Biophysical Society Thematic Meeting

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

, David Bléger

, Andrea Grafmüller

, Stefan Hecht

, Rumiana Dimova

Max Planck Institute of Colloids and Interfaces, Potsdam, Brandenburg, Germany,

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.