Formation and structure of PEI/DNA complexes: quantitative analysis

Abstract

Controlled formation of gene delivery complexes (DNA and a vector, usually a cationic polymer) is one of the key challenges in developing efficient gene delivery systems. The researchers focused their procedures on the ratio of vector to DNA, neglecting the influence of concentration on the complex formation process. In this study we show, by studying the association of polyethylenimine (PEI) and 66-base pair (bp) DNA fragments, that the concentration of the gene delivery system greatly influences the formation of PEI/DNA complexes even at a fixed PEI/DNA ratio. We find that the charge and the size of PEI/DNA complexes are increasing functions of their concentration even in a highly dilute regime of concentrations. The number of PEI/DNA molecules in a complex was calculated from the measured charge and electrophoretic mobility. We established a model, on the basis of Smoluchowski theory, to explain the relation between the concentration and the size of PEI/DNA complexes. We analyzed the structure of the complexes and found out that a large proportion of space in the PEI/DNA complexes is occupied by the solvent. This study indicates that the influence of concentration should be seriously considered in gene delivery studies, since large PEI/DNA complexes can be prepared by scaling up their concentration simultaneously without increasing the dosage of PEI.

Intrinsic MRI contrast from amino acid-based paramagnetic ionic liquids

“…Such a complex occurs when all negative phosphate groups bind with positive cation. 55,56 This result is also in accordance with observations from the ITC enthalpogram. The zeta potentials of DNA in the presence of other PMILs are given in the ESI, † (Fig.…”

Characterization of Caulobacter crescentus FtsZ Protein Using Dynamic Light Scattering

“…DLS is a technique used to determine the distribution of the size of nucleotides and proteins (20) through the temporal correlation of the fluctuating intensity of scattered light (21). We anticipated that DLS could provide quantitative data on the kinetics of FtsZ polymerization and depolymerization in vitro that are not measurable with many other techniques that are often used to study protein assembly, including static light scattering (SLS) (22)(23)(24), transmission electron microscopy (TEM) (16), and atomic force microscopy (AFM) (25).…”

Recent progress in gene therapy to deliver nucleic acids with multivalent cationic vectors

“…3 shows a tipical plot of size vs the charge ratio of the nano-aggregate formed by the (C 12 Am) 2 C 12 -siRNA lipoplex [114]. This procedure has been followed to get the size for: (a) lipoplexes formed by pDNA with GCLs [64,66,111,115,137] or MVCLs [138,139]; (b) polyplexes formed by pDNA with cationic polymers [95,98,[124][125][126]140] or polycations [134,141,142]; (c) lipoplexes formed by siRNA with GCLs [114] or MVCLs [139,143]; and (d) polyplexes formed by siRNA with cationic polymers [90,105,144] or polycations [145]. Additionally, SLS and DLS methods also provide an estimation of the electroneutrality ratio of the nanoaggregates because, at this point (see Fig.…”