ИСТИНА

421 Colloidal stability and bioactivity of Fe3O4 nanoparticles functionalized with humics and silica T. Kuznetsova, National University of Science and Technology MISIS; L. Bondarenko, Moscow Aviation Institute; P. Uchanov, Institute of Ecology and Evolution RAS / Laboratory for soil ecological functions; A. Sybachin, Lomonosov Moscow State University; V. Terekhova, Lomonosov Moscow State University / Lab of Ecotoxicological Soil Analysis; K. Kydralieva, Moscow Aviation Institute. Investigations of Fe3O4 nanoparticles (NPs) functionalized by different inorganic and organic ligands are being increasingly reported in the literature due to the importance for biomedical and ecological applications. The huge diversity of polymers allows for different types of Fe3O4 NPs surface functionalization, i.e., introduces charges on the system that can prevent the aggregation of the particles in liquids and improve their chemical stability through surface charge control. In addition to studying the size, structure and composition of the colloidal particles, control of their colloidal stability is very important. Controlling the stability of the magnetic fluids against aggregation is important because the formation of aggregates alters their specific surface area and dispersibility as well as their bioactivity. In the present work, the influence of humic acids (HA) and/or silanes (tetraethoxysilane, TEOS and 3-amino propyl-triethoxysilane, APTES) was studied and correlated with the colloidal stability and bioactivity. The control of the functionalization nature and density (number of layers) on the Fe3O4 surface was investigated, electrokinetic measurements (zeta-potential and hydrodynamic diameter), bioactivity analysis were performed. The higher plant ? whitemustard Sinapis alba L., green algae Scenedesmus quadricauda (Turb.) Brev., and infusorians P?ramecium caudatum were used as test organisms for bioactivity evaluation. The results suggest that surface charge and bioactivity can be controlled by grafting Fe3O4 NPs with HA and/or silanes. The sequential layer-by-layer grafting of precursors onto the NPs surface demonstrated an logical increase in the hydrodynamic diameter (measured by dynamic light scattering) in the row: Fe3O4/TEOS<Fe3O4 /TEOS/APTES< Fe3O4/TEOS/APTES/HA. Zeta potential for silica grafted NPs varied considerably with layering from -20 mV (Fe3O4/TEOS) to -0.6 mV (Fe3O4/TEOS/APTES), which correlates with surface charge provided by the surface amino group of APTES. For the Fe3O4coated by HA zeta-potential increased from 15 mV (bare Fe3O4 ) to -40 mV (Fe3O4/HA). The bioactivity of bare and functionalized NPs by silica and/or HA with respect to test-organisms demonstrated higher toxicity for multilayered nanoparticles asFe3O4 /TEOS/APTES/HA in compare with Fe3O4/HA. Acknowledgement. This research has been financed by the Russian Foundation for Basic Research (#18-33-01270/18) and the Russian Science Foundation (#16-14-00167).