Complexation of Linear DNA and Poly(styrenesulfonate) with Cationic Copolymer Micelles: Effect of Polyanion Flexibility

Abstract

The complexation of linear double stranded DNA and poly(styrenesulfonate) (PSS) with cationic poly(dimethylamino ethyl methacrylate)-block-poly(n-butyl methacrylate) micelles was compared in aqueous solutions at various pH values and ionic strengths. The complexation process was monitored by turbidimetric titration, as a function of the ratio (N/P) of amine groups in the micelle corona to the number of phosphates (or sulfonates) in the polyanion. The size, structure and stability of the resulting micelleplexes were studied by dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryo-TEM). In the short chain regime, where the contour lengths of the polyanions are shorter than or comparable to the micelle corona thickness, micelleplexes with DNA oligomers show very similar behavior to complexes with short PSS chains, in terms of titration curves and structural evolution of the complexes as a function of charge ratio. However, in the long chain regime, where the contour length of the polyanion far exceeds the micelle radius, micelleplexes of linear DNA show titration curves shifted toward lower N/P ratios, reduced stability at N/P < 1, and a higher percentage of small complexes at N/P > 1 compared to complexes with long chain PSS. Furthermore, at 1 M ionic strength, the cationic micelles could still complex with long chain PSS, but not with DNA of the same total charge. These differences are attributed to the flexibility difference between the polyanion chains, and possible mechanisms are proposed. This work highlights the importance of chain flexibility in complexation of dissimilar polyelectrolyte pairs, a factor that could therefore help guide the future design of micelleplexes for various applications.

Packaging pDNA by Polymeric ABC Micelles Simultaneously Achieves Colloidal Stability and Structural Control

“…Polycationic micelles are related systems that consist of self-assembled amphiphilic cationic polymers, and they can complex with DNA to form “micelleplexes”. − The structure of these micelles can be readily tuned − to either mimic a histone octamer, or to adopt a wide range of shapes, such as spheres, disks, and cylinders, , where structural parameters can be systematically varied. In addition, the extremely slow chain-exchange kinetics of micelles with long hydrophobic core blocks ensures that micelle shape is invariant during complexation .…”

“…In addition, the extremely slow chain-exchange kinetics of micelles with long hydrophobic core blocks ensures that micelle shape is invariant during complexation . Further, the components of a micelle corona can be varied from purely cationic to a mixture of cationic and nonionic components in statistical, gradient, or block distributions, which have been shown to influence the structure, rearrangement kinetics, and colloidal stability of their complexes with oppositely charged flexible polyelectrolytes. , Previous studies on micelleplexes with spherical micelles in excess show that the pDNA chains bridge multiple micelles to form large aggregates. − For core–shell micelles with a pure cationic corona, Rinkenauer et al and Jiang et al have observed micelleplexes composed of multiple micelles linked by DNA chains. For micelles with a mixed corona of cationic and hydrophilic nonionic chains, Sharma et al observed that plasmids condense into rodlike structures with micelles decorating the surface .…”

Coarse‐Grained Simulations of the Impact of Chain Length and Stiffness on the Formation and Aggregation of Polyelectrolyte Complexes

“…the numbers of polycations and nucleic acid chains in the polyplex) and, more specifically, if the polyplexes are aggregates, where we use the term aggregate to refer to a polyplex containing multiple polyanion chains. [6][7][8][9][10][11][12][13][14][15] For example, examination of polyplexes consisting of PEI and plasmid DNA has shown that polyplexes can be aggregates containing dozens of DNA plasmids and PEI molecules, [6] and that aggregation depends on DNA concentration, the length and type (e.g. linear or branched) of the PEI, and the ratio of PEI amine groups to DNA phosphates (a property referred to as the N/P ratio).…”

“…Thus, there have been several experimental investigations of how polyelectrolyte length and rigidity impact complex structure. [8][9][10][11][12][13][14][15] Hayashi et al examined complexation between a ~+40 charged PLL-PEG block copolymer and a 21-mer of either double-stranded siRNA or single-stranded RNA. They found that, at sufficient RNA concentrations, complexes formed from single-stranded RNA chains formed aggregates containing many RNA chains, while double-stranded siRNA did not aggregate.…”

Synthesis and Assembly of Designer Styrenic Diblock Polyelectrolytes

“…Nevertheless, these model materials can be used to explore the formation pathways and processing effects between kinetic and thermodynamic products, which has recently been of interest to the advancement of micelleplex delivery vehicles. [53][54][55] Detailed studies on the kinetics of formation and chain exchange in these PEC micelles are ongoing, and a following report is underway. Altogether, performing controlled aqueous RAFT polymerization of ionic monomers in a parallel reactor system is promising toward broadening the materials portfolio of designer PECs.…”