Novel Mechanisms of Cell Uptake in Lipid-Mediated Gene Delivery

The mechanism of cell uptake in lipid mediated gene delivery was investigated in NIH3T3 and CHO cell lines. We show that different endocytic pathways are activated by shape coupling between lipoplex and membrane lipids. Our results suggest that tailoring the lipoplex lipid composition to the patchwork-like plasma membrane profile could be a successful machinery of coordinating the endocytic pathway activities and the subsequent intracellular processing. Transfection experiments performed at 4C, when endocytosis does not take place, show that a novel class of highly efficient multicomponent lipoplexes enter cells by a temperature-independent fusion-like mechanism. In vivo, plasma proteins bind to lipoplex surface and create a rich ‘protein corona’ that is recognized by cells and other biological structures. The ‘protein corona’ associated to lipoplexes after interaction with human plasma was found to be much richer in basic immunoglobulins gamma proteins (Ig-Gs) than that of pure lipid vesicles in the absence of DNA. Because surface properties of lipoplexes may determine their interaction with cells and tissues, an accurate knowledge of lipoplex surface properties may be important for predicting biological responses. These findings also suggest the existence of hybrid structures made of multilamellar complexes either stuck together by DNA or coexisting with DNA loaded intact vesicles.