Intracytoplasmic tagging of cells with ferumoxides and transfection agent for cellular magnetic reisonance imaging after cell transplantation: Methods and techniques

Background. Superparamagnetic iron oxides (SPIO) are being us ad to label cells for in vivo monitoring by magnetic resonance imaging (MRI). The purpose of this study if; to present protocols using SPIO and a polycationic transfection agent for magnetic labeling of cells as a basis for cellular MRI. Methods. Various concentrations of ferumoxides (FE)-poly-L-lysine (PLL) complexes were used to magnetically label cells. Iron incorporation into cells along with c all viability and short- and long-term toxicity were evaluated. Results. Rapidly growing cell suspension and adherent cells were effectively labeled by means of endocytosis into endosomes at low concentrations of FE (25 mug/mL media) and PLL (0.75 mug/mL media). Hematopoietic stem cells and lymphocytes required higher concentrations of PLL (1.5 mug/mL) in serum-free media during initial FE-PLL complex formation before labeling the cells: in culture. Total iron concentration in cells depended on the cell type, concentration of FE-PLL complexes in media, cellular density, and incubation time. Iron concentrations after overnight incubation with given FE at 25 mug/ml, media resulted in, for example, T cells being labeled with 1 to 3 pg/cell of intracytoplasmic endosomal iron and 15 to 20 pg/cell of intracytoplasmic iron in mesenchymal stem cells compared with 0.01 to 0.1 pg/cell for unlabeled cells. Protocols developed for this study demonstrated no adverse effect on the cell viability, functional capacity, or toxicity. Conclusion: This technique can be used to label cells for in vivo MRI tracking of stem cells and lymphocytes. FE at a concentration of 25 to 50 mug/ml, with a ratio of SPIO to PLL of 1:0.03 to 1:0.06 would be sufficient to label cells for cellular MRI.