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BP: Fachverband Biologische Physik

BP 7: Poster I

BP 7.7: Poster

Monday, March 23, 2009, 17:45–20:00, P3

Dynamics of vesicle adhesion through a polymer cushion: role of layer thickness and tension — •Kheya Sengupta¹ and Laurent Limozin² — ¹CINAM/CNRS-UPR3118, Marseille, France — ²INSERM UMR 600 - CNRS UMR 6212, Marseille, France

The adhesion of giant unilamellar phospholipid vesicles to planar substrates coated with extra-cellular matrix mimetic cushions of hyaluronan is studied using quantitative dual wavelength reflection interference contrast microscopy (DW-RICM). The thickness of the cushion is varied in the range of about 50 to 100 nm, by designing various coupling strategies. On bare protein coated substrates, the vesicles spread fast (0.5 sec) and form a uniform adhesion-disc, with the average membrane height about 4 nm. On thick hyaluronan cushions (>80 nm), the vesicle sits on the top of the cushion and spreading is totally prevented. On a thin and inhomogeneous cushion, the adhesion is modified but not totally impeded. The spreading is slow (~20 sec) compared to the no-cushion case. We show that in addition to the quality of the cushion, the initial tension of the vesicles plays a crucial role in the spreading kinetics. We interpret our experimental results in the light of a theoretical framework which integrates the influence of polymers on the membrane-surface interaction potential on one hand and the role of this potential in the spreading kinetics on the other hand. We conclude that the slow kinetics arises partially from a reduction in the adhesion-strength but the main contribution comes from the increased viscosity in the presence of the polymer.