Gadolinium-doped iron oxide nanoflowers as dual modality agents for magnetic hyperthermia and MRI

Recent advances in nanoparticle synthesis have shown that clusters of iron oxide nanoparticles have enhanced magnetic properties compared to individual spherical nanoparticles. Iron oxide nanoflowers (IONFs) show promise for applications in magnetic hyperthermia and magnetic resonance imaging (MRI) due to their stronger interparticle interactions compared to separated or dispersed spherical nanoparticle systems. In this study, we produced both undoped IONFs and gadolinium-doped iron oxide nanoflowers (Gd-IONFs) through the introduction of a small amount of gadolinium acetylacetonate during the thermal decomposition reaction. Transmission electron microscopy (TEM) revealed similarly sized ∼ 42 nm clusters for both the nanoflower sets. Magnetometry measurements showed a moderate decrease in saturation magnetization upon doping the nanoflowers with gadolinium. The IONFs and Gd-IONFs exhibited excellent performance for magnetic hyperthermia under hyperthermia relevant fields and frequencies of 200 kHz and 20 kA m^-1, with AC magnetometric specific absorption rate (SAR) values of 417± 9.9 W g_Fe^-1 and 466 ± 4.4 W g_Fe+Gd^-1, respectively. MRI measurements showed a decrease in transverse relaxivity r₂ from 570 ± 23 L mmol^-1 s^-1 to 560 ± 6 L mmol^-1 s^-1 upon the addition of gadolinium. Similarly, a decrease in longitudinal relaxivity r₁ from 2.6 ± 0.2 L mmol^-1 s^-1 to 2.3 ± 0.1 L mmol^-1 s^-1 occurred through the incorporation of gadolinium. Overall, this work demonstrates that low-level Gd incorporation preserves the excellent magnetic hyperthermia performance of iron oxide nanoflowers while enabling their development as a multifunctional platform for combined magnetic hyperthermia and MRI applications.