Fig. 4

a FACS analysis for determining the endocytic pathways of FMSPs in PC12 cells. b Intracellular fluorescence intensity of PC12 cells in the presence of different endocytosis inhibitors. c TEM image of caveolae-mediated endocytosis. Insert is a magnified representative area (yellow box) showing the flask-shaped structure of caveolae (60–80 nm). d TEM image of micropinocytosis. The diameter and depth of the invagination structures conform to the characteristic features of micropinocytosis. *P < 0.05