Charge-Mixed Nanogels Enable Enhanced Efficacy and Reduced Cytotoxicity in siRNA Delivery

Cationic nanogels represent a distinctive class of polymeric vectors for siRNA delivery; however, their applications are constrained by a fundamental trade-off between efficacy and cytotoxicity. In this study, we designed an innovative charge-mixed nanogel to tackle this dilemma. Using a robust electrostatic templated polymerization (ETP) method, we synthesized a library of cationic nanogels with precisely regulated charge composition, size, and cross-linking degree. A systematic investigation elucidated their effects on delivery efficacy and cytotoxicity reduction. Specifically, the charge, size, and cross-linking degree of the nanogels cooperatively regulate their delivery efficiency, while the reduction in cytotoxicity relies primarily on the dilution of positive charge through the incorporation of ionic units into the cationic network. The established structure-activity relationship led to the identification of an optimal formulation consisting of 80% cationic units and 20% anionic groups, with a hydrodynamic radius of approximately 83 nm and a 20% cross-linking degree using a disulfide cross-linker. This design promotes intracellular GSH-responsive dissociation of the nanogels and subsequent siRNA release. We demonstrate that the engineered charge-mixed nanogels facilitate excellent cellular uptake (4.4 times that of Lipo 3000) and superior silencing efficiency while significantly reducing cytotoxicity. Our study provides both instructive design principles for cationic nanocarriers and a promising vector that reconciles high delivery potency with excellent biocompatibility for advanced siRNA therapeutics.