Synergistic effects of conjugating cell penetrating peptides and thiomers on non-viral transfection efficiency

Nanoparticles generated by complex coacervation of plasmid DNA (pDNA) and modified chitosans namely chitosan–thioglycolic acid (TGA) conjugate and chitosan–HIV-1 Tat peptide conjugate were evaluated as gene delivery systems. In order to optimize transfection efficiency, chitosan–HIV-1 Tat peptide conjugate was combined with chitosan–TGA before its complexation with pDNA. Particle size and zeta potential measurements were performed to characterize the generated nanoparticles. The nanoparticles transfection efficiencies were assessed by exploitation of the green fluorescent protein (GFP) reporter gene. HEK293 cells were incubated for 24 h with the nanoparticles and the GFP positive cells were observed by fluorescence microscopy. The nanoparticles in the size range of 200–300 nm could transfect HEK293 cells as a model cell line with different transfection efficiencies. Unlike chitosan–TGA, chitosan–HIV-1 Tat peptide led to increased zeta potential of nanoparticles as compared to unmodified chitosan. The transfection efficiency of the nanoparticles generated by combination of chitosan–HIV-1 Tat peptide with chitosan–TGA was comparatively higher than that of the nanoparticles generated by either chitosan–TGA or the combination of chitosan–HIV-1 Tat peptide with unmodified chitosan. After 72 h of incubation, the combination of chitosan–HIV-1 Tat peptide with chitosan–TGA was found to be 7.12- and 67.37 times more efficient than unmodified chitosan and pDNA alone, respectively and showed a synergistic effect in transfection of pDNA into the cells. Moreover, none of the nanoparticles showed any severe cytotoxicity. Accordingly, this strategy might result in a potent carrier for gene delivery.