Conducting polymers have been widely used in the development
and fabrication of biosensors for several applications due to
their extremely useful physical, optical and electrical properties
[1–4]. Polyaniline (PAni) is one of the most investigated conducting
polymers [5,6]. It provides extraordinary stability, simplicity of
synthesis and excellent electrochemical properties. PAni based
amperometric and piezoelectric immunosensors have been
reported for several applications [7–9]. Nanostructured PAni has
been shown to provide greater sensitivity and faster response time
compared to bulk counterpart due to higher effective surface area
and shorter penetration depth for the analytes.
Desired immobilization of biomolecules on PAni substrates is
achieved through molecular entrapment, protein A adsorption,
electrostatic binding by oxidation and covalent bonding to the
copolymerized PAni [10–15]. Enzymes have also been grafted onto
the PAni surface with the help of cross-linkers [16–19]. At times, for
immobilizing the biomolecules, PAni is first grafted with suitable
functional groups, e.g.–COOH using acrylic acid [20,21]. One of our
recent works demonstrated the immobilization of protein
molecules on PAni through avidin-biotin interaction [22].