Exchange bias, magnetic fluid hyperthermia, and cellular uptake by endothelial cells in core-shell Fe@Fe3O4 nanoparticles

In this work, a well-defined system of spherical monodispersed superparamagnetic core-shell Fe@Fe
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nanoparticles has been synthesized by a thermal decomposition reaction. Before surface functionalization, the mean particle size was 14.1 nm ± 1.2 nm with a bright shell of a thickness of 1.3 nm ± 0.4 nm. After ligand exchange surface functionalization, the shell thickness has more than doubled to 2.7 nm ± 0.4 nm. The appearance of the Verwey transition TV=125K confirms the presence of magnetite "Fe
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" as a shell around the magnetic core "Fe", which was verified with high-resolution transmission electron microscopy (HRTEM). The exchange bias (EB) associated with exchange anisotropy between the shell and the core has been observed. After incubating the human umbilical vein endothelial cells (HUVEC) with Fe@Fe
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overnight, a complete uptake of the particles at low and high concentrations (50 and 400 µg/ml) was observed. The specific absorption rate (SAR) values of core/shell iron/iron oxide nanoparticles are higher than the conventional iron oxide nanoparticles, which highlights their promising application as heating agents for magnetic fluid hyperthermia.