Construction of a Novel Ph- and Viscosity-Switchable Near Infrared Fluorescent Probe and its Imaging Application

Viscosity is an important parameter to measure the fluidity of liquid, it is also used as a key indicator in biological tissue and lesions to evaluate the states of body fluid. Most of the traditional detection methods exhibit many drawbacks such as the short emission wavelength, interference by background fluorescence. Herein, inspired by the unique multi double bond structure of retinal, a novel pH and viscosity dual response fluorescent probe (Rh-TR) was constructed. Rh-TR exhibited two emission signals centered at 510 nm and 660 nm. The fluorescence at 510 nm increased by about 124-fold, while the fluorescence change at 660 nm is not obvious with the increase of pH values in PBS. When detect viscosity change by the probe, the fluorescence at 510 nm decreased by about 85%, while, the fluorescence at 660 nm increased by over 20 times. The probe also shown high selectivity and little toxicity. As proved by biological imaging experiment, the probe can successfully image the pH and viscosity change in cells and zebrafish environment. Together with the unique structure of Rh-TR with retinal part and the attractive pH- and viscosity-switchable spectral property, the probe may find further application in many fields such as the viscosity related diseases and industry detection area.