Peptide-grafted dextran vectors for efficient and high-loading gene delivery

Among various polymeric gene delivery systems, peptide-based vectors demonstrate great potential owing to their unique structure and properties, including flexibility; however, there is insufficient molecular understanding of the role and properties of amino acids as building blocks in gene delivery. In this work, we constructed a series of histidine (H)-containing peptide-grafted dextran (D-RxHy) vectors via a simple two-step reaction of dextran with five RxHyC peptides: R7H3C, R5H3C, R5H5C, R3H5C, and R3H7C. The gel electrophoresis study unveiled the DNA-binding ability of H residues. While all D-RxHy vectors possess similarly low cytotoxicity, D-R3H7 exhibited the highest gene transfection efficiency. Interestingly, at the low nitrogen to phosphate (N/P) ratio of 2, D-R3H7 displayed a 6–8-fold higher luciferase expression compared to the gold standard branched PEI (25k). D-R3H7 and D-R5H5 demonstrated favorable cell uptake rates. A chloroquine-treated transfection assay confirmed the key effect of the high buffering capacity of H-rich D-R3H7 on its high gene transfection efficiency, especially at low N/P ratios. The present work unveiled that histidine is critical for both DNA condensation and the accurate control of endosomal escape. The tunable D-RxHy platform not only demonstrates promising potential for therapeutic purposes but can also be used as a tool to elucidate the molecular mechanism of polymer-based transfection.