Magnetic and Hyperthermia Measurements Ultrafast Hyperthermia by Fe3O4 Nano-Assemblies V. Tzitzios1, G. Basina2, C.G. Hadjipanayis3 Abel Frank4 and G.C. Hadjipanayis4 1Institute of Nanoscience and Nanotechnology, NCSR “Demokritos”, Greece 2Department of Chemistry, University of Crete, Voutes 71003 Heraklion, Greece 3Department of Neurosurgery, Emory University School of Medicine 4Department of Physics and Astronomy, University of Delaware Abstract PVP and citrate coated Fe3O4 nano-assemblies in the 30-40 nm size range were synthesized by a modified polyol method. Their structural and magnetic properties were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and magnetometry (VSM) measurements. It is found that the Fe3O4 nano-assemblies show very high heating rate in hyperthermia experiments and therefore are very promising candidates for biomedical applications. All the diffraction peaks can be attributed to Fe3O4 {JCPDS-019-0629} single phases. No signals for other oxides were detected in the XRD pattern. The TEM and HR-TEM images suggest that the nano-assemblies have a flower-like morphology with 30-40 nm mean diameter and consist of 6-8 nm mean diameter isolated Fe3O4 nanoparticles as presented in Figure 2. Room temperature magnetic hysteresis loops presented in Figure 3, show that the Fe3O4 nano-assemblies reveal superparamagnetic behavior and their saturation magnetization is 39 and 57.7 emu/g for the PVP and citrate coated materials, respectively. The difference in the saturation magnetization is probably due to the lower organic content in the case of the citrate modified materials. Introduction Superparamagnetic Fe3O4 nanoparticles continue to emerge as one of the most important nanomaterial for biomedical applications because of its biocompatibility, with applications as MRI contrast agent, thermally activated drug release and heating mediators for hyperthermia cancer treatment.1 In the past few years much work was published on a plethora of synthetic protocols in order to control the size, shape and surface functionality. Among the work focused on magnetic hyperthermia, Jean-Paul Fortin et al.2 reported that the Specific Loss Power (SLP) for isolated Fe3O4 nanoparticles is maximized in the 10-15 nm size range. More recently it was reported that the organization of superparamagnetic isolated Fe3O4 nanoparticles to nano-assemblies increases significantly the SLP values.1, 3 Results show that the 40 nm nano-assemblies (which consisted from 6 nm average diameter isolated Fe3O4 nanoparticles) have a 92.6 W/g SLP with an applied field 10 kA/m at 425 kHz frequency. In this study, we report the fabrication and characterization of Fe3O4 nano-assemblies synthesized by a modified polyol method. Figure 2. (a) Particle morphology as shown by TEM; (b) HRTEM of individual particles. Magnetic and Hyperthermia Measurements Sample Fabrication Synthesis of Fe3O4 nanoparticles was done in a 100 ml spherical flask under reflux conditions. The flask was charged with 20 ml PEG-200 and 500 mg PVP and the temperature was raised to 150 oC under N2 atmosphere. Subsequently, an appropriate amount of Fe(acac)3 was added to the hot mixture via vigorous stirring and the temperature was raised to 200-250 oC and held for 1 h under N2 blanket. Finally, the particles were precipitated by the addition of 50 ml of isopropanol. Precursor injection Gas in thermocouple Oil bubbler Heating mantle septum Figure 3. Hysteresis loops of as-made particles Figure 4. Temperature profiles from hyperthermia The temperature profiles, obtained from hyperthermia measurements in water solution with 10 mg/ml nanomaterial concentration with an 10 kA/m applied field at 150 kHz frequency, (Figure 4) showed an increase in temperature from 293 to 338 K (ΔT=45 K) after only 79 s of field exposure with a very high rate of 0.57 oC/s in the case of citrate functionalized particles while the heating rate is 0.31 oC/s for the PVP coated particles. Conclusions Fe3O4 nano-assemblies can easily be prepared by a modified polyol method. The Fe3O4 nano-assemblies form very stable water colloidal solution with ferrofluid behavior in both PVP and citrate coating. The Fe3O4 nano-assemblies show superparamagnetic behavior and produce very fast heating rate of 0.57 oC/s , under 10 kA/m applied field at 150 kHz. Results The synthesis takes place in poly-ethylene glycol with 200 molecular weight at 220 oC, using Fe lactate as iron source in the presence of poly-vinyl-pyrrolidone (PVP) as morphogenetic and capping agent. The as-made PVP coated Fe3O4 nano-assemblies, after purification by washing with water, were further functionalized by citrate ions in order to increase their water solubility. Figure 1, shows the XRD pattern from the Fe3O4 nanomaterial after the citrate ligand exchange. 1Lartigue L., Alloyeau D., Kolosnjaj-Tabi J., Javed Y., Guardia P., Riedinger A., Péchoux C., Pellegrino T., Wilhelm C., Gazeau F., ACS Nano 2013, 7 (5), pp 3939–3952 2Fortin J-P, Wilhelm C., Servais J., Ménager C., Bacri J-C, Gazeau F., J. Am. Chem. Soc., 2007, 129 (9), pp 2628–2635 3Barickn K.C., Aslam M., Lin Y-P., Bahadur D., Prasad P.V., Dravid V. P., J. Mater. Chem., 2009, 19, 7023-7029. References Acknowledgments National Science Foundation (DMR0302544) Figure 1. X-ray diffraction pattern of as-made particles