Synthesis of highly hydrophilic magnetic nanoparticles of Fe3O4 for potential use in biologic systems

Nanoparticles of Fe3O4 with enhanced hydrophilic properties were synthesized using a co-precipitation approach of Fe2+ and Fe3+ ions in a basified aqueous solution followed by a surface treatment. Two surfacing strategies, using a two-step approach, were used to coat synthesized nanoparticles with silanes of different functional groups for further treatment with ethylenediamine: (i) Michael addition and (ii) nucleophilic addition. Wide-angle X-ray diffraction (WAXD) revealed the pristine nanoparticles with 6.3  nm of diameter. Before the surface treatment with ethylenediamine, stirred suspensions of silanized nanoparticles in water showed segregation after a few minutes in repose. On the other hand, the suspensions of nanoparticles silanized and functionalized with ethylenediamine became homogenous and translucent in water. The advantage of the developed nanoparticles is that (because of their high hydrophilicity) they could interact with biological species such as enzymes, proteins, aminoacids and DNA.

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► Nanoparticles of Fe3O4 with enhanced hydrophilic properties were synthesized.
► A strategy was developed to coat silanized nanoparticles with ethylenediamine.
► Aqueous suspensions of nanoparticles without ethylenediamine showed segregation.
► Aqueous suspensions of ethylenediamine-coated nanoparticles are stables.
► The forces that maintain the particles suspended in water are hydrogen bonds.