Preparation of poly(glutamic acid) shielding micelles self-assembled from polylysine-b-polyphenylalanine for gene and drug codelivery

A novel amphiphilic cationic block copolymer polylysine-b-polyphenylalanine (PLL-b-PPhe) was synthesized and self-assembled into micelles in aqueous solution, then shielded with poly(glutamic acid) (marked as PG/PLL-b-PPhe) to codeliver gene and drug for combination cancer therapy. Here, doxorubicin (DOX) was selected to be loaded into PLL-b-PPhe micelles and the drug loading efficiency was 8.0%. The drug release studies revealed that the PLL-b-PPhe micelles were pH sensitive and the released DOX could reach to 53.0%, 65.0%, 72.0% at pH 7.4, 6.8 and 5.0, respectively. In order to reduce positive charge and cytotoxicity of PLL-b-PPhe micelles, PG was used as shelding, simultaneously condensed with Bcl2 siRNA to form gene carrier system. Compared with PEI, PG/PLL-b-PPhe had excellent gene transfection efficiency, especially when the molar ratio of PLL to PPhe was 30:60 and the mixed mass ratio of PLL-b-PPhe to gene was 5:1. More importantly, DOX and Bcl2 siRNA gene codelivery system displayed remarkable cytotoxicity against B16F10 cells. Confocal laser scanning microscopy (CLSM) and flow cytometry were used to characterize endocytosis of the codelivery system, and confirmed that both DOX and Bcl2 siRNA had been endocytosed into B16F10 cells. The above results indicated that gene and drug codelivery was a promising strategy in future cancer therapy.