Bile salts (BSs) are biological surfactants that have a rigid steroid skeleton, carrying hydroxyl group(s), and a charged head on the lateral chain. Due to their rigidity and their uncommon distribution of hydrophobic and hydrophilic regions BSs self assemble in peculiar supramolecular arrangements that are particularly ordered and not rationalized on the basis of the conventional geometric rules of surfactant packing. It has been shown that rigid surfactants with new amphiphilic structures and self-assembly properties can be synthesized starting from bile salts as substrates.[1-5] For example, surfactants showing thermo- or pH-responsive self assembling in tubular aggregates were prepared,[1,2] whereas mixtures of anionic and cationic forms of these derivatives were reported to form catanionic tubules with controlled stoichiometry.[3] Recently, new amino-acid or sugar-substituted derivatives have been also synthesized that form gels of extremely narrow hollow fibers [4] or monodisperse single walled tubules via scrolling of layers (Figure).[5] Self-associating molecules have shown a growing interest in the last decades for their employment in nanotechnology. The reported results demonstrate that bile acid derivatives could provide molecules with uncommon and versatile aggregation properties that could open up the possibilities for designing new nanostructured biomaterials.
Supramolecular structures of bile salt derivatives
[1] Galantini, L. et al. Soft Matter 2009, 5, 3018.
[2] Di Gregorio, M.C. et al. Phys. Chem. Chem. Phys. 2013,15, 7560.
[3] Manghisi, N. et al. Angew. Chem. Int. Ed. 2010, 49, 6604.
[4] Travaglini, L. et al. Chem. Commun. 2012, 48, 12011.
[5] Gubitosi, M et al. Langmuir submitted.
luciano.galantini@uniroma1.it
