Dynamic and structural scalings of the complexation between pDNA and bPEI in semidilute and low-salt solutions

Using a combination of static and dynamic laser light scattering, we investigated the complexation of a supercoiled plasmid DNA (pDNA, 104 bp) and a branched polyethyleneimine (bPEI, Mw = 25 kD) in semidilute and low-salt aqueous solutions. Our results unearth some scaling laws for dynamic and structural properties of the resultant complexes (polyplexes) with different bPEI:pDNA (N:P) molar ratios. Namely, the average scattering intensity ( ) and the average linewidth of the Rayleigh peak ( ) are scaled to the scattering vector (q) as ∝ q or ∝ q, where αS and αD are two N:P dependent scaling exponents. The N:P ratio strongly affects the complexation. When N:P < 2.0, the motions of the negatively charged and extended pDNA chains and the polyplexes are highly correlated so that they behave like a transient network with a fractal dimension. As the N:P ratio increases, nearly all of pDNA chains condensed and the overall charge of the polyplexes reverses to slightly positive, resulting in a turbid dispersion of large loose aggregates made of smaller, but more compact, polyplexes. Further increase of N:P finally disrupts large loose aggregates, leading to a homogeneous transparent dispersion of the polyplexes. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 571–577, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com