title: Nonviral siRNA delivery to the lung: investigation of PEG-PEI polyplexes and their in vivo performance.
abstract: This study describes the physicobiological characterization of PEI- and PEG-PEI polyplexes containing partially 2'-OMe modified 25/27mer dicer substrate siRNAs (DsiRNAs) and their in vivo behavior regarding biodistribution and systemic bioavailability after pulmonary application as well as their ability to knock down gene expression in the lung. Biophysical characterization included circular dichroism of siRNA in polyplexes, condensation efficiency of polymers and in vitro stability. After in vivo application, biodistribution and kinetics of radiolabeled polyplexes were quantified and recorded over time in three-dimensional SPECT images and by end point scintillation counting. The influence on lung tissue and on the humoral and cellular immunosystem was investigated, and finally knockdown of endogenous gene expression in the lung was determined qualitatively. While all of the polymers used in our study were proven to effectively condense siRNA, stability of the complexes depended on the PEG grafting degree. Interestingly, PEI 25 kDa, which showed the least interaction with mucin or surfactant in vitro, performed poorly in vivo. Our nuclear imaging approach enabled us to follow biodistribution of the instilled nanocarriers over time and indicated that PEGylated nanocarriers are more suitable for lung application. While moderate proinflammatory effects were attributed to PEI25k-PEG(2k)(10) nanocarriers, none of the treatments caused histological abnormalities. Our preliminary in vivo knockdown experiment suggests that PEG-PEI/siRNA complexes are promising nanomedicines for pulmonary siRNA delivery. These results encouraged us to further investigate possible adverse effects and to quantify in vivo gene silencing in the lung after intratracheal instillation of PEG-PEI/siRNA complexes.
authors.affiliation: Department of Pharmaceutics and Biopharmacy, Philipps Universitat Marburg, Ketzerbach 63, 35032 Marburg, Germany.
authors.forename: Olivia M
authors.initials: OM
authors.lastname: Merkel
authors.forename: Andrea
authors.initials: A
authors.lastname: Beyerle
authors.forename: Damiano
authors.initials: D
authors.lastname: Librizzi
authors.forename: Andreas
authors.initials: A
authors.lastname: Pfestroff
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Behr
authors.forename: Brian
authors.initials: B
authors.lastname: Sproat
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Barth
authors.forename: Thomas
authors.initials: T
authors.lastname: Kissel
mesh_terms: D000818:Animals; D001992:Bronchoalveolar Lavage Fluid; D002942:Circular Dichroism; D016503:Drug Delivery Systems; D005434:Flow Cytometry; D055785:Gene Knockdown Techniques; D049452:Green Fluorescent Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008168:Lung / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D009077:Mucins / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry*; D011094:Polyethyleneimine / Q000737:chemistry*; D034741:RNA, Small Interfering / Q000008:administration & dosage* / Q000493:pharmacokinetics; D014018:Tissue Distribution
chemical_list: D009077:Mucins; D034741:RNA, Small Interfering; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D011092:Polyethylene Glycols; D011094:Polyethyleneimine