| As a basic feature in life processes, chiral recognition has attracted increasing interest since the two enantiomers of a chiral compound generally have different biological activities. Currently, gold nanparticles (AuNPs) as colorimetric probes are widely used in the bioanalysis fields. In this thesis, we applied AuNPs as colorimetric probes into chiral recognition.1. Visual chiral recognition of Dopa using L-cysteine modified gold nanoparticles as colorimetric probesIn this work, we adsorbed L-cysteine onto the surface of AuNPs to obtain L-cysteine-capped AuNPs. L-cysteine-capped AuNPs are used as chiral selector for D-and L-Dopa. In the presence of L-Dopa, an appreciable red-to-blue color change of AuNPs solution can be observed, whereas no color change is found in the presence of D-Dopa. The chiral assay described in this work is easily readout with the naked eye or using a UV-vis spectrometer. Furthermore, the AuNPs can selectively adsorb L-Dopa, and simple centrifugation can allow the precipitation of L-Dopa with AuNPs and leave a net excess of the other enantiomer in solution, thus resulting in enantioseparation. We also find that AuNPs are capable of colorimetric recognition L-Tyrosine which provides a potential technique for enantioseparation of amino acids.2. Visual chiral recognition and quantification of tryptophan using unmodified gold nanoparticles as colorimetric probesA simple protocol to distinguish enantiomers is extremely intriguing and useful. In this study, we propose a low-cost, facile, sensitive method for visual chiral recognition of enantimers. It is based on the inherent chirality of AuNPs, and the unmodified AuNPs are used as chiral selector for D-and L-Tryptophan (Trp). In the presence of D-Trp, an appreciable red-to-blue color change of AuNPs solution can be observed, whereas no color change is found in the presence of L-Trp. The chiral assay described in this work is easily readout with the naked eye or using a UV-vis spectrometer. Furthermore, the AuNPs can selectively adsorb D-Trp, and simple centrifugation can allow the precipitation of D-Trp with AuNPs and leave a net excess of the other enantiomer in solution, thus resulting in enantioseparation. In this method, AuNPs do not need any labeling or modifying with chiral molecules. The method is more attractive because of its high sensitivity, low cost, ready availability and simple manipulation. |
