Dual Ethanolamine Head Groups in Ionizable Lipids Facilitate Phospholipid-free Stable Nanoparticle Formulation for Augmented and Safer mRNA Delivery

The accelerated advent of mRNA-based therapeutics and vaccines, highlighted by the battle against SARS-CoV-2, underscores the urgency to refine lipid nanoparticles (LNPs) for efficient mRNA delivery. In this work, we introduce a novel series of ionizable lipids characterized by double ethanolamine head groups, significantly amplifying mRNA binding affinity. A succinct three-component formulation is subsequently delineated, obviating the conventional dependency on phospholipids inherent in traditional four-component LNPs. Intriguingly, this formulation enables particle formation under neutral pH conditions, a notable departure from the acidic milieu traditionally required, attributable to the enhanced nonionic interactions predominating in mRNA encapsulation. The resultant particles exhibit exceptional stability, superior mRNA encapsulation efficiency, and maintain robust delivery efficacy. When deployed as a vaccine platform, the formulation elicited pronounced humoral and T-cell immune responses, concurrently exhibiting a favorable toxicity profile with a reduced induction of pro-inflammatory cytokines such as IL-6. Our exploration suggests that by fine-tuning the non-electrostatic interactions between the ionizable lipid and mRNA, the dynamics of particle formation can be considerably divergent from the prevailing paradigms of mRNA-LNP formation, hinting at a broader horizon for lipid optimization within the realm of mRNA delivery systems.