Poly(L-lysine) (PLL) is a cationic polyelectrolyte of interest for many applications, including in therapeutic biology for DNA complexation and transfection. Several non-lysine based polycations have been shown to afford more efficient transfection in live cells than has been achieved with PLL. We find that reconfiguring polylysine into short oligolysine grafts, strung from a hydrophobic polymer backbone, gives transfection reagents greatly superior to PLL, despite having the identical cationic functional groups (i.e., exclusively primary amines). Altering the oligolysine graft length modulates DNA-polymer interactions and transfection efficiency, while incorporating the PKKKRKV heptapeptide (the Simian virus SV40 large T-antigen nuclear localization sequence) pendent groups onto the polymer backbone led to even greater transfection efficiency over the oligolysine-grafted structures. Protein expression levels obtained with these novel polymer transfection reagents were higher than, or comparable to, expression seen in the cases of JetPEI™, FuGENE® 6 and Lipofectamine™ 2000, the later being notorious for cytotoxicity that accompanies high transfection efficiency. The relative strength of the polymer-DNA complex is key to the transfection performance, as judged by serum stability and PicoGreen analysis. Moreover, polyplexes formed from our graft copolymer structures exhibit low cytotoxicity, contributing to the therapeutic promise of these novel reagents.
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