Transfection efficiency increases by incorporating hydrophobic monomer units into polymeric gene carriers

The water soluble terpolymer, poly(N-isopropylacrylamide (IPAAm)-co-2-(dimethylamino)ethyl methacrylate (DMAEMA)-co-butylmethacrylate (BMA)) was synthesized, and its efficiency in in vitro gene transfection was evaluated. Copolymers with different compositions were synthesized by radical polymerization. For a series of copolymers containing 60 mol% of DMAEMA, the plasmid bands were retained within the gel loading slot, independent of polymer/plasmid weight ratios or BMA monomer content. In contrast, for a series of copolymers containing 20 mol% DMAEMA, plasmid bands of complexes were retarded with increasing weight ratios. For the copolymer with 10 mol% BMA content, the plasmid was completely retained within the gel loading slot. The transfection efficiency of polymer/plasmid complexes was evaluated in COS-1 cells using a pCMV-lacZ plasmid, encoding for beta-galactosidase as a reporter gene. Transfection efficiency of a series of copolymers containing 20 mol% of DMAEMA varied with BMA content. The transfection efficiency of the copolymers with 0, 2, and 5 mol% of BMA was low. The transfection efficiency of the copolymers with 10 mol% of BMA was about 2-fold higher than that of the PDMAEMA control homopolymer. The transfected cells were observed at a very wide range of polymer/plasmid weight ratios. The transfection efficiency of all copolymers containing 60 mol% of DMAEMA was lower than that of the PDMAEMA homopolymer.