Manipulationof the Gel Behavior of Biological SurfactantSodium Deoxycholate by Amino Acids.

Supramolecular hydrogels were preparedin the mixtures of biologicalsurfactant sodium deoxycholate (NaDC) and halide salts (NaCl and NaBr)in sodium phosphate buffer. It is very interesting that with the additionof two kinds of amino acids (l-lysine and l-arginine)to NaDC/NaX hydrogels, the gel becomes solution at room temperature.We characterized this performance through phase behavior observation,transmission electron microscopy, scanning electron microscopy, X-raypowder diffraction, Fourier transform infrared spectra, and rheologicalmeasurements. The results demonstrate that the gels are formed byintertwined fibrils, which are induced by enormous cycles of NaDCmolecules driven by comprehensive noncovalent interactions, especiallythe hydrogen bonds. Our conclusion is that the presence of halidesalts (NaCl and NaBr) enhances the formation of the gels, while theaddition of amino acids (l-lysine and l-arginine)could make the breakage of the hydrogen bonds and weaken the formationof the gels. Moreover, its fast disassembly in the presence of aminoacids allows for the release of substances (i.e., the dye methyleneblue) entrapped within the gel network. The tunable gel morphology,microstructure, mechanical strength, and anisotropy verify the roleof halide salts and amino acids in altering the properties of thegels, which can probably be exploited for a variety of applicationsin future. [ABSTRACT FROM AUTHOR]