Self-assembled oligopeptide nanostructures for co-delivery of drug and gene with synergistic therapeutic effect

In this study, oligopeptide amphiphile containing three blocks of amino acids, Ac-(AF)(6)-H-5-K-15-NH2 (FA32), were synthesized and evaluated as carriers for co-delivery of drug and gene. Doxorubicin (DOX), luciferase reporter gene, and p53 gene were used as a model drug and genes. The peptide amphiphile self-assembled into cationic core-shell nanostructures (i.e. micelles), with a CIVIC value of around 0.042 mg/mL, estimated by fluorescent spectroscopy technique. FA32 nanostructures had an average size of 102 +/- 19 nm, and a zeta potential of 22.8 +/- 0.2 mV. These nanostructures had a high capacity for DOX encapsulation, with a DOX loading level of up to 22%. In addition, DOX release from the micelles was sustained without obvious initial burst. DOX-loaded micelles were effectively taken up by HepG2 cells, with an IC50 of 1.8 mg/L for DOX-loaded FA32, which was higher than that of free DOX (0.25 mg/L). In addition, FA32 micelles condensed DNA efficiently to form small complexes with net positive charge on the surface. In vitro gene transfection studies showed that FA32 induced comparable gene expression level to polyethylenimine. Co-delivery of drug and gene using FA32 micelles was demonstrated via confocal imaging, luciferase expression in the presence of DOX, and synergy in cytotoxic effect between p53 gene and DOX. It was shown that through simultaneous delivery of both p53 gene and DOX using FA32 micelles, an increase in p53 mRNA expression level as well as end point cytotoxicity towards HepG2 cells was achieved. FA32 micelles, therefore, have a great potential in delivering hydrophobic anticancer drug and gene simultaneously for improved cancer therapy. (C) 2009 Elsevier Ltd. All rights reserved.