Layered double hydroxide nanoparticles as cellular delivery vectors of supercoiled plasmid DNA

We prepared stable homogeneous suspensions with layered double hydroxide (LDH) nanoparticles for in vitro gene delivery tests. The viability of HEK 293T cells in the presence of LDH nanoparticles at different concentrations was investigated. This revealed 50% cell viability at 500 mu g/ml of LDH nanoparticles that is much higher than 50-100 mu g/mL used for the delivery tests. The supercoiled pEF-eGFP plasmid (ca. 6100 base pairs) was mixed with LDH nanoparticle suspensions for anion exchange at a weight ratio of DNA/LDH between 1:25 and 1:100. In vitro experiments show that GFP expression in HEK 293T cells starts in the first day, reaches the maximum levels by the second day and continues in the third day. The GFP expression generally increases with the increase in DNA loading in DNA-LDH nanohybrids. However, the delivery efficiency with LDH nanoparticles as the agent is low. For example, the relative efficiency is 7%-15% of that of the commercial agent FuGENE (R) 6. Three to 6% of total cells expressed GFP in an amount detectable by the FACS cytometry 2 days after transfection at 1 mu g/mL of plasmid DNA with 25 mu g/mL of LDH nanomaterial. The lower delivery efficiency could be attributed to the aggregation of LDH nanoparticles caused by the long-chain plasmid DNA.