To evaluate the enhancing effects of γ-CyD on gene transfer activity of AF-liposomes associating pDNA encoding EGFP controlled by a CMV or SV40 promoter, we examined EGFP and firefly luciferase gene expression after transfection of pDNA/γ-CyDs/AF-liposomes in HepG2 cells ( Figure 5) . The charge ratio of AF-liposome/pDNA was 1.6. γ-CyDs were added to AFliposome suspension before freeze-drying. The concentrations of γ-CyDs were 1 μM/μM lipids. The ζ-potential was measured by a light-scattering method. The particle size was determined using a photon correlation spectroscopic analyzer. Each value represents the mean ± SEM of 3 experiments. * P < .05 versus without CyD.