open
circuit voltage of +0.63 V was more impressive and demonstrates that Fe-based
electrode materials could be used in the future to fabricate EBCs that are viable for
real-life applications.
3.2 Outlook on the Future Applications of Enzymatic Biofuel
Cells
Future applications of bioelectrodes and complete EBC assemblies in the medicinal
field are predicted to increase. However, in order for these devices to become widely
applied, their long-term performance need to be further improved if they are to compete
with state-of-the-art batteries. Encouragingly, this research field has progressed at an
impressive pace during the past decade, much thanks to innovations related to the
engineering of new nanomaterials and clever solutions for interfacing enzymes with
nanometallic species. Thus, it will most likely not take long until we can see the first
examples of implantable medical devices that are powered by EBCs. Such devices
could, for example, be self-powered biosensors that over a period of days detect certain
analytes in the patient’s blood and where the measured analyte at the same time acts as a
fuel for the EBC. As has been showcased herein, biosensors have already been
developed for a wide range of analytes such as cholesterol, glucose, lactate, urea, and
vitamin C, and all of these are relevant to a variety of medical conditions and diseases.
However, in recent years several ingenious bioanalytical devices have been reported
in which hybrid glucose/O 2 EBCs have been connected to more elaborate sensing
platforms to enable the detection of a much wider range of species.
For example, the group of Li has reported on a self-powered and ultrasensitive
aptasensing platform for detection of antibiotic residues in the nM range (Fig. 4) [108].
In this system, the bioanode of the EBC is coated with SiO 2 @Au NP-DNA conjugates
that interact with the electrode surface via complementary and pre-attached aptamers.
The function of these DNA conjugates is to block the access of glucose to the bioanode
surface in the absence of the analyte and thus restrict the power output of the EBC.
However, once the analyte is present in the surrounding solution, the analyte will
interact with the aptamers and trigger the release of the DNA conjugates, which will
expose the electrode surface to the glucose, and as a result, the power output of the EBC
will increase. The authors showcased the practical applicability of this aptasensing
260
O. Verho and J.-E. Bäckvall
by the unusually high turnover rate of electrons of 2,580 e
À s
À1 that was measured.
In addition to Pt, several other metals have been studied as modifiers for
bioelectrodes, as, for example, Ag [104], Co [105], and Pd [106], but perhaps one
of the most interesting metals to study further is Fe, given its low toxicity, low cost,
and high availability. The group of Poo-arporn recently described a glucose/O 2 EBC
that was manufactured from a reduced graphene oxide electrode material, which
was only doped with superparamagnetic Fe 3 O 4 NPs [107]. Although the measured
maximum power density was modest (73.7 μW cm
À2 at 5 mM glucose), the open
circuit voltage of +0.63 V was more impressive and demonstrates that Fe-based
electrode materials could be used in the future to fabricate EBCs that are viable for
real-life applications.
3.2 Outlook on the Future Applications of Enzymatic Biofuel
Cells
Future applications of bioelectrodes and complete EBC assemblies in the medicinal
field are predicted to increase. However, in order for these devices to become widely
applied, their long-term performance need to be further improved if they are to compete
with state-of-the-art batteries. Encouragingly, this research field has progressed at an
impressive pace during the past decade, much thanks to innovations related to the
engineering of new nanomaterials and clever solutions for interfacing enzymes with
nanometallic species. Thus, it will most likely not take long until we can see the first
examples of implantable medical devices that are powered by EBCs. Such devices
could, for example, be self-powered biosensors that over a period of days detect certain
analytes in the patient’s blood and where the measured analyte at the same time acts as a
fuel for the EBC. As has been showcased herein, biosensors have already been
developed for a wide range of analytes such as cholesterol, glucose, lactate, urea, and
vitamin C, and all of these are relevant to a variety of medical conditions and diseases.
However, in recent years several ingenious bioanalytical devices have been reported
in which hybrid glucose/O 2 EBCs have been connected to more elaborate sensing
platforms to enable the detection of a much wider range of species.
For example, the group of Li has reported on a self-powered and ultrasensitive
aptasensing platform for detection of antibiotic residues in the nM range (Fig. 4) [108].
In this system, the bioanode of the EBC is coated with SiO 2 @Au NP-DNA conjugates
that interact with the electrode surface via complementary and pre-attached aptamers.
The function of these DNA conjugates is to block the access of glucose to the bioanode
surface in the absence of the analyte and thus restrict the power output of the EBC.
However, once the analyte is present in the surrounding solution, the analyte will
interact with the aptamers and trigger the release of the DNA conjugates, which will
expose the electrode surface to the glucose, and as a result, the power output of the EBC
will increase. The authors showcased the practical applicability of this aptasensing
260
O. Verho and J.-E. Bäckvall