A chiral sensing platform with reversible chirality based on Au nanoparticles-d-methionine/chitosan

Abstract

Au nanoparticles (AuNPs) is first combined with d-methionine (d-Met) through Au–S bond, and the obtained Au-d-Met was self-assembled with chitosan (CS) via electrostatic driving. Both d-Met and CS are important chiral sources, and therefore the resultant Au-d-Met/CS displays distinct chirality. Interestingly, the chirality of the Au-d-Met/CS can be reversed depending on the ratio of d-Met to CS, as revealed by circular dichroism spectra. Due to the high electrical conductivity of AuNPs as well as the intrinsic chirality of d-Met and CS, the resultant Au-d-Met/CS is used as the electrochemical chiral sensing platform for the discrimination of tryptophan (Trp) enantiomers. Although the Trp enantiomers can be successfully discriminated by the developed chiral sensing platform, the electrochemical signals of l-Trp and d-Trp can be reversed on the differential pulse voltammograms (DPVs) when different ratios of d-Met to CS are used, which can be ascribed to the reversible chirality of the Au-d-Met/CS complexes prepared by different ratios of d-Met to CS.