University of Pennsylvania engineers redesigned ionizable lipids to create aromatic, bioreducible lipid nanoparticles (aroLNPs) that reduce liver accumulation and preferentially deliver mRNA to lymph nodes in mice. The JACS‑published work showed roughly tenfold less liver delivery compared with a Moderna‑style ionizable lipid while maintaining robust lymph‑node transfection and antigen‑specific immunity. Authors highlighted modular chemistry and disulfide biodegradability as keys to tuning tropism. The finding provides a delivery strategy to improve vaccine potency and safety by concentrating antigen expression in immune‑training sites rather than the liver.