Deciphering the Mitochondrial Viscosity and Interplay Between Mitochondria and Plasma Membrane Using Far Red-emitting Molecular Rotor

The dysfunctions in the mitochondria are associated with various pathological conditions like neurodegeneration, metabolic disorder, and cancer, leading to dysregulated cell death. Here, we have designed and synthesized a julolidine-based molecular rotor (JMT) to target mitochondria with far-red emission accounting for mitochondrial dysfunction. JMT showed an excellent viscosity sensitivity with 160-fold and 4-times enhancement in fluorescence intensity and lifetime, respectively. The origin of the dark state in a lower viscous environment was investigated through density functional calculations. JMT has monitored mitochondrial dysfunction under stressed and inflammatory conditions. Moreover, we reported tracking small fluorescent molecules switching from mitochondria to the plasma membrane. On treating the mitochondria potential uncoupler, JMT relocates to the cell membrane and can be utilized for understanding the interplay between mitochondria and cell membranes.