Magnetic Nanoparticles for Biomedical Applications

Magnetic nanoparticles (MNPs) are sub-100 nm structures composed of magnetic cores, often iron oxides or ferrites, which exhibit unique magnetic behaviours distinct from their bulk counterparts. Their high surface-to-volume ratio allows precise tuning of magnetic response through control of size, shape and composition. Superparamagnetic behaviour minimises agglomeration and residual magnetism, making MNPs ideally suited for in vivo applications. Surface functionalisation with polymers, ligands or inorganic shells imparts colloidal stability, biocompatibility and targeting capabilities. In diagnostics, MNPs serve as contrast agents for magnetic resonance imaging and as labels for biosensing. In therapy, they enable site-specific drug delivery, magnetic fluid hyperthermia and emerging magnetoelectric neuromodulation. Key design parameters include saturation magnetisation, coercivity, relaxation time and surface chemistry. Recent advances span synthesis of core–shell architectures for enhanced energy conversion, fundamental understanding of size-dependent magnetic domains and systematic evaluation of biological interactions. Together, these developments position MNPs as versatile platforms for global healthcare challenges, from precision oncology to remote neuromodulation.

Research from Nature Portfolio

Recent studies have introduced magnetoelectric nanodiscs with a multilayer core–double-shell architecture combining Fe₃O₄, CoFe₂O₄ and BaTiO₃. These discs convert external magnetic fields into local electric potentials, triggering neuronal depolarisation in vitro and enabling wireless control of rodent motor and reward behaviours in vivo. This work establishes a blueprint for minimally invasive, transgene-free neuromodulation.

Fundamental investigations of highly crystalline Fe₃O₄ nanoparticles have elucidated the correlation between particle size, crystal domain structure and magnetic coercivity. A critical single-domain threshold near 76 nm maximises coercivity, guiding the design of nanoparticles with optimised magnetic response for biomedical heating or imaging.

Systematic in vitro and in vivo comparisons of iron oxide nanoparticles with different coatings have demonstrated that polyethylene glycol (PEG) and polyethylenimine (PEI) markedly influence cellular uptake, biodistribution, clearance and toxicity. Smaller PEGylated particles achieved superior tumour accumulation with negligible acute toxicity, underscoring the crucial role of surface chemistry in clinical translation.

Magnetic Nanoparticles for Biomedical Applications publication trend

The graph below shows the total number of articles in magnetic nanoparticles for biomedical applications across all publications each year (not limited to Nature Index journals).

Technical terms

Superparamagnetism: A state in which nanoparticles randomly flip their magnetisation under thermal fluctuations, preventing remanent magnetisation once an external field is removed.

Magnetoelectric coupling: The phenomenon in which an applied magnetic field induces an electric potential in a material, enabling remote electrical stimulation via magnetic nanoparticles.

Hyperthermia: Therapeutic heating of tissue by MNPs under an alternating magnetic field to induce cell death in targeted regions, often used in cancer treatment.

Coercivity: The intensity of magnetic field required to reduce the magnetisation of a material to zero, influencing the heating efficiency and stability of MNPs.

Surface functionalisation: Chemical modification of nanoparticle surfaces to impart biocompatibility, targeting capability and colloidal stability in biological media.

References

1. Magnetoelectric nanodiscs enable wireless transgene-free neuromodulation. Nature Nanotechnology (2024).
2. Correlation between particle size/domain structure and magnetic properties of highly crystalline Fe3O4 nanoparticles. Scientific Reports (2017).
3. Uptake, distribution, clearance, and toxicity of iron oxide nanoparticles with different sizes and coatings. Scientific Reports (2018).
4. Comprehensive understanding of magnetic hyperthermia for improving antitumor therapeutic efficacy. Theranostics (2020).
5. Iron Oxide Nanoparticles for Biomedical Applications: A Perspective on Synthesis, Drugs, Antimicrobial Activity, and Toxicity. Antibiotics (2018).
6. Recent progress on magnetic iron oxide nanoparticles: synthesis, surface functional strategies and biomedical applications. Science and Technology of Advanced Materials (2015).