Transient pores in stretched vesicles: role of leak-out

Abstract

Abstract We have visualized macroscopic transient pores in mechanically stretched giant vesicles. They can be observed only if the vesicles are prepared in a viscous solution to slow down the leak-out of the internal liquid. We study here theoretically the full dynamics of growth (driven by surface tension) and closure (driven by line tension) of these large pores. We write two coupled equations of the time evolution of the radii r(t) of the hole and R(t) of the vesicle, which both act on the release of the membrane tension. We find four periods in the life of a transient pore: (I) exponential growth of the young pore; (II) stop of the growth at a maximum radius rm; (III) slow closure limited by the leak-out; (IV) fast closure below a critical radius, when leak-out becomes negligible. Ultimately the membrane is completely resealed. Notation d membrane thickness E surface stretching modulus K b Helfrich bending constant Q leak-out flux r pore radius r i pore radius at nucleation r c pore radius at zero tension r L characteristic radius of leak-out r m radius at maximum (II) r 23 pore radius at cross-over between (II) and (III) r 34 pore radius at cross-over between (III) and (IV) R vesicle radius R i initial vesicle radius R 0 vesicle radius at zero tension V L leak-out velocity V 3 slow closure velocity limited by leak-out (III) V 4 fast closure velocity at end (IV) η 2 lipid viscosity η s surface viscosity η 0 viscosity of solution σ surface tension σ 0 surface tension before pore opening τ rise time of pore growth (I) J line tension