EDTA-Na₃ functionalized Fe₃O₄ nanoparticles: grafting density control for MRSA eradication

We report a synthesis strategy to simplify often cumbersome post-synthesis ligand exchange protocols and use that approach to synthesize EDTA-Na3 (N-(trimethoxysilylpropyl)ethylenediaminetriacetate, trisodium salt) functionalized hydrophilic and biocompatible Fe3O4 nanoparticles. The grafting density of EDTA-Na3 has been controlled from 0.07-0.37 μmol m-2 by varying the time at which EDTA-Na3 was added to the reaction. The success of EDTA-Na3 surface functionalization has been verified using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Mössbauer spectroscopy techniques. Mössbauer spectroscopy results showed the evidence of Fe-EDTA monomer and dimer formation signifying covalent bonding between Fe ions and EDTA-Na3. The earliest addition of EDTA-Na3 resulted in the most stable dispersion of nanoparticles in water and phosphate buffered saline (PBS) which remained stable for more than a month. In addition, our results suggest that these nanoparticles can have useful applications in magnetic hyperthermia and eradication of methicillin-resistant Staphylococcus aureus (MRSA) bacteria in presence of an ac magnetic field.