(726a) Nanoparticle Phagocytosis: Characterization and Quantification By Magnetic Cytometry

Nanoparticle characterization is of importance and in high demand in medical biology research and clinical application. The uptake by cultured CHO (Chinese hamster ovary) cells of 50 and 100nm iron oxide particles (MNPs) coated with starch, aminated starch and PEG (2K, 5k and 20k Daltons) was studied to reveal the chemistry of nanoparticle phagocytosis. A particle tracking velocimeter, Hyperflux^TM was utilized to directly measure the magnetophoretic mobility, size and other morphological parameters of magnetic nanoparticles and labeled cells. The magnetophoretic mobility is a key parameter to describe the cell motion in a defined magnetic field and is used as a quantitative indicator of the number of particles ingested per cell. By quantitatively characterizing and determining the cell uptake kinetics as a function of particle size and surface chemistry, we have been able to reveal the dependencies of phagocytosis on cell type, incubation time, particle composition, particle size and particle toxicity. We found that surface aminated nanoparticles, which are highly positively charged, are more effectively taken up by CHO cells than starch-coated particles or uncoated particles. The PEG content in coating, though bio-friendly, will prevent the penetration of MNPs into CHO cells. In addition, the Hyperflux Velocimeter analysis provides a better understanding of cell labeling and as a tool to optimize setting of MNPs type and incubation condition.

Key Words: magnetic particles, nanoparticles, magnetophoretic mobility, phagocytosis, CHO cells, particle tracking velocimetry