Virus-inspired disulfide engineering enables gene delivery via remodeling of cellular uptake and organ distribution.

Efficient cytosolic delivery remains a central challenge in the clinical translation of gene therapeutics. Inspired by viral strategies, we explored disulfide chemistry as a structural lever to enhance cellular uptake and intracellular trafficking. We systematically incorporated disulfide moieties into the poly(β-amino ester)s (PAEs) backbone to generate a series of PAEs with different disulfide content. These minimalist backbone modifications significantly reprogrammed the cellular uptake route through thiol-mediated internalization. Furthermore, we found that backbone disulfide incorporation increases polymer chain flexibility, enabling the carrier to differentially package genetic cargoes based on their intrinsic rigidity. While the rigid, double stranded plasmid DNA remained primarily sequestered in the lungs, the more flexible single stranded messenger RNA formed more compact polyplexes that effectively shifted gene expression to the spleen. Such cargo dependent redistribution was absent in disulfide free systems, highlighting the role of backbone flexibility in redefining the in vivo identity of the carrier. Together, this work establishes backbone disulfide engineering as a virus-inspired and tunable design strategy for programmable gene delivery and control over organ-specific distribution.