Desorption of Amphotericin B from Mixed Monolayers with Cholesterol at the Air/Water Interface

The desorption of amphotericin B (AmB) from mixed monolayers with cholesterol was studied by monitoring temporal changes in the relative area (At/A0) as a function of time at constant surface pressures, corresponding to three distinct regions of the AmB isotherm. The loss of AmB molecules from the interface was found to obey the Ter Minassian Saraga model [J. Colloid Interface Sci.11, 398 (1956)]. In the low surface pressure region the overall process of desorption is controlled by a one-step dissolution (at small times) followed by diffusion. At high pressures, however, the process of dissolution is more complex and consists of two steps that differ in rate. The presence of cholesterol molecules in the monolayer prevents the desorption of AmB molecules as evidenced by the constant desorption values. The analysis of the kinetics parameters confirms our previous findings, based on the analysis of excess functions, that the highest interactions, due to the stable complex formation, appear for the mixture of XAmB=0.7.