Improved gene expression pattern using Epstein–Barr virus (EBV)-based plasmid and cationic emulsion

To improve transgene expression of a non-viral gene delivery system, an Epstein–Barr virus (EBV)-based plasmid and cationic emulsion complex was prepared and evaluated. Cationic emulsion was formulated with castor oil, 3-N-(N′,N′-dimethylaminoethane)-carbamoyl cholesterol (DC-Chol) and other co-emulsifiers. An EBV-based plasmid containing the two EBV components, origin of replication (oriP) and EBV nuclear antigen 1 (EBNA-1), was constructed. The physical characteristics of the emulsion and the emulsion/DNA complex were determined. After cells were transfected with cationic emulsion/EBV-based plasmid complex, transfection efficiency and expression pattern were evaluated using green fluorescent protein (GFP) as a reporter. The average particle size and zeta potential of the emulsion itself were 96 nm and +17 mV, respectively. The emulsion showed stable size distribution up to at least one month. With an increase of emulsion to DNA ratio, zeta-potential increased from negative to positive and the particle size decreased to 200–300 nm. The complex was stable against DNase I digestion and showed comparable transfection efficiency with Lipofectin® for several tested cell lines. An enhanced and prolonged gene expression was achieved using EBV-based plasmid and cationic emulsion complex. Combining physically stable emulsion with self-replicating EBV-based plasmid may confer more effective gene expression.