# Application in Nanomedicine of Manganese-Zinc Ferrite Nanoparticles
## 3 In Vitro Applications of Mn-Zn Ferrites  
In this section, some recent studies, in which manganese-zinc ferrite nanoparticles have been tested within in vitro experiments, are analyzed. In the selection of relevantcontributions, some aspects were considered, such as the effective enhancement of the magnetic properties (e.g., magnetic saturation or \(r_{2}\) relaxivity or SAR value), that justified the use of a doped ferrite in alternative to bare iron oxide nanoparticles, and the application of these nanoparticles in an in vitro assay, with particular consideration of the biocompatibility of the nanomaterial.  
[PERSON] et al. presented a study on the synthesis of Mn\({}_{\mathrm{x}}\)Zn\({}_{1-\mathrm{x}}\)Fe\({}_{2}\)O\({}_{4}\) ferrite nanoparticles with a size of around 8 nm. For these nanoparticles, obtained by thermal decomposition, the ratio between Zn and Mn was inversely varied, finding Mn\({}_{0.6}\)Zn\({}_{0.4}\)Fe\({}_{2}\)O\({}_{4}\) as the best composition in terms of Ms (76.7 emu/g). These nanoparticles were then transferred in the aqueous phase through the use of a synthetic amphiphilic block copolymer obtained from mPEG and poly(caprolactone) (PEG-PLC), obtaining ultra-stable clusters of about 100-150 nm. The size of these clusters and their magnetization were modulated by varying the mass ratios between the particles and polymer. In terms of magnetic hyperthermia, however, it was noted that the ferrites obtained with Mn only show a higher SAR (1618 W/g) than Mn\({}_{0.6}\)Zn\({}_{0.4}\)Fe\({}_{2}\)O\({}_{4}\) (1100 W/g). From the experiments conducted on MCF-7 and drug-resisive MCF-7/ADR cancer cells in vitro, it can been seen that the application of magnetic hyperthermia generated high levels of cellular depletion of up to 90% within 15 min, obtained mainly by induction of apoptotic and non-necrotic phenomena [41].  
In addition, in the work of [PERSON] et al. the Mn-Zn ferrite nanoparticles were synthesized by thermal decomposition, obtaining monodisperse nanoparticles of 10 nm, with a quasi-cubic morphology. In addition to a good \(r_{2}\) relaxivity and an excellent biocompatibility (with cytotoxicity of 10% at the highest tested concentration and a hemolysis rate of 1.12%), these ferrites showed a very high magnetic saturation, equal to 98 emu/g. These nanoparticles were then investigated as a potential actuator for magnetic hyperthermia, obtaining an increase in temperature of up to 42-44 \({}^{\circ}\)C within 20 min, at 235 kHz, with a particularly low concentration of 60 \(\mathrm{\SIUnitSymbolMicro g}\)/mL. In addition, the nanoparticles were evaluated as carriers for gene therapy, assessing the ability to transfer CD44-shRNA-EGFP plasmids into the ovarian cancer SK-OV-3 cells, obtaining a transfection efficiency of 58%, which is comparable to the standard liposome method [42].  
Applying a different synthetic method, [PERSON] et al. reported the preparation of manganese-zinc ferrite nanoparticles that were obtained by a hydrothermal route, obtaining particles with a TEM diameter of approximately 14 nm and a hydrodynamic diameter of approximately 400 nm. These particles, stabilized with a PEG outer layer, showed a higher relaxivity \(r_{2}\), 85 mM\({}^{-1}\) s\({}^{-1}\) compared to the commercial equivalent (Sinerem). Taking into account a low-mild cytotoxicity, two different cell lineages, 4T1 and L929 cells, were incubated and then analyzed by MRI to evaluate the T\({}_{2}\) signal decrease, obtaining a decrease of signal intensity in T\({}_{2}\)-weighted images, of 25% at an iron concentration of 0.4 mg/mL and 45% at a concentration of 0.8 mg/mL [43].