Arginine-rich peptides have attracted considerable attention due to their distinct internalization mechanism. It was reported that arginine and guanidino moieties were able to translocate through cell membranes and played a critical role in the process of membrane permeation. In this work, arginine was conjugated to the backbone of chitosan to form a novel chitosan derivative, arginine modified chitosan (Arg-CS). Arg-CS/DNA complexes were prepared according to the method of coacervation process. The physicochemical properties of Arg-CS and Arg-CS/DNA complexes were characterized and the transfection activity and efficiency mediated by Arg-CS/DNA complexes were investigated taking HeLa cells as target cells. Arg-CS was characterized by FTIR and 13C NMR. Arg-CS/DNA polye- lectrolyte complexes were investigated by agarose gel retardation, dynamic light scattering (DLS) and atomic force microscopy (AFM). The results revealed that the Arg-CS/DNA complexes started to form at N/P ratio of 2:1, and the size of particles varied from 100 to 180 nm. The cytotoxicity of Arg-CS and their complexes with plasmid DNA were determined by MTT assay for HeLa cells, and the results suggested that Arg-CS/DNA complexes were slightly less toxic than Arg-CS. Moreover, the derivative alone and their complexes showed significantly lower toxicity than PEI and PEI/DNA complexes, respectively. Taking HeLa cells as target cells and using pGL3-control as reporter gene, the luciferase expression mediated by Arg-CS was greatly enhanced to about 100 folds compared with the luciferase expression mediated by chitosan at different pH media. These results suggest that Arg-CS is a promising candi- date as a safe and efficient vector for gene delivery and transfection.
N-Methylene phosphonic chitosan （NMPCS）, an amphiphilic macromolecule with powerful chelating ability of Ca^2＋ ions, was synthesized and characterized. The physicochernical properties of NMPCS and the interactions between NMPCS and plasmid DNA were investigated by FTIR, ^13C NMR, X-ray, agarose gel electrophoresis retardation assay, atomic force microscopy （AFM） and circular dichroism （CD）. The results suggest that at charge ratio 2：1 or above, DNA could be completely entrapped and spherical complexes with mean size of 80-210 nm were formed. Taking HeLa as host cell, luciferase expression mediated by NMPCS improved about 100 times compared to the expression mediated by chitosan.
Dun Wan ZhuJin Gen BoHai Ling ZhangWen Guang LiuXi Gang LengCun Xian SongYu Ji YinLi Ping SongLan Xia LiuLin MeiXiu Lan LiYang ZhangKang De Yao
