Improved Tat-mediated plasmid DNA transfer by fusion to LK15 peptide

The use of cell penetrating peptides (CPPs), such as Tat-derived peptide, to deliver DNA into cells is limited as evidenced by the low transfection efficiency of their DNA complexes. Here, we demonstrate that covalent attachment of membrane active peptide LK15 to Tat peptide improves gene transfer. Our results demonstrate that Tat peptide was able to form complexes with DNA, but their transfection efficiency was insufficient as assessed by luciferase assay. The attachment of LK15 to Tat significantly improved the physiochemical properties of the DNA complexes, rendered the complexes membrane active and enhanced the gene expression in HT29 and in HT1080 cultured cells. The enhanced transfection ability of Tat-LK15 compared to Tat is likely to be due mainly to the higher uptake of DNA. Finally, we evaluated the penetration and transfection ability of Tat and Tat-LK15 in multicellular tumour spheroids (MCTS) to mimic in vivo delivery to tumours. The results showed that the penetration and transfection ability of Tat and Tat-LK15/DNA complexes were limited to the rim of HT29 spheroids. Taken together, our data shows improvement in the transfection efficiency of Tat peptide by covalent attachment to LK15. Further advancements are needed before any potential applications in tissues as the penetration into the core of MCTS remains severely restricted.