SOLUBILIZING EFFECTS CAUSED BY ALKYL PYRIDINIUM SURFACTANTS IN PHOSPHATIDYLCHOLINE LIPOSOMES

The solubilization of neutral and electrically charged liposomes by a series of alkyl pyridinium surfactants (alkyl chain lengths C-10-C-14) was investigated. Solubilization was detected as a decrease in static light-scattering of liposome suspensions. Two parameters were regarde d as corresponding to the effective surfactant/lipid molar ratios at w hich the surfactant saturated the liposomes Re-sat and led to a comple te solubilization of these structures Re-sol. From these parameters th e corresponding surfactant partition coefficients were determined. The Re and K parameters fell as the surfactant alkyl chain length decreas ed or both the critical micellar concentration (CMC) and the hydrophil ic/lipophilic balance (HLB number) increased, regardless of the bilaye rs electrical charge. Thus, although decyl-pyridiniumm bromide (DePB) showed the highest ability for saturation and solubilization of bilaye rs, its concentration was always higher than that needed for dodecyl-p yridinium bromide (DoPB) and tetradecyl-pyridinium bromide (TePB), the last one being the most active. These results emphasize the influence of the hydrophilic/lipophilic balance of these surfactants on liposom e solubilization and the minor influence of the electrostatic factors in this process.