Synthesis of PAMAM Dendrimer Derivatives with Enhanced Buffering Capacity and Remarkable Gene Transfection Efficiency

Abstract

In this study, we introduced histidine residues into l-arginine grafted PAMAM G4 dendrimers to enhance proton buffering capacity and evaluated the physicochemical characteristics and transfection efficacies in vitro. The results showed that the synthesized PAMAM G4 derivatives effectively delivered pDNA inside cells and the transfection level improved considerably as the number of histidine residues increased. Grafting histidine residues into the established polymer vector PAMAM G4-arginine improved their proton buffering capacity. The cytotoxicity of PAMAM G4 derivatives was tested and it was confirmed that they displayed relatively lower cytotoxicity compared to PEI25KD in various cell lines. Also, confocal microscopy results revealed that PAMAM G4 derivatives effectively delivered pDNA into cells, particularly into the nucleus. These PAMAM dendrimer derivatives conjugated with histidines and arginines may provide a promising polymeric gene carrier system.

Polyamidoamine (PAMAM) dendrimers modified with short oligopeptides for early endosomal escape and enhanced gene delivery

“…Interestingly, the addition of a histidine group remarkably lowered the cytotoxicity. This result is consistent with previous reports that the PAMAM G4-R conjugate is more toxic than the PAMAM G4-HR (Yu et al, 2011). Based on the cytotoxicity data it was presumed that the histidines grafted between PAMAM G4 and other amino acids may act as a neutralizing layer minimizing the toxicity.…”

“…The higher transfection efficiency of this conjugate was attributed to the synergistic effects of the cationic amino acid arginine that enhances cellular uptake (Futaki, 2005;Luo et al, 2012;Rothbard et al, 2002). In addition, induction of the proton sponge effect by histidine further enhanced this efficiency by overpowering the acidic environment inside the endosomal compartment (Yu et al, 2011). Furthermore, CPPs containing hydrophobic amino acid like phenylalanine (F) and leucine, show increased transfection efficiency because of their enhanced interaction with the cell membrane (Choi et al, 2007;Kurisawa et al, 2000;Sang Yoo et al, 2005;Tian et al, 2007;Wang et al, 2009).…”

PAMAM dendrimer - cell membrane interactions

“…Dendrimers are branched polymeric nanoparticles, and have been investigated for a range of biomedical applications [7,8] such as drug [9] and gene delivery [10], due to the possibility for precise control over their physicochemical properties. Their size, shape and surface charge can be tuned for bypassing the cellular membrane [11,12], forming complexes with DNA [13,14], and solubilising hydrophobic drugs [9].…”

Heterocyclic amine-modified polyethylenimine as gene carriers for transfection of mammalian cells

“…479 Also histidine could provide a direct fusogenic property on the 480 endosomal membranes at acidic pHs [35,36]. Covalently attaching 481 onto PAMAM G4 derivatives [37], chitosan [38] and polylysine 482 [39,40] increased buffering capacity and transfection efficiency. The high level of transfection activity observed in this study 524 with modified derivatives of PEIs is consistent with factors in addi-525 tion to buffering capacity affecting endosomal release and Table 3 Size and zeta potential data for polyplexes prepared with heterocyclic amine derivatives of PEI 25 and PEI 10 and RL-CMV plasmid DNA.…”