Abstract: OBJECTIVE:To investigate pharmacokinetics siRNA drugs in vivo and to analyze advantages of liposomes as drug carriers. METHODS:A previously constructed siRNA expression plasmid was loaded into nano-invisible cationic liposomes and used for investigations:bare siRNA plasmid group and siRNA plasmid liposomes group. DNase I digestion and serum stability were evaluated. Then,20 μg bare plasmid siRNA and liposome siRNA plasmid were injected into mice through their tail veins,and blood samples were collected at 0 min,5 min,15 min,30 min,1 h,2 h,4 h,12 h,and 24 h,respectively. Quantitative real-time PCR (qPCR) was used to quantitatively detect liposomes in mice,and the concentrations of siRNA plasmid at each time point was calculated. RESULTS:The bare plasmids were completely degraded in DNaseⅠwithin 20 min,and the degradation of plasmid liposomes was slow,with (20.16±2.47)% DNA remaining at 24 h. The bare plasmid only remained (11.03±0.92)% at 20 min in 80% serum,and was basically degraded at 1 h. The plasmid liposomes remained (10.26±1.04)% at 24 h in 80% serum. The stability of siRNA expression plasmid in DNaseⅠand serum was significantly improved by using liposomes as a carrier (P<0.05). The half-life of liposomal encapsulated plasmids in mice was about 2 h,while that of naked plasmids was only 6 min,and the difference was statistically significant (P<0.05). CONCLUSION:In vivo detection of siRNA liposomes can be accomplished by qPCR. Cationic liposomes can protect nucleic acid drugs inside the body,which is an efficient delivery carrier. At the same time,liposomes can improve stability of drugs in vivo and prolong the action time of drugs.

Key words: siRNA, cationic liposomes, in vivo stability, nucleic acid quantitative detection, pharmacokinetics