Influence of a neutralizing polymer on cationic lipid mediated delivery of antisense oligonucleotides

The use of antisense oligonucleotides (AS ODNs) to inhibit the expression of specific mRNA targets represents a powerful bioengineering strategy for inhibition of gene expression. Cationic lipids and polymers are frequently used to improve the delivery of AS ODNs to cells, but the resulting complexes often aggregate, bind to serum components, and are trafficked poorly within cells. In this study we show that the addition of a synthetic, pH-sensitive, membrane-disrupting polyanion, poly(propylacrylic acid) (PPAA), improves the in vitro efficiency of the commercial transfection reagent dioleoyl trimethylammonium propane (DOTAP) with regards to oligonucleotide delivery. The cellular uptake of fluorescently labeled oligonucleotides in vitro increased with increasing PPAA content. More importantly, the delivery of an anti-GFP oligonucleotide using the DOTAP/PPAA formulation exhibited sequence-specific downregulation in a cellular screening assay. The extent by which GFP expression in stably GFP-expressing cells was down-regulated was dependent on both the charge ratio and PPAA content of the formulation. Hence, this novel and simple system could, with further study, aid the use of cationic lipids for DNA delivery.