DNA Condensation by PAMAM Dendrimers:  Self-Assembly Characteristics and Effect on Transcription

Abstract

Electrostatic shielding and steric blocking by histones are two significant factors that participate in the control of the local rates of transcription in chromatin. As a simple model system to determine how the degree of DNA condensation affects enzyme accessibility and gene expression, we have used generation 5 polyamidoamine (G5 PAMAM) cationic dendrimer particles (size 5.4 nm) as a synthetic histone model together with an in vitro transcription assay. The degree of compaction, conformation, and binding availability of the dendrimer-DNA complexes is characterized by linear and circular dichroism, dynamic light scattering, and competitive binding of ethidium. Using ultracentrifugation we are able to show explicitly, for the first time, that dendrimer particles bind to DNA in a highly cooperative manner, and that the dendrimer-induced condensation of the DNA strongly attenuates transcription. Two fractions with different properties can be identified: a low-density fraction which behaves very similar to uncondensed DNA and a high-density fraction which is condensed to a high extent and where binding availability and transcription are strongly reduced. Circular dichroism gives clues to the structure of the condensed DNA indicating long-range order between the helices such as in polymer-salt-induced cholesteric liquid crystalline domains, one possible shape being a toroidal structure. On the basis of the experimental data, we propose a model for the self-assembly of the dendrimer-DNA system.

Evaluation of anionic half generation 3.5–6.5 poly(amidoamine) dendrimers as delivery vehicles for the active component of the anticancer drug cisplatin

“…Poly(amidoamine) or PAMAM dendrimers consist of polyamide branches stemming from a central ammine or diaminoalkane core (see Fig. 1 [10][11][12][13][14], whereas the half generation dendrimers have multiple anionic charges which are ideal for cationic drugs or for reversible coordination to platinum complexes [15]. PAMAM dendrimers of generations 1 to 10 are nanometre in diameter, and thus, ideal for targeting tumours through the EPR effect.…”

Synthesis of a novel PEGDGA-coated hPAMAM complex as an efficient and biocompatible gene delivery vector: an in vitro and in vivo study

“…Both Results of confocal microscopy, demonstrating lysosomes containing nanoparticles labeled with fluorescent, and these findings could be the reasons for our claim. However, trends for increased internalization of nanoparticles in 15 and 60 min are depicted in Figure 9 (Choi et al, 2004b;Fant et al, 2008).…”

“…However, a PAMAM dendrimer molecule has a well-defined spherical shape, representing a high positive surface charge. PAMAM dendrimer molecules have demonstrated considerable efficacy in both gene therapy and drug delivery (Bielinska et al, 1999;Fant et al, 2008;Wang et al, 2010). These molecules combine to form a DNA/dendrimer complex with a relatively low polydispersity index (PDI) which inhibits aggregations.…”

Potential use of folate-polyethylene glycol (PEG)-appended dendrimer (G3) conjugate with α-cyclodextrin as DNA carriers to tumor cells

“…1 Unlike classical polymers, dendrimers have a high degree of molecular uniformity, narrow molecular weight (MW) distribution, specific size and shape characteristics, and a highly functionalized terminal surface. 2 Dendrimers can form complexes with nucleic acid drugs such as plasmid DNA (pDNA), short-hairpin RNA and small-interfering RNA through the electrostatic interaction and bind to glycosaminoglycans (heparan sulfate, hyaluronic acid and chondroitin sulfate) on cell surface, 3,4 and have been shown to be more efficient and safer than either cationic liposomes or other cationic polymers for in vitro gene transfer. 5,6 Cyclodextrins (CyDs) are cyclic (a-1,4)-linked oligosaccharides of a-D-glucopyranose containing a hydrophobic central cavity and hydrophilic outer surface, and they are known to be able to act as host molecules.…”