Graphene Oxide Decorated with Ru(II)-Polyethylene Glycol Complex for Lysosome-Targeted Imaging and Photodynamic/Photothermal Therapy

The combination of photothermal therapy (PTT) and photodynamic therapy (PDT) can kill cancer cells more efficiently as compared with PTT or PDT treatment alone. In this work, we use nanohybrid rGO-Ru-PEG composed of reduced nanographene oxide (rGO) sheet and a phosphorescent polyethylene glycol modified Ru(II) complex (Ru-PEG) for combined PTT and PDT of cancer. Photosensitizer and imaging agent Ru-PEG is decorated onto delivery and PTT agent rGO via π-π stacking and hydrophobic interactions. The chemical structure and morphology have been characterized by various methods. The release of Ru-PEG from rGO surface is pH-dependent, and irradiation can increase the release rate considerably. The combined effects of PDT and PTT have been evaluated by cytotoxicity assay under serial irradiation at 808 nm (PTT) and 450 nm (PDT). Mechanism investigation shows that the nanohybrid can induce apoptosis through generation of reactive oxygen species (ROS) and cathepsin-initiated apoptotic signaling pathways under light excitation. rGO-Ru-PEG can be applied to in vivo photothermal imaging, and high treatment efficacy was achieved for in vivo antitumor experiments when irradiated with an 808 nm laser and a 450 nm laser. Our work provides an effective strategy for the construction of multifunctional imaging and phototherapeutic nanohybrids for the treatment of cancer.