Synthesis of linear polyethylenimine and use in transfection

Linear polyethylenimine (LPEI) is an efficient transfection reagent for a broad range of cell lines and primary cells and is also useful for local or systemic gene delivery in vivo. In contrast to many other nonviral transfection methods, LPEI is less dependent on mitosis and also transfects postmitotic cells. Transfections can be performed with a simple protocol, as described here. The presence of serum (up to 10%) during transfection does not markedly decrease transfection efficiency, but it significantly reduces toxicity, especially to primary cells. This is a major advantage compared to most lipidic transfection systems. Toxicity can also be kept to a minimum using low, optimized amounts of the transfection reagent. However, LPEI can be quite toxic when applied at elevated doses in vitro or in vivo. LPEI is a fully synthetic product that can be easily synthesized from rather inexpensive precursors and is suitable for large-scale transfections. This protocol describes the synthesis of LPEI from a precursor polymer and the generation of DNA/LPEI polyplexes. Transfection protocols for cells adherent to tissue culture dishes or grown in suspension are given, as are in vivo applications.