A pH-sensitive polymer that enhances cationic lipid-mediated gene transfer

The efficient release of nonviral gene carriers from endosomes is an import ant step for the successful delivery of DNA into the cell nucleus. A synthe tic pH-sensitive anionic polymer, poly(propylacrylic acid) (PPAA), was desi gned to aid in endosomal escape of nonviral vectors and improve the transfe ction efficiencies with these vectors. Transfection of NIH3T3 fibroblasts w ith ternary physical mixtures of the cationic lipid DOTAP, pCMV beta plasmi d DNA, and PPAA showed marked enhancement of both gene expression levels an d fraction of cells transfected compared to binary control mixtures of DOTA P and DNA. PPAA also significantly improved the serum-stability of DOTAP/DN A vectors. The DOTAP/DNA/PPAA vectors maintained high levels of transfectio n in media containing up to 50% serum. The striking enhancement of transfec tion efficiency with cationic lipid/DNA/PPAA mixtures, along with the enhan ced serum-stability, suggests that PPAA may provide significant improvement s for the in vivo intracellular delivery of drugs such as DNA, oligonucleot ides, proteins, and peptides.