DNA condensation by partially acetylated poly(amido amine) dendrimers: effects of dendrimer charge density on complex formation.

摘要: The ability of poly(amido amine) (or PAMAM) dendrimers to condense semiflexible dsDNA and penetrate cell membranes gives them great potential in gene therapy drug delivery but their high positive surface charge makes cytotoxic. Here, we describe the effects partial neutralization by acetylation on DNA condensation using light scattering, circular dichroism, single molecule imaging dendrimer-DNA complexes combed onto surfaces tethered those under flow. We find that can be condensed generation-five (G5) even when charges are more than 65% neutralized, such bind negligibly an end-tethered is stretched also fully charged introduced flow DNA, all molecules become equally highly coated with at a rate becomes very fast dendrimer concentration, remain bound during subsequent dendrimer-free buffer. These results suggest presence coexisting dendrimer-bound after bulk mixing two solution may result from diffusion-limited irreversible binding, rather than, or addition to, previously proposed cooperative binding mechanism DNA.