| Abstract
| - In previous report (Čeh, B.; Lasic, D. D.Langmuir1995, 11, 3356), theaccumulation of external moleculesinto preformed liposomes by the influence of various gradients, a veryimportant feature in recent applicationsof liposomes as drug carriers, was presented. The thermodynamicmodel of liposome loading with weakbases/acids used preset permeability coefficients that allowed ordisallowed penetration of noncharged andcharged species, respectively, across the vesicle membrane. Now inthis article we investigate the kineticsof drug loading. Using Fick's first law, we can calculatekinetics of loading, expressing the diffusion constantas a permeability coefficient and defining an associated flow rate.Results of this theoretical approach, whichin the limit of long times converge to the result of the thermodynamicmodel, show the filling of liposomeswith particular molecules as a function of time, as well as timedependence on pH changes and concentrationof any other species in the liposome internal or externalenvironment.
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