Insights into the Interactions between Dendrimers and Bioactive Surfactants: 3. Size-Dependent and Hydrophobic Property-Dependent Encapsulation of Bile Salts

The supramolecular structures of dendrimer-bile salt complexes have been investigated by multidimensional and multinuclear NMR techniques, such as H-1 NMR, COSY, TOCSY, NOESY, and DOSY. 2D-NOESY analysis indicated the localization of bile salt in the interior pockets of dendrimers. The orientation of the guest in the pockets was predicted by the NOE cross-peaks based on NOESY spectrum. H-1 NMR experiments suggested that no electrostatic interactions between the amine groups of dendrimers and the negatively charged group of bile salts occur in the complexes. DOSY studies further confirmed the inclusion structures based on the diffusion coefficient information. The supramolecular structures of dendrimer-bile salt complexes were mainly formed by hydrophobic interactions/hydrogen-bond interactions in the interior pockets of dendrimers. In addition, size- and hydrophobic property-dependent encapsulation of bile salts and bile derivates in the cavities was observed. These results suggest a new interaction model of dendrimer-surfactant aggregates and provide new insight into the interactions between dendrimers and bioactive surfactants.