Solubilization of DPPC Small Unilamellar Liposomes by Sucrose Esters. A Fluorescence Study

The effect of the microenvironment on the Laurdan fluorescence was employed to study the solubilization mechanism of Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) small unilamellar vesicles with several sucrose monoesters. The saturation and the solubilization concentrations (C sat and C sol), the ester–DPPC molar ratio (R e) and the bilayer/aqueous partition coefficients (K) were measured by monitoring changes in laurdan generalized polarization for four different alkyl esters of sucrose. All critical concentrations showed linear dependence with DPPC liposomes concentration. The saturation and the solubilization capacity of this type of surfactant do not show a direct dependence with the length of its alkyl chain. For the studied series the lauryl sucrose derivative is the compound which presents the higher capacity to saturate and solubilize the DPPC vesicles, while the capacity of the esters with shorter and longer alkyl chains worsen. When the results obtained for DPPC liposomes are compared with previously obtained data for DODAC a different structuration of sucrose moieties in the bilayer can be postulated