Biophysical Society Thematic Meeting| Padova 2019

Quantitative Aspects of Membrane Fusion and Fission

Poster Abstracts

33-POS Board 33 INVESTIGATION OF FORCES DURING MEMBRANE FUSION BY USING LIPID VESICLES AS AFM PROBES Ines Lüchtefeld 1 ; Tomaso Zambelli 1 ; Janos Vörös 1 ; 1 ETH Zurich, Institute for Biomedical Engineering, Zurich, Switzerland The interaction and fusion of phospholipid membranes plays an important role in many essential physiological processes such as neurotransmitter release at the synapse or drug delivery to cells with cationic liposomes. In spite of the physiological importance, the process of establishing a fusion pore between two membranes is still not fully understood. Especially vague is the understanding about the role of the contact time and contact force of two membranes for the establishment of hemi- and full fusion states. Therefore, we propose a new experimental system to investigate the influence of contact forces during membrane fusion. The system consists of an atomic force microscopy (AFM) cantilever with an integrated microfluidic channel, namely the FluidFM. It is used to firstly attach a giant unilamellar vesicle (GUV) to the tip of the cantilever by applying negative pressure inside of the channel, and to subsequently bring this GUV into force-controlled contact with a supported lipid bilayer, a surface immobilized GUV, or a cell. Using fluorescence increase and recovery measurements we are able to observe fusion states dependent on the contact force, contact time, and other parameters like membrane tension and ion concentration. By bringing two lipid membranes into close and force-controlled proximity for defined time periods, the presented experimental system is not only able to model processes like cationic liposome assisted drug delivery, but can also mimic the zippering function of the cytosolic domains of the SNARE complex. Consequently, the presented experimental system is able to facilitate new quantitative insights into various membrane fusion processes, like the contact time and force necessary for protein free fusion, as in liposome assisted drug delivery, or the role of the transmembrane domains of the SNARE complex components.

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