Fibroblast-Selective Lipid Nanoparticles for Tumor Stromal Transfection

Fibroblasts are abundant and functionally diverse components of the tumor microenvironment and have emerged as attractive targets for stromal modulation in solid tumors. However, selective gene delivery to fibroblasts remains challenging due to their heterogeneity and close spatial association with tumor and immune cells, particularly when using ligand-free lipid nanoparticle (LNP)-based delivery systems. In this study, we applied a selectivity-driven screening approach to identify LNP formulations that preferentially transfect fibroblasts based on lipid composition. Systematic variation of clinically relevant ionizable and helper lipids identified specific LNP compositions that consistently favored fibroblast-selective mRNA expression. In vitro analysis showed that specific lipid compositions conferred preferential transgene expression in fibroblasts, which was maintained under competitive tumor cell-fibroblast coculture conditions. Consistent with these findings, peritumoral administration of optimized LNPs in tumor-bearing mice demonstrated preferential mRNA expression in stromal fibroblasts within the tumor microenvironment. These results establish the lipid composition of LNPs as a key determinant of fibroblast-selective mRNA expression across in vitro, coculture, and peritumoral in vivo models.