glycerol in the presence of the redox cofactor NADH. Its electrochemical response
can then be assessed through the use of a redox mediator [297, 298].
Hydrolases can also be used as part of target probes in affinity biosensors. When
the probe binds to its specific target (the analyte in question), the hydrolytic reaction
generates an electroactive product that is detected at the electrode’s surface. The
alkaline phosphatase has been applied in the construction of such devices for the
detection of tumor and influenza virus biomarkers [299, 300]. The detection principle is based on the hydrolysis of amino- or nitrophenyl phosphates, which results
in an oxidizable product that is detected at the electrode.
6 Summary and Outlook
From the early work of Clark and Lyons with glucose oxidase, biosensing with
selective enzymes has become an extensive research field. Attractive features of
these biocatalysts, such as high selectivity, sensitivity, and fast reaction rates, have
maintained them as highly sought after bioreceptors for biosensor construction. The
combination with electrochemical transducers has been widely explored due to
added advantages, such as simplicity, relative low costs, high sensitivity, and the
potential to create miniaturized, portable devices.
Glucose detection, which is mostly based on glucose oxidases and dehydrogenases, continues to dominate the biosensor’s market and remains one of the largest
areas in biosensor research. Nonetheless, the demand for improved analytical tools
for a variety of target substrates increases continuously and stimulates the
exploitation of a plethora of new enzymes. Accordingly, electrochemical
enzyme-based biosensors have been proposed for the detection of several important
analytes, such as cholesterol, neurotransmitters, or phenolic compounds using a
variety of oxidase enzymes; nitrate, nitrite, or nitric oxide with selective reductases;
and organophosphate compounds, urea or influenza virus biomarkers by employing
different hydrolases.
The enzyme biosensor field shows no signs of slowing down. Still, a number of
issues need to be addressed before new bioelectrocatalytic systems can make an
impact on real-life applications. Further optimization of biosensor architectures is
required to ensure efficient enzyme integration with electrode interfaces, facilitating
ET, and improving device stability and reproducibility. Significant progress has
been made through the years and will undoubtedly continue, owing to advances in
material sciences, polymer chemistry, and electronics technology, as well as, the
increased understanding of enzyme properties and the parameters that control their
activity on electrode surfaces. Through combined research efforts, the advantages of
these unique biocatalysts have and are expected to carry on supplying solutions to
analytical challenges ranging from biomedical analysis to environmental pollution,
food safety, or industrial bioprocess monitoring.
344
T. Monteiro et al.
can then be assessed through the use of a redox mediator [297, 298].
Hydrolases can also be used as part of target probes in affinity biosensors. When
the probe binds to its specific target (the analyte in question), the hydrolytic reaction
generates an electroactive product that is detected at the electrode’s surface. The
alkaline phosphatase has been applied in the construction of such devices for the
detection of tumor and influenza virus biomarkers [299, 300]. The detection principle is based on the hydrolysis of amino- or nitrophenyl phosphates, which results
in an oxidizable product that is detected at the electrode.
6 Summary and Outlook
From the early work of Clark and Lyons with glucose oxidase, biosensing with
selective enzymes has become an extensive research field. Attractive features of
these biocatalysts, such as high selectivity, sensitivity, and fast reaction rates, have
maintained them as highly sought after bioreceptors for biosensor construction. The
combination with electrochemical transducers has been widely explored due to
added advantages, such as simplicity, relative low costs, high sensitivity, and the
potential to create miniaturized, portable devices.
Glucose detection, which is mostly based on glucose oxidases and dehydrogenases, continues to dominate the biosensor’s market and remains one of the largest
areas in biosensor research. Nonetheless, the demand for improved analytical tools
for a variety of target substrates increases continuously and stimulates the
exploitation of a plethora of new enzymes. Accordingly, electrochemical
enzyme-based biosensors have been proposed for the detection of several important
analytes, such as cholesterol, neurotransmitters, or phenolic compounds using a
variety of oxidase enzymes; nitrate, nitrite, or nitric oxide with selective reductases;
and organophosphate compounds, urea or influenza virus biomarkers by employing
different hydrolases.
The enzyme biosensor field shows no signs of slowing down. Still, a number of
issues need to be addressed before new bioelectrocatalytic systems can make an
impact on real-life applications. Further optimization of biosensor architectures is
required to ensure efficient enzyme integration with electrode interfaces, facilitating
ET, and improving device stability and reproducibility. Significant progress has
been made through the years and will undoubtedly continue, owing to advances in
material sciences, polymer chemistry, and electronics technology, as well as, the
increased understanding of enzyme properties and the parameters that control their
activity on electrode surfaces. Through combined research efforts, the advantages of
these unique biocatalysts have and are expected to carry on supplying solutions to
analytical challenges ranging from biomedical analysis to environmental pollution,
food safety, or industrial bioprocess monitoring.
344
T. Monteiro et al.