Fenton-Reaction-Acceleratable Magnetic Nanoparticles for Ferroptosis Therapy of Orthotopic Brain Tumors

Cancer is one of the leading causes of morbidity and mortality in the world, but more cancer therapies are needed to complement existing regimens due to problems of existing cancer therapies. Herein, we term ferroptosis therapy (FT) as a form of cancer therapy and hypothesize that the FT efficacy can be significantly improved via accelerating the Fenton reaction by simultaneously increasing the local concentrations of all reactants (Fe²⁺, Fe³⁺, and H₂O₂) in cancer cells. Thus, Fenton-reaction-acceleratable magnetic nanoparticles, i.e., cisplatin (CDDP)-loaded Fe₃O₄/Gd₂O₃ hybrid nanoparticles with conjugation of lactoferrin (LF) and RGD dimer (RGD2) (FeGd-HN@Pt@LF/RGD2), were exploited in this study for FT of orthotopic brain tumors. FeGd-HN@Pt@LF/RGD2 nanoparticles were able to cross the blood-brain barrier because of its small size (6.6 nm) and LF-receptor-mediated transcytosis. FeGd-HN@Pt@LF/RGD2 can be internalized into cancer cells by integrin α_vβ₃-mediated endocytosis and then release Fe²⁺, Fe³⁺, and CDDP upon endosomal uptake and degradation. Fe²⁺ and Fe³⁺ can directly participate in the Fenton reaction, whereas the CDDP can indirectly produce H₂O₂ to further accelerate the Fenton reaction. The acceleration of Fenton reaction generates reactive oxygen species to induce cancer cell death. FeGd-HN@Pt@LF/RGD2 successfully delivered reactants involved in the Fenton reaction to the tumor site and led to significant inhibition of tumor growth. Finally, the intrinsic magnetic resonance imaging (MRI) capability of the nanoparticles was used to assess and monitor tumor response to FT (self-MRI monitoring).