Intermolecular Exchange, Solvent Microenvironment, and Catalysis in Nanoparticulate Complexes of Nucleic Acids and Polycationic Polymers.

[摘要] Leveraging solution NMR techniques, we obtain information on the site-specific structure and dynamics of polyplex components. Results on a model polyplex of a short hairpin RNA, the 29-nucleotide transactivation response element (TAR) from the human immunodeficiency virus type 1 (HIV-1) and PEGylated G5-PAMAM (G5-PEG) show that while the RNA exit, in rapid intermolecular exchange between free and bound forms, no significant change in its structure or fast dynamics is observed upon polyplex formation at low N:P ratios. However, structural perturbations at N:P ratios > 1 cannot not be ruled out owing to low signal from RNA. DLS measurements reveal polydisperse polyplexes with the majority of polyplexes having small average size consistent with the size measured using NMR relaxation parameters. In addition, using fluorescently tagged and untagged RNA, it was demonstrated that the RNA in the complexes can be competitively exchanged rapidly in solution over a wide range of N:P ratios. Combining these studies we provide a picture of polyplexes as dynamic assemblies in which the bound nucleic acid are capable of intermolecular exchange. Such a dynamic exchange could potentially provide mechanisms for intracellular release of delivered therapeutic nucleic acids.We use prototropic/solvatochromic fluorescein dye to characterize the local solvent environments in these complexes. It is observed that the nucleic acid-POCP interactions gives rise to unique microenvironments with solvent properties like local pH being significantly different than that of bulk solution. The magnitude of local changes is highly dependent on the polymer type, with branched polymers displaying more acidic microenvironments compared to linear polymers. This data demonstrates that polymer structural details play a key role in defining the heterogeneity in local solvent environments in polyplexes.

[发布机构] University of Michigan

[效力级别] Exchange dynamics in polyplexes

[关键词] Complexes of nucleic acids and polycationic polymers (polyplexes);Exchange dynamics in polyplexes;Solvent microenvironment in polyplexes;Catalysis in polyplexes;Chemistry;Science;Chemistry