Self-Powered Electrochemical Lactate Biosensing

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), respectively, to facilitate the oxidation and reduction of lactic acid and molecular oxygen. 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 1-25 mM. An open circuit voltage of 395.3 mV and a short circuit current density of 418.8 mu A/cm(2) 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 bursts of 1.2-1.8 V via the capacitor. By observing the burst frequency of a 10 pF capacitor, the exact concentration of lactic acid was deduced. As a self-powered lactate sensor, a linear dynamic range of 1-100 mM lactic acid was observed under physiologic conditions (37 degrees C, pH 7.4) and the sensor exhibited an excellent sensitivity of 125.88 Hz/mM-cm(2). This electrochemical lactate biosensor has the potential to be used for the real-time monitoring of lactic acid level in biological fluids.