Novel Glycosylated Naphthalimide-based Activatable Fluorescent Probe: A Tool for Assessment of Hexosaminidase Activity and Intracellular Hexosaminidase Imaging.

The development of effective detection methods for hexosaminidase is of great importance for rapid screening of potential inhibitors in vitro and for early diagnosis of related diseases ex vivo. In this study, the activatable fluorescent probes that are based on naphthalimide decorated with ethylene glycol units were synthesized using N-acetyl-β-D-glucosaminide as a hexosaminidase-responsive group. When exposed to this enzyme, the glucoside-linked naphthalimide moiety of 1c can be cleaved quickly with significant changes in both color (from colorless to yellow) and fluorescence (from blue to green). The probe 1c shows better wa-ter-solubility and fluorescence properties than the common substrate 4-methylumbelliferyl N-acetyl-β-D-glucosaminide. Further-more, the response mechanism of 1c to hexosaminidase was evaluated using HPLC analysis and TD-DFT calculations. Molecular docking was performed to investigate the interaction mode. In addition, 1c has been successfully achieved straight-forward rapid discovery of effective hexosaminidase inhibitors. Fluorescence imaging experiments indicate that 1c has good cell safety and can be employed as a useful tool for detecting intracellular hexosaminidase activity.