Abstract
This study is primarily concerned with the molecular interaction and the interfacial properties of mixed monolayers at the air/water interface at different temperatures. Measurement of surface pressure □□area per molecule (□□A) isotherms for DSPC/cholesterol, DSPC/DSPE-PEG2000, DSPC/paclitaxel, mixed monolayers, DSPC/cholesterol/DSPE-PEG2000 mixed monolayers, and DSPC/cholesterol/DSPE-PEG2000/paclitaxel mixed monolayers, respectively were conducted at different temperatures. Thermodynamic characteristics of these mixed systems at the air/water interface were studied from data obtained. The □□A isotherms showed these four components were miscible at 24.5℃. Temperature and compositions both had profound influence on the shape of isotherms, the compressibility, the stability, and the relaxation behavior of mixed monolayers. The most stable formulation can be determined by the estimation of the excess free energy of mixing. Additionally, the corresponding liposomal membrane stability of these mixed system was determined by release of encapsulated 5,6-carboxyfluorescein. Finally, the relevance of the observations for these mixed monolayers to the behavior in a liposomal domain was discussed.