A Highly Effective Electrochemical Chiral Sensor of Tryptophan Enantiomers Based on Covalently Functionalize Reduced Graphene Oxide with L-Lysine

A fast electrochemical chiral sensor based on L-lysine (L-Lys) covalent functionalize reduced graphene oxide (RGO) has been developed for electrochemical recognize of tryptophan (Trp) enantiomers. The reduced graphene oxide/L-Lys (RGO/L-Lys) chiral composites with excellent water-soluble and biocompatible is very suitable for electrochemical sensor. Meanwhile, the L-Lys retains original chirality in RGO/L-Lys composites, which progress to electrochemical chiral sensor. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) were implemented to monitor the electrochemical behavior when RGO/L-Lys simply modified on glassy carbon electrode (RGO/L-Lys/GCE). Surprisingly, the reduction of peak current was significantly different after the RGO/L-Lys composites interacted with L-Trp or D-Trp, and the testing time is very short. It suggested that the RGO/L-Lys/GCE can be used as an electrochemical chiral sensor for the discrimination of Trp enantiomers. In this electrochemical discrimination process, the three-point interaction between L-Lys and Trp enantiomers has played an important role. Further research indicated that the decreased of peak currents versus percentage of L-Trp of Trp racemic mixture exhibits a fine linear relationship, it provides opportunity to make analysis for discrimination of Trp enantiomers. The RGO/L-Lys/GCE electrochemical chiral sensor with rapid recognition, good sensitivity and high stability provided an efficient method to recognize and determine Trp enantiomers.