Catanionic surfactants

Khan, Ali; Marques, Eduardo F.

doi:10.1007/978-94-009-1557-2_3

Cited by 71 publications

(73 citation statements)

References 142 publications

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“…41,42 This type of behavior is seen inter alia for the systems DDAB-SDS 37 and DDAB-AOT. 43 At low concentrations, with slight excess of one of the ionic amphiphiles, mixed micelles denoting growth (to rodlike or disklike micelles) and stable, spontaneous vesicles are often formed.…”

Section: Introductionmentioning

confidence: 69%

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Micelles, Dispersions, and Liquid Crystals in the Catanionic Mixture Bile Salt−Double-Chained Surfactant. The Bile Salt-Rich Area

et al. 2000

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The phase behavior and phase structure for the catanionic pair sodium taurodeoxycholate-didodecyldimethylammonium bromide (DDAB) are investigated, at 25°C. A combination of techniques is used including light and electron microscopy, small-angle X-ray scattering, and pulsed field gradient NMR self-diffusion. The bile salt micellar solution incorporates large amounts of the double-chained amphiphile, with the solution region extending to equimolarity. On the contrary, the hexagonal liquid-crystalline phase is destabilized by the addition of small amounts of DDAB. At equimolarity, coacervation instead of precipitation is observed, with formation of a viscous isotropic solution and a very dilute one. In the water-rich part of the phase diagram, a peculiar type of phase separation occurs, involving the formation of very fine bluish dispersions and a region of coexistence of two dispersions (double dispersion region). Microscopy and self-diffusion data for the solution region indicate limited growth of the mixed micelles. Large domains in which the micellar structure appears to be maintained are imaged in the bluish dispersions by electron microscopy. No other type of aggregate such as vesicles or precipitates is observed in the dilute bile salt-rich area of this mixture.

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Section: Introductionmentioning

confidence: 69%

“…42 This is not the case for the STDC-DDAB mixture, where the mixed aggregates at equimolarity retain the micellar structure. Moreover, vesicle formation, often detected in catanionic mixtures, is absent from the diluted bile salt-rich area of the system.…”

Section: Summary and Final Remarksmentioning

confidence: 99%

Micelles, Dispersions, and Liquid Crystals in the Catanionic Mixture Bile Salt−Double-Chained Surfactant. The Bile Salt-Rich Area

et al. 2000

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“…Appropriate heterogeneous regions were also experimentally found in both the SDS-rich and the DDAB-rich side, bearing in mind that since catanionic mixtures are in reality four-component systems, multiphase regions can only be approximately depicted in triangular phase diagrams. 3,41 In the cationic-rich side, an isotropic bluish turbid solution was found, consisting of a narrow lobe up to about 0.8 wt % DDAB ( Figure 2b). At higher surfactant concentration, the phase behavior is dominated by the DDAB-rich swollen lamellar phase and the catanionic crystals in appropriate two-and three-phase regions.…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3] At high surfactant concentration and above the Krafft boundary of the mixture, these systems show a variety of liquid crystalline phases, namely, lamellar and cubic phases, which are not present in the individual surfactant-water binary systems. [4][5][6] At low concentration, typically below 5 wt %, their behavior is dominated by phase separation, with the formation of highly insoluble precipitates (catanionic solid) at and around equimolarity.…”

Section: Introductionmentioning

confidence: 99%

“…Yet, it is the structural studies on these isotropic phases that have in recent years attracted considerable interest, mainly due to the fact that spontaneous formation of stable vesicles appears to be a general feature of these mixtures. 3,7 A vesicle is a colloidal object, usually spherical, which consists of a self-folded amphiphilic bilayer enclosing a volume of solvent secluded from the bulk. A vesicular solution always presents some degree of polydispersity, and the average vesicle diameter varies enormously between systems, from small unilamellar vesicles (10-50 nm) to large unilamellar (50-500 nm), giant unilamellar (more than 0.5 µm) and multilamellar vesicles (1-50 µm), also known as onions.…”

Section: Introductionmentioning

confidence: 99%

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Vesicle Formation and General Phase Behavior in the Catanionic Mixture SDS−DDAB−Water. The Anionic-Rich Side

et al. 1998

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Catanionic mixtures are aqueous mixtures of oppositely charged surfactants which display novel phase behavior and interfacial properties in comparison with those of the individual surfactants. One phase behavior property is the ability of these systems to spontaneously form stable vesicles at high dilution. The phase behavior of the mixture sodium dodecyl sulfate (SDS) -didodecyldimethylammonium bromide (DDAB) in water has been studied in detail, and two regions of isotropic vesicular phases (anionic-rich and cationic-rich) were identified. Cryo-transmission electron microscopy allowed direct visualization of relatively small and polydisperse unilamellar vesicles on the SDS-rich side. Monitoring of the microstructure evolution from mixed micelles to vesicles as the surfactant mixing ratio is varied toward equimolarity was also obtained. Further information was provided by water self-diffusion measurements by pulsed field gradient spin-echo NMR. Water molecules can be in fast or slow exchange between the inside and outside of the vesicle with respect to the experimental time scale, depending on membrane permeability and vesicle size. For the SDSrich vesicles, a slow-diffusing component of very low molar fraction observed for the echo decays was traced down to very large vesicles in solution. Light microscopy confirmed the presence of vesicles of several microns in diameter. Thus, polydispersity seems to be an inherent feature of the system.

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Divergent effects of cholesterol on the structure and fluidity of liposome and catanionic vesicle membranes

et al. 2022

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Lipid-like ion-pair amphiphile vesicles, or catanionic vesicles, have emerged as potential drug carriers. The effects of cholesterol on the properties of catanionic vesicles have yet been systematically studied. Here, we compared the effects of cholesterol on the structures and fluidities of dipalmitoylphosphatidylcholine liposomes and catanionic vesicles with similar main transition temperatures (T m ). For liposomes, fluorescence anisotropy (FA) thermograms reveal typical condensing and disordering effects of cholesterol above and below T m respectively. In contrast, FA and molecular simulation data reveal that catanionic bilayers below T m are more fluidic due to shorter alkyl chains. This leads to only condensing effects of cholesterol for catanionic vesicles at all temperatures. Our results provide important insights into the fabrication of catanionic vesicles as novel drug carriers.

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Catanionic surfactants

Cited by 71 publications

References 142 publications

Micelles, Dispersions, and Liquid Crystals in the Catanionic Mixture Bile Salt−Double-Chained Surfactant. The Bile Salt-Rich Area

Micelles, Dispersions, and Liquid Crystals in the Catanionic Mixture Bile Salt−Double-Chained Surfactant. The Bile Salt-Rich Area

Vesicle Formation and General Phase Behavior in the Catanionic Mixture SDS−DDAB−Water. The Anionic-Rich Side

Divergent effects of cholesterol on the structure and fluidity of liposome and catanionic vesicle membranes

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