Polymeric micelles self-assembled from amphiphilic polymers with twin disulfides used as siRNA carriers to enhance the transfection.

The sequence-defined polycationic polymers with or without Cys-Arg-Cys motifs conjugated with targeting and shielding segments were synthesized as siRNA carriers via native chemical ligation (NCL) reaction. After purification, the structures and physicochemical characteristics were determined by a variety of experimental techniques. The particle size of siRNA/CRC-polymer polyplex was much smaller than that of polyplex without CRC motifs. The buffer capacity and siRNA binding ability of CRC motifs modified polymers were significantly improved, resulting from the twin disulfides and hexatomic ring formulation. The critical micelle concentrations of the polymers were <10mg/L, indicating formation of polymeric micelles and sufficient stability of the system. The CRC motifs modified polymers with folate targeted ligands exhibited a strongly enhanced cellular uptake than the negative control and the unmodified analogues. The results of gene transfection showed that the folate-PEG-ligated polymer modified with CRC motifs had much better gene transfection compared to the alanine-ended control and other analogues. Furthermore, they showed barely cytotoxicity. By the way, there was no distinctly improvement for pDNA transfection. All above results suggested that folate-PEG-ligated polymers modified with CRC motifs and their self-assembly polymeric micelles could be promising non-viral siRNA carriers.