Incorporation of disulfide bonds into ionizable lipids enables efficient splenic mRNA delivery and potent immunotherapy in mice

The application of mRNA-based therapies has gained significant attention in recent years, with lipid nanoparticles (LNPs) emerging as key delivery vehicles. However, challenges remain in optimizing delivery efficiency and targeting tissues beyond the liver, particularly for immunotherapy. In this study, we constructed novel lipids with disulfide bonds in the linkers and utilized the redox responsiveness of these bonds in the reductive microenvironment of tumor or immune cells to enable robust splenic mRNA delivery and potent cancer immunotherapy. A library of 119 lipids was synthesized by conjugating hydrophilic amines, disulfide-containing linkers, and hydrophobic amines via sequential aza-Michael addition. In vitro screening identified lipids with longer, branched hydrophobic tails, particularly 2C10, as leading carriers for mRNA delivery. Compared to conventional LNPs without disulfide linkers, disulfide-containing LNPs showed smaller size, higher mRNA binding, and enhanced mRNA release in the presence of GSH, with predominantly spleen-targeted in vivo delivery. Encapsulation with OVA mRNA promoted CD4 + and CD8 + T cell differentiation, leading to significant tumor regression in a melanoma mouse model. These findings highlight the potential of redox-responsive LNPs for targeted mRNA delivery and cancer immunotherapies.