Intracellular delivery of mRNA represents one of the greatest challenges due to the fragility of mRNA and the difficulty to destabilize the endosomal membrane. One of the most advanced non-viral delivery systems for mRNA are lipid nanoparticles (LNPs). COVID-19 vaccines are the first ones using the mRNA-LNP technology and this resulted in the first-time approval of mRNA-based vaccines. LNPs consist of multiple components: (a) ionizable lipids, (b) cholesterol, (c) phospholipids and (d) PEG-lipids. Ionizable lipids are supposed to be the main driver to determine LNP efficacy and safety. To minimize toxicity, they are neutrally charged at physiological pH. At acidic pH in endosomes they become positively charged and are able to interact with endosomal phospholipids to convert the bilayer structure into a hexagonal HII phase. This hexagonal HII phase disrupts the lipid bilayer and is associated with membrane fusion and membrane disruption resulting in the release of mRNA. Cholesterol is involved in the LNP structure and endosomal escape. Phospholipids on the other hand contribute to LNP stability and endosomal escape whereas hydrophilic PEG-lipids are needed to stabilize the LNPs during manufacturing and storage. Here we focused on the synthesis of a novel library of ionizable lipids with (a) degradable moieties that degrade in response to the intracellular milieu that is sensed by LNP upon endocytosis (b) ionizable amines that are able to complex mRNA as well as destabilize endosomal membranes and (c) a variety of alkyl chains to enhance nanoparticle stabilization and to promote endosomal escape. Based on this novel library of ionizable lipids, mRNA nanoparticle formulations were made and physicochemical properties (size, zeta potential, encapsulation, pKa) were assessed. All formulations were tested in vitro on different types of cell lines to evaluate their toxicity, endocytosis and mRNA expression. The best performing ionizable lipids based on in vitro data were chosen to be tested in vivo to evaluate their safety profile and biological activity profile.

A novel library of degradable ionizable lipids for mRNA immunotherapy

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.