Disulfide cross-linked low generation dendrimers with high gene transfection efficacy, low cytotoxicity, and low cost.

Cationic poly(amidoamine) (PAMAM) dendrimers were widely used as nonviral gene carriers. PAMAM dendrimer-based products such as Superfect and Priofect were already commercially available gene transfection reagents. However, these products are based on high generation dendrimers with high cost and serious cytotoxicity. In this study, we prepared high efficient gene carriers using disulfide cross-linked low generation (generation 2, G2) PAMAM dendrimers. These synthesized materials can effectively condense DNA into ~200 nm polyplexes and degrade into G2 dendrimers after cellular uptake. Confocal laser scanning microscope studies revealed high cellular uptake behavior of disulfide cross-linked G2 PAMAM dendrimers. Compared to G2 and G5 PAMAM dendrimers, disulfide cross-linked G2 PAMAM dendrimers showed much improved gene transfection efficacy (both EGFP and luciferase gene) and low cytotoxicity on both HEK293 and HeLa cell lines. The disulfide cross-linked G2 dendrimer prepared at a linker/dendrimer molar ratio of 1:1 showed the highest gene transfection efficacy and exhibited comparable efficacy to branched PEI with a molecular weight of 25 kD, a commercially available nonviral gene vector. Our study demonstrated that disulfide cross-linked low generation PAMAM dendrimers with high transfection efficacy, low cytotoxicity, and low cost are efficient alternatives to high generation PAMAM dendrimers in gene delivery.