Core-shell Cu@Pt nanoparticles and L-cysteine synergistically boosted electrochemical detection for wide-range melatonin detection in biological and food samples

An electrochemical detection method was proposed for the detection of Melatonin (MT) based on the synergistic signal amplification of L-Cys and core-shell Cu@Pt bimetallic nanoparticles (Cu@PtNPs). The successful fabrication of the PL-Cys/Cu@PtNPs/GCE was confirmed by characterization techniques including SEM, XRD, and TEM. The method exhibited excellent analytical performance, with a low detection limit of 0.03 μmol/L and a wide linear range across two concentration intervals: 0.1–100.0 μmol/L and 100.0–900.0 μmol/L. The method's practical applicability was successfully validated in human serum and various food samples, achieving satisfactory recovery rates of 98.73 %–99.67 % and 99.49 %–108.57 %, respectively, with relative standard deviations below 6.85 %. The novelty of this work lies in the synergistic amplification effect of the Cu@PtNPs and L-Cys and the application of density functional theory (DFT) calculations to elucidate the MT electrooxidation mechanism, confirming a 2-electron, 1-proton transfer process.