Construction of chitosan-based fluorescent probe for real-time monitoring of viscosity changes in living cells with low cytotoxicity and high photostability

Viscosity is a crucial factor influencing diffusion-controlled processes in biological systems. An abnormal increase or decrease in the viscosity level is closely related to various human diseases, such as malignant tumors, coronary heart disease, and cerebral thrombosis. We report a “turn-on” chitosan-based viscosity fluorescent probe (CS-V) for cell-level viscosity measurement. Under viscous conditions, the fluorescence intensity of the probe at a wavelength of 530 nm increased by approximately 56 times and was sensitive to changes in the viscosity level. The probe CS-V was constructed using chitosan (CS) with low toxicity and high biological activity, combined with mitochondrial targeting groups and luminescent groups. As the first chitosan-based probe for viscosity detection, it not only exhibited excellent selectivity and rapid response but also had lower toxicity, better biocompatibility and excellent photostability than small-molecule probes, and can be used for long time fluorescence imaging.