An electrochemical chiral sensor based on electrochemically modified electrode for the enantioselective discrimination of D-/L-tryptophan

Chirality is a universal characteristic of natural systems and discrimination of enantiomers of a chiral molecule plays a major role particularly in chemical biology and in pharmacology. In this study, a novel electrochemical chiral sensor was developed for direct discrimination of D- and L-tryptophan (Trp) in an aqueous medium. The chiral sensor was produced by hierarchical modification of reduced graphene oxide, gold nanoparticles, poly-L-cysteine, and poly-L-phenylalanine methyl ester on the glassy carbon electrode. Each of the layers was produced by electrochemical techniques, such as electrochemical reduction and polymerization. After structural and morphological characterizations, the electrochemical behaviors of the enantiomeric pairs of Trp at the modified electrode were investigated by cyclic voltammetry and square wave voltammetry. A distinctive separation between the oxidation peak potentials of D- and L-Trp was observed at 0.73 and 0.83 V, respectively. In order to investigate the amperometric response towards D- and L-Trp, chronoamperometry technique was also used in the concentration range of 0.1–0.8 mM. Furthermore, the electrochemical performance of the modified electrodes was investigated in a mixed solution of D- and L-Trp. The results showed that the prepared electrode could be used as an electrochemical chiral sensor for Trp enantiomers.