One-pot synthesis of fluorescent nanoprobes based on D-cys-based CDs and quantitative detection of lysine enantiomers

The recognition of amino acid enantiomers is of great significance in drug research and disease diagnosis. However, the similar physical and chemical properties of enantiomers make chiral recognition challenging. Optical characterization is a promising approach to distinguish enantiomers. Carbon dots (CDs) have attracted widespread attention due to their simple synthesis, high economic benefits, and good biocompatibility. Chiral carbon dots, as fluorescent probes, have gradually received more attraction. Here, a fluorescence probe (CYS-CDs + Cu²⁺) was constructed using D-Cys as chiral source to synthesize chiral carbon dots (CYS-CDs), and Cu²⁺ as inducer to recognize the chirality of lysine enantiomers(L-/D-Lys). And then, based on the ability of Cu²⁺ to quench the fluorescence of CYS-CDs and L-Lysine (L-Lys) could restore the fluorescence of the CYS-CDs + Cu²⁺ probe, so achieve an "on-off-on" detection mode to detect L-Lys. On the contrary, D-Lys cannot restore the fluorescence of CYS-CDs + Cu²⁺. The probe can distinguish lysine enantiomers not only by fluorescence spectra but also by circular dichroism spectra. And, the probe can be used for the quantitative detection of L-Lys by fluorescence method, of which the detection range is 0-520 μM, and the limit of detection is only 13.70 μM. In addition, a paper-based fluorescent senor was constructed on this basis. This work may be of practical significance to expand the recognition method of amino acid enantiomers.