  The response of lipid bilayers to osmotic stress is an important part of
cellular function. Previously, in [Oglecka et al. 2014], we reported that
cell-sized giant unilamellar vesicles (GUVs) exposed to hypotonic media,
respond to the osmotic assault by undergoing a cyclical sequence of swelling
and bursting events, coupled to the membrane's compositional degrees of
freedom. Here, we seek to deepen our quantitative understanding of the
essential pulsatile behavior of GUVs under hypotonic conditions, by advancing a
comprehensive theoretical model for vesicle dynamics. The model quantitatively
captures our experimentally measured swell-burst parameters for
single-component GUVs, and reveals that thermal fluctuations enable rate
dependent pore nucleation, driving the dynamics of the swell-burst cycles. We
further identify new scaling relationships between the pulsatile dynamics and
GUV properties. Our findings provide a fundamental framework that has the
potential to guide future investigations on the non-equilibrium dynamics of
vesicles under osmotic stress.
