Kinetics of pore-mediated release of marker molecules from liposomes or cells

We present a general mathematical treatment of marker efflux from liposomes or cells mediated by pore formation with the idea of using it in practice to obtain basic information about the underlying rates and mechanism. The approach encompasses permeation of molecules through any kind of pore-like defects in a cell membrane as they are induced by the action of some external agent. The approach broadens an earlier treatment to the more realistic general case in which a distribution of pore lifetimes must be taken into account. We derive a theoretical retention function describing the amount of marker remaining in the cells, formulated in terms of the pore activation and inactivation kinetics. The phenomenological efflux function evaluated directly from experimental data, is directly comparable with this retention function so long as the experimental signal is linearly related to the marker concentration. With the use of self-quenching dyes the relationship between signal and concentration is not, in general, linear, so that a more complicated treatment may be required. Even for these dyes, however, linearity holds under the frequently encountered condition of "all-or-none" release of dye from vesicles, a condition that can itself be verified experimentally.