title: Synthesis and characterization of mannosylated pegylated polyethylenimine as a carrier for siRNA.
abstract: Regulation of gene expression using small interfering RNA (siRNA) is a promising strategy for research and treatment of numerous diseases. In this study, we develop and characterize a delivery system for siRNA composed of polyethylenimine (PEI), polyethylene glycol (PEG), and mannose (Man). Cationic PEI complexes and compacts siRNA, PEG forms a hydrophilic layer outside of the polyplex for steric stabilization, and mannose serves as a cell binding ligand for macrophages. The PEI-PEG-mannose delivery system was constructed in two different ways. In the first approach, mannose and PEG chains are directly conjugated to the PEI backbone. In the second approach, mannose is conjugated to one end of the PEG chain and the other end of the PEG chain is conjugated to the PEI backbone. The PEI-PEG-mannose delivery systems were synthesized with 3.45-13.3 PEG chains and 4.7-3.0 mannose molecules per PEI. The PEI-PEG-Man-siRNA polyplexes displayed a coarse surface in Scanning Electron Microscopy (SEM) images. Polyplex sizes were found to range from 169 to 357 nm. Gel retardation assays showed that the PEI-PEG-mannose polymers are able to efficiently complex with siRNA at low N/P ratios. Confocal microscope images showed that the PEI-PEG-Man-siRNA polyplexes could enter cells and localized in the lysosomes at 2h post-incubation. Pegylation of the PEI reduced toxicity without any adverse reduction in knockdown efficiency relative to PEI alone. Mannosylation of the PEI-PEG could be carried out without any significant reduction in knockdown efficiency relative to PEI alone. Conjugating mannose to PEI via the PEG spacer generated superior toxicity and gene knockdown activity relative to conjugating mannose and PEG directly onto the PEI backbone.
authors.affiliation: Department of Biomedical Engineering, College of Engineering, The University of Iowa, Iowa City, IA, USA.
authors.forename: Najung
authors.initials: N
authors.lastname: Kim
authors.forename: Dahai
authors.initials: D
authors.lastname: Jiang
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Jacobi
authors.forename: Kim A
authors.initials: KA
authors.lastname: Lennox
authors.forename: Scott D
authors.initials: SD
authors.lastname: Rose
authors.forename: Mark A
authors.initials: MA
authors.lastname: Behlke
authors.forename: Aliasger K
authors.initials: AK
authors.lastname: Salem
mesh_terms: D000818:Animals; D004337:Drug Carriers / Q000009:adverse effects / Q000138:chemical synthesis* / Q000737:chemistry; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D015316:Genetic Therapy / Q000379:methods*; D006801:Humans; D007041:Hypoxanthine Phosphoribosyltransferase / Q000737:chemistry; D008156:Luciferases / Q000737:chemistry; D008358:Mannose / Q000737:chemistry*; D051379:Mice; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D010316:Particle Size; D010957:Plasmids / Q000008:administration & dosage; D011092:Polyethylene Glycols / Q000009:adverse effects / Q000138:chemical synthesis / Q000737:chemistry; D011094:Polyethyleneimine / Q000009:adverse effects / Q000138:chemical synthesis / Q000737:chemistry; D034741:RNA, Small Interfering / Q000008:administration & dosage*; D014162:Transfection
chemical_list: D004337:Drug Carriers; D034741:RNA, Small Interfering; D011092:Polyethylene Glycols; D011094:Polyethyleneimine; D008156:Luciferases; D007041:Hypoxanthine Phosphoribosyltransferase; D008358:Mannose