Formation of DNA nanoparticles in the presence of novel polyamine analogues: a laser light scattering and atomic force microscopic study

Abstract

We synthesized a pentamine (3-3-3-3) and two hexamine (3-3-3-3-3 and 3-4-3-4-3) analogues of the natural polyamine, spermine (3-4-3) and studied their effectiveness in condensing pGL3 plasmid DNA, using light scattering and atomic force microscopic (AFM) techniques. The midpoint concentration of the polyamines on pGL3 condensation (EC50) was 11.3, 10.6, 1.5, 0.49 and 0.52 micro M, respectively, for 3-4-3, norspermine (3-3-3), 3-3-3-3, 3-3-3-3-3 and 3-4-3-4-3 in 10 mM Na cacodylate buffer. Dynamic laser light scattering study showed a decrease in hydrodynamic radii of plasmid DNA particles as the number of positive charges on the polyamines increased. AFM data showed the presence of toroids with outer diameter of 117-191 nm for different polyamines, and a mean height of 2.61 +/- 0.77 nm. AFM results also revealed the presence of intermediate structures, including those showing circumferential winding of DNA to toroids. The dependence of the EC50 on Na+ concentration suggests different modes of binding of spermine and its higher valent analogues with DNA. Our results show a 20-fold increase in the efficacy of hexamines for DNA condensation compared to spermine, and provide new insights into the mechanism(s) of DNA nanoparticle formation. These studies might help to develop novel nonviral gene delivery vehicles.

Peptide-Functionalized Poly(ethylene glycol) Star Polymers: DNA Delivery Vehicles with Multivalent Molecular Architecture

“…In water, the polyplex size varies between about 90 and 200 nm, which is consistent with the sizes of polyplexes created with un-PEGylated polycations (54,(56)(57)(58). Upon the addition of Opti-MEM, PEG-PF4 ZIP and PEG-ATIII polyplexes did not aggregate and showed a small and uniform polyplex size over 120 min.…”

Morphological variation in a toroid generated from a single polymer chain

“…This model offers two merits. First, we 8 can determine the shape of the cross-section of a toroid. Next, from an experimental point of view, we can determine the effect on DNA of a chemical added to the DNA solution by considering the image of a toroid; by determining whether the chemical effectively changes the thickness or stiffness of a DNA chain.…”

“…It is well known that a toroid structure is generated from a giant DNA molecule upon the addition of condensing agents such as multivalent cations, polyamines and neutral flexible polymers [1][2][3][4][5][6][7][8] . After a full survey of previous experimental studies on a DNA toroid, Bloomfield stated that "---the major diameter of the condensed particle remains almost constant on the order of 60-80 nm and does not seem to depend upon the length of an individual DNA molecule, so long as the DNA length is from 400 to over 40,000 base pairs (bp)."…”

Evaluation and Elucidation of DNA‐Containing Viologen Dendrimer Complex Formation

“…[19] Vijayanathan et al have surveyed the suggested structures of pure and complexed plasmid DNA. [20] Recently, a plectonemic structure on mica has been used as a model for pure plasmids, and toroidal structures have been proposed for polyplexes [21] and dendriplexes. [22] For polyplexes, structures have been suggested in which the toroidal plasmid is wrapped around den- Figure 1.…”