Design of Activatable NIR-II Molecular Probe for In Vivo Elucidation of Disease-Related Viscosity Variations

Abstract

A clear elucidation of a disease-related viscosity change in vivo is significant yet highly challenging as well. Fluorescence imaging in the second near-infrared region (NIR-II, 1000-1700 nm) has gained increasing attention for observation in living organisms, but a viscosity-activatable fluorescent probe emitting at this region remains a vacancy. Herein, we report the first panel of a viscosity-activated NIR-II emissive fluorescent probe <b>WD-X</b>. By embedding different substituents into the <b>WD-X</b> platform and screening, we obtained an ideal probe, <b>WD-NO</b>_<b>2</b>, which displayed the best combination of properties, including a 31-fold fluorescence enhancement in response to viscosity, insensitivity to environments (pH, polarity), and relatively high quantum yield (1.6% in glycerol). <b>WD-NO</b>_<b>2</b> was successfully applied to track the variation of viscosity in diabetes-induced liver injury in vivo.