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In Vitro Gene Delivery with Non-Cytotoxic Cationic Oligopeptide Amphiphiles

Nikken Wiradharma, Drug Gene and Protein Delivery; Chemical and Biomolecular Engineering, Institute of Bioengineering and Nanotechnology; National University of Singapore, 31 Biopolis Way, #04-01, The Nanos, Singapore 138669, 21 Lower Kent Ridge Road, Singapore 119077, Singapore, Singapore, Yen Wah Tong, Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore, 117576, Singapore, and Yi Yan Yang, Drugs, Proteins and Genes Delivery, Institute of Bioengineering and Nanotechnology, 31 Biopolis Way #04-01, Singapore, Singapore.

In this study, cationic and amphiphilic oligopeptides with a sequence A12H5K10 and A12H5K15 were designed and tested as a non-viral gene vector. The amphiphilic oligopeptides exhibit a critical micelle concentration at around 0.9 and 1.1 mg/mL, respectively, indicating their ability to self-assemble into micelle form in aqueous environment. The formation of the micellar nanoparticles were also confirmed by scanning electron microscopy. Both peptides were able to condense DNA at small N/P ratio, with a size of around 300-400nm, and zeta potentials ranging from +7-18 mV. We also hypothesized that the pre-formation of micelle before complexation increases cationic surface density, hence providing stronger DNA binding capacity of the vector. As such, control study with a peptide without hydrophobic block, H5K10, was also performed to evaluate this hypothesis. In addition, DNAse degradation of DNA-bound peptide complex also provided strong evidence on this hypothesis. To evaluate the efficacy of the cationic peptide amphiphiles, cytotoxicity test and luciferase transfection test were performed for all the three peptides against HepG2, HEK293, and 4T1 cell lines. All these studies were performed in comparison with PEI as the positive controls. The results showed that our designed oligopeptides were able to induce in vitro gene expression at about one order of magnitude less than PEI, if not comparable, with significant reduction in cellular cytotoxicity.