Purpose: To determine the influence of physicochemical properties of lipid nanoparticles (LNPs) carrying siRNA on their gene silencing in vivo. Mechanistic understanding of how the architecture of the nanoparticle can alter gene expression has also been studied.
Methods: The effect of 3-N-[(ω-methoxypoly(ethylene glycol)2000)carbamoyl]-1,2-dimyristyloxy-propylamine (PEG-C-DMA) on hepatic distribution and FVII gene silencing was determined. FVII mRNA in hepatocytes and liver tissues was determined by Q-PCR. Hepatic distribution was quantified by FACS analysis using Cy5 labeled siRNA.
Results: Gene silencing was highly dependent on the amount of PEG-C-DMA present. FVII gene silencing inversely correlated to the amount of PEG-C-DMA in LNPs. High FVII gene silencing was obtained in vitro and in vivo when the molar ratio of PEG-C-DMA to lipid was 0.5 mol%. Surprisingly, PEGylation didn't alter the hepatic distribution of the LNPs at 5 h post administration. Instead the amount of PEG present in the LNPs has an effect on red blood cell disruption at low pH.
Conclusion: Low but sufficient PEG-C-DMA amount in LNPs plays an important role for efficient FVII gene silencing in vivo. PEGylation did not alter the hepatic distribution of LNPs, but altered gene silencing efficacy by potentially reducing endosomal disruption.