Chemistry of Lipid Nanoparticles for RNA Delivery

Abstract

Metrics & MoreArticle Recommendations CONSPECTUS: Lipid nanoparticles (LNPs) are a type of lipid vesicles that possess a homogeneous lipid core. These vesicles are widely used in small-molecule drug and nucleic acid delivery and recently gained much attention because of their remarkable success as a delivery platform for COVID-19 mRNA vaccines. Nonetheless, the utility of transient protein expression induced by mRNA extends far beyond vaccines against infectious diseasesthey also hold promise as cancer vaccines, protein replacement therapies, and gene editing components for rare genetic diseases. However, naked mRNA is inherently unstable and prone to rapid degradation by nucleases and self-hydrolysis. Encapsulation of mRNA within LNPs protects mRNA from extracellular ribonucleases and assists with intracellular mRNA delivery.In this Account, we discuss the core features of LNPs for RNA delivery. We focus our attention on LNPs designed to deliver mRNA; however, we also include examples of siRNA-LNP delivery where appropriate to highlight the commonalities and the dissimilarities due to the nucleic acid structure. First, we introduce the concept of LNPs, the advantages and disadvantages of utilizing nucleic acids as therapeutic agents, and the general reasoning behind the molecular makeup of LNPs. We also briefly highlight the most recent clinical successes of LNP-based nucleic acid therapies. Second, we describe the theory and methods of LNP self-assembly. The common idea behind all of the preparation methods is inducing electrostatic interactions between the nucleic acid and charged lipids and promoting nanoparticle growth via hydrophobic interactions. Third, we break down the LNP composition with special attention to the fundamental properties and purposes of each component. This includes the identified molecular design criteria, commercial sourcing, impact on intracellular trafficking, and contribution to the properties of LNPs. One of the key components of LNPs is ionizable lipids, which initiate electrostatic binding with endosomal membranes and facilitate cytosolic release; however, the roles of other lipid components should not be disregarded, as they are associated with stability, clearance, and distribution of LNPs. Fourth, we review the attributes of LNP constructs as a whole that can heavily influence RNA delivery. These attributes are LNP size, charge, internal structure, lipid packing, lipid membrane hydration, stability, and affinity toward biomacromolecules. We also discuss the specific techniques used to examine these attributes and how they can be adjusted. Finally, we offer our perspective on the future of RNA therapies and some questions that remain in the realm of LNP formulation and optimization.

Carrier strategies boost the application of CRISPR/Cas system in gene therapy

“…[141] The use of LNPs for non-gene-editing mRNA delivery has been extensively reviewed elsewhere. [107,142] Here, we mainly review significant advances of lipid-based carriers in Cas9 mRNA delivery.…”

Next RNA Therapeutics: The Mine of Non-Coding

“…RNA is a hydrophilic and negatively charged molecule, so it has difficulties to enter in naked form into the cells because of electrostatic repulsion. This is why it needs some appropriate vehicles to penetrate target cells and gain function [96].…”

“…Lipid nanovesicles are small vesicles that recently gained great success as vehicles for RNA vaccines (e.g., COVID-19 vaccines) [97]. They are characterized by the presence of lipids that mimic the cell membrane, and PEG-lipids (polyethylene glycol-anchored lipids) to prevent the interaction with environmental elements [96]. Indeed, the advantage of PEG-lipid addition is the improvement of circulation time for liposome-encapsulated (LNP) drugs and the reduction in non-specific uptakes.…”

The Future of Tissue-Targeted Lipid Nanoparticle-Mediated Nucleic Acid Delivery

“…Formulating therapeutic nucleic acids into nanoparticles is of utmost importance to prevent degradation by nucleases upon administration and to enhance cellular uptake of these negatively charged entities. The current state of the art for therapeutic nucleic acid delivery is lipid nanoparticles (LNP), which are composed of cholesterol, a helper lipid, a PEGylated lipid and an ionizable amine-containing lipid ( Figure 1 ) [ 3 ]. The cholesterol and helper lipids are important for the integrity of the LNP, while the PEGylated lipid provides colloidal stability as well as stealth properties to limit accumulation in the reticuloendothelial system (RES).…”