Nanowire biosensor as cost-effective testing platform for biomedical applications

Devices based on nanostructures, such as nanogaps and nanowires, are widely employed in bio-sensing, for example building a sensing nanowire structure on a nanogap between two electrodes. The main difficulty in the fabrication process of these structures is due to the fact that the nanogap between the electrode is created starting from a continuous structure and then using electromigration, but this process is random and so non-controllable. Moreover the positioning of the nanowire right in the middle of the gap is quite challenging. In this work, starting from the fabrication of the devices (based on a previous work and slightly modified), different tests on the devices are performed, starting from measuring the resistance of the nanowire itself, to a detection of human fibrinogen. This particular molecules, are widely studied in medical sciences because of their central role in human immune response, helping to stop excessive bleeding when an injury happens. The best way to do fibrinogen detection is through an ELISA kit, but these kits are quite big and so less sensitive than a nanostructure-based biosensor. A better approach, that is followed in this work, is to employ a nanostructure, such as a nanowire, in order to obtain a better sensitivity and a better specificity, with a cost-effective solution. In this approach the biological readouts are achieved by relative measurement of the fibrinogen binding on the surface of the functionalised nanowire surface. Readouts in this instance are achieved as I/V curves within the linear resistance response of the sensor. This enables to achieve sensitivity but also additional specificity when the functionalisation is successful. The characterisation and battery of results achieved in this thesis are showing promising evidence for biomedical applications in the haematology rapid detection diagnostic area.