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.

A new tool to attack biofilms: driving magnetic iron-oxide nanoparticles to disrupt the matrix

A main feature of biofilms is the self-produced extracellular polymeric substances (EPSs) that act as a protective shield, preventing biocide penetration. We use magnetic iron oxide nanoparticles (MNPs) in combination with magnetic fields to damage the biofilm matrix and cause detachment. A Methicillin-resistant Staphylococcus aureus (MRSA) biofilm strain is used to demonstrate the efficacy of the methodology with different sizes and concentrations of MNPs under AC and DC applied field conditions. We achieve up to a nearly 5 log10 reduction in biofilm bacteria after treatment with 30 mg mL-1 of 11 nm MNPs using a magnetic field. The MNPs cause significant mechanical disruption to the matrix and lead to biofilm dispersal. In addition, using magnetic hyperthermia further affects biofilm damage.

Simple, Hackable, Size-Selective, Amine-Functionalized Fe-Oxide Nanoparticles for Biomedical Applications

A facile one-pot method for synthesizing amine-functionalized nonspherical Fe₃O₄ nanoparticles in gram-scale quantities is presented using just a single source of iron (iron(II) chloride) and an amine (triethylamine). The amine not only transforms iron salt to Fe₃O₄, but also directs the morphology of the nanoparticles along with the temperature of the reaction and functionalizes them, making the synthesis very economical. By modifying the surface further, these nanoparticles promise to offer useful biomedical applications. For example, after biocide coating, the particles are found to be 100% effective in deactivating methicillin-resistant Staphylococcus aureus (MRSA) bacteria in 2 h. Cellular-uptake studies using biocompatible EDTA-Na₃ (N-(trimethoxysilyl-propyl)ethylenediaminetriacetate, trisodium salt)-coated nanoparticles in human glioblastoma U-251 cells show that the majority of the particles are internalized by the cells in the presence of a small dc-magnetic field, making these particles a potential candidate as drug carriers for magnetic field-targeted delivery and hyperthermia.