A serum-resistant polyamidoamine-based polypeptide dendrimer for gene transfection

Abstract A serum tolerant polycation gene vector, G2 PAMAM-PGlu-G1 PAMAMs (ALA), was designed, synthesized, characterized and evaluated. A honeycomb-like molecular structure model for mechanistic explanation of ALA was postulated and discussed. Designed as a star-shaped polyamidoamine (PAMAM)-based polypeptide dendrimer through peptide bond linkages, ALA was with non-toxic low generation G2 PAMAM (G2 ) as its central core, polyglutamate (PGlu)s as its star-shaped backbone branches and G1 PAMAM (G1 )s as its branch grafts and peripheral terminals. IR,1 H NMR demonstrated its successful combination. As a gene carrier, ALA exhibited good DNA binding and condensation capacity with particle size (∼87 nm for N/P 40, ∼170 nm for N/P 30) and ζ-potential (∼16 mV for N/P 30–40), negligible cytotoxicity, exciting serum tolerant capacity and significant serum-promoted (serum-containing 56.6%>serum-free 32.7%), cell line dependent (Hek 293 > Bel 7402 > Hela), incubation period dependent (38 h > 18 h > 12 h > 9 h > 4 h > 2 h > 1 h) and sustained (peak transfection appeared at 30 h incubation) transfection efficiency. The presence of serum had not only no inhibition on, but also prominent promotion to, the transfection activity of ALA. All above features differentiated ALA clearly from most other serum-inhibitive nonviral gene carriers, and proved ALA the promising and challenging potential efficient gene vector for practical clinical application.