Biodegradation of Magnetic Nanoparticles in Rat Brain Studied by Mössbauer Spectroscopy

Superparamagnetic particles of Fe₃O₄ in ferrofluid were injected transcranially in the ventricle of the rat brain. At three months after the injection the rat was sacrificed and the brain was investigated by Mössbauer spectroscopy and histological Perls Prussian blue method. Histological examination demonstrated increased concentration of blue areas in parenchyma and on the dura mater of the brain of experimental rat in comparison with the brain of control rat, indicating appearance in the brain of some undegradable compound of iron. Mössbauer spectra showed the presence in the ferrofluid of both Fe₃O₄ nanoparticles and an additional chemical compound which contains ferric iron in the high-spin state. Comparison of the Mössbauer spectra of the ferrofluid, of the brain before injection and of the brain three months after injection shows that the Fe₃O₄ nanoparticles were removed from the brain in three months. At the same time this additional chemical compound does not decompose and remains in the brain intact.