Biophysical Society Thematic Meeting | Ascona, Switzerland

Liposomes, Exosomes, and Virosomes: From Modeling Complex Membrane Processes to Medical Diagnostics and Drug Delivery

Poster Abstracts

23-POS Board 12 Light-Triggered Morphological Transformations in Giant Vesicles

Vasil Georgiev 1 , David Bléger 2 , Andrea Grafmüller 1 , Stefan Hecht 2 , Rumiana Dimova 1 . 1 Max Planck Institute of Colloids and Interfaces, Potsdam, Brandenburg, Germany, 2 Humboldt University, Berlin, Berlin, Germany. Regulation of the lipid membrane structure and morphology are critical for many cellular processes such as the fission-fusion sequence in vesicular transport or endo- and exocytosis. A well-known membrane mimetic system for exploring such cellular processes is giant unilamellar vesicles (GUVs). Photosensitive molecules offer a way to modulate the membrane morphology. Here, we studied the behavior of GUVs in the presence of two photosensitive molecules, tetrafluoroazobenzene (F-azo) and azobenzene-trimethylammonium-bromide (azoTAB). Upon irradiation with light (green or UV and blue), the F-azo molecules undergo reversible trans-cis isomerization [Bléger et al. JACS 134:20597-20600, 2012]. UV and blue light irradiation of the vesicles mixed with F-azo induce reversible morphological transformations such as budding and bud readsorption. The molecule partitioning and orientation in the membrane was probed with molecular dynamics simulations. The energy gain of insertion and the barrier for flipping suggest that F-azo partitions in the membrane and that the observed GUV morphological transitions result from the F-azo isomerization. The associated area increase in the GUVs was measured via vesicle electrodeformation for two different F-azo concentrations. The influence of molecule isomerization on phase separated vesicles was also examined. The appearance of liquid- disordered domains within the preexisting liquid ordered phase was observed. Differently from the action of F-azo molecules, under UV irradiation, azoTAB molecules cause the GUVs to rupture. A potential application of such system includes the development of drug delivery systems with light-triggered release of solutes. These results suggest that the photosensitive molecules provide us with a handle to modulate the membrane morphology and stability. We acknowledge S. Santer (Potsdam University) for the azoTAB molecules and IMPRS for the financial support.

81