Facet-dependent magnetic properties of magnetite nanoparticles coated with dodecyl amine and their biological effect in hepatocarcinoma cell line

Abstract

Herein was conducted a compelling structural analysis of magnetite nanoparticles (NPs) coated with dodecyl amine (DDA), compared with uncoated magnetite, both previously synthesized by an accelerated one-pot synthesis, starting from a single iron precursor. XRD/TEM results for the obtained nanomaterial Fe3O4@DDA showed the predominance of Fe3+ cations on the most stable atomic plane of magnetite (111). Using Molecular Dynamics calculations, with the observed atomic dispositions as inputs, it was established that NPs' surface and DDA might interact by short-distance coordination, with DDA as a ligand of Fe3+ cations, or by long-distance adsorption via H-bonding. The simulations align with TEM images, revealing an amorphous contour corresponding to the organic coating arranged as a bilayer. The TGA analysis corroborated a dual mass loss profile relating to the DDA bilayer at 116 °C and 350 °C. The Fe3O4@DDA NPs’ magnetic properties (saturation magnetization (Ms) and coercivity field (Hc)) were preserved. Fe3O4@DDA exhibited a reduction of 3 emu/g in Ms and an increment of 12 Oe in Hc, compared with Fe3O4 NPs, attributable to the coating inhomogeneity and the consequent anisotropy rise. Fe3O4@DDA triggered concentration-dependent cytotoxic effects on the human hepatocarcinoma cell line HepG2. At 50 µg/mL after incubation of 48 h, cell viability was 63% < , whereas at 72 h only 30% of cells were viable. At 300 µg/mL, less than 10% of HepG2 cells remained viable after 24 h of incubation. In the case of Fe3O4 NPs assessed in the same cell line, cell viability remained as high as 80% at 300 µg/mL during 72 h of incubation. Trypan blue assay suggests membrane integrity damage as the primary mechanism of HepG2 cell death. Even though the in vitro results herein presented are preliminary, they represent the first report of the cytotoxic effect of magnetite coated with a nitrogenous surfactant.Graphical abstract