(373c) Magnetic Nanomaterial Endocytosis: Uptake and Cytotoxicity

Magnetic nanomaterials have found recent popularity in endocytosis, cell separation, drug delivery, tumor targeting, biomedical imaging, and in vivo diagnostics. Endocytosis (internalization by cells) of magnetic nanoparticles is of fundamental importance to a broad range of biomedical applications depending on the nanoparticle size, shape, surface functionalization, and magnetic properties. Magnetic cytometry captures the motion of labeled cells in an isodynamic magnetic field to estimate the magnetophoretic mobility of labeled cells. Magnetophoretic mobility is proportional to the number of beads ingested per cell. Using magnetic cytometry, it is possible to estimate the number of particles ingested by each cell within populations of thousands of cells. We employed a Hyperflux^TM particle tracking velocimeter to measure magnetophoretic mobility of CHO cells in monolayer culture ingesting 50 nm and 100 nm magnetic beads (fluidMAG^TM, Chemicell) with different surface coatings. In addition to uptake data, cell loss and viability data are available in the course of endocytosis studies by this method. Reduction in cell number is correlated with the level of cellular uptake. Positively charged beads resulted in the highest level of uptake and the greatest reduction in cell number, while PEG-coated beads were the least ingested and the least toxic. Maximum cell losses observed were 50% on day 1 and 65% on day 2 of incubation at the highest concentration of beads studied corresponding to 200 μg of iron/mL. The viability of cells that survived processing was evaluated by viability staining methods, including flow cytometry. In most cases, >80% of cells were viable after one day of exposure to 100 μg of iron/mL by staining criteria. The results in general follow a previously found rule that cell loss is proportional to magnetic nanomaterial uptake, and this principle can guide the use of nanomaterials in biomedical applications.