ИСТИНА

High-quality, 25 nm octahedral-shaped Fe3O4 magnetite nanocrystals are epitaxially grown on 9 nm Au seed nanoparticles (NPs) using a modified wet-chemical synthesis. Detailed studies of the structure and magnetism discover single-crystalline, nanosized Fe3O4 NPs with bulk-like magnetic properties (saturation magnetization of 86 Am2/kg at 300 K close to the bulk value of 92 Am2/kg and a Verwey transition from monoclinic to the cubic inverse spinel structure at T𝑉 = 123 K). For MRI, these features lead to their high T2-relaxivity in in vitro and in vivo experiments. We evaluate an at least doubled relaxivity as compared to the maximum values obtained for Fe3O4 − Au hybrids and a 3-5 times higher value as compared to commercial T2 contrast agents in medical use. Moreover, first experiments on the magnetomechanical action of the hybrid NPs in a low-frequency alternating magnetic field leads to a cell death rate of up to 44% compared to the control.