Characterization of the Physiochemical Interactions Between LNPs and the Endosomal Lipids: A Rational Design of Gene Delivery Systems

Lipid nanoparticles (LNPs) are a class of materials, with each interacting in a complex fashion to form specialized bio-containers carrying therapeutic drugs and strands of nucleic acids such as small interfering RNA (siRNA)1. LNPs are at the forefront of the rapidly developing field of nanotechnology with several potential applications in drug delivery, clinical medicine, and research. Despite holding a significant promise for reaching the goal of controlled and site specific drug delivery, the engineering of efficient LNPs is limited by the lack of knowledge about the structure of LNPs, the roles of their individual components and the physical interactions with other biomolecules2. Because of this, characteristics such as the encapsulation efficiency, polydispersity, and stability of LNPs are not predictable. One of the biggest problems of LNP gene therapy is the molecular details of the cellular processes that determine the efficiency of intracellular drug delivery is still unclear. Studies have shown that LNPs enter cells via the endocytic pathway and are engulfed by endosomes. The delivery of siRNA is substantially reduced, as ∼70% of the internalized siRNA undergoes exocytosis through egress of LNPs from late endosomes/lysosomes3. In this project, we used advanced molecular dynamics simulations to understand the molecular basis of the structure of LNPs based on their composition. Our simulations also provided the first detailed molecular-level view of the interactions of the LNP components with endosomal lipids. Here, we also studied the change in interactions between the LNPs and endosomal lipids by varying ion concentration and altering pH. Results of our simulation will provide a route to the rational design of new LNPs that address safety concerns and ensure effective delivery to accelerate the translation of engineering lipid-based nanoparticles towards the clinic. References 1. Semple, S.C., et al. (2010) Rational design of cationic lipids for siRNA delivery. Nat.Biotechnol. 28,172-176 2. Huang, L. and Liu, Y. (2011) In vivo delivery of RNAi with lipid-based nanoparticles. Annu.Rev.Biomed. Eng. 13, 507-530 3. Sahay G., et al. (2013) Efficiency of siRNA delivery by lipid nanoparticles is limited by endocytic recycling. Nat.Biotechnol. 31,653-658.