Intracellular trafficking of transferrin-conjugated liposome/DNA complexes by confocal microscopy

Intracellular trafficking of transferrin-conjugated dimethyldioctadecyl-ammonium bromide liposome (T1-liposome)/DNA complexes in HeLa cells was studied using the double-labeled fluorescence technique and confocal microscopy. The size of the T1-liposome/DNA complex was about 367 nm in diameter and the zeta-potential of it at a 5:1 (w/w) ratio was almost neutral. The intracellular pathway of the T1-liposome/DNA complex, noted as green (FITC), red (rhodamine) or yellow (FITC + rhodamine) fluorescence, was elucidated from the plasma membrane to the endosome (or lysosome), and finally to the nucleus. The results of this study indicate that plasmid DNA enters into the nucleus not only as a free form but as an associated form complexed with T1-liposome. More interestingly, the T1-liposome undergoes a nuclear location in the form of ordered structures. This could be a very useful piece of information in designing a safe and advanced gene delivery system.