Repurposing Conventional Magnetic Functional Agents: A Novel Strategy for Long-Acting, Safe, Magnetically Mediated...

Background: Although conventional magnetic functional agents provide a material basis for magnetically mediated tumor therapy, they have long been restricted by the application framework of magnetic resonance imaging (MRI) or magnetic thermal ablation. Methods: This study proposed a repurposing strategy of two mature magnetic functional agents, Fe₃O₄ nanoparticles and gadopentetic acid (GA), by applying their unique magnetic response properties to enhance magnetic field therapy for glioma. Results: Both magnetic materials, when combined with an external magnetic field (MF), showed a synergistic effect to amplify the therapeutic effect. In the CT-2A glioma-bearing mice model, it resulted in marked suppression of tumor growth, with the growth inhibition (TGI) rate increasing from ~27% after MF therapy alone to 64% and 55% after the Fe₃O₄- and GA-potentiated MF therapy, respectively. It was proposed that the MF effect on impairing tumor angiogenesis was enhanced, as evidenced by significant reductions in CD31 expression and microvessel density. It disrupted nutrient supply to the tumor, augmenting the tumor suppression efficiency. The reduced infiltration of CD4+ and CD8+ T cells into tumors further confirmed the effective blockade of tumor perfusion. Conclusions: This study established a new paradigm of conventional magnetic materials to enhance the non-thermal physical effects and biological regulatory effects of magnetic field for glioma therapy, instead of only as the imaging agents or magnetic hyperthermia agents.