Simultaneous imaging of lysosomal and mitochondrial viscosity under different conditions using a NIR probe

This article reported a hemicyanine dye fluorescent probe (1), based on benzo[e]indole and aromatic azonia skeleton, for simultaneous detection of viscosity fluctuation in mitochondria and lysosomes. Probe 1 exhibited near infrared emission and high sensitivity towards viscosity of the medium. As the viscosity increases, the rotation of C-C single bond between the benzo[e]indole and the nitrogen heterocycle could be suppressed, and the entire molecular scaffold was coplanar and emitted strong fluorescence due to more delocalized electron distribution. The fluorescence intensity of probe 1 was enhanced 16.2 times at 650 nm as the viscosity increased from 0.89 cP to 865 cP. Correspondingly, the fluorescence quantum yield of probe 1 increased from 4.2% to 49.6%. The change of lg (I-650nm) had a good linear relationship with lgri (viscosity values: 0.89 cP to 8.6 cP), which meant the viscosity of dilute solution could be detected quantitatively. In cell experiments, probe 1 with low concentration (500 nM) had stronger fluorescence intensity in cancer cells than in normal cells. Besides, probe 1 could monitor the viscosity changes of mitochondria and lysosomes caused by the addition of ionophores (monensin, nystatin and dexamethasone) or in the process of autophagy. The results provide a simple and effective method for the early diagnosis of related diseases.

Automated summary

This study reported a novel fluorescent probe for simultaneous detection of viscosity fluctuation in mitochondria and lysosomes, showing great potential in cell experiments. The probe exhibited stronger fluorescence in cancer cells at low concentrations and could be used for early diagnosis of related diseases.