title: Cellular internalization and gene silencing of siRNA polyplexes by cytocleavable cationic polyrotaxanes with tailored rigid backbones.
abstract: To achieve successful delivery of siRNA therapeutics, cytocleavable cationic polyrotaxanes (PRXs) composed of N,N-dimethylaminoethyl (DMAE) group-modified α-cyclodextrins (CDs) that were threaded onto a poly(ethylene glycol) (PEG) axis and capped with a bulky stopper using cytocleavable disulfide linkages (DMAE-PRX) were utilized as an siRNA carrier. DMAE-PRXs with various numbers of threading CDs and modified DMAE groups were synthesized, and the physicochemical properties, cellular internalization, and gene silencing activity of DMAE-PRX/siRNA were investigated to elucidate the relationship between its supramolecular structure and its function. When the numbers of modified DMAE groups were increased, the DMAE-PRXs formed closely associated polyplexes with siRNA and increased their polyanion exchange resistance. Additionally, the DMAE-PRXs with 52 threading CDs (52CD-PRXs) showed greater binding capabilities with siRNA and greater resistance to polyanion competition than 31CD-PRXs, indicating that the highly CD-threaded PRX structure in the 52CD-PRXs is superior in forming stable polyplexes with siRNA. Indeed, 52CD-PRX/siRNA showed greater intracellular uptake of siRNA than 31CD-PRX/siRNA with comparable numbers of DMAE groups. 52CD-PRX/siRNA successfully induced gene silencing of a targeted luciferase expressed in human cervical carcinoma without marked cytotoxicity and non-specific gene silencing. Although the gene silencing activities of DMAE-PRX/siRNA were comparable to those of linear poly(ethylenimine) (L-PEI), L-PEI showed cytotoxicity and non-specific gene silencing. Additionally, DMAE-PRXs with cytocleavable capabilities were found to enhance gene silencing, in comparison with non-cleavable DMAE-PRX. Thus, the cytocleavable cationic PRXs are suggested to be attractive supermolecules for the delivery of therapeutic siRNAs.
authors: Institute of Biomaterials and Bioengineering, Tokyo Medical and Dental University, Tokyo, Japan.
authors: Atsushi
authors: A
authors: Tamura
authors: Nobuhiko
authors: N
authors: Yui
mesh_terms: D020868:Gene Silencing; D008956:Models, Chemical; D011092:Polyethylene Glycols / Q000737:chemistry; D034741:RNA, Small Interfering / Q000235:genetics*; D043862:Rotaxanes / Q000737:chemistry*
chemical_list: D034741:RNA, Small Interfering; D043862:Rotaxanes; D011092:Polyethylene Glycols