Development of an electrochemical lactate sensor for foetal monitoring during birth
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Foetal monitoring during birth is essential to determine foeta lwell-being throughout labour. The current method that complements foetal heart rate monitoring, foetal scalp blood sampling for pH determination, is laborious, prone to errors and invasive. Lactate has been identified as a potential alternative measurand for intrapartum foetal monitoring, due to the ability to distinguish between different types of acidosis. A literature review from the medical and technical perspective and a patent review were conducted to identify the current advancements in the field of lactate sensing with regards to foetal monitoring. It was concluded that a less invasive and a continuous monitoring device is required to fulfil the clinical needs for intrapartum foetal monitoring. Therefore, a novel biosensor, combining microneedle technology and electrochemical lactate sensing, was proposed and developed for this purpose. A fabrication process using the microneedle array was established using an electron beam evaporator. Commercial screen-printed electrodes were utilised for the development of an immobilisation protocol exploring covalent bonding and cross-linking. Electrochemical impedance spectroscopy, cyclic voltammetry and amperometry experiments were conducted to assess the success. A complete microneedle three-electrode prototype sensor was fabricated. The initial electrochemical analysis of commercially available, screen-printed electrodes concluded that platinum electrodes, in combination with covalent bonding, have the potential to provide the basis for further development towards a lactate sensor for foetal monitoring during birth. This work has identified developmental work required for the immobilisation process to be able to determine the compatibility with the microneedle array as an electrode surface.