Investigations into the design and development of novel screenprinted electrochemical biosensors for sugars

The aim of the studies described in this thesis was to develop a set of single shot biosensors, for low concentration measures (less the 1 mM) of glucose, sucrose and fructose. In addition, the development of a user friendly potentiostat instrumental system to display and save the data acquired, via the use of an android tablet. Chapter one describes an introduction and background to screen printed biosensors. Including the electrochemical techniques used and a basic explanation of screen printing. A brief discussion of the sugars, that will be measured in this thesis. Chapter two describes the development of a simple, low cost chronoamperometric assay, for the measurement of fructose, using a graphite-nanoparticle modified screen-printed electrode (SPCE-G-COOH). Cyclic voltammetry showed that the response of the SPCE-G-COOH enhanced the sensitivity and precision, towards the enzymatically generated ferrocyanide species, over a plain SPCE; therefore the former was employed in subsequent studies. Calibration studies were carried out using chronoamperometry and tested using a commercial fruit juice. Chapter three continues from chapter two, using studies to explore the conversion of the fructose bioassay into a fructose biosensor. More analysis of the interference of ascorbic acid (vitamin C) and a method of removing the interference signals via linear subtraction, using a secondary base electrode. Chapter four explains measuring glucose, using a unique mediator, and measuring the amperometric signal, in the reduction phase. The chapter describes the use of multiple enzymes and the optimisation of them. This section then demonstrates the modification of the glucose biosensor to a sucrose biosensor. This was achieved by the inclusion of an invertase enzyme. The studies of the glucose and sucrose biosensor were then compared against a commercially available system. Chapter five investigates a possible potentiostat system, linked to an android based tablet. The intention was to produce a simple and user-friendly system to measure and record the concentrations found. Chapter six comprises future work to be carried out and ideas. These suggestions are to improve the system allowing it to be more user-friendly and to remove some of the human errors that could be introduced into the system