The hydrodynamic radii (Rh) of different DNA polyplexes were measured using a Brookhaven Zeta PALS Zeta Potential Analyzer in the Multi-Angle Particle Size Option at a scattering angle of 90º at 25 ºC. Before preparation of the particles, all solutions were filtered through a Whatman 25 mm GD/X filter unit with 0.45 µm pore size to exclude colloidal contamination. Samples were prepared by mixing 1 µg of pBR322 DNA with each polycation (at N/P 3) in 1000 µL of 10 mM Tris. Samples were thereafter incubated at room temperature for 30 minutes, then measured. Samples were prepared in triplicates with the diameter obtained in each replicate being the average of 5 scattered intensity weighted scans taken over 150 seconds.