Nanomaterial Endocytosis: Estimation of Particles Per Cell by Magnetic Measurement

We investigated the uptake of superparamagnetic iron oxide nanoparticles (SPIONs) by mammalian cells in monolayer culture by exposing Chinese hamster ovary cells, line CHO-K1 which is frequently used in industrial applications, to Chemicell FluidMagD nanoparticles with diameters of 105 and 150 nm and surface coatings of starch and aminated starch, respectively. The number of particles ingested per cell was determined by measuring the magnetophoretic mobility distributions of treated and untreated cell populations using a Hyperflux magnetic particle tracking velocimeter. Increases in cell volume were evaluated on the basis of cell size data from the Hyperflux velocimeter and used to calculate particles per cell. Starch-coated and positively charged SPIONs were taken up effectively at several concentrations, and these led to quantifiable magnetophoretic mobility and cell volume increases, which, if due to particles only, correspond to several hundred thousand to over one million SPIONs per cell at high SPION feed concentrations. These conclusions are consistent with independent bulk measurements of iron content. Magnetophoretic mobility measurement is a facile and more robust method for measuring SPION uptake.