Characterization and Quantification of Magnetic Particles and Magnetically Labeled Cells by Magnetic Cytometry

Abstract

Characterization of magnetic particles and labeled cells is in high demand in both medical research and clinical applications. A HyperfluxTM Velocimeter is utilized to directly measure the magnetophoretic mobility, size and other morphology parameters of magnetic particles and labeled cells. The magnetophoretic mobility analysis provides a better understanding and quality control of particles samples, serves as a key parameter in describing cell motion in a defined magnetic field and quantitatively determines the number of particles ingested per cell. The Chinese hamster ovary (CHO-K1) cells were exposed in monolayer culture to approximated 50 and 100 nm iron oxide nanoparticles coated with starch, surface amine groups and polyethylene glycol (PEG) to study the chemistry of phagocytosis. Kinetic and dynamic studies were performed with varying incubation times and particle concentrations. At the conclusion of each exposure, cells were harvested into single-cell suspensions, and particle uptake was quantified by magnetic cytometry. By quantitatively determining the magnetophoretic mobility which is proportional to particle uptake per cell as measured by flow cytometry and by chemical analysis, the dependencies of phagocytosis on cell type, incubation time, particle composition, particle size and particle toxicity were determined. Particle uptake of surface aminated particles by CHO cells is larger than either starch-coated particles or uncoated particles. Amination of starch particles increased the positive zeta potential and cellular uptake. In contrast, PEGylation of aminated starch particles decreased the positive zeta potential and drastically reduced cellular uptake. Magnetic cytometry can accurately measure properties of magnetic particles and labeled cells. Velocimetry analysis reveals that SPION surface charges and composition profoundly affect their uptake by cells in vitro. The labeled cell system can be optimized for special applications by controlling labeling conditions.