Abstract: AimTo prepare TK-gene nanoparticles and investigate its expression. MethodsBiodegradable and biocompatible polymer polylactic-co-glycolic acid (PLGA) was used to prepare recombinant plasmid p^po nanoparticles by double-emulsion evaporation technique. The characteristics of the nanoparticles including morphology, entrapment efficiency was investigated. The expression of TK gene was also investigated by MTT assay, which could determine the dying cells after the addition of gancyclovir (GCV). The enhanced green fluorescent protein (EGFP) expression in human hepatocarcinoma SMMC-7221 cells and human normal parenchymal Chang liver cells were assessed by flow cytometric analysis. ResultsThe resulting plasmid-nanoparticles had regular spherical surface and a narrow particle size with a mean diameter of (72±12) nm, The average entrapment efficiency was 91.25%, the enhanced transfection efficiency and ability protecting plasmid DNA from degraded by nuclease or sonication due to nanoparticles encapsulation. ConclusionDNA-nanoparticles need further study as gene delivery system.