BACKGROUND: At present, non-viral vectors have become a hotspot in gene transfection research because of their strong points of lower toxicity,low immunologic reaction, target orientation, and easy assembly.OBJECTIVE: To evaluate the role of chitosan-DNA nanoparticles in transfection efficiency and cellular toxicity of tumor cells.DESIGN: Observational control trial. SETTING: Institute of Environmental Medical Sciences, Tongji Medical College of Huazhong University of Science and Technology.MATERIALS: Zeta potential/ particle size analyzer; spectrofluorometer;Hoechst 33258; PLPS-3'EGFP plasmid; lung cancer cell A549 and human hepatocarcinoma cell line HepG2.METHODS: This experiment was conducted in the Institute of Environmental Medical Sciences, Tongji Medical College of Huazhong University of Science and Technology, from December 2004 to December 2005. The green fluorescent protein gene was used as report gene; chitosan green fluorescent protein plasmid nanoparticles were prepared with re-coherence gy of prepared nanoparticles; Zeta potential/ particle size analyzer was used to measure the diameter and superficial potential of the nanoparticles;enzyme-protection test was used to measure anti DNA enzyme degradation and lung cancer cell A549 were transfected in vitro. Transfection of the cells was observed under the inverted fluorescence microscope after 24, 48nanoparticles.characteristics: Nucleic acid encapsulation efficiency of chitosan nanoparticles was 91.7%, and the nanoparticles presented globular shape with the mean diameter of 149nm and superficial potential of +20.5 mV.Transfection rate of nanoparticles: It reached the peak 48 hours later; the transfection rate of A549 was 95% while that of HepG2 was only about chitosan could inhibit the growth of HepG2 and A549, and the inhibitory effect of chitosan on cellular growth was stronger than that of the nanoparticles.CONCLUSION: Nanoparticles of chitosan plasmid can transfect HepG2and A549, two kinds of tumor cells, and have inhibitory effects on their growth, suggesting that nanoparticles, as the carrier of DNA, can be used in the transfection of tumor cells.