Naphthylimide-based mitochondrial immobilized probes for polarity-specific imaging of mitochondrial autophagy in cells and mouse cardiac tissue

Abstract

Mitochondrial autophagy is closely related to various diseases such as neurodegenerative diseases and cancer, and changes in mitochondrial polarity are key markers of these diseases. Traditional fluorescent probes rely on membrane potential and often lose signal during key stages of autophagy. This work develops a mitochondria-immobilized fluorescent probe, Mito-NT, which uses naphthylimide as the fluorescent moiety, triphenylamine as the electron donor, pyridine salt as the electron acceptor, and a mitochondrial-targeting group. The probe achieves polarity-dependent fluorescence response through the activation of an intramolecular charge transfer (ICT) mechanism. The active chlorine unit in its structure ensures that the probe remains stable in the mitochondria and is not affected by changes in the membrane potential. Mito-NT exhibits high polarity sensitivity, pH stability, strong interference resistance, and low cytotoxicity, enabling dynamic monitoring of the mitochondrial autophagy process, tracking the fusion of mitochondria and lysosomes, and distinguishing mouse hunger-induced cardiac mitochondrial autophagy (manifested as enhanced fluorescence). This probe provides a powerful tool for mitochondrial autophagy research and related disease diagnosis.