title: Balancing cationic and hydrophobic content of PEGylated siRNA polyplexes enhances endosome escape, stability, blood circulation time, and bioactivity in vivo.
abstract: A family of pH-responsive diblock polymers composed of poly[(ethylene glycol)-b-[(2-(dimethylamino)ethyl methacrylate)-co-(butyl methacrylate)], PEG-(DMAEMA-co-BMA), was reversible addition-fragmentation chain transfer (RAFT) synthesized with 0-75 mol % BMA in the second polymer block. The relative mole % of DMAEMA and BMA was varied in order to identify a polymer that can be used to formulate PEGylated, siRNA-loaded polyplex nanoparticles (NPs) with an optimized balance of cationic and hydrophobic content in the NP core based on siRNA packaging, cytocompatibility, blood circulation half-life, endosomal escape, and in vivo bioactivity. The polymer with 50:50 mol % of DMAEMA:BMA (polymer "50 B") in the RAFT-polymerized block efficiently condensed siRNA into 100 nm NPs that displayed pH-dependent membrane disruptive behavior finely tuned for endosomal escape. In vitro delivery of siRNA with polymer 50 B produced up to 94% protein-level knockdown of the model gene luciferase. The PEG corona of the NPs blocked nonspecific interactions with constituents of human whole blood, and the relative hydrophobicity of polymer 50 B increased NP stability in the presence of human serum or the polyanion heparin. When injected intravenously, 50 B NPs enhanced blood circulation half-life 3-fold relative to more standard PEG-DMAEMA (0 B) NPs (p < 0.05), due to improved stability and a reduced rate of renal clearance. The 50 B NPs enhanced siRNA biodistribution to the liver and other organs and significantly increased gene silencing in the liver, kidneys, and spleen relative to the benchmark polymer 0 B (p < 0.05). These collective findings validate the functional significance of tuning the balance of cationic and hydrophobic content of polyplex NPs utilized for systemic siRNA delivery in vivo.
authors.affiliation: Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Nelson
authors.affiliation: Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA.
authors.forename: James R
authors.initials: JR
authors.lastname: Kintzing
authors.affiliation: Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA.
authors.forename: Ann
authors.initials: A
authors.lastname: Hanna
authors.affiliation: Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA.
authors.forename: Joshua M
authors.initials: JM
authors.lastname: Shannon
authors.affiliation: Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA.
authors.forename: Mukesh K
authors.initials: MK
authors.lastname: Gupta
authors.affiliation: Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, USA.
authors.forename: Craig L
authors.initials: CL
authors.lastname: Duvall
mesh_terms: D001775:Blood Circulation; D002412:Cations; D045744:Cell Line, Tumor; D011992:Endosomes / Q000378:metabolism*; D006207:Half-Life; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D011092:Polyethylene Glycols / Q000737:chemistry*; D034741:RNA, Small Interfering / Q000737:chemistry*; D014018:Tissue Distribution
chemical_list: D002412:Cations; D034741:RNA, Small Interfering; D011092:Polyethylene Glycols
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