Cationic liposomes as carriers for gene delivery: Physico-chemical characterization and mechanism of cell transfection

Abstract

The inter-correlations among the parameters that influence the transfection efficiency of liposome-DNA complexes (lipoplexes) as carriers in gene therapy, optimum procedures for transfection and mechanism of cell transfection were investigated. The morphology, size and ζ-potential of liposomes and lipoplexes were measured by atomic force microscopy (AFM) and dynamic light scattering techniques. The lipoplexes formation was tested by using gel electrophoresis. Transfection efficiency was assessed using luciferase and green fluorescence protein reporter plasmids, respectively. It was found that transfection efficiency markedly depended on liposome to DNA weight ratio, lipoplexes morphology and size. The intracellular trafficking of exogenous DNAs was observed by confocal laser microscopy. After 4 h incubation, DNAs delivered by Lipofectamine 2000 reached the nucleus with a much higher frequency than 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP). It was concluded that lipoplexes with filaments contributing more than globular obtained higher transfection efficiency with the maximum expression of 500000 RLU/mg luciferase in HeLa cells, for they are easy to release pDNA after endocytosis. These results implied that by further modifying the chemical features of the lipid vectors and controlling their biological behaviors, more efficient lipid delivery vectors may be achieved.

Key words: Cationic liposomes, gene delivery, transfection efficiency, AFM, intracellular trafficking.