FeS-loaded nitrogen-doped carbon nanozymes for sensitive colorimetric detection of xanthine in urine samples

Abstract

As a key alkaloid, the concentration of xanthine in the body often reflects various physiological or pathological states of the human body. However, conventional methods for xanthine detection often suffer from time-consuming procedures and a narrow linear range. The present study screened 30 nanozymes with varying Fe/S molar ratios using a hydrogen peroxide-3,3′,5,5′-tetramethylbenzidine (H₂O₂–TMB) colorimetric system and identified the FeS-loaded nitrogen-doped carbon nanozyme (Fe300S5-NC) as a highly efficient catalyst. Inspired by the biological metabolic pathway of xanthine, an XOD/Fe300S5-NC/TMB colorimetric system was constructed for the detection of xanthine. The constructed colorimetric sensing platform demonstrated facile operation and rapid response, with a linear xanthine detection range of 10–1000 μM and a detection limit of 0.97 μM. This work provides a viable strategy for designing artificial enzymes with high peroxidase-like activity, indicating potential for biosensing applications.