Effect of the nanoformulation of siRrNAa-lipid assemblies on their cellular uptake and immune stimulation

Kohei Kubota, Kohei Onishi, Kazuaki Sawaki, Tianshu Li, Kaoru Mitsuoka, Takaaki Sato, Shinji Takeoka*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)


Two lipid-based nanoformulations have been used to date in clinical studies: lipoplexes and lipid nanoparticles (LNPs). In this study, we prepared small interfering RNA (siRNA)-loaded carriers using lipid components of the same composition to form molecular assemblies of differing structures, and evaluated the impact of structure on cellular uptake and immune stimulation. Lipoplexes are electrostatic complexes formed by mixing preformed cationic lipid liposomes with anionic siRNA in an aqueous environment, whereas LNPs are nanoparticles embedding siRNA prepared by mixing an alcoholic lipid solution with an aqueous siRNA solution in one step. Although the physicochemical properties of lipoplexes and LNPs were similar except for small increases in apparent size of lipoplexes and zeta potential of LNPs, siRNA uptake efficiency of LNPs was significantly higher than that of lipoplexes. Furthermore, in the case of LNPs, both siRNA and lipid were effectively incorporated into cells in a co-assembled state; however, in the case of lipoplexes, the amount of siRNA internalized into cells was small in comparison with lipid. siRNAs in lipoplexes were thought to be more likely to localize on the particle surface and thereby undergo dissociation into the medium. Inflammatory cytokine responses also appeared to differ between lipoplexes and LNPs. For tumor necrosis factor-a, release was mainly caused by siRNA. On the other hand, the release of interleukin-1β was mainly due to the cationic nature of particles. LNPs released lower amounts of tumor necrosis factor-a and interleukin-1β than lipoplexes and were thus considered to be better tolerated with respect to cytokine release. In conclusion, siRNA-loaded nanoformulations effect their cellular uptake and immune stimulation in a manner that depends on the structure of the molecular assembly; therefore, nanoformulations should be optimized before extending studies into the in vivo environment.

Original languageEnglish
Pages (from-to)5121-5133
Number of pages13
JournalInternational Journal of Nanomedicine
Publication statusPublished - 2017 Jul 19


  • Confocal microscopy
  • Cryo-TEM
  • Endocytosis
  • Immune stimulation
  • Nanoformulation
  • SiRNA

ASJC Scopus subject areas

  • Biophysics
  • Bioengineering
  • Biomaterials
  • Pharmaceutical Science
  • Drug Discovery
  • Organic Chemistry


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