enzyme-based biosensors, with special emphasis on the electrochemical ones.
The manuscript will cover four representative classes of enzymes, namely
oxidases, dehydrogenases, reductases, and hydrolases.
Keywords
Enzymes Á Oxidoreductases Á Electrode Á Electrochemical Á Biosensors Á
Point-of-use tests
1 Introduction
Analytical chemistry plays a significant role in the control and monitoring of many
anthropological activities, as different as health care, food control, agriculture and
industrial processing, environmental, and security protection. Human progress
constantly challenges analytical chemistry, thus promoting the continuous development of new methodologies, probes, and detection instruments for the quick,
straightforward, and reliable examination of complex samples. Whenever possible,
the analytical solutions should be portable and simple-to-use, enabling the shift
from laboratory settings to on-site measurements. However, taking a sensitive and
selective method to the field is a major challenge yet. One of the most exciting
strategies relies on the integration of molecular recognition phenomena originated
from biological systems, which are typically highly selective, sensitive, and fast,
with a signal-transducing system that reflects the biorecognition event, and can be
easily miniaturized, automated, and connected with a data transmission system.
Such compact analytical devices are so-called biosensors. Briefly, a biosensor
incorporates a biological sensing component—the biorecognition element—intimately associated with a physicochemical transducer. The output is a digital
electronic signal that is proportional to the concentration of a target analyte or a
related group of analytes [1, 2].
The history of biosensing devices started with the groundbreaking work of
Leland C. Clark Jr., in 1962, describing an enzyme electrode for the first time.
Building on the previously invented “Clark electrode” where O 2 is reduced at a
platinum electrode, he demonstrated that the electrochemical detection of this
species could be used to monitor the catalytic activity of O 2 -consuming enzymes,
like oxidases, upon immobilization on the electrode surface. Because the decrease
in O 2 tension is stoichiometrically correlated with the consumption rate of the main
enzyme substrate, this could serve as the basis for a broad range of bioanalytical
applications. A glucose biosensor based on the entrapment of glucose oxidase was
the first successful example, which was followed by a myriad of other enzyme
electrochemical biosensors, either based on the assessment of the catalytic consumption of the co-substrate (O 2 ) or the formation of the also electroactive reaction
product (H 2 O 2 ), or even an artificial redox mediator. The first commercial glucose
304
T. Monteiro et al.
The manuscript will cover four representative classes of enzymes, namely
oxidases, dehydrogenases, reductases, and hydrolases.
Keywords
Enzymes Á Oxidoreductases Á Electrode Á Electrochemical Á Biosensors Á
Point-of-use tests
1 Introduction
Analytical chemistry plays a significant role in the control and monitoring of many
anthropological activities, as different as health care, food control, agriculture and
industrial processing, environmental, and security protection. Human progress
constantly challenges analytical chemistry, thus promoting the continuous development of new methodologies, probes, and detection instruments for the quick,
straightforward, and reliable examination of complex samples. Whenever possible,
the analytical solutions should be portable and simple-to-use, enabling the shift
from laboratory settings to on-site measurements. However, taking a sensitive and
selective method to the field is a major challenge yet. One of the most exciting
strategies relies on the integration of molecular recognition phenomena originated
from biological systems, which are typically highly selective, sensitive, and fast,
with a signal-transducing system that reflects the biorecognition event, and can be
easily miniaturized, automated, and connected with a data transmission system.
Such compact analytical devices are so-called biosensors. Briefly, a biosensor
incorporates a biological sensing component—the biorecognition element—intimately associated with a physicochemical transducer. The output is a digital
electronic signal that is proportional to the concentration of a target analyte or a
related group of analytes [1, 2].
The history of biosensing devices started with the groundbreaking work of
Leland C. Clark Jr., in 1962, describing an enzyme electrode for the first time.
Building on the previously invented “Clark electrode” where O 2 is reduced at a
platinum electrode, he demonstrated that the electrochemical detection of this
species could be used to monitor the catalytic activity of O 2 -consuming enzymes,
like oxidases, upon immobilization on the electrode surface. Because the decrease
in O 2 tension is stoichiometrically correlated with the consumption rate of the main
enzyme substrate, this could serve as the basis for a broad range of bioanalytical
applications. A glucose biosensor based on the entrapment of glucose oxidase was
the first successful example, which was followed by a myriad of other enzyme
electrochemical biosensors, either based on the assessment of the catalytic consumption of the co-substrate (O 2 ) or the formation of the also electroactive reaction
product (H 2 O 2 ), or even an artificial redox mediator. The first commercial glucose
304
T. Monteiro et al.