Cytotoxicity and Cellular Internalization of Epirubicin-Loaded Folate-Conjugated Pullulan Acetate Nanoparticles in Cancer Cells

In this study, epirubicin (EPI)-loaded folate-conjugated pullulan acetate nanoparticles (FPA NPs) were prepared, and their cytotoxicity and cellular internalizations were systematically investigated in HeLa, MCF-7 and HepG2 cells at different folate-receptor (FR) expression levels. FPA/EPI NPs had a regular spherical shape and their size was 268.5 +/- 12.0 nm with a narrow distribution. FPA/EPI NPs showed variable degrees of cytotoxicity against HeLa, MCF-7 and HepG2 cells, and their half maximal inhibitory concentrations (IC50) value were 2.31 mu g/mL, 4.03 mu g/mL and 7.35 mu g/mL, respectively, after 72 h incubation. After 2 h incubation, FPA/EPI NPs were efficiently internalized in Hela, MCF-7 and HepG2 cells, and their cellular uptakes were significantly inhibited at 4 degrees C. To study the effect of various inhibitors on the uptake of FPA/EPI NPs, cells were preincubated with the inhibitors individually. The results showed that clathrin-mediated endocytosis and cell macropinocytosis were involved in the cellular internalizations of FPA/EPI NPs in Hela, MCF-7 and HepG2 cells, but FR-mediated endocytosis was only observed in FR-overexpressed Hela and MCF-7 cells. In summary, our data suggested that FPA NPs could be potentially used as a drug carriers for targeted therapy of the FR-overexpressed cancers.