21-Arm star polymers with different cationic groups based on cyclodextrin core for DNA delivery

A series of cationic star polymers with 21 arms (21ACSPs) were synthesized through atom transfer radical polymerization using a β-cyclodextrin initiator with 21 initiation sites. Monomers containing primary, tertiary amino and quaternary ammonium groups were polymerized using 21Br-β-CD, Cu(I)Br and 2,2′-dipyridyl as initiator, catalyst and ligand, respectively. It was found that a co-solvent of 1-methyl-2-pyrrolidione and water (1:1) could facilitate the reaction, resulting in a well-controlled living polymerization. The conversion was up to 95% compared to the previously reported method (60%). AFM and DLS measurement revealed that 21ACSPs have the ability to condense the plasmid DNA (pCMV-Luc) to 80–180 nm. 21ACSPs with primary and tertiary amino groups exhibited higher cell transfection efficiency to CHSE-214 cells than 21ACSPs with quaternary ammonium groups. Meanwhile, all of the reported star polymers have no obvious cytotoxicity. The findings from this work are expected to be helpful for the development of efficient DNA delivery system.