Exploration of Novel Meso-C═N-BODIPY-Based AIE Fluorescent Rotors with Large Stokes Shifts for Organelle-Viscosity Imaging.

The research on fluorescent rotors for viscosity has attracted extensive interest to better comprehend the close relationships of microviscosity variations with related diseases. Although scientists have made great efforts, fluorescent probes for cellular viscosity with both aggregation-induced emissions (AIEs) and large Stokes shifts to improve sensing properties have rarely been reported. Herein, we first report four new meso-C═N-substituted BODIPY-based rotors with large Stokes shifts, investigate their viscosity/AIE characteristics, and perform cellular imaging of the viscosity in subcellular organelles. Interestingly, the meso-C═N-phenyl group-substituted probe 6 showed an obvious 594 nm fluorescence enhancement in glycerol and a moderate 650 nm red AIE emission in water. Further, on attaching CF3 to the phenyl group, a similar phenomenon was observed for 7 with red-shifted emissions, attributed to the introduction of a phenyl group, which plays a key role in the red AIE emissions and large Stokes shifts. Comparatively, for phenyl-group-free probes, both the meso-C═N-trifluoroethyl group and thiazole-substituted probes (8 and 9) exhibited good viscosity-responsive properties, while no AIE was observed due to the absence of phenyl groups. For cellular experiments, 6 and 9 showed good lysosomal and mitochondrial targeting properties, respectively, and were further successfully used for imaging viscosity through the preincubation of monensin and lipopolysaccharide (LPS), indicating that C═N polar groups potentially work as rotatable moieties and organelle-targeting groups, and the targeting difference might be ascribed to increased charges of thiazole. Therefore, in this study, we investigated the structural relationships of four meso-C═N BODIPY-based rotors with respect to their viscosity/AIE characteristics, subcellular-targeting ability, and cellular imaging for viscosity, potentially serving as AIE fluorescent probes with large Stokes shifts for subcellular viscosity imaging.

A conformationally-locked p-hydroxybenzylidene imidazolinone derivative for detecting Aß42 aggregation.

Alzheimer's disease (AD) is a common type of neurodegenerative disease, which can only be symptomatically relieved but does not yet have a cure. Among the different Aß species, amyloid-ß 42 (Aß42) aggregates are proposed to be more neurotoxic than that of Aß40, and oligomeric Aß42 is thought to play a harmful role in the pathophysiology of AD. Therefore, the detection of Aß42 aggregation is very meaningful in the AD field. We herein report a conformationally-locked p- hydroxybenzylidene imidazolinone derivative, BDI, which exhibits selectivity and specificity towards Aß42 aggregation and remarkable fluorescent enhancement with a large Stokes shift (more than 100 nm). In the fluorescent co-localization study, BDI can sensitively detect a large population of Aß42 aggregation over that of Aß40 in the brain tissues of AD transgenic mouse models. Therefore, this new probe could provide a useful tool for the rapid detection of important Aß species in AD.