Particle Size and Zeta Potential Measurements. Polyplex particle sizing and zeta potential measurements were made using a ZetaPALS dynamic light scattering instrument (Brookhaven Instruments, Holtsville, NY, 15 mW laser). Complexes were prepared in 10 mM Tris buffer at the desired polymer to DNA weight ratios as described above and incubated at room temperature for 30 min. Immediately prior to dynamic light scattering (DLS) measurements, each sample was diluted to a final concentration of 2 μg DNA/mL using buffer. Correlation functions were collected by DLS using a 90Plus/BI-MAS automatic particle sizer (Brookhaven Instruments, NY). DLS measurements were performed prior to zeta (ζ)-potential measurements. To assess polyplex surface charge, ζ-potential measurements of polyplexes were performed on a BIC ZetaPALS (Brookhaven Instruments, Holtsville, NY) at a 15° scattering detector angle. Each measurement was taken in triplicate with four runs and ten cycles acquisition per run. The ζ-potentials were calculated using the PALS software and Smoluchowki model for aqueous solutions, and the hydrodynamic diameter determined by applying the Stokes-Einstein equation from the experimentally determined translational diffusion coefficient. Data presented as mean ± SD (n =3).