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Thermally induced oxidative decomposition of iron(II) acetate in air is presented as a simple route towards superparamagnetic maghemite nanoparticles the size of which can be controlled by the reaction temperature in the range of 320-400°C. Decomposition mechanism, the phase composition of the reaction products as well as their structural, magnetic and surface properties were monitored by Mossbauer spectroscopy, XRD, TEM, magnetic and BET surface area measurements. Mossbauer spectra confirm maghemite (gamma-Fe2O3) as the only crystalline decomposition product without any traces of other Fe2O3 polymorphs or magnetite (Fe3O4). On the other hand, the amorphous phase was identified in all samples, which is manifested by the presence of the sextet component with significantly reduced hyperfine magnetic field in the low temperature and in-field Mossbauer spectra. Its content decreases with temperature of synthesis, in accordance with increasing saturation magnetization of the samples. The size of maghemite particles can be controlled by reaction temperature from 4-8 nm at 320 °C to 20-30 nm at 400 °C. This controlled growth is clearly observed by TEM and indirectly demonstrated by narrowing of XRD lines, decreasing surface area (from 147 to 51 m2/g) and increasing blocking and irreversibility temperatures in the FC-ZFC curves. The low intensities of the 2nd and 5th spectral lines in the in-field (5K/5T) Mossbauer spectrum of the sample prepared at 400 °C indicate a low degree of spin frustration of maghemite phase, while the amorphous admixture reveals speromagnetic behavior with unchanged intensities of spectral lines compared to the zero-field spectrum. The sample synthesized at 400 °C exhibits the MRI contrast properties fully comparable with the commercial agent Lumirem as proved by phantom experiments.Key words: Solid-state synthesis, Superaparamagnetic Iron Oxide Nanoparticles, MRI.

Superparamagnetic Iron Oxide Nanoparticles (SPION) are used as an MRI contrast agent for imaging SPION-loaded stem cells in biomedical applications. SPION-labeled stem cells are monitored during the recovery period following transplantation. However, SPION interference within cells has not been clarified to date. We constructed and characterized maghemite nanoparticles, which are biocompatible for a variety of biomedical applications such as MRI contrast agents, fluorescent agents and as magnetic drug delivery carriers. We tested novel SPIO-nanoparticles including a variety of labeling methods suitable for the characterization of cellular behavior. In parallel, we developed an innovative protocol to conjugate antibodies with nanoparticles (AB-nanoparticles) to monitor specific antigen - receptor of desired cells. We quantified SPIO-nanoparticle uptake into cells, cell viability, proliferation and morphology. using our developed protocols, we are able to visualize real-time SPION movement during cell division, redistribution and frequency of cell mitosis. We observed initial endosome formation and the fate of nanoparticles entrapped in endosomes under field emission scanning electron microscopy (FESEM).Key words: stem cells, SPIO, labeling, FESEM, real-time imaging, antibody-conjugated nanoparticlesAcknowledgement: Supported by the European Regional Development Funds (CZ.1.05/2.1.00/03.0058) and KONTAKT II LH12085.View Large Image | View Hi-Res Image | Download PowerPoint Slide