AVS 60th International Symposium and Exhibition
    Biomaterial Interfaces Thursday Sessions
       Session BI+NL+NS+SS-ThM

Invited Paper BI+NL+NS+SS-ThM3
Primitive Osmosensing by Phospholipid Membranes

Thursday, October 31, 2013, 8:40 am, Room 201 B

Session: Bio/Nano Interfaces
Presenter: A.N. Parikh, University of California, Davis
Authors: K. Oglecka, Nanyang Technological University, Singapore
J. Sanborn, University of California, Davis
D. Gettel, University of California, Davis
R. Kraut, Nanyang Technological University, Singapore
B. Liedberg, Nanyang Technological University, Singapore
A.N. Parikh, University of California, Davis
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This talk describes experimental observations of the response of multicomponent vesicles to osmotic gradients. We find that giant vesicles, consisting of phase separating lipid mixtures, immersed in hypertonic bath exhibit a Rayleigh-Plateu like pearling instability paving for elemental mechanical process of vesicular self-reproduction. When immersed in hypotonic bath, however, the response of giant vesicles comprise an unusual transitory state, characterized by damped, periodic oscillations between a microscopically phase-separated state and a uniform one. We find that this unusual oscillatory phase separation is synchronized with the cyclical patterns of membrane tension and poration, producing swell-burst cycles. Swelling, which is caused by the influx of water, raises membrane tension, thus promoting the appearance of microscopic domains. Bursting, which facilitates solute leakage, relaxes the membrane tension, breaking up large domains into those below the optical limit. This autonomous self-regulatory response – in which an external osmotic perturbation is managed by a co-ordinated and cyclical sequence of simple physical mechanisms. These mechanisms allow vesicles to sense (by domain formation) and regulate (by solute efflux) osmotic differences across their compartmental boundaries in a negative feedback loop producing a primitive form of a quasi-homeostatic regulation in a synthetic system, generated from simple components, namely, water, osmolytes, and lipids.