A comparative evaluation of poly-l-lysine-palmitic acid and Lipofectamine TM 2000 for plasmid delivery to bone marrow stromal cells

The current study compared the effectiveness of an amphiphilic biomaterial poly(l-lysine)-palmitic acid (PLL-PA), and the lipid-based transfection agent LipofectamineTM 2000 for plasmid delivery to bone marrow stromal cells (BMSC). We investigated the utility of the carriers to deliver a plasmid containing enhanced green fluorescent protein (pEGFP) to BMSC in vitro. Confocal microscopy was used to investigate the intracellular trafficking of pEGFP/carrier complexes. pEGFP delivery and EGFP expression were assessed by flow cytometry. PLL-PA formed condensed structures with pEGFP and successfully delivered the plasmid into the nucleus within 5h of incubation with the cells. PLL- delivered the pEGFP to 80% of the cells, achieving a maximum transfection efficiency of 22%. This was significantly higher than LipofectamineTM 2000-mediated transfection, which was 11% under most optimal conditions. Dosing the BMSC two or three times during the 24h period increased the transfection efficiency by 2-3 folds, without compromising cell viability. When chloroquine was employed as an ensomolytic agent, 100mum of the drug increased the transfection efficiency while reducing cell viability, but lower concentrations (1-10mum) were not beneficial for transfection. Combining PLL-PA with LipofectamineTM 2000 created an additive effect, increasing the transfection efficiency of PLL-PA. Long-term evaluation of gene expression with pEGFP/PLL-PA yielded 17% transfection on day 1, which gradually decreased over a 12-day period. We conclude that PLL- is an effective biomaterial carrier and a promising candidate for non-viral gene delivery to BMSC.