IFE-based lysosome-targeted probe for different response behaviors to biothiols and bioimaging

Abstract

Biothiols (Cys, Hcy, and GSH) are generated by reducing disulphide bonds with the help of proteolysis in lysosomes, meanwhile three biothiols play the different roles in preserving the optimal activity of lysosomes. It is well-known that different biothiols have different physiological functions, and abnormal levels of different biothiols could trigger different diseases, thus discrimination of three biothiols in lysosomes is very essential. Herein, Nitrobenzodioxzole (NBD) is employed and inner filter effect (IFE) is designed to overcome the insufficient difference identification of NBD-based probes for biothiols. This new probe (Lyso-II-NBD) exhibits almost no fluorescence, upon addition of biothiols, Lyso-II-NBD is first split into Lyso-II-OH with green fluorescence and non-fluorescence S-substituted NBD-compounds (NBD-S-Cys/Hcy/GSH) by nucleophilic substitution reaction, then only NBD-S-Cys/Hcy rapidly undergo the intramolecular rearrangement and form N-substituted compounds (NBD-N-Cys/Hcy) with yellow fluorescence. At this moment IFE process is occurred between Lyso-II-OH and NBD-N-Cys/Hcy, which makes green fluorescence of Lyso-II-OH disappearance and the enhancement of yellow fluorescence by 7.4 times for Cys and 37 times for Hcy, while NBD-S-GSH remains unchanged and only split Lyso-II-OH presents green fluorescence. The co-localization study reveals that Lyso-II-NBD could target lysosomes and discriminate Cys/Hcy and GSH by dual fluorescence channels without interference from each other, indicating Lyso-II-NBD has a good potential in biomedical application.