A glutathione responsive pyrrolopyrrolidone nanotheranostic agent for turn-on fluorescence imaging guided photothermal/photodynamic cancer therapy

The high concentration of glutathione (GSH), a feature of solid tumors, can reduce the reactive oxygen species (ROS) damage to cancer cells, which seriously weakens the efficacy of photodynamic therapy in cancer treatment. Herein, we designed and synthesized two kinds of GSH responsive pyrrolopyrrolidone (DPP) derivatives that conjugated with 2-(diphenylmethylene) malononitrile (DPPBPh) and 2,3,3-triphenylacrylonitrile (DPPTPh), respectively. DPPTPh with two -CN groups shows higher singlet oxygen quantum yield and photothermal conversion efficiency than DPPBPh with four -CN groups. These two DPP derivatives can not only be used as colorimetric GSH probes to avoid the fluorescence quenching caused by aggregation, but also enhance the photodynamic/photothermal therapeutic efficacy of their corresponding nanoparticles (NPs). Moreover, DPPTPh NPs exhibit better therapeutic efficacy than DPPBPh NPs even at a low dose (0.2 mg kg(-1)). This work presents DPP derivative-based theranostic nanomedicines for GSH responsive fluorescence "turn on" imaging and enhanced photodynamic/photothermal synergistic therapy.