Negatively charged self-assembling DNA/poloxamine nanospheres for in vivo gene transfer. Nucleic Acids Res

Over the past decade, numerous nonviral cationic vectors have been synthesized. They share a high density of positive charges and efficiency for gene transfer in vitro. However, their positively charged surface causes instability in body fluids and cytotoxi-city, thereby limiting their efficacy in vivo. Therefore, there is a need for developing alternative molecular structures. We have examined tetrabranched amphi-philic block copolymers consisting of four polyethy-leneoxide/polypropyleneoxide blocks centered on an ethylenediamine moiety. Cryo-electron microscopy, ethidium bromide fluorescence and light and X-ray scattering experiments performed on vector–DNA complexes showed that the dense core of the nano-sphere consisted of condensed DNA interacting with poloxamine molecules through electrostatic, hydro-gen bonding and hydrophobic interactions, with DNA molecules also being exposed at the surface. The supramolecular organization of block copolymer/ DNA nanospheres induced the formation of negat-ively charged particles. These particles were stable in a solution that had a physiological ionic composi-tion and were resistant to decomplexation by heparin. The new nanostructured material, the structure of which clearly contrasted with that of lipoplexes and polyplexes, efficiently transferred reporter and ther-apeutic genes in skeletal and heart muscle in vivo. Negatively charged supramolecular assemblies hold promise as therapeutic gene carriers for skeletal and heart muscle-related diseases and expression of therapeutic proteins for local or systemic uses