Hydrogelation and Crystallization of Sodium Deoxycholate Controlled by Organic Acids

Abstract

The gelation and crystallization behavior of a biological surfactant, sodium deoxycholate (NaDC), mixed with l-taric acid (L-TA) in water is described in detail. With the variation of molar ratio of L-TA to NaDC (r = n(L-TA)/n(NaDC)) and total concentration of the mixtures, the transition from sol to gel was observed. SEM images showed that the density of nanofibers gradually increases over the sol-gel transition. The microstructures of the hydrogels are three-dimensional networks of densely packed nanofibers with lengths extending to several micrometers. One week after preparation, regular crystallized nanospheres formed along the length of the nanofibers, and it was typical among the transparent hydrogels induced by organic acids with pKa1 value <3.4. Small-angle X-ray diffraction demonstrated differences in the molecular packing between transparent and turbid gels, indicating a variable hydrogen bond mode between NaDC molecules.

Scrolling of Supramolecular Lamellae in the Hierarchical Self-Assembly of Fibrous Gels

“…A gel often consists of microcrystals with a high aspect ratio, 22 and even non-crystalline gels can form alongside a non-gelating crystalline phase or undergo crystallization with the passage of time. [23][24][25] Although the crystal structure of a gelator might offer some indication of how molecules interact in the gel phase, [26][27][28] the assumption of a structural relationship between the two materials is not always justified. 29,30 Nonetheless, it is likely that the dominant supramolecular motifs in crystals are preserved in the corresponding gels and play a central role in determining the materials' optical, microstructural, and rheological characteristics.…”

Wormlike reverse micelles in lecithin/bile salt/water mixtures in oil

“…Due to the steroid rigidity and the peculiar distribution of hydrophobic and hydrophilic domains, these molecules are particularly attractive for the bottom up construction of complex nanostructures. They often self-assemble in tubes or fibers and behave as low molecular weight gelators [15][16][17][18][19][20][21][22][23][24][25][26]. The tubes have cross section diameters spanning a wide range of values (3-450 nm) [9,19,[27][28][29][30][31][32][33][34] and sometimes they form through appealing pH [35,36] or temperature responsive aggregations [37].…”

Effects of polymers on the properties of hydrogels constructed using sodium deoxycholate and amino acid

“…indicate that the carboxyl and carboxylate species coexist as aggregates in solutions, 21 proving the existence of O-H/O hydrogen bonding between NaDC and deoxycholic acid or Asp molecules. For NaDC/Asp/polymer hydrogels (Fig.…”

“…19,20 Sodium deoxycholate (NaDC), as one of the most studied bile salt hydrogelators, is sensitive to pH and yields hydrogels at slightly alkaline pH. 21 However, the viscoelastic and mechanical properties of NaDC hydrogels are not strong enough. Thus, some additives are needed to construct composite hydrogels and improve their function.…”