Disulfide-bond-containing agamatine-cystaminebisacrylamide polymer demonstrates better transfection efficiency and lower cytotoxicity than polyethylenimine in NIH/3T3 cells.

Previously, we synthesized a non-viral vector containing disulfide bond by polymerization of agamatine (AGM) and N,N'-cystaminebisacrylamide (CBA). In this study, we investigated the transfection efficiency of disulfide bond (SS) containing AGM-CBA polymer in gene delivery into NIH/3T3 cells, and examined the factors affecting its transfection efficiency by comparing with polyethylenimine (PEI). In addition, experiments were carried out to determine the mechanisms of cell entry pathways and intracellular behavior of AGM-CBA/pDNA polyplexes. The transfection efficiency of AGM-CBA/pDNA with different weight ratios and different amounts of pDNA was measured and the pathways mediated transfection processes were studied by using various endocytosis inhibitors. To determine the intracellular behavior of AGM-CBA/pDNA polyplexes, the transfection efficiencies of AGM-CBA/pDNA and PEI/pDNA polyplexes with different combination structures were determined by using reporter gene and fake plasmid DNA. The transfection efficiency of AGM-CBA/pDNA polyplexes was correlated with its weight ratio of AGM-CBA and pDNA, and the amount of pDNA. Both AGM-CBA/pDNA and PEI/pDNA polyplexes enter into cell by clathrin- and caveolae-mediated endocytic pathways. However, AGM-CBA/pDNA showed different intracellular behavior in NIH/3T3 cells compared to PEI/pDNA polyplexes. It was hypothesized that disulfide bond in AGM-CBA could be an important factor contributing to its intracellular behavior and better transfection efficiency. Overall, AGM-CBA demonstrated better transfection efficiency and lower cytotoxicity than PEI in NIH/3T3 cells as a gene delivery vector.