Vascular-Protective Effects of Cerium Oxide Nanoparticles Complexed with Iron Oxide and Methotrexate: Reversing Atherosclerosis in a Murine Model

Atherosclerosis is a leading cause of cardiovascular morbidity, characterized by chronic inflammation and excessive production of reactive oxygen species (ROS). Despite advances in therapy, effective diagnostic and therapeutic strategies that can both visualize and modulate vascular inflammation remain limited. Here, we designed a chitosan-stabilized cerium oxide–iron oxide nanocomplex conjugated with methotrexate and Cy5 (Chit-IOCO-Cy5-MTX) to achieve simultaneous ROS scavenging, anti-inflammatory activity, and magnetic resonance imaging (MRI). The nanocomplex exhibited strong T2 relaxivity (r2 = 281 mM–1 s–1) and high colloidal stability. In vitro, Chit-IOCO-Cy5-MTX was efficiently internalized by LPS-activated RAW 264.7 macrophages, markedly reducing intracellular ROS levels and suppressing pro-inflammatory cytokines (IL-6, TNF-α, COX-2). In ApoE–/– mice, MRI and ex vivo fluorescence confirmed targeted accumulation in atherosclerotic plaques. Four-week treatment significantly decreased plaque area and inflammatory protein expression compared to saline and non-MTX controls, without detectable systemic toxicity. Overall, this study demonstrates a cerium oxide–iron oxide nanotheranostic platform that enables targeted imaging and effective modulation of oxidative and inflammatory pathways in atherosclerosis, highlighting its translational potential for vascular inflammatory diseases.