The relationship between internalization of magnetic nanoparticles and changes of cellular optical scatter signal.

Carboxylmethyl starch sodium-coated magnetic nanoparticles (CMS@MNs) with average size of 10 nm were synthesized by chemical coprecipitation. Cellular iron content showed that CMS@MNs could be efficiently uptaken by human hepatoma cells. TEM image showed that clusters consisting of nanoparticles were enclosed within sub-micrometric endosomes and one cell contained several such endosomes. After incubation with the nanoparticles, a phenomenon appeared that the intensity of cellular side scatter signal (SSC) obtained by flow cytometry at 488 nm argon laser increased. It was demonstrated that the increase of SSC signal was induced by a cell itself, and mainly caused by the nanoparticles both adsorbed on the membrane and internalized into cytoplasm. Although without inducing cell death the treatments with the nanoparticles could lead to increased permeability of cell membrane to propidium iodide. Results implied a potential that flow cytometry might be used as a tool to rapidly evaluate and select cells with high magnetic labeling and high viability in cellular transplant.