Inward multivesiculation at the basal membrane of adherent giant phospholipid vesicles.

Adherent giant vesicles composed of phosphatidylcholine, phosphatidylserine and biotinylated lipids form clusters of inward spherical buds at their basal membrane. The process is spontaneous and occurs when the vesicles undergo a sequence of osmotic swelling and deswelling. The daughter vesicles have a uniform size (diameter ≈ 2-3 μm), engulf small volumes of outer fluid and remain attached to the region of the membrane from which they generate, even after restoring the isotonicity. A pinning-sealing mechanism of long-wavelength modes of membrane fluctuations is proposed, by which the just-deflated vesicles reduce the surplus of membrane area and avoid excessive spreading and compression via biotin anchors. The work discusses the rationale behind the mechanism that furnishes GUVs with basal endovesicles, and its prospective use to simulate cellular events or to create molecular carriers.