Detection of Magnetosome-Like Structures in Eukaryotic Cells Using Nonlinear Longitudinal Response to ac Field

Although magnetosomes have been discovered in bacteria since several decades, until today the question remains open whether such biomineralized structures do exist in eukaryotic cells. Herein, evidence was provided for the existence of magnetosome-like Fe-based structures in different viable eukaryotic cells by the registration of second harmonic of magnetization M2(H) of longitudinal nonlinear response to weak ac field. The behavior of the field hysteresis of the M2 response from cells in suspension and/or in pellet indicated a multi-domain state of magnetosome-like structures in certain type of cells, and a single-domain state in other cell lines. The amounts of magnetosomes in cells range from ≤ 1÷2 to 5÷8 per cell. The presence of magnetosome-like structures was analyzed in normal tissue samples obtained from Wistar rats and C57/Bl6 mice. Additionally, the tumor tissue (orthotopic rat C6 glioma and mouse GL261 glioma) were assessed for magnetosomes. Detected magnetosomes in certain tissues (i.e., brain, heart, lungs) matched to a single-domain magnetite nanoparticle, whereas in other organs they exhibited characteristics attributable to a multi-domain state, better corresponding to Fe(0) composition of their magnetic cores. Subsequent studies are necessary to elucidate the role of the Fe-based magnetosome-like structures in the biology and physiology of eukaryotic cells.