Characterization of 9-nitrocamptothecin-in-cyclodextrin-in-liposomes modified with transferrin for the treating of tumor.

Encapsulation of hydrophobic drugs in the form of drug-cyclodextrin (CD) complex in liposomes has been applied as a novel strategy to combine the relative advantages of CDs and liposomes into one system, naming drug-in-CD-in-liposome (DCL). In the present study, soluble 9-NC/hydroxypropyl-β-cyclodextrin (HP-β-CD) inclusion complexes were prepared using the freeze-drying technique. Then 9-NC inclusion complexes were further encapsulated into liposomes by ethanol injection method and transferrin (Tf) was conjugated to the surface of 9-NC DCL to obtain Tf modified 9-NC DCL (Tf-9-NC-CL). Compared to PEGylated 9-NC DCL (P-9-NC-CL), the lactone stability and vesicle stability of Tf-9-NC-CL were significantly increased. Both 9-NC and HP-β-CD were found to release from the DCL and Tf modification resulted in reduced release of them. The enhanced targeting efficiency of the Tf-modified liposomes was demonstrated by flow cytometry and confocal microscopy. In vivo pharmacokinetics in rats showed improved lactone stability of 9-NC following intravenous injection of Tf-9-NC-CL. The cytotoxicity of Tf-9-NC-CL against tumor cells and normal cells was investigated in vitro and the antitumor efficacy was evaluated in S180 tumor-bearing mice in vivo. Compared with free 9-NC, 9-NC inclusion complexes and P-9-NC-CL, Tf-9-NC-CL demonstrated the strongest cytotoxicity to tumor cells. And the inhibitory rate of tumor (IRT) values were determined to be 43.08%, 56.92%, 67.69% and 80.00% for 9-NC solution, inclusion complexes, P-9-NC-CL and Tf-9-NC-CL, respectively. In conclusion, Tf modification can be useful in increasing vesicle stability, targeting drug delivery efficiency and antitumor efficacy of DCL containing hydrophobic antitumor drugs, such as 9-NC.