Packaging of DNA by shell crosslinked nanoparticles

Abstract

We demonstrate compaction of DNA with nanoscale biomimetic constructs which are robust synthetic analogs of globular proteins. These constructs arẽ 15 nm in diameter, shell crosslinked knedel-like (SCKs) nanoparticles, which are prepared by covalent stabilization of amphiphilic di-block co-polymer micelles, self-assembled in an aqueous solution. This synthetic approach yields size-controlled nanoparticles of persistent shape and containing positively charged functional groups at and near the particle surface. Such properties allow SCKs to bind with DNA through electrostatic interactions and facilitate reduction of the DNA hydrodynamic diameter through reversible compaction. Compaction of DNA by SCKs was evident in dynamic light scattering experiments and was directly observed by in situ atomic force microscopy. Moreover, enzymatic digestion of the DNA plasmid (pBR322, 4361 bp) by EcoRI was inhibited at low SCK:DNA ratios and prevented when ≤ ≤ ≤ ≤60 DNA bp were bound per SCK.Digestion by MspI in the presence of SCKs resulted in longer DNA fragments, indicating that not all enzyme cleavage sites were accessible within the DNA/SCK aggregates. These results have implications for the development of vehicles for successful gene therapy applications.

Single-molecule experiments in biological physics: methods and applications

“…Recent studies of DNA condensation have considered synthetic condensing agents much simpler than protein histones such as shell crosslinked nanospheres [218] and dendrimers [219]. Dendrimers are synthetic branched polymers that are synthesized via an initiator core terminating (after a repeated series of steps) with amino N H 2 (D) FECs of DNA fibers (red curves) condensed with dendrimers of generation G8 (diameter of particles around 10 nm) [217].…”

PEGylated polymers for medicine: from conjugation to self-assembled systems

“…Examples of micelles with cross-links in the corona are referred to as shell cross-linked micelles (SCMs), or shell cross-linked nanoparticles (termed SCKs, after the initially-coined term ''shell cross-linked knedels''). Wooley and co-workers described the preparation and characterization of SCKs in 1996, 141 and the concept has since been extended considerably to provide a suite of tailored nanoparticles for drug delivery, 142 by the addition of biologically active moieties, [143][144][145][146][147] imaging agents, 148,149 stimuli-sensitive and degradable linkages, 11,13,150,151 core excavation, 16 and PEGylation. 152 One recent detailed study compared PEGylated and non-PEGylated SCK's with different hydrophobic cores, one consisting of the malleable poly(methyl acrylate), and the other composed of hard polystyrene.…”

DNA Spools under Tension

“…Prominent examples of DNA wrapping proteins are: the Lac1 repressor [2] participating in the bacterial gene regulation, the DNA-gyrase [3] directing changes in DNA topology, RNA polymerase [4] copying DNA to RNA, and the histone octamer [5] performing DNA packaging into nucleosomes leading in each cell to the enormous condensation of meters of DNA into micron sized chromosomes. Besides the natural wrapped architectures there are attempts to design nanoparticles imitating that motive [6] as a means to efficiently pack and transport DNA into cells. In most of these ligand-DNA complexes the geometry and chemistry of the ligand surface enforces the DNA to follow a superhelical wrapping path with one or more tight turns.…”