Extended Light Scattering Investigations on Dihydroxy Bile Salt Micelles in Low-Salt Aqueous Solutions

Abstract

Extended static and dynamic light scattering results on micellar solutions of the dihydroxy bile salt NaGDC (sodium glycodeoxycholate) are presented. From the measurements the apparent molar mass and the mean aggregation number, the apparent diffusion coefficient and the mean hydrodynamic radius for the micelles as a function of NaGDC concentration (8.5-28.0 g/L), ionic strength of the solution (0.03-0.2 M NaCl added), and temperature (20-35 °C) are deduced. The apparent micellar size versus surfactant concentration is discussed only in the context of intermicellar interactions. Growth processes are not taken into account. A self-consistent calculation of the concentration dependence of the diffusion coefficient very similar to that of Dorshow et al. 1,2 is applied in order to determine the potential of the micelles using the DLVO theory. The fractional ionization of the micelle surface is estimated. Moreover, the expansion of the analysis from Dorshow et al. shows that Hamaker's constant is proportional to the mean molar mass of the micelles.

Membranolytic Activity of Bile Salts: Influence of Biological Membrane Properties and Composition

“…However, based on DLS no exact information with regards to the shape of the formed aggregates can be obtained. Therefore, SANS measurements were performed [82][83][84]. This is exemplarily described for the system NaDC/DPPC in 100 mM NaCl at 60 °C.…”

“…In order to compare the results with the ITC results, the same temperature ranges were investigated [64]. The data were evaluated as described previously [84].…”

Use of affinity capillary electrophoresis for characterizing pharmaceutical colloidal vehicle systems thermodynamically

“…With the experimental technique of static and dynamic light scattering it is possible to determine the aggregation number and the hydrodynamic radius of micelles [36]. Light scattering measurements and theoretical evaluations the partial specific volumes were derived as follows [37]:…”

“…To calculate the partition coefficient from the capacity factor according to Equation (5), the cmc of the micelle was calculated at different temperatures as described by Ishihama et al [5]. However, the aggregation number, the phase ratio between the micelle and aqueous phases, the hydrodynamic radius as well as the partial specific volumes of the drugs have changed with change of the temperature [36] (Table 1).…”

“…Previous investigations using microemulsion electrokinetic chromatography were carried out Table 1. Micellar parameters, aggregation number (n), hydrodynamic radius (R h ), phase ratio between the micelle and aqueous phases (Q), partial specific volumes (v) studied at different temperatures using dynamic light scattering [36,37] only with cetyl trimethylammonium chloride or sodium dodecyl sulfate [22,23]. These microemulsion systems have been used only as separation media [42,43].…”