Study and Characterization of a Microfluidic enhanced Lactate Sensor with Iron Oxide (III) Nanoparticles

Lactate plays a key role in exercise physiology and metabolic studies as it is produced by the body as part of normal metabolic processes and has recently gained importance in relation to human sweat. Previous research has focused on blood lactate as an indicator of exercise intensity, but recent studies are moving towards the analysis of sweat lactate, providing a broader understanding of lactate dynamics. The aim of this thesis is to investigate the development and performance evaluation of a sweat lactate biosensor. Sweat lactate concentrations is investigated through a series of experiments and analyses under different conditions: time, temperature, contamination, nanoparticle involvement. The theoretical basis for understanding the functionality of the biosensor is provided, covering lactate and sweat physiology, useful materials for immobilisation of nanoparticles and enzymes. The use of mill-scale nanoparticles, wearable sensing technologies and electrochemical sensing techniques is explored, with an overview of dynamic and static diffusion mechanisms. A notable aspect is the use of a microfluidic cell with a flow rate based sensing method that takes into account the natural flow of sweat in human skin, as opposed to the traditional approach of static sweat sampling. This offers the possibility of identifying and monitoring lactate concentrations in real time as a function of physiological performance. The methodology employed is described in detail, including beaker and flow cell setups, the origin and synthesis of magnetite nanoparticles, flow cell design and fabrication procedures, nanoparticle and enzyme immobilisation methods, and sample preparation protocols. The focus shifts to the presentation and analysis of experimental results, highlighting the effects of nanoparticles on biosensor performance, the key differences between beaker and flow cell configurations, the influence of time, temperature and interferences on biosensor functionality, and the comparison of custom biosensors with commercial alternatives. Lastly, the thesis describes future prospects and concludes with implications for continued refinement and innovation in the advancement of sweat lactate biosensor technology. The results of this research could change the approach to lactate monitoring, with potential applications ranging from sports science to the prevention of heat-related diseases, contributing to the wider field of wearable and point-of-care diagnostics.