Determination of Limits for Evaluating the Degree of Internalization of γ-Fe₂O₃ Nanoparticles by Cultures of Human Mesenchymal Stomal Cells

A culture of human bone marrow mesenchymal stromal cells (MSCs) has been investigated. The cell culture has been grown as a monolayer in a nutrient medium containing a stabilized aqueous suspension of magnetic maghemite (γ-Fe₂O₃) nanoparticles (MNPs). The MNPs have been synthesized by the electrophysical method of laser target evaporation. A method has been proposed for stabilizing the suspension in the nutrient medium with a high ionic strength. The possibility of MNP internalization (either by fixing on the cell membrane or by incorporating into the cell space) with human MSCs has been evaluated using optical microscopy, scanning (SEM) and transmission (TEM) electron microscopy, and SQUID magnetometry. Comparative analysis of the structure and magnetic properties has been performed, and assumptions have been put forward about the features of MNP internalization with the cells in this system. It has been revealed that the limiting amount of MNPs that can be reliably analyzed in a biological sample of the studied type is about 0.005 mg. It has been found that, in the considered range of initial concentrations of magnetic nanoparticles in biological samples based on human MSCs, the level of accumulation of magnetic nanoparticles in cell cultures depends on their concentration.