Exploiting Biological Toxicity Mechanisms for Enhanced Arsenite Detection Using α-Lipoic Acid-Modified CuO Nanoparticles

Arsenic contamination remains a critical global water quality challenge, with inorganic arsenite [As(III)] representing the most acutely toxic and mobile form. The strong affinity of As(III) for sulfhydryl groups in biological systems motivates the development of thiol-based recognition strategies for selective sensing. Here, a biomimetic electrochemical platform is presented in which alpha-lipoic-acid-functionalized CuO nanoparticles (αLA-CuO NPs) are immobilized on a disposable graphite pencil electrode (GPE). Electrochemical reduction of surface-bound αLA generates thiol functionalities that enhance As(III) complexation and interfacial charge transfer at the CuO nanostructured surface. Structural and electrochemical characterizations verify successful functionalization and improved electron-transfer kinetics relative to unmodified electrodes. Differential pulse voltammetry enables sensitive detection of As(III) from 1–500 μM with a limit of detection of 65.5 nM (4.9 μg L–1), which is below the 10 μg L–1 guideline for drinking water established by the World Health Organization. The sensor exhibits excellent selectivity against common coexisting ions and achieves recoveries of 98.35 ± 2.56% in spiked canal water, demonstrating minimal matrix interference. This work introduces a new low-cost αLA-CuO/GPE architecture in which biomimetic thiol chemistry is synergistically integrated with a nanostructured, disposable electrode format, offering practical potential for on-site monitoring of arsenic in contaminated water sources.