A TICS-fluorophore based probe for dual-color GSH imaging

Cascading reactions in fluorophores accompanied by the replacement of different fluorescence wavelengths can be used to develop luminescent materials and reactive fluorescent probes. Based on multiple signal channels, the selectivity of probes can be improved and the range of response to guest molecule recognition can be expanded. By regulating the position, number, and activity of active sites in fluorophores, fluorescent probes that successively react with thiol and amino groups in cysteine (Cys), homocysteine (Hcy) have been developed, which can only react with the thiol group of GSH. In this paper, we report the first probe capable of cascading nucleophilic substitution reaction with the thiol group and amino group of GSH at a single reaction site, and showed the dual-color recognition of GSH, which improved the selectivity of GSH also was an extension of GSH probes. The probe Rho-DEA was based on a TICS fluorophore, and the intramolecular cascade nucleophilic substitution reaction occurs with Cys/Hcy. The thiol substitution of the first step reaction with Cys/Hcy was quenched due to intersystem crossing to triplet state, so GSH can be selectively recognized from the fluorescence signal. Rho-DEA has the ability of mitochondrial localization, and finally realized in situ dual-color fluorescence recognition of GSH in mitochondria. A TICS-based fluorescent probe Rho-DEA undergoes cascade nucleophilic substitution reactions with the thiol and amino groups of GSH, accompanied by the generation of red and green fluorescence, respectively, enabling dual-color imaging of GSH in cellular mitochondria.