Bioinspired, Guanidinium, and Indole Modified Poly(glycidyl ether)s as Highly Efficient Vectors for Polyplex‐Mediated Gene Delivery

Allyl glycidyl ether and 2-methoxyethyl glycidyl ether were copolymerized via anionic ring-opening polymerization and subsequently functionalized with guanidinium and indole groups through a post-polymerization thiol-ene reaction. This modular approach yielded eight polymers with systematically varied hydrophilic-hydrophobic balance, carrying 50-92 mol% guanidinium and 0-22 mol% indole. The polymers featured molar masses between 10.1 and 15.7 kg/mol with a dispersity of around 1.3. Polyplexes were formulated using plasmid DNA and characterized with respect to their physicochemical properties including DNA binding affinity, surface charge, and particle size as well as their transfection efficiencies and polymer in vitro cytotoxicity. All polymers were able to form stable complexes and protected their cargo against enzymatic degradation. An additional hydrophilic monomer did not influence physicochemical characteristics, but increased polymer cytotoxicity. Transfection studies in CHO-K1 cells revealed a strong dependence on polymer hydrophobicity: polymers with medium indole content outperformed both more hydrophilic and more hydrophobic analogues, reaching efficiencies above the gold standard poly(ethylene imine). These results underline the critical role of balancing hydrophilic and hydrophobic groups in side-chain functionalized poly(glycidyl ether)s for safe and effective gene delivery.