A low molecular weight fraction of polyethylenimine (PEI) displays increased transfection efficiency of DNA and siRNA in fresh or lyophilized complexes.

RNA interference (RNAi) represents a powerful method for specific gene silencing. It is mediated through small double-stranded RNA molecules (small interfering RNAs, siRNAs) which sequence-specifically trigger the cleavage and subsequent degradation of their target mRNA. One critical factor that determines the success of RNAi is the ability to deliver intact siRNAs into target cells.