Synthesis and characterization of methylated poly(L-histidine) to control the stability of its siRNA polyion complexes for RNAi.
Poly(L-histidine) (PLH) with dimethylimidazole groups has been synthesized as a pH-sensitive polypeptide to control the stability of its small interfering RNA (siRNA) polyion complexes for RNA interference (RNAi). The resulting methylated PLH (PLH-Me) was water-soluble despite deprotonation of the imidazole groups at physiological pH, as determined by acid-base titration and solution turbidity measurement. Agarose gel retardation assay proved that the quaternary dimethylimidazole groups worked as cationic groups to retain siRNA. The stability of the PLH-Me/siRNA complexes has depended on the content of hydrophobic groups, that is, τ/π-methylimidazole groups as well as deprotonated imidazole groups. PLH-Me exhibited no significant cytotoxicity despite the existence of cationic dimethylimidazole groups. By use of PLH-Me as a pH-sensitive siRNA carrier, the PLH-Me/siRNA complexes mediated efficient siRNA delivery attributed to the dimethylimidazole groups, and the gene silencing depended on the content balance among dimethyl, τ/π-methyl, and unmodified imidazole groups. These results suggest that PLH-Me controls the stability of siRNA polyion complexes by enhancing noncytotoxic siRNA delivery by optimizing the content balance of dimethyl, τ/π-methyl, and unmodified imidazole groups.
Department of Applied Chemistry, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan. asayama-shoichiro@tmu.ac.jp
Shoichiro
S
Asayama
Takao
T
Kumagai
Hiroyoshi
H
Kawakami
D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D056945:Hep G2 Cells; D006639:Histidine / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D008745:Methylation; D015394:Molecular Structure; D034622:RNA Interference / Q000187:drug effects; D034741:RNA, Small Interfering / Q000737:chemistry*; D013329:Structure-Activity Relationship
D007093:Imidazoles; D007477:Ions; D034741:RNA, Small Interfering; C033223:polyhistidine; D006639:Histidine