A highly efficient chiral sensing platform for tryptophan isomers based on a coordination self-assembly

Construction of convenient and effective method for enantiomer identification is of vital significance for biochemistry and medical science. Herein, we design an effective sensor for chiral recognition of tryptophan (Trp) enantiomers, and self-assembly of Cu2+-modified β-cyclodextrin on poly-L-arginine/multi-walled carbon nanotubes (Cu-β-CD/PLA/MWCNTs) is studied. Meanwhile, Cu2+ acts as a cap to prevent the release of the high energy water and compel Trp enantiomer into the smaller opening of β-cyclodextrin. Recognition of L-Trp is accomplished by the formation of hydrogen bonds between the amino of L-Trp and the high energy water confined in cavity of Cu-β-CD. Compared with D-Trp, the sensor exhibits favorable chiral recognition toward L-Trp with a separation coefficient of 3.37. And the chiral sensor presents admirable enantiomers determination with excellent sensitivity, providing a good linear correlation in the range of 1 × 10-6 M~5.5 × 10-5 M, and the detection limit can reach 3.3 × 10-7 M (S/N = 3). Besides, the proposed sensor has been able to predict the percentage of D-Trp in the racemic mixture, suggesting its potential applications in the enantiomer recognition field.