Cationic methacrylate copolymers containing primary and tertiary amino side groups: Controlled synthesis via RAFT polymerization, DNA condensation, and in vitro gene transfection

A versatile family of cationic methacrylate copolymers containing varying amounts of primary and tertiary amino side groups were synthesized and investigated for ¡n vitro gene transfection. Two different types of methacrylate copolymers, poly(2-(dimethylamino)ethyl methacrylate)/aminoethyl methacrylate [P(DMAEMA/AEMA)j and poly(2-(dimethylamino)ethyl methacrylate)/aminohexyl methacrylate [P(DMAEMA/AHMA)j, were obtained by reversible addition-fragmentation chain transfer (RAFT) copolymerization of dimethylaminoethyl methacrylate (DMAEMA) with ZV-(tert-butoxycarbonyl)aminoethyl methacrylate (Boc-AEMA) or ZV-(ferf-butoxycarbonyl)aminohexyl methacrylate (Boc-AHMA) followed by acid deprotection. Gel permeation chromatography (GPC) measurements revealed that Boc-protected methacrylate copolymers had M _n in the range of 16.1-23.0 kDa and low polydispersities of 1.12-1.26. The copolymer compositions were well controlled by monomer feed ratios. Dynamic light scattering and agarose gel electrophoresis mea-surements demonstrated that these PDMAEMA copolymers had better DNA condensation than PDMAEMA homopolymer. The polyplexes of these copolymers revealed low cytotoxicity at an NIP ratio of 3/1. The in vifro transfection in COS-7 cells in serum free medium demonstrated significantly enhanced (up to 24fold) transfection efficiencies of PDMAEMA copolymer polyplexes as compared with PDMAEMA control. In the presence of 10% serum, P(DMAEMA/AEMA) and P(DMAEMA/AHMA) displayed a high transfection activity comparable with or better than 25 kDa PEI. These results suggestthat cationic methacrylate copolymers are highly promising for development of safe and efficient nonviral gene transfer agents.