AbstractThe phosphorylation of proteins, catalysed by protein kinases, play an important role in nearly every aspect of cell life. The abnormal phosphorylation of proteins is responsible for the onset of several diseases and disorders including various types of cancers, diabetes, Alzheimer's disease, etc. Therefore, the discovery of protein kinase inhibitors is a major focus of the pharmaceutical companies. Drug discovery today is dominated by number a of processes that require expensive chemicals, fluorescent tags and radio-labelling and can often be time consuming and laborious. Through this research, a new process for the screening of protein kinase inhibitors has been explored. In order to improve the cost effectiveness and efficiency of the process, biosensors have been developed using printed circuit board (PCB) technology and made compatible with commercially available complementary metal oxide semiconductors (CMOS). Designing a REFET structure for biosensing where the reference electrode can be eliminated was the final aim.
In this thesis, the techniques which are already in use are reviewed in order to understand their drawbacks and to help improve our design. A sensor array that can fit under the industrially used 96 well microtitre plate has been designed such that the existing techniques of liquid handling for drug discovery can be used.
In the first technique an electrolyte-insulator-semiconductor structure is interfaced with a PCB for sensing pH changes associated with phosphorylation, through capacitance versus voltage measurements. Next, organic thin film transistors with gold extended gates have been used to detect charge changes during a phosphorylation reaction. Thin films of evaporated tin oxide and tantalum oxide on a PCB have also been tested as pH sensitive membranes for this reaction. The thin films have been used as extended gates for commercial CMOS circuits and the shift in their drain current versus gate voltage characteristics have been measured.
The REFET structure has been finally designed with tin oxide as the sensing layer. The reference layer has been designed using a thin film made of SU-8 photoresist as a pH insensitive layer. The two thin films have been used as extended gates to a commercially available matched pair CMOS integrated circuit and a differential measurement in their drain current for a fixed gate voltage is conducted for the phosphorylation reaction. Finally, array of REFET structures are multiplexed for the possibility of high throughput screening. The final device provides an excellent starting point for fabricating sensor arrays compatible with the widely accepted well plate structure and associated liquid handling systems.
|Date of Award||2 Oct 2019|
|Supervisor||Mirella Di Lorenzo (Supervisor) & Pedro Estrela (Supervisor)|