Increasing the biocompatibility, cellular uptake, and magnetic heating performance of ferromagnetic iron-oxide magnetic nanoparticles (F-MNPs) is clearly required to efficiently induce apoptosis of cancer cells by magnetic hyperthermia (MH). Thus, F-MNPs were coated with silica layers of different thicknesses via a reverse microemulsion method, and their morphological, structural, and magnetic properties were evaluated by multiple techniques. The presence of a SiO₂ layer significantly increased the colloidal stability of F-MNPs, which also enhanced their heating performance in water with almost 1000 W/g_Fe as compared to bare F-MNPs. The silica-coated F-MNPs exhibited biocompatibility of up to 250 μg/cm² as assessed by Alamar Blues and Neutral Red assays on two cancer cell lines and one normal cell line. The cancer cells were found to internalize a higher quantity of silica-coated F-MNPs, in large endosomes, dispersed in the cytoplasm or inside lysosomes, and hence were more sensitive to in vitro MH treatment compared to the normal ones. Cellular death of more than 50% of the malignant cells was reached starting at a dose of 31.25 μg/cm² and an amplitude of alternating magnetic field of 30 kA/m at 355 kHz.

Co_1−xZn_xFe₂O₄ nanoparticles (0 ≤ x ≤ 1) have been synthesized via a green sol–gel combustion method. The prepared samples were studied using X-ray diffraction measurements (XRD), transmission electron microscopy (TEM), Raman, and magnetic measurements. All samples were found to be single phases and have a cubic Fd-3m structure. EDS analysis confirmed the presence of cobalt, zinc, iron, and oxygen in all studied samples. Raman spectra clearly show that Zn ions are preferentially located in T sites for low Zn concentrations. Due to their high crystallinity, the nanoparticles show high values of the magnetization, which increases with the Zn content for x < 0.5. The magnetic properties are discussed based on Raman results. Co ferrite doped with 30% of Zn produced the largest SAR values, which increase linearly from 148 to 840 W/g_MNPs as the H is increased from 20 to 60 kA/m.

The combination of magnetic hyperthermia with chemotherapy is considered a promising strategy in cancer therapy due to the synergy between the high temperatures and the chemotherapeutic effects, which can be further developed for targeted and remote-controlled drug release. In this paper we report a simple, rapid, and reproducible method for the preparation of thermosensitive magnetoliposomes (TsMLs) loaded with doxorubicin (DOX), consisting of a lipidic gel formation from a previously obtained water-in-oil microemulsion with fine aqueous droplets containing magnetic nanoparticles (MNPs) dispersed in an organic solution of thermosensitive lipids (transition temperature of ~43 °C), followed by the gel hydration with an aqueous solution of DOX. The obtained thermosensitive magnetoliposomes (TsMLs) were around 300 nm in diameter and exhibited 40% DOX incorporation efficiency. The most suitable MNPs to incorporate into the liposomal aqueous lumen were Zn ferrites, with a very low coercive field at 300 K (7 kA/m) close to the superparamagnetic regime, exhibiting a maximum absorption rate (SAR) of 1130 W/gFe when dispersed in water and 635 W/gFe when confined inside TsMLs. No toxicity of Zn ferrite MNPs or of TsMLs was noticed against the A459 cancer cell line after 48 h incubation over the tested concentration range. The passive release of DOX from the TsMLs after 48h incubation induced a toxicity starting with a dosage level of 62.5 ug/cm². Below this threshold, the subsequent exposure to an alternating magnetic field (20–30 kA/m, 355 kHz) for 30 min drastically reduced the viability of the A459 cells due to the release of incorporated DOX. Our results strongly suggest that TsMLs represent a viable strategy for anticancer therapies using the magnetic field-controlled release of DOX.

Co_0.95R_0.05Fe₂O₄ nanoparticles with R = La, Pr, Nd, Sm, and Eu were synthesized via an environmentally friendly sol–gel method. The prepared samples were studied using X-ray diffraction measurements (XRD), transmission electron microscopy (TEM), X-ray photoelectron microscopy (XPS), and magnetic measurements. All compounds were found to be single phases adopting a cubic Fd-3m structure. EDS analysis confirmed the presence of Co, Fe, R, and oxygen in all cases. The XPS measurements reveal that the Co 2p core-level spectra are characteristic for Co³⁺ ions, as indicated by the 2p_3/2 and 2p_1/2 binding energies and spin–orbit splitting values. The analysis of the Fe 2p core-level spectra reveals the presence of both Fe³⁺ and Fe²⁺ ions in the investigated samples. The doped samples exhibit lower saturation magnetizations than the pristine sample. Very good agreement with the saturation magnetization values was obtained if we assumed that the light rare-earth ions occupy octahedral sites and their magnetic moments align parallel to those of the 3d transition metal ions. The ZFC-FC curves indicate that some nanoparticles remain superparamagnetic, while others exhibit ferrimagnetic ordering at room temperature, suggesting the presence of interparticle interactions. The M_r/M_s ratio at room temperature reflects the dominance of magnetostatic interactions.

The applications of ferrimagnetic nanoparticles (F-MNPs) in magnetic hyperthermia (MH) are restricted by their stabilization in microscale aggregates due to magnetostatic interactions significantly reducing their heating performances. Coating the F-MNPs in a silica layer is expected to significantly reduce the magnetostatic interactions, thereby increasing their heating ability. A new fast, facile, and eco-friendly oil-in-water microemulsion-based method was used for coating Zn_0.4Fe_2.6O₄ F-MNPs in a silica layer within 30 min by using ultrasounds. The silica-coated clusters were characterized by various physicochemical techniques and MH, while cytotoxicity studies, cellular uptake determination, and in vitro MH experiments were performed on normal and malignant cell lines. The average hydrodynamic diameter of silica-coated clusters was approximately 145 nm, displaying a high heating performance (up to 2600 W/g_Fe). Biocompatibility up to 250 μg/cm² (0.8 mg/mL) was recorded by Alamar Blue and Neutral Red assays. The silica-coating increases the cellular uptake of Zn_0.4Fe_2.6O₄ clusters up to three times and significantly improves their intracellular MH performances. A 90% drop in cellular viability was recorded after 30 min of MH treatment (20 kA/m, 355 kHz) for a dosage level of 62.5 μg/cm² (0.2 mg/mL), while normal cells were more resilient to MH treatment.

We report the successful synthesis and a complete magnetic characterization of CoFe₂O₄@SiO₂@Au magnetoplasmonic nanoparticles. The CoFe₂O₄ magnetic nanoparticles were prepared using the hydrothermal method. A subsequent SiO₂ shell followed by a plasmonic Au shell were deposited on the magnetic core creating magnetoplasmonic nanoparticles with a core–shell architecture. A spin-glass-type magnetism was shown at the surface of the CoFe₂O₄ nanograins. Depending on the external magnetic field, two types of spin-glass were identified and analyzed in correlation with the exchange field acting on octahedral and tetrahedral iron sites. The magnetization per formula unit of the CoFe₂O₄ core is not changed in the case of CoFe₂O₄@SiO₂@Au nanocomposites. The gold nanoparticles creating the plasmonic shell show a giant diamagnetic susceptibility, dependent on their crystallite sizes.