A sensitive electrochemical sensor for chiral detection of tryptophan enantiomers by using carbon black and ß­cyclodextrin.

ABSTRACT

A chiral sensor for the electrochemical identification of tryptophan (Trp) isomers is described. The electrochemical sensor was prepared based on the combination of (a) carbon black (CB-COOH) as conductive material, (b) Cu2+-modified ß-cyclodextrin (Cu-ß-CD), and (c) ß-CD-based metal-organic frameworks (ß-CD-MOF) as chiral selectors. The Cu-ß-CD can be self-assembled into the CB-COOH and ß-CD-MOF through electrostatic interactions, which was characterized by zeta potential analysis. UV-vis spectroscopy proved that Cu-ß-CD displays a higher combination for D-Trp than L-Trp, and the ß-CD-MOF at the surface of the GCE has a higher affinity for L-Trp than D-Trp, which endow an easier permeation of L-Trp to the surface of the electrode, thus leading to a larger electrochemical signal of differential pulse voltammetry (DPV). The enantioselectivity for L-Trp over D-Trp (IL/ID) is 2.13, with a low detection limit for D-Trp (11.18 µM) and L-Trp (5.48 µM). In addition, the proposed chiral sensor can be chosen to determine  the percentage of D-Trp in enantiomer mixture solutions and real sample detection with a recovery from 98.2 to 102.8% for L-Trp and 97.9 to 101.1% for D-Trp.