Tumor Microenvironment-Activatable Metal-Phenolic Nanoformulations for Ultrasound-Boosted Ferroptosis through Triple Regulatory Pathways

Abstract

Despite its effectiveness in exterminating tumor cells, ferroptosis is seriously hampered by the high expression of antioxidant glutathione (GSH) and the inadequacy of endogenous H₂O₂ in tumors. Herein, metal-phenolic nanoformulations (FNCP NFs) composed of sonosensitizer Chlorin e6 (Ce6), the phenolic GSH consumer naphthazarin, and Fe³⁺, followed by the modification of PEG2000, are strategically designed and fabricated for ultrasound-boosted ferroptosis in tumor cells through triple regulatory pathways. The carrier-free FNCP NFs can rapidly dissociate under tumor microenvironment response with the assistance of ultrasound, releasing Fe²⁺, Ce6, and naphthazarin. Ce6 and Fe²⁺ are capable of producing singlet oxygen (¹O₂) and hydroxyl radicals (·OH) by ultrasound-activated sonodynamic therapy and Fenton reaction-mediated chemodynamic therapy (CDT), respectively, which not only induce apoptotic cell death but also lead to the effective accumulation of lipid peroxidation (LPO), resulting in ferroptosis. Meanwhile, the released naphthazarin and the self-cycling valence alternations of Fe³⁺/Fe²⁺ promote the significant decrease of intracellular GSH contents, further inducing the inactivation of glutathione peroxidase 4 (GPX4) and the up-regulation of LPO levels, eventually realizing the synergistically enhanced ferroptosis. This facile and feasible design for versatile metal-phenolic nanoformulations offers a new strategy for effectively improving ferroptosis efficiency and multimodal cancer therapies.