Magnetic Fe₃O₄ nanoparticles “decorated” by LAPONITE® nanodisks: a biocompatible nano-hybrid with ultrafast magnetic hyperthermia and MRI contrast agent ability

Journal of Materials Chemistry B, Issue 26, 2022

Read more: https://doi.org/10.1039/D2TB00139J 

NCSR Demokritos | University of Delaware | Khalifa University | Icahn School of Medicine at Mount Sinai | Goodfellow Cambridge Ltd

Researchers have developed a biocompatible nano-hybrid by combining magnetic iron oxide nanoparticles with synthetic clay nanodisks. This material is produced through a straightforward chemical process that ensures the particles remain stable in water without clumping together. Scientific testing confirms that these hybrids excel at generating heat for targeted medical treatments and function effectively as contrast agents for high-quality MRI scans. Crucially, the substance appears non-toxic to human cells, making it a promising candidate for cancer therapy and internal imaging. The study demonstrates that this innovative combination of Fe₃O₄/LAPONITE® nano-hybrid provides a safe and efficient tool for modern biomedical applications.

This research focused on the development of a biocompatible nanohybrid designed for dual use in magnetic hyperthermia (MH) and magnetic resonance imaging (MRI). The researchers successfully materialised superparamagnetic Fe₃O₄ nanoparticles "decorated" with LAPONITE® nanodisks using a facile Schikorr reaction. This synthetic protocol involved the interaction of ferrous hydroxide [Fe(OH)₂] with the synthetic smectite clay LAPONITE.

The nano-hybrid combines superparamagnetic iron oxide (Fe₃O₄) nanoparticles with LAPONITE®, a synthetic clay widely used in biomedical applications. The clay coating stabilises the particles in water (ζ-potential up to −34.1 mV), prevents aggregation, and critically suppresses interparticle magnetic interactions — unlocking exceptional heating efficiency. Under a clinically relevant alternating magnetic field (28 kA m⁻¹, 150 kHz), the optimised formulation achieved a specific absorption rate (SAR) of 540 W gFe⁻¹ raising the temperature of the surrounding solution by 53 °C in under 45 seconds.

In cell studies, the material showed negligible toxicity to healthy tissue yet produced significant cell death in therapy-resistant glioblastoma (GBM) tumour lines when the magnetic field was applied. When delivered directly into the rodent brain, the nanoparticles generated clear, persistent MRI contrast for at least 7 days.

• Unmatched Stability: Using a facile synthetic approach called the Schikorr reaction, the researchers integrated magnetic nanoparticles with diamagnetic clay. This "decoration" gives the particles a high negative zeta potential (−34.1 mV), which prevents them from clumping together and ensures they remain stable in water—a critical requirement for medical use.
• Ultrafast Heat Therapy (Magnetic Hyperthermia): When exposed to a magnetic field, these nanohybrids act as precise heat mediators. They achieved a Specific Absorption Rate (SAR) of 540 W g Fe⁻¹, demonstrating a superior ability to generate the localized heat needed to destroy tumour cells efficiently.
• High-Contrast MRI Imaging: Beyond treatment, these particles excel in diagnostics. In rodent brain studies, the nanohybrids significantly affected T2 relaxation times, causing a distinct signal drop on MRI scans. This allows doctors to clearly track the nanoparticles in vivo, making them potent MRI contrast agents.
• Proven Safety: Biocompatibility is essential for any internal treatment. Toxicity tests on human glioblastoma (brain tumour) cells and human skin fibroblasts showed negligible to no toxicity, confirming that the material is safe for biological applications.

Glioblastoma is notoriously resistant to conventional therapy, and current treatment approaches struggle to act precisely at the tumour site without harming surrounding healthy tissue. Magnetic hyperthermia offers a targeted alternative, but its clinical translation has long been limited by materials that either underperform at safe field frequencies, lack stability in biological environments, or require complex multi-step synthesis that limits scalability.

However, in this study the researchers have successfully engineered a multifunctional nanoplatform that seamlessly integrates therapeutic (hyperthermia) and diagnostic (MRI) capabilities while maintaining a high safety profile and excellent physical stability, with hyperthermia performance among the highest reported for iron oxide nanomaterials at safe, clinically applicable field frequencies.