Influence of the alkyl chain length of alkyl glucosides on their ability to solubilize phosphatidylcholine liposomes

Abstract

The solubilizing alterations caused by a series of alkyl glucosides (alkyl chain length ranging from C 8 to C 12) in neutral and electrically charged phosphatidylcholine (PC) liposomes were investigated. The surfactant to phospholipid molar ratios (Re) and the bilayer/aqueous phase partition coefficients ( K) were determined by monitoring the changes in the static light scattering (SLS) of the system during solubilization. Liposomes were formed by PC, to which phosphatidic acid (PA) or stearylamine (SA) was added when required to increase the negative or positive surface charge. The fact that at the two interaction levels investigated (100 and 0% of SLS of the surfactant/PC systems), the free surfactant concentration for each surfactant was always comparable to its critical micelle concentration (CMC) indicates that the liposome solubilization was mainly ruled by the formation of mixed micelles. The rise in the surfactant CMC (decrease in its alkyl chain length) led to an increase in the surfactant ability to saturate or solubilize liposomes and inversely in an abrupt decrease in its bilayer affinity, regardless of the electrical charge of liposomes. The overall balance of these opposite tendencies shows that the octyl glucoside showed the highest ability to saturate and solubilize liposomes (lowest Re values), whereas the dodecyl glucoside exhibited the highest degree of partitioning into liposomes or affinity with these bilayer structures (highest K values). The use of C 9-Glu reduced approximately 2.5 times the concentration needed to saturate and solubilize 1.0 mM PC liposomes with respect to that needed for C 8-Glu, regardless of the type of electrical charge present in bilayers.