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 transfection efficiencies. This can be achieved by condensation or aggregation of the DNA using the attractive interaction of DNA with cationic polyelectrolytes or histones. In recent years, the use of poly(ethylene imine) has gained importance in this field. In our study, we characterize the hydrodynamic properties of the dendrimeric cationic polyelectrolyte poly(ethylene imine) (PEI; Mw=25 kDa) and of short DNA fragments (≈150 bp) in solution by dynamic light scattering. On this basis we determine structural parameters of the formed aggregates. On mixing the DNA fragments with the cationic polyelectrolyte, an instantaneous formation of large aggregates is found. This is different compared to condensation with small cations, which can not condense short DNA fragments. The experimental conditions (pH, etc.) during the measurements correspond to the situation in transfection experiments.