Highly Efficient Protein-free Membrane Fusion: A Giant Vesicle Study

Author(s)

Lira, Rafael B. ^{[1, 2]} ; Robinson, Tom ^[2] ; Dimova, Rumiana ^[2] ; Riske, Karin A. ^[1]

Affiliation

^[1] Univ Fed Sao Paulo, Dept Biofis, Sao Paulo - Brazil

^[2] Max Planck Inst Colloids & Interfaces, Dept Theory & Biosyst, Potsdam - Germany

• Document type: Journal article
• Source: BIOPHYSICAL JOURNAL; v. 116, n. 1, p. 79-91, JAN 8 2019.
• Web of Science Citations: 6

Abstract

Membrane fusion is a ubiquitous process in biology and is a prerequisite for many intracellular delivery protocols relying on the use of liposomes as drug carriers. Here, we investigate in detail the process of membrane fusion and the role of opposite charges in a protein-free lipid system based on cationic liposomes (LUVs, large unilamellar vesicles) and anionic giant unilamellar vesicles (GUVs) composed of different palmitoyloleoylphosphatidylcholine (POPC)/palmitoyloleoylphosphatidylglycerol (POPG) molar ratios. By using a set of optical-microscopy- and microfluidics-based methods, we show that liposomes strongly dock to GUVs of pure POPC or low POPG fraction (up to 10 mol%) in a process mainly associated with hemifusion and membrane tension increase, commonly leading to GUV rupture. On the other hand, docked LUVs quickly and very efficiently fuse with negative GUVs of POPG fractions at or above 20 mol%, resulting in dramatic GUV area increase in a charge-dependent manner; the vesicle area increase is deduced from GUV electrodeformation. Importantly, both hemifusion and full fusion are leakage-free. Fusion efficiency is quantified by the lipid transfer from liposomes to GUVs using fluorescence resonance energy transfer (FRET), which leads to consistent results when compared to fluorescence-lifetime-based FRET. We develop an approach to deduce the final composition of single GUVs after fusion based on the FRET efficiency. The results suggest that fusion is driven by membrane charge and appears to proceed up to charge neutralization of the acceptor GUV. (AU)

• FAPESP's process: 11/22171-6 - Study of biophysical properties of giant unilamellar vesicles as model for intracellular delivery of material: membrane electroporation and fusion
• Grantee: Rafael Bezerra de Lira
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 16/13368-4 - Nanostructured systems: from membrane biomimetic models to carriers of bioactives
• Grantee: Karin Do Amaral Riske
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 13/07246-5 - Electroporation and fusion of electrically charged vesicles
• Grantee: Rafael Bezerra de Lira
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate