A Fast, Reliable Oil-In-Water Microemulsion Procedure for Silica Coating of Ferromagnetic Zn Ferrite Nanoparticles Capable of Inducing Cancer Cell Death In Vitro

Abstract

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 Zn0.4Fe2.6O4 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/gFe). 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 Zn0.4Fe2.6O4 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.

Enhanced Magnetic Hyperthermia Performance of Zinc Ferrite Nanoparticles under a Parallel and a Transverse Bias DC Magnetic Field

“…It is also important to mention that recently, it was demonstrated that core-shell ferrite MNPs with a shell doped with Zn, exhibit an unusually high SAR [ 14 ]. As reported previously [ 34 ], these Zn ferrite MNPs exhibit very high SAR values, above 3 kW/g Fe , and are also nontoxic for both normal BJ and A459 cancer cell lines, up to a concentration of 0.8 mg/mL [ 35 ].…”

“…The zinc ferrite NPs were synthesized following a thermal decomposition method of the acetylacetonate precursors [ 34 ]. The detailed synthesis method and the physicochemical characterization techniques as, transmission electron microscopy (TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), Fourier transform infra-red spectroscopy (FTIR), and vibrating sample magnetometry (VSM) are presented in our previous paper [ 35 ]. Briefly, the as-synthesized MNPs have faceted shapes (some are cubic, others polyhedral) with the main size of 28 ± 0.2 nm and a good polydispersity index which was very close to the average crystalline size (27 nm), calculated using Scherrer’s formula by the Gaussian fit of the prominent X-ray diffraction peaks ( Figure S1 ) [ 35 ].…”

“…The energy-dispersive X-ray (EDX) maps show that the Fe and Zn elements are homogeneously distributed within the total volume. At the same time, the quantitative analysis of the EDX spectra revealed a mean value of the Zn atomic percentage around 0.4, i.e., the Zn ferrites correspond to the formula Zn 0.4 Fe 2.6 O 4 ( Figure S1 ) [ 35 ]. The M s is around 100 emu/g at 4 K and decreases to 73 emu/g at room temperature (RT), this decrease being consistent with the literature and can be attributed to the increased spin-disorders in the surface layers of the smaller MNPs [ 36 ].…”

“…The M s is around 100 emu/g at 4 K and decreases to 73 emu/g at room temperature (RT), this decrease being consistent with the literature and can be attributed to the increased spin-disorders in the surface layers of the smaller MNPs [ 36 ]. The Zn ferrites preserve the ferromagnetic character at RT, as the coercive field (H c ) slightly decreases from 29 mT (24 kA/m) to 19 mT (15 kA/m) by increasing the temperature from 4 K to RT ( Figure S1 ) [ 35 ]. The oxidation of the oleic acid by sodium periodate induces Zn ferrites a zeta potential of −52 mV, due to the resulting carboxyl groups [ 37 ], enabling a good colloidal stability.…”

“…The oxidation of the oleic acid by sodium periodate induces Zn ferrites a zeta potential of −52 mV, due to the resulting carboxyl groups [ 37 ], enabling a good colloidal stability. However, according to the DLS data, the ferromagnetic Zn ferrites have a mean hydrodynamic diameter of 70 nm in water, signifying that they stabilize in an aqueous solution in very small clusters [ 35 ]. The main physical parameters obtained from the physicochemical characterization relevant to the current study are summarized in Table 1 .…”