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

Abstract

In this paper, we report Zincke's salt-substituted tetraphenylethylenes 1a and 1b with Cl and PF as counteranions, respectively. The crystal structure of 1b was determined. Both 1a and 1b are almost nonemissive even in the aggregated states. This is attributed to the photoinduced electron transfer from 2,2-bis(4-methoxyphenyl)-1-phenylvinyl-phenyl unit to 1-(2,4-dinitrophenyl) pyridinium unit within 1a and 1b. The results demonstrate that the emissions of 1a and 1b in aqueous solution can be switched on upon either reaction with GSH or light irradiation. On the basis of the reaction between 1a and GSH, 1a 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 1b 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 1b 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 1b shows phototoxicity toward tumor cells such as Hela and U2OS cells.

Recent advances of AIE light-up probes for photodynamic therapy

“…2c ). 44 Due to the PET process from the TPE unit to the 1-(2,4-dinitrophenyl) pyridinium unit (electron accepter), the probe hardly emits fluorescence even in the aggregate state. The removal of 2,4-dinitrophenyl under light illumination breaks PET processes, resulting in strong green fluorescence emission.…”

Aggregation‐Induced Emission Luminogens for Mitochondria‐Targeted Cancer Therapy

“…Zhang et al reported two Zincke's salt substituted tetraphenylethylenes (11 a and 11 b) with Cl À and PF 6 À as counter anions, respectively ( Figure 6). [26] Although they share the same cation structure, the change in counter anion gives rise to different reactivity. 11 a was found to respond to glutathione (GSH) with green fluorescence.…”

Reduced Thiol Compounds – Induced Biosensing, Bioimaging Analysis and Targeted Delivery

“…However, after reacting with RTCs, the bromide group can be partially replaced by –SH group, which could restore the fluorescence of KC‐Br probe (Figure 6). At the same time, intramolecular charge transfer (ICT), makes the fluorescence of KC‐SH stronger, so it can be used for the detection of RTCs [15] . In addition, they also found that the free‐NH 2 group can further react with the products substituted by Cys/Hcy to form related Schiff bases, but this kind of reaction will not occur in compound KC‐GSH, so this probe can specifically recognize GSH with high selectivity and sensitivity, and can be used for GSH imaging in living cells, which lays a theoretical foundation for distinguishing similar biological RTCs (Cys/GSH/Hcy).…”

“…The mechanism of the bimolecular fluorescent probes studied previously was that ICT, leads to serious overlap between probes and the movement of emission bands, which greatly affects the accuracy and resolution of the detection results [6,8,15,39] . In order to solve this problem and improve the resolution of the fluorescent probe, Yang et al .…”

“…The characteristics and surface chemical properties of the delivery carrier can be adjusted, tuning the interactions between the delivery carrier and the RTCs, allowing the precise sustained and controlled release of the drug. In fact, people have gradually realized the importance of RTCs in biology [15] . In this review, we present representative examples to briefly summarize the reaction principles of RTCs‐specific biosensor probes.…”