Fabrication of a Novel Electrochemical Sensor Using L-Cysteine-Glutaraldehyde-Glutamine-Cu²⁺ Self-Assembled Monolayer on a Gold Electrode for the Determination of Curcumin in Human Blood Serum

Abstract

In this study, a new electrochemical sensor based on self-assembled monolayers of Cys-GA-Gln-Cu²⁺ modified gold electrode was fabricated. The electrocatalytic activity of adsorbed copper ions was utilized to determine the quantitative concentration of curcumin. Techniques such as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) with an external redox probe were used to investigate the layer-by-layer modification on the gold electrode surface. This electrode showed selective and reproducible adsorption for Cu²⁺In the absence of curcumin, the DPV redox peak for Cu²⁺ was observed at about 276 mV with an anodic current of 1.36 μA vs. Ag/AgCl for 5.0×10⁻⁴ M of copper. In the presence of curcumin, an anodic peak was observed at 292 mV vs. Ag/AgCl with 3.86 μA for 5×10⁻⁴ M of Cu²⁺. The results demonstrated that the electrocatalytic properties of copper in the presence of curcumin could be used as a precise sensor for the determination of trace concentrations of curcumin in human blood serum. The differential pulse voltammetric response of the modified SAM electrode was linear against curcumin concentration in the range of 1 × 10⁻⁶ to 1 × 10⁻¹⁰ M with an R²=0.9982 at pH= 5. The relative standard deviation (RSD) determined by DPV was 4.1%. Advantages of the sensor include good sensitivity, selectivity, simple recovery, and an inexpensive preparation method. The detection limit could be estimated 1.31×10^-11 M according to the IUPAC recommendation (3σ).