A mitochondria-targeted dual-response fluorescent probe with large Stokes shift for visualizing viscosity and cysteine in cancer cells and zebrafish

Mitochondrial cysteine (Cys) and viscosity are closely associated with numerous cellular processes and diseases. Developing a method capable of real-time tracking of viscosity and Cys in mitochondria is crucial for understanding cell status and mitochondria-related diseases. In this study, we developed a mitochondria-targeted fluorescent probe (Mito-QP) with a large Stokes shift of 171 nm for detecting Cys and viscosity. The acryloyl group enabled Mito-QP specific response to Cys with high sensitivity. The probe exhibited significant red fluorescence enhancement with increasing viscosity due to restricted intramolecular rotation. Additionally, Mito-QP showed low cytotoxicity and excellent mitochondrial-targeting ability. The probe was successfully employed to monitor fluctuations in mitochondrial viscosity and Cys in cancer cells and zebrafish. This work provides a convenient and effective sensor for studying mitochondrial dysfunction.