Construction of a Chiral Fluorescent Probe for Tryptophan Enantiomers/Ascorbic Acid Identification

Abstract

Chiral recognition of amino acid enantiomers is critical in enhancing drug efficacy, detecting disease markers, and understanding physiological processes. Enantioselective fluorescent identification has gained attention among researchers due to its nontoxicity, easy synthesis, and biocompatibility. In this work, chiral fluorescent carbon dots (CCDs) were produced through a hydrothermal reaction followed by chiral modification. The fluorescent probe, Fe3+-CCDs (F-CCDs), was constructed by complexing Fe3+ with CCDs to differentiate between the enantiomers of tryptophan (Trp) and determine ascorbic acid (AA) through an “on–off–on” response. It is worth noting that l-Trp can greatly enhance the fluorescence of F-CCDs with a blue shift, whereas d-Trp does not have any effect on the fluorescence of F-CCDs. F-CCDs showed a low limit of detection (LOD) for l-Trp and l-AA, with an LOD of 3.98 and 6.28 μM, respectively. The chiral recognition mechanism of tryptophan enantiomers using F-CCDs was proposed based on the interaction force between the enantiomers and F-CCDs, as confirmed by UV–vis absorption spectroscopy and density functional theory calculations. The determination of l-AA by F-CCDs was also confirmed through the binding of l-AA to Fe3+ to release CCDs, as seen in UV–vis absorption spectra and time-resolved fluorescence decays. In addition, AND and OR gates were constructed based on the different responses of CCDs to Fe3+ and Fe3+-CCDs to l-Trp/d-Trp, demonstrating the significance of molecular-level logic gates in drug detection and clinical diagnosis.

Recent Progress in Detecting Enantiomers in Food

“…In 2023, Li et al employed chiral fluorescent carbon dots (CCDs) to successfully discriminate between the enantiomers of tryptophan (Trp) ( Figure 6 ) [ 19 ]. The CCDs were synthesized via a hydrothermal reaction followed by chiral modification.…”

“…Various analytical techniques have been employed to determine enantiomers in food [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ], including liquid chromatography, spectrophotometry, capillary electrophoresis, and fluorescence analysis. While techniques like high-performance liquid chromatography can effectively identify and separate enantiomers, they suffer from time-consuming procedures, expensive instrumentation, and limited real-time analysis capabilities.…”

Chiral Assembly of Perovskite Nanocrystals: Sensitive Discrimination of Amino Acid Enantiomers

“…The advancement of chiral fluorescent materials has opened a new avenue for the construction of fluorescent chiral sensing platforms. To date, chiral covalent organic frameworks (COFs), CdSe/ZnS quantum dots (QDs), chiral carbon dots (CDs), chiral silicon nanoparticles, aggregation-induced emission luminogens (AIEgens), molecularly imprinted polymers (MIPs), and chiral polyionic liquid were developed and used for the recognition of chiral compounds . Inspired by these studies, we speculate that a chiral perovskite assembly with dual properties of fluorescence and chirality could be used for chiral discrimination of chiral molecular enantiomers.…”

Modifying carbon dots with l-phenylalanine for rapid discrimination of tryptophan enantiomers

“…4–6 Therefore, in order to avoid side-effects in drug research and development as much as possible, it is essential to develop new and efficient methods to discriminate Trp enantiomers. 7…”