  We establish a biophysical model for the dynamics of lipid vesicles exposed
to surfactants. The solubilization of the lipid membrane due to the insertion
of surfactant molecules induces a reduction of membrane surface area at almost
constant vesicle volume. This results in a rate-dependent increase of membrane
tension and leads to the opening of a micron-sized pore. We show that
solubilization kinetics due to surfactants can determine the regimes of pore
dynamics: either the pores open and reseal within a second (short-lived pore),
or the pore stays open up to a few minutes (long-lived pore). First, we
validate our model with previously published experimental measurements of pore
dynamics. Then, we investigate how the solubilization kinetics and membrane
properties affect the dynamics of the pore and construct a phase diagram for
short and long-lived pores. Finally, we examine the dynamics of sequential pore
openings and show that cyclic short-lived pores occur at a period inversely
proportional to the solubilization rate. By deriving a theoretical expression
for the cycle period, we provide an analytic tool to measure the solubilization
rate of lipid vesicles by surfactants. Our findings shed light on some
fundamental biophysical mechanisms that allow simple cell-like structures to
sustain their integrity against environmental stresses, and have the potential
to aid the design of vesicle-based drug delivery systems.
