Zincke's Salt-Substituted Tetraphenylethylenes for Fluorometric Turn-On Detection of Glutathione and Fluorescence Imaging of Cancer Cells

In this paper, we report Zincke's salt substituted tetraphenylethylenes la and lb with Cl- and PF6- as counteranions, respectively. The crystal structure of lb was determined. Both la and lb are almost nonemissive even in the aggregated states. This is attributed to the photoinduced electron transfer from 2,2-bis(4-methoxypheny1)-1-phenylvinyl-phenyl unit to 1-(2,4-dinitrophenyl) pyridinium unit within la and lb. The results demonstrate that the emissions of la and lb in aqueous solution can be switched on upon either reaction with GSH or light irradiation. On the basis of the reaction between la and GSH, la can be utilized for the fluorescence turn-on detection of GSH selectively, and GSH with concentration as low as 36.9 nM can be detected. The transformation of lb into 2 under light irradiation results in the fluorescence imaging of Hela and U2OS cells and phototoxicity toward Hela and U2OS cells after the protonation of pyridine unit in 2 because of the acidic environment of tumor cells. Aggregates of lb can be up-taken by Hela and U2OS cells and fluorescence imaging has been successfully recorded with CLSM. Moreover, the protonated form of 2 can function as photosensitizer and lb shows phototoxicity toward tumor cells such as Hela and U2OS cells.