Rational Design for Multicolor Flavone-Based Fluorophores with Aggregation-Induced Emission Enhancement Characteristics and Applications in Mitochondria-Imaging.

Liyan Liu,Yaohui Lei,Jianhui Zhang,Na Li,Huaqiao Wang,Fan Zhang,Feng He

doi:10.3390/molecules23092290

Abstract

Fluorophores with aggregation-induced emission enhancement (AIEE) properties have attracted more attention in recent years. In order to realise more valuable applications, the different kinds of AIEE molecules are in serious need of further development. Therefore, a novel flavone-based AIEE system derived from restriction of intramolecular rotation (RIR) was designed and synthesized in this work. The results revealed that six of the compounds showed typical AIEE characteristics, with fluorescence emissions from purple, blue, cyan to green, tunable by changing substituent groups. This flavone-based AIEE system has never been reported before. The AIEE characteristics were investigated by optical spectroscopy, fluorescence photographs, scanning electron microscopy (SEM), fluorescence quantum yields (ФF) and fluorescence lifetime in the CH3OH/H2O mixed solution. Moreover, benefiting from the simple structures and small molecular weight, they could permeate cells faster than current high-molecular-weight AIEE molecules. Furthermore, to examine possible biomedical applications, fluorescence imaging in living A549 lung cells and cell viabilities were examined, and the results displayed that these fluorophores showed good cellular uptake and low cytotoxicity within the experimental concentration range. In addition, these AIEE compounds possessed excellent specificity for mitochondrial targeting and mitochondrial morphological change tracking, besides, they displayed superior photostability, which indicated they are potential candidates for mitochondrial imaging.

Highlights

Fluorophores have received a great deal of attention in the areas of fundamental photophysics research and applications in biology, medicine, pharmacy and other fields [1,2,3,4]
The conventional organic fluorophores frequently suffer from aggregation-caused quenching (ACQ) [5], whereby their fluorescence emission becomes weaker when the concentration of the solution increases, which limits their applications
A novel aggregation-induced emission enhancement (AIEE) system involving flavone-based derivatives was developed based on our previous study of AIEE molecules

Summary

Introduction

Fluorophores have received a great deal of attention in the areas of fundamental photophysics research and applications in biology, medicine, pharmacy and other fields [1,2,3,4]. The conventional organic fluorophores frequently suffer from aggregation-caused quenching (ACQ) [5], whereby their fluorescence emission becomes weaker when the concentration of the solution increases, which limits their applications. The novel luminescence phenomenon of aggregation-induced emission (AIE) was first discovered by Tang’s group in. Some mechanisms for the observed properties have been put forward, including restriction of intramolecular rotation (RIR), restriction of intramolecular charge transfer, E-Z isomerization, planarization, J-type aggregate formation and twisted intramolecular charge transfer (TICT). Among these factors RIR is considered to be the main cause [10,11,12,13,14,15,16]

Methods

Results

Conclusion