A Branched Tripeptide with an Anion-Binding Motif as a Novel Delivery Carrier for Efficient Gene Transfection.

Recently, branched and dendrimeric cationic peptides have shown increasing transfection efficiency compared to linear peptides owing to their superior capacity for DNA condensation. Herein, we design and synthesize two analogously guanidinocarbonylpyrrole (GCP)-substituted branched cationic tripeptides, which provide extremely strong electrostatic attraction with plasmid DNA. Both ligands 1 and 2 can bind to plasmid DNA and form condensed complexes owing to the branched structure and high positive charges, as demonstrated by isothermal titration calorimetry (ITC), Zeta-potential and atomic-force microscopy (AFM). Compared with ligand 1, after the replacement of the carboxylate group by an amide group, binding of ligand 2 to DNA shows exothermic enthalpy and positive entropy changes. Rationally, ligand 2 can translocate plasmid pF143 to HEK 293T cells, showing high gene transfection efficiency. Therefore, the branched cationic peptides could serve as powerful tools for gene delivery and have great potential for gene silencing and gene therapy.