Diketopyrrolopyrrole-based multifunctional ratiometric fluorescent probe and γ-glutamyltranspeptidase-triggered activatable photosensitizer for tumor therapy†
Photosensitizers can generate highly reactive oxygen species (ROS) by light excitation, causing cell damage and apoptosis. However, conventional photosensitizers cannot kill cancer cells selectively. In this work, we report a series of diketopyrrolopyrrole (DPP)-based photosensitizers, in which DPP-py with one pyridine group exhibits superior photodynamic killing effect on tumor cells. Furthermore, by introducing 4-bromomethyl-phenyl glutamic acid in DPP-py, we adopt a strategy involving the intramolecular charge transfer effect to develop a multifunctional DPP-based ratiometric fluorescent probe and activatable photosensitizer DPP-GGT, which can target the tumor-related biomarker γ-glutamyltranspeptidase (γ-GT). DPP-GGT shows highly selective and obvious fluorescent changes from red to yellow for γ-GT. More importantly, DPP-GGT exhibits specific photodynamic killing effects on human hepatic cancer cells HepG2 due to the high activity of endogenous γ-GT but no marked phototoxicity toward low-γ-GT-expressing breast cancer cells MCF-7 or normal hepatocyte cells L02. The results demonstrate that DPP-GGT has great potential for the tumor-specific activatable photodynamic anticancer therapy.