Transferrin-conjugated cationic liposome (Tf-DDAB liposome) was developed as a targeted gene delivery system by using heterobifunctional cross-linking agent, N-succimidyl-3-(2-pyridyldithio) propionate (SPDP), and gradient metrizamide ultracentrifugation method. Physico-chemical properties of Tf-liposome were determined by scanning/transmission electron microscopy (SEM/TEM) and dynamic laser-light scattering method (DLS) with a mean diameter of 584 +/- 15 nm. Gel retardation assay was performed using various DDAB:DNA ratios, and proved that the 6:1 weight ratio formulation gave the most neutralized complex. In vitro transfection was done in human cervical cancer cells, HeLa, and the transfection efficiency of Tf-liposome was found to be fivefold higher than that of unconjugated (plain) DDAB liposome and twofold higher than that of Lipofectin. In conclusion, a target-oriented Tf-DDAB liposome was made successfully and proved to be very efficient in DNA delivery into the cervical cancer cells in culture.