Interaction of short DNA fragments with the cationic polyelectrolyte poly(ethylene imine): a dynamic light scattering study

In genetic engineering and gene therapy, it is important to obtain high tra nsfection efficiencies. This can be achieved by condensation or aggregation of the DNA using the attractive interaction of DNA with cationic polyelect rolytes or histones. In recent years, the use of poly(ethylene imine) has g ained importance in this held. In our study, we characterize the hydrodynam ic properties of the dendrimeric cationic polyelectrolyte poly(ethylene imi ne) (PEI; M-W = 25 kDa) and of short DNA fragments (approximate to 150 bp) in solution by dynamic light scattering. On this basis we determine structu ral parameters of the formed aggregates. On mixing the DNA fragments with t he cationic polyelectrolyte, an instantaneous formation of large aggregates is found. This is different compared to condensation with small cations, w hich can not condense short DNA fragments. The experimental conditions (pH, etc.) during the measurements correspond to the situation in transfection experiments. (C) 2000 Elsevier Science B.V. All rights reserved.