Photo-Triggered Migration of Indole based Cationic Fluorophore from Mitochondria to Nucleolus in live cells

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.