Fluorescent probes based 1,8-naphthalimide-nitrogen heterocyclic for monitoring the fluctuation of mitochondrial viscosity

Abnormal mitochondrial viscosity could lead to diabetes and neurodegenerative diseases, therefore three probes 1a-c for monitoring the fluctuation of viscosity were designed and synthesized in this article. Probes 1a-c were composed of 1,8-naphthalimide derivatives and benzoxazole, benzothiophene or oxazole [4,5-b] pyridine structure through carbon-carbon double bond connection, and their emission wavelengths increased sequentially (1a: 580 nm; 1b: 614 nm; 1c: 630 nm). The single bond between the nitrogen-containing heterocycle and the carbon-carbon double bond served as the viscosity response site. When the viscosity increased from 0.95 cP to 945 cP, the fluorescence intensity of probes 1a-c increased 18.67-fold, 20.34-fold and 18.37-fold, respectively. In 99% glycerol, the fluorescence quantum yields of probes 1a-c were 85.4%, 80.8% and 34.3% respectively. In addition, the excited state lifetime of probe 1c in 80% glycerol (725 ps) was higher than that in 40% glycerol (203 ps). More importantly, the influence of solvent polarity, pH and some potential interfering substances on probes 1a-c were negligible. And cell experiments showed that probes 1a-c could be used for monitoring the fluctuation of the mitochondrial viscosity in HeLa cells.

Automated summary

This article designed and synthesized three chemical probes for monitoring the fluctuation of mitochondrial viscosity, with their emission wavelengths increasing sequentially as the viscosity changed. The probes showed significant fluorescence intensity changes with viscosity variations and exhibited different fluorescence quantum yields in various solvents. Cell experiments demonstrated that these probes could effectively monitor changes in mitochondrial viscosity in HeLa cells.