Abstract
Lipid nanoparticles (LNPs) are the most clinically relevant vehicles for mRNA vaccines. Despite the great successes, the toxicity caused by the high dose of lipid components still represents a great challenge. The suboptimal loading capacity of mRNA in LNPs not only compromises the vaccine's efficacy but also heightens the risk of non-specific immune responses, accelerates clearance caused by anti-PEG IgG/IgM. These problems underscore the urgent need for improving mRNA loading capacity in LNPs to provide dose-sparing effects. Herein, we develop a metal ion mediated mRNA enrichment strategy to efficiently form a high-density mRNA core, and manganese ion (Mn2+) exhibits a unique capability to match the need. The prepared Mn-mRNA nanoparticle is subsequently coated with lipids to form the resulting nanosystem, L@Mn-mRNA, which achieved nearly twice the mRNA loading capacity compared to conventional mRNA vaccine formulations (LNP-mRNA). Remarkably, L@Mn-mRNA also demonstrates a 2-fold increase in cellular uptake efficiency compared to LNP-mRNA, attributed to the enhanced stiffness provided by the Mn-mRNA core. By combining improved mRNA loading with superior cellular uptake, L@Mn-mRNA achieves significantly enhanced antigen-specific immune responses and therapeutic efficacy as vaccines. We elucidate the mechanism behind Mn-mRNA construction and optimize the L@Mn-mRNA formulations, and this method is suitable for types of lipids and mRNAs. Moreover, L@Mn-mRNA also reduces the risk of anti-PEG IgG/IgM generation. Thus, this strategy holds significant potential as a platform for the next generation of lipid-based mRNA vaccines.