Despite the recently enlarged field of available RNA knock-down technologies, e.g., antisense oligonucleotides (ASOs) and duplexes of synthetic 21 nucleotides RNAs (siRNAs), no versatile transfection reagent has been reported to deliver different nucleic acids formats at high rates of efficiency. We have evaluated the versatility and efficacy of linear PEI in transfecting and properly delivering a broad panel of nucleic acids such as short oligonucleotides and double-stranded RNA into cells in culture.