Insight into mechanisms of cellular uptake of lipid nanoparticles and intracellular release of small RNAs

Purpose: Understanding mechanisms of cellular uptake and intracellular release would enable better design of nanocarriers for delivery of nucleic acids such as siRNA and MicroRNA (miRNA).

Method: In this study, we investigated cellular pharmacokinetics of siRNA by co-encapsulating fluorescently labeled siRNA and molecular beacon (MB) in four different formulations of cationic lipid nanoparticles (LNPs). A miRNA mimic was also used as a probe for investigating cellular pharmacokinetics, which correlated well with RNAi activities.

Results: We tried to find the best LNP formulation based on the combination of DOTMA and DODMA. When the DOTMA/DODMA ratio was at 5/40, the LNP containing a luciferase siRNA produced the highest gene silencing activity. The superior potency of DOTMA/DODMA could be attributed to higher uptake and improved ability to facilitate siRNA release from endosomes subsequent to uptake.

Conclusions: Our findings may provide new insights into RNAi transfection pathways and have implications on cationic LNP design.