10.1021/mp200374e.s002 Francesco Cardarelli Francesco Cardarelli Daniela Pozzi Daniela Pozzi Angelo Bifone Angelo Bifone Cristina Marchini Cristina Marchini Giulio Caracciolo Giulio Caracciolo Cholesterol-Dependent Macropinocytosis and Endosomal Escape Control the Transfection Efficiency of Lipoplexes in CHO Living Cells American Chemical Society 2012 lipid composition cationic liposome formulations imaging approaches DOTAP intracellular delivery zwitterionic lipid dioleoylphosphatidylethanolamine zwitterionic helper dioleoylphosphocholine DNA intracellular fate uptake mechanism Transfection Efficiency physicochemical properties Chinese hamster ovary cell uptake endosomal compartments DOPE DOPC lysosome marker lipoplexe Endosomal Escape Control CHO Living CellsHere lipoplex macropinocytosis 2012-02-06 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Cholesterol_Dependent_Macropinocytosis_and_Endosomal_Escape_Control_the_Transfection_Efficiency_of_Lipoplexes_in_CHO_Living_Cells/2553337 Here we investigate the cellular uptake mechanism and final intracellular fate of two cationic liposome formulations characterized by similar physicochemical properties but very different lipid composition and efficiency for intracellular delivery of DNA. The first formulation is made of cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and the zwitterionic helper dioleoylphosphocholine (DOPC), while the second one is made of the cationic 3β-[<i>N</i>-(<i>N</i>,<i>N</i>-dimethylaminoethane)-carbamoyl] cholesterol (DC-Chol) and the zwitterionic lipid dioleoylphosphatidylethanolamine (DOPE). Combining pharmacological and imaging approaches we show that both DOTAP-DOPC/DNA and DC-Chol-DOPE/DNA lipoplexes are taken up in Chinese hamster ovary (CHO) living cells mainly through fluid-phase macropinocytosis. Our results also indicate that lipoplex macropinocytosis is a cholesterol-sensitive uptake mechanism. On the other side, both clathrin-mediated and caveolae-mediated endocytosis play a minor role, if any, in the cell uptake. Colocalization of fluorescently tagged lipoplexes and Lysosensor, a primary lysosome marker, reveals that poorly efficient DOTAP-DOPC/DNA lipoplexes are largely degraded in the lysosomes, while efficient DC-Chol-DOPE/DNA systems can efficiently escape from endosomal compartments.