Advances in biosensors: principle, architecture and applications

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Fig. 4.0: Methods of biosensing with various transducer mechanisms: (a) Optical; (b)
Electrochemical; (c) Calorimetric - thermal; (d) Piezoelectric- mass sensitive.
Electrochemical biosensor
Electrochemical sensor in which an electrode is used as the transduction element, represent an
important subclass of sensor. According to IUPAC recommendation 1999, an electrochemical
biosensor is self-contained integrated device, which is capable of providing specific
quantitative or semi-quantitative analytical information using a biological recognition element
(biochemical receptor) which is retained in direct spatial contact with an electrochemical
transduction element (Thevenot et al. 1999, 2001). Electrochemical biosensors measure the
current produced from oxidation and reduction reactions. This current produced can be
correlated to either the concentration of the electroactive species present or its rate of
production/consumption. The resulting electrical signal is related to the recognition process
by target and analyte, and is proportional to the analyte concentration. A review by Wang et
al. (2008) has revealed that electrochemical immunosensors are gradually increasing in
popularity in clinical analysis and this is partly due to improved sensor design. Similarly,
Maria et al. (2008) revealed that the electrochemical immunosensor is a promising alternative
compared to existing laboratory method. Wang (2006) has reported the use of
electrochemical-based device for point-of-care cancer diagnostics which has brought the
electrochemical biosensor to new level in clinical diagnostics. Subsequently, all this report
has reveal the electrochemical biosensor has advantages such as fast, simple, low cost, high
sensitivity, and relatively simple instrumentation (Grieshaber et al. 2008, Mono et al. 2012).
Depending upon the nature of electrochemical changes detection during a biorecognition
event, electrochemical biosensors fall into one of four categories: amperometric,
potentiometric, impedance and conductometric.
Amperometric
Amperometric sensor are based on the measurement of current as a function of time resulting
from the oxidation and reduction of an electroactive species in a biochemical reaction that
mainly depends on the concentration of an analyte with a fixed potential. There are three type
of electrode that usually employed in a amperometric sensor; The working electrode which
usually made of gold (Au), carbon (c), platinum (Pt), A reference electrode usually silver or
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