Photoelectrochemical determination of nitrite as a biomarker of exercise-induced nitric oxide metabolism in athletes using a CdS/polyaniline sensor

The precise detection of nitrite as a stable, end product and downstream metabolite of NO is critical for understanding exercise-induced physiological adaptation in athletes. However, typical electrochemical techniques usually have restricted sensitivity, photointerference, and matrix-dependent inaccuracy when detecting biological samples. In this work, we fabricated a PEC platform exploiting an ultrahigh-photocurrent CdS/polyaniline (CdS/PANI) heterostructured film to facilitate accurate and selective nitrite detection as a biologically important health parameter of exercise-induced NO metabolism. When the CdS quantum structure is combined with the conductive PANI, strongly increased visible light absorption efficiency and more rapid charge separation were achieved, and electron-hole recombination was inhibited. Such synergistic effects result in strong photocurrent responses, with nitrite being an efficient electron acceptor and contribute to a substantial concentration-dependent reduction of the photocurrent. It provides an acceptable limit of detection, a wide linear range, good selectivity toward the traditional biological interferents, and stability during use. The proposed CdS/PANI PEC system offers a rapid, cost-effective, and analytically powerful strategy for evaluating exercise-induced metabolic changes and highlights its strong potential for future applications in sports physiology, biomarker detection, and personalized performance monitoring.