Characterization of Hydrophobic and Polar Binding Environments in a Sodium Deoxycholate Hydrogel Using Fluorescence and Photochromism

The properties of guests bound to sodium deoxycholate (NaDC) gels was compared to the properties NaDC self-assemblies in solution to determine the extent of the similarities of these properties in the solution and gel phases. Bile salts, such as NaDC, form self-assemblies with two binding sites with different properties and guests that bind to the self-assemblies were chosen to determine these different properties. Pyrene and perylene were used as fluorescent probes that reside in the primary aggregates of NaDC self-assemblies, while the photochromism of 1′,3′,3′-trimethyl-6-nitrospiro[2H-1]-benzopyran-2,2′-indoline was used to probe the binding site in the larger secondary aggregates. The properties reported by all three guests showed that the properties for the two different binding sites were the same for NaDC self-assemblies in solution and in the gel. These results will be instrumental for the design of gel systems containing bile salts since the properties observed for guests in the self-assemblies in solution are directly transferable to the immobile phase of the gel.