A Triphenylphosphonium Functionalized AIE Conjugated Macrocyclic Tetramaleimide for Mitochondrial-targeting Bioimaging

Development of subcellular organelle-targeted bioimaging probes is of great importance in the field of early detection of diseases and exploring the behaviors of subcellular organelles. Herein, we present a triphenylphosphonium functionalized conjugated macrocyclic tetramaleimide (TPP-CMT) as a mitochondrial-targeting bioimaging probe. The core of TPP-CMT is obtained by connecting two pyrenes and two benzenes through four maleimides. This unique structure endows TPP-CMT with exceptional far red/near-infrared aggregation-induced emission (FR/NIR-AIE) characteristics. TPP-CMT is an excellent fluorescent emitter in most solvents and even in solid states. The quantum yield of TPP-CMT was higher than 27% when dissolved in common middle-polarity organic solvent and this value remained at 28.2% in its solid state. The introduction of four triphenylphosphonium on maleimide positions endows TPP-CMT with mitochondrial-targeting ability. Thanks to the FR/NIR-AIE characteristics and the mitochondrial-targeting ability, this well-designed fluorescent probe was successfully employed for mitochondrial targeting bioimaging of HeLa and HepG2 cells.