Superparamagnetic iron oxide nanoparticles (SPIONs) are the most commonly used inorganic nanoparticles for magnetic hyperthermia in cancer treatment. In this technique, the temperature of the tumor is increased by applying an external alternating magnetic field, which induces heat release from magnetic nanoparticles located at the tumor site. In this study, SPIONs were produced using the chemical co-precipitation technique combined with hydrothermal treatment to reduce their size dispersibility and increase their crystallinity, which are directly related to their magnetic properties. The size of the SPIONs increased from 9 nm to 20 nm after hydrothermal treatment at 160 °C for 24 h. These NPs exhibit a cubic/rectangular shape with a structure composed of both magnetite and maghemite. Their superparamagnetic behavior was confirmed, and the magnetic saturation increased from 58 to 73 emu g⁻¹ at RT and from 67 to 81 emu g⁻¹ at 10 K. Magnetic hyperthermia measurements showed an increase in SAR values from 83 to about 160–200 W g⁻¹, depending on the hydrothermal treatment conditions. Additionally, the exposure of normal and melanoma cells to SPIONs in the presence of an alternating magnetic field leads to a significant reduction in cell viability, with a more pronounced effect in melanoma cells. These results demonstrate the high potential of this synthesis technique for producing SPIONs for cancer treatment via magnetic hyperthermia.

This study aimed to develop multifunctional nanoplatforms for both cancer imaging and therapy using superparamagnetic iron oxide nanoparticles (SPIONs). Two distinct synthetic methods, reduction–precipitation (M_R/P) and co-precipitation at controlled pH (M_pH), were explored, including the assessment of the coating’s influence, namely dextran and gold, on their magnetic properties. These SPIONs were further functionalized with gadolinium to act as dual T1/T2 contrast agents for magnetic resonance imaging (MRI). Parameters such as size, stability, morphology, and magnetic behavior were evaluated by a detailed characterization analysis. To assess their efficacy in imaging and therapy, relaxivity and hyperthermia experiments were performed, respectively. The results revealed that both synthetic methods lead to SPIONs with similar average size, 9 nm. Mössbauer spectroscopy indicated that samples obtained from M_R/P consist of approximately 11–13% of Fe present in magnetite, while samples obtained from M_pH have higher contents of 33–45%. Despite coating and functionalization, all samples exhibited superparamagnetic behavior at room temperature. Hyperthermia experiments showed increased SAR values with higher magnetic field intensity and frequency. Moreover, the relaxivity studies suggested potential dual T1/T2 contrast agent capabilities for the coated SP_pH-Dx-Au-Gd sample, thus demonstrating its potential in cancer diagnosis.