Hybrid nanostructures combining magnetic nanoparticles with metal–organic frameworks (MOFs) represent a promising approach for developing multifunctional platforms for advanced cancer theranostics. In this work, a γ-Fe₂O₃/ZIF-8 composite was synthesized via a stepwise seeded-growth strategy, enabling controlled growth of ZIF-8 onto pre-formed flower-like γ-Fe₂O₃ nanoflowers. X-ray diffraction confirmed the coexistence of both crystalline phases, while electron microscopy and elemental mapping revealed a well-defined hybrid architecture with homogeneous distribution of magnetic and MOF components. Magnetic measurements showed that the composite retains superparamagnetic behavior, with a reduced saturation magnetization (≈30 emu g⁻¹) compared to pure γ-Fe₂O₃ (≈75 emu g⁻¹), attributed to dilution by the non-magnetic ZIF-8 phase. Despite this reduction, the hybrid nanostructure exhibits efficient heat generation under an alternating magnetic field. The specific loss power depends on field amplitude and frequency and deviates from Linear Response Theory predictions, likely due to particle size distribution and magnetic interactions within the nanoflower structure. Importantly, the composite rapidly reaches therapeutically relevant temperatures (42–45 °C), confirming suitability for magnetic hyperthermia. The ZIF-8 component demonstrates excellent radiolabeling capability with the therapeutic radionuclide ¹⁶¹Tb, achieving yields above 94%. The γ-Fe₂O₃/ZIF-8 composite shows similarly high labeling yields (>95%) and outstanding radiochemical stability over 14 days, while pure γ-Fe₂O₃ exhibits significantly lower labeling efficiency (~50%). These results indicate that ZIF-8 plays a crucial role in radionuclide binding. Consequently, γ-Fe₂O₃/ZIF-8 hybrid nanostructures function as a single theranostic carrier integrating magnetic hyperthermia and stable radionuclide delivery, enabling synergistic treatment strategies where hyperthermia enhances therapeutic efficacy of radionuclide therapy.

Acknowledgement

This research was supported by the Science Fund of the Republic of Serbia, Grant No. 7282, Project title "Design of radioactive magnetic nanoconstructs for tumour therapy by synergy of nanobrachytherapy and magnetic hyperthermia" (Acronym: RADIOMAG).