An electrochemical chiral sensor based on amino-functionalized graphene quantum dots/β-cyclodextrin modified glassy carbon electrode for enantioselective detection of tryptophan isomers

An electrochemical chiral sensing platform based on amino-functionalized graphene quantum dots/beta-cyclodextrin modified glassy carbon electrode -(NH2-GQDs/beta-CD/GCE) was developed for enantioselective detection of tryptophan (Trp) isomers. -NH2-GQDs/beta-CD/GCE showed high electrocatalytic activity and good analytical behavior toward the oxidation of Trp isomers. The oxidation peak potentials and oxidation peak currents of Trp isomers at -NH2-GQDs/beta-CD/GCE surface were observed by differential pulse voltammetry. -NH2-GQDs/beta-CD nanocomposite exhibited different binding ability for two Trp isomers and selectively bonded with d-Trp, resulting in the higher oxidation peak current of d-Trp at -NH2-GQDs/beta-CD/GCE surface. Trp isomers exhibited different oxidation peak potentials at -NH2-GQDs/beta-CD/GCE surface, and the peak potential separation between l-Trp and d-Trp was around 0.022 V, which was used for the enantioselective detection of Trp isomers. Under the optimum experimental conditions, the oxidation peak currents were linearly dependent on the concentrations of Trp isomers. The linear ranges of l-Trp and d-Trp were all from 1.0 to 30.0 mu M with correlation coefficients of 0.9886 and 0.9800, respectively. The detection limits of l-Trp and d-Trp were 0.65 and 0.12 mu M (3 sigma/K), respectively. Such -NH2-GQDs/beta-CD/GCE displayed high antiinterference against some physiological substances, good reproducibility and excellent long-term stability toward Trp isomers detection in biomedical applications.