An ingenious near-infrared fluorescent probe for detection of viscosity in biosystems and beverages

[Display omitted] •An ingenious fluorescent probe XAN-V was developed for viscosity detection.•XAN-V possesses high selectivity, good stability and low cytotoxicity.•XAN-V could visualize the viscosity in live cells, zebrafish and liver tissues.•XAN-V could monitor viscosity changes in spoiled beverages. Viscosity, as a crucial microenvironmental factor, significantly influences physiopathology processes and intricately linked to food quality. Herein, an ingenious xanthylium-based near-infrared fluorescent probe XAN-V was synthesized for detection of viscosity in biosystems and beverages. In low-viscosity medium, the unrestricted rotation of probe results in faint fluorescence. Conversely, an increase in viscosity leads to a significant rise in fluorescence intensity of XAN-V, attributed to the constrained rotation and reduced non-radiative energy dissipation. Demonstrating good selectivity and stability, as well as low cytotoxicity, XAN-V was successfully employed for viscosity imaging in living cells, zebrafish, and liver tissues, as well as for thickening effects evaluation of different food thickeners in water and beverages. With its versatility, XAN-V could track changes in viscosity of diverse beverages at different temperatures throughout storage duration. This fluorescent probe may serves as a sophisticated tool for monitoring viscosity in biosystems, as well as for ensuring quality control and safety in beverages.