title: Dynamic and structural scalings of the complexation between pDNA and bPEI in semidilute and low-salt solutions.
abstract: Using a combination of static and dynamic laser light scattering, we investigated the complexation of a supercoiled plasmid DNA (pDNA, 10(4) bp) and a branched polyethyleneimine (bPEI, M(w) = 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 (<I>) and the average linewidth of the Rayleigh peak (<Gamma>) are scaled to the scattering vector (q) as <I> proportional, variant q(alpha(s) ) or <Gamma> proportional, variant q(alpha(D) ), where alpha(S) and alpha(D) 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.
authors.affiliation: Department of Chemistry, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong.
authors.forename: Rui
authors.initials: R
authors.lastname: Deng
authors.forename: Shu
authors.initials: S
authors.lastname: Diao
authors.forename: Yanan
authors.initials: Y
authors.lastname: Yue
authors.forename: To
authors.initials: T
authors.lastname: Ngai
authors.forename: Chi
authors.initials: C
authors.lastname: Wu
authors.forename: Fan
authors.initials: F
authors.lastname: Jin
mesh_terms: D000838:Anions; D001703:Biophysics / Q000379:methods*; D001704:Biopolymers / Q000737:chemistry; D003198:Computer Simulation; D004247:DNA / Q000737:chemistry*; D017709:Fractals; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D008968:Molecular Conformation; D010957:Plasmids / Q000378:metabolism*; D011094:Polyethyleneimine / Q000737:chemistry*; D012492:Salts / Q000737:chemistry; D012996:Solutions; D014162:Transfection
chemical_list: D000838:Anions; D001704:Biopolymers; D012492:Salts; D012996:Solutions; D011094:Polyethyleneimine; D004247:DNA