Abstract: Objective To characterize the mechanism of cellular uptake of dandelion decoctosome. Methods Internalization of fluorescently-labeled dandelion decoctosome was evaluated in A549 cells. By using a range of chemical inhibitors to block specific pathways as well as RNA interference (RNAi) to knockdown key proteins involved in individual endocytic pathways, cellular uptake of dandelion decoctosome was assessed using flow cytometry and confocal microscopy. Results Lysosomotropic agents significantly decreased dandelion decoctosome entering into cells（P<0.01）. Moreover, inhibitors of macropinocytosis, including cytochalasin D and amiloride significantly reduced the internalization of dandelion decoctosome in a dose dependent manner（P<0.001）. Consistently, knockdowning of Rac1 and PAK1 by RNAi impeded the cell entry of dandelion decoctosome（P<0.05）. Conclusions dandelion decoctosome enters cells via endocytosis and predominantly via macropinocytosis.

Key words: exosomes, decoctosome, endocytosis, macropinocytosis