Aggregated Assemblies of Sodium Dodecyl Sulfate/Dimethyldodecyl Ammoniopropane Sulfonate and Phospholipids at the Interface and in the Bulk

Solubilization of phospholipid vesicular structures into mixed micelles of zwitterionic surfactants

“…This paper is a continuation of previous work (7) and aims to explore surfactant-lipid interactions by selecting three different kinds of phospholipids (Scheme 1) having an identical phosphocholine group but different double fatty acid chains: (A, Scheme 1) L-α-phosphatidylcholine (PC), (B) 1,2didecanoyl-sn-glycero-3-phosphocholine (DPC), and (C) 1,2dipalmitoyl-sn-glycero-3-phosphocholine (PPC), which are expected to exist only in the form of bilayers (11,12) owing to the strong hydrophobic characters of their double fatty acid chains. Since lipid macromolecules are much larger than conventional surfactants such as dimethyltetradecylammoniopropanesulfonate TPS (D), the aggregation process of TPS has been studied in the presence of micromolar amounts of each lipid to effectively monitor and compare the surfactant aggregation with that in the absence of lipids.…”

“…However, the evolution of high K values in the present study shows that the degree of partitioning of surfactants into bilayers drastically increased as the surfactant alkyl chain length increased or its CMC decreased. This suggests that the affinity of surfactant molecules for lipid bilayers with respect to the aqueous medium increases as the surfactant alkyl chain length increases (7,25). The third break, which is always close to the CMC of TPS in pure water in the presence of different amounts of each lipid, can be ascribed to independent micelle formation.…”

“…Figure 1A shows the plots of CMC of a series of zwitterionic surfactants: dimethyldodecylammoniopropanesulfonate (DPS), TPS, and dimethylhexadecylammoniopropanesulfonate (HPS). The values of DPS and HPS have also been taken from our previous (7) and continuing work (Sehgal, P., H. Doe, and M.S. Bakshi, unpublished data), respectively.…”

“…A number of studies on the principles governing the interactions of surfactants have utilized a simplified membrane model with phospholipid bilayers. Lichtenberg (6) postulated that the effective surfactant-to-lipid ratio producing saturation and solubilization of vesicles depends on the surfactant CMC and on the bilayer/aqueous medium surfactant distribution coefficients K. In previous work (7), we explored lipid-surfactant interactions and concluded that zwitterionics have stronger interactions with lipids than anionic surfactants of similar hydrocarbon chain length but with different hydrophilicities. Johnsson and Edwards (8) studied the interactions between nonionic surfactants and sterically stabilized phosphatidylcholine (PC) liposomes by using cryogenic transmission electron microscopy and concluded that bilayer solubilization depends on the nature of the surfactant.…”

Effects of interactions on the formation of mixed micelles of 1,2-diheptanoyl-sn-glycero-3-phosphocholine with sodium dodecyl sulfate and dodecyltrimethylammonium bromide

“…In the human digestive tract, phospholipids form mixed micelles with bile salts and are hydrolyzed by the phospholipase enzymes [3][4][5]. Although several studies exist on the mixed micelle formation between conventional surfactants and long chain phospholipids upon a breakdown of the vesicular structures [6][7][8][9], little is known about direct mixed micelle formation between phospholipids and detergents. Hence, it is important to elucidate the nature of mixed micellization on the basis of different categories of the surfactants.…”