title: Microfluidic Mixing: A General Method for Encapsulating Macromolecules in Lipid Nanoparticle Systems.
abstract: Previous work has shown that lipid nanoparticles (LNP) composed of an ionizable cationic lipid, a poly(ethylene glycol) (PEG) lipid, distearoylphosphatidylcholine (DSPC), cholesterol, and small interfering RNA (siRNA) can be efficiently manufactured employing microfluidic mixing techniques. Cryo-transmission electron microscopy (cryo-TEM) and molecular simulation studies indicate that these LNP systems exhibit a nanostructured core with periodic aqueous compartments containing siRNA. Here we examine first how the lipid composition influences the structural properties of LNP-siRNA systems produced by microfluidic mixing and, second, whether the microfluidic mixing technique can be extended to macromolecules larger than siRNA. It is shown that LNP-siRNA systems can exhibit progressively more bilayer structure as the proportion of bilayer DSPC lipid is increased, suggesting that the core of LNP-siRNA systems can exhibit a continuum of nanostructures depending on the proportions and structural preferences of component lipids. Second, it is shown that the microfluidic mixing technique can also be extended to encapsulation of much larger negatively charged polymers such mRNA (1.7 kb) or plasmid DNA (6 kb). Finally, as a demonstration of the generality of the microfluidic mixing encapsulation process, it is also demonstrated that negatively charged gold nanoparticles (5 nm diameter) can also be efficiently encapsulated in LNP containing cationic lipids. Interestingly, the nanostructure of these gold-containing LNP reveals a "currant bun" morphology as visualized by cryo-TEM. This structure is fully consistent with LNP-siRNA structure predicted by molecular modeling.
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Alex K K
authors.initials: AK
authors.lastname: Leung
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Yuen Yi C
authors.initials: YY
authors.lastname: Tam
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Sam
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Ismail M
authors.initials: IM
authors.lastname: Hafez
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.
authors.forename: Pieter R
authors.initials: PR
authors.lastname: Cullis
mesh_terms: D020285:Cryoelectron Microscopy; D006046:Gold / Q000737:chemistry; D053768:Metal Nanoparticles; D044085:Microfluidics; D046529:Microscopy, Electron, Transmission; D010713:Phosphatidylcholines / Q000737:chemistry*; D034741:RNA, Small Interfering / Q000737:chemistry
chemical_list: D010713:Phosphatidylcholines; D034741:RNA, Small Interfering; D006046:Gold; C010942:1,2-distearoyllecithin