Nanotechnology-Enabled Sensors

400 Chapter 7: Organic Nanotechnology Enabled Sensors
ICPs also have numerous applications in biosensing. These polymers are
attractive materials to use in biosensors due to the considerable flexibility
that exists in their chemical structures and their redox characteristics. Such
characteristics of conductive polymers are very useful for the development
of enzyme-based biosensors (enzyme-based sensors will be discussed in
the coming sections) where rapid electron transfer at the electrode surface
is required. In fact, ICPs such as polyaniline, polypyrrole, polyindole and
polythiophene have already been widely used in enzyme-based biosensors.
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The mild conditions used for the polymerization of such conductive
polymers are ideal for the incorporation of enzymes, antibodies or even
whole living cells. Polymers such as polypyrrole, 73 polyaniline 74 and polyphenylenediamine
75 can be used for the physical entrapment of enzymes
during the electrodeposition of the polymers.
ICPs in nano-form also enhance the biosensing properties of existing
transducers. For instance, Kim et al 76 reported producing a conductometric
immunosensor with polyaniline-bound gold colloids (Fig. 7.27). They
introduced polyaniline as a conductive agent on the gold surface after
immobilizing an antibody specific to human albumin on transducer. This
polyaniline-bound gold system can amplify the conductometric signal several
times compared with the plain gold system.
Fig. 7.27 The concept of enhanced electron transfer with a conducting polymer
adsorbed onto the surface of gold colloids for biosensing applications. Reprinted
with permission from the Elsevier publications. 76