Breaking the delivery barrier: magnetic nanoparticles at the Nexus of imaging and theranostics.

Cancer is still one of the major causes of death globally, and the lack of specificity of current chemotherapeutic and imaging agents still remains to be a major issue in the therapy of cancer, which lead to the lack of efficacy and high systemic toxicity. Magnetic nanoparticles (MNPs) especially Superparamagnetic Iron Oxide Nanoparticles (SPION) and Ultrasmall Superparamagnetic Iron Oxide Nanoparticles (USPION) have shown potential as theranostic platforms due to their magnetic responsiveness, biocompatibility, and multiple functionalities. The advantages of iron oxide-based nanomaterials such as Fe3O4 (magnetite) and maghemite (γ-Fe2O3) are that multiple imaging, targeting, hyperthermia and drug delivery modalities can be integrated into a single material, allowing for improved antitumoral efficacy while reducing off-target toxicity. The recent progress in the synthesis, surface modification of magnetic nanoparticles with biocompatible polymers and targeting ligands, and their physicochemical characterization, for optimization of biological performance, is summarised. Special attention is given to the strategies for targeted and controlled delivery such as magnetic field guided localization, stimuli responsive drug release, ligand mediated targeting, and multifunctional nanocarrier design. Additionally, recent advances in magnetic resonance imaging (MRI), image-guided therapy, multimodal therapy and clinically relevant theranostic applications are critically discussed. Current challenges in translation are also discussed, such as scale-up, long-term safety, regulatory aspects and clinical translation. In conclusion, the magnetic nanoplatforms based on SPIONs and USPIONs are a very promising approach to precision oncology, combining diagnostic, therapeutic and monitoring functions in a single nanoplatform, which will facilitate the translation of magnetic nanomedicine toward personalized cancer treatment.