The specificity of biosensors is achieved by the use of biological probes with affinity to the targets to be detected. The electrochemical transducer converts the biological recognition process into an electrical signal. The resulting electrical signal is the response of the recognition from the biolayer. Potentiometric, amperometric and voltammetric detection are the fundamental electrochemical measurement techniques. In this thesis, direct open circuit potentiometry (OCP) is studied with several types of electrochemical systems. The biological interaction between the probes and the targets are characterised by measuring the variations of the true open circuit potential (OCP) that occurs at the surface of the working electrode when the charge density and the distribution of the immobilised biolayer change upon interactions with the target biomolecules. OCP is a detection technique which measures the recognition electrical signal in real time.With the true OCP measurement system developed in-house, a number of electrochemical systems were studied by looking at the interaction with different biomolecules, to show that a true OCP measurement system could be achieved for biosensor development. The electrochemical systems that have been investigated include DNA – DNA detection with a novel cobalt complex for signal enhancement, PNA – DNA detection with gold nanoparticles for signal enhancement, and protein phosphorylation (for drug discovery applications) with gold nanoparticles for signal enhancement. A comparison with promising biosensing techniques such as electrochemical impedance spectroscopy (EIS) and other techniques is performed to demonstrate the benefits of OCP as a biosensing technique. An easily expandable multichannel OCP biosensor array instrumentation system was developed. The whole instrumentation is built and assembled with a custom designed electronic system, a microfluidic system and its applicability demonstrated for a range of electrochemical systems. Through an investigation of the instrumentation amplifier circuit and the multiplexing technique, and the analysis of experimental data, an optimisation for the OCP measurement system is achieved. This thesis tackles a gap in the literature in terms of studies of OCP as a biosensing technique, providing a number of case studies that can contribute towards the development of potential new low-cost biosensors.
|Date of Award||20 Jun 2018|
|Supervisor||Pedro Estrela (Supervisor)|