Cellular uptake of magnetic nanoparticle is mediated through energydependent endocytosis in A549 cells

Biocompatible silica-overcoated magnetic nanoparticles containing an organic fluorescence dye, rhodamine B isothiocyanate (RITC), within a silica shell [50 nm size, MNP@SiO2(RITC)s] were synthesized. For future application of the MNP@SiO2(RITC)s into diverse areas of research such as drug or gene delivery, bioimaging, and biosensors, detailed information of the cellular uptake process of the nanoparticles is essential. Thus, this study was performed to elucidate the precise mechanism by which the lung cancer cells uptake the magnetic nanoparticles. Lung cells were chosen for this study because inhalation is the most likely route of exposure and lung cancer cells were also found to uptake magnetic nanoparticles rapidly in preliminary experiments. The lung cells were pretreated with different metabolic inhibitors. Our results revealed that low temperature disturbed the uptake of magnetic nanoparticles into the cells. Metabolic inhibitors also prevented the delivery of the materials into cells. Use of TEM clearly demonstrated that uptake of the nanoparticles was mediated through endosomes. Taken together, our results demonstrate that magnetic nanoparticles can be internalized into the cells through an energy-dependent endosomal-lysosomal mechanism.

Cancer immunotherapy using dendritic cell-derived exosomes

Dendritic cells (DCs) are the most potent antigen presenting cells and the only ones capable of inducing primary cytotoxic immune responses. We found that DCs secrete a population of membrane vesicles, called exosomes. Exosomes are 60-80 nm vesicles of endocytic origin. The protein composition of exosomes was subjected to a systematic proteomic analysis. Besides MHC and co-stimulatory molecules, exosomes bear several adhesion proteins, most likely involved in their specific subjected to targeting. We also found that exosomes accumulate several cytosolic factors, probably involved in their endosomal biogenesis. Like DCs, exosomes induced immune responses in vivo. Indeed, a single injection of DC-derived exosomes sensitized with tumor peptides induced potent anti tumor immune responses in mice and the eradication of established tumors. Tumor-specific cytotoxic T lymphocytes were found in the spleen of exosome-treated mice, and the anti tumor effect of exosomes was sensitive to in vivo depletion of CD8+ T cells. These results show that exosomes induce potent anti tumor effects in vivo, and strongly support the implementation of human DC-derived exosomes for cancer immunotherapy.