Application of nano-alumina electrodes in electrochemical sensing for monitoring exercise-induced lactate

Abstract

This study reports the development of a novel potentiometric biosensor for non-invasive analysis of lactate in human sweat, employing a carbon paste electrode modified with nano-Al₂O₃ and lactate oxidase (LOx). Nano-Al₂O₃ was synthesized via a sol–gel process, yielding uniformly dispersed, porous particles with diameters of 80–90 nm and an average crystallite size of approximately 55 nm, which enhanced the electrode’s catalytic efficiency and electron transfer capabilities. The carbon paste electrode was prepared by incorporating 10 wt% of nano-Al₂O₃ into a composite of graphite and carbon black, followed by immobilization of LOx from a 2.5 mg/mL solution to ensure stable enzyme activity. Electrochemical evaluation revealed that the modification reduced the charge transfer resistance from 410 Ω for the bare electrode to 324 Ω, while the subsequent enzyme coating increased resistance moderately to 534 Ω without compromising performance. Calibration studies using lactate concentrations ranging from 0.1 mM to 50 mM yielded a linear response with a sensitivity of 150 mV per decade and a detection limit of 0.08 mM. The biosensor reached stable readings within 45–60 s and exhibited high reproducibility with a relative standard deviation below 4 % over repeated tests. Ex vivo sweat analysis during controlled exercise demonstrated a recovery rate of 96 % and a strong correlation (R² = 0.97) with standard HPLC measurements, verifying the biosensor’s real-world applicability. These results indicate that nano-scale modification via nano-Al₂O₃ integration significantly enhances biosensor performance, offering a promising platform for continuous metabolic monitoring in sports and clinical diagnostics.