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Synthesis of Novel PEG-coated Iron Oxide Nanoparticles via Thermal Decomposition Approach

Superparamagnetic nanoparticles (MNPs), showing controllable nanoscale dimensions, biocompatibility, and superior magnetic properties are widely used as magnetic resonance imaging (MRI) contrast agents. As the requirements for biomedical applications of MNPs are closely related to their morphology and magnetism, well-defined sizes and magnetic properties are among the main focuses in the MNPs synthesis. PEG-coated iron oxide nanoparticles were synthesized by high- temperature decomposition of Fe(III) mandelate as organic precursor in poly(ethylene glycol) (PEG, Mr=6, 000) as a solvent and in the presence of poly(ethylene glycol) bis(carboxymethyl) ether (Polyglycol 250 diacid) as a stabilizer. The effects of reaction temperature on the yield, size and morphology of isolated products were investigated by performing synthesis at 300, 320, 340 and 360 °C. Influence of the stabilizer was evaluated by using different concentrations of Polyglycol 250 diacid (8, 16, 24, 32 and 40 mmol). According to Fourier transform infrared spectroscopy (FT IR), PEG coating was obtained at all reaction conditions. Coating thickness increased with increasing concentration of the stabilizer, but not with temperature, as shown by elemental analysis. According to transmission electron micrographs, obtained MNPs were smaller than 30 nm in diameter, while the smallest particles (ca 6 nm) were obtained in the reaction performed at 320 °C in the presence of 40 mmol of Polyglycol 250 diacid. Hydrodynamic particle size according to dynamic light scattering was smallest (ca 165 nm) if the particles were prepared at 300 °C in the absence of Polyglycol 250 diacid.The prepared nanoparticles showed low dispersibility in water and in other solvents, such as toluene, chloroform, isopropanol, oleic acid, tetrahydrofuran, isopropanol, dimethyl sulfoxide (DMSO) and dichlorometane in the presence of surfactants like adipic acid monoethyl ester oleic acid and α-metoxy-ω- carboxy PEG. Thus, it is necessary to further functionalize the prepared MNPs and increase their hydrophilicity prior to their transfer in water media and evaluation of possible in vivo diagnostic applications.

Iron Oxide Nanoparticles; thermal decomposition; synthesis; characterization

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