A novel fluorescent probe based on indole-fused 1,8-naphthalimide derivative for rapid discrimination of H2S, Cys, and Hcy/GSH and its multi-functional applications

In view of the vital roles in biological systems, it is significant and challenging to construct a fluorescent probe that can simultaneously detect and discriminate the most important four reactive sulfur species (H2S, Cys, Hcy/ GSH). Herein, a smart fluorescent probe Indole-NI-NBD based on indole-fused 1,8-naphthalimide derivative has been rationally designed and synthesized. This probe displayed fast, selective and sensitive responses for these four reactive sulfur species with distinct fluorescent turn-on signal changes at 595 nm. Moreover, the unique absorbance enhancement at 575 nm and the distinct color change achieved "naked eye" detection of H2S. The distinctive fluorescence enhancement at 560 nm only for Cys achieved its discrimination from H2S, and Hcy/ GSH. More importantly, using Indole-NI-NBD-loaded test strips and RGB experiment, a smartphone sensing platform was constructed and realized the convenient, reliable, and on-site detection of H2S and Cys. Finally, Indole-NI-NBD was applied to image H2S, Cys, Hcy/GSH and distinguish Cys from them in living cells and zebrafish via different fluorescence signals at a single excitation wavelength.