Characterization and evaluation of a folic acid receptor-targeted cyclodextrin complex as an anticancer drug delivery system.

To improve the water solubility and tumor targeting ability of docetaxel (DTX), and thus enhance the drug's antitumor efficacy and safety, a novel folate receptor (FR)-targeted cyclodextrin drug delivery vehicle (FA-CD) was successfully synthesized. The synthesis of the designed cyclodextrin was confirmed by Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR), and differential scanning calorimetry (DSC). The in vitro cytotoxicity was investigated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and the results showed that no significant differences (p>0.05) appeared in cytotoxicity between the different cyclodextrins in the different cell lines. Besides, the DTX/FA-CD inclusion complex was prepared. The cellular uptake and competition assays were examined using the HepG2, HeLa, and KB cell lines, which have different levels of folate receptor expression. Interestingly, the Cy5.5/FA-CD complex had higher uptake in the HepG2, HeLa, and KB cells, compared with non-targeted Cy5.5/CD complex (p<0.001). The time-dependent drug uptake into KB cells observed by LSCM confirmed the drug delivery via endocytic routes. Data from the competition assays, especially in KB cells, showed that a significant inhibitory effect (p<0.001) was obtained when the concentration of FA was increased, and suggested that the Cy5.5/FA-CD was internalized through a FR-mediated mechanism. Moreover, the in vitro bioactivity assay also demonstrated efficient antitumor activity, and the order of the cell viabilities (% of control) was OB>HepG2>HeLa>KB for DTX/FA-CD (p<0.001). For DTX/CD, however, it displayed minimum antitumor behavior in all cell types. An apoptosis study by FCM and LSCM also revealed that the FA-modified complexes were more effective in inducing apoptosis in FR-expressing cells. Finally, an in vivo biodistribution study in KB-bearing healthy mice revealed that the DTX/FA-CD complex has enhanced tumor-targeting efficacy and diminished systemic side effects. These results suggest that the novel FR-targeted cyclodextrin complex is a promising alternative as an anticancer drug delivery system.