Surface engineered gold nanodendrites decorated flexible carbon fiber-based electrochemical sensor platform for sensitive detection of L-Cysteine in serum and urine samples

In this work, highly dispersed gold nanodendrites (Au NDs) decorated flexible carbon fiber electrode (Au NDs@FCF electrode) were fabricated by facile, green, and one-step electrochemical deposition protocol and utilized for the direct electrochemical determination of L-Cysteine (L-Cys). The prepared Au NDs@FCF electrodes were characterized by SEM, HR-TEM, XRD, XPS, CV, and EIS towards the dimensions, surface morphological traits, crystalline nature, chemical composition, and electrochemical catalytic oxidation towards L-Cys and electrochemical active surface area (ECASA) of the Au NDs. The developed Au NDs@FCF electrode demonstrates an enzyme mimics electrocatalytic efficiency towards the oxidation of L-Cys at the operating potential of 0.82 V (vs Ag/AgCl) with a lower experimental detection limit of 0.16 nM, higher sensitivity of ∼50.2 μA μM⁻¹ cm⁻², and a wide concentration ranges from 100 to 3000 nM with a correlation coefficient of R² = 0.996. In addition, the developed Au NDs@FCF electrode has exhibited excellent selectivity with various anti-interferences such as glucose, dopamine, uric acid, Na⁺, Mg²⁺, Ca²⁺, high reproducibility, and repeatability with RSD of 2.3 %. The Au NDs@FCF electrode demonstrates outstanding electrocatalytic oxidation and a rapid sensing response time of ∼3 s. The current Au NDs@FCF electrode achieving the successful detection of L-Cys in practical human serum and urine samples highlights its potential application in biomedical diagnostics. This advancement indicates that the sensor can effectively operate in real-world conditions, offering a valuable tool for medical professionals to monitor L-Cys levels in patients accurately.