title: Mechanistic investigation of poly(ethylene imine)-based siRNA delivery: disulfide bonds boost intracellular release of the cargo.
abstract: Poly(ethylene imine) (PEI) has gained increasing attention in the delivery of small interfering RNAs (siRNAs) into cells. In order to further optimize PEI for this application, the first goal of this study was to examine particular steps of siRNA delivery with various PEI derivatives as carriers. Furthermore, the hypothesis that disulfide cleavable carrier systems are favorable for the release of siRNA into the cell cytoplasm was investigated. Flow cytometry and confocal microscopy were used to assess the cellular uptake and intracellular distribution of siRNA, which were then related to gene silencing efficacy. We observed a strong correlation between cellular uptake and RNAi activity. The cellular uptake of siRNA was more efficient with increasing branching of the polymer, i.e. linear PEI (lPEI) 5 kDa < lPEI cross-linked via disulfide bonds (ssPEI) < branched PEI (bPEI) 25 kDa. However, it was also evident that the siRNA release from the carrier, which was promoted by ssPEI, played an important role in the accessibility of siRNA for the gene silencing complex. Therefore, we suggest that a combination of a high branching density and reductively cleavable bonds within the PEI-based carrier system could be one possible step towards improving siRNA delivery.
authors.affiliation: Department of Pharmaceutical Technology, University of Regensburg, Regensburg, Germany.
authors.forename: Miriam
authors.initials: M
authors.lastname: Breunig
authors.forename: Constantin
authors.initials: C
authors.lastname: Hozsa
authors.forename: Uta
authors.initials: U
authors.lastname: Lungwitz
authors.forename: Kazuo
authors.initials: K
authors.lastname: Watanabe
authors.forename: Isao
authors.initials: I
authors.lastname: Umeda
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kato
authors.forename: Achim
authors.initials: A
authors.lastname: Goepferich
mesh_terms: D000818:Animals; D016466:CHO Cells; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D004220:Disulfides / Q000737:chemistry*; D004337:Drug Carriers / Q000737:chemistry*; D005434:Flow Cytometry; D018014:Gene Transfer Techniques; D049452:Green Fluorescent Proteins / Q000235:genetics; D007097:Imines / Q000737:chemistry*; D018613:Microscopy, Confocal; D010316:Particle Size; D011095:Polyethylenes / Q000737:chemistry*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000235:genetics; D014162:Transfection
chemical_list: D004220:Disulfides; D004337:Drug Carriers; D007097:Imines; D011095:Polyethylenes; D034741:RNA, Small Interfering; C505405:poly(ethylene imine); D049452:Green Fluorescent Proteins