Green Sol–Gel Synthesis of Iron Oxide Nanoparticles for Magnetic Hyperthermia Applications

Background/Objectives: The unique properties of iron oxide nanoparticles have attracted significant interest within the biomedical community, particularly for magnetic hyperthermia applications. Various synthesis methods have been developed to optimize these nanoparticles. Methods: In this study, we employed a powdered coconut water (PCW)-assisted sol–gel method to produce magnetite nanoparticles for the first time. A comprehensive analysis of the thermal (differential thermal analysis and thermogravimetry), structural (X-ray diffraction), morphological (scanning electron microscopy with energy dispersive spectroscopy), magnetic (vibrating sample magnetometer and hyperthermia), and biological (cytotoxicity essays) properties was conducted to assess their potential for magnetic hyperthermia. Results: Samples heat-treated at 700 °C and 400 °C (washed powder) for 4 h under argon presented only magnetite in their composition. The micrometer-sized particles exhibited ferrimagnetic behavior, with saturation magnetization values of 37, 76, and 10 emu/g and specific absorption rates (SAR) of 27.1, 19.9, and 14.1 W/g, respectively, for treatments at 350 °C (48 h), 700 °C (4 h), and 400 °C (washed powder, 4 h) under an argon atmosphere. Biological tests showed no cytotoxicity below 10 mg/mL. Conclusions: The findings highlight the potential of PCW-assisted synthesis as a sustainable and efficient strategy for producing pure magnetite, with powder washing preceding the heat treatment enabling the attainment of this phase at lower temperatures. Nevertheless, the micrometer-scale dimensions is observed in the morphological analysis limit their suitability for biomedical applications.