Enhancing the Transgene Performance of Polyethyleneimine through Amino Acid Conjugation

The delivery of nucleic acids requires a gene vector as they are unable to effectively cross cell membranes. Polycations and deoxyribonucleic acid (DNA) can self-assemble into polyplexes enabling intracellular delivery of genetic material. In this framework, we have evaluated the transfection efficiency and cytotoxicity of amino acid-modified branched polyethyleneimine (BPEI). The presence of arginine (Arg), cysteine (Cys) and histidine (His) conjugated to the polymer chains allows for higher transfection capability with lower cytotoxicity compared to the unsubstituted counterpart. BPEI-Arg showed the highest values of transfection efficiency as attributed to its positive charges at nearly neutral pH. The enhanced gene delivery capacity is also linked to the cell-penetrating feature of arginine. The improved efficiency evidenced for BPEI-Cys and BPEI-His is presumably connected to polyplex stabilization due to the formation of bioreducible disulfide bridges, and the protonation of histidine at the intracellular environment. The amino acid modification of branched PEI chains is herein demonstrated to be potentially relevant in ocular gene delivery since human retinal pigment epithelial cells are known to be notoriously difficult to be transfected. This investigation accordingly bridges a gap by combining efficient branched PEI DNA-compacting ability with the superior cell-penetrating properties of arginine, and focused also on potential retinal or corneal therapies.