A novel fluorescent probe for high-fidelity imaging of mitochondria viscosity changes

[Display omitted] •A large ''off-on'' fluorescence response (130-fold) with red emission.•A large Stokes shift (119 nm) and high fluorescence quantum yield in glycerol (64.04%).•Being able to target and immobilize mitochondria.•High fidelity imaging of mitochondria. Studies have shown that the changes of mitochondrial viscosity which is close related to its state can be affected by the destruction of ion balance, excessive production of reactive oxygen species, apoptosis and other factors. However, these processes are usually connected to mitochondrial depolarization, causing probes with cationic mitochondrial targeting groups to escape from the mitochondria. As a result, it is impossible to perform high-fidelity imaging of mitochondrial viscosity changes. To solve this problem, we report a novel viscosity probe (MF-V1) which is able to investigate the changes of mitochondrial viscosity under mitochondrial depolarization. Interestingly, MF-V1 exhibited excellent performance, including large ''off-on'' fluorescence response (130-fold), large Stokes shift (119 nm), and high fluorescence quantum yield in glycerol (0.64). More importantly, MF-V1 has been successfully used to monitor viscosity changes of mitochondria under normal and depolarized conditions. Additionally, the new probe was also used to detect viscosity changes in zebrafish and mice, affording a powerful tool for investigating the relationship between mitochondrial viscosity and related diseases.