A novel electrochemical platform based on screen printed carbon electrodes (SPCEs) for molecular diagnostics

Identifier:  TDX:3083

Handle: https://hdl.handle.net/20.500.11797/TDX3083

Authors:  Ahmed, Nihad Kamal Ibrahim

Abstract:
The objective is to develop an electrochemical platform based on screen printed microsystems that enable low cost, point of use molecular diagnostics. This thesis focuses on methods to increase the reliability and reproducibility of screen printed electrode-based molecular assays. As proof of concept Karlodinium armiger, a toxic microalgae used as target. Recombinase Polymerase Amplification (RPA), an isothermal amplification method, was chosen because it can be easily incorporated in portable, point-of-use devices. Non-specific interactions with the porous and irregular surface of the SPCEs affect the reliability of the results. We demonstrate two methods can solve these problems: the first approach electro-grafted carboxylated diazonium was linked covalently to the aminated DNA probes (recognition layer) on the SPCE surface. DNA hybridization and detection were achieved in both solid and liquid phase RPA achieving detection limits (LODs) of 0.1 fM and 0.3 fM respectively. This approach requires wet chemistry and electrochemical activation of the electrodes during manufacturing, complicating production and increasing its cost. Surface modification by drop casting is more appropriate for large scale production. Basically, the surface of SPCEs was modified with poly (L-Lysine) polymer crosslinked with polyethylene glycol diglycidyl ether (PEGDE) that attached the aminated DNA probes. Polyethylene glycol (PEG) used to block the non-specific adsorption of horseradish (HRP) labels that were used for detection