Fusion of biological membranes is used by diverse biological systems, from viruses to organelles, to deliver macromolecules from one membrane-bound volume to another. Membrane fusion has also been investigated as a potentially efficient mechanism for the delivery of macromolecular therapeutics to the cytoplasm. However, a key limitation of current fusogenic liposomal systems is their relative inefficiency and lack of specificity for target cells. Here, we utilize lipid membrane phase separation to enhance fusion of liposomes to model membranes and cells. Specifically, we report that concentrating the fusogenic lipid, 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), within lipid domains dramatically increases the efficiency of membrane fusion. To demonstrate this concept, we created phase separating and non-phase separating liposomes with and without DOTAP, each labeled with a fluorescent membrane dye. These liposomes were incubated with target membranes of increasing molecular complexity including giant unilamellar vesicles, giant plasma membrane vesicles, and HeLa cells. In each case, target membranes incubated with phase separating liposomes containing DOTAP exhibited increased membrane fluorescence when compared to membranes incubated with non-phase separating vesicles containing DOTAP and control vesicles lacking DOTAP. These data demonstrate that phase separation can enhance membrane fusion by locally concentrating fusogenic lipids. We anticipate fusogenic, phase separating liposomes will be a key first step toward building an efficient and specific system for delivery of macromolecules to the cytoplasm. In particular, our ongoing work incorporates targeting ligands into phase separating liposomes, such that phase separation and subsequent membrane fusion can be triggered by specific interactions between liposomes and the target cell population.

Lipid phase separation enhances fusion

253rd National Meeting (2017)

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