Tumor Microenvironment-Activated and ROS-Augmented Nanoplatform Amplified PDT against Colorectal Cancer through Impairing GPX4 To Induce Ferroptosis

Photodynamic therapy (PDT) induces apoptosis in cancer cells by generating cytotoxic reactive oxygen species (ROS); however, this effect is constrained by the intrinsic antioxidant mechanisms of the cells and the hypoxic conditions of the tumor microenvironment (TME). To overcome these limitations, a novel ferroptosis-boosted nanophotosensitizer (FCE NPs) is developed after loading alkaloid evodiamine based on an acid-responsive nanoplatform (FC NPs) composed of ferric ions and Chlorin e6 (Ce6). Upon exposure to laser irradiation, the photosensitizer Ce6 efficiently generates singlet oxygen (1O2), which depletes glutathione (GSH), thereby disrupting the redox homeostasis within tumor cells and leading to the oxidation of cellular unsaturated lipid into lipid peroxides (LPO). Additionally, the Fenton reaction between released Fe(III) ions and H2O2 in the TME produces highly cytotoxic hydroxyl radicals (•OH), a form of ROS, causing the accumulation of LPO together with 1O2 to trigger ferroptosis. Following the incorporation of evodiamine, the integrated nanoplatform FCE NPs exhibited excellent antitumor activity through high-performance ferroptosis by inhibiting a glutathione peroxidase 4 (GPX4) level. It was also observed that the key regulator of Wnt signaling pathway β-catenin was downregulated, suggesting the inhibition of FCE NPs on the Wnt signaling pathway. Therefore, this study demonstrated that the FCE NPs could lead to the explosive production of ROS and simultaneous inhibition of GPX4/GSH pathways and the Wnt signaling pathway in colorectal cancer, significantly amplifying the tumoricidal efficacy of PDT through the synergistical sensitization of ferroptosis. This approach offers a promising strategy for the clinical application of ferroptosis therapy.