Preparation of a low molecular weight polyethylenimine for efficient cell transfection

Polyethylenimines (PEIs) of a molecular weight between 25 and about 800 kDa have successfully been used for in vitro and in vivo gene delivery approaches. Recent publications indicated that PEI molecules of lower molecular weight and a small molecular weight range are also efficient transfection reagents with a much lower cytotoxicity compared to high molecular weighs PEIs. Here, we describe the application of molecular sieve chromatography to fractionate a convnercinllv available 25-kDa PEI. We generated three pools of PEIs with molecular weight ranges of 70-360(1), 10-70 (II), and 0.5-10 kDa (III), respectively We show that, in comparison,with the 25-kDn PEI, pool III increased the expression of lucifel ase up to 100-fold and the number of transfected cells 2-3-fold. In addition, the kinetics of reporter gene expression was also much faster in pool III, compared with the 25-kDa PEI or with pools I or II. Finally, pool III short ed the lowest cytotoxicity in comparison with the other PEI preparations. Thus, we provide a one-step processing of a 25-kDa PEI, resulting in a more effective and also less cytotoxic transfection reagent.