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

## TL;DR

This paper introduces a new approach to using magnetic agents for glioma treatment by repurposing them to enhance magnetic field therapy, leading to better tumor suppression.

## Contribution

The novel strategy repurposes Fe3O4 and GA as magnetic field therapy enhancers, moving beyond traditional roles in imaging or hyperthermia.

## Key findings

- Fe3O4 and GA, when combined with an external magnetic field, significantly increased tumor growth inhibition in glioma-bearing mice.
- The magnetic field therapy disrupted tumor angiogenesis and reduced microvessel density, impairing tumor nutrient supply.
- Reduced infiltration of CD4+ and CD8+ T cells confirmed the blockade of tumor perfusion.

## Abstract

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.