Date of Award
Master of Science (MS)
Electrical & Computer Engineering
Lactic acid is a vital indicator for shock, trauma, stress, and exercise intolerance. It is a key biomarker for increases in stress levels and is the primary metabolically produced acid responsible for tissue acidosis that can lead to muscle fatigue and weakness. During intensive exercise, the muscles go through anerobic metabolism to produce energy. This leads to decreases in the blood flow of nutrients and oxygen to the muscles and increases in lactate production, which in turn cause lactic acidosis. Currently, changes in blood lactate concentrations are monitored by sensors that can be invasive via blood or wearable based sensors that use the enzyme lactate oxidase. Lactate oxidase produces hydrogen peroxide, which is a toxic byproduct and can foul the surface of the sensor. Here, we present the development of a noninvasive wearable electrochemical lactate biosensor for the detection of lactic acid. The bioelectrode was designed with buckypaper (BP), which is composed of a dense network of multi-walled carbon nanotubes. This material was chosen due to its low cost, high conductivity, flexibility, and high active surface area. D-Lactate dehydrogenase (D-LDH) was immobilized on the surface of the BP to facilitate the oxidation of lactic acid. The biosensor was then integrated into a polydimethylsiloxane (PDMS) flexible substrate platform. PDMS was chosen because of its lightweight, flexible, biocompatibility, and conformal properties. The sensor is designed to be placed on skin in order to measure the concentration of lactate in sweat. The concentration of lactate in sweat has been shown to be a good biomarker for evaluating the severity of peripheral occlusive arterial diseases and damage in soft tissue. The lactate biosensor developed in this work exhibited a dynamic linear range of 5 mM to 45 mM lactic acid with a good sensitivity of 1.388μA/mMcm2. It can measure higher than the average lactate concentration in sweat during exercise, which is 31mM. This electrochemical biosensor has the potential to be used for the real-time detection of lactic acid concentration in sweat, suggesting promising applications in clinical, biological and sports medicine fields.
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"Flexible Electrochemical Lactate Sensor"
(2020). Master of Science (MS), Thesis, Electrical & Computer Engineering, Old Dominion University, DOI: 10.25777/e73w-zn15