Tuning gradient steepness in copolymers augments intracellular pDNA Delivery

Therapeutic nucleic acids promise to improve the lives of millions of people suffering from genetic disorders. However, nucleic acids confront intracellular delivery barriers such as cellular uptake, endolysosomal processing, or nuclease-mediated degradation, which curtail their therapeutic functionality. Engineered viral vectors can overcome these challenges but are difficult to manufacture at scale & prohibitively expensive. Polymers, in contrast, can be economically mass-produced & designed to minimize immune responses. Synthetic advances, particularly in reversibly deactivated radical polymerization, help chemists access arbitrary combinations of compositions, lengths, architectures, and repeat unit spatial distributions, offering unprecedented control over polymer properties. Here, we demonstrate that the spatial distribution of lipophilic cations governs the complexation pathways, serum stability, & biological performance of polymer–pDNA complexes. We engineered gradient copolymers that combine the polyplex colloidal stability of block copolymers with the transfection efficiency of statistical copolymers. We synthesized length & compositionally equivalent gradient copolymers G1–G3 along with statistical (S) & block (B) copolymers of 2-(diisopropylamino)ethyl methacrylate & 2-hydroxyethyl methacrylate. Our work demonstrates that gradient polymerization is a powerful & under-utilized tool to optimize multiple design objectives in polycation-mediated nucleic acid delivery.