Functionalization of MnFe$_2$O$_4$ magnetic nanoparticles for biomedical applications in magnetic fluid

The properties of magnetic nanoparticles (MNP) MnFe$_2$O$_4$ synthesized by the polyol method and then functionalized with 3-aminopropyltriethoxysilane (APTES) have been studied. The aim of the work is to create MNCs for magnetic fluid in biomedical applications, in particular for magnetic hyperthermic therapy of malignant tumors. The properties of the obtained particles were studied using X-ray diffraction and Mossbauer spectroscopy, which confirmed the single-phase nature of both MnFe$_2$O$_4$ MNP and functionalized MnFe$_2$O$_4$@APTES composites. From the structural analysis, it was found that the average size of the synthesized particles is $\sim$13 nm, which is consistent with the data of the Messbauro studies. Magnetic and Mossbauer studies have shown that both MnFe$_2$O$_4$ MNPCS and MnFe$_2$O$_4$@APTES composites are superparamagnetic at room temperature. The functionalization (coating) of particles leads to a decrease in the effective magnetic field values compared to those observed in MnFe$_2$O$_4$ without coating, which is consistent with published data on a decrease in the magnetization of the MnFe$_2$O$_4$@APTES composite. The decrease in magnetization and effective fields is explained by the fact that when MnFe$_2$O$_4$ MNP is functionalized, the APTES material covers the surface layer of particles and magnetic dipole interactions decrease.