(131f) Magnetic Nanoparticle Endocytosis Mechanism: Characterization and Quantification By Magnetic Cytometry

Magnetic nanoparticles (MNPs) with varied surface modifications are extensively used in cell labeling, cell purification, cell physiology, endocytosis, biochemical micro assays, endosome research, cell separation, drug targeting, and in vivo diagnostics. The Hyperflux^TM velocimeter uses particle tracking velocimetry to measure magnetophoretic mobility, size and other morphological parameters of magnetic particles and labeled cells. Magnetic cytometry by velocimetry records the motion of labeled cells in an isodynamic magnetic field thereby estimating the key parameter, magnetophoretic mobility of labeled cells. Magnetophoretic mobility is proportional to the number of particles ingested per cell. The rapid estimation of magnetophoretic mobility by the instrument and collection of multiple thousand data points facilitates cellular uptake quantification and kinetic studies in less time than any other existing technique. The receptor-independent uptake by cultured CHO (Chinese Hamster Ovary) cells of 100 nm iron oxide nanoparticles with different surface coatings, namely starch, dextran sulfate (DXS), amino groups, and polyethylene glycol (PEG 2K Daltons), was studied to reveal the role of nanoparticle endocytosis mechanisms. Caveolae-mediated and clathrin-coated endocytosis are revealed by using specific mechanism-based inhibitors such as Genistein and Methyl-β-cyclodextrin. Uptake inhibition has been investigated at different inhibitor concentrations during endocytosis by evaluating the cellular survival rate, toxicity, and uptake of nanoparticles with the different surface coatings, which also reveal relevance of surface charge. Characterization of labeled cells and magnetic particles by magnetic velocimetry facilitates the rapid estimation of intrinsic magnetic properties, the optimization of MNP coatings, a better understanding of cell labeling, and the evaluation of the role of different cellular endocytosis mechanisms.