Enhanced gene transfection efficiency by polyamidoamine (PAMAM) dendrimers modified with ornithine residues

Aim of the study was to prepare and to evaluate gene transfection efficiency and cytotoxicity of the ornithine-conjugated PAMAMG4 dendrimers. Ornithine-conjugated PAMAMG4 dendrimers were prepared by Fmoc synthesis. A comparative gene transfection study between PAMAMG4 dendrimers and the surface modified dendrimers was conducted in HEK 293T, GM7373 and NCI H157G cell lines. Effect of excess of ornithine (100muM) on transfection efficiency of the ornithine-conjugated PAMAMG4 dendrimers was investigated in separate experiment. Cytotoxicity of the dendriplexes was tested in HEK 293T cells by MTT assay. (1)H NMR and MALDI-TOF spectral analysis showed that about 60 molecules of ornithine (PAMAMG4-ORN60) were conjugated to a PAMAMG4 dendrimer. Preliminary studies indicated that dendriplexes at charge ratio (N/P 10) show higher transfection efficiency and presence of serum does not affect the transfection efficiency of the dendriplexes. Transfection efficiency of PAMAMG4-ORN60 dendriplexes was slightly higher in cancer cells (NCI H157G) as compared to HEK 293T cells. Transfection efficiency of the PAMAMG4-ORN60 dendrimers decreased in presence of excess of ornithine while there was no effect on the parent PAMAMG4 dendrimers. Cytotoxicity assay has shown that PAMAMG4-ORN60 dendriplexes at N/P 10 were safe at concentrations