Tumor-Specific Endogenous Fe^II-Activated, MRI-Guided Self-Targeting Gadolinium-Coordinated Theranostic Nanoplatforms for Amplification of ROS and Enhanced Chemodynamic Chemotherapy

Low drug payload and lack of tumor-targeting for chemodynamic therapy (CDT) result in an insufficient reactive oxygen species (ROS) generation, which seriously hinders its further clinical application. Therefore, how to improve the drug payload and tumor targeting for amplification of ROS and combine it with chemotherapy has been a huge challenge in CDT. Herein, methotrexate (MTX), gadolinium (Gd), and artesunate (ASA) were used as theranostic building blocks to be coordinately assembled into tumor-specific endogenous FeII-activated and magnetic resonance imaging (MRI)-guided self-targeting carrier-free nanoplatforms (NPs) for amplification of ROS and enhanced chemodynamic chemotherapy. The obtained ASA-MTX-GdIII NPs exhibited extremely high drug payload (∼96 wt %), excellent physiological stability, long circulating ability (half-time: ∼12 h), and outstanding tumor accumulation. Moreover, ASA-MTX-GdIII NPs could be specifically uptaken by tumor cells via folate (FA) receptors and subsequently be disassembled via lysosomal acidity-induced coordination breakage, resulting in drug burst release. Most strikingly, the produced ASA could be catalyzed by tumor-specific overexpressed endogenous FeII ions to generate sufficient ROS for enhancing the main chemodynamic efficacy, which could exert a synergistic effect with the assistant chemotherapy of MTX. Interestingly, ASA-MTX-GdIII NPs caused a lower ROS generation and toxicity on normal cell lines that seldom expressed endogenous FeII ions. Under MRI guidance with assistance of self-targeting, significantly superior synergistic tumor therapy was performed on FA receptor-overexpressed tumor-bearing mice with a higher ROS generation and an almost complete elimination of tumor. This work highlights ASA-MTX-GdIII NPs as an efficient chemodynamic-chemotherapeutic agent for MRI imaging and tumor theranostics.