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

Abstract

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.

Supra-molecular Association and Polymorphic Behaviour In Systems Containing Bile Acid Salts

“…The system containing sodium taurodeoxycholate and a double chain surfactant, DDAB (didodecyldimethylammonium bromide) was also presented [110]. The latter system is especially interesting, since DDAB is used in mixture with lipids and imparts a positive charge to the resulting vesicles [111]. In that system a wide solution region extends from the BS-rich side up to the DDAB-rich one.…”

Effect of a bile salt on the aggregation behavior of a double-chained cationic surfactant - the cationic-rich dilute region of the didodecyldimethylammonium bromide-sodium taurodeoxycholate-water system

“…Vitrified samples were prepared, transferred and imaged according to the usual procedure, described in previous works [24,25,37]. A Philips CM120 Bio-Twin microscope was used, especially designed for handling cryogenic samples.…”

“…Both the phospholipid and DDAB are vesicle-and lamellarforming amphiphiles; however, the presence of the headgroup electrostatic interactions and salt (NaBr) in the catanionic system brings a new complexity to the phase equilibria and aggregation processes. Previously, the phase behavior and aggregation phenomena were studied for the same catanionic pair, in the bile salt rich area [37]. It was reported that the system displays coacervation instead of precipitation at equimolarity, consisting of a viscous isotropic solution in equilibrium with a very dilute solution.…”

Micellar crowding and branching in a versatile catanionic system

“…It becomes by far more extended in the case of DDAB-STDC-D 2 O [1]. Noteworthily, detailed rheological and NMR diffusivity measurements enlightened a dramatic microstructural change occurring at the equimolar line, from dis- crete to branched, interconnected micelles [4].…”

“…The association of the two surfactants didodecyldimethylammoniun bromide (DDAB) and sodium taurodeoxycholate (STDC), which differ under various respects beside charge, gives rise to a variety of intriguing self-assembly motifs, as revealed by Marques et al [1][2][3][4]. STDC is a bile salt (Fig.…”