Phototriggered Migration of Indole-Based Cationic Fluorophore from Mitochondria to Nucleolus in Live Cells

Abstract Small-molecule fluorescence probes capable of migrating between subcellular organelles under varying cellular conditions are essential tools for investigating live cell events. In this work, we present TNK-01, synthesized from pyridinium salt and indole derivatives known for their affinity to nucleic acids and ability to target mitochondria. TNK-01 exhibits migration from mitochondria to the nucleolus upon continuous light irradiation, driven by its differential binding affinities for the negatively charged mitochondrial membrane and RNA. The photo-triggered migration of TNK-01 is enhanced by its RNA binding affinity, resulting in an approximate 32-fold increase in fluorescent signal with selectivity for RNA over DNA. Furthermore, TNK-01 demonstrates stable emission across a pH range of 3 to 8, allowing for effective monitoring of translocation across various cell lines. Its large Stokes shift, high photostability, wash-free imaging, and low cytotoxicity make TNK-01 a promising tool for cellular imaging in live cells. This photo-triggered indole-based fluorescent probe enables new research in mitochondrial studies and organelle communication, which are increasingly important for understanding metabolism and disease progression.