Dual-emissive near-infrared fluorescent probe revealing fluidity changes in lysosomal membranes during lysosomal fission and fusion

Lysosomal membranes fluidity is a crucial parameter closely relative to lysosomal fission and fusion, autophagy, endocytosis, and exocytosis. However, fluorescent probes for the visualization of lysosomal membranes fluidity were rarely reported. In this work, by linking an amine moiety on a polarity-responsive near-infrared fluorophore, we have constructed a well membrane permeable probe ( DMA ) to visualize the changes in lysosomal membranes fluidity in dual-channel mode. GUVs and lipid treatment experiments demonstrated that DMA enabled visualization of the increase and decrease of lysosomal membrane fluidity with red-shifted and blue-shifted emission, respectively. With the unique probe, the up-regulated fluidity of lysosomal membranes under starvation in buffer was revealed for the first time. The increased fluidity should be attributed to the lysosomal membrane fusing with other organelles facilitated by the treatment at low level of amino acids. The firstly increased and then decreased lysosomal membranes fluidity during ferroptosis were successfully observed. Particularly, the changes in membrane fluidity were in-situ and real-timely visualized during lysosomal fission and fusion. Lysosomal membrane fluidity was initially up-regulated before lysosomal fusion, and down-regulated after the fusion procedure was completed. The membrane fluidity was also up-regulated after lysosomal fission. • A dual-emissive NIR probe was successfully constructed to visualize the fluidity of lysosomal membranes. • The probe was highly membrane permeable illuminating lysosomes with the loading concentration of 1 nM. • The up-regulated lysosomal membrane fluidity under nutrient-less conditions and ferroptosis has been revealed. • The membrane fluidity regulation during lysosomes fission and fusion was also visualized.