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The interaction between lipid bilayers plays a pivotal role in membrane fusion, which is involved in many processes of life, for instance, cellular secretion via exocytosis, virus infection, and signaling between nerve cells. A good fundamental understanding of membrane fusion, i.e. interaction of lipid membranes gives the opportunity to control membrane fusion. This is valuable for many applications in life science and bioengineering like drug delivery, chemical microreactors, synthesis of nanomaterials and gene transfer.
In order to get a better understanding of membrane fusion, the interaction of positively or negatively charged supported lipid bilayers (SPB) with small unilamellar vesicle (SUV) of opposite charge were studied by quartz crystal microbalance with dissipation monitoring (QCM-D) and fluorescence microscopy. Using QCM-D two tracts are observed: (i) an initial mass uptake accompanied by a simultaneous increase in dissipation followed (ii) by mass loss and a decrease in dissipation as large as the initial values. The first step leads back to attachment of intact vesicles while the second step is indicative of detachment of vesicles. This observation let us assume that lipids are swapped between the attached SUVs and the SPB. In order to verify this speculation fluorescence microscopy was used. These experiments showed clearly an exchange of the lipids between the SUV and the SPB. This platform can now be used for further studies focused on the effect of pH and ions in solution to the interaction of lipid bilayers.
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