Advances in electronic detection based on nanowires (NWs) and nanotubes (NTs) has revolutionized our ability to provide label-free and real-time, yet sensitive and selective detection of a wide range of chemical and biological species using the NW or NT as the gate of a field effect transistor (FET). The selectivity of the nanosensors can be further enhanced by modification with specific bioreceptors.

Conducting polymers such as polypyrrole (Ppy) because of their electronic conductivity, environmental stability, easy and controlled processing by electrochemical polymerization and biocompatibility have emerged as promising materials in the development of biosensors. Here we report a cost-effective fabrication of a single Ppy nanowire based conductometric biosensor for label-free, sensitive, selective and rapid detection of proteins.

Two hundred nanometer diameter Ppy nanowires were fabricated using well established template method using alumina template and suspended in water after dissolution of template. Using electrophoretic alignment, single nanowire connections were obtained between 3 μm gap pair of prefabricated gold electrodes. Nanowire on the electrodes was subsequently secured on the electrodes by maskless gold electrodeposition. This also ensured good electrical contact between nanowire and the contact electrodes.

To demonstrate the utility of these devices as a biosensor, covalent surface functionalization of these nanowires was studied and an optimum strategy of functionalization was adopted. Ppy nanowires were functionalized with antibodies against carcinoembryonic antigen (CEA) and label-free detection and quantification of CEA achieved.