Preparation of Magnetic Iron Oxide Nanoparticles (MIONs) with Improved Saturation Magnetization Using Multifunctional Polymer Ligand

This paper describes the preparation of ultra-small magnetic iron oxide (Fe3O4) nanoparticles (MIONs) coated with water-soluble thioether end-functionalized polymer ligand pentaerythritol tetrakis 3-mercaptopropionate-polymethacrylic acid (PTMP-PMAA). The MIONs were prepared by co-precipitation of aqueous iron precursor solution at a high temperature. The polymer modified MIONs were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and vibrating sample magnetometery (VSM). It was found that these MIONs were successfully modified by this water-soluble polymer ligand with a fairly uniform size and narrow size distribution. The dried powder of MIONs could be stored for a long time and re-dispersed well in water without any significant change. Additionally, the polymer concentration showed a significant effect on size and magnetic properties of the MIONs. The saturation magnetization was increased by optimizing the polymer concentration. Furthermore, the 3-(4,5-dimethylthiazol-2-yl)-2-5-diphenyltetrazolium bromide (MTT)-assay demonstrated that these MIONs were highly biocompatible and they could be successfully coupled with fluorescent dye Rhodamine due to the formation of amide bond between carboxylic acid groups of MIONs and amine groups of dye. The obtained results indicated that these multifunctional MIONs with rich surface chemistry exhibit admirable potential in biomedical applications.