Paper Title
Surface Study of Fe3O4 Nanoparticles Functionalised with Biocompatible Adsorbed Molecules

Abstract
Surfaces of iron oxide of ferrimagnetic magnetite (Fe3O4) nanoparticles (MNPs) prepared by Massart’s method and their functionalised form (f-MNPs) with succinic acid ((CH2)2(CO2H)2), L-arginine (C6H14N4), oxalic acid (C2H2O4), citric acid (C6H8O7) and glutamic acid (C5H9O4N) were studied by X-ray photoelectron spectroscopy (XPS) and reflection electron energy loss spectroscopy (REELS). The biocompatibility of these f-MNPs was tested on L929 and HeLa cells. The XPS analysis of chemical states and amount of C, O, Fe, N and Cl and S containing contaminations at the surface of MNPs and f-MNPs revealed differences in chemical bonding of atoms and content of carbon-oxygen groups, iron oxide forms, iron oxide magnetic properties, adsorbed molecules surface coverage, overlayer thickness, electronic and optical properties influencing the biological properties of these surfaces. The surfaces showed no remarkable changes in biocompatibility on L929 cells, whereas the cytotoxicity on HeLa cells was the highest for MNPs functionalised with oxalic acid. Although, differences in efficacy of f-MNPs on HeLa cells treatment were not extensive (10.8-5.3% of cell death), it seems that the most efficient f-MNPs were characterised by the smallest surface coverage and overlayer thickness of functionalising adsorbed molecules, high number of C sp3 hybridisations, the highest content of oxygen groups, C-N groups, lattice and adsorbed O2- and OH- chemical forms from Fe3O4 and FeOOH with respect to C sp2 and electronic and optical properties closest to those of Fe3O4 MNPs. The Auger parameters (derived from XPS and Auger spectra), elastic and inelastic scattering probabilities of electrons on atoms and valence band electrons (derived from REELS spectra) indicating modification of surface electronic charge redistribution, electronic and optical properties due to surface functionalisation justify various biological behaviour of the investigated f-MNPs on HeLa cells.