Enzyme-free voltammetric sensor for monitoring of creatinine in diabetic patient using sustainable L-cysteine/AuNPs/rGO nanocomposite.

Accurate, non-invasive and routine monitoring of urinary creatinine (Crt) is essential for the early diagnosis of kidney dysfunction in diabetic patients. However, traditional enzymatic and Jaffe's assays suffer from limitations such as enzyme instability, high costs, and complex protocols. In this study, an electrochemical biosensor for creatinine monitoring in diabetic patient urine samples was developed using gold nanoparticles and reduced graphene oxide (AuNPs/rGO) nanocomposite synthesized by using L-cysteine as a sustainable reducing and stabilizing agent. Structural and electrochemical characterization using UV- Visible spectroscopy (UV-Vis), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Transmission electron microscopy (TEM), and Cyclic voltammetry (CV) confirmed the successful synthesis of nanocomposite. The prepared biosensor demonstrated a wide linear range (50-1000 μM) with a detection limit of 38.62 μM for DPV and 30.66 μM for SWV at physiological pH 7.4. The biosensor exhibited exceptional selectivity against common interferents present in urine (glucose, urea, uric acid, ascorbic acid), with <5% signal variation. Furthermore, biosensor demonstrated good stability over one month, with only 3.76% signal loss. The biosensor was further validated using urine samples of diabetic patients, yielding a recovery of 96.12% (RSD 2.25%). This study reports, for the first time, the development of a non-enzymatic AuNPs/rGO based electrochemical biosensor for creatinine monitoring from diabetic urine samples, highlighting its significant role in terms of material design, sensitive detection, resistance to interference, and clinical applicability for regular monitoring of creatinine in diabetic patients.