| Lactic acid is a key biomarker of stress that increases during organ procurement process and is the main source of metabolically produced acid responsible for tissue acidosis. When an individual experiences an extremity limb loss, the flow of nutrients and oxygen to that limb ceases, which initiates the deterioration of the limb's tissue. This process is described as ischemia, which can be identified by the coupled and accelerated production of lactic acid and oxidation of glucose due to elevated glycolysis in the oxygen-deprived tissue. Thus, lactic acid concentration levels can serve as excellent biomarkers for monitoring tissue and organ health. This work presents the development and characterization of a self-powered electrochemical lactate biosensor for real-time monitoring of lactic acid. The bioanode and biocathode were modified with D-Lactate dehydrogenase (D-LDH) and Bilirubin oxidase (BOD) to facilitate the oxidation of lactic acid and the reduction of molecular oxygen, respectively. The bioelectrodes were arranged in a parallel configuration to construct the biofuel cell. This biofuel cell's current-voltage characteristic was analyzed in the presence of various lactic acid concentrations over a range of 1 mM to 25 mM of lactic acid. An open circuit voltage of 395.3 mV and a short circuit current density of 418.8 microA/cm2 were obtained when operating in 25 mM lactic acid. Additionally, a 10 pF capacitor was integrated via a charge pump circuit to the biofuel cell to realize the self-powered lactate biosensor with a footprint of 1.4 cm x 2 cm. The charge pump enabled the boosting of the biofuel cell voltage in burst of 1.2 V to 1.8 V via the capacitor. By observing the burst frequency of 10 pF capacitor, the exact concentration of lactic acid was deduced. As a self-powered lactate sensor, a linear dynamic range of 1 mM to 100 mM lactic acid was observed under physiologic conditions (37 °C, pH 7.4) and the sensor exhibited an excellent sensitivity of 125.88 Hz/mM-cm2. This electrochemical lactate biosensor has the potential to be used for real-time monitoring of lactic acid level in biological fluids. |
