Rational design of a NIR fluorescent probe and its application in food detection of viscosity and biosystem imaging

Viscosity is one of the most important parameters of liquid foods and shows significant change during food spoilage. It is also an important component of the cell microenvironment and is closely associated with the development of liver injury. In this work, a viscosity-sensitive fluorescent probe named WZ-V based on the twisted intramolecular charge transfer (TICT) mechanism was successfully designed. WZ-V had a large Stokes shift, long wavelength emission, and the fluorescence intensity shows 290-fold enhancement in high viscosity. Probe WZ-V successfully detected viscosity changes caused by food thickeners, as well as in milk, orange juice, and lemonade spoilage processes. This provides a new tool for regulating the viscosity of liquid foods and monitoring viscosity changes during food spoilage. In addition, WZ-V has been successfully applied to image viscosity changes in liver injury, which provides an important reference for the study of liver diseases.