Biomedical Engineering Reference
In-Depth Information
The titania-Nafion composite materials offer a convenient way for the preparation of
chemical sensors and biosensors. The use of the titania-Nafion composite has been shown
to be useful in improving the performances of the electrochemical sensors and biosensors.
For example, the electrochemical sensors based on titania-Nafion composite showed
extremely fast response time because the titania-Nafion composite materials have greater
pore size than pure Nafion film does, thus leading to faster diffusion of analyte into the
film [13]. Furthermore, the biosensors based on titania-Nafion composite films exhibited
substantial improvement in long-term stability because both Nafion and titania film were
very stable and biocompatible [14]. Therefore, the CNT-titania-Nafion biocomposite
materials combine the major advantages of CNT with those of bulk titania-Nafion com-
posite and thus open a new avenue for wide-range sensing application of CNT.
Another simple method for preparing effective CNT-based electrochemical biosensors
involves the use of CNT-Teflon composite films [15]. The bulk of the resulting CNT-teflon
electrodes play a role as a reservoir of the enzyme. The electrocatalytic properties of CNT
toward hydrogen peroxide and NADH are not impaired by their association with the
Teflon binder. Owing to the enhanced electron-transfer reactions of hydrogen peroxide
and NADH, effective low-potential amperometric biosensors for glucose and ethanol can
be fabricated with the incorporation of GOx or alcohol dehydrogenase/NAD
within the
CNT-Teflon composite matrix. The enhanced electrochemical activity of CNT-Teflon-
based biosensor was coupled with the minimization of electrode surface fouling com-
monly occurring in the NADH oxidation.
Gong et al. [16] reported on the sol-gel-derived ceramic-CNT nanocomposite elec-
trodes. The ceramic-CNT electrodes prepared in the above-mentioned manner exhibited
a tunable dimension ranging from conventional electrode to nanoelectrode ensembles,
depending upon the amount of the MWCNT dispersed in silica sol. A high content of
MWCNT resulted in the electrode in conventional dimension, while a low content pro-
duced the electrode in nanoelectrode dimension.
CNT-paste electrode was prepared by dispersing MWCNT within mineral oil [17-18].
Such composite materials combine the ability of CNTs to promote electron-transfer reac-
tions with the attractive advantages of paste electrode materials. In particular, the sub-
stantial decrease in the hydrogen peroxide reduction potential (400 mV) with an
incorporation of GOx into the composite material permits the development of a highly
selective and sensitive glucose biosensor without any mediator or antiinterference mem-
brane. Similarly, CNT-based screen-printed electrochemical sensors have been reported by
Wang and Musameh [19]. Screen-printing technology is well established for the mass pro-
duction of disposable electrochemical sensors. Most commonly used ink is carbon-based
conducting ink incorporating graphite particles, polymer binder, and other additives. In
the CNT-based screen-printed electrode, CNT was used instead of graphite for the con-
ducting inks. Such screen-printed CNT electrodes are mechanically stable and exhibit
higher electrochemical reactivity compared to conventional carbon-based screen-printed
electrode. Thus, the resulting CNT-based screen-printed electrodes combine the attractive
advantages of CNT and screen-printed electrodes.
13.3.1.2 Oxidase-Based Biosenors
Owing to the greatly enhanced electrocatalytic activity as well as dramatically decreased
overpotential of CNT-modified electrode toward the oxidation of hydrogen peroxide,
CNT-modified electrodes offer great promise for the development of selective and sensi-
tive electrochemical biosensors based on oxidase enzymes.
Wang group [8] reported on the glucose biosensor based on the CNT-Nafion-GOx-
composite on GC electrode. The accelerated electrocatalytic oxidation of hydrogen peroxide
