Cationic
liposomes composed of dialkyl cationic
lipid such as 1,2-dioleoyl-3-trimethylammonium-propane (
DOTAP) can efficiently deliver
siRNA to the lungs following the
intravenous injection of cationic
liposome/
siRNA complexes (lipoplexes). In this study, we examined the effect of cationic
lipid of cationic
liposomes on
siRNA delivery to the lungs after
intravenous injection. We used six kinds of cationic
cholesterol derivatives and 11 kinds of dialkyl or trialkyl cationic
lipids as cationic
lipids, and prepared 17 kinds of cationic
liposomes composed of a cationic
lipid and 1,2-dioleoyl-L-α-glycero-3-phosphatidylethanolamine (DOPE) for evaluation of
siRNA biodistribution and in vivo gene silencing effects. Among cationic
liposomes, those composed of N-hexadecyl-N,N-dimethylhexadecan-1-aminium
bromide (DC-1-16), N,N-dimethyl-N-octadecyloctadecan-1-aminium
bromide (DC-1-18), 2-((1,5-bis(octadecyloxy)-1,5-dioxopentan-2-yl)amino)-N,N,N-trimethyl-2-oxoethan-1-aminium
chloride (DC-3-18D), 11-((1,3-bis(dodecanoyloxy)-2-((dodecanoyloxy)methyl)propan-2-yl)amino)-N,N,N-trimethyl-11-oxoundecan-1-aminium
bromide (TC-1-12), or cholesteryl (3-((2-hydroxyethyl)amino)propyl)carbamate hydroiodide (HAPC-Chol) with DOPE exhibited high accumulation of
siRNA in the lung and significant suppression of Tie2
mRNA expression after the
intravenous injection of cationic lipoplexes with Tie2
siRNA. Furthermore, DC-1-16/DOPE and DC-1-18/DOPE lipoplexes with
protein kinase N3 (PKN3)
siRNA could suppress the tumour growth when intravenously injected into mice with lung LLC
metastasis. These findings indicate that the
siRNA biodistribution and in vivo knockdown efficiency after the
intravenous injection of cationic lipoplexes were strongly affected by the type of cationic
lipid of cationic
liposomes.